12-07-2013, 04:55 PM
Routing
Routing.ppt (Size: 1.05 MB / Downloads: 56)
Routing Protocol
Used to change the routing table according to various routing information
Specify detail of communication between routers
Specify information changed in each communication,
Network reachability
Network state
Metric
Metric
A measure of how good a particular route
Hop count, bandwidth, delay, load, reliability, …
Each routing protocol may use different metric and exchange different information
Category of Routing Protocols – by AS
AS-AS communication
Communications between routers in different AS
Interdomain routing protocols
Exterior gateway protocols (EGP)
Ex:
BGP (Border Gateway Protocol)
Inside AS communication
Communication between routers in the same AS
Intradomain routing protocols
Interior gateway protocols (IGP)
Ex:
RIP (Routing Information Protocol)
IGRP (Interior Gateway Routing Protocol)
OSPF (Open Shortest Path First Protocol)
RIP Operation
routed – RIP routing daemon
Operated in UDP port 520
Operation
Initialization
Probe each interface
send a request packet out each interface, asking for other router’s complete routing table
Request received
Send the entire routing table to the requestor
Response received
Add, modify, delete to update routing table
Regular routing updates
Router sends out their routing table to every neighbor every 30 minutes
Triggered updates
Whenever a route entry’s metric change, send out those changed part routing table