Bài giảng TCP/IP - Chapter 13: Routing Protocols (RIP, OSPF, BGP)

Chapter 13Routing Protocols(RIP, OSPF, BGP)CONTENTS INTERIOR AND EXTERIOR ROUTING RIP OSPF BGPINTERIORANDEXTERIORROUTING13.1Figure 13-1Popular routing protocolsFigure 13-2Autonomous systemsRIP:RoutingInformationProtocol13.2Figure 13-3Example of updatinga routing tableFigure 13-4Initial routing tables in a small autonomous systemFigure 13-5Final routing tables for the previous figureFigure 13-6RIP message formatFigure 13-7Request messagesExample 1What is the periodic response sent by router R1 in Figure 13.8 (next slide)? Assume R1 knows about the whole autonomous system.Figure 13-8Example 1SolutionR1 can advertise three networks 144.2.7.0, 144.2.9.0, and 144.2.12.0. The periodic response (update packet) is shown in Figure 13.9 (next slide).Figure 13-9Solution to Example 1Figure 13-10RIP timersExample 2A routing table has 20 entries. It does not receive information about five routes for 200 seconds. How many timers are running at this time?SolutionThe timers are listed below: Periodic timer: 1 Expiration timer: 20 - 5 = 15 Garbage collection timer: 5Figure 13-11Slow convergenceFigure 13-12Hop countFigure 13-13InstabilityFigure 13-14Split horizonFigure 13-15Poison reverseFigure 13-16RIP-v2 FormatRIP version 2 supports CIDR.Figure 13-17AuthenticationRIP uses the services of UDP on well-known port 520.OSPF:Open ShortestPath First13.3Figure 13-18Areas in an autonomous systemFigure 13-19Types of linksFigure 13-20Point-to-point linkFigure 13-21Transient link Figure 13-22Stub linkFigure 13-23Example of an internetFigure 13-24Graphical representation of an internetFigure 13-25Types of LSAsFigure 13-26Router linkFigure 13-27Network linkFigure 13-28Summary link to networkFigure 13-29Summary link to AS boundary routerFigure 13-30External linkExample 3In Figure 13.31 (next slide), which router(s) sends out router link LSAs?Figure 13-31 Example 3 and Example 4SolutionAll routers advertise router link LSAs. R1 has two links, Net1 and Net2. R2 has one link, Net1 in this AS. R3 has two links, Net2 and Net3. Example 4In Figure 13.31, which router(s) sends out the network link LSAs?SolutionAll three network must advertise network links:Advertisement for Net1 is done by R1 because it is the only router and therefore the designated router.Advertisement for Net2 can be done by either R1, R2, or R3, depending on which one is chosen as the designated router. Advertisement for Net3 is done by R3 because it is the only router and therefore the designated router. In OSPF, all routers have the same link state database.Figure 13-32-Part 1Shortest path calculationFigure 13-32-Part 2Shortest path calculationFigure 13-32 Part 3Shortest path calculationFigure 13-33Types of OSPF packetsFigure 13-34OSPF packet headerFigure 13-35Hello packetFigure 13-36Database description packetFigure 13-37Link state request packetFigure 13-38Link state update packetFigure 13-39LSA headerFigure 13-40Router link LSAExample 5Give the router link LSA sent by router 10.24.7.9 in Figure 13.41.Figure 13-41Example 5SolutionThis router has three links: two of type 1 (point-to-point) and one of type 3 (stub network). Figure 13.42 shows the router link LSA.Figure 13-42Solution to Example 5Figure 13-43Network link advertisement formatExample 6Give the network link LSA in Figure 13.44.Figure 13-44Example 6SolutionThe network, for which the network link advertises, has three routers attached. The LSA shows the mask and the router addresses. See Figure 13.45.Note that only one of the routers, the designated router, advertises the network link. Figure 13-45Solution to Example 6Figure 13-46Summary link to network LSAFigure 13-47Summary link to AS boundary LSAFigure 13-48External link LSAFigure 13-49Link state acknowledgment packetOSPF packets are encapsulated in IP datagrams.BGP:Border GatewayProtocol13.4Figure 13-50Path vector packetsFigure 13-51Types of BGP messagesBGP supports classless addressing and CIDR.Figure 13-52BGP packet headerFigure 13-53Open messageFigure 13-54Update messageFigure 13-55Keepalive messageFigure 13-56Notification messageBGP uses the services of TCP on port 179.