Chapter 22 Network Layer Delivery Forwarding and Routing

Chapter 22 Network Layer: Delivery, Forwarding, and Routing 1

Source routing과 Next-Hop routring 3

Autonomous System 1 Autonomous System 2 Subnet 1. 2 R 3 Subnet 2. 1 R 2 R 6 Subnet 1. 1 Subnet 1. 3 R 5 Subnet 2. 2 R 7 R 1 R 4 Subnet 1. 4 R 8 Subnet 2. 4 Subnet 2. 3 LEGEND: Interior Gateway Protocol Exterior Gateway Protocol 11

라우팅 프로토콜의 분류 Interior Gateway Protocol (IGP) Exterior Gateway Protocol (EGP) 12

IGP Routing protocol Shortest path algorithm Routing algorithm RIP IGRP Bellman-Ford algorithm Distance Vector algorithm OSPF IS-IS Dijstra algorithm Link State algorithm 13

각 라우터에 이르는 시간의 계산 B Echo 패킷 A J m sec (TAB, TAC, TAD, TAE) TB = m + TAB T C = m + T AC T D = m + T AD T E = m + T AE Ti sec C D E 15

Distance Vector Algorithm의 예 16

Updating routing table 17

Link State Packet의 구성 19

Link state routing의 예(1) Step 1: Collect the link state information from the neighboring nodes and make the link state packets. 5 B 2 A 2 2 C 3 1 3 D F 1 1 3 E Link state packets A seq# age B 2 C 5 D 2 B seq# age A 2 C 3 D 2 C seq# age A 5 B 3 D 3 E 1 F 1 D seq# age A 2 B 2 C 3 E 1 E seq# age C 1 D 1 F seq# age C 1 E 1 20

Link state routing의 예(2) Step 2: Propagate the link state information to all other nodes. n n Make the link state packet. Use the flooding. Step 3: Compute the shortest path. n n Based on the link state information, the node makes the link state database that represents the whole network topology. Compute the shortest path using the Dijkstra algorithm. 21

Link State Database 5 B 2 A 3 2 2 C 3 D 1 F 1 3 1 E Link # Cost A-B A-C A-D B-A B-C B-D C-A 2 5 2 2 3 2 5 C-B C-D C-E C-F D-A D-B D-C 3 3 1 1 2 2 3 D-E E-C E-D E-F E-C E-E 1 1 1 22