Networking

The TCP-IP Protocol Suite (Part 2)Carl Smith National Certificate

Parts adapted from HNC lectures by Steve Leggett – 2002/03

Developed by the American Defence Department.

Internet Protocol (IP).

Addresses both LAN's and WAN's.

IP information is sent in the form of packets.

What is IP?

IP Packet

SourceAddress

DestinationAddress Data

Checksum CRC

IP addresses fall into 3 main categories:

Class A, Class B and Class C

IP addresses consist of 4 bytes (32 bits) in the form AAA.BBB.CCC.DDD

Every interface should have an IP address.

IP Addressing

IP Addressing...

s1

s0

e0

t0

144.98.100.1

144.98.200.1

144.98.30.1

144.98.40.1

Class A network - NETWORK.HOST.HOST.HOST

1.0.0.0 through to 126.0.0.0 (16.7 million possible hosts)

Class B network - NETWORK.NETWORK.HOST.HOST

128.0.0.0 through to 191.255.0.0 (65,536 possible hosts)

Class C network - NETWORK.NETWORK.NETWORK.HOST

192.0.0.0 through to 223.255.255.0 (256 possible hosts)

Class D – start at 224.0.0.0 are used for multicasting purposes

Class E – start at 240.0.0.0 are used for research purposes

IP Addressing…

Class A address:

10.xxx.xxx.xxx

Class B addresses:

147.119.xxx.xxx, 144.98.xxx.xxx

Class C addresses:

192.2.101.xxx, 221.190.45.xxx

NB – The number of usable hosts is two less than the total number possible because all zeros or all ones cannot be used.

IP Address examples

An address using all zero bits is used to specify the actual network, whilst an address of all ones is a broadcast address destined for every user on the network.

Defined by RFC 1918 – networks and addresses 10.0.0.0 through to 10.255.255.255, 172.16.0.0 through to 172.31.255.255 and 192.168.0.0 through to 192.168.255.255

These are reserved to be used only as internally private addresses – not to connect to the Internet.

IP Addressing

Segments the network into smaller sub-networks of the whole network.

Manipulates the HOST portion of the address:

144.98.xxx.xxx

In IP router networks each router interface must have a separate subnet address.

Sub-netting

IP Addressing and Sub-netting

144.98.1.1

144.98.1.2144.98.10.1144.98.20.1

144.98.30.1

144.98.2.1

144.98.2.2

144.98.20.2

144.98.30.2

144.98.10.2

144.98.30.3

144.98.20.3

144.98.10.2

IP Subnets are defined by using a subnet mask. The mask denotes how many bits of the host portion of the address describe the subnet

144.98.subnet.host

This mask is a 32 bit Internet address with all ones in the network and subnet portion of the address.

Subnet Masks

Subnet Masks…

128 64 32 16 8 4 2 1

NETWORK NETWORK SUBNET HOST

144 98 54 2

Class 'B' Address

8 bits 8 bits 8 bits 8 bits

128 64 32 16 8 4 2 1 128 64 32 16 8 4 2 1

0 1 1 0 0 0 1 01 0 1 0 0 0 0 0 0 0 1 1 0 1 1 0 0 0 0 0 0 0 1 1

128 64 32 16 8 4 2 1

1 1 1 1 1 1 1 11 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0

255 255 255 0

255.255.255.0

8 bits used for the subnet address and 8 bits for the host address.

This means that the 8 bits in the host portion allows 254 hosts and the 8 bits in the subnet portion allows 254 subnets.

255.255.255.192

we have taken two bits of the host portion of the address and used it for the subnet portion.

Subnet Masks…

Subnet Masks…

MASK SUBNETBits

HOSTBits

SUBNETS HOSTS

255.255.255.0 8 254 254255.255.255.128 7 510 126255.255.255.192 6 1022 62255.255.255.224 5 2048 30

0 1 1 0 0 0 1 01 0 1 0 0 0 0 0 0 0 1 1 0 1 1 0 0 0 0 0 0 0 1 1

128 64 32 16 8 4 2 1

NETWORK NETWORK SUBNET HOST

144 98 54 2

Class 'B' Address

8 bits 8 bits 8 bits 8 bits

128 64 32 16 8 4 2 1 128 64 32 16 8 4 2 1 128 64 32 16 8 4 2 1

891011

Summary