[65-libyang-models] Massive cleanup

11 files changed, 1007 insertions, 2419 deletions

diff --git a/src/lib/yang/models/ietf-dhcpv4-options.yang b/src/lib/yang/models/ietf-dhcpv4-options.yang
deleted file mode 100644
index 57a081c19d..0000000000
--- a/src/lib/yang/models/ietf-dhcpv4-options.yang
+++ /dev/null
@@ -1,243 +0,0 @@
-module ietf-dhcpv4-options {
-  yang-version 1.1;
-  namespace "urn:ietf:params:xml:ns:yang:ietf-dhcpv4-options";
-  prefix "dhcpv4-options";
-
-  import ietf-inet-types {
-    prefix inet;
-  }
-  import ietf-yang-types {
-    prefix yang;
-  }
-  import ietf-dhcpv4-types {
-    prefix dhcpv4-types;
-  }
-
-  organization "DHC WG";
-  contact
-    "piotr.strzyzewski@polsl.pl";
-  description "This model defines a YANG data model that can be
-    used to configure DHCPv4 options.";
-
-  revision 2018-07-14 {
-    description "Initial revision";
-    reference "";
-  }
-
-  /*
-   * Features
-   */
-
-  //  features for server options
-  feature router-op {
-    description "Support for Router Option";
-  }
-  feature time-server-op {
-    description "Support for Time Server Option";
-  }
-  feature domain-server-op {
-    description "Support for Domain Server Option";
-  }
-  feature log-server-op {
-    description "Support for Log Server Option";
-  }
-  feature hostname-op {
-    description "Support for Hostname Option";
-  }
-  feature domain-name-op {
-    description "Support for Domain Name Option";
-  }
-  feature broadcast-op {
-    description "Support for Broadcast Address Option";
-  }
-  feature ntp-server-op {
-    description "Support for NTP Servers Option";
-  }
-  feature server-name-op {
-    description "Support for Server-Name Option";
-  }
-  feature bootfile-name-op {
-    description "Support for Bootfile-Name Option";
-  }
-
-  /*
-   * Groupings
-   */
-
-  grouping server-option-definitions {
-    description "Contains definitions for options configured on the
-      DHCPv4 server which will be supplied to clients.";
-
-    container router-option {
-      // if-feature router-op
-      // presence "Enable this option";
-      description "Router (3) Router addresses";
-      reference "RFC2132: DHCP Options and BOOTP Vendor Extensions";
-      list router {
-        key router-id;
-        description "Router info";
-        leaf router-id {
-          type uint8;
-          mandatory true;
-          description "Router list entry ID";
-        }
-        leaf router-addr {
-          type inet:ipv4-address;
-          mandatory true;
-          description "Router address";
-        }
-      }
-    }
-    container time-server-option {
-      // if-feature time-server-op
-      // presence "Enable this option";
-      description "Time Server (4) Timeserver addresses";
-      reference "RFC2132: DHCP Options and BOOTP Vendor Extensions";
-      list time-server {
-        key time-server-id;
-        description "Time Server info";
-        leaf time-server-id {
-          type uint8;
-          mandatory true;
-          description "Time Server list entry ID";
-        }
-        leaf time-server-addr {
-          type inet:ipv4-address;
-          mandatory true;
-          description "Time Server address";
-        }
-      }
-    }
-    container domain-server-option {
-      // if-feature domain-server-op
-      // presence "Enable this option";
-      description "Domain Server (6) DNS Server addresses";
-      reference "RFC2132: DHCP Options and BOOTP Vendor Extensions";
-      list domain-server {
-        key domain-server-id;
-        description "DNS Server info";
-        leaf domain-server-id {
-          type uint8;
-          mandatory true;
-          description "DNS Server list entry ID";
-        }
-        leaf domain-server-addr {
-          type inet:ipv4-address;
-          mandatory true;
-          description "DNS Server address";
-        }
-      }
-    }
-    container log-server-option {
-      // if-feature log-server-op
-      // presence "Enable this option";
-      description "Log Server (7) Logging Server addresses";
-      reference "RFC2132: DHCP Options and BOOTP Vendor Extensions";
-      list log-server {
-        key log-server-id;
-        description "Logging Server info";
-        leaf log-server-id {
-          type uint8;
-          mandatory true;
-          description "Logging Server list entry ID";
-        }
-        leaf log-server-addr {
-          type inet:ipv4-address;
-          mandatory true;
-          description "Logging Server address";
-        }
-      }
-    }
-    container hostname-option {
-      // if-feature hostname-op;
-      // presence "Enable this option";
-      description "Hostname (12) Hostname string";
-      reference "RFC2132: DHCP Options and BOOTP Vendor Extensions";
-      leaf hostname {
-        type string;
-        description "Hostname";
-      }
-    }
-    container domain-name-option {
-      // if-feature domain-name-op;
-      // presence "Enable this option";
-      description "Domain Name (15) The DNS domain name of the client";
-      reference "RFC2132: DHCP Options and BOOTP Vendor Extensions";
-      leaf domain-name {
-        type string;
-        description "Domain Name";
-      }
-    }
-    container broadcast-option {
-      // if-feature broadcast-op
-      // presence "Enable this option";
-      description "Broadcast Address (28) Broadcast Address";
-      reference "RFC2132: DHCP Options and BOOTP Vendor Extensions";
-      leaf broadcast-addr {
-        type inet:ipv4-address;
-        description "Broadcast address";
-      }
-    }
-    container ntp-server-option {
-      // if-feature ntp-server-op
-      // presence "Enable this option";
-      description "NTP Servers (42) NTP Server addresses";
-      reference "RFC2132: DHCP Options and BOOTP Vendor Extensions";
-      list ntp-server {
-        key ntp-server-id;
-        description "NTP Server info";
-        leaf ntp-server-id {
-          type uint8;
-          mandatory true;
-          description "NTP Server list entry ID";
-        }
-        leaf ntp-server-addr {
-          type inet:ipv4-address;
-          mandatory true;
-          description "NTP Server address";
-        }
-      }
-    }
-    container server-name-option {
-      // if-feature server-name-op;
-      // presence "Enable this option";
-      description "Server-Name (66) TFTP Server Name";
-      reference "RFC2132: DHCP Options and BOOTP Vendor Extensions";
-      leaf server-name {
-        type string;
-        description "TFTP Server Name";
-      }
-    }
-    container bootfile-name-option {
-      // if-feature bootfile-name-op;
-      // presence "Enable this option";
-      description "Bootfile-Name (67) Boot File Name";
-      reference "RFC2132: DHCP Options and BOOTP Vendor Extensions";
-      leaf bootfile-name {
-        type string;
-        description "Boot File Name";
-      }
-    }
-    container domain-search-option {
-      // if-feature domain-search-op;
-      // presence "Enable this option";
-      description "Domain Search (119) DNS domain search list";
-      reference "RFC3397: Dynamic Host Configuration Protocol
-        (DHCP) Domain Search Option";
-      list domain-search {
-        key domain-search-id;
-        description "Domain Search info";
-        leaf domain-search-id {
-          type uint8;
-          mandatory true;
-          description "Domain Search entry ID";
-        }
-        leaf domain-search-entry {
-          type string;
-          mandatory true;
-          description "Domain Search list entry";
-        }
-      }
-    }
-  }
-}
diff --git a/src/lib/yang/models/ietf-dhcpv4-types.yang b/src/lib/yang/models/ietf-dhcpv4-types.yang
deleted file mode 100644
index 4b33d2a418..0000000000
--- a/src/lib/yang/models/ietf-dhcpv4-types.yang
+++ /dev/null
@@ -1,64 +0,0 @@
-module ietf-dhcpv4-types {
-  yang-version 1.1;
-  namespace "urn:ietf:params:xml:ns:yang:ietf-dhcpv4-types";
-  prefix "dhcpv4-types";
-
-  import ietf-inet-types {
-    prefix inet;
-  }
-  import ietf-yang-types {
-    prefix yang;
-  }
-
-  organization "DHC WG";
-  contact
-    "piotr.strzyzewski@polsl.pl";
-  description "This model defines a YANG data model that can be
-    used to define some commonly used DHCPv4 types";
-
-  revision 2018-07-14 {
-    description "Initial revision";
-    reference "";
-  }
-
-  /*
-  * Grouping
-  */
-  grouping vendor-infor {
-    description "Vendor information.";
-    container vendor-info {
-      description "";
-      leaf ent-num {
-        type uint32;
-        description "enterprise number";
-      }
-      leaf-list data {
-        type string;
-        description "specific vendor info";
-      }
-    }
-  }
-
-  grouping portset-para {
-    description "portset parameters";
-    container port-parameter {
-      description "port parameter";
-      leaf offset {
-        type uint8;
-        mandatory true;
-        description "offset in a port set";
-      }
-      leaf psid-len {
-        type uint8;
-        mandatory true;
-        description "length of a psid";
-      }
-      leaf psid {
-        type uint16;
-        mandatory true;
-        description "psid value";
-      }
-    }
-  }
-
-}
diff --git a/src/lib/yang/models/ietf-kea-dhcpv6.yang b/src/lib/yang/models/ietf-kea-dhcpv6.yang
deleted file mode 100644
index eb736cb10e..0000000000
--- a/src/lib/yang/models/ietf-kea-dhcpv6.yang
+++ /dev/null
@@ -1,315 +0,0 @@
-module ietf-kea-dhcpv6 {
-    namespace "urn:ietf:params:xml:ns:yang:ietf-kea-dhcpv6";
-    prefix "dhcpv6";
-
-    import ietf-inet-types { 
-        prefix inet; 
-        revision-date "2013-07-15"; 
-    }
-    import ietf-yang-types { 
-        prefix yang; 
-        revision-date "2013-07-15"; 
-    }
-
-    organization "ISC, DT, Sysrepo, Tsinghua";
-
-    contact "lh.sunlinh@gmail.com";
-
-    description "This model defines a YANG data model that can be 
-    used to configure and manage Kea DHCPv6 server.";
-
-    revision 2016-07-16 {
-        description "version00: the minimum mapping between Kea 
-        configuration and dhcpv6 YANG model.";
-
-        reference "sysrepo.org";
-
-    }
-
-/*
- * Typedef
- */
- 
-    typedef duidtype {
-        type union {
-            type uint16;
-            type string {
-                pattern '(([0-9a-fA-F]{2}){2,128})';    
-            }
-        }
-        description "the type defined for duid";
-    }
-
-/*
- * Data Nodes
- */
-
-    container server {
-        description "Kea dhcpv6 server configuration";
-        container serv-attributes {
-            description "gloabl attributes";
-            leaf name {
-                type string;
-                description "server's name";
-            }
-            leaf duid {
-                type duidtype;
-                description "DHCP Unique Identifer";
-            }
-            leaf enable {
-                type boolean;
-                description "whether to enable the server";
-            }
-            container lease-database {
-                leaf type {
-                    type string;
-                    description "defines database type. Supported
-                                values are: memfile, mysql, pgsql,
-                                cassandra";
-                }
-                description "Defines database connection";
-            }
-            container control-socket {
-                leaf socket-type {
-                     type string;
-                     /* @todo: change this to enum */
-                     description "Type of control socket used
-                     to send commands to Kea";
-                }
-                leaf socket-name {
-                     type string;
-                     description "Specifies location of the
-                     unix socket Kea uses to receive commands";
-                }
-                description "Defines control API socket";
-            }
-            container interfaces-config {
-                description "A leaf list to denote which one or 
-                more interfaces the server should listen on. The 
-                default value is to listen on all the interfaces. 
-                This node is also used to set a unicast address 
-                for the server to listen with a specific interface. 
-                For example, if people want the server to listen 
-                on a unicast address with a specific interface, he 
-                can use the format like 'eth1/2001:db8::1'.";
-                leaf-list interfaces {
-                    type string;
-                    description "the specific interfaces";
-                }
-            }
-            leaf description {
-                type string;
-                description "description of the server";
-            }
-            leaf stateless-service {
-                type boolean;
-                description "A boolean value specifies whether 
-                the server support client-server exchanges 
-                involving two messages defined in ([RFC3315]).";
-            }
-            leaf renew-timer {
-                type yang:timeticks;
-                description "renew time in seconds";
-            }
-            leaf rebind-timer {
-                type yang:timeticks;
-                description "rebind time in seconds";
-            }
-            leaf preferred-lifetime {
-                type yang:timeticks;
-                description "preferred lifetime IA in seconds";
-            }
-            leaf valid-lifetime {
-                type yang:timeticks;
-                description "valid liftime for IA";
-            }
-        }
-        container custom-options {
-            description "container for defining custom 
-            DHCPv6 options";
-            list custon-option{
-                key option-code;
-                description "container for defining custom 
-                DHCPv6 options";
-                leaf option-code {
-                    type uint16;
-                    description "option code for custom option";
-                }
-                leaf option-name {
-                    type string;
-                    description "option name for custom option";
-                }
-                leaf option-type {
-                    type string;
-                    description "option type for custom option";
-                }
-                
-            }
-        }
-        container option-sets {
-            description "option sets configruation";
-            list option-set {
-                key option-set-id;
-                description "a specific option set";
-                leaf option-set-id {
-                    type uint8; 
-                    description "identifier for specific option 
-                    set";   
-                }
-                leaf description{
-                    type string;
-                    description "description for the option set";
-                }
-                list standard-option {
-                    key option-code;
-                    description "standard format for DHCPv6 
-                    option";
-                    leaf option-code {
-                        type uint16;
-                        description "option code for standard option";
-                    }
-                    leaf option-name {
-                        type string;
-                        description "option name for standard option";
-                    }
-                    leaf option-value {
-                        type string;
-                        description "option data for standard option";
-                    }
-                    leaf csv-format {
-                        type boolean;
-                        description "whether csv-format is employed";
-                    }
-                }
-            }
-        }
-        container network-ranges {
-            description "gloabl level for DHCPv6 server";
-            leaf option-set-id {
-                type uint8;
-                description "selected option set for global level";
-            }
-            leaf rapid-commit {
-                type boolean;
-                description "whether rapid commit is enabled 
-                gloablly";
-            }
-            list subnet6 {
-                key subnet;
-                description "A subnet of DHCPv6 server";
-                leaf network-range-id {
-                    type uint8;
-                    description "subnet id";
-                }
-                leaf network-description {
-                    type string;
-                    description "description for the subnet";
-                }
-                leaf subnet {
-                    type inet:ipv6-prefix;
-                    description "the subnet prefix";
-                }
-                leaf option-set-id {
-                    type uint8;
-                    description "selected option set for this 
-                    subnet";
-                }
-                leaf rapid-commit {
-                    type boolean;
-                    description "whether rapid commit is enabled 
-                    for this subnet";
-                }
-                leaf interface {
-                    type string;
-                    description "IPv6 subnet selction";
-                }
-                leaf interface-id {
-                    type string;
-                    description "content of the interface-id 
-                    option used by relays";
-                }
-                leaf relay-address {
-                    type inet:ipv6-address;
-                    description "specify which relay will be 
-                    used";
-                }
-                container pools {
-                    description "address pools for this subnet";
-                    list address-pool {
-                        key pool-id;
-                        description "a specific address pool";
-                        leaf pool-id {
-                            type uint8;
-                            description "address pool 
-                            indentifier";
-                        }
-                        leaf pool-prefix {
-                            type inet:ipv6-prefix;
-                            description "the pool prefix";
-                        }
-                        leaf start-address {
-                            type inet:ipv6-address;
-                            description "start address";
-                        }
-                        leaf end-address {
-                            type inet:ipv6-address;
-                            description "end address";
-                        }
-                    }
-                }
-                container prefix-pools {
-                    description "prefix pools for this subnet";
-                    list prefix-pool {
-                        key pool-id;
-                        description "a specific prefix pool";
-                        leaf pool-id {
-                            type uint8;
-                            description "prefix pool 
-                            indentifier";
-                        }
-                        leaf pool-prefix {
-                            type inet:ipv6-prefix;
-                            description "available prefix";
-                        }
-                    }
-                }
-                list reserved-host {
-                    key cli-id;
-                    description "host reservation";
-                    leaf cli-id {
-                        type uint32;
-                        description "a cli-id is corresponding 
-                        to a specific host (DUID)";
-                    }
-                    leaf duid {
-                        type duidtype;
-                        description "host's DUID";
-                    }
-                    leaf hardware-addr {
-                        type yang:mac-address;
-                        description "host's mac address";
-                    }
-                    leaf-list reserv-addr {
-                        type inet:ipv6-address;
-                        description "reserved IPv6 addresses";
-                    }
-                }
-            }
-        }
-        container rsoo-enabled-options {
-            description "rsoo enabled options";
-            list rsoo-enabled-option{
-                key option-code;
-                description "rsoo enabled option";
-                leaf option-code {
-                    type uint16;
-                    description "option code";
-                }
-                leaf description {
-                    type string;
-                    description "description of the option";
-                }                    
-            }
-        }
-    }
-}
diff --git a/src/lib/yang/models/kea-control-agent.yang b/src/lib/yang/models/kea-control-agent.yang
index d2fcb06f62..b9c69aa3b0 100644
--- a/src/lib/yang/models/kea-control-agent.yang
+++ b/src/lib/yang/models/kea-control-agent.yang
@@ -12,11 +12,14 @@ module kea-control-agent {
   import kea-types {
     prefix kea;
   }
+  import kea-logging {
+    prefix logging;
+  }
 
   organization "Internet Systems Consortium";
   contact "kea-dev@lists.isc.org";
   description "This model defines a YANG data model that can be
-    used to configure and manage a Kea control agent.";
+               used to configure and manage a Kea control agent.";
 
   revision 2018-08-20 {
     description "Initial revision";
@@ -24,11 +27,12 @@ module kea-control-agent {
   }
 
   /*
-  * Groupings
+  * Data Nodes
   */
 
-  grouping configuration {
-    description "Contains parameters for control agent configuration.";
+  container config {
+    description "Contains control agent configuration.";
+    config true;
 
     leaf http-host {
       type inet:ip-address;
@@ -59,13 +63,20 @@ module kea-control-agent {
           uses kea:control-socket;
         }
       }
-   }
+    }
 
-   uses kea:hooks-libraries;
+    uses kea:hooks-libraries;
 
-   leaf user-context {
-     type kea:user-context;
-     description "Control agent user context.";
-   }
- }
+    leaf user-context {
+      type kea:user-context;
+      description "Control agent user context.";
+    }
+  }
+
+  container logging {
+    description "Logging";
+    config true;
+
+    uses logging:configuration;
+  }
 }
diff --git a/src/lib/yang/models/kea-dhcp-types.yang b/src/lib/yang/models/kea-dhcp-types.yang
new file mode 100644
index 0000000000..3adf1f6793
--- /dev/null
+++ b/src/lib/yang/models/kea-dhcp-types.yang
@@ -0,0 +1,734 @@
+module kea-dhcp-types {
+  yang-version 1.1;
+  namespace "urn:ietf:params:xml:ns:yang::kea-dhcp-types";
+  prefix "kea-dhcp-types";
+
+  import ietf-inet-types {
+    prefix inet;
+  }
+  import ietf-yang-types {
+    prefix yang;
+  }
+  import kea-types {
+    prefix kea;
+  }
+
+  organization "Internet Systems Consortium";
+  contact "kea-dev@lists.isc.org";
+  description "This file defines some commonly used Kea DHCP types and
+               groupings.";
+  revision 2018-08-20 {
+    description "Initial revision";
+    reference "";
+  }
+
+  /*
+  * Typedef
+  */
+  typedef host-reservation-mode {
+    type enumeration {
+      enum "disabled";
+      enum "out-of-pool";
+      enum "all";
+    }
+    description "Host reservation mode.";
+  }
+
+  typedef lease-state {
+    type enumeration {
+      enum "default";
+      enum "declined";
+      enum "expired-reclaimed";
+    }
+    description "Defines state of the lease.";
+  }
+
+  /*
+  * Grouping
+  */
+  grouping valid-lifetime {
+    leaf valid-lifetime {
+      type uint32;
+      units "seconds";
+      description "Valid lifetime.";
+    }
+  }
+
+  grouping renew-timer {
+    leaf renew-timer {
+      type uint32;
+      units "seconds";
+      description "Renew timer.";
+    }
+  }
+
+  grouping rebind-timer {
+    leaf rebind-timer {
+      type uint32;
+      units "seconds";
+      description "Rebind timer.";
+    }
+  }
+
+  grouping database {
+    leaf database-type {
+      type string;
+      mandatory true;
+      description "Database type (e.g. mysql).";
+    }
+    leaf user {
+      type string;
+      description "Database user name.";
+    }
+    leaf password {
+      type string;
+      description "Database user password.";
+    }
+    leaf host {
+      type string;
+      description "Database host.";
+    }
+    leaf name {
+      type string;
+      description "Database name.";
+    }
+    leaf persist {
+      type boolean;
+      default true;
+      description "Write lease to disk file. This parameter applies only to
+                   memfile backend.";
+    }
+    leaf port {
+      type uint16;
+      description "Database port.";
+    }
+    leaf lfc-interval {
+      type uint32;
+      units "seconds";
+      default 3600;
+      description "Interval between two lease file cleanups.";
+    }
+    leaf readonly {
+      type boolean;
+      default false;
+      description "If set to true, the database will be connected in
+                   read-only mode. This does not make sense for lease
+                   databases, only for host reservations and possibly
+                   for upcoming config backend.";
+    }
+    leaf connect-timeout {
+      type uint32;
+      units "milliseconds";
+      description "Database connection timeout.";
+    }
+    leaf contact-points {
+      type string;
+      description "Cassandra database contact points, a coma separated list of
+                   IP addresses.";
+    }
+    leaf keyspace {
+      type string;
+      description "Cassandra database keyspace (this is Cassandra's equivalent
+                   of a database name).";
+    }
+    leaf max-reconnect-tries {
+      type uint32;
+      default 0;
+      description "Maximum of recovery attempts before exit.";
+    }
+    leaf reconnect-wait-time {
+      type uint32;
+      default 0;
+      units "milliseconds";
+      description "Waiting delay between two recovery attempts.";
+    }
+    leaf request-timeout {
+      type uint32;
+      units "milliseconds";
+      description "Timeout waiting for a response.";
+    }
+    leaf tcp-keepalive {
+      type uint32;
+      units "seconds";
+      default 0;
+      description "TCP keepalive for the database connection.";
+    }
+    leaf tcp-nodelay {
+      type boolean;
+      default true;
+      description "TCP nodelay for the database connection.";
+    }
+    uses kea:user-context {
+      refine user-context {
+        description "Database user context. Arbitrary JSON data can be
+                     stored here.";
+      }
+    }
+  }
+
+  grouping databases {
+    container lease-database {
+      description "Lease database.";
+      uses database;
+    }
+    container hosts-databases {
+      description "Hosts databases.";
+      list hosts-database {
+        key database-type;
+	uses database;
+      }
+    }
+  }
+
+  grouping expired-leases-processing {
+    container expired-leases-processing {
+      description "Expired leases processing setup.";
+      leaf reclaim-timer-wait-time {
+        type uint32;
+        units "seconds";
+        default 10;
+        description "Interval between reclamation cycles.";
+      }
+      leaf flush-reclaimed-timer-wait-time {
+        type uint32;
+        units "seconds";
+        default 25;
+        description "Interval between reclaimed leases collection.";
+      }
+      leaf hold-reclaimed-time {
+        type uint32;
+        units "seconds";
+        default 3600;
+        description "Hold timer for re-assignment.";
+      }
+      leaf max-reclaim-leases {
+        type uint32;
+        default 100;
+        description "Maximum number of reclaimed leases per cycle.";
+      }
+      leaf max-reclaim-time {
+        type uint32;
+        units "milliseconds";
+        default 250;
+        description "Maximum duration of a reclamation cycle.";
+      }
+      leaf unwarned-reclaim-cycles {
+        type uint32;
+        default 5;
+        description "Maximum numbers of uncomplete cycles before warning.";
+      }
+    }
+  }
+
+  grouping control-socket {
+    container control-socket {
+      description "Control socket";
+      uses kea:control-socket;
+    }
+  }
+
+  grouping dhcp-ddns {
+    container dhcp-ddns {
+      description "DHCP-DDNS client setup.";
+      leaf enable-updates {
+        type boolean;
+        default false;
+        description "Enable DHCP-DDNS updates.";
+      }
+      leaf qualifying-suffix {
+        type string;
+        description "DHCP-DDNS qualifying suffix.";
+      }
+      leaf server-ip {
+        type inet:ip-address;
+        default "127.0.0.1";
+        description "DHCP-DDNS server IP address.";
+      }
+      leaf server-port {
+        type uint16;
+        default 53001;
+        description "DHCP-DDNS server port.";
+      }
+      leaf sender-ip {
+        type inet:ip-address;
+        description "DHCP-DDNS sender IP address.";
+      }
+      leaf sender-port {
+        type uint16;
+        description "DHCP-DDNS sender port.";
+      }
+      leaf max-queue-size {
+        type uint32;
+        default 1024;
+        description "Maximum DHCP-DDNS queue size.";
+      }
+      leaf ncr-protocol {
+        type enumeration {
+          enum "UDP";
+          enum "TCP";
+        }
+        default "UDP";
+        description "Protocol to use for DHCP-DDNS communication.
+                     Currently only UDP is supported.";
+      }
+      leaf ncr-format {
+        type enumeration {
+          enum "JSON";
+        }
+        default "JSON";
+        description "Packet format to use for DHCP-DDNS.";
+      }
+      leaf always-include-fqdn {
+        type boolean;
+        description "???";
+      }
+      leaf override-no-update {
+        type boolean;
+        default false;
+        description "Ignore client request and send update.";
+      }
+      leaf override-client-update {
+        type boolean;
+        default false;
+        description "Ignore client delegation.";
+      }
+      leaf replace-client-name {
+        type enumeration {
+          enum "when-present";
+          enum "never";
+          enum "always";
+          enum "when-not-present";
+        }
+        default "never";
+        description "Replace the name provided by the client.";
+      }
+      leaf generated-prefix {
+        type string;
+        default "myhost";
+        description "DHCP-DDNS generated prefix.";
+      }
+      leaf hostname-char-set {
+        type string;
+        description "A regex defining invalid characters. If detected, those
+                     will be replaced by hostname-char-replacement.";
+      }
+      leaf hostname-char-replacement {
+        type string;
+        description "Replacement for invalid charaters. See
+                     hostname-char-set.";
+      }
+      uses kea:user-context {
+        refine user-context {
+          description "DHCP-DDNS user context. Arbitrary JSON data can
+                       be stored here.";
+        }
+      }
+    }
+  }
+
+  grouping sanity-checks {
+    container sanity-checks {
+      description "Sanity checks.";
+      leaf lease-checks {
+        type enumeration {
+          enum "none" {
+            description "No checks.";
+          }
+          enum "warn" {
+            description "When a check fails print a warning and accept the
+                         lease.";
+          }
+          enum "fix" {
+            description "When a check fails try to fix it and accept the
+                         lease.";
+          }
+          enum "fix-del" {
+            description "When a check fails try to fix it and reject the
+                         lease if still bad.";
+          }
+          enum "del" {
+            description "When a check fails reject the lease.";
+          }
+        }
+        default "warn";
+        description "Lease checks: verify subnet-id consistency on memfile
+                     loading.";
+      }
+    }
+  }
+
+  grouping client-class {
+    leaf client-class {
+      type string;
+    }
+  }
+
+  grouping pool-client-class {
+    uses client-class {
+      refine client-class {
+        description "Pool client class guard (only clients belonging
+                     to this class will be allowed in this pool).";
+      }
+    }
+  }
+
+  grouping subnet-client-class {
+    uses client-class {
+      refine client-class {
+        description "Subnet client class guard (only clients belonging to this
+                     class will be allowed in this subnet).";
+      }
+    }
+  }
+
+  grouping network-client-class {
+    uses client-class {
+      refine client-class {
+        description "Shared network client class guard (only clients
+                     belonging to this class will be allowed in this
+                     shared network).";
+      }
+    }
+  }
+
+  grouping require-client-classes {
+    leaf-list require-client-classes {
+      type string;
+    }
+  }
+
+  grouping pool-require-client-classes {
+    uses require-client-classes {
+      refine require-client-classes {
+        description "Pool require client classes.";
+      }
+    }
+  }
+
+  grouping subnet-require-client-classes {
+    uses require-client-classes {
+      refine require-client-classes {
+        description "Subnet require client classes.";
+      }
+    }
+  }
+
+  grouping network-require-client-classes {
+    uses require-client-classes {
+      refine require-client-classes {
+        description "Shared network require client classes.";
+      }
+    }
+  }
+
+  grouping interface {
+    leaf interface {
+      type string;
+    }
+  }
+
+  grouping subnet-interface {
+    uses interface {
+      refine interface {
+        description "Name of the network interface this subnet is directly
+                     accessible with (optional).";
+      }
+    }
+  }
+
+  grouping network-interface {
+    uses interface {
+      refine interface {
+        description "Specifies the network interface this shared network is
+                     directly accessible with. (optional)";
+      }
+    }
+  }
+
+  grouping interface-id {
+    leaf interface-id {
+      type string;
+    }
+  }
+
+  grouping subnet-interface-id {
+    uses interface-id {
+      refine interface-id {
+        description "Subnet interface-id option.";
+      }
+    }
+  }
+
+  grouping network-interface-id {
+    uses interface-id {
+      refine interface-id {
+        description "Shared network interface-id option.";
+      }
+    }
+  }
+
+  grouping subnet-id {
+    leaf id {
+      type uint32 {
+        range 1..max;
+      }
+      mandatory true;
+      description "Subnet ID, a unique identifier used to locate or reference
+                   a subnet.";
+    }
+  }
+
+  grouping host-identifier {
+    leaf identifier {
+      type string;
+      description "Host identifier.";
+    }
+  }
+
+  grouping host-hostname {
+    leaf hostname {
+      type string;
+      description "Host DNS name.";
+    }
+  }
+
+  grouping host-client-classes {
+    leaf-list client-classes {
+      type string;
+      description "Host client classes (if host identifier matches, a
+                   client's packet will be added to the classes liste
+                   here.)";
+    }
+  }
+
+  grouping host-subnet-id {
+    leaf subnet-id {
+      type uint32;
+      mandatory true;
+      description "Host subnet ID.";
+    }
+  }
+
+  grouping reservation-mode {
+    leaf reservation-mode {
+      type host-reservation-mode;
+    }
+  }
+
+  grouping subnet-reservation-mode {
+    uses reservation-mode {
+      refine reservation-mode {
+        description "Subnet host reservation mode.";
+      }
+    }
+  }
+
+  grouping network-reservation-mode {
+    uses reservation-mode {
+      refine reservation-mode {
+        description "Shared network host reservation mode.";
+      }
+    }
+  }
+
+  grouping interfaces-re-detect {
+    leaf re-detect {
+      type boolean;
+      default false;
+      description "Re-detect interfaces at each reconfiguration.";
+    }
+  }
+
+  grouping class-name {
+    leaf name {
+      type string;
+      mandatory true;
+      description "Name of the client class.";
+    }
+  }
+
+  grouping class-test {
+    leaf test {
+      type string;
+      description "Defines an expression that evaluates every incoming
+                   packet.";
+    }
+  }
+
+  grouping class-only-if-required {
+    leaf only-if-required {
+      type boolean;
+      default false;
+      description "Client class only if required flag.";
+    }
+  }
+
+  grouping option-def-name {
+    leaf name {
+      type string;
+      mandatory true;
+      description "Name of the new option being defined.";
+    }
+  }
+
+  grouping option-def-type {
+    leaf type {
+      type string;
+      mandatory true;
+      description "Type of the new option being defined (such as
+                   string, record or uint8).";
+    }
+  }
+
+  grouping option-def-record-types {
+    leaf record-types {
+      type string;
+      description "Option definition record types.";
+    }
+  }
+
+  grouping option-def-encapsulate {
+    leaf encapsulate {
+      type string;
+      description "Defines option space this new option encapsulates.
+                   Usually empty.";
+    }
+  }
+
+  grouping option-data-name {
+    leaf name {
+      type string;
+      description "Option name.";
+    }
+  }
+
+  grouping option-data-data {
+    leaf data {
+      type string;
+      description "Option data.";
+    }
+  }
+
+  grouping option-data-csv-format {
+    leaf csv-format {
+      type boolean;
+      default true;
+      description "If true, the option is specified as comma separated
+                   values.  If false, it is expected as a hex string.";
+    }
+  }
+
+  grouping option-data-always-send {
+    leaf always-send {
+      type boolean;
+      default false;
+      description "Defines whether to always send the option,
+                   regardless if the client requested it or not.";
+    }
+  }
+
+  grouping option-def-array {
+    leaf array {
+      type boolean;
+      default false;
+      description "Option definition array flag.";
+    }
+  }
+
+  grouping decline-probation-period {
+    leaf decline-probation-period {
+      type uint32;
+      units "seconds";
+      default 86400;
+      description "Decline probabation period.";
+    }
+  }
+
+  grouping network-name {
+    leaf name {
+      type string;
+      mandatory true;
+      description "Shared network name.";
+    }
+  }
+
+  grouping dhcp4o6-port {
+    leaf dhcp4o6-port {
+      type uint16;
+      description "DHCPv4-over-DHCPv6 interserver port.";
+    }
+  }
+
+  grouping pool-user-context {
+    uses kea:user-context {
+      refine user-context {
+        description "Pool user context. Arbitrary JSON data can be
+                     stored here.";
+      }
+    }
+  }   
+
+  grouping host-user-context {
+    uses kea:user-context {
+      refine user-context {
+        description "Host user context. Arbitrary JSON data can be
+                     stored here.";
+      }
+    }
+  }
+
+  grouping subnet-user-context {
+    uses kea:user-context {
+      refine user-context {
+        description "Subnet user context. Arbitrary JSON data can be
+                     stored here.";
+      }
+    }
+  }   
+
+  grouping network-user-context {
+    uses kea:user-context {
+      refine user-context {
+        description "Shared network user context. Arbitrary JSON data can be
+                     stored here.";
+      }
+    }
+  }
+
+  grouping interfaces-user-context {
+    uses kea:user-context {
+      refine user-context {
+        description "Interfaces user context. Arbitrary JSON data can
+                     be stored here.";
+      }
+    }
+  }
+
+  grouping class-user-context {
+    uses kea:user-context {
+      refine user-context {
+        description "Client class user context. Arbitrary JSON data can
+                     be stored here.";
+      }
+    }
+  }
+
+  grouping option-def-user-context {
+    uses kea:user-context {
+      refine user-context {
+        description "Option definition user context. Arbitrary JSON data
+	             can be stored here.";
+      }
+    }
+  }
+
+  grouping option-data-user-context {
+    uses kea:user-context {
+      refine user-context {
+        description "Option user context. Arbitrary JSON data can be
+                     stored here.";
+      }
+    }
+  }
+
+}
diff --git a/src/lib/yang/models/kea-dhcp4.yang b/src/lib/yang/models/kea-dhcp4.yang
index 0345bd5143..6f62e6362e 100644
--- a/src/lib/yang/models/kea-dhcp4.yang
+++ b/src/lib/yang/models/kea-dhcp4.yang
@@ -12,11 +12,17 @@ module kea-dhcp4 {
   import kea-types {
     prefix kea;
   }
+  import kea-dhcp-types {
+    prefix dhcp;
+  }
+  import kea-logging {
+    prefix logging;
+  }
 
   organization "Internet Systems Consortium";
   contact "kea-dev@lists.isc.org";
   description "This model defines a YANG data model that can be
-    used to configure and manage a Kea DHCPv4 server.";
+               used to configure and manage a Kea DHCPv4 server.";
 
   revision 2018-08-20 {
     description "Initial revision";
@@ -37,52 +43,9 @@ module kea-dhcp4 {
     description "Host identifier type.";
   }
 
-  typedef host-reservation-mode {
-    type enumeration {
-      enum "disabled";
-      enum "out-of-pool";
-      enum "all";
-      enum "global";
-    }
-    description "Host reservation mode.";
-  }
-
-  typedef lease-state {
-    type enumeration {
-      enum "default";
-      enum "declined";
-      enum "expired-reclaimed";
-    }
-    description "Defines state of the lease.";
-  }
-
   /*
   * Groupings
   */
-  grouping valid-lifetime {
-    leaf valid-lifetime {
-      type uint32;
-      units "seconds";
-      description "Valid lifetime.";
-    }
-  }
-
-  grouping renew-timer {
-    leaf renew-timer {
-      type uint32;
-      units "seconds";
-      description "Renew timer.";
-    }
-  }
-
-  grouping rebind-timer {
-    leaf rebind-timer {
-      type uint32;
-      units "seconds";
-      description "Rebind timer.";
-    }
-  }
-
   grouping match-client-id {
     leaf match-client-id {
       type boolean;
@@ -126,13 +89,14 @@ module kea-dhcp4 {
     list subnet4 {
       key id;
       ordered-by user;
-      uses valid-lifetime;
-      uses renew-timer;
-      uses rebind-timer;
+      uses dhcp:valid-lifetime;
+      uses dhcp:renew-timer;
+      uses dhcp:rebind-timer;
       uses option-data-list;
       container pools {
         list pool {
           key "start-address end-address";
+          ordered-by user;
           leaf prefix {
             type inet:ipv4-prefix;
             description "Defines a pool of dynamic IPv4 addresses to be managed
@@ -149,19 +113,9 @@ module kea-dhcp4 {
             description "Last IPv4 address in a pool.";
           }
           uses option-data-list;
-          leaf client-class {
-            type string;
-            description "Pool client class guard (only clients belonging to this
-                         class will be allowed in this pool).";
-          }
-          leaf-list require-client-classes {
-            type string;
-            description "Pool require client classes.";
-          }
-          leaf user-context {
-            type kea:user-context;
-            description "Pool user context. Arbitrary JSON data can be stored here.";
-          }
+          uses dhcp:pool-client-class;
+          uses dhcp:pool-require-client-classes;
+          uses dhcp:pool-user-context;
         }
       }
       leaf subnet {
@@ -169,72 +123,35 @@ module kea-dhcp4 {
         mandatory true;
         description "IPv4 subnet prefix.";
       }
-      leaf interface {
-        type string;
-        description "Name of the network interface this subnet is directly
-                     accessible with (optional).";
-      }
-      leaf interface-id {
-        type string;
-        description "Subnet interface-id option.";
-      }
-      leaf id {
-        type uint32 {
-          range 1..max;
-        }
-        mandatory true;
-        description "Subnet ID, a unique identifier used to locate or reference
-                     a subnet.";
-      }
-      leaf client-class {
-        type string;
-        description "Subnet client class guard (only clients belonging to this
-                     clas will be allowed in this subnet).";
-
-      }
-      leaf-list require-client-classes {
-        type string;
-        description "Subnet require client classes.";
-      }
+      uses dhcp:subnet-interface;
+      uses dhcp:subnet-interface-id;
+      uses dhcp:subnet-id;
+      uses dhcp:subnet-client-class;
+      uses dhcp:subnet-require-client-classes;
       container reservations {
-        description "A container with host reservations specific to this IPv4 subnet.";
+        description "A container with host reservations specific to
+                     this IPv4 subnet.";
         list host {
           key "identifier-type identifier";
           leaf identifier-type {
             type host-identifier-type;
             description "Host identifier type.";
           }
-          leaf identifier {
-            type string;
-            description "Host identifier.";
-          }
-          leaf-list client-classes {
-            type string;
-            description "Host client classes (if host identifier matches, a client's
-                         packet will be added to the classes liste here.)";
-          }
+          uses dhcp:host-identifier;
           leaf ip-address {
             type inet:ipv4-address;
             description "Host reserved IPv4 address.";
           }
-          leaf hostname {
-            type string;
-            description "Host DNS name.";
-          }
+          uses dhcp:host-hostname;
+          uses dhcp:host-client-classes;
           uses option-data-list;
           uses next-server;
           uses server-hostname;
           uses boot-file-name;
-          leaf user-context {
-            type kea:user-context;
-            description "Host user context. Arbitrary JSON data can be stored here.";
-          }
+          uses dhcp:host-user-context;
         }
       }
-      leaf reservation-mode {
-        type host-reservation-mode;
-        description "Subnet host reservation mode.";
-      }
+      uses dhcp:subnet-reservation-mode;
       container relay {
         description "Optional information about relay agent.";
         uses relay;
@@ -255,130 +172,20 @@ module kea-dhcp4 {
         type inet:ipv6-prefix;
         description "Subnet DHCPv4-over-DHCPv6 IPv6 prefix.";
       }
-      leaf user-context {
-        type kea:user-context;
-        description "Subnet user context. Arbitrary JSON data can be stored here.";
-      }
-    }
-  }
-
-  grouping database {
-    leaf database-type {
-      type string;
-      mandatory true;
-      description "Database type (e.g. mysql).";
-    }
-    leaf user {
-      type string;
-      description "Database user name.";
-    }
-    leaf password {
-      type string;
-      description "Database user password.";
-    }
-    leaf host {
-      type string;
-      description "Database host.";
-    }
-    leaf name {
-      type string;
-      description "Database name.";
-    }
-    leaf persist {
-      type boolean;
-      default true;
-      description "Write lease to disk file. This parameter applies only to
-                  memfile backend.";
-    }
-    leaf port {
-      type uint16;
-      description "Database port.";
-    }
-    leaf lfc-interval {
-      type uint32;
-      units "seconds";
-      default 3600;
-      description "Interval between two lease file cleanups.";
-    }
-    leaf readonly {
-      type boolean;
-      default false;
-      description "If set to true, the database will be connected in read-only
-                   mode. This does not make sense for lease databases, only for
-                   host reservations and possibly for upcoming config backend.";
-    }
-    leaf connect-timeout {
-      type uint32;
-      units "milliseconds";
-      description "Database connection timeout.";
-    }
-    leaf contact-points {
-      type string;
-      description "Cassandra database contact points, a coma separated list of
-                  IPv4 addresses.";
-    }
-    leaf keyspace {
-      type string;
-      description "Cassandra database keyspace (this is Cassandra's equivalent
-                   of a database name).";
-    }
-    leaf max-reconnect-tries {
-      type uint32;
-      default 0;
-      description "Maximum of recovery attempts before exit.";
-    }
-    leaf reconnect-wait-time {
-      type uint32;
-      default 0;
-      units "milliseconds";
-      description "Waiting delay between two recovery attempts.";
-    }
-    leaf request-timeout {
-      type uint32;
-      units "milliseconds";
-      description "Timeout waiting for a response.";
-    }
-    leaf tcp-keepalive {
-      type uint32;
-      units "seconds";
-      default 0;
-      description "TCP keepalive for the database connection.";
-    }
-    leaf tcp-nodelay {
-      type boolean;
-      default true;
-      description "TCP nodelay for the database connection.";
-    }
-    leaf user-context {
-      type kea:user-context;
-      description "Database user context. Arbitrary JSON data can be stored here.";
+      uses dhcp:subnet-user-context;
     }
   }
 
   grouping client-class {
-    leaf name {
-      type string;
-      mandatory true;
-      description "Name of the client class.";
-    }
-    leaf test {
-      type string;
-      description "Defines an expression that evaluates every incoming packet.";
-    }
-    leaf only-if-required {
-      type boolean;
-      default false;
-      description "Client class only if required flag.";
-    }
+    uses dhcp:class-name;
+    uses dhcp:class-test;
+    uses dhcp:class-only-if-required;
     uses option-def-list;
     uses option-data-list;
     uses next-server;
     uses server-hostname;
     uses boot-file-name;
-    leaf user-context {
-      type kea:user-context;
-      description "Client class user context. Arbitrary JSON data can be stored here.";
-    }
+    uses dhcp:class-user-context;
   }
 
   grouping option-def-list {
@@ -386,44 +193,22 @@ module kea-dhcp4 {
       description "List with custom option definitions.";
       list option-def {
         key "code space";
-        leaf name {
-          type string;
-          mandatory true;
-          description "Name of the new option being defined.";
-        }
         leaf code {
           type uint8;
           mandatory true;
           description "Option code to be used by the new option definition.";
         }
-        leaf type {
-          type string;
-          mandatory true;
-          description "Type of the new option being defined (such as string or uint8).";
-        }
-        leaf record-types {
-          type string;
-          description "Option definition record types.";
-        }
         leaf space {
           type string;
           mandatory true;
           description "Option space for the new option (typically dhcp4).";
         }
-        leaf encapsulate {
-          type string;
-          description "Defines option space this new option encapsulates.
-                       Usually empty.";
-        }
-        leaf array {
-          type boolean;
-          default false;
-          description "Option definition array flag.";
-        }
-        leaf user-context {
-          type kea:user-context;
-          description "Option definition user context.";
-        }
+        uses dhcp:option-def-name;
+        uses dhcp:option-def-type;
+        uses dhcp:option-def-record-types;
+        uses dhcp:option-def-encapsulate;
+        uses dhcp:option-def-array;
+        uses dhcp:option-def-user-context;
       }
     }
   }
@@ -433,14 +218,6 @@ module kea-dhcp4 {
       description "Option data list.";
       list option-data {
         key "code space";
-        leaf name {
-          type string;
-          description "Option name.";
-        }
-        leaf data {
-          type string;
-          description "Option data.";
-        }
         leaf code {
           type uint8;
           mandatory true;
@@ -451,39 +228,27 @@ module kea-dhcp4 {
           mandatory true;
           description "Option space.";
         }
-        leaf csv-format {
-          type boolean;
-          default true;
-          description "If true, the option is specified as comma separated values.
-                       If false, it is expected as a hex string.";
-        }
-        leaf always-send {
-          type boolean;
-          default false;
-          description "Defines whether to always send the option, regardless if the
-                       client requested it or not.";
-        }
-        leaf user-context {
-          type kea:user-context;
-          description "Option user context. Arbitrary JSON data can be stored here.";
-        }
+        uses dhcp:option-data-name;
+        uses dhcp:option-data-data;
+        uses dhcp:option-data-csv-format;
+        uses dhcp:option-data-always-send;
+        uses dhcp:option-data-user-context;
       }
     }
   }
 
-  grouping configuration {
-    description "Contains parameters for DHCPv4 server configuration.";
+  /*
+  * Data Nodes
+  */
 
-    uses valid-lifetime;
-    uses renew-timer;
-    uses rebind-timer;
+  container config {
+    description "Contains DHCPv4 server configuration.";
+    config true;
 
-    leaf decline-probation-period {
-      type uint32;
-      units "seconds";
-      default 86400;
-      description "Decline probabation period.";
-    }
+    uses dhcp:valid-lifetime;
+    uses dhcp:renew-timer;
+    uses dhcp:rebind-timer;
+    uses dhcp:decline-probation-period;
 
     container subnet4 {
       description "Global list of IPv4 subnets.";
@@ -494,22 +259,15 @@ module kea-dhcp4 {
       description "Defines a list of IPv4 shared networks.";
       list shared-network {
         key name;
-        leaf name {
-          type string;
-          mandatory true;
-          description "Shared network name.";
-        }
+        uses dhcp:network-name;
         container subnet4 {
-          description "List of IPv4 subnets that belong to this shared network.";
+          description "List of IPv4 subnets that belong to this shared
+                       network.";
           uses subnet4-list;
         }
-        leaf interface {
-          type string;
-          description "Specifies the network interface this shared network is
-                       directly accessible with. (optional)";
-        }
-        uses renew-timer;
-        uses rebind-timer;
+        uses dhcp:network-interface;
+        uses dhcp:renew-timer;
+        uses dhcp:rebind-timer;
         uses option-data-list;
         uses match-client-id;
         uses next-server;
@@ -519,25 +277,11 @@ module kea-dhcp4 {
           description "Optional information about relay agent.";
           uses relay;
         }
-        leaf reservation-mode {
-          type host-reservation-mode;
-          description "Shared network host reservation mode.";
-        }
-        leaf client-class {
-          type string;
-          description "Shared network client class guard (only clients belonging
-                       to this class will be allowed in this shared network).";
-        }
-        leaf-list require-client-classes {
-          type string;
-          description "Shared network require client classes.";
-        }
-        uses valid-lifetime;
-        leaf user-context {
-          type kea:user-context;
-          description "Shared network user context. Arbitrary JSON data can be
-                       stored here.";
-        }
+        uses dhcp:network-reservation-mode;
+        uses dhcp:network-client-class;
+        uses dhcp:network-require-client-classes;
+        uses dhcp:valid-lifetime;
+        uses dhcp:network-user-context;
       }
     }
 
@@ -564,7 +308,7 @@ module kea-dhcp4 {
         type enumeration {
           enum "same-as-inbound" {
             description "Send the response on the interface where the query
-              was received.";
+                         was received.";
           }
           enum "use-routing" {
             description "Use kernel routing.";
@@ -573,31 +317,11 @@ module kea-dhcp4 {
         default "same-as-inbound";
         description "Control the interface used to send a response.";
       }
-      leaf re-detect {
-        type boolean;
-        default false;
-        description "Re-detect interfaces at each reconfiguration.";
-      }
-      leaf user-context {
-        type kea:user-context;
-        description "Interfaces user context. Arbitrary JSON data can be stored
-                     here.";
-      }
+      uses dhcp:interfaces-re-detect;
+      uses dhcp:interfaces-user-context;
     }
 
-    container lease-database {
-      description "Lease database.";
-      presence "Enable lease database.";
-      uses database;
-    }
-
-    container hosts-databases {
-      description "Hosts databases.";
-      list hosts-database {
-        key database-type;
-        uses database;
-      }
-    }
+    uses dhcp:databases;
 
     leaf-list host-reservation-identifiers {
       type host-identifier-type;
@@ -616,202 +340,45 @@ module kea-dhcp4 {
     uses option-def-list;
     uses option-data-list;
     uses kea:hooks-libraries;
-
-    container expired-leases-processing {
-      description "Expired leases processing setup.";
-      leaf reclaim-timer-wait-time {
-        type uint32;
-        units "seconds";
-        default 10;
-        description "Interval between reclamation cycles.";
-      }
-      leaf flush-reclaimed-timer-wait-time {
-        type uint32;
-        units "seconds";
-        default 25;
-        description "Interval between reclaimed leases collection.";
-      }
-      leaf hold-reclaimed-time {
-        type uint32;
-        units "seconds";
-        default 3600;
-        description "Hold timer for re-assignment.";
-      }
-      leaf max-reclaim-leases {
-        type uint32;
-        default 100;
-        description "Maximum number of reclaimed leases per cycle.";
-      }
-      leaf max-reclaim-time {
-        type uint32;
-        units "milliseconds";
-        default 250;
-        description "Maximum duration of a reclamation cycle.";
-      }
-      leaf unwarned-reclaim-cycles {
-        type uint32;
-        default 5;
-        description "Maximum numbers of uncomplete cycles before warning.";
-      }
-    }
-
-    leaf dhcp4o6-port {
-      type uint16;
-      description "DHCPv4-over-DHCPv6 interserver port.";
-    }
-
-    container control-socket {
-      description "Control socket";
-      presence "Enable control socket.";
-      uses kea:control-socket;
-    }
-
-    container dhcp-ddns {
-      description "DHCP-DDNS client setup.";
-      leaf enable-updates {
-        type boolean;
-        default false;
-        description "Enable DHCP-DDNS updates.";
-      }
-      leaf qualifying-suffix {
-        type string;
-        description "DHCP-DDNS qualifying suffix.";
-      }
-      leaf server-ip {
-        type inet:ip-address;
-        default "127.0.0.1";
-        description "DHCP-DDNS server IP address.";
-      }
-      leaf server-port {
-        type uint16;
-        default 53001;
-        description "DHCP-DDNS server port.";
-      }
-      leaf sender-ip {
-        type inet:ip-address;
-        description "DHCP-DDNS sender IP address.";
-      }
-      leaf sender-port {
-        type uint16;
-        description "DHCP-DDNS sender port.";
-      }
-      leaf max-queue-size {
-        type uint32;
-        default 1024;
-        description "Maximum DHCP-DDNS queue size.";
-      }
-      leaf ncr-protocol {
-        type enumeration {
-          enum "UDP";
-          enum "TCP";
-        }
-        default "UDP";
-        description "Protocol to use for DHCP-DDNS communication.
-                     Currently only UDP is supported.";
-      }
-      leaf ncr-format {
-        type enumeration {
-          enum "JSON";
-        }
-        default "JSON";
-        description "Packet format to use for DHCP-DDNS.";
-      }
-      leaf always-include-fqdn {
-        type boolean;
-        description "???";
-      }
-      leaf override-no-update {
-        type boolean;
-        default false;
-        description "Ignore client request and send update.";
-      }
-      leaf override-client-update {
-        type boolean;
-        default false;
-        description "Ignore client delegation.";
-      }
-      leaf replace-client-name {
-        type enumeration {
-          enum "when-present";
-          enum "never";
-          enum "always";
-          enum "when-not-present";
-        }
-        default "never";
-        description "Replace the name provided by the client.";
-      }
-      leaf generated-prefix {
-        type string;
-        default "myhost";
-        description "DHCP-DDNS generated prefix.";
-      }
-      leaf hostname-char-set {
-        type string;
-        description "A regex defining invalid characters. If detected, those
-                     will be replaced by hostname-char-replacement.";
-      }
-      leaf hostname-char-replacement {
-        type string;
-        description "Replacement for invalid charaters. See hostname-char-set.";
-      }
-      leaf user-context {
-        type kea:user-context;
-        description "DHCP-DDNS user context. Arbitrary JSON data can be stored here.";
-      }
-    }
+    uses dhcp:expired-leases-processing;
+    uses dhcp:dhcp4o6-port;
+    uses dhcp:control-socket;
+    uses dhcp:dhcp-ddns;
 
     leaf echo-client-id {
       type boolean;
       default true;
-      description "Send client-id back when the client sent it. This is conformant
-                   with RFC6842, but some older, buggy clients have problems with it.";
+      description "Send client-id back when the client sent it. This
+                   is conformant with RFC6842, but some older, buggy
+                   clients have problems with it.";
     }
 
     uses match-client-id;
     uses next-server;
     uses server-hostname;
     uses boot-file-name;
-
-    leaf user-context {
-      type kea:user-context;
-      description "DHCPv4 server user context. Arbitrary JSON data can be stored here.";
-    }
-
-    container sanity-checks {
-      description "Sanity checks.";
-      leaf lease-checks {
-        type enumeration {
-          enum "none" {
-            description "No checks.";
-          }
-          enum "warn" {
-            description "When a check fails print a warning and accept the
-              lease.";
-          }
-          enum "fix" {
-            description "When a check fails try to fix it and accept the
-              lease.";
-          }
-          enum "fix-del" {
-            description "When a check fails try to fix it and reject the
-              lease if still bad.";
-          }
-          enum "del" {
-            description "When a check fails reject the lease.";
-          }
-        }
-        default "warn";
-        description "Lease checks: verify subnet-id consistency on memfile
-          loading.";
+    uses kea:user-context {
+      refine user-context {
+        description "DHCPv4 server user context. Arbitrary JSON data can
+                     be stored here.";
       }
     }
+    uses dhcp:sanity-checks;
+  }
+
+  container logging {
+    description "Logging";
+    config true;
+
+    uses logging:configuration;
   }
 
   /*
   * State data
   */
-  grouping state {
+  container state {
     description "State of Kea DHCPv4 server.";
+    config false;
 
     container leases {
       description "Kea DHCPv4 leases.";
@@ -831,11 +398,10 @@ module kea-dhcp4 {
           type binary;
           description "Lease client-id.";
         }
-        leaf valid-lifetime {
-          type uint32;
-          units "seconds";
-          mandatory true;
-          description "Lease valid lifetime.";
+        uses dhcp:valid-lifetime {
+          refine valid-lifetime {
+            mandatory true;
+          }
         }
         leaf cltt {
           type uint32;
@@ -864,7 +430,7 @@ module kea-dhcp4 {
           description "Lease hostname.";
         }
         leaf state {
-          type lease-state;
+          type dhcp:lease-state;
           default "default";
           description "Lease state.";
         }
@@ -905,42 +471,24 @@ module kea-dhcp4 {
       description "Kea DHCPv4 hosts.";
       list host {
         key "subnet-id identifier-type identifier";
-        leaf identifier {
-          type string;
-          mandatory true;
-          description "Host identifier.";
-        }
         leaf identifier-type {
           type host-identifier-type;
           mandatory true;
           description "Host identifier type.";
         }
-        leaf subnet-id {
-          type uint32;
-          mandatory true;
-          description "Host subnet ID.";
-        }
+        uses dhcp:host-identifier;
+        uses dhcp:host-subnet-id;
         leaf ip-address {
           type inet:ipv4-address;
           description "Host reserved IP address.";
         }
-        leaf hostname {
-          type string;
-          description "Host name.";
-        }
-        leaf-list client-classes {
-          type string;
-          description "Host client classes. (if host identifier matches, a client's
-                         packet will be added to the classes liste here)";
-        }
+        uses dhcp:host-hostname;
+        uses dhcp:host-client-classes;
         uses option-data-list;
         uses next-server;
         uses server-hostname;
         uses boot-file-name;
-        leaf user-context {
-          type kea:user-context;
-          description "Host user context. Arbitrary JSON data can be stored here.";
-        }
+        uses dhcp:host-user-context;
         leaf auth-key {
           type string;
           description "Host authentication key (unused in DHCPv4).";
diff --git a/src/lib/yang/models/kea-dhcp6.yang b/src/lib/yang/models/kea-dhcp6.yang
index 49aaeac027..55372493f2 100644
--- a/src/lib/yang/models/kea-dhcp6.yang
+++ b/src/lib/yang/models/kea-dhcp6.yang
@@ -12,11 +12,18 @@ module kea-dhcp6 {
   import kea-types {
     prefix kea;
   }
+  import kea-dhcp-types {
+    prefix dhcp;
+  }
+  import kea-logging {
+    prefix logging;
+  }
+
 
   organization "Internet Systems Consortium";
   contact "kea-dev@lists.isc.org";
   description "This model defines a YANG data model that can be
-    used to configure and manage a Kea DHCPv6 server.";
+               used to configure and manage a Kea DHCPv6 server.";
 
   revision 2018-08-20 {
     description "Initial revision";
@@ -35,25 +42,6 @@ module kea-dhcp6 {
     description "Host identifier type.";
   }
 
-  typedef host-reservation-mode {
-    type enumeration {
-      enum "disabled";
-      enum "out-of-pool";
-      enum "all";
-      enum "global";
-    }
-    description "Host reservation mode.";
-  }
-
-  typedef lease-state {
-    type enumeration {
-      enum "default";
-      enum "declined";
-      enum "expired-reclaimed";
-    }
-    description "Defines state of the lease.";
-  }
-
   /*
   * Groupings
   */
@@ -65,30 +53,6 @@ module kea-dhcp6 {
     }
   }
 
-  grouping valid-lifetime {
-    leaf valid-lifetime {
-      type uint32;
-      units "seconds";
-      description "Valid lifetime.";
-    }
-  }
-
-  grouping renew-timer {
-    leaf renew-timer {
-      type uint32;
-      units "seconds";
-      description "Renew timer.";
-    }
-  }
-
-  grouping rebind-timer {
-    leaf rebind-timer {
-      type uint32;
-      units "seconds";
-      description "Rebind timer.";
-    }
-  }
-
   grouping relay {
     leaf-list ip-addresses {
       type inet:ipv6-address;
@@ -96,19 +60,27 @@ module kea-dhcp6 {
     }
   }
 
+  grouping rapid-commit {
+    leaf rapid-commit {
+      type boolean;
+      default false;
+    }
+  }
+
   grouping subnet6-list {
     description "Subnet6 list.";
     list subnet6 {
       key id;
       ordered-by user;
       uses preferred-lifetime;
-      uses valid-lifetime;
-      uses renew-timer;
-      uses rebind-timer;
+      uses dhcp:valid-lifetime;
+      uses dhcp:renew-timer;
+      uses dhcp:rebind-timer;
       uses option-data-list;
       container pools {
         list pool {
           key "start-address end-address";
+          ordered-by user;
           leaf prefix {
             type inet:ipv6-prefix;
             description "Pool prefix.";
@@ -124,24 +96,15 @@ module kea-dhcp6 {
             description "Last IPv6 address in a pool.";
           }
           uses option-data-list;
-          leaf client-class {
-            type string;
-            description "Pool client class guard. (only clients belonging to this
-                         class will be allowed in this pool).";
-          }
-          leaf-list require-client-classes {
-            type string;
-            description "Pool require client classes.";
-          }
-          leaf user-context {
-            type kea:user-context;
-            description "Pool user context. Arbitrary JSON data can be stored here.";
-          }       
+          uses dhcp:pool-client-class;
+          uses dhcp:pool-require-client-classes;
+          uses dhcp:pool-user-context;
         }
       }
       container pd-pools {
         list pd-pool {
           key prefix;
+          ordered-by user;
           leaf prefix {
             type inet:ipv6-prefix;
             mandatory true;
@@ -152,23 +115,28 @@ module kea-dhcp6 {
             description "Prefix pool delegated length.";
           }
           uses option-data-list;
-          leaf client-class {
-            type string;
-            description "Prefix pool client class guard. (only clients belonging to this
-                         class will be allowed in this pool).";
+          uses dhcp:client-class {
+            refine client-class {
+              description "Prefix pool client class guard. (only
+                           clients belonging to this class will be
+                           allowed in this pool).";
+            }
           }
-          leaf-list require-client-classes {
-            type string;
-            description "Prefix pool require client classes.";
+          uses dhcp:require-client-classes {
+            refine require-client-classes {
+              description "Prefix pool require client classes.";
+            }
           }
           leaf excluded-prefix {
             type inet:ipv6-prefix;
             description "Prefix pool excluded prefix.";
           }
-          leaf user-context {
-            type kea:user-context;
-            description "Prefix pool user context. Arbitrary JSON data can be stored here.";
-          }       
+          uses kea:user-context {
+            refine user-context {
+              description "Prefix pool user context. Arbitrary JSON data
+                           can be stored here.";
+            }
+          }
         }
       }
       leaf subnet {
@@ -176,54 +144,27 @@ module kea-dhcp6 {
         mandatory true;
         description "IPv6 subnet prefix.";
       }
-      leaf interface {
-        type string;
-        description "Name of the network interface this subnet is directly
-                     accessible with (optional).";
-      }
-      leaf interface-id {
-        type string;
-        description "Subnet interface-id option.";
-      }
-      leaf id {
-        type uint32 {
-          range 1..max;
+      uses dhcp:subnet-interface;
+      uses dhcp:subnet-interface-id;
+      uses dhcp:subnet-id;
+      uses rapid-commit {
+        refine rapid-commit {
+          description "Subnet rapid commit flag.";
         }
-        mandatory true;
-        description "Subnet ID, a unique identifier used to locate or reference
-                     a subnet.";
-      }
-      leaf rapid-commit {
-        type boolean;
-        default false;
-        description "Subnet rapid commit flag.";
-      }
-      leaf client-class {
-        type string;
-        description "Subnet client class guard (only clients belonging to this
-                     clas will be allowed in this subnet).";
-      }
-      leaf-list require-client-classes {
-        type string;
-        description "Subnet require client classes.";
       }
+      uses dhcp:subnet-client-class;
+      uses dhcp:require-client-classes;
       container reservations {
-        description "A container with host reservations specific to this IPv6 subnet.";
+        description "A container with host reservations specific to
+                     this IPv6 subnet.";
         list host {
           key "identifier-type identifier";
           leaf identifier-type {
             type host-identifier-type;
+            mandatory true;
             description "Host identifier type.";
           }
-          leaf identifier {
-            type string;
-            description "Host identifier.";
-          }
-          leaf-list client-classes {
-            type string;
-            description "Host client classes. (if host identifier matches, a client's
-                         packet will be added to the classes liste here.)";
-          }
+          uses dhcp:host-identifier;
           leaf-list ip-addresses {
             type inet:ipv6-address;
             description "Host reserved IP addresses.";
@@ -232,143 +173,27 @@ module kea-dhcp6 {
             type inet:ipv6-prefix;
             description "Host reserved IP prefixes.";
           }
-          leaf hostname {
-            type string;
-            description "Host DNS name.";
-          }
+          uses dhcp:host-hostname;
+          uses dhcp:host-client-classes;
           uses option-data-list;
-          leaf user-context {
-            type kea:user-context;
-            description "Host user context.";
-          }
+          uses dhcp:host-user-context;
         }
       }
-      leaf reservation-mode {
-        type host-reservation-mode;
-        description "Subnet host reservation mode.";
-      }
+      uses dhcp:subnet-reservation-mode;
       container relay {
         description "Optional information about relay agent.";
         uses relay;
       }
-      leaf user-context {
-        type kea:user-context;
-        description "Subnet user context.";
-      }
-    }
-  }
-
-  grouping database {
-    leaf database-type {
-      type string;
-      mandatory true;
-      description "Database type (e.g. mysql).";
-    }
-    leaf user {
-      type string;
-      description "Database user name.";
-    }
-    leaf password {
-      type string;
-      description "Database user password.";
-    }
-    leaf host {
-      type string;
-      description "Database host.";
-    } 
-    leaf name {
-      type string;
-      description "Database name.";
-    }
-    leaf persist {
-      type boolean;
-      default true;
-      description "Write lease to disk file. This parameter applies only to
-                  memfile backend.";
-    }
-    leaf port {
-      type uint16;
-      description "Database port.";
-    }
-    leaf lfc-interval {
-      type uint32;
-      units "seconds";
-      default 3600;
-      description "Interval between two lease file cleanups.";
-    }
-    leaf readonly {
-      type boolean;
-      default false;
-      description "If set to true, the database will be connected in read-only
-                   mode. This does not make sense for lease databases, only for
-                   host reservations and possibly for upcoming config backend.";
-    }
-    leaf connect-timeout {
-      type uint32;
-      units "milliseconds";
-      description "Database connection timeout.";
-    }
-    leaf contact-points {
-      type string;
-      description "Cassandra database contact points.";
-    }
-    leaf keyspace {
-      type string;
-      description "Cassandra database keyspace.";
-    }
-    leaf max-reconnect-tries {
-      type uint32;
-      default 0;
-      description "Maximum of recovery attempts before exit.";
-    }
-    leaf reconnect-wait-time {
-      type uint32;
-      default 0;      
-      units "milliseconds";
-      description "Waiting delay between two recovery attempts.";
-    }
-    leaf request-timeout {
-      type uint32;
-      units "milliseconds";
-      description "Timeout waiting for a response.";
-    }
-    leaf tcp-keepalive {
-      type uint32;
-      units "seconds";
-      default 0;
-      description "TCP keepalive for the database connection.";
-    }
-    leaf tcp-nodelay {
-      type boolean;
-      default true;
-      description "TCP nodelay for the database connection.";
-    } 
-    leaf user-context {
-      type kea:user-context;
-      description "Database user context.";
+      uses dhcp:subnet-user-context;
     }
   }
 
   grouping client-class {
-    leaf name {
-      type string;
-      mandatory true;
-      description "Client class name.";
-    }
-    leaf test {
-      type string;
-      description "Defines an expression that evaluates every incoming packet.";
-    }
-    leaf only-if-required {
-      type boolean;
-      default false;
-      description "Client class only if required flag.";
-    }
+    uses dhcp:class-name;
+    uses dhcp:class-test;
+    uses dhcp:class-only-if-required;
     uses option-data-list;
-    leaf user-context {
-      type kea:user-context;
-      description "Client class user context.";
-    }
+    uses dhcp:class-user-context;
   }
 
   grouping option-def-list {
@@ -376,44 +201,22 @@ module kea-dhcp6 {
       description "Option definition list.";
       list option-def {
         key "code space";
-        leaf name {
-          type string;
-          mandatory true;
-          description "Name of the new option being defined.";
-        }
         leaf code {
           type uint16;
           mandatory true;
           description "Option code to be used by the new option definition.";
         }
-        leaf type {
-          type string;
-          mandatory true;
-          description "Type of the new option being defined (such as string or uint8).";
-        }
-        leaf record-types {
-          type string;
-          description "Option definition record types.";
-        }
         leaf space {
           type string;
           mandatory true;
           description "Option space for the new option (typically dhcp6).";
         }
-        leaf encapsulate {
-          type string;
-          description "Defines option space this new option encapsulates.
-                       Usually empty.";
-        }
-        leaf array {
-          type boolean;
-          default false;
-          description "Option definition array flag.";
-        }
-        leaf user-context {
-          type kea:user-context;
-          description "Option definition user context.";
-        }
+        uses dhcp:option-def-name;
+        uses dhcp:option-def-type;
+        uses dhcp:option-def-record-types;
+        uses dhcp:option-def-encapsulate;
+        uses dhcp:option-def-array;
+        uses dhcp:option-def-user-context;
       }
     }
   }
@@ -423,14 +226,6 @@ module kea-dhcp6 {
       description "Option data list.";
       list option-data {
         key "code space";
-        leaf name {
-          type string;
-          description "Option name.";
-        }
-        leaf data {
-          type string;
-          description "Option data.";
-        }
         leaf code {
           type uint16;
           mandatory true;
@@ -441,40 +236,28 @@ module kea-dhcp6 {
           mandatory true;
           description "Option space.";
         }
-        leaf csv-format {
-          type boolean;
-          default true;
-          description "If true, the option is specified as comma separated values.
-                       If false, it is expected as a hex string.";
-        }
-        leaf always-send {
-          type boolean;
-          default false;
-          description "Defines whether to always send the option, regardless if the
-                       client requested it or not.";
-        }
-        leaf user-context {
-          type kea:user-context;
-          description "Option user context. Arbitrary JSON data can be stored here.";
-        }
-      }   
+        uses dhcp:option-data-name;
+        uses dhcp:option-data-data;
+        uses dhcp:option-data-csv-format;
+        uses dhcp:option-data-always-send;
+        uses dhcp:option-data-user-context;
+      }
     }
   }
 
-  grouping configuration {
-    description "Contains parameters for DHCPv6 server configuration.";
+  /*
+  * Data Nodes
+  */
 
-    uses preferred-lifetime;
-    uses valid-lifetime;
-    uses renew-timer;
-    uses rebind-timer;
+  container config {
+    description "Contains DHCPv6 server configuration.";
+    config true;
 
-    leaf decline-probation-period {
-      type uint32;
-      units "seconds";
-      default 86400;
-      description "Decline probabation period.";
-    }
+    uses preferred-lifetime;
+    uses dhcp:valid-lifetime;
+    uses dhcp:renew-timer;
+    uses dhcp:rebind-timer;
+    uses dhcp:decline-probation-period;
 
     container subnet6 {
       description "Global subnet6 list.";
@@ -485,54 +268,32 @@ module kea-dhcp6 {
       description "Defines a list of IPv6 shared networks.";
       list shared-network {
         key name;
-        leaf name {
-          type string;
-          mandatory true;
-          description "Shared network name.";
-        }
+        uses dhcp:network-name;
         container subnet6 {
-          description "List of IPv6 subnets that belong to this shared network.";
+          description "List of IPv6 subnets that belong to this shared
+                       network.";
           uses subnet6-list;
         }
-        leaf interface {
-          type string;
-          description "Shared network interface.";
-        }
-        leaf interface-id {
-          type string;
-          description "Shared network interface-id option.";
-        }
-        uses renew-timer;
-        uses rebind-timer;
+        uses dhcp:network-interface;
+        uses dhcp:network-interface-id;
+        uses dhcp:renew-timer;
+        uses dhcp:rebind-timer;
         uses option-data-list;
         container relay {
           description "Optional information about relay agent.";
           uses relay;
         }
-        leaf reservation-mode {
-          type host-reservation-mode;
-          description "Shared network host reservation mode.";
-        }
-        leaf client-class {
-          type string;
-          description "Shared network client class guard (only clients belonging
-                       to this class will be allowed in this shared network).";
-        }
-        leaf-list require-client-classes {
-          type string;
-          description "Shared network require client classes.";
-        }
+        uses dhcp:network-reservation-mode;
+        uses dhcp:network-client-class;
+        uses dhcp:require-client-classes;
         uses preferred-lifetime;
-        leaf rapid-commit {
-          type boolean;
-          default false;
-          description "Shared network rapid commit flag.";
-        }
-        uses valid-lifetime;
-        leaf user-context {
-          type kea:user-context;
-          description "Shared network user context.";
+        uses rapid-commit {
+          refine rapid-commit {
+            description "Shared network rapid commit flag.";
+          }
         }
+        uses dhcp:valid-lifetime;
+        uses dhcp:network-user-context;
       }
     }
 
@@ -543,30 +304,11 @@ module kea-dhcp6 {
         description "Name of the interface (e.g. eth0) or name/address
                      (e.g. eth0/2001:db8::1) or * (use all interfaces).";
       }
-      leaf re-detect {
-        type boolean;
-        default false;
-        description "Re-detect interfaces at each reconfiguration.";
-      }
-      leaf user-context {
-        type kea:user-context;
-        description "Interfaces user context.";
-      }
-    }
-    
-    container lease-database {
-      description "Lease database.";
-      presence "Enable lease database.";
-      uses database;
+      uses dhcp:interfaces-re-detect;
+      uses dhcp:interfaces-user-context;
     }
 
-    container hosts-databases {
-      description "Hosts databases.";
-      list hosts-database {
-        key database-type;
-        uses database;
-      }
-    }
+    uses dhcp:databases;
 
     leaf-list relay-supplied-options {
       type string;
@@ -595,44 +337,7 @@ module kea-dhcp6 {
     uses option-def-list;
     uses option-data-list;
     uses kea:hooks-libraries;
-
-    container expired-leases-processing {
-      description "Expired leases processing setup.";
-      leaf reclaim-timer-wait-time {
-        type uint32;
-        units "seconds";
-        default 10;
-        description "Interval between reclamation cycles.";
-      }
-      leaf flush-reclaimed-timer-wait-time {
-        type uint32;
-        units "seconds";
-        default 25;
-        description "Interval between reclaimed leases collection.";
-      }
-      leaf hold-reclaimed-time {
-        type uint32;
-        units "seconds";
-        default 3600;
-        description "Hold timer for re-assignment.";
-      }
-      leaf max-reclaim-leases {
-        type uint32;
-        default 100;
-        description "Maximum number of reclaimed leases per cycle.";
-      }
-      leaf max-reclaim-time {
-        type uint32;
-        units "milliseconds";
-        default 250;
-        description "Maximum duration of a reclamation cycle.";
-      }
-      leaf unwarned-reclaim-cycles {
-        type uint32;
-        default 5;
-        description "Maximum numbers of uncomplete cycles before warning.";
-      }
-    }
+    uses dhcp:expired-leases-processing;
 
     container server-id {
       description "Server DUID.";
@@ -671,151 +376,31 @@ module kea-dhcp6 {
       }
     }
 
-    leaf dhcp4o6-port {
-      type uint16;
-      description "DHCPv4-over-DHCPv6 interserver port.";
-    }
-
-    container control-socket {
-      description "Control socket";
-      presence "Enable control socket.";
-      uses kea:control-socket;
-    }
-
-    container dhcp-ddns {
-      description "DHCP-DDNS client setup.";
-      leaf enable-updates {
-        type boolean;
-        default false;
-        description "Enable DHCP-DDNS updates.";
-      }
-      leaf qualifying-suffix {
-        type string;
-        description "DHCP-DDNS qualifying suffix.";
-      }
-      leaf server-ip {
-        type inet:ip-address;
-        default "127.0.0.1";
-        description "DHCP-DDNS server IP address.";
-      }
-      leaf server-port {
-        type uint16;
-        default 53001;
-        description "DHCP-DDNS server port.";
-      }
-      leaf sender-ip {
-        type inet:ip-address;
-        description "DHCP-DDNS sender IP address.";
-      }
-      leaf sender-port {
-        type uint16;
-        description "DHCP-DDNS sender port.";
-      }
-      leaf max-queue-size {
-        type uint32;
-        default 1024;
-        description "Maximum DHCP-DDNS queue size.";
-      }
-      leaf ncr-protocol {
-        type enumeration {
-          enum "UDP";
-          enum "TCP";
-        }
-        default "UDP";
-        description "Protocol to use for DHCP-DDNS communication.
-                     Currently only UDP is supported.";
-      }
-      leaf ncr-format {
-        type enumeration {
-          enum "JSON";
-        }
-        default "JSON";
-        description "Packet format to use for DHCP-DDNS.";
-      }
-      leaf always-include-fqdn {
-        type boolean;
-        description "???";
-      }
-      leaf override-no-update {
-        type boolean;
-        default false;
-        description "Ignore client request and send update.";
-      }
-      leaf override-client-update {
-        type boolean;
-        default false;
-        description "Ignore client delegation.";
-      }
-      leaf replace-client-name {
-        type enumeration {
-          enum "when-present";
-          enum "never";
-          enum "always";
-          enum "when-not-present";
-        }
-        default "never";
-        description "Replace the name provided by the client.";
-      }
-      leaf generated-prefix {
-        type string;
-        default "myhost";
-        description "DHCP-DDNS generated prefix.";
-      }
-      leaf hostname-char-set {
-        type string;
-        description "A regex defining invalid characters. If detected, those
-                     will be replaced by hostname-char-replacement.";
-      }
-      leaf hostname-char-replacement {
-        type string;
-        description "Replacement for invalid charaters. See hostname-char-set.";
-      }
-      leaf user-context {
-        type kea:user-context;
-        description "DHCP-DDNS user context. Arbitrary JSON data can be stored here.";
+    uses dhcp:dhcp4o6-port;
+    uses dhcp:control-socket;
+    uses dhcp:dhcp-ddns;
+    uses kea:user-context {
+      refine user-context {
+        description "DHCPv6 server user context. Arbitrary JSON data can
+                     be stored here.";
       }
     }
+    uses dhcp:sanity-checks;
+  }
 
-    leaf user-context {
-      type kea:user-context;
-      description "DHCPv6 server user context. Arbitrary JSON data can be stored here.";
-    }
+  container logging {
+    description "Logging";
+    config true;
 
-    container sanity-checks {
-      description "Sanity checks.";
-      leaf lease-checks {
-        type enumeration {
-          enum "none" {
-            description "No checks.";
-          }
-          enum "warn" {
-            description "When a check fails print a warning and accept the
-              lease.";
-          }
-          enum "fix" {
-            description "When a check fails try to fix it and accept the
-              lease.";
-          }
-          enum "fix-del" {
-            description "When a check fails try to fix it and reject the
-              lease if still bad.";
-          }
-          enum "del" {
-            description "When a check fails reject the lease.";
-          }
-        }
-        default "warn";
-        description "Lease checks: verify subnet-id consistency on memfile
-          loading.";
-      }
-    }
+    uses logging:configuration;
   }
 
   /*
   * State data
   */
-  grouping state {
+  container state {
     description "State of Kea DHCPv6 server.";
+    config false;
 
     container leases {
       description "Kea DHCPv6 leases.";
@@ -831,11 +416,10 @@ module kea-dhcp6 {
           mandatory true;
           description "Lease DUID.";
         }
-        leaf valid-lifetime {
-          type uint32;
-          units "seconds";
-          mandatory true;
-          description "Lease valid lifetime.";
+        uses dhcp:valid-lifetime {
+          refine valid-lifetime {
+            mandatory true;
+          }
         }
         leaf cltt {
           type uint32;
@@ -890,7 +474,7 @@ module kea-dhcp6 {
           description "Lease hostname.";
         }
         leaf state {
-          type lease-state;
+          type dhcp:lease-state;
           default "default";
           description "Lease state.";
         }
@@ -910,7 +494,7 @@ module kea-dhcp6 {
         key subnet-id;
         leaf subnet-id {
           type uint32;
-          mandatory true;         
+          mandatory true;
           description "Subnet ID.";
         }
         leaf total-nas {
@@ -945,21 +529,13 @@ module kea-dhcp6 {
       description "Kea DHCPv6 hosts.";
       list host {
         key "subnet-id identifier-type identifier";
-        leaf identifier {
-          type string;
-          mandatory true;
-          description "Host identifier.";
-        }
         leaf identifier-type {
           type host-identifier-type;
           mandatory true;
           description "Host identifier type.";
         }
-        leaf subnet-id {
-          type uint32;
-          mandatory true;
-          description "Host subnet ID.";
-        }
+        uses dhcp:host-identifier;
+        uses dhcp:host-subnet-id;
         leaf-list ip-addresses {
           type inet:ipv6-address;
           description "Host reserved IP addresses.";
@@ -968,19 +544,10 @@ module kea-dhcp6 {
           type inet:ipv6-prefix;
           description "Host reserved prefixes.";
         }
-        leaf hostname {
-          type string;
-          description "Host name.";
-        }
-        leaf-list client-classes {
-          type string;
-          description "Host client classes.";
-        }
+        uses dhcp:host-hostname;
+        uses dhcp:host-client-classes;
         uses option-data-list;
-        leaf user-context {
-          type kea:user-context;
-          description "Host user context.";
-        }
+        uses dhcp:host-user-context;
         leaf auth-key {
           type string;
           description "Host authentication key.";
diff --git a/src/lib/yang/models/kea-dhcpddns.yang b/src/lib/yang/models/kea-dhcpddns.yang
index af7fb767b1..2de9e735c9 100644
--- a/src/lib/yang/models/kea-dhcpddns.yang
+++ b/src/lib/yang/models/kea-dhcpddns.yang
@@ -12,6 +12,9 @@ module kea-dhcpddns {
   import kea-types {
     prefix kea;
   }
+  import kea-logging {
+    prefix logging;
+  }
 
   organization "Internet Systems Consortium";
   contact "kea-dev@lists.isc.org";
@@ -76,8 +79,13 @@ module kea-dhcpddns {
     }
   }
 
-  grouping configuration {
-    description "Contains parameters for DHCP-DDNS server configuration.";
+  /*
+  * Data Nodes
+  */
+
+  container config {
+    description "Contains DHCP-DDNS server configuration.";
+    config true;
 
     leaf ip-address {
       type inet:ip-address;
@@ -159,4 +167,11 @@ module kea-dhcpddns {
       description "DHCP-DDNS server user context.";
     }
   }
+
+  container logging {
+    description "Logging";
+    config true;
+
+    uses logging:configuration;
+  }
 }
diff --git a/src/lib/yang/models/kea-dhcpv4-server.yang b/src/lib/yang/models/kea-dhcpv4-server.yang
deleted file mode 100644
index 9d6a7bbf22..0000000000
--- a/src/lib/yang/models/kea-dhcpv4-server.yang
+++ /dev/null
@@ -1,585 +0,0 @@
-module ietf-dhcpv4-server {
-  yang-version 1.1;
-  namespace "urn:ietf:params:xml:ns:yang:ietf-dhcpv4-server";
-  prefix "dhcpv4-server";
-
-  import ietf-inet-types {
-    prefix inet;
-  }
-  import ietf-yang-types {
-    prefix yang;
-  }
-  import ietf-dhcpv4-options {
-    prefix dhcpv4-options;
-  }
-  import ietf-dhcpv4-types {
-    prefix dhcpv4-types;
-  }
-  import ietf-interfaces {
-    prefix if;
-  }
-
-  organization "ISC";
-
-  contact
-    "The Kea DHCPv4 model is now maitained by ISC, please send
-     your comments to the kea-dev@lists.isc.org mailing list.
-
-     The original author was Piotr Strzyżewski
-     piotr.strzyzewski@polsl.pl";
-
-  description
-      "This model defines a YANG data model that can be
-       used to configure and manage Kea DHCPv4 server.";
-
-  revision 2018-07-14 {
-    description "Initial revision; mostly based on DHCPv6 version";
-    reference "";
-  }
-
-  /*
-  * Typedef
-  */
-  typedef threshold {
-    type union {
-      type uint16 {
-        range 0..100;
-      }
-      type enumeration {
-        enum "disabled" {
-            description "No threshold";
-        }
-      }
-    }
-    description "Threshold value in percent";
-  }
-
-  /*
-  * Data Nodes
-  */
-  container server {
-    presence "Enables the server";
-    description "DHCPv4 server portion";
-
-    /*
-     * Configuration data
-     */
-    container server-config {
-      description "This container contains the configuration data
-            of a server.";
-      container serv-attributes {
-        description
-         "This container contains basic attributes of a DHCPv4 server
-         such as IPv4 address, server name and so on. Some optional
-         functions that can be provided by the server are also included.";
-        leaf name {
-          type string;
-          description "server's name";
-        }
-        leaf description {
-          type string;
-          description "description of the server.";
-        }
-        leaf-list ipv4-address {
-          type inet:ipv4-address;
-          description "server's IPv4 address.";
-        }
-        leaf-list interfaces-config {
-          // Note - this should probably be references to
-          // entries in the ietf-interfaces model
-          type if:interface-ref;
-          description "A leaf list to denote which one or more interfaces
-            the server should listen on. The default value is to listen
-            on all the interfaces. This node is also used to set a unicast
-            address for the server to listen with a specific interface.
-            For example, if someone want the server to listen on a unicast
-            address with a specific interface, she/he can use the format
-            like 'eth0/192.0.2.1'.";
-        }
-        uses dhcpv4-types:vendor-infor;
-      }
-
-      container option-sets {
-        description "DHCPv4 employs various options to carry additional
-          information and parameters in DHCP messages. This container defines
-          all the possible options that need to be configured at the server
-          side.";
-        list option-set {
-            key option-set-id;
-            description "A server may allow different option sets to be
-              configured for different conditions (i.e. different networks,
-              clients and etc). This 'option-set' list enables various sets of
-              options being defined and configured in a single server. Different
-              sets are distinguished by the key called 'option-set-id'. All the
-              possible options discussed above are defined in the list and each
-              option is corresponding to a container. Since all the options in
-              the list are optional, each container in this list has a 'presence'
-              statement to indicate whether this option (container) will be
-              included in the current option set or not. In addition, each container
-              also has a 'if-feature' statement to indicate whether the server
-              supports this option (container).";
-            leaf option-set-id {
-              type uint32;
-              description "option set id";
-            }
-          uses dhcpv4-options:server-option-definitions;
-        }
-      }
-
-      container network-ranges {
-        description "This model supports a hierarchy to achieve dynamic
-          configuration. This level represents IPv4 subnets. The top level is a global
-          level which is defined as the container 'network-ranges'. The following
-          levels are defined as sub-containers under it. The 'network-ranges'
-          (which reprents pools within subnets) contains the parameters
-          (e.g. option-sets) that would be allocated to all the clients served by
-          this server.";
-
-        leaf option-set-id {
-          type leafref {
-            path "/server/server-config/option-sets/option-set/option-set-id";
-          }
-          description
-            "The ID field of relevant global option-set to be provisioned to
-            clients.";
-        }
-        list network-range {
-          key network-range-id;
-          description
-          "Under the 'network-ranges' container, a 'network-range' list
-           is defined to configure the server at a network level which is also
-           considered as the second level. Different network are identified by the
-           key 'network-range-id'. This is because a server may have different
-           configuration parameters (e.g. option sets) for different networks.";
-          leaf network-range-id {
-            type uint32;
-            mandatory true;
-            description "equivalent to subnet id";
-          }
-          leaf network-description {
-            type string;
-            description "description of the subnet";
-          }
-          leaf network-prefix {
-            type inet:ipv4-prefix;
-            mandatory true;
-            description "subnet prefix";
-          }
-          leaf option-set-id {
-            type leafref {
-              path "/server/server-config/option-sets/option-set/option-set-id";
-            }
-            description "The ID field of relevant option-set to be provisioned to
-            clients of this network-range.";
-          }
-
-          container address-pools {
-            description
-            "A container that describes the DHCPv4 server's
-             address pools.";
-            list address-pool {
-              key pool-id;
-              description "A DHCPv4 server can be configured with
-              several address pools. This list defines such address pools
-              which are distinguished by the key called 'pool-id'.";
-              leaf pool-id {
-                type uint32;
-                mandatory true;
-                description "pool id";
-              }
-              leaf pool-prefix {
-                type inet:ipv4-prefix;
-                mandatory true;
-                description "pool prefix";
-              }
-              leaf start-address {
-                type inet:ipv4-address-no-zone;
-                mandatory true;
-                description "start address";
-              }
-              leaf end-address {
-                type inet:ipv4-address-no-zone;
-                mandatory true;
-                description "end address";
-              }
-              leaf renew-time {
-                type uint32;
-                units "seconds";
-                description "renew time";
-              }
-              leaf rebind-time {
-                type uint32;
-                units "seconds";
-                description "rebind time";
-              }
-//              leaf rapid-commit {
-//                type boolean;
-//                mandatory false;
-//                description "A boolean value specifies whether the pool
-//                supports client-server exchanges involving two messages.";
-//              }
-              leaf client-class {
-                type string;
-                description
-                "If this leaf is specified, this pool will only serve
-                the clients belonging to this class.";
-              }
-              leaf max-address-count {
-                type threshold;
-                description "maximum count of addresses that can
-                  be allocated in this pool. This value may be
-                  less than count of total addresses.";
-              }
-              leaf option-set-id {
-                type leafref {
-                  path "/server/server-config/option-sets/option-set/option-set-id";
-                }
-                description "The ID field of relevant option-set to be
-                    provisioned to clients of this address-pool.";
-              }
-            }
-          }
-
-          container host-reservations {
-            description
-              "This container allows the server to make reservations at host level.";
-            list host-reservation {
-              key cli-id;
-              description "This list allows the server to reserve addresses,
-              prefixes, hostname and options for different clients.";
-              leaf cli-id {
-                type uint32;
-                mandatory true;
-                description "client id";
-              }
-
-              choice client-identifier {
-                description "When making reservations, the server needs to choose a
-                identifier to identify the client. Currently 'Client ID' and
-                'hardware address' are supported.";
-                case client-id {
-                  description "Client ID";
-                  leaf client-ident {
-                    type string;
-                    description "Client ID";
-                  }
-                }
-                case hw-address {
-                  description "hardware address";
-                  leaf hardware-address {
-                    type yang:mac-address;
-                    description "MAC address of client";
-                  }
-                }
-              }
-
-              leaf-list reserv-addr {
-                type inet:ipv4-address-no-zone;
-                description "reserved addr";
-              }
-
-              leaf hostname {
-                type string;
-                description "reserved hostname";
-              }
-
-              leaf option-set-id {
-                type leafref {
-                  path "/server/server-config/option-sets/option-set/option-set-id";
-                }
-                description "The ID field of relevant option-set to be provisioned
-                  in the host reservation.";
-              }
-            }
-          }
-
-        }
-      }
-
-/*
-      container relay-opaque-paras {
-        description "This container contains some opaque values in Relay Agent
-          options that need to be configured on the server side only for value
-          match. Such Relay Agent options include Interface-Id option,
-          Remote-Id option and Subscriber-Id option.";
-        list relays {
-          key relay-name;
-          description "relay agents";
-          leaf relay-name {
-            type string;
-            mandatory true;
-            description "relay agent name";
-          }
-          list interface-info {
-            key if-name;
-            description "interface info";
-            leaf if-name {
-              type string;
-              mandatory true;
-              description "interface name";
-            }
-            leaf interface-id {
-              type string;
-              mandatory true;
-              description "interface id";
-            }
-          }
-          list subscribers {
-            key subscriber;
-            description "subscribers";
-            leaf subscriber {
-              type uint32;
-              mandatory true;
-              description "subscriber";
-            }
-            leaf subscriber-id {
-              type string;
-              mandatory true;
-              description "subscriber id";
-            }
-          }
-          list remote-host {
-            key ent-num;
-            description "remote host";
-            leaf ent-num {
-              type uint32;
-              mandatory true;
-              description "enterprise number";
-            }
-            leaf remote-id {
-              type string;
-              mandatory true;
-              description "remote id";
-            }
-          }
-        }
-      }
-*/
-    }
-
-    /*
-     * State data
-     */
-    container server-state {
-      config "false";
-      description "states of server";
-      container network-ranges {
-        description "This model supports a hierarchy to achieve dynamic configuration.
-          That is to say we could configure the server at different levels through
-          this model. The top level is a global level which is defined as the container
-          'network-ranges'. The following levels are defined as sub-containers under it.
-          The 'network-ranges' contains the parameters (e.g. option-sets) that would be
-          allocated to all the clients served by this server.";
-        list network-range {
-          key network-range-id;
-          description "The ID field of relevant option-set to be provisioned
-            to clients of this network-range.";
-          leaf network-range-id {
-            type uint32;
-            mandatory true;
-            description "equivalent to subnet id";
-          }
-          container address-pools {
-            description "A container that describes the DHCPv4 server's address pools";
-              list address-pool {
-                key pool-id;
-                description "A DHCPv4 server can be configured with
-                several address pools. This list defines such address pools
-                which are distinguished by the key called 'pool-id'.";
-                leaf pool-id {
-                  type uint32;
-                  mandatory true;
-                  description "pool id";
-                }
-                leaf total-address-count {
-                  type uint32;
-                  mandatory true;
-                  description "count of total addresses in the pool";
-                }
-                leaf allocated-address-conut {
-                  type uint32;
-                  mandatory true;
-                  description "count of allocated addresses in the pool";
-                }
-              }
-              list binding-info {
-                key cli-id;
-                description "A list that records a binding information for each DHCPv4
-                  client that has already been allocated IPv4 addresses.";
-                leaf cli-id {
-                  type uint32;
-                  mandatory true;
-                  description "client id";
-                }
-                list cli-hw {
-                  key hw-address;
-                  description "client host id";
-                  leaf hw-address {
-                    type yang:mac-address;
-                    mandatory true;
-                    description "HW address";
-                  }
-                  leaf-list cli-addr {
-                    type inet:ipv4-address;
-                    description "client addr";
-                  }
-                  leaf pool-id {
-                    type uint32;
-                    mandatory true;
-                    description "pool id";
-                  }
-                }
-              }
-            }
-
-          container host-reservations {
-            description "This container provides host reservations in the host level.";
-            list binding-info {
-              key cli-id;
-              description
-                "A list records a binding information for each DHCPv4
-                client that has already been alloated IPv4 addresses or prefixes
-                by host reservations.";
-              leaf cli-id {
-                type uint32;
-                mandatory true;
-                description "client id";
-              }
-              list cli-hw {
-                key hw-address;
-                description "client host id";
-                leaf hw-address {
-                  type yang:mac-address;
-                  mandatory true;
-                  description "HW address";
-                }
-                leaf-list cli-addr {
-                  type inet:ipv4-address;
-                  description "client addr";
-                }
-              }
-            }
-          }
-
-          }
-        }
-
-        container packet-stats {
-          description "A container presents the packet statistics related to
-            the DHCPv4 server.";
-          leaf request-count {
-            type uint32;
-            mandatory true;
-            description "request counter";
-          }
-          leaf renew-count {
-            type uint32;
-            mandatory true;
-            description "renew counter";
-          }
-          leaf rebind-count {
-            type uint32;
-            mandatory true;
-            description "rebind counter";
-          }
-          leaf decline-count {
-            type uint32;
-            mandatory true;
-            description "decline count";
-          }
-          leaf release-count {
-            type uint32;
-            mandatory true;
-            description "release counter";
-          }
-          leaf info-req-count {
-            type uint32;
-            mandatory true;
-            description "information request counter";
-          }
-          leaf advertise-count {
-            type uint32;
-            mandatory true;
-            description "advertise counter";
-          }
-          leaf confirm-count {
-            type uint32;
-            mandatory true;
-            description "confirm counter";
-          }
-          leaf reconfigure-count {
-            type uint32;
-            mandatory true;
-            description "reconfigure counter";
-          }
-          leaf relay-forward-count {
-            type uint32;
-            mandatory true;
-            description "relay forward counter";
-          }
-          leaf relay-reply-count {
-            type uint32;
-            mandatory true;
-            description "relay reply counter";
-          }
-        }
-      }
-    }
-
-  /*
-  * Notifications
-  */
-
-  notification notifications {
-    description "dhcpv4 server notification module";
-    container dhcpv4-server-event {
-      description "dhcpv4 server event";
-      container address-pool-running-out {
-        description "Raised when the address pool is going to
-          run out. A threshold for utilization ratio of the pool has
-          been defined in the server feature so that it will notify the
-          administrator when the utilization ratio reaches the
-          threshold, and such threshold is a settable parameter.";
-        leaf total-address-count {
-          type uint32;
-          mandatory true;
-          description "Count of total addresses in the pool.";
-        }
-        leaf max-address-count {
-          type uint32;
-          mandatory true;
-          description "Maximum count of addresses that can be allocated
-            in the pool. This value may be less than count of total
-            addresses.";
-        }
-        leaf allocated-address-conut {
-          type uint32;
-          mandatory true;
-          description "Count of allocated addresses in the pool.";
-        }
-        leaf serv-name {
-          type string;
-          description "server name";
-        }
-        leaf pool-name {
-          type string;
-          mandatory true;
-          description "pool name";
-        }
-      }
-      container invalid-client-detected {
-        description "Raised when the server has found a client which
-          can be regarded as a potential attacker. Some description
-          could also be included.";
-        leaf hw {
-          type yang:mac-address;
-          description "HW address";
-        }
-        leaf description {
-          type string;
-          description "description of the event";
-        }
-      }
-    }
-  }
-}
diff --git a/src/lib/yang/models/kea-server.yang b/src/lib/yang/models/kea-server.yang
deleted file mode 100644
index 536600f244..0000000000
--- a/src/lib/yang/models/kea-server.yang
+++ /dev/null
@@ -1,85 +0,0 @@
-module kea-server {
-  yang-version 1.1;
-  namespace "urn:ietf:params:xml:ns:yang::kea-server";
-  prefix "kea-server";
-
-  import kea-dhcp4 {
-    prefix dhcp4;
-  }
-  import kea-dhcp6 {
-    prefix dhcp6;
-  }
-  import kea-dhcpddns {
-    prefix d2;
-  }
-  import kea-control-agent {
-    prefix agent;
-  }
-  import kea-logging {
-    prefix logging;
-  }
-
-  organization "Internet Systems Consortium";
-  contact "kea-dev@lists.isc.org";
-  description "This model defines a YANG data model that can be
-    used to define some commonly used Kea server";
-
-  revision 2018-08-20 {
-    description "Initial revision";
-    reference "";
-  }
-
-  /*
-  * Data Nodes
-  */
-  container dhcp4 {
-    presence "Enables DHCPv4 server";
-    description "DHCPv4 server configuration";
-
-    uses dhcp4:configuration;
-  }
-
-  container dhcp6 {
-    presence "Enables DHCPv6 server";
-    description "DHCPv6 server configuration";
-
-    uses dhcp6:configuration;
-  }
-
-  container dhcpddns {
-    presence "Enables DHCP-DDNS server";
-    description "DHCP-DDNS server configuration";
-
-    uses d2:configuration;
-  }
-
-  container control-agent {
-    presence "Enables control agent";
-    description "Control agent configuration";
-
-    uses agent:configuration;
-  }
-
-  container logging {
-    description "Logging";
-
-    uses logging:configuration;
-  }
-
-  /*
-  * State data
-  */
-  container state {
-    config true;
-
-    container dhcp4 {
-      description "DHCPv4 server state.";
-      uses dhcp4:state;
-    }
-
-    container dhcp6 {
-      description "DHCPv6 server state.";
-      uses dhcp6:state;
-    }
-  }
-}
diff --git a/src/lib/yang/models/kea-types.yang b/src/lib/yang/models/kea-types.yang
index e6954e9512..7639600393 100644
--- a/src/lib/yang/models/kea-types.yang
+++ b/src/lib/yang/models/kea-types.yang
@@ -12,8 +12,7 @@ module kea-types {
 
   organization "Internet Systems Consortium";
   contact "kea-dev@lists.isc.org";
-  description "This model defines a YANG data model that can be
-    used to define some commonly used Kea types";
+  description "This file defines some commonly used Kea types and groupings.";
 
   revision 2018-08-20 {
     description "Initial revision";
@@ -31,6 +30,12 @@ module kea-types {
   /*
   * Grouping
   */
+  grouping user-context {
+    leaf user-context {
+      type user-context;
+    }
+  }
+
   grouping control-socket {
     description "Control socket.";
     leaf socket-name {