Basic IP Protocol Natawut Nupairoj, Ph.D. Department of

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

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

An Internet According to TCP/IP

TCP vs. OSI Model

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

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

Port

IP Datagram

IP Address

IP Address Classes

Decimal Notation

IP Class Ranges

Network and Host Address

Example

Example: Subnet

Subnetting

Netmask

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.

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

IP Routing Mechanism Search routing table for an entry: Matches the complete IP address (both network and host I Ds). 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 iss ues an ICMP error message).

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

ICP: ARP ARP: Address Resolution Protocol To send a packet to the destination, a host must kno w the destination physical network address. The sender/router must convert from IP address to p hysical 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 n etwork address. ARP response can be cached.

Address Resolution Protocol

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

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.

Important ICMP Messages Echo: Destination, network, port unreachable messages: Used by the traceroute program. Time Exceeded: for ping program. 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 a nd starts dropping datagrams.