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authorAntonio Quartulli <ordex@autistici.org>2011-04-27 14:27:44 +0200
committerSven Eckelmann <sven@narfation.org>2011-06-20 11:37:24 +0200
commita73105b8d4c765d9ebfb664d0a66802127d8e4c7 (patch)
treeb4b11a4050109d8f042c7ac87a5a6d6d91b5d1d2 /drivers
parentbatman-adv: Unify the first 3 bytes in each packet (diff)
downloadlinux-a73105b8d4c765d9ebfb664d0a66802127d8e4c7.tar.xz
linux-a73105b8d4c765d9ebfb664d0a66802127d8e4c7.zip
batman-adv: improved client announcement mechanism
The client announcement mechanism informs every mesh node in the network of any connected non-mesh client, in order to find the path towards that client from any given point in the mesh. The old implementation was based on the simple idea of appending a data buffer to each OGM containing all the client MAC addresses the node is serving. All other nodes can populate their global translation tables (table which links client MAC addresses to node addresses) using this MAC address buffer and linking it to the node's address contained in the OGM. A node that wants to contact a client has to lookup the node the client is connected to and its address in the global translation table. It is easy to understand that this implementation suffers from several issues: - big overhead (each and every OGM contains the entire list of connected clients) - high latencies for client route updates due to long OGM trip time and OGM losses The new implementation addresses these issues by appending client changes (new client joined or a client left) to the OGM instead of filling it with all the client addresses each time. In this way nodes can modify their global tables by means of "updates", thus reducing the overhead within the OGMs. To keep the entire network in sync each node maintains a translation table version number (ttvn) and a translation table checksum. These values are spread with the OGM to allow all the network participants to determine whether or not they need to update their translation table information. When a translation table lookup is performed in order to send a packet to a client attached to another node, the destination's ttvn is added to the payload packet. Forwarding nodes can compare the packet's ttvn with their destination's ttvn (this node could have a fresher information than the source) and re-route the packet if necessary. This greatly reduces the packet loss of clients roaming from one AP to the next. Signed-off-by: Antonio Quartulli <ordex@autistici.org> Signed-off-by: Marek Lindner <lindner_marek@yahoo.de> Signed-off-by: Sven Eckelmann <sven@narfation.org>
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