Internet Protocol-Data Communication and Computer Networks-Lecture Slides, Slides of Data Communication Systems and Computer Networks

Download Internet Protocol-Data Communication and Computer Networks-Lecture Slides and more Slides Data Communication Systems and Computer Networks in PDF only on Docsity!

Network layer

Internet Protocol

Need for network layer

•^

The network layer at the source

is responsible for creating a packet from the

data coming from another protocol such as transport layer protocol. 

The header of the packet contains, among other information, thelogical addresses of the source and destination. 

The network layer is responsible for checking its routing table to findthe routing information. 

If the packet is too large, the packet is fragmented.

•^

The network layer at the destination

is responsible for address verification

Destination address on the packet is the same as the address of thehost. 

If the packet is fragmented, the network layer waits until allfragments have arrived, and then reassemble them and delivers thereassembled packet to the transport layer.

•^

IPV



Is an unreliable and connectionless datagram protocol,

best effort delivery

service. 

The term best effort means that IPV4 provides no error and flow controlexcept for error detection on the header. 

If reliability is important, IPV4 must be paired with reliable protocol such asTCP/IP. 

IPV4 uses datagram approach for packet switching network; each datagramis handled independently and each datagram can fallow a

different to the

destination

•^

VER

is a 4-bit field defines the version of the IP protocol.

•^

HLEN

this 4-bit field total length of the datagram header in 4byte words.

The length of the header is variable( between 20 and 60 bytes). 

When there are no options, header length is 20 bytes. 

When the option field is at its maximum size, the value of this field is 60bytes.

-^

Services 

It is an 8 bit field, the first 3 bits are called

precedence bits.



The next 4 bits are called type of service and the last bit is not used. 

Precedence

is a 3 bit ranges from 0 to 7 , it defines the priority of

datagram that need to be discarded when there are congestion , thosedatagrams with the lowest precedence are discarded first.

TOS bits

•^

Fragmentation Offset

this field is used in fragmentation.

•^

Protocol

the 8 bit field defines a higher level protocols that uses the services of

IPv4 layer. 

In IPv4 datagram encapsulate data from the higher level layers protocolssuch as TCP,UDP,ICMP and IGMP. 

The field specify the final destination protocol to which the IPv4 datagram isdelivered.

-^

Checksum

-^

Source Address

a 32 bit field of source address

•^

Destination Address

32 bit field of destination address.



Maximum Transfer Unit (MTU)

When a datagram is encapsulated in

frame, the total size of datagram must be less than this maximum size,which is define by the restrictions imposed by the hardware and softwarein the network. ^

The maximum length of the IPv4 datagram is equal to the 65535bytes.



For our physical networks we divide a datagram to make it possible topass through these networks. this is called

fragmentation.



Fields related to the Fragmentation.

1.

Identification

16 bit field identifies a datagram originated from the

source host. the identification no helps the destination inreassembling the datagram.

2.

Flags

3 bit field, ^

First bit is reserved. ^

The second bit is called a

do not fragment bit

.

^

If its value is 1 the machine do not fragment the datagram, ^

if its value is 0 the datagram can be fragmented.

^

The third bit is called

more

fragment bit.

^

if^ the value is 1 means the datagram is not the last and there aremore segments. ^

if the value is 0, means this is the last or only fragment.

Drawbacks in IPV4 

Despite of all short term solutions , such as subnetting, classlessaddressing is still a long term problem in the Internet. 

The Internet must accommodate real time audio and videotransmission. This type of transmission requires minimum delaystrategies and reservations not provided in the IPV4. 

The Internet must accommodate encryption and authentication ofdata for some applications. No encryption or authentication isprovided by IPV4. To overcome these discrepancies IPV6 was introduced

IPng (Internetworking Protocol, next generation) Advantages 

Large address space

An IPV6 address is 128 bits, so address

space is increased by 2

96

Better header format

IPV6 uses a new header format in which

options are separated from the base header and inserted, whenneeded, between the base header and the upper layer data. 

New Options

IPV6 has new options to allow additional

functionalities. 

Allowance for extension In, IPV6 is designed to allow the extension ofthe protocol if required by new technologies. 

Support for resource allocation In IPV6, the type of service field hasbeen removed by flow label to enable the source to request specialhandling of packet. This mechanism is used to support real-time audioand video traffic. 

Support for more Security

The encryption and authentication options

in IPV6 provide confidentiality and integrity of the packet.

Format of an IPV6 datagram

Flow Label

is a 3-byte(24 bit) field that is designed to provide

special handling for a particular data flow. Payload Length

The 2-byte payload length field defines the length of

the IP datagram excluding the base header. Next header

The next header is an 8-bit field defining the header

that fallows the base header in the datagram. The next header is either one of the optional extension headers used

by IP or the header of an encapsulation packet such as UDP orTCP. Hop Limit

This 8-bit hop limit filed serves the same purpose as the

TTL field in IPV4. Source address

The source address is 16-byte (128 bit) .Internet

address that identifies the original source of the datagram. Destination address

The destination address is 16-byte (128 bit).

Internet address that identifies the original source of the datagram.

Noncongestion-controlled Traffic 

Refer to the type of delay tat expect minimum traffic. 

Discarding of traffic is not desirable 

The source does not adapt itself to congestion. Flow Label 

A sequence of packets, sent from a particular source to a particulardestination, that needs special handling by routers is called flow ofpackets. 

The combination of the source address and the value of the

flow

label

uniquely defines a flow of packets.

Each router receives a packet, it consults its flow label table to findthe corresponding entry for the flow label value defined in thepacket. It then provides the packet with the services mentioned inthe entry.

• Transition from IPV4 to IPV