CSE/EE 461 Distance Vector Routing

CSE/EE 461 Distance Vector Routing

This Time

? Focus

? How do we calculate routes for packets

? Routing is a network layer function

? Each packet is routed on the basis of its destination

? In contrast to MST where we are creating an extended LAN ? Broadcast, but to all the right places

? Routing Algorithms

? Distance Vector routing (RIP)

Application Presentation

Session Transport Network Data Link Physical

Routing and Forwarding

source dest

128.95.1.3 212.16.8.4

128.95

A

128.95.1.3

F

180.1

128.96

B

212.12.5

C

212.16.8

D

212.16.8.4

E 12

G

210.11.13

Routing and Forwarding

? Routing is the global process that all routers go through to calculate routes

? Involves global decisions ? "For this link, which networks can I get to?"

? Forwarding is local the process that each router goes through for every packet to send it on its way

? Involves local decisions ? "For this packet, which link should I use to send it out?"

? Compare to MST

Routing Table: Gives Next Hop

? The routing table at A, for example, lists at a minimum the next hops (IP address) for the different destinations

Dest

B C D E F G

Next Hop

B C C E F F

"B" == "128.96", etc

128.95

A

F

180.1

128.96

B

212.12.5

C

212.16.8

D

E 12

G

210.11.13

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