The document discusses several key functions and design goals of the network layer in internet architecture. It covers routing algorithms like distance vector and link state routing, as well as routing protocols like RIP. It also provides an overview of the TCP/IP protocol stack and some of its core components like IP, ICMP, TCP and UDP.

8. Calculating the Cost Network 1 Network 2 Network 3 Network 4 Network Hops 2 1 3 1 1 2 Network Hops 1 1 1 2 Network Hops 1 1 2 3 3 4 2 1 3 2 Transmitted routing table Transmitted routing table Internal routing table Router A Router B Router C

10. Routing Table Network Mask Router Hops Age Port ID 3 255 C 1 30 1 4 255 C 1 30 2 2 255 B 2 15 2 1 255 B 3 45 2

13. TCP/IP Stack 1 2 3 4 5 -7 OSI DIX Ethernet or ... ARP ICMP IP TCP UDP DNS TELNET FTP

17. Layer Protocols DNS Query DNS Reply SYN SYN/ACK ACK Caller Callee {TCP Establishment} ARP Request ARP Reply

21. Netmask Examples ? S= 128.194.100.10 M= 255.255.255.0 result 128.194.100.0 D= 128.194.200.10 M= 255.255.255.0 result 128.194.200.0 Not Equal S= 128.194.12.10 M= 255.255.255.0 result 128.194.12.0 S= 67.194.18.10 M= 255.255.240.0 result 67.194.16.0 D= 128.194.12.110 M= 255.255.255.0 result 128.194.12.0 D= 67.194.10.10 M= 255.255.240.0 result 67.194. 0.0 ?

23. IP Header 0 16 31 VERS HLEN SERVICE TYPE TOTAL LENGTH FLAGS FRAGMENT OFFSET IDENTIFICATION TIME TO LIVE PROTOCOL HEADER CHECKSUM SOURCE IP ADDRESS DESTINATION IP ADDRESS 19 8 4 IP OPTIONS (IF ANY) PADDING DATA ... 24

24. IP Packet Handling (rcv) receiving Transport Layer (TCP or UDP) Sockets IP Link {DIX Type or 802.3 DSAP} Other Physical

25. IP Packet Handling (xmit) sending Local or Non-Local ? ARP Search Routing Table Found! Missing! ICMP Error Send locally...

26. Bridges or Routers A B C D 1 2 3 4 5 Address & Netmask 1: 131.122.24.12 255.255.255.0 2: 131.122.31.253 255.255.255.0 3: 131.121.18.12 255.255.240.0 4: 131.121.24.18 255.255.240.0 5: 131.121.31.254 255.255.240.0