Ip Addressing

IP Address

•IP address is defined at Network Layer.

•IP address are logical addresses.

•IP address are of 32 bits in length.

•Every machine in the IP network needs an IP address to communicate.

•IP addresses are allocated by IANA (Internet Assigned Number Authority)

Internet Layer

Application

Transport

Network

Network Interface

•Internet Protocol•Internet Control Message Protocol (ICMP)• Address Resolution Protocol (ARP)• Reverse Address Resolution Protocol

(RARP)

Internet Control Message Protocols

• Used for Error reporting & management purposes.

• Described in RFC 792.

• Message types include

• Destination Unreachable.

• Host Unreachable.

•Port Unreachable.

ICMP Illustration

Network y

No RouteTo Network Y

Destination Unreachable

Internet Growth

• A research network is now been the worlds largest public data network.

• Internet doubles in size every nine months.

• As the internet grows , there are two primary concerns

• IP V4 address space exhaustion.

• increase in routing table size.

IP addressing basics

•A device connected to an IP network requires an IP address to communicate (or) access the network.

•An IP address is 32 bits in length in which some bits represent Network address and other bites represent Node (or) device address.

HOST ADDRESSNETWORK ADDRESS

IP ADDRESS FORMAT

IP addressing basics•All devices connected on the same segment (subnet) will share common network prefix while their host bits will be unique.

•Host connected to different segments will have unique network addresses.

•IP addresses were commonly represented in dotted decimal format like 210.210.10.79.

•IP addresses management is co-ordinated by IANA. IP addressing details were published in RFC 1700.

•APNIC represents the Asia/Pacific region for IP address allocation & management.

•The Network-bits were currently referred as network prefix.

IP addressing illustration

192.168.1.0 192.168.2.0

192.168.1.1

192.168.1.2

192.168.2.1

E0 E1

Classful addressing

•Each network attached to the internetwork differs in the no of devices attached to a network.

•Different classes have been published to accommodate networks of different sizes. For example: IBM may have 1000’s of Host connecting to the internetwork, while a small startup company will have only 10 hosts connecting to the internetwork.

•Something like a addressing efficiency theory.

•3 different addressing classes

• Class A, Class B, Class C

Class A - IP addresses

•A class A network consists of a 7 bit network ID and 24 bit host id.

•The significant bit is 0 to indicate a class A address.

•Class A networks were also referred as /8s.

•A single class A network can support a maximum hosts 16 Million.

•Reserved host bits include all 1’s and 0’s used for broadcast and this network references.

•In decimal representation class A addresses first octet will be in the range of 1 - 126

0 Network Bits Host Bits

0 7 8 31

Special addresses

Network bits Host bits(all 1’s)

Broadcast address

Network bits Host number(all 0’s)

This network(Local)

Special Address illustration

192.168.1.0

192.168.1.1

192.168.1.2

192.168.1.3

Destination IP HELLO 192.168.1.255 ALL

Destination IP HELLO 192.168.1.255 ALL

Destination IP HELLO 192.168.1.255 ALL

• Address resolution

• service resolution

• routing protocols

Class B – IP addresses

•Uses 16 bits for Network ID and 16 bits to represent host ID.

•The first two bit values are set to 11 followed by 14 bits for network ID representation.

•Total no of hosts in a single class B network is 65,534.

•Class B addresses first octet fall in the range of 128 - 191

1 0 Network Bits Host Bits

0 1 15 16 31

Class C – IP address

0 Network Bits Host Bits

0 23 24 31

•Uses 24 bits for Network ID and 8 BITS FOR HOSTS id’S

•The first 3 bits were set to 110 followed by 21 bits to represent network Ids.

•Last 8 bits were used to represent host ID’s.

•A class C network can support a maximum hosts of 254.

•Class C address first octet fall in the range 192 - 223

Dotted Decimal Notation & IP classes

Class A 1.0.0.0 – 126.255.255.255

Class B 128.0.0.0 – 191.255.255.255

Class C 192.0.0.0 – 223.255.255.255

Class D 224.0.0.0 – 239.255.255.255

Class E 240.0.0.0 – 254

Limitations in classful addressing

•IANA has released IP addresses upon request without verifying the actual needs.

•Growth rate exhausted the IP address space.

•A standard 32 bit ip address provided only 2^32 = 4,294,967,296 addresses, a slightly larger address is needed to sustain the growth .

•Lack of specific network classes to support a large number of medium business with 100’s of hosts connections requirement to the internet. They all use class B.

•Now only /C address were available which increases the routing table size in gateways

Subnetting

•Earlier internetwork is based on a two level hierarchy in the format

HOST ADDRESSNETWORK ADDRESS

Two level hierarchy

NETWORK ADDRESS

Three level hierarchy

SUBNET HOST ADDRESS

• Subnetting brings in a three level hierarchy in IP addressing

Subnetting benefit

150.151.1.0

150.151.2.0

150.151.3.0

150.151.40

150.151.0.0

150.151.1.0 E0

150.151.2.0 E1

150.151.3.0 E2

Customer Routing Table

150.151.0..0 S0…………..………..………….

Service Provider Routing Table

S0S1

Subnetting benefits

•Reduces internet routing table sizes.

•New network addressing requirements can be met locally by the administrator without requiring address allocation from internet authority.

•Link instability within the corporate network will not impact the routing stability of the service provider network.

Subnetting examples

• Assume a organization has a class B network address 150.151.0.0 , the organization has 16 networks to connect

Major Network address Mask

150.151.0.0 255.255.0.0

New Network address Subnet mask Subnet Bits

150.151.1.0 255.255.255.0 8

150.151.2.0 255.255.255.0 8

150.151.3.0 255.255.255.0 8

…………… 255.255.255.0 8

150.151.254.0 255.255.255.0 8

Subnet design considerations

Questions to ask as network support

•How many subnets were required in the current

network?

•How many subnets will be required in the next 2 years?

•What is the maximum no of hosts connected to any single segment?

•What will the maximum no of hosts connected to a segment in the future?

Apply

Private IP addresses

•All the hosts running TCP/IP may not connect to the internet.

•These hosts can be assigned private addresses without requiring address registration from IANA.

•Private IP address blocks are

•10.0.0.0 – 10.255.255.255

•172.16.0.0 – 172.31.255.255

•192.168.0.0 – 192.168.255.255

•RFC 1918 describes private ip addresses.

•Private IP addresses are not seen on the internet.

Conserving Public IP addresses

• Network Address Translation enables private IP machines to be connected to the internet.

• How NAT works?

Internet

Private IP: 10.1.1.5

10.1.1.5 Internet

202.144.50.51 Internet

•Mapping multiple private addresses to a single Public address is referred as Port Address Translation (PAT)

Network Address Translation

•Saves IP addresses.

•Hosts using private IP addresses are invisible on the internet.

•NAT illustration

Internet

IP: 10.1.1.5

10.1.1.5 Internet

202.144.50.51 Internet

NAT usage in SIFY

SIFY Backbone

MDU Services

Private IP 10.x.y.z

IWAY services

Private IP 172.x.y.z

NAT is done here

Enterprise NAT/PAT example

SIFY

IP:

10

.1.1

.0

NAT converts the customer 10.1.1.0 private LAN IP into public IP

IP Next Generation

•IP address are 128 Bits ( 16 Bytes).

•Four times of the existing IP address (4Bytes).

•Features of Ipng

•Solution to address depletion concerns.

•Minimized routing table

•Support for Multimedia applications.

•Security

MAC Address

• MAC Address is Media Access Control address in the data link layer.

•Size of MAC address is 48 Bits(6 Bytes)

•MAC addresses are allocated by IEEE to the vendors

•Vendors assigns MAC addresses in the NIC cards

•MAC addresses are unique for every machine in the network.