1. TCP/IP Protocol Suite 1 Chapter 14 Upon completion you will be able to: Unicast Routing Protocols: RIP, OSPF, and BGP Distinguish between intra and interdomain routing Understand distance vector routing and RIP Understand link state routing and OSPF Understand path vector routing and BGP Objectives

2. TCP/IP Protocol Suite 2 14.1 INTRA- AND INTERDOMAIN ROUTING Routing inside an autonomous system is referred to as intradomain routing. Routing between autonomous systems is referred to as interdomain routing.

3. TCP/IP Protocol Suite 3 Figure 14.1 Autonomous systems

4. TCP/IP Protocol Suite 4 Figure 14.2 Popular routing protocols

5. TCP/IP Protocol Suite 5 14.2 DISTANCE VECTOR ROUTING In distance vector routing, the least cost route between any two nodes is the route with minimum distance. In this protocol each node maintains a vector (table) of minimum distances to every node The topics discussed in this section include: InitializationSharingUpdating When to Share Two-Node Loop Instability Three-Node Instability

6. TCP/IP Protocol Suite 6 Figure 14.3 Distance vector routing tables

7. TCP/IP Protocol Suite 7 Figure 14.4 Initialization of tables in distance vector routing

8. TCP/IP Protocol Suite 8 In distance vector routing, each node shares its routing table with its immediate neighbors periodically and when there is a change. Note:

9. TCP/IP Protocol Suite 9 Figure 14.5 Updating in distance vector routing

10. TCP/IP Protocol Suite 10 Figure 14.6 Two-node instability

11. TCP/IP Protocol Suite 11 Figure 14.7 Three-node instability

12. TCP/IP Protocol Suite 12 14.3 RIP The Routing Information Protocol (RIP) is an intradomain routing protocol used inside an autonomous system. It is a very simple protocol based on distance vector routing. The topics discussed in this section include: RIP Message Format Requests and Responses Timers in RIP RIP Version 2 Encapsulation

13. TCP/IP Protocol Suite 13 Figure 14.8 Example of a domain using RIP

14. TCP/IP Protocol Suite 14 Figure 14.9 RIP message format

15. TCP/IP Protocol Suite 15 Figure 14.10 Request messages

16. TCP/IP Protocol Suite 16 Figure 14.11 shows the update message sent from router R1 to router R2 in Figure 14.8. The message is sent out of interface 130.10.0.2. Example 1 See Next Slide The message is prepared with the combination of split horizon and poison reverse strategy in mind. Router R1 has obtained information about networks 195.2.4.0, 195.2.5.0, and 195.2.6.0 from router R2. When R1 sends an update message to R2, it replaces the actual value of the hop counts for these three networks with 16 (infinity) to prevent any confusion for R2. The figure also shows the table extracted from the message. Router R2 uses the source address of the IP datagram carrying the RIP message from R1 (130.10.02) as the next hop address.

17. TCP/IP Protocol Suite 17 Figure 14.11 Solution to Example 1

18. TCP/IP Protocol Suite 18 Figure 14.12 RIP timers

19. TCP/IP Protocol Suite 19 A routing table has 20 entries. It does not receive information about five routes for 200 s. How many timers are running at this time? Example 2 Solution The 21 timers are listed below: Periodic timer: 1 Expiration timer: 20 − 5 = 15 Garbage collection timer: 5

20. TCP/IP Protocol Suite 20 Figure 14.13 RIP version 2 format

21. TCP/IP Protocol Suite 21 Figure 14.14 Authentication

22. TCP/IP Protocol Suite 22 RIP uses the services of UDP on well-known port 520. Note:

23. TCP/IP Protocol Suite 23 14.4 LINK STATE ROUTING In link state routing, if each node in the domain has the entire topology of the domain, the node can use Dijkstra’s algorithm to build a routing table. The topics discussed in this section include: Building Routing Tables

24. TCP/IP Protocol Suite 24 Figure 14.15 Concept of link state routing

25. TCP/IP Protocol Suite 25 Figure 14.16 Link state knowledge

26. TCP/IP Protocol Suite 26 Figure 14.17 Dijkstra algorithm

27. TCP/IP Protocol Suite 27 Figure 14.18 Example of formation of shortest path tree

28. TCP/IP Protocol Suite 28 Table 14.1 Routing table for node A

29. TCP/IP Protocol Suite 29 14.5 OSPF The Open Shortest Path First (OSPF) protocol is an intradomain routing protocol based on link state routing. Its domain is also an autonomous system. The topics discussed in this section include: AreasMetric Types of Links Graphical Representation OSPF Packets Link State Update Packet Other Packets Encapsulation

30. TCP/IP Protocol Suite 30 14.5 OSPF It is based on the distributed map concept all nodes have a copy of the network map, which is regularly updated. It is based on the distributed map concept all nodes have a copy of the network map, which is regularly updated. Each node contains a routing directory database Each node contains a routing directory database This database contains information about router as well as status information's about adjacent routers. This database contains information about router as well as status information's about adjacent routers. This information is periodically broadcast to all routers in the same domain This information is periodically broadcast to all routers in the same domain It computes the shortest path to the other routers It computes the shortest path to the other routers Classification: Classification: 1. Internal gateway protocol(IGP) 1. Internal gateway protocol(IGP) 2. External gateway protocal(EGP) 2. External gateway protocal(EGP)

31. TCP/IP Protocol Suite 31 14.5 OSPF Features of OSPF: Features of OSPF: It supports multiple circuit load balancing because it can store multiple routes to a destination It supports multiple circuit load balancing because it can store multiple routes to a destination It can converge very quickly to network topology change It can converge very quickly to network topology change It supports multiple metrics It supports multiple metrics It is not susceptible to routing loops It is not susceptible to routing loops It support for variable length subnetting by including the subnet mask in the routing message It support for variable length subnetting by including the subnet mask in the routing message

32. TCP/IP Protocol Suite 32 Figure 14.19 Areas in an autonomous system

33. TCP/IP Protocol Suite 33

34. TCP/IP Protocol Suite 34 An area is identified by a 32-bit number OSPF uses four types of routers: 1. An internal router is a router will all its links connected to the networks within the same area 2. An area border router is a router that has its links connected to more than one area 3.A backbone router is router that has its links connected to the backbone 4. An autonomous system boundary router(ASBR) is a router that has its links connected to another autonomous system

35. TCP/IP Protocol Suite 35 Figure 14.26 OSPF common header

36. TCP/IP Protocol Suite 36 Version The OSPF version number. This specification documents version 2 of the protocol. Type The OSPF packet types are as follows. The format of each of these packet types is described in a succeeding section. Type Description 1 Hello 2 Database Description 3 Link State Request 4 Link State Update 5 Link State Acknowledgment Packet length The length of the protocol packet in bytes. This length includes the standard OSPF header. Router ID The Router ID of the packet's source. In OSPF, the source and destination of a routing protocol packet are the two ends of an (potential) adjacency. Area ID A 32 bit number identifying the area that this packet belongs to. All OSPF packets are associated with a single area. Most travel a single hop only. Packets travelling over a virtual link are labelled with the backbone Area ID of 0.0.0.0.

37. TCP/IP Protocol Suite 37 Checksum: The checksum field is used to detect errors in the packet. The checksum is performed on the entire packet AU Type: Identifies the authentication scheme to be used for the packet. Authentication: A 64-bit field for use by the authentication scheme. OSPF Operation: 1.OSPF send the Hello messages for discovering the neighbours and designated routers are elected in multiaccess networks 2.Adjacencies are establised and link state databases are synchronized 3.Link state advertisement are exchanged by adjacent routers to allow topological databases to be maintained and to advertise inter area and inter AS routes. The routers use the information in the database to generate routing tables

38. TCP/IP Protocol Suite 38 14.7 BGP Border Gateway Protocol (BGP) is an interdomain routing protocol using path vector routing. It first appeared in 1989 and has gone through four versions. The topics discussed in this section include: Types of Autonomous Systems Path Attributes BGP Sessions External and Internal BGP Types of Packets Packet Format Encapsulation

39. TCP/IP Protocol Suite 39 14.7 BGP BGP performs interdomain routing in Transmission-Control Protocol/Internet Protocol (TCP/IP) networks. BGP is an exterior gateway protocol (EGP), which means that it performs routing between multiple autonomous systems or domains and exchanges routing and reachability information with other BGP systems. If two routers are in different autonomous systems, they may wish to exchange routing information BGP performs 3 functional procedures 1.Neighbour acquistion – to exchange the routing info between 2 routers in diff. AS Neighbour reachability-used to maintain the relationship. Both sides needs to be assured that the other side still exists and is still engaged in the neighbour relationship. Both routers send keepalive messages to each other Network reachability – If database changes, router issues an update message that is broadcase to all other routers implementing BGP – Internal BGP and External BGP

40. TCP/IP Protocol Suite 40 Figure 14.50 Internal and external BGP sessions

41. TCP/IP Protocol Suite 41 Figure 14.51 Types of BGP messages

42. TCP/IP Protocol Suite 42 BGP Messages: Header of the all BGP messages is fixed size that identifies message type 1.Marker: It is used for authentication. The sender may insert value in this field that would be used as part of an authentication mechanism to enable the recipient to verify the identify of the sender 2. Length: This field indicates the total length of the message in octets, including the BGP header. Value of the length must be between 19 and 4096 3. Type : Type field indicates type of messages. a) OPEN b)UPDATE c) NOTIFICATION d) KEEPALIVE

43. TCP/IP Protocol Suite 43 Figure 14.52 BGP packet header

44. TCP/IP Protocol Suite 44 Figure 14.53 Open message

45. TCP/IP Protocol Suite 45 Figure 14.54 Update message

46. TCP/IP Protocol Suite 46 Advantages of BGP: 1.BGP is a very robust and scalable routing protocol 2.CIDR is used by BGP to reduce the size of the Internet routing tables 3.BGP easily solves the count-to-infinity problem Disadvantages of BGP: 1.BGP is complex 2.BGP routes to destination networks, rather than to specific hosts or routers

47. TCP/IP Protocol Suite 47 BGP supports classless addressing and CIDR. Note:

48. TCP/IP Protocol Suite 48 Figure 14.55 Keepalive message

49. TCP/IP Protocol Suite 49 Figure 14.56 Notification message

50. TCP/IP Protocol Suite 50 Table 14.3 Error codes

51. TCP/IP Protocol Suite 51 BGP uses the services of TCP on port 179. Note:

52. TCP/IP Protocol Suite 52 IPv6 Internet Protocol version 6 (IPv6) is the latest revision of the Internet Protocol (IP), the communications protocol that provides an identification and location system for computers on networks and routes traffic across the Internet. IPv6 was developed by the Internet Engineering Task Force (IETF)Internet Protocolcommunications protocolInternet Engineering Task Force Advantages of IPv6: 1.Larger address space 2.Better header format 3.Security capabilities 4.Support for resource allocation 5.New options 6.Allowance for extension

53. TCP/IP Protocol Suite 53 IPv6 TYPES: 1)Unicast - An identifier for a single interface. 2) Anycast - An identifier for a set of interfaces 3) Multicast – An identifier for a set of interfaces. A packet sent to a multicast address is delivered to all interfaces identified by that address