[#1418] Updated v6 tests and doc

2 files changed, 120 insertions, 0 deletions

diff --git a/doc/sphinx/arm/dhcp4-srv.rst b/doc/sphinx/arm/dhcp4-srv.rst
index 214c44bbc9..a2f021a0b5 100644
--- a/doc/sphinx/arm/dhcp4-srv.rst
+++ b/doc/sphinx/arm/dhcp4-srv.rst
@@ -3994,6 +3994,63 @@ enable the option for the whole subnet, the following configuration can be used:
         }
     ],
 
+Lease Caching
+-------------
+
+Clients that attempt renewal frequently can cause the server to update
+and write the database frequently resulting in a performance impact on
+the server. The cache parameters instructs the DHCP server to avoid
+updating leases too frequently thus avoiding this behavior. Instead
+the server assigns the same lease (i.e. reuses it) with no
+modifications except for CLTT (Client Last Transmission Time)
+which does not require disk operations.
+
+The two parameters are the ``cache-threshold`` double and the
+``cache-max-age`` integer and have no default, i.e. the lease caching
+feature must be explicitly enabled. These parameters can be configured
+at the global, shared network and subnet levels. The subnet level has
+the precedence on the shared network level, the global level is used
+as last resort. For example:
+
+::
+
+    "subnet4": [
+        {
+            "pools": [ { "pool":  "192.0.2.1 - 192.0.2.200" } ],
+            "subnet": "192.0.2.0/24",
+            "cache-threshold": .25,
+	    "cache-max-age": 600,
+            "valid-lifetime": 2000,
+            ...
+        }
+    ],
+
+When an already assigned lease can fulfill a client query:
+
+  - any important change e.g. for DDNS parameter, hostname or
+    valid lifetime reduction makes the lease not reusable
+
+  - lease age i.e. the difference between the creation or last modification
+    time and the current time is computed (elapsed duration)
+
+  - if the ``cache-max-age`` is configured, it is compared with the age
+    and too old leases are not reusable (this means that the value 0
+    for ``cache-max-age`` disables the lease cache feature)
+
+  - if the ``cache-threshold`` is configured and is between 0. and 1.
+    it expresses the percentage of the lease valid lifetime which is
+    allowed for the lease age. Values below and including 0. and
+    values greater than 1. disables the lease cache feature.
+    
+In the example a lease with a valid lifetime of 2000 seconds can be
+reused if it was committed less than 500 seconds ago. With a lifetime
+of 3000 seconds the maximum age of 600 seconds applies.
+
+In responses the ``dhcp-lease-time`` option is set to the remaining
+valid lifetime i.e. the expiration date does not change. Other options
+based on the valid lifetime e.g. ``dhcp-renewal-time`` and
+``dhcp-rebinding-time`` also use the remaining lifetime.
+
 .. _host-reservation-v4:
 
 Host Reservation in DHCPv4
@@ -6749,6 +6806,10 @@ used by all servers connecting to the configuration database.
    +-----------------------------+----------------------------+-------------+-------------+-------------+
    | boot-file-name              | yes                        | yes         | yes         | n/a         |
    +-----------------------------+----------------------------+-------------+-------------+-------------+
+   | cache-max-age               | yes                        | todo        | todo        | n/a         |
+   +-----------------------------+----------------------------+-------------+-------------+-------------+
+   | cache-threshold             | yes                        | todo        | todo        | n/a         |
+   +-----------------------------+----------------------------+-------------+-------------+-------------+
    | calculate-tee-times         | yes                        | yes         | yes         | n/a         |
    +-----------------------------+----------------------------+-------------+-------------+-------------+
    | client-class                | n/a                        | yes         | yes         | yes         |
diff --git a/doc/sphinx/arm/dhcp6-srv.rst b/doc/sphinx/arm/dhcp6-srv.rst
index efdb8310d7..1268a63f57 100644
--- a/doc/sphinx/arm/dhcp6-srv.rst
+++ b/doc/sphinx/arm/dhcp6-srv.rst
@@ -3467,6 +3467,61 @@ Our tests reported best results when:
    storing leases. In our case it's 11 * 6 = 66.
 
 
+Lease Caching
+-------------
+
+Clients that attempt renewal frequently can cause the server to update
+and write the database frequently resulting in a performance impact on
+the server. The cache parameters instructs the DHCP server to avoid
+updating leases too frequently thus avoiding this behavior. Instead
+the server assigns the same lease (i.e. reuses it) with no
+modifications except for CLTT (Client Last Transmission Time)
+which does not require disk operations.
+
+The two parameters are the ``cache-threshold`` double and the
+``cache-max-age`` integer and have no default, i.e. the lease caching
+feature must be explicitly enabled. These parameters can be configured
+at the global, shared network and subnet levels. The subnet level has
+the precedence on the shared network level, the global level is used
+as last resort. For example:
+
+::
+
+    "subnet6": [
+        {
+            "subnet": "2001:db8:1:1::/64",
+            "pools": [ { "pool": "2001:db8:1:1::1:0/112" } ],
+            "cache-threshold": .25,
+	    "cache-max-age": 600,
+            "valid-lifetime": 2000,
+            ...
+        }
+    ],
+
+When an already assigned lease can fulfill a client query:
+
+  - any important change e.g. for DDNS parameter, hostname, or
+    preferred or valid lifetime reduction makes the lease not reusable
+
+  - lease age i.e. the difference between the creation or last modification
+    time and the current time is computed (elapsed duration)
+
+  - if the ``cache-max-age`` is configured, it is compared with the age
+    and too old leases are not reusable (this means that the value 0
+    for ``cache-max-age`` disables the lease cache feature)
+
+  - if the ``cache-threshold`` is configured and is between 0. and 1.
+    it expresses the percentage of the lease valid lifetime which is
+    allowed for the lease age. Values below and including 0. and
+    values greater than 1. disables the lease cache feature.
+    
+In the example a lease with a valid lifetime of 2000 seconds can be
+reused if it was committed less than 500 seconds ago. With a lifetime
+of 3000 seconds the maximum age of 600 seconds applies.
+
+In responses used preferred and valid lifetimes are the remaining
+values i.e. the expiration dates do not change.
+
 .. _host-reservation-v6:
 
 Host Reservation in DHCPv6
@@ -6731,6 +6786,10 @@ the global DHCPv6 options (``option-data``) are modified using
    |                             |                            | Network   |           |           | Delegation |
    |                             |                            |           |           |           | Pool       |
    +=============================+============================+===========+===========+===========+============+
+   | cache-max-age               | yes                        | todo      | todo      | n/a       | n/a        |
+   +-----------------------------+----------------------------+-----------+-----------+-----------+------------+
+   | cache-threshold             | yes                        | todo      | todo      | n/a       | n/a        |
+   +-----------------------------+----------------------------+-----------+-----------+-----------+------------+
    | calculate-tee-times         | yes                        | yes       | yes       | n/a       | n/a        |
    +-----------------------------+----------------------------+-----------+-----------+-----------+------------+
    | client-class                | n/a                        | yes       | yes       | yes       | yes        |