IP and IP Addressing in Computer Network, Slides of Computer Networks

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Program Name :B.Tech

Semester :ECE 6th Sem

Course Name: Computer Network

Course Code:EC 602

Facilitator Name: Megha Dewan

IP stands for Internet Protocol

IP specifies the format of packets, also called datagrams, and the addressing scheme.

Most networks combine IP with a higher- level protocol called Transmission Control Protocol (TCP), which establishes a virtual connection between a destination and a source.

 Provide a standard means of communication between devices  Can’t communicate if speaking two different languages Therefore we have a concept called “Protocol”

 Rules and conventions explaining how something must be done  Used to describe how devices can communicate  Protocol also defines the format of Data i.e. : being exchanged. If we both utilize the same protocol then you know how to format data so I will understand it and I know how to format data so you will understand it

Delivery service of IP is minimal.

IP provides an unreliable connectionless best effort service ◦ (^) Unreliable : IP doesn’t make an attempt to recover lost packets ◦ (^) Connectionless : Each packet is handled independently

IP doesn’t make guarantees on the service ( No throughput , No delay guarantee…)

IP supports the following services^ One-to-one  (^) One-to-all  (^) One-to-several (unicast) (broadcast ) (multicast) unicast broadcast multicast

Because TCP/IP was developed earlier than the OSI 7 layer model, it doesn’t have 7 layers but only 4 layers. Application Layer Transport Layer Internet Layer Network Access Layer

End to End data transfer……

Examples : ◦ (^) TCP (Transmission Control Protocol)  (^) Connection oriented (connection established before data exchanged)  (^) Reliable delivery of data ◦ (^) UDP (User Datagram Protocol)  (^) Connectionless service  (^) Delivery is not guaranteed (unreliable)

Internet layer protocols define the rules of how to find the routers for a packet to the destination.

It only gives best effort delivery. (packets can be delayed, corrupted, lost or out of order)

Examples : ◦ (^) IP – Internet Protocol (Provide packet delivery) ◦ (^) ARP – Address Resolution Protocol (Defined the procedure of network address / mac address translation(mapping)) ◦ (^) ICMP – Internet Control Message Protocol (Defined the procedure of error message transfer)

lengt

h

bits

data (variable length, typically a TCP or UDP segment)

heade

ch recksu

m

time

to

live

32 bit source IP

address

ver

head. type

of

len

service

16-bit

identifier

flg

s

fragme

nt

offset

uppe

r

laye

r

32 bit destination IP

address

options (if

any)

IP datagram format

IP protocol

version

total

datagram

length

(bytes)

for

fragmentati

on/

reassembly

numb

er header

length

bytes

“type”

of data

max

number

remaining

hops

(decremented

at each

router)

upper layer

protocol to

deliver payload

to

e.g.

timestamp,

record route

taken,

specify list

of routers to

visit.

how much overhead?

Network Layer 4-^16

❖ ❖ ❖ 20 bytes of TCP 20 bytes of IP = 40 bytes + app layer overhead

Byte s IHL (Intern et Heade r Length ) Byte Offse t 0 4 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 Wor d Bit 0 1 2 3 4 5 6 7 8 9 Nibble Byte

Version IHL (Header Length) Type of Service (TOS) Total Length Identification IP Flags x D M Fragment Offset Time To Live (TTL) Protocol Header Checksum Source Address Destination Address IP Option (optional, not common) 1 2 3

IP Header (version 4)

Header Checksum Checksum of entire IP header Header Length Number of 32-bit words in TCP header, minimum value of 5. Multiply by 4 to get byte count. Fragment Offset Fragment offset from start of IP datagram. Measured in 8 byte ( words, 64 bits) increments. If IP datagram is fragmented, fragment size (Total Length) must be a multiple of 8 bytes. Version Version of IP Protocol. 4 and 6 are valid. This diagram represents version 4 structure only. Total Length Total length of IP datagram, or IP fragment if fragmented. Measured in Bytes. Protocol 1 ICMP 2 IGMP 6 TCP 9 IGRP 17 UDP 47 GRE 50 ESP 51 AH 57 SKIP 88 EIGRP 89 OSPF 115 L2TP IP Protocol ID. Including (but not limited to): x 0x80 reserved (evil bit) D 0x40 Do Not Fragment M 0x More Fragments follow IP Flags x D M RFC 791 Please refer to RFC 791 for the complete Internet Protocol (IP) Specification. Copyright 2004 - Matt Baxter - mjb@fatpipe.org

MAC address ◦ (^) Identifies a specific NIC in a computer on a network ◦ (^) Each MAC address is unique ◦ (^) TCP/IP networks can use MAC addresses in communication

Network devices cannot efficiently route traffic using MAC addresses because they: ◦ (^) Are not grouped logically ◦ (^) Cannot be modified ◦ (^) Do not give information about physical or logical network configuration

IP addressing ◦ (^) Devised for use on large networks

IP addresses have a hierarchical structure and do provide logical groupings ◦ (^) IP address identifies both a network and a host