Routing Information Protocol (RIP) RIP Updates Earliest IP routing protocol (1 b When router first starts, asks for copy of table for b Neighbors use to iteratively update their tables Sending Updates P Every router listens for updates on UDP port 520 RIP message can contain entries for up to 25 table When every entry changes, send copy of entry to xcept for one causing update(split horizon rule) RIP Staleness/Oscillation Small Infinity Route Timer b Every route has timeout limit of 180 seconds2/16/2008 7 Routing Information Protocol (RIP) z Earliest IP routing protocol (1982 BSD) » Current standard is version 2 (RFC 1723) z Features » Every link has cost 1 37 37 Every link has cost 1 » “Infinity” = 16 – Limits to networks where everything reachable within 15 hops z Sending Updates » Every router listens for updates on UDP port 520 » RIP message can contain entries for up to 25 table entries RIP Updates z Initial » When router first starts, asks for copy of table for every neighbor » Uses it to iteratively generate own table z Periodic 38 38 » Every 30 seconds, router sends copy of its table to each neighbor » Neighbors use to iteratively update their tables z Triggered » When every entry changes, send copy of entry to neighbors – Except for one causing update (split horizon rule) » Neighbors use to update their tables RIP Staleness / Oscillation Control z Small Infinity » Count to infinity doesn’t take very long z Route Timer 39 39 » Every route has timeout limit of 180 seconds – Reached when haven’t received update from next hop for 6 periods » If not updated, set to infinity » Soft-state refresh Æ important concept!!! z Behavior » When router or link fails, can take minutes to stabilize