IP Protocol - Introduction

Dr. Farid Farahmand

Introduction

TDM transport networks are not sufficient for data communications

Low utilization TDM networks are being replaced by

packet/frame/cell based data communication systems

So the question is what are such communication systems and protocols?

Transport Protocol Classification

Any communication system provides its services in two basic ways

Dedicated lines (circuits) Shared lines (circuits)

In packet/frame based technologies, shared resources are categorized as

Connection oriented Multiple predefines virtual paths are established through the

same physical link (highway system) The virtual path can be

Permanent: logical circuit provisioned as the system us turned-up Switched: Logical circuit established upon request

Connectionless No predefined path exists; routing takes place based on the

source and destination nodes (airplane system)

Network Basics

The backbone or core networkConsists of switches, core routers,Gateway routers (maybe called Differently)

Edge routers are used to be connected to the core network

Data path

Ingress Edge node

Egress Edge node

Transport Layer

End-to-end delivery of the entire message. Differs from network layer that oversees end-to-end delivery of

individual packets without recognizing any relationship between them.

Addressing We have seen that in the Internet the top three OSI layers are

combined into the application layer. On the Internet, the transport layer interacts with applications. Because many applications (and application instances - -

windows) can be active at any one time, this requires an additional layer of addressing known as port addressing

Transport Layer – Port Address

Connectionless vs. Connection-Oriented

Connectionless vs. Connection-Oriented

Connectionless Services There is no error control, so

incorrect frames are simply discarded.

This is called a best try service. Commonly used for low error

rate lines. The Internet model network

layer protocol, IP, is a connectionless service.

UDP is the Internet model transport layer protocol.

Connection-oriented Services Involves negotiating a ‘link’ between

the source and destination. This link will be a virtual

connection in a switched network.

Since a single pathway is established, the acknowledgement process for error control is facilitated.

These services are considered reliable and therefore are the most frequently used.

There is no connection-oriented network layer protocol in the Internet model.

TCP is the connection-oriented transport layer protocol in the Internet model.

Functions of a Connection-Oriented Transport Protocol

Connection establishment Reliable delivery:

error control (similar to data link) sequence control; loss control; duplication control (discard duplicated)

Flow control Connection termination

Functions of a Connection-Oriented Transport Protocol

Connection Termination

Three way hand shake

Functions of a Connection-Oriented Transport Protocol

Flow control Flow control similar to that used

by the data link layer, however, the flow control is from end-to-end.

Transmission Control Protocol (TCP)

Connection oriented transport protocol that provides all the functionality defined for the transport layer in the OSI model.

Packets are called segments:-16 bits are allowed for port addresses (numbers) in both protocols (allows for up to 65536 ports!)-TCP source and destination

User Datagram Protocol (UDP)

UDP provides a connectionless service with limited error control.

No sequence numbers implies that sequence, loss and duplication control are not supported.

Packets are called datagrams:

RTP (real-time protocol) header contains field used to assist UDP in transmitting real-time traffic such as VoIP

IP Protocol

IPv4 Addresses are 32 bits wide Its header is 20 bytes at minimum Uses doted-decimal notation (e.g. 43.23.43.56)

IPv6 Provides larger address domain; addresses are 128

bits wide Multiple separate headers are supported Handles audio and video; providing high quality

paths Supports unicast, multicast, anycast

IP Header

The IP datagram contains data and IP address

The IP datagram is encapsulated in a frame with physical address

The header changes as the frame goes from one network domain to the next IP Datagram

Frame

DataIP Address

FrameAddress

IP Packet Format

+ 0 - 3 4 - 7 8 - 15 16 - 18 19 - 31

0 Version Header length Type of Service Total Length

32 Identification Flags Fragment Offset

64 Time to Live Protocol Header Checksum

96 Source Address

128 Destination Address

160 Options

192  Data

 

All numbers are in bits

IP Packet Format

+ 0 - 3 4 - 7 8 - 15 16 - 18 19 - 31

0 Version Header length Type of Service Total Length

32 Identification Flags Fragment Offset

64 Time to Live Protocol Header Checksum

96 Source Address

128 Destination Address

160 Options

192  Data

 

All numbers are in bits Internet header Length

Reliability/TH/delay

How long in seconds pkt stays in Internet

Next higher level protocol after IP

IP Packet Format - TTL

TTL (time-to-live) refers to the number of router hops (or seconds) the IP packet is allowed before it must be discarded. Each router that receives a packet subtracts

one from the count in the TTL field. When the count reaches zero, the router

detecting it discards the packet and sends an Internet Control Message Protocol (ICMP) message back to the originating host.

Encapsulated IP Packet in Ethernet Frame

MAC and Associated IP address

Ethernet Frame Carrying IP Packet

Protocol Analyzer Display: 0000 00 00 C0 A0 51 24 00 C0 93 21 88 A7 08 00 45 080010 00 5A DC 28 00 00 FF 01 88 08 C0 99 B8 01 C0 990020 B8 03 2a B4 DD …..

Encapsulated IP Packet in Ethernet Frame

Ethernet Frame Carrying IP Packet

IP starting with 45 Hex indicates IPv4 with standard length of 20 bytes

IP starting with 4F Hex indicates IPv4 with standard length of 60 bytes

Remember: 24=16; 45= 0100 0101= One Byte

An Ethernet frame containing IP information has 08 00 in its type field

99 is one byte

1001 1001

Example:

IP Addressing

Two address types Physical address (the frame has the physical address)

Embedded in the hardware (NIC, e.g., 00 00 11 00 11 33) Also called the Media Address Control (MAC) address

Logical IP datagram contains the logical IP address

To transport IP packets both physical and IP addresses must be known

ARP (address resolution protocol) and RARP (reverse) address resolution protocol are used to convert MAC to IP address and vice versa

Static address resolution Dynamic address resolution

IP Addressing

Uses doted-decimal notation A network address is divided into Netid and

Hostid IP Address classification

(number of hosts per network)Class Leading bits NetworkAddress (Netid)

Host Address (Hostid)

Class A     0     7 bit (125)*     24 bit (16,777,151,750)

Class B     10     14 bit (16,368)     16 bit (65,534)

Class C     110     21 bit (2,096,896)     8 bit (254)

Class D (multicast)     1110

Class E (reserved)     1111

* Some values are reserved!

IP Addressing Classification

Network Address Host Address

Network Address

Host Address

Network Address

Host Address

Reserved for Internet research

Multicast Address

Example of IP Addressing

Q1: Determine the network address for the following IP addresses:

1- 84.42.58.11 (84 = 54 Hex = 0101 0100) Netid=84.0.0.0 Class A Hostid=0.42.58.11

2- 144.54.67.5 (144 = 90 Hex = 1001 0000) Netid=144.62.0.0 Class B Hostid=0.0.67.5

Q2: What type of IP address classificationwill a large organization with 1000individual users in 150 dispersed buildings use? Class B

IP Routing Protocols

Routing packets requires having knowledge about the network

Partial (know your own neighbors) Full (know the entire network elements)

Retrieving network information (network discovery protocols)

RIP (routing information protocol): routing based on the least number of hops

OSPF (open shortest path first): Routing based on number of hops, link speed, congestion

Sources

Tomasi Text Book Comer Text book