1. Internetworking Hussain Ali, MS hussain@ccse.kfupm.edu.sa Department of Computer Engineering King Fahd University of Petroleum and Minerals Dhahran, Saudi Arabia

2. What is Internetworking ?  Internetworking stands for  connectivity and communication between two or more networks.  dropping the “s” from Networks.

3. How is Internetworking Achieved ?  Cables and physical interfaces (physical connectivity)  Protocols, management and applications needed to support user (Internetworking)

4. Motivation for Internetworking  Overcome distance limitations and protocol differences for more effective sharing of data and resources  Productive communication between people across a single network or multiple networks  Email, newsgroups, mailing lists, live conferencing

5. Components of an Internetwork  Campus Network  Locally connected users in a building or group of buildings  Wide Area Networks (WANs)  Distant campuses connected together usually through connection providers such as the phone company  Remote Connections  Linking branch offices and mobile users to a corporate campus

6. Campus Networks  A campus is a building or group of buildings all connected into one enterprise network that consists of many local area networks.  The distinct characteristic of a campus is that the company network owns the physical wires.

7.  Campus network topology is primarily LAN technology connecting all the end systems together.  Campus networks generally use LAN technologies such as Ethernet, Token Ring, FDDI, Fast Ethernet, and ATM.

8. Wide Area Networks  WAN communication occurs between geographically separate areas.  In enterprise internetworks, WANs connect campuses together.  When a local end station wants to communicate with a remote end station, information must be sent over one or more WAN links.

9.  WAN services are provided through the following 3 primary switching technologies:  Circuit Switching  Packet Switching  Cell Switching

10. Remote Connection  Remote connections link single mobile users and branch offices to a local campus.  Typically a branch office is a small site that has few users and needs a low bandwidth WAN connection.  These small sites or single users, seldom need to remain connected 24 hours a day.  Remote connections are generally dial-up links or low bandwidth dedicated WAN links.

11. Trends in LAN/WAN Integration  Today, most of the computing power resides on the desktop, and this power is growing.  Distributed applications are increasingly bandwidth hungry.  Voice communications have increased significantly.  All of this is driving towards an integration of LANs and WANS under one roof.

12.  In the LAN, bandwidth is free and connectivity is limited only by hardware.  In the WAN, bandwidth is an excessive cost.  The existence and development of bandwidth sensitive traffic such as voice and real-time video has forced a requirement of better and more predictable LAN and WAN performance.

13. Interaction of Different Networks 1. LAN-to-LAN 2. LAN-to-WAN 3. WAN-to-WAN 4. LAN-to-WAN-to-LAN Host 802.5 LAN MR SNA WAN X.25 WAN MR B 802.3 LAN 802.4 LAN802.3 LAN Host B: Bridge MR: Multi-protocol router Host

14.  Devices that interconnect LANs are known as relays and operate at one layer of OSI model  There are four common types of relays  Repeater: at physical layer (bits)  Bridge: at data-link layer (frames)  Router: at network layer (packets)  Gateways: at transport and higher layers (protocols) Relays

15. Repeater (Hub)  Overcomes restrictions caused by single segment usage such as number of users, cable length.  Amplifies or regenerates weak signals.  Extends cable length  Can connect LANs of a similar type but which use different media.  Provides simple connection between adjacent LANs at the expense of increased network congestion

16. Use of Repeaters for a Multi- segment LAN Repeater Segment A Segment B Station Printer Station Stations File Server

17. Bridge  Interconnects two or more LANs (either similar or dissimilar) at the MAC level.  Capable of deciding whether or not to forward frame.  Creates an extended network and keeps local traffic off.  Can make minor changes to frame header.  Does not inspect or modify the network layer packets inside frames.

18. Characteristics of Bridges  Routing Tables  Filtering  Forwarding  Learning Algorithm

19.  Routing table  Contains one entry per station of network to which bridge is connected.  Is used to determine the network of destination station of a received packet.  Filtering  Is used by bridge to allow only those packets destined to the remote network.  Packets are filtered with respect to their destination and multicast addresses.

20. l Forwarding: the process of passing a packet from one network to another. l Learning: the process by which the bridge learns how to reach stations on the internetwork.

21. Operation of a LAN bridge from 802.3 to 802.4 802.3 CSMA/CD802.4 Token bus Host A LLC MAC Host B Physical MAC LLC Network Bridge 802.3Packet 802.3Packet 802.4 Packet 802.4Packet 802.4Packet 802.3 802.4 Physical Network

22. Transparent Bridges  The first IEEE 802 bridge is a transparent bridge or spanning tree bridge.  People wanted to have complete transparency: when a site with multiple LANs buys bridges designed to the IEEE standard, just plug connectors into bridges. So,  no need for hardware/software changes,  no setting of address switches,  no downloading of routing tables or parameters.

23.  A transparent bridge accepts every frame transmitted on all the LANs to which it is attached.

24. AB D C F H G E LAN 1 LAN 2 LAN 3 LAN 4 Bridge

25. l Topology can change dynamically. l There must be only one path of bridges and LANs between any two segments in the bridged LAN l Bridges must support Spanning Tree Protocol if network contains loops. l Have the advantage of being easy to install l Use only a subset of topology. l Are chosen by the CSMA/CD and token bus.

26. Source Routing Bridges  Token ring people chose the source routing bridge.  Transmitter, or source, of frame in source routing specifies which route the frame is to follow.  Every machine in the network knows, or can find, the best path to every other machine; discovery frame is used.  Sender knows whether or not the destination is on its own LAN.

27. Comparison of Bridges

28. Router  Provides a more intelligent service  makes a decision as to the best way to deliver a packet from source to destination  may fragment packets to meet packet size requirements of LANs  are slower than bridges  Permits translation between different address domains such as addresses of IEEE 802 LAN and X.25

29.  Connects dissimilar networks, provided that end-systems use a common network layer protocol, such as IP.  Unlike bridge, router receive only those packets addressed to it by either a user machine or another router.  Select the best route.  The question of who owns, operates, and maintains a router arises especially when two networks belong to independent organizations.

30. Full Router and Two Half-Routers Buffer Net 1 to internet Net 2 to internet Network 1 Network 2 internet to Net 1 internet to Net 2 Network 1 Network 2 Net 1 to internet Net 2 to internet to Net 2 internet to Net 1 Machine owned jointly by both networks Full Router: Two-Half Routers:

31. Disadvantages of Routers  Routers  are protocol-dependent devices that must understand the protocol they are forwarding.  can require a considerable amount of initial configuration.  are relatively complex devices, and generally are more expensive than bridges.

32. Advantages of Routers Routers l provide sophisticated routing, flow control, and traffic isolation l are configurable, which allows network manager to make policy based on routing decisions l allow active loops so that redundant paths are available

33. Gateway  Connects end-systems whose host protocols have varying degrees of difference  Transport gateways make a connection between two networks at the transport layer.  Application gateways connect two parts of an application in the application layer, e.g., sending email between two machines using different mail formats

34. l Connect two networks above the network layer of OSI model. l Are capable of converting data frames and network protocols into the format needed by another network. l Provide for translation services between different computer protocols.

35. Routers versus Bridges  Addressing  Routers are explicitly addressed.  Bridges are not addressed.  Availability  Routers can handle failures in links, stations, and other routers.  Bridges use only source and destination MAC address, which does not guarantee delivery of frames.

36. l Message Size »Routers can perform fragmentation on packets and thus handle different packet sizes. »Bridges cannot do fragmentation and should not forward a frame which is too big for the next LAN. l Forwarding »Routers forward a message to a specific destination. »Bridges forward a message to an outgoing network.

37. l Priority »Routers can treat packets according to priorities »Bridges treat all packets equally. l Error Rate »Network layers have error-checking algorithms that examines each received packet. »The MAC layer provides a very low undetected bit error rate.

38. l Security »Both bridges and routers provide the ability to put “security walls” around specific stations. »Routers generally provide greater security than bridges because –they can be addressed directly and –they use additional data for implementing security.

39. Brouters: Bridging Routers l Combine features of bridges and routers. l Capable of establishing a bridge between two networks as well as routing some messages from the bridge networks to other networks. l Are sometimes called (Layer 2/3) switches and are a combination of bridge/router hardware and software.

40. Network Connectivity Devices  Entry-level Hubs  Interconnect PCs in a single network segment  Simple stand-alone device that provides a starting point cost-effective connectivity for many organizations.

41. Network Connectivity Devices (contd.)  Stackable Hubs  Let you start small and grow your network at your own pace.  Are connected by flexible expansion cables, and once stacked together, function as one hub.  Manageable as one logical unit.

42. Network Connectivity Devices (contd.)  Chassis Hub  Big iron box that can contain a variety of network modules.  It has a power supply, a high speed backplane, and expansion slots for plug-in Hub modules.

43. Network Connectivity Devices (contd.)  Workgroup switches  Low-end network devices that aggregate multiple shared segments  Use switching technology  Typically deployed at the desktop level  Ethernet, Token-Ring, or ATM

44. Network Connectivity Devices (contd.)  Workgroup switches  Low-end network devices that aggregate multiple shared segments  Use switching technology.  Typically deployed at the desktop level.

45. Network Connectivity Devices (contd.)  Backbone switches  High-end network devices deployed at the core of the network.  Use switching technology.  Aggregate data from Hubs and Workgroup switches.  Typically accept various networking options.

46. Network Connectivity Devices (contd.)  Routers  Perform routing of packets among LANs.  Provide most effective way of segmenting the network.  Move data by finding the best path from the sender to the receiver.  Suitable for organizations with many large LANs.