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authorPaul Jakma <paul@quagga.net>2010-01-07 06:12:53 +0000
committerPaul Jakma <paul@quagga.net>2010-12-08 17:11:18 +0000
commit57c5c6526df82970ca24293798d278862cf55106 (patch)
tree91847b2de0f333fa3a45691054f38c82f44f7609 /ports/pkg/DESCR
parent94b6bfd28357dfa5a4f478b7393522816976c0b0 (diff)
ospfd: Reset neighbour inactivity timer for any packet arrival
* The hello protocol monitors connectivity in 2 different ways: a) local -> remote b) remote -> local Connectivity is required in both directions (2-way) for adjacencies to form. The first requires a round-trip to detect, and is done by advertising which other hosts a router knows about in its hello messages. This allows a host to detect which other routers are and are not receiving its message. If a remote neighbour delists the local router, then the local router raises a "1-Way Received" event. The latter is straight-forward, and is detected by setting a timer for the neighbour. If another Hello packet is not received within this time then the neighbour is dead, and a separate "Inactive" event is raised. These are 2 different and relatively independent measures. Knowing that we can optimise the 2nd, remote->local measure and reset the timer when /any/ packet arrives from that neighbour. For any packet is as good as a Hello packet. This can help in marginal situations, where the number of protocol messages that must be sent sometimes can exceed the capacity of the network to transmit the messages within the configured dead-time. I.e. an OSPF network with lots of LSAs, slow links and/or slow hosts (e.g. O(10k) LSAs, O(100kbit) links, embedded CPUs, and O(10s) dead-times). This optimisation allows an OSPF network to run closer to this margin, and/or allows networks to perhaps better cope with rare periods of exceptional load, where otherwise they would not. It's fully compatible with plain OSPF implementations and doesn't prejudice dead-neighbour detection. * ospf_nsm.h: Rename HelloReceived event to PacketReceived. * ospf_nsm.c: (nsm_hello_received) -> nsm_packet_received * ospf_packet.c: Schedule PacketReceived whenever a valid message is received.
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