08-02-2013, 10:48 AM
Network Layer
1Network Layer.ppt (Size: 1.09 MB / Downloads: 90)
Position of network layer
The network layer is responsible for the delivery of individual packets from the source to the destination host
IPv4 Addresses
An IP address is a 32-bits long
The IP addresses are unique and universal
The address space of IPv4 is 232 or 4,294,967,296
Binary notation: 01110101 10010101 00011101 00000010
Dotted-decimal notation: 117.149.29.2
Subnetting
Divide a large block of addresses into several contiguous groups and assign each group to smaller networks called subnets
Increase the number of 1s in the mask
Supernetting
Combine several class C blocks to create a larger range of addresses
Decrease the number of 1s in the mask (/24 /22 for C addresses)
Classless addressing
Classful addressing has created many problems
Many ISPs and service users need more addresses
Idea is to have variable-length blocks that belong to no class
Three restrictions on classless address blocks;
The addresses in a block must be contiguous, one after another
The number of addresses in a block must be a power of 2
The first address must be evenly divisible by the number of addresses
Mask and Address Blocks
In IPv4 addressing, a block of addresses can be defined as x.y.z.t /n in which x.y.z.t defines one of the addresses and the /n defines the mask.
The first address in the block can be found by setting the rightmost 32 − n bits to 0s
The last address in the block can be found by setting the rightmost 32 − n bits to 1s
The number of addresses in the block can be found by using the formula 232−n
IPv6 Addresses
Despite all short-term solutions, such as classless addressing, DHCP (Dynamic Host Configuration Protocol), and NAT, still address-hungry
An IPv6 address is 128 bits long
Hexadecimal colon notation: