The services provided by the network layer should be independent of the subnet topology.
- 2. Computer Networks: Routing 2 Network Layer Design Goals 1. The services provided by the network layer should be independent of the subnet topology. 2. The Transport Layer should be shielded from the number, type and topology of the subnets present. 3. The network addresses available to the Transport Layer should use a uniform numbering plan (even across LANs and WANs).
- 3. Computer Networks: Routing 3 Figure 7.2 Physical layer Data link layer Physical layer Data link layer End system a Network layer Physical layer Data link layer Physical layer Data link layer Transport layer Transport layer Messages Messages Segments End system b Network service Network service Copyright ©2000 The McGraw Hill Companies Leon-Garcia & Widjaja: Communication Networks Network layer Network layer Network layer
- 4. Computer Networks: Routing 4 Application Transport Internet Network Interface Application Transport Internet Internet Network 1 Network 2 Machine A Machine B Router/Gateway Network Interface Network Interface Figure 8.3
- 5. Computer Networks: Routing 5 R R R R S S S s s s s s s s s s s R s R Backbone To internet or wide area network Organization Servers Gateway Departmental Server Figure 7.6 Copyright ©2000 The McGraw Hill Companies Leon-Garcia & Widjaja: Communication Networks Metropolitan Area Network (MAN)
- 6. Computer Networks: Routing 6 Interdomain level Intradomain level LAN level Autonomous system or domain Border routers Border routers Figure 7.7 Internet service provider Copyright ©2000 The McGraw Hill Companies Leon-Garcia & Widjaja: Communication Networks Wide Area Network (WAN)