From e70ab8102507ba242e11f9d290ca8e5c87028be0 Mon Sep 17 00:00:00 2001 From: Jet Hughes Date: Tue, 18 Oct 2022 13:09:16 +1300 Subject: [PATCH] vault backup: 2022-10-18 13:09:16 --- .../notes/20-network-layer-control-plane.md | 31 +++++++++++++++++-- 1 file changed, 29 insertions(+), 2 deletions(-) diff --git a/content/notes/20-network-layer-control-plane.md b/content/notes/20-network-layer-control-plane.md index a2e857751..1133b4fdc 100644 --- a/content/notes/20-network-layer-control-plane.md +++ b/content/notes/20-network-layer-control-plane.md @@ -111,9 +111,36 @@ each node: "good news (decrease on link cost) travels quickly" -"bad news (increase on link cost) travels slowly" +"bad news (increase on link cost) travels slowly" - count-to-infinity problem - if a link is broken other routers become aware slowly -- +- routers unaware of broken link can "advertise" incorrect costs and create a routing loop +- loop is broken if a hop count threshold is passed + +## link state (LS) vs Distance vector (DV) +message complexity +- LS: n routers O(n²) messages sent +- DV: exhange between neighbors; convergence time varies + +speed of convergence: +- LS: O(n²) algorithm, O(n²) messages +- DV: varies + - may have routing loops + - count-to-infinity problem + +robustness +- LS: + - router can advertise incorrect link cost + - each router computes only its own table +- DV: + - router can advertise incorrect path cost: black holing + - each routers table is used by others: errors propagate through network + + +## routing in internet +- autonomous system (AS): a group of networks and routers controled by a single administrative authority +- Intra-AS routing: + - routing information protocol (RIP): distance vector routing + - open shortest path first (OSPF): link state routing # routing in the internet