Question

Due to some bug in cache control module of ARP package, it increments the time out value instead of decrementing it. How does it affect the performance of the cache tablein following scenarios?a.Number of different destination IP addresses are less than size of cache tableb.Number of different destination IP addresses aresignificantly larger than size of cache table.

Answer 1

Cache Control Module: Basically it checks the cache table for every 5 seconds.If the state field of the entry is free,it chekcs another entry.

a) If the state field of the entry is pending, the cache control will be increased the value of attempt field by 1, It then checks the value of the attempt field. If the value of the attempt field is greater than the maximum limit which is allowed, it updates the state field to free and destroys the corresponding queue.

Packet forwarding is done when uIP receives a packet that has a destination IP address that does not match any of the IP addresses of the node. A node typically has multiple addresses: one or more unicast addresses and at least one broadcast or multicast address. Packets that do not match the addresses should be forwarded to a neighboring node, either because the address matches that of the neighbor or because the neighbor has a route to the destination address.

Packet forwarding occurs only when uIP has been configured to be a router. The packet forwarding mechanism is then invoked as part of the output processing.

The packet forwarding mechanism is modular and does not specify any particular routing mechanism to be used. Rather, a routing mechanism will register itself with the forwarding module upon startup. For every packet, the forwarding mechanism asks the routing module to look up the destination IP address and return the address to the next-hop neighbor. The routing module may implement this any way it wants by using a table of destination addresses, a table of network prefixes, a hash table of addresses, a cache of the recently used routes, or any other way it finds suitable. The routing protocol may perform a route discovery for each address not found in its cache.

So below picture is the Address resolution protocol of my PC. It shows the Internet Address, Physical address which is Mac address and its type. i have printed the ARP table below.