Network Layer Chapter 5 CN5E by Tanenbaum &

Transcript:Network Layer Chapter 5 CN5E by Tanenbaum &:
Network Layer Chapter 5 CN5E by Tanenbaum & Wetherall, © Pearson Education-Prentice Hall and D. Wetherall, 2011 Design Issues Routing Algorithms Congestion Control Quality of Service Internetworking Network Layer of the Internet Revised: August 2011 The Network Layer CN5E by Tanenbaum & Wetherall, © Pearson Education-Prentice Hall and D. Wetherall, 2011 Responsible for delivering packets between endpoints over multiple links TUNALI Computer Networks 1 3 Network Layer Functionality Getting packets from the source all the way to the destination Lowest layer that deals with end-to-end transmission Must know the topology of the physical network Design Issues Store-and-forward packet switching » Services Provided to the Transport Layer Connectionless service – datagrams » Connection-oriented service – virtual circuits » Comparison of virtual-circuits and datagrams » CN5E by Tanenbaum & Wetherall, © Pearson Education-Prentice Hall and D. Wetherall, 2011 Store-and-Forward Packet Switching CN5E by Tanenbaum & Wetherall, © Pearson Education-Prentice Hall and D. Wetherall, 2011 Hosts send packets into the network; packets are forwarded by routers TUNALI Computer Networks 1 6 Services Provided to the Transport Layer Frequently, network layer is the interface between the carrier and the customer Services should be independent of the router technology Transport layer should be shielded from the topology of the routers present Network Layer addressing should be uniform TUNALI Computer Networks 1 7 Unreliable and connectionless Just two primitives SEND PACKET RECEIVE PACKET The complexity is in the transport layer (hosts) Connectionless Service – Datagrams Packet is forwarded using destination address inside it Different packets may take different paths CN5E by Tanenbaum & Wetherall, © Pearson Education-Prentice Hall and D. Wetherall, 2011 TUNALI Computer Networks 1 9 Connection-Oriented Service Properties Set up a connection to receiver Negotiate parameters Packets are guaranteed to be delivered in sequence Flow control provided Complexity is in the network layer Connection-Oriented – Virtual Circuits Packet is forwarded along a virtual circuit using tag inside it Virtual circuit (VC) is set up ahead of time CN5E by Tanenbaum & Wetherall, © Pearson Education-Prentice Hall and D. Wetherall, 2011 TUNALI Computer Networks 1 11 Internal Organization of Network Layer Virtual circuits No need to choose a route for each packet Datagram No routes are worked out in advance Note that the type of services provided to transport layer and internal organization of the network are different concepts E.g. Network Layer may provide a connection-oriented service to transport layer even when it internally uses