IP - The Internet Protocol

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IP - The Internet Protocol

Magda El Zarki Dept. of CS UC Irvine

Email: elzarki@uci.edu

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Overview

IP (Internet Protocol) is a Network Layer Protocol.

Several versions ? most popular (IPv4). It is specified in RFC 891.

Gaining popularity is IPv6 due to increased addressing space and security handling.

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IP and the Internet Architecture

ICMP ARP

TCP

IP

Network Access

Media

UDP

Transport Layer

IGMP

Network Layer

Link Layer

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IP: The waist of the hourglass

IP is the waist of the hourglass of the Internet protocol architecture

Multiple higher-layer protocols

Multiple lower-layer protocols

Only one protocol at the network layer.

Applications HTTP FTP SMTP

TCP UDP

IP

Data link layer protocols

Physical layer protocols

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The Internet protocol

IP is the highest layer protocol which is implemented at BOTH routers and hosts

Application

Application protocol

Application

TCP

TCP protocol

TCP

IP

IP protocol

IP

IP protocol

IP

IP protocol

Data Link

Data Link

Data Link

Data Link

Data Link

Data Link

Data Link

Data Link

Host

Router

Router

IP

Network Access

Host

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IP Service

Delivery service of IP is minimal IP provide provides an unreliable connectionless best effort service (also

called:ldatagram service").

Unreliable: IP does not make an attempt to recover lost packets Connectionless: Each packet (ldatagramz) is handled

independently. IP is not aware that packets between hosts may be sent in a logical sequence Best effort: IP does not make guarantees on the service (no throughput guarantee, no delay guarantee,...) Consequences:

? Higher layer protocols have to deal with losses or with duplicate packets

? Packets may be delivered out-of-sequence

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IP Service

IP supports the following services:

one-to-one

(unicast)

one-to-all

(broadcast)

one-to-several

(multicast)

unicast

broadcast

multicast

IP multicast also supports a many-to-many service. IP multicast requires support of other protocols (IGMP, multicast routing)

IP Datagram Format

bit # 0

78

15 16

version

header length

DS

Identification

ECN

0

DM FF

time-to-live (TTL)

protocol

23 24 total length (in bytes)

Fragment offset header checksum

source IP address

destination IP address

options (0 to 40 bytes)

payload

4 bytes

20 bytes Header Size < 24 x 4 bytes = 60 bytes

20 bytes Total Length < 216 bytes = 65536 bytes

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