University:
York University
Course:
AP/ITEC 1610 | Introduction to Computer Programming
Academic year:

2023
Views:

355

Pages:

3
Author:

Nick T.

Scalable Routing Aggregate routers into regions known as autonomous systems (AS) or 'domains'. Intra AS/Domain All within must follow same protocol Has a 'gateway' router Inter-AS/Domain Amongst domains Gateways perform inter-AS routing Forwarding Table Configured by inter/intra routing algorithms Intra: Determine entries for destinations in AS Inter: What's reachable through a given domain Propagate this info to all routers in ASx Open Shortest Path First (OSPF) Each router floods link-state advertisement to all other routers in entire AS Each router has full topology, uses Dijkstra's to compute forwarding table Hierarchical OSPF Two levels: local area and backbone •Boundary router: connects to other Ases backbone Area burder router X X Summarize distances to destinations in own area, advertise in backbone X X Area I X Area 2 →local router: compute routing witharea internal routers BORDER GATEWAY PROTOCOL "give that holds the intenet together* Allows subnets to advertise its existence and the destinations it can reach eBGP: obtain subnet reachability into from other Ases ¡ BGP: propogate reachability info to all AS-intermal routers BGP session: routers exchange messages over semi-permanent TCP connection A path vector protocol Hot potato routing: try to get packet out network with as little cost a possible Advertized BGP Path prefix + attributes. dest advertised Z important attributes 1. AS-PATH: list of Ases through which prefix advert has passed 2. NEXT-HOP: indicates specific internal-As router to next-hop AS Policy-Based Routing •reject or accept advect based on policy • doldo not advertise based on policy Intra-AS routing Inter-AS routing Policy Control over how its truftic routed. Who routes through Single admin policy less of an issue Scale Focus on hierarchical Scaling Performance Can focus on performere Policy dominates over performance