Repository : ssh://git@open-mesh.org/doc
On branches: batman-adv-doc,master
commit b411f17bb490b941abcc4926ef023b28e9d31890 Author: Marek Lindner lindner_marek@yahoo.de Date: Sat Apr 11 07:56:00 2009 +0800
minor "assumption" fix
b411f17bb490b941abcc4926ef023b28e9d31890 batman_iv.docbook | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/batman_iv.docbook b/batman_iv.docbook index 0b47682f..bf7004a4 100644 --- a/batman_iv.docbook +++ b/batman_iv.docbook @@ -379,7 +379,7 @@ So far, B.A.T.M.A.N. IV focusses only on the link quality to evaluate paths but not on the number of hops in the path as it is unaware of the topology beyond its horizon. In certain network setups the link quality of the neighbors is very similar whereas the number of hops is not. In these scenarios it is very desirable to choose the shortest path to reduce latency and to safe bandwidth (on wireless mediums). The following section is going to illustrate the issue and how it is going to be addressed using an Ethernet network as example for the sake of simplicity. WiFi and other mediums are less susceptible as Ethernet but still affected. </para> <para> - Example: The nodes A, B and C that are connected to a network switch. Node A originates the first message which is received, processed and rebroadcasted by B immediately. The rebroadcast from node B arrives at node C before the message from node A arrives. As the link quality is the same and perfect (in this example) Node C assumes a path towards node A via node B. [penalty1 bild] + Example: The nodes A, B and C that are connected to a network switch. Node A originates the first message which is received, processed and rebroadcasted by B immediately. Lets assume the rebroadcast from node B arrives at node C before the message from node A arrives. As the link quality is the same and perfect (in this example) Node C assumes a path towards node A via node B. [penalty1 bild] </para> <para> To overcome this issue B.A.T.M.A.N. IV introduces a hop penalty: Every time an OGM passes a node the TQ value will be decreased by a fixed value regardless of the asymetric link penalty before rebroadcasting the packet. In the given example it decrease the value of the route via node B and favors the direct connection. [penalty2 bild]