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OSPF: Anatomy of an Internet Routing Protocol

by John T. Moy

February 1998

Intermediate to advanced

368 pages

10h 7m

English

Addison-Wesley Professional

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IntroductionAudienceOrganization of This BookCompanion Book: OSPF Complete ImplementationAcknowledgments
1.1. The Internet Protocol SuitePhysical LayerData-Link LayerNetwork LayerTransport LayerHigher Layers1.2. Forwarding IP DatagramsModification of ForwardingSending ICMP ErrorsAdd-OnsFinding the First-Hop Router1.2.1. IP Addresses1.2.2. A Short History of Internet Addressing1.2.3. Tunneling1.3. IPv6Differences from IPv4Further Reading
2.1. Routing TablesImplementation of Routing Tables2.2. Internet Routing Architecture2.3. Distance Vector AlgorithmsDistance Vector ConvergenceCounting to InfinityImproving Convergence2.4. Link-State AlgorithmsFurther Reading
3.1. Functional Requirements3.2. Design DecisionsLink-State versus Distance VectorLink-State BasisEncapsulationLSA FragmentationCommon Mechanisms over Disparate Link LayersBackup Designated RouterExternal Route TagHierarchical Abstraction3.3. OSPFv1: A False Start3.4. Interoperability TestingToolsProblems FoundINTEROP Demo3.5. Field TrialsFeature RequestsProblems Found3.6. On Becoming a Standard3.7. The Internet EvolvesCIDRFrame Relay SubnetsMulticastEnhanced SecurityIPv6Further Reading
4.1. An OSPF Example4.2. Link State Advertisements (LSAs)4.2.1. Identifying LSAsLS Type FieldLinks State ID FieldAdvertising Router Field4.2.2. Identifying LSA InstancesLS Sequence Number Field4.2.3. Verifying LSA ContentsLS Checksum Field4.2.4. Removing LSAs from the Distributed DatabaseLS Age Field4.2.5. Other LSA Header FieldsOptionsLength4.3. A Sample LSA: The Router-LSA4.4. The link-State Database4.5. Communicating between OSPF Routers: OSPF Packets4.6. Neighbor Discovery and Maintenance4.7. Database Synchronization4.7.1. Initial Database Synchronization4.7.2. Reliable Flooding4.7.3. Flooding Robustness4.8. Routing CalculationsFurther ReadingExercise

5.1. The IP Subnet Model5.2. Broadcast Subnets5.2.1. Neighbor Discovery and Maintenance5.2.2. Database SynchronizationDesignated Router Election5.2.3. Abstraction5.2.4. Problems5.3. NBMA Subnets5.3.1. Neighbor Discovery and Maintenance5.3.2. Database Synchronization5.3.3. Abstraction5.3.4. Problems5.4. Point-to-MultiPoint Subnets5.4.1. Neighbor Discovery and Maintenance5.4.2. Database Synchronization5.4.3. Abstraction5.4.4. ProblemsFurther ReadingExercises
6.1. OSPF Areas6.1.1. Area Organization6.1.2. Virtual Links6.2. Incorporating External Routing Information6.2.1. Interaction with Areas6.3. OSPF Area Types6.3.1. Stub Areas6.3.2. NSSAsFurther ReadingExercises
7.1. TOS-Based RoutingBackward-Compatibility Provisions7.2. Stub AreasBackward-Compatibility Provisions7.3. Demand Circuit ExtensionsThe DoNotAge BitCaveatsBackward-Compatibility Provisions7.4. NSSA AreasBackward-Compatibility Provisions7.5. Database Overflow SupportBackward-Compatibility Provisions7.6. The External-Attributes-LSABackward-Compatibility ProvisionsFurther ReadingExercises
9.1. Internet Multicast Model9.2. The Multicast Protocol StackIP Multicast Addresses9.2.1. IGMPIGMPv2IGMPv39.3. Broadcast Forwarding9.3.1. Multicast ForwardingMulticast Router Processing9.4. MBONETTL ThresholdsFurther Reading
10.1. An Extended Example10.1.1. Steady-State Forwarding BehaviorExpanding Ring Search10.1.2. Response to Change10.2. Group-Membership-LSAs10.3. MOSPF Routing Calculations10.3.1. The Multicast Forwarding Cache10.3.2. Maintaining the Multicast Forwarding Cache10.3.3. Calculating a Multicast Datagram’s Path: Details10.4. Hierarchical Multicast in MOSPF10.4.1. Advertising MOSPF Information in the Presence of Hierarchy10.4.2. Routing Calculations in Hierarchical MOSPF10.5. Backward Compatibility: Mixing with Nonmulticast RoutersRestrictions10.6. MOSPF in the MBONEFurther ReadingExercises
11.1. SNMP11.2. OSPF MIB11.3. Configuring OSPF11.3.1. Configuring Link Costs11.3.2. Configuring OSPF Areas11.3.3. Configuring Timers11.4. An Example: The Arkansas Public School Computer Network11.5. Monitoring the OSPF ProtocolSynchronization ProblemsChecking Database ContentsOther Issues11.6. Interactions with Other Routing Protocols11.6.1. OSPF/BGP InteractionUsing OSPF to Replace IBGP11.6.2. OSPF/RIP Interaction11.7. OSPF Security11.7.1. OSPF Cryptographic Authentication11.7.2. Message Verification11.7.3. Key Management11.7.4. Stronger SecurityFurther ReadingExercises
12.1. War Stories12.2. Finding Tools for Debugging Routing Problems12.3. Tool Interpretation12.4. The ping ToolHow It WorksStrong PointsWeak Points12.5. The traceroute ToolHow It WorksStrong PointsWeak Points12.6. SNMP MIBsHow It WorksStrong PointsWeak Points12.7. MIB-Based ToolsHow They WorkStrong PointsWeak Points12.8. Network AnalyzersHow They WorkStrong PointsWeak Points12.9. Protocol-Specific ToolsHow They WorkStrong PointsWeak Points12.10. Product-Specific Monitoring and TracingHow They WorkStrong PointsWeak Points12.11. Multicast TracerouteHow It WorksStrong PointsWeak PointsFurther ReadingExercises
13.1. RIPRIPv213.2. OSPF13.3. BGPIBGPBGP Path AttributesBGP Operational Issues13.4. IGRPEIGRP13.5. Integrated IS-IS13.6. Historical Protocols13.7. Interaction among Routing ProtocolsFurther Reading
14.1. Broadcast-and-Prune Protocols14.2. DVMRP14.3. MOSPF14.4. PIM Dense14.5. PIM Sparse14.6. CBT14.7. Interaction among Multicast Routing Protocols

Content preview from OSPF: Anatomy of an Internet Routing Protocol

Chapter 10. MOSPF

Continuing our discussion of multicast routing, this chapter examines a particular multicast routing protocol, the Multicast Extensions to OSPF (MOSPF). MOSPF is an extension of OSPF, allowing IP multicast routing to be introduced into an existing OSPF unicast routing domain.

MOSPF has seen considerable deployment in private internets. When a network is already running OSPF, MOSPF is probably a better choice than the more common DVMRP when introducing a multicast routing capability. Both MOSPF and DVMRP calculate source-based trees. However, unlike MOSPF’s link-state basis, DVMRP uses Distance Vector routing technology and is susceptible to all the normal convergence problems of Distance Vector algorithms (Section 2.3). MOSPF ...