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Cap. 13 Forouzan. Chapter 13 Routing Protocols (RIP, OSPF, BGP)

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Presentation on theme: "Cap. 13 Forouzan. Chapter 13 Routing Protocols (RIP, OSPF, BGP)"— Presentation transcript:

1 Cap. 13 Forouzan

2 Chapter 13 Routing Protocols (RIP, OSPF, BGP)

3 Servicios:  Crear o Actualizar una tabla de ruteo basado en la trayectoria de mínimo atraso entre el fuente y el destino.  Conociendo totalmente a la red.  Basándome en un conocimiento Parcial de la red

4 Tipos de Protocolos de Ruteo  Static:  A parameter is minimized outline; the router is manually configured given the result of the minimization process.  Protocols:  1-MD + backtracking  n-MD + backtracking (p.e. bifurcación)  Flooding  Flow based  Dynamic (Adaptable)  Centralized:  All information is sent to a RCC (Routing Center Control) node.  Aislado: Cada nodo colecta informacion SIN intercambiar mensajes.  Papa caliente: en la fila mas corta  Distributed: Each node collect information to send to the others.  Vector de distancias (Bellman-Ford distribuido o Ford-Fulkerson)  Estado-del-enlace  Static:  A parameter is minimized outline; the router is manually configured given the result of the minimization process.  Protocols:  1-MD + backtracking  n-MD + backtracking (p.e. bifurcación)  Flooding  Flow based  Dynamic (Adaptable)  Centralized:  All information is sent to a RCC (Routing Center Control) node.  Aislado: Cada nodo colecta informacion SIN intercambiar mensajes.  Papa caliente: en la fila mas corta  Distributed: Each node collect information to send to the others.  Vector de distancias (Bellman-Ford distribuido o Ford-Fulkerson)  Estado-del-enlace

5 Metrics  Hop number  Delay  Throughput

6 Autonomous System Exterior Routing

7 Interior and Exterior Routing

8 Autonomous System Interior Routing Exterior Routing

9 RIP (Routing Information Protocol)

10  It is a vector distance algorithm which uses the Bellman-Ford Algorithm to calculate the routing tables to be used inside an AS.  Hop count is used as the metric for path selection.  If the hop count is greater than 15, the packet will be discarded.  By default, routing updates are broadcast every 30 seconds.

11 Environment Enlace Datos Red Físico Transporte Sesión Presentación Aplicación Varies IP, ICMP TCP, UDP HTTP, SNMP, Telnet, ftp Varies IP,ICMP,RIP Varies IP,ICMP,RIP Varies IP,ICMP,RIP Varies IP,ICMP,RIP Varies IP,ICMP,RIP Enlace Datos Red Físico Transporte Sesión Presentación Aplicación Varies IP, ICMP TCP, UDP HTTP, SNMP, Telnet, ftp

12 Léxico: RIP (Routing Information Protocol)  Request  Response  Solicited  Unsolicited  Update Message

13 Semantics:  Request  Send for a router that just come up or by a router that some has some time-out entries.  Unicast, multicast or broadcast.  Response  Solicited:  Send only in answer to a request  Unsolicited:  Sent periodically, every 30 seconds.  Update Message: Periodic Timer  Controls the advertising of regular update messages.

14 Figure 13-7 Sintaxis: Formato del Frame de un Request Sintaxis: Formato del Frame de un Request

15 Sintaxis: Formato del Frame de un Response Comando (1-5) Reserved Vesion(1) Familia de Red 1 (For TCP/IP=2) Dirección IP de la Red Debe de estar puesto a cero. Distancia hacia la Red 1: Hop count from the advertising router to the destination network Familia de Red 2 Dirección IP de la Red 2 Debe de estar puesto a cero. … Distancia hacia la Red 2: Hop count from the advertising router to the destination network

16 Figure 13-8

17 Routing Table  Each entry in the routing table has:  destination network IP address,  shortest distance to reach the destination in hop count and  next hop (interface) to which the packet should be deliver to reach its final destination..

18 Figure 13-4

19 Figure 13-5

20 Reglas de Procedimiento: RIP (Routing Information Protocol)  Incialization.  Every T m sec : 1. Node’s distance calculation. 2. Send information(vector of estimates) to its neighbors. 3. Recieve information from its neighbors. 4. For each value of vector adds the calculated distance. 5. Updates Routing Table (RIP Updating algorithm).

21 2. Nodes sending information, 3. Neighbors receiving information

22  En realidad los nodos NO estan sincronizados, y eso hace que una grafica mas real para un tiempo t1 sea: Nota: Utiliza broadcast al enviar mensajes a sus vecinos

23  En realidad los nodos NO estan sincronizados, y eso hace que una grafica mas real para un tiempo t2 sea:

24  En realidad los nodos NO estan sincronizados, y eso hace que una grafica mas real para un tiempo t3 sea:

25  En realidad los nodos NO estan sincronizados, y eso hace que una grafica mas real para un tiempo t4 sea:

26  En realidad los nodos NO estan sincronizados, y eso hace que una grafica mas real para un tiempo t5 sea:

27  Etc.

28 5. RIP Updating algorithm Receive: a response RIP message 1. Add one hop to the hop count for each advertising destination. 2. Repeat the following steps for each advertised destination: 1. If (destination not in the routing table) // New router 1. Add the advertised information to the table 2. Else 1. If (next-hop field is the same) 1. Replace entry in the table with the advertising one 2. Else 1. If (advertised hop count < than the one in the table) 1. Add it to the routing table. 2. Else 1. Do nothing.

29 A router receive a RIP message Net24 Net38 Net64 Net83 Net95 Net17A Net22C Net68F Net84E Net95F RIP message from C Old routing table

30 A router receive a RIP message Net24 Net38 Net64 Net83 Net95 Net25 Net39 Net65 Net84 Net96 Net17A Net22C Net68F Net84E Net95F RIP message from C 1. RIP message from C After increment Old routing table Updating Algorithm

31 A router receive a RIP message Net24 Net38 Net64 Net83 Net95 Net25 Net39 Net65 Net84 Net96 Net17A Net22C Net68F Net84E Net95F Updating Algorithm RIP message from C After increment Old routing table

32 A router receive a RIP message Net24 Net38 Net64 Net83 Net95 Net25 Net39 Net65 Net84 Net96 Net17A Net22C Net68F Net84E Net95F Updating Algorithm Net17A RIP message from C After increment Old routing table New routing table Rules: Net1: No news, don’t change.

33 A router receive a RIP message Net24 Net38 Net64 Net83 Net95 Net25 Net39 Net65 Net84 Net96 Net17A Net22C Net68F Net84E Net95F Updating Algorithm Net17A Net25C RIP message from C After increment Old routing table New routing table Rules: Net2: Same next hope, replace.

34 A router receive a RIP message Net24 Net38 Net64 Net83 Net95 Net25 Net39 Net65 Net84 Net96 Net17A Net22C Net68F Net84E Net95F Updating Algorithm Net17A Net25C Net39C RIP message from C After increment Old routing table New routing table Rules: Net3: A new router, add.

35 A router receive a RIP message Net24 Net38 Net64 Net83 Net95 Net25 Net39 Net65 Net84 Net96 Net17A Net22C Net68F Net84E Net95F Updating Algorithm Net17A Net25C Net39C Net65C RIP message from C After increment Old routing table New routing table Rules: Net6: Different next hope, new hop count smaller, replace.

36 A router recive a RIP message Net24 Net38 Net64 Net83 Net95 Net25 Net39 Net65 Net84 Net96 Net17A Net22C Net68F Net84E Net95F Updating Algorithm Net17A Net25C Net39C Net65C Net84E RIP message from C After increment Old routing table New routing table Rules: Net8: Different next hope, new hop count the same, don’t change.

37 A router recive a RIP message Net24 Net38 Net64 Net83 Net95 Net25 Net39 Net65 Net84 Net96 Net17A Net22C Net68F Net84E Net95F Updating Algorithm Net17A Net25C Net39C Net65C Net84E Net95F RIP message from C After increment Old routing table New routing table Rules: Net9: Different next hope, new hop count larger, don’t change.

38 Timers en RIP Sending of messages (distance’s vector) Validity of a route (route is invalid, but the route is not still purged from the table ) Failure of a Router (after this time, finally the route is purged from the table )

39 Problems:  Slow Convergence:  Since information is on the neigbors, it shows very slow Convergece (Infinite Counting Problem: reacts faster to the good news than to the bad news).  Solution:  Limiting the number of hops (AS Diameter) a 15.  Instability:  messages can go from one router to another in a loop.  Solutions:  Triggered Update  Split Horizon  Poison Reverse

40  Tiempo esperado entes que un cambio alcance un ruteador:  Entonces, el tiempo de le toma actualizar un ruteador que está a N ruteadores, entonces

41 Figure 13-10

42 Ejemplo:  Si hay 10 enrutadores:  Suponiendo que la tecnología de red utilizada es Ethrenet, entonces la cantidad de bits transmitidos en este tiempo es:

43 Problems:  Slow Convergence:  Since information is on the neigbors, it shows very slow Convergece (Infinite Counting Problem: reacts faster to the good news than to the bad news).  Solution:  Limiting the number of hops (AS Diameter) a 15.

44 Figure 13-11

45 Problems:  Instability:  messages can go from one router to another in a loop.  Solutions:  Limiting the number of Hops, reduce the problem but do NOT eliminate it.  Triggered Update  Split Horizon  Poison Reverse

46 Figure

47 4 5 B 6 76

48 Triggered Update  If there is a change in the network, the router springs into action inmediatly by sending out its new table.

49 16 -

50 Split Horizon  If a router receive a packege from an interface, then the same update information must not be send back for the same interface.

51 Figure Eenvia información de Net3, pero NO de Net1, 16 - Eenvia información de Net1, pero NO de Net3,

52 Figure 13-13

53 Poisson Reverse  Information receive by the router is used to update the routing table and then passed out to all interfaces. However, a table entry that has come through one interface is set to a metric of 16 as it goes out through the same interface.

54 Figure 13-14

55 RIP v2  Enables RIP to receive information of an exterior routing protocol.  Authentication is added to protect message against unauthorized advertisement.  Utiliza la dirección de multicast:

56 Figure 13-15

57 Figure 13-16

58 OSPF  Interior Routing Protocol.  Divide the AS in areas (colection of networks, hosts and routers inside an AS).  Routers inside an area floods the area with routing information.  There is a special area called ¨backbone¨.  All areas inside an AS must be connected to the “backbone”.  Allow the administrator to assign cost (based on delay, maximum throughput, etc.) to each router.

59 OSPF:  Interior Routing Protocol.  Divide the AS in areas (colection of networks, hosts and routers inside an AS).  Routers inside an area floods the area with routing information.  Allow the administrator to assign cost (based on delay, maximum throughput, etc.) to each router.

60  Routers inside the Area flood the area with routing information.  At the border of an area, a special router summarize the information about the area and send it to other areas.  All the areas inside an autonomous system must be connected to the backbone. If, due to some problem, the connectivity between a backbone and an area is broken, a virtual link between routers must be created by the administration to allow continuity of the functions of the backbone.

61 Figure a. Transient link phisical representation. b. Transient link “possible” phyisical representation: Even if they are connected to the same LAN, in this case each router would had to advertise the other routers the status of the links!!! c. Transient link “convenient” logical representation: there is a special router who is a true router and a designeted router. The designated router collect the interface information attached to the LAN.

62 Graphical Representation

63 Figure 13-24

64 Figure Part 1

65 Figure Part 2

66 Figure Part 3

67 Figure Test Reacheability. First step in the link state routing. When a router in connected for first time to the network, it needs to know the the complete link state database. A router needs information about specific route or routes. It is answered with a link State update packet. All the links of the router All the links connected to a network One for each network. It sends the network masks and the metrics To which network, the border router is attached. One for each network. It sends the network masks and the metrics

68 Figure Link State Request Database Description Link State Update

69 Figure 13-33

70 Figure 13-36

71 Figure 13-41

72 BGP  The autonomous boundary routers advertise the reachability of the networks in their own autonomous systems to neighbor autonomous boundary routers.  Each router that receive a path vector message verifies that the advertised path is in agreement with its policy.  If it is, the router  updates its routing table  modifies the message (  adds its number to the path and  replaces the next routing with its own identification)  sending it to the next neighbor.

73 Figure 13-42

74  Loop Prevention:  Can be avoided using the path vector routing.  Policy Routing:  The path is not based in minmium delay or minimum number of hops, but in policies.

75 Fin

76 Figure 13-43

77 Figure 13-44

78 Figure 13-45

79 Figure 13-46

80 Figure 13-47

81 Figure 13-48

82 Figure 13-49

83 Figure 13-50


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