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Cap. 13 ForouzanCap. 13 Forouzan
Chapter 13
Routing Protocols(RIP, OSPF, BGP)
Servicios: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
Tipos de Protocolos de RuteoTipos 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
MetricsMetrics
Hop number Delay Throughput
Autonomous SystemAutonomous System
Exterior Routing
Interior and Exterior RoutingInterior and Exterior Routing
Autonomous SystemAutonomous System
Interior Routing
Interior Routing
Interior Routing
Interior Routing
Exterior Routing
RIP (Routing Information Protocol)RIP (Routing Information Protocol)
RIP (Routing Information
Protocol)
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.
EnvironmentEnvironment
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
Léxico: RIP (Routing Information
Protocol)
Léxico: RIP (Routing Information
Protocol) Request Response
Solicited Unsolicited
Update Message
Semantics: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.
Figure 13-7
Sintaxis:Formato del Frame de un
Request
Sintaxis:Formato del Frame de un
Request
Sintaxis:Formato del Frame de un
Response
Sintaxis:Formato del Frame de un
ResponseComando (1-5) ReservedVesion(1)
Familia de Red 1 (For TCP/IP=2)
Dirección IP de la Red 1
0 24168 31
Debe de estar puesto a cero.
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
Familia de Red 2
Dirección IP de la Red 2
Debe de estar puesto a cero.
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
Figure 13-8
Routing TableRouting 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..
Figure 13-4
Figure 13-5
Reglas de Procedimiento: RIP (Routing Information
Protocol)
Reglas de Procedimiento: RIP (Routing Information
Protocol) Incialization. Every T msec:
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).
2. Nodes sending information,3. Neighbors receiving information
2. Nodes sending information,3. Neighbors receiving information
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
En realidad los nodos NO estan sincronizados, y eso hace que una grafica mas real para un tiempo t2 sea:
En realidad los nodos NO estan sincronizados, y eso hace que una grafica mas real para un tiempo t3 sea:
En realidad los nodos NO estan sincronizados, y eso hace que una grafica mas real para un tiempo t4 sea:
En realidad los nodos NO estan sincronizados, y eso hace que una grafica mas real para un tiempo t5 sea:
Etc.
5. RIP Updating algorithm5. RIP Updating algorithm
Receive: a response RIP message1. 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 router1. Add the advertised information to the table
2. Else1. If (next-hop field is the same)
1. Replace entry in the table with the advertising one
2. Else1. If (advertised hop count < than the one in the
table)1. Add it to the routing table.
2. Else1. Do nothing.
A router receive a RIP messageA router receive a RIP message
Net2 4Net3 8Net6 4Net8 3Net9 5
Net1 7 ANet2 2 CNet6 8 FNet8 4 ENet9 5 F
RIP message from C
Old routing table
A router receive a RIP messageA router receive a RIP message
Net2 4Net3 8Net6 4Net8 3Net9 5
Net2 5Net3 9Net6 5Net8 4Net9 6
Net1 7 ANet2 2 CNet6 8 FNet8 4 ENet9 5 F
RIP message from C
1. RIP message from C
After increment
Old routing table
Updating Algorithm
A router receive a RIP messageA router receive a RIP message
Net2 4Net3 8Net6 4Net8 3Net9 5
Net2 5Net3 9Net6 5Net8 4Net9 6
Net1 7 ANet2 2 CNet6 8 FNet8 4 ENet9 5 F
Updating Algorithm
RIP message from C
RIP message from C
After increment
Old routing table
A router receive a RIP messageA router receive a RIP message
Net2 4Net3 8Net6 4Net8 3Net9 5
Net2 5Net3 9Net6 5Net8 4Net9 6
Net1 7 ANet2 2 CNet6 8 FNet8 4 ENet9 5 F
Updating Algorithm
Net1 7 A
RIP message from C
RIP message from C
After increment
Old routing tableNew routing table
Rules:
Net1: No news, don’t change.
A router receive a RIP messageA router receive a RIP message
Net2 4Net3 8Net6 4Net8 3Net9 5
Net2 5Net3 9Net6 5Net8 4Net9 6
Net1 7 ANet2 2 CNet6 8 FNet8 4 ENet9 5 F
Updating Algorithm
Net1 7 ANet2 5 C
RIP message from C
RIP message from C
After increment
Old routing tableNew routing table
Rules:
Net2: Same next hope, replace.
A router receive a RIP messageA router receive a RIP message
Net2 4Net3 8Net6 4Net8 3Net9 5
Net2 5Net3 9Net6 5Net8 4Net9 6
Net1 7 ANet2 2 CNet6 8 FNet8 4 ENet9 5 F
Updating Algorithm
Net1 7 ANet2 5 CNet3 9 C
RIP message from C
RIP message from C
After increment
Old routing tableNew routing table
Rules:
Net3: A new router, add.
A router receive a RIP messageA router receive a RIP message
Net2 4Net3 8Net6 4Net8 3Net9 5
Net2 5Net3 9Net6 5Net8 4Net9 6
Net1 7 ANet2 2 CNet6 8 FNet8 4 ENet9 5 F
Updating Algorithm
Net1 7 ANet2 5 CNet3 9 CNet6 5 C
RIP message from C
RIP message from C
After increment
Old routing tableNew routing table
Rules:
Net6: Different next hope, new hop count smaller, replace.
A router recive a RIP messageA router recive a RIP message
Net2 4Net3 8Net6 4Net8 3Net9 5
Net2 5Net3 9Net6 5Net8 4Net9 6
Net1 7 ANet2 2 CNet6 8 FNet8 4 ENet9 5 F
Updating Algorithm
Net1 7 ANet2 5 CNet3 9 CNet6 5 CNet8 4 E
RIP message from C
RIP message from C
After increment
Old routing tableNew routing table
Rules:
Net8: Different next hope, new hop count the same, don’t change.
A router recive a RIP messageA router recive a RIP message
Net2 4Net3 8Net6 4Net8 3Net9 5
Net2 5Net3 9Net6 5Net8 4Net9 6
Net1 7 ANet2 2 CNet6 8 FNet8 4 ENet9 5 F
Updating Algorithm
Net1 7 ANet2 5 CNet3 9 CNet6 5 CNet8 4 ENet9 5 F
RIP message from C
RIP message from C
After increment
Old routing tableNew routing table
Rules:
Net9: Different next hope, new hop count larger, don’t change.
Timers en RIPTimers 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 )
Problems: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
Tiempo esperado entes que un cambio alcance un ruteador:
Entonces, el tiempo de le toma actualizar un ruteador que está a N ruteadores, entonces
sec152
}{30
===
RIPpt
ptxE
sec152
×=× Nt
NRIPpt
p
Figure 13-10
Ejemplo:Ejemplo: Si hay 10 enrutadores:
Suponiendo que la tecnología de red utilizada es Ethrenet, entonces la cantidad de bits transmitidos en este tiempo es:
sec1502
10,30
=×== Nt
p
RIPp
tN
Mbps150
Problems: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.
Figure 13-11
Problems: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
Figure 13-12
3
Figure 13-12
45 B
5 B 6
7 6
Triggered UpdateTriggered Update
If there is a change in the network, the router springs into action inmediatly by sending out its new table.
16 -
Split HorizonSplit Horizon
If a router receive a packege from an interface, then the same update information must not be send back for the same interface.
Figure 13-12
Eenvia información de Net3, pero NO de Net1,
16 - 16 -
Eenvia información de Net1, pero NO de Net3,
Figure 13-13
Poisson ReversePoisson 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.
Figure 13-14
RIP v2RIP 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: 224.0.0.9
Figure 13-15
Figure 13-16
OSPFOSPF
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.
OSPF: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.
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.
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.
Graphical RepresentationGraphical Representation
Figure 13-24
Figure 13-30-Part 1
Figure 13-30-Part 2
Figure 13-30 Part 3
Figure 13-31
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 networkOne 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
Figure 13-32
Link State Request
Database Description
Link State Update
Figure 13-33
Figure 13-36
Figure 13-41
BGPBGP
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.
Figure 13-42
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.
FinFin
Figure 13-43
Figure 13-44
Figure 13-45
Figure 13-46
Figure 13-47
Figure 13-48
Figure 13-49
Figure 13-50