Difference Between Network Address Translation (NAT) and Port Address Translation (PAT)

Network Address Translation (NAT) and Port Address Translation (PAT) are the two protocols via which we can map the unregistered private (inside local address of an internal network to a registered public (inside global) address of an external network before moving the packet.

The primary distinction is that NAT is used to map public IP addresses to private IP addresses in a one-to-one or many-to-one relationships. On the other hand, PAT is a sort of NAT in which numerous private IP addresses (many-to-one) are mapped into a single public IP address via ports.

An internal network user with a private IP (unregistered) could not connect to the Internet or external network because each device in the network must have a unique IP address. NAT operates on a router connecting two networks together, and translates internal network private addresses (i.e., not globally unique) into legal public addresses.

It was also created with the intention of preserve IP addresses. As the number of internet users grew faster than the restricted number of IP addresses available, internet users faced the problem of IP address scarcity. The NAT and PAT protocols are used for a specific reason.

What is NAT?

NAT (Network Address Translation) connects two networks and maps the private (inside local) addresses into public addresses (inside global). Inside local denotes that the best address belonged to an internal network and was not assigned by a Network Information Centre or service power. The inside global signifies that the address is a valid address assigned by the NIC or service provider, and one or more inside local addresses to the outside world.

NAT is a method of converting a private IP address or a local address into a public IP address. NAT is a technique for reducing the rate at which available IP addresses are depleted by translating a local IP or private IP address into a global or public IP address. The NAT relation might be one-to-one or many-to-one.

Furthermore, NAT can only configure one address in order to represent the entire network to the outside world. As a result, the translation process is transparent. NAT can be used to migrate and merge networks, share server loads, and create virtual servers, etc.

Types of NAT

There are three types of NAT:

Static NAT
In static NAT, a local address is mapped to a global address. In this type of NAT, the relationship is one-to-one. Static NAT is used if a host needs a consistent address that must be acceded from the internet. For example, networking devices or enterprise servers.
Dynamic NAT
Unregistered private IP addresses can be converted to registered public IP numbers from a pool of public IP addresses using dynamic NAT.
PAT/NAT Overloading/IP masquerading
Among the three varieties, PAT is the most famous. It’s a form of Dynamic NAT that’s comparable to it, but it uses ports to translate many private IP addresses to a single public IP address.

Advantages of NAT

The following are the advantages of NAT:

NAT protects the public addresses that have been registered and slow down the IP address space exhaustion.
Removes the address renumbering process that occurs when switching networks
The occurrence of address overlap was significantly reduced.
Increases flexibility of the connection establishment.

Disadvantages of NAT

The following are the disadvantages of NAT:

Lack of end-to-end traceability
Certain applications are not compatible with NAT
Switching path delays are the outcome of the translation

What is PAT?

Port Address Translation (PAT) is a sort of Dynamic NAT that allows us to configure address translation at the port level while simultaneously optimising the remaining IP address utilisation. PAT maps numerous source local addresses and ports to a single global IP address and ports from a pool of IP addresses which are routable on the destination network. Here the interface IP address is used in conjunction with the port number, and numerous hosts may have similar IP address because the port number is unique.

In order to identify the different translations, it uses a unique source port address on the inside global IP address. Because the port number is encoded in 16 bits, the total number of NAT translations that can be performed is 65536.

The original source is preserved by the PAT. If the source port is already allocated, the available ports are searched. The ports groups are split into three ranges 0 to 511, 512 to 1023, and 1024 to 65535.

If PAT doesn’t find an available port from the proper port group and if more than one external IPv4 address is configured, PAT moves to the next IPv4 address and tries to allocate the original source port until it runs out of available ports and external IPv4 addresses.

Advantages of PAT

The following are the advantages of PAT:

Conserve IP addresses by assigning single public IP to a group of hosts using different port numbers.
Lessens security flaws or security attacks as the private address prevent the public address from being exposed.

Disadvantages of PAT

The following are the disadvantages of PAT:

The internal table can only have a certain number of entries to keep track of connections.
In PAT, more than one instance of the same sort of public service cannot be run from the same IP address.