Network Layer (R1)

Network Layer(R1) - CSCI 232 Computer Networks Network Layer CSCI 232 Computer Networking Network Layer George Blankenship Network Layer George

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CSCI 232 - Computer Networks Network Layer George Blankenship 1 Network Layer George Blankenship 1 CSCI 232 Computer Networking: Network Layer George Blankenship Network Layer George Blankenship 2 Review • Lower level protocols – Encode message for media – Move message across media – Move message across intermediate systems to end system • Upper level protocols – Assemble message – Process message Network Layer George Blankenship 3 Road Map Physical Desktop System Laptop computer Laser printer Tower System Desktop System Laptop computer IBM RS/60 0 DECstation Modem Modem Fax Telephone Laser printer Desktop System Desktop System IBM S/370 Router Router Transport Network
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CSCI 232 - Computer Networks Network Layer George Blankenship 2 Network Layer George Blankenship 4 Lesson Outline • Concepts – Connection Oriented/Connectionless – Routing algorithms – Addressing •IP •ICMP • Routing table management Network Layer George Blankenship 5 Internetworking • A link between networks – Routing and delivery of data between processes on different networks – Accounting services and status info • Independent of network architectures – Routing of messages across networks • Provide a defined quality of service (stability, fairness, and optimality) • Function performed in a “router” •Internetworking –Service –Routing –Addressing •IP –Network –Subnetwork –AS –ARP –Encoding –ICMP •Routing Network Layer George Blankenship 6 Service Approaches • Connection oriented network service (CONS) – Virtual circuit established before data transfer – VC crosses network – IS-IS traffic moves in VC • Connectionless network service (CLNS) – Each NPDU is independent (datagram) – No implications on lower protocols – Reliability is function of upper protocol •Internetworking –Service –Routing –Addressing •IP –Network –Subnetwork –AS –ARP –Encoding –ICMP •Routing
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CSCI 232 - Computer Networks Network Layer George Blankenship 3 Network Layer George Blankenship 7 CONS/CLNS Comparison Issue CLNS CONS Circuit setup Not needed Required Addressing Each packet contains full source and destination address Each packet contains short VC number State information Stateless State table required Routing Each packet is routed independently Route chosen at VC setup, all packets follow same route Effect of router failure None, packet in router lost VC passing through router must be rebuilt Congestion control Difficult Easy, as long as buffer space exists in VC route Network Layer George Blankenship 8 Routing Taxonomy • Non-adaptive routing (static routing) – Route is determined by separate algorithm in advance and loaded into routers (switches) – Router failure causes route computation for whole network • Adaptive routing (dynamic routing) – Route is recomputed as traffic is processed – Route computation is continuous •Internetworking –Service –Routing –Addressing •IP –Network
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This note was uploaded on 09/03/2010 for the course CS 232 taught by Professor Susan during the Summer '09 term at GWU.

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Network Layer(R1) - CSCI 232 Computer Networks Network Layer CSCI 232 Computer Networking Network Layer George Blankenship Network Layer George

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