1. 1 Networking and Internetworking Devices we need networking and internetworking devices to extend physical distance and to improve efficiency and manageability

2. 2 Introduction Many times it is necessary to connect a local area network to another local area network or to a wide area network. Local area network to local area network connections are often performed with a bridge. Local area network to wide area network connections are usually performed with a router. A third device, the switch, can be used to interconnect segments of a local area network.

3. 3 Why Interconnect? To separate / connect one corporate division with another. To connect two LANs with different protocols. To connect a LAN to the Internet. To break a LAN into segments to relieve traffic congestion. To provide a security wall between two different types of users. To connect WLAN to LAN

4. 4 Networking and Internetworking Devices Connecting devices and the OSI Model

5. 5 Repeaters operate on physical layer regenerate the original bit pattern (which may become too weak or corrupted) and put the refreshed copy back onto the link allow us to extend only the physical length of a network

6. 6 Repeaters A repeater in the OSI model

7. 7 Repeaters function of a repeater a repeater is a regenerator, not an amplifier

8. 8 Bridges operate in physical and data link layers divide a large network into smaller segments relay frames between two originally separate LANs

9. 9 Bridges A bridge in the OSI model

10. 10 Bridges contain logic that allows them to keep the traffic for each segment separate filter traffic – useful for controlling congestion and isolating problem links when a frame enters a bridge, checks address and forwards to the right segment

11. 11 Bridges Types of Bridges simple bridges – most primitive, least expensive, addresses must be entered manually for each segment multiport bridges – can connect more than one LANs

12. 12 Bridges Types of Bridges (cont) transparent bridges – build table of station addresses dynamically by checking source and destination addresses, self updating to prevent loops in the LANs connected by several bridges spanning tree algorithm and source routing is used

13. 13 Bridges Bridges can connect LANs using different protocols at the data link layer; issues considered frame format payload size data rate address bit order access method, etc

14. 14 Routers operate in physical, data link and network layers of the OSI model relay packets among multiple interconnected networks by default is a single- protocol device

15. 15 Routers routers in an internet routers act like stations on a network, have several addresses on and link to two or more networks at the same time packets received will be relayed to the adjacent network or passed them on to another router

16. 16 Gateways operate in all seven layers of the OSI

17. 17 Gateways a gateway is a protocol converter accept a packet formatted for one protocol (e.g. AppleTalk) and convert it to a packet formatted for another protocol (e.g. TCP/IP)

18. 18 Other devices Multiprotocol routers designed to route packets belonging to two or more protocols (e.g. IP, IPX, AppleTalk) single protocol versus multiprotocol routers:

19. 19 Other devices Brouters a single-protocol or multiprotocol routers that acts as a router and sometime as a bridge

20. 20 Other devices Switches provide bridging functionality with greater efficiency store-and-forward switch cut-through switch Routing Switches use network layer destination address to find the output link to which the packet should be forwarded

21. 21 Routing Algorithms common methods used to calculate the shortest path between two routers distance vector routing each router periodically shares its knowledge about the entire network with its neighbors link state routing each router shares its knowledge of its neighbor with all routers in the internetwork

22. 22 Routing Algorithms Distance Vector Routing the concept

23. 23 Routing Algorithms Distance Vector Routing (cont) routing table

24. 24 Routing Algorithms Distance Vector Routing (cont) routing table distribution

25. 25 Routing Algorithms Distance Vector Routing (cont) updating routing table for router A

26. 26 Routing Algorithms Distance Vector Routing (cont) final routing table

27. 27 Routing Algorithms Distance Vector Routing (cont) Updating algorithm 1. If the advertised destination table is not in the routing table, the routershould add the advertised information to the table 2. If the advertised destination is in the routing table, a. if the next hop field is the same, the router should replace the entry in the table with the advertised one b. if the next hop field is not the same i. if the advertised hop count is smaller than the one in the table, the router should replace the entry in the table with the new one ii. if the advertised hop count is same or larger, the router should do nothing

28. 28 Routing Algorithms Distance Vector Routing (cont) Example