1. Network Layer

2. application transport network link physical message segment packet frame signal Network Architecture

3. Source Destination Transport packet from SOURCE to DESTINATION through intermediate ROUTERS. ROUTING: determine a path from source to destination & route packets along path. ADDRESSING: uniquely identify each node in network SERVICE: bandwidth, delay, errors, ordering, congestion Network Layer Goals

4. Data Flow Across Layers All hosts & routers have a network layer HostA HostB HostC HostD Router

5. Implementing Protocol on Data Layer accepts data from above Layer adds NEW header information Layer passes NEW data to layer below

6. Switchboard Operator

7. Virtual Circuit Service Model One path, dedicated resources, consistent, expensive, fragile

8. Origins of Internet

9. Packet Switching Service Model Many paths, no dedicated resources, inconsistent, inexpensive, robust

10. Dijkstra’s Algorithm Example I StepND(B),P(B)D(C),P(C)D(D), P(D)D(E),P(E)D(F), P(F) 0 1 2 3 4 5 START FINISH A -> F

11. Dijkstra’s Algorithm Example II StepND(B),P(B)D(C),P(C)D(D),P(D)D(E),P(E)D(F),P(F)D(G),P(G)D(H),P(H)D(I),P(I) 0 1 2 3 4 5 6 7 9 START FINISH A -> H

12. Dijkstra’s Algorithm Example III StepND(B),P(B)D(C),P(C)D(D),P(D)D(E),P(E)D(F),P(F) 0 1 2 3 4 5 6 7 9 B A C D E F

13. IP Addressing

14. Six IP Networks e-mail server e-mail client

15. IP Packet Format

16. IP Raw Bytes version: header length: service type: total packet length: identifier: flags (3 bits): fragment offset (13 bits): time to live: upper layer protocol: checksum: source ip: destination ip:

17. Ethereal Analysis

18. netstat –r Analysis Microsoft Windows XP [Version 5.1.2600] (C) Copyright 1985-2001 Microsoft Corp. C:\Documents and Settings\bdugan>netstat -r Route Table =========================================================================== Interface List 0x1........................... MS TCP Loopback interface 0x2...00 08 74 47 a1 7b...... 3Com 3C920 Integrated Fast Ethernet Controller ( 3C905C-TX Compatible) - Eacfilt Miniport 0x3...44 45 53 54 42 00...... Nortel IPSECSHM Adapter - Eacfilt Miniport =========================================================================== Active Routes: Network Destination Netmask Gateway Interface Metric 0.0.0.0 0.0.0.0 192.168.0.1 192.168.0.4 1 127.0.0.0 255.0.0.0 127.0.0.1 127.0.0.1 1 192.168.0.0 255.255.255.0 192.168.0.4 192.168.0.4 1 192.168.0.4 255.255.255.255 127.0.0.1 127.0.0.1 1 192.168.0.255 255.255.255.255 192.168.0.4 192.168.0.4 1 224.0.0.0 240.0.0.0 192.168.0.4 192.168.0.4 1 255.255.255.255 255.255.255.255 192.168.0.4 192.168.0.4 1 255.255.255.255 255.255.255.255 192.168.0.4 3 1 Default Gateway: 192.168.0.1 =========================================================================== Persistent Routes: None C:\Documents and Settings\bdugan>

19. Solve OSPF Scalability Problem