1. Basic IP Protocol Natawut Nupairoj, Ph.D. Department of Computer Engineering Chulalongkorn University

2. Outline Overview. IP Address. Subnetting. IP Routing. ICMP.

3. An Internet According to TCP/IP

4. TCP vs. OSI Model

5. Network Layer IP:Internet Protocol Unreliable (best-effort) Connectionless IP datagram ICMP: Internet Control Message Protocol Request/response/error messages Ping, traceroute Encapsulated in IP datagrams. IGMP: Internet Group Management Protocol Join/leave IP multicast groups. Encapsulated in IP datagrams.

6. Transport Layer TCP Reliable (timeout/retransmission mechanism) Connection-oriented. TCP segment Telnet, rlogin, SMTP, HTTP, FTP UDP (datagram) Unreliable but low-overhead DNS, TFTP, BOOTP, SNMP Connecting thru “port” (SAP). 16-bit numbers well-known port number: HTTP(80), FTP(20), etc.

7. Port

8. IP Datagram

9. IP Address

10. IP Address Classes

11. Decimal Notation

12. IP Class Ranges

13. Network and Host Address

14. Example

15. Example: Subnet

16. Subnetting

17. Netmask

18. Basic IP Routing Hop-by-hop using routing table. Routing table entry: Destination IP address: host address - non-zero host ID network address - host ID = 0 Gateway IP address: next-hop router. directly connected.

19. Basic IP Routing Flags destination IP: host or network address gateway IP: router or direct connect Network interface should be used for transmission.

20. IP Routing Mechanism Search routing table for an entry: Matches the complete IP address (both network and host IDs). Matches the destination network ID. Default route. If found, send to the gateway IP address (either next-hop or directly connected interface). Otherwise, the datagram is undeliverable (router issues an ICMP error message).

21. Internet Control Protocols To provide support for IP. ARP RARP ICMP All data for these protocols are encapsulated in IP datagrams.

22. ICP: ARP ARP: Address Resolution Protocol To send a packet to the destination, a host must know the destination physical network address. The sender/router must convert from IP address to physical network address (ie. Ethernet address). When a host wants to find a physical address: It broadcasts an ARP request containning an IP address. The owner (or designated responder) replies with its own network address. ARP response can be cached.

23. Address Resolution Protocol

24. ICP: RARP Reverse Address Resolution Protocol. The reverse of ARP. For diskless workstation. X Terminal Other related protocols: bootp tftp

25. ICP: ICMP Internet Control Message Protocol Communicate error messages and other conditions for IP and higher layers. Message Types: Status checking: ping. Error messages: destination unreachable, network unreachable, etc. Flow control: source quench. Routing control: redirect, etc. Information retrieval: timestamp request, etc.

26. Important ICMP Messages Echo: for ping program. Destination, network, port unreachable messages: Used by the traceroute program. Time Exceeded: TTL = 0 during transit or reassembly. Also used by the traceroute program. Source quench: flow control. the receiver informs the sender that it is running out of buffer and starts dropping datagrams.