what is the difference between NAT and PAT?
NAT stands for Network Address Translation and PAT stands for Port Address Translation.
A network address translation device obscures all details of the computers connected to the local network. NAT device acts as gateway for all the computers. Behind the NAT device, local network can use any network address space. NAT device acts as proxy for the local network on the internet.
A NAT device helps in increasing the security as it can prevent an outside attacker even to find the local network. This is because of local addressing scheme is not contiguous with the standard IP address space used worldwide.
PAT helps in optimum utilization of IP address space by way of allocating one dedicated IP address for the organization and internally uses IP addresses as per the need. PAT is the extension of the NAT.