ipaddr-1217448089978438-9

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TCP/IP Addressing Demystified

- Edited by Alien Coders Team

Contributed by Souvik

Official Website: http://www.aliencoders.com

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What you will learn

• How internet addressing works

• Internet Addressing

• Role played by Routing and addressing

• ARP

•

TCP/UDP• IPv6 into the picture

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• The Internet Protocol (IP) enables communications across a vast and

heterogeneous collection of networks.

• The Internet offers two basic communication services that operate on

top of IP:

•

TCP Transmission control protocol i.e reliable stream service.• UDP User datagram Protocol.

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The TCP header contains the port number of the client process and the well known

port 80 for the HTTP server process.

The IP network address are the logical address because they are defined in termsof logical topology of the routers and the end systems.

Ethernet LAN frames contains physical address that identify the physical

endpoints for the sender and the receiver.

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• The network interface layer is particularly concerned with the

protocols that are used to access the intermediate networks.

• At each gateway the network protocol is used to encapsulate the IP packet into a packet or frame of the underlying link.

• The router must determine the next hop in the route to the destinationand then encapsulate the IP packet or frame of the type of the nextnetwork or link

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IP Packet

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• Total Length : With 16 bits , the max packetlength = 65,535

• Protocol TCP =6 ; UDP =17 ; ICMP = 1

• Options : Security level , Route to be taken by the packet

• Padding : To make the header field a multiple of32 bit word.

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Network

I nternet AddressingHost

An IP address is divided into 2 parts:

a) network part 2) host part .

The part of a public IP address that identifies the network is

internationally controlled by the Network Information Center (NIC)

located in the Stanford Research Institute in California.

The part that identifies the host is controlled locally at a

network level.

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I nternet Addressing

An Internet address is four octets (i.e. 32 bits) long.

The first few bits in the network part of the address helps interpret the

address.These bits indicate the class of the address.

When a system wants to communicate over the internet they need to have a public address.

This public address has to be purchased from NIC in Stanford.

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Address classes

There are five Internet address classes. They are : Class A / B / C / D / E .

Class A addressing is used for very large networks, that is networks which willhave a large number of hosts attached to them.

For class A the MSB is 0.

Each pure class A network can support (224-2) hosts. One address each beingreserved for network address (all 0 ) and all one for broad cast.

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Class A

24 bits

Host ID

The first bit is 0 and next 7 bits called the Net ID identifies

the network . The next field contains the host ID, whichidentifies the particular host within the specified network.

In a class A address it's 24 bits long and therefore allows

for almost 17 million hosts on a network.

For example 10.200.20.5 is a class A address

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Class B

Class B addressing is used for medium-sized networks.

If the first two bits in the address are 10, it's a class B address. 14 bits for network Idsand 16 bits for host Ids allowing about 16,000 networks and 64,000 hosts for eachnetwork.

The range of first octet of class B address is 128 – 191.i.e 128.0.0.0 to 191.255.0.0

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Class C

The next address class is class C, probably the most common network class.

If the first 3 bits in the address are 110, the address is a class C address.

The net ID is 21 bits long and the host ID is 8 bits long, allowing about 21

million networks and 254 hosts per network.

The range of class C Network is 192.0.0.0 –

223.255.255.0

The 192.0.0.2555 is the broadcast address and 192.0.0.0 is the network address.

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Class D

Class D addressing is used for multicasting a number of hosts for applications

like audio and video conferencing.

Class D networks have the first 4 bits in the network part = 1110.

The first octet ranges from 224 – 239.

All the addressees from 224.0.0.0 to 239.255.255.255 can be used as multicast

address.

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All students in Internet Class!

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• A host ID that contains all 1s is meant to broadcast the

packet to all hosts specified by the network.

• If the network ID also contains all 1s the packet is

broadcast on the local network.

• A host ID that contains all 0s refers to the networkspecified by the network ID , rather than to a host.

• A source may send all 0s in the source address while trying

to find out the correct IP address. The machine is thenidentified by its MAC address.

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• These are the IP address ranges reserved for private

networks within organizations.

• These addresses will not be allocated by NIC as public IP

address for the internet.

• There is no problem of clash because when a packet goes

outside the organization the local IP address gets translated

into into the public IP address purchased by the

organizations.

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Private Addressing

– Class A:

• 10.0.0.0 to 10.255.255.255---- 1 Class A network

– Class B:• 172.16.0.0 to 172.31.255.255 ---- 16 contiguous Class B

networks

– Class C:

• 192.168.0.0 to 192.168.255.255--- 255 contiguous Class Cnetworks

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• These are IP address ranges reserved for private networks

within organizations.

• These addresses will not be allocated by NIC as public IP

addresses for the Internet.

•There is no problem of clash because when a packet goesoutside the organization the local IP address gets translated

into the public IP address purchased by the organization.

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Reserved and Available IP

Addresses

Class Address or Range Status

A 0.0.0.0

1.0.0.0 through 126.0.0.0

127.0.0.0

Reserved

Available

Reserved

B 128.0.0.0128.1.0.0 through 191.254.0.0

191.255.0.0

Reserved Available

Reserved

C 192.0.0.0

192.0.1.0 through 223.255.254

223.255.255.0

Reserved

Available

Reserved

D 224.0.0.0 through

239.255.255.255

Multicast group

addresses

E 240.0.0.0 through

255.255.255.254

255.255.255.255

Reserved

Broadcast

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• Subnet Addressing : To add another

hierarchical level called the subnet .

• The beauty of the subnet addressing scheme is

that it is oblivious to the network outside the

organization.

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• An organization has many LANs , each consisting of no more than 100

hosts.

• 7 bits for for host identification in a sub network and other 9 bits areused for identifying the subnetwork.

• Packet with destination IP 150.100. 12.176 arrives

• The subnet mask used is 11111111 11111111 11111111 10000000 =

255.255.255.128

• The router performs the AND between the subnet mask and the IP and

the subnet number becomes 10010110 01100100 00001100 10000000: 150.100.12.128

This number is used to forward the packet to the correct subnetwork.

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I P Address Classes Exercise

Address Class Network Host

10.2.1.1

128.63.2.100

201.222.5.64

192.6.141.2

130.113.64.16

256.241.201.10

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IP Address Classes Exercise

Answers

Address Class Network Host

10.2.1.1

128.63.2.100

201.222.5.64

192.6.141.2

130.113.64.16

256.241.201.10

A

B

C

C

B

Nonexistent

10.0.0.0

128.63.0.0

201.222.5.0

192.6.141.0

130.113.0.0

0.2.1.1

0.0.2.100

0.0.0.64

0.0.0.2

0.0.64.16

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Subnet Mask

172 16 0 0

255 255 0 0

255 255 255 0

IP

Address

DefaultSubnet

Mask

8-bit

Subnet

Mask

Network Host

Network Host

Network Subnet Host

Also written as “/16” where 16 represents the number of 1s

in the mask.

Also written as “/24” where 24 represents the number of 1s

in the mask.

11111111 11111111 00000000 00000000

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Decimal Equivalents of Bit

Patterns

1 0 0 0 0 0 0 0 = 128

1 1 0 0 0 0 0 0 = 192

1 1 1 0 0 0 0 0 = 224

1 1 1 1 0 0 0 0 = 240

1 1 1 1 1 0 0 0 = 248

1 1 1 1 1 1 0 0 = 252

1 1 1 1 1 1 1 0 = 254

1 1 1 1 1 1 1 1 = 255

128 64 32 16 8 4 2 1

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16

Network Host

172 0 0

10101100

11111111

10101100

00010000

11111111

00010000

00000000

00000000

10100000

00000000

00000000

•Subnets not in use — the default

00000010

Subnet Mask without Subnets

172.16.2.160

255.255.0.0

Network

Number

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• Network number is extended by eight bits

Subnet Mask with Subnets

16

Network Host

172.16.2.160

255.255.255.0

172 2 0

10101100

11111111

10101100

00010000

11111111

00010000

11111111

00000010

10100000

00000000

00000000

00000010

Subnet

SubnetAddress

1 2 8

1 9 2

2 2 4

2 4 0

2 4 8

2 5 2

2 5 4

2 5 5

S b t M k ith S b t

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Subnet Mask with Subnets

(cont.)

Network Host

172.16.2.160

255.255.255.192

10101100

11111111

10101100

00010000

11111111

00010000

11111111

00000010

10100000

11000000

10000000

00000010

Subnet

•

Network number extended by ten bits

16172 2 128

SubnetAddress

1 2 8

1 9 2

2 2 4

2 4 0

2 4 8

2 5 2

2 5 4

2 5 5

1 2 8

1 9 2

2 2 4

2 4 0

2 4 8

2 5 2

2 5 4

2 5 5

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Subnet Mask Exercise

Address Subnet Mask Class Subnet

172.16.2.10

10.6.24.20

10.30.36.12

255.255.255.0

255.255.240.0

255.255.255.0

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Subnet Mask Exercise Answers

Address Subnet Mask Class Subnet

172.16.2.10

10.6.24.20

10.30.36.12

255.255.255.0

255.255.240.0

255.255.255.0

B

A

A

172.16.2.0

10.6.16.0

10.30.36.0

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Broadcast Addresses

172.16.1.0

172.16.2.0

172.16.3.0

172.16.4.0

172.16.3.255(Directed broadcast)

255.255.255.255(Local network broadcast)

X

172.16.255.255(All subnets broadcast)

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Addressing Summary Example

16172 2 160

10101100 00010000 1010000000000010 Host

Mask

Subnet

Broadcast

Last

First

172.16.2.160

255.255.255.192

4

1

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10101100

11111111

00010000

11111111 11111111

10100000

11000000

00000010 Host

Mask

Subnet

Broadcast

Last

First

172.16.2.160

255.255.255.192

1

2

3

7

16172 2 160

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10101100

11111111

00010000

11111111 11111111

10100000

11000000

10000000

00000010 Host

Mask

Subnet

Broadcast

Last

First

172.16.2.160

255.255.255.192

1

2

3

4

16172 2 160

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10101100

11111111

00010000

11111111 11111111

10100000

11000000

10000000

00000010

10111111

Host

Mask

Subnet

Broadcast

Last

First

172.16.2.160

255.255.255.192

1

2

3

4

5

6

16172 2 160

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10101100

11111111

00010000

11111111 11111111

10100000

11000000

10000000

00000010

10111111

10000001

Host

Mask

Subnet

Broadcast

Last

First

172.16.2.160

255.255.255.192

1

2

3

4

5

6

16172 2 160

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10101100

11111111

00010000

11111111 11111111

10100000

11000000

10000000

00000010

10111111

10000001

10111110

Host

Mask

Subnet

Broadcast

Last

First

172.16.2.160

255.255.255.192

1

2

3

4

5

6

7

16172 2 160

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10101100

11111111

10101100

00010000

11111111

00010000

11111111

00000010

10100000

11000000

10000000

00000010

10101100 00010000 00000010 10111111

10101100 00010000 00000010 10000001

10101100 00010000 00000010 10111110

Host

Mask

Subnet

Broadcast

Last

First

172.16.2.160

255.255.255.192

1

2

3

4

5

6

7

8

16172 2 160

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Routing Demonstration

ARP

192.168.89.20

192.168.89.40

192.168.88.20

192.168.88.40

192.168.89.2

192.168.88.2

192.168.90.2

192.168.90.3

192.168.91.3

192.168.91.4

Router BRouter C

Router A

Layer 2

Layer 2

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Routing done by Host

Network

Destination

Netmask Gateway Interface

0.0.0.0 0.0.0.0 192.168.88.2 192.168.88.40

192.168.88.0 255.255.255.0 192.168.88.4

0

192.168.88.40

192.168.88.40 255.255.255.25

5

127.0.0.1 127.0.0.1

Let assume IP packet received by network layer of

host have destination IP 192.168.88.20 and source IP: 192.168.88.40

192.168.88.20

AND

255.255.255.255

192.168.88.20

192.168.88.20

AND

255.255.255.0

192.168.88.0

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Routing done by Host NetworkDestination


0.0.0.0 0.0.0.0 192.168.88.2 192.168.88.40

192.168.88.0 255.255.255.0 192.168.88.4

0

192.168.88.40

192.168.88.40 255.255.255.25

5

127.0.0.1 127.0.0.1

Let assume IP packet received by network layer of

host have destination IP 192.168.89.4 and source IP: 192.168.88.40

192.168.89.4

AND

255.255.255.255

192.168.89.4

192.168.89.4

AND

255.255.255.0

192.168.89.0

192.168.89.4

AND

0.0.0.0

0.0.0.0

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NetworkDestination


0.0.0.0 0.0.0.0 192.168.90.3 192.168.90.2

192.168.88.0 255.255.255.

0

192.168.88.2 192.168.88.2

192.168.89.0 255.255.255.

0

192.168.89.2 192.168.89.2

192.168.90.0 255.255.255.

0

192.168.90.2 192.168.90.2

192.168.91.0 255.255.255.0

192.168.90.3 192.168.90.2

Let assume IP packet received by layer 3

have destination IP 192.168.89.4 and source IP: 192.168.88.40

192.168.89.4

AND

255.255.255.0

192.168.89.0

Routing Done Router A

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NetworkDestination


0.0.0.0 0.0.0.0 192.168.91.4 192.168.91.3

192.168.88.0 255.255.255.0 192.168.90.2 192.168.90.3

192.168.89.0 255.255.255.0 192.168.90.2 192.168.90.3192.168.90.0 255.255.255.0 192.168.90.3 192.168.90.3

192.168.91.0 255.255.255.0 192.168.91.3 192.168.91.3

Routing Done by Router B

Let assume IP packet received by Router A

have destination IP 192.168.92.5 and source IP: 192.168.88.40

192.168.92.5

AND

255.255.255.0

192.168.92.0

192.168.92.5

AND

0.0.0.0

0.0.0.0

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Dynamic Routing

Routing Protocol

Interior Gateway Protocol Exterior Gateway Protocol

Open Shortest Path First Routing Information Protocol

Border Gateway Protocol

Dijkstra Algorithm Bellman Ford Algorithm

Link State Protocol Distance Vector Protocol

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Address Resolution Protocol• The address resolution protocol (ARP) is used when

one host wants to get the physical address of

another host on the same network.

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Address Resolution Protocol

Ignored

Ignored

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Address Resolution Protocol

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Address Resolution

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Fragmentation and Reassembly

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IPv6

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USER DATAGRAM PROTOCOL

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