24-01-2012, 04:47 PM
Efficient Addressing
[attachment=16547]
How to Make Routing Scale
Flat (Ethernet) versus Hierarchical (Internet) Addresses
-All hosts attached to same network have same network address
Problem: inefficient use of Hierarchical Address Space
-class C with 2 hosts (2/255 = 0.78% efficient)
- class B with 256 hosts (256/65535 = 0.39% efficient)
Problem: still Too Many Networks
- routing tables do not scale
-Big tables make routers expensive
-route propagation protocols do not scale
Subnets contd.
Subnetting is not the only way to solve scalability problems
Additional router support is necessary to include netmask and forwarding functionality
Non-contiguous netmask numbers can be used
-They make administration more difficult
Multiple subnets can reside on a single network
-Requires routers within the network
Subnets help solve scalability problems
- Do not require us to use class B or C address for each physical network
-Help us to aggrigate information
Chief advantage of IP addresses: routers could keep one entry per network instead of one per destination host
[attachment=16547]
How to Make Routing Scale
Flat (Ethernet) versus Hierarchical (Internet) Addresses
-All hosts attached to same network have same network address
Problem: inefficient use of Hierarchical Address Space
-class C with 2 hosts (2/255 = 0.78% efficient)
- class B with 256 hosts (256/65535 = 0.39% efficient)
Problem: still Too Many Networks
- routing tables do not scale
-Big tables make routers expensive
-route propagation protocols do not scale
Subnets contd.
Subnetting is not the only way to solve scalability problems
Additional router support is necessary to include netmask and forwarding functionality
Non-contiguous netmask numbers can be used
-They make administration more difficult
Multiple subnets can reside on a single network
-Requires routers within the network
Subnets help solve scalability problems
- Do not require us to use class B or C address for each physical network
-Help us to aggrigate information
Chief advantage of IP addresses: routers could keep one entry per network instead of one per destination host