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Chapter 14-16a. Internet Routing Review. Introduction. Motivation: Router performance is critical to overall performance and QoS in the Internet and private internetworks. Consider: selecting best routes (optimize delay, load) maintaining routing tables (router overhead) - PowerPoint PPT Presentation

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  • Chapter 14-16aInternet RoutingReview

    Chapter 12 TCP Traffic Control

  • Introduction Motivation: Router performance is critical to overall performance and QoS in the Internet and private internetworks. Consider:selecting best routes (optimize delay, load)maintaining routing tables (router overhead)router-generated management trafficTopics:Overview of Graph TheoryInterior Routing ProtocolsExterior Routing Protocols

    Chapter 12 TCP Traffic Control

  • Graph Theory and NetworksSize of G: |E| = 10Order of G: |V| = 6

    Chapter 12 TCP Traffic Control

  • Graph Theory and NetworksWeighted Digraph to Represent Link Costs

    Chapter 12 TCP Traffic Control

  • Spanning Trees

    Chapter 12 TCP Traffic Control

  • Link Cost DeterminationShortest-path distance approachhop counteach link has equal cost of one unitShortest-path length approacheach link has associated cost in each directionweighted digraph

    Chapter 12 TCP Traffic Control

  • Breadth-First SearchProduces a spanning tree rooted in V1Finds shortest-path distance from V1 to all V

    Chapter 12 TCP Traffic Control

  • Dijkstras Link-State AlgorithmBased on breadth-first searchRunning time order of |V|2

    Chapter 12 TCP Traffic Control

  • Bellman-Ford Distance Vector AlgorithmRunning time order of |V| x |E|

    Chapter 12 TCP Traffic Control

  • Ex: Dijkstra vs. Bellman-Ford Least-cost routing algorithms

    Chapter 12 TCP Traffic Control

  • Interior/Exterior Routing Protocols Hosth2abaCABdInterior routingwithin network (AS) AInterior routingwithin network (AS) B

    Chapter 12 TCP Traffic Control

  • Chapter 15Interior Routing Protocols

    Chapter 12 TCP Traffic Control

  • Internet Routing Example

    Chapter 12 TCP Traffic Control

  • Routing TableFixed vs. Adaptive Routing?

    Chapter 12 TCP Traffic Control

  • Routing Information Protocol (RIP)Distance Vector Algorithmtypically uses simple link delay count metricSmall networksfast and simplemax hop count = 15 (RIPv1)Adaptive updates sent approximately every 30 secondslinks are invalidated if no update in 180 secondsUses UDP transport (port 520)

    Chapter 12 TCP Traffic Control

  • RIP MessagesCommand1 for request2 for replyVersion1: RIPv1, RFC 10582: RIP-2, RFC 1723Address Family ID always 2 for IP addressesIP address non-zero network portionzero host portionCost Metric typically 1 (i.e. hop count)

    Chapter 12 TCP Traffic Control

  • Open Shortest Path First Protocol (OSPF)Link-State AlgorithmDijkstras Algorithmuses flooding to advertise, request infoPreferred for TCP/IP-based internetsscale, TOS, hierarchy of areas, etc.multiple metrics monetary cost, reliability, throughput, delay, arbitraryAdaptive routers flood with new data when a significant change occursSent as payload in IP datagram

    Chapter 12 TCP Traffic Control

  • Open Shortest Path First Protocol (Scale, Hierarchy)

    Chapter 12 TCP Traffic Control

  • OSPF MessagesVersion2: current versionType1: Hello, for discovery2: database structure3: request link-state4: update link-state5: acknowledge updateLength of messageRouter IDunique in a single areaArea IDunique to an ASInternet checksumAuthentication InfoType of authentication64 bit authentication valueOSPF Header

    Chapter 12 TCP Traffic Control

  • Chapter 16aExterior Routing Protocols

    Chapter 12 TCP Traffic Control

  • Exterior RoutingRIPOSPFBGP

    Chapter 12 TCP Traffic Control

  • Border Gateway Protocol (BGP-4)Path Vector Algorithmcost metrics not used or advertisedeach router specifies a complete path to all other nodes (e.g., from node A to node Z = ADFHKXZ)Facilitates routing based on policy instead of cost metricsuse preferred routes, providers (based on policy)avoid competitors, poor performers, etc.Adaptive peers exchange updates on demandnodes may choose not to participateUses TCP transport (port 179)

    Chapter 12 TCP Traffic Control

  • Border Gateway Protocol Example W, X, Y, A, B and C are networksPaths are specified as, for example: Path (w, y) = wACy Path (x, y) = xCyBGP routers advertise (update) only those routes that are specified by administrative policy would A advertise ABx or ACx ?

    Chapter 12 TCP Traffic Control

  • BGP MessagesCommon AttributesMarkersynchronization and authentication mechanismLength of messageTypeopen: establish a neighbor relationshipupdate: send/withdraw route informationkeepalive: acknowledge or confirm relationshipnotification: error detected

    Chapter 12 TCP Traffic Control

  • Inter-Domain Routing Protocol (IDRP)Exterior routing protocol for IPv6Uses path-vector routing algorithmISO standard, defined within OSI protocol familybut, not dependent on OSI modelcan be used with any internet protocol stack (such as TCP/IP)provides a superset of BGP-4 functionscan aggregate routing info confederationsUtilizes an underlying internet protocol (like IP) with its own handshaking mechanism to exchange routing messages

    Chapter 12 TCP Traffic Control

    Protocols and the TCP/IP SuiteChapter 2