Cache Table

ARP Modules

Output Module Sleep until IP packet is received from IP Software Check cache table for entry corresponding to the destination of this IP packet If (found) –If (the state = RESOLVED) Extract the value of the hardware address from the Entry Send the Packet and hardware address to data link layer Return –If (the state = PENDING) Enqueue the packet to the corresponding queue Return If (not found) –Create a cache entry with state= PENDING and ATTEMPT =1 –Create a queue –Enqueue the packet –Send ARP request Return

Input Module Sleep until ARP packet (request or reply) arrives Check cache table for entry corresponding to this ARP packet If (found) –Update the entry ( Set TIME_OUT, Set corresponding –If (state = PENDING) While (the queue is not empty) –Dequeue one Packet –Send the packet and the Hardware address to the data link If (not found) –Create an entry –Add the entry to the table If (the packet is a request) –Send an ARP reply Return

Cache Control Module Sleep until the periodic time matures For every entry in the cache table –If (State = free) continue –If (the state = PENDING) Attempt++ If (Attempt > Maximum) –State = Free –Destroy the corresponding queue Else –Send an ARP request Continue –If (the state = RESOLVED) TIME_OUT = TIME_OUT – ELAPSED_TIME If (TIME_OUT < 0) –The State = Free –Destroy the corresponding queue Return

Cache Table (after 20 sec)

Cache Table (15 sec later)

Cache Table (after 25 sec)