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
De mi cosecha

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
CISCO systems networking academy. Cap. 11
Aplicaciones útiles de ruteo estático:
Seguridad. Un ruteo dinámico tiende a revelar todo sobre la red, por razones de seguridad es importante esconder partes de una red. El ruteo estático permite que el administrador controlelo que puede publicarse de particiones restringidas.
Stub network. Cuando una red es accesible solo por una trayectoria, ruteo estático es suficiente. Elimina el overhead del ruteo dinámico.
Ruteo Dinámico:
Mayor Flexibilidad cuando falla un enlace.

5. Metrics
Hop number
Delay
Throughput

6. Autonomous System Exterior Routing
Why Interior and Exterior Protocols?

7. Interior and Exterior Routing
Why Interior and Exterior Protocols?

8. Autonomous System Interior Routing Interior Routing Exterior Routing

9. RIP (Routing Information Protocol)

10. RIP (Routing Information Protocol)
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.
If the metric is delay, the router can measuer using ECHO packets.
If the metric is hops, then the distance is 1.
If the metric is queue length, then the router examines its queues.

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

12. Léxico: RIP (Routing Information Protocol)
Request
Response
Solicited
Unsolicited
Update Message
TCP/IP, Douglas Comer, Pag 276.

13. Semantics: Request Response Update Message: Periodic Timer
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. Formato del Frame de un Request
Figure 13-7
Sintaxis:
Formato del Frame de un Request

15. Sintaxis: Formato del Frame de un Response8 16 24 31
Comando (1-5)
Reserved
Vesion(1)
Familia de Red 1 (For TCP/IP=2)
Debe de estar puesto a cero.
Dirección IP de la Red 1
Debe de estar puesto a cero.
Debe de estar puesto a cero.
Distancia hacia la Red 1: Hop count from the advertising router to the destination network
Comand
Request (1)
Respons (2)
Family:
For TCP/IP is 2.
Familia de Red 2
Debe de estar puesto a cero.
Dirección IP de la Red 2
Debe de estar puesto a cero.
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 msec:
Node’s distance calculation.
Send information(vector of estimates) to its neighbors.
Recieve information from its neighbors.
For each value of vector adds the calculated distance.
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
Add one hop to the hop count for each advertising destination.
Repeat the following steps for each advertised destination:
If (destination not in the routing table) // New router
Add the advertised information to the table
Else
If (next-hop field is the same)
Replace entry in the table with the advertising one
If (advertised hop count < than the one in the table)
Add it to the routing table.
Do nothing.

29. A router receive a RIP message
RIP message from C
Net2 4
Net3 8
Net6 4
Net8 3
Net9 5
Old routing table
Net1 7 A
Net2 2 C
Net6 8 F
Net8 4 E
Net9 5 F

30. A router receive a RIP message
1. RIP message from C
After increment
RIP message from C
Net2 5
Net3 9
Net6 5
Net8 4
Net9 6
Net2 4
Net3 8
Net6 4
Net8 3
Net9 5
Old routing table
Net1 7 A
Net2 2 C
Net6 8 F
Net8 4 E
Net9 5 F
Updating
Algorithm

31. A router receive a RIP message
RIP message from C
After increment
RIP message from C
Net2 5
Net3 9
Net6 5
Net8 4
Net9 6
Net2 4
Net3 8
Net6 4
Net8 3
Net9 5
Old routing table
Net1 7 A
Net2 2 C
Net6 8 F
Net8 4 E
Net9 5 F
Updating
Algorithm

32. A router receive a RIP message
RIP message from C
After increment
RIP message from C
Net2 5
Net3 9
Net6 5
Net8 4
Net9 6
Net2 4
Net3 8
Net6 4
Net8 3
Net9 5
New routing table
Old routing table
Net1 7 A
Net1 7 A
Net2 2 C
Net6 8 F
Net8 4 E
Net9 5 F
Updating
Algorithm
Rules:
Net1: No news, don’t change.

33. A router receive a RIP message
RIP message from C
After increment
RIP message from C
Net2 5
Net3 9
Net6 5
Net8 4
Net9 6
Net2 4
Net3 8
Net6 4
Net8 3
Net9 5
New routing table
Old routing table
Net1 7 A
Net2 5 C
Net1 7 A
Net2 2 C
Net6 8 F
Net8 4 E
Net9 5 F
Updating
Algorithm
Rules:
Net2: Same next hope, replace.

34. A router receive a RIP message
RIP message from C
After increment
RIP message from C
Net2 5
Net3 9
Net6 5
Net8 4
Net9 6
Net2 4
Net3 8
Net6 4
Net8 3
Net9 5
New routing table
Old routing table
Net1 7 A
Net2 5 C
Net3 9 C
Net1 7 A
Net2 2 C
Net6 8 F
Net8 4 E
Net9 5 F
Updating
Algorithm
Rules:
Net3: A new router, add.

35. A router receive a RIP message
RIP message from C
After increment
RIP message from C
Net2 5
Net3 9
Net6 5
Net8 4
Net9 6
Net2 4
Net3 8
Net6 4
Net8 3
Net9 5
New routing table
Old routing table
Net1 7 A
Net2 5 C
Net3 9 C
Net6 5 C
Net1 7 A
Net2 2 C
Net6 8 F
Net8 4 E
Net9 5 F
Updating
Algorithm
Rules:
Net6: Different next hope, new hop count smaller, replace.

36. A router recive a RIP message
RIP message from C
After increment
RIP message from C
Net2 5
Net3 9
Net6 5
Net8 4
Net9 6
Net2 4
Net3 8
Net6 4
Net8 3
Net9 5
New routing table
Old routing table
Net1 7 A
Net2 5 C
Net3 9 C
Net6 5 C
Net8 4 E
Net1 7 A
Net2 2 C
Net6 8 F
Net8 4 E
Net9 5 F
Updating
Algorithm
Rules:
Net8: Different next hope, new hop count the same, don’t change.

37. A router recive a RIP message
RIP message from C
After increment
RIP message from C
Net2 5
Net3 9
Net6 5
Net8 4
Net9 6
Net2 4
Net3 8
Net6 4
Net8 3
Net9 5
New routing table
Old routing table
Net1 7 A
Net2 5 C
Net3 9 C
Net6 5 C
Net8 4 E
Net9 5 F
Net1 7 A
Net2 2 C
Net6 8 F
Net8 4 E
Net9 5 F
Updating
Algorithm
Rules:
Net9: Different next hope, new hop count larger, don’t change.

38. Timers en RIP Sending of messages Validity of a route
(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 )
13.9

39. Problems: Slow Convergence: Instability:
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

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

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 3

47. Figure 4
5 B 6 7

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

49. Basada de grafica Figure 13-12 de Forouzan.
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 13-12 16 - 16 - Eenvia información de Net3, pero NO de Net1,

52. Figure

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

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

57. Figure

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 13-19 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

64. Figure Part 1

65. Figure Part 2

66. Figure Part 3

67. Figure
A router needs information about specific route or routes.
It is answered with a link State update packet.
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.
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
Database Description
Link State Request
Link State Update

69. Figure

70. Figure

71. Figure

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

74. Loop Prevention: Policy Routing:
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

77. Figure

78. Figure

79. Figure

80. Figure

81. Figure

82. Figure

83. Figure