14-02-2013, 03:03 PM
Network Layer
1Network.pdf (Size: 476.94 KB / Downloads: 396)
Address Mapping
The delivery of a packet to a host or a router
requires two levels of addressing: logical and
physical. We need to be able to map a
logical address to its corresponding physical
address and vice versa. This can be done by
using either static or dynamic mapping.
ARP - The Address Resolution Protocol
An IP datagram must be encapsulated in a frame to
pass through the physical network. This requires the
physical address of the receiver.
ARP associates an IP address with its physical
address.
Cache Table
A sender usually has more than one IP
datagram to send to the same destination
It is inefficient to use ARP for each
datagram
A cache table is used
limited size
RARP
Finds the logical address for a host that only
knows its physical address
RARP request packets are broadcast; RARP
reply packets are unicast
Used by diskless machines to obtain their IP
addresses