1. NETWORK LAYER

2. Ch 19. Logical Addressing

3. 19.1 IPv4 Addresses For world-wide communications IPv4 Address
Uniquely identify a device in the network
Logical address = IP address (in TCP/IP protocol)
IPv4 Address
32 bits long  232 address space
Globally unique
Notation (binary or dotted-decimal)

4. Classful Addressing
Address space is divided into five classes: A, B, C, D, and E
netid
hostid

5. Classful Addressing Mask is used to find the netid and hostid
Subnetting – divide a large block of addresses into several groups (increases the number of 1s in the mask)
Supernetting – combine small blocks of addresses due to depletion of class A and B addresses.
Address depletion
A large part of addresses were wasted

6. Classless Addressing
To overcome address depletion classless addressing is used.
Allow a different size of address blocks with restrictions of
Addresses in a block must be contiguous
The number of addresses in a block is a power of 2
The first address must be divisible by the number of addresses

7. Classless Addressing A block of addresses can be defined as x.y.z.t /n
where x.y.z.t is any address in the block
/n defines the mask
First n bits are the netid
The block can have up to 2(32–n) hosts
Practice with example 19.9

8. Exp: /28 will be represented in binary as ( is the first address in the block)
The first address is often assigned to a special device, e.g., a gateway

9. Hierarchy of IPv4 Address
Comparison
Telephone number
IPv4 Address

10. Subnetting (Multi-level Hierarchy)
“Internally” divide a block of addresses into clusters of networks (called subnets)
An outside device still sees them as a single block
Needs to split in 3 groups.
Example: Organization is given
/26

11. Example 19.10
A block of addresses /16 needs to be distributed to three groups as follows:
64 customers; each needs 256 addresses
128 customers; each needs 128 addresses
128 customers; each needs 64 addresses

12. Network Address Translation (NAT)
Addresses for private network
Home users have a small network, where each device needs an IP address
Some addresses are reserved for “internal network”
Anyone can use these addresses without permission

13. NAT
The private network should has one single connection to the Internet
Address translation

14. Translation Table

15. Translation Table Entry of a table may … NAT and ISP
use one (global) IP address
use a pool of (global) IP addresses – often used by ISP (see below)
use both IP address and port number – often known as IP sharing
NAT and ISP

16. 19.2 IPv6 Addresses IPv6 Address 128 bits long  2128 address space
Globally unique
Notation (hexadecimal colon)

17. Abbreviated representation

18. Address Structure
Unicast
Multicast

19. Homework
Exercise 18 19 22 26