Community handle translation (NAT) is a function of Router which is
required for routing visitors.
That’s utterly incorrect. NAT is a kludge (a careless, inefficient resolution) designed to increase the lifetime of IPv4 addressing till IPv6 is ubiquitous. NAT breaks the IP paradigm of end-to-end connectivity, and lots of issues have issues with NAT. Routing works fairly nicely with out NAT. You need to solely use NAT had been you completely should use it, e.g. personal to public addressing, or for becoming a member of two networks with overlapping addresses.
It does processing based mostly on each Community layer and Transport layer
(layer 4) headers.
Once more, no. Routing doesn’t contain the layer-4 header. One type of NAT, NAPT (Community Tackle Port Translation), will use the TCP or UDP ports, or ICMP question IDs, nevertheless it solely works for these three protocols, and it breaks different transport protocols and lots of purposes. A routing desk (what routers use to find out the trail of packets) has nothing about layer-4 protocols in it.
RFC 2663, IP Community Tackle Translator (NAT) Terminology and Issues explains NAPT:
4.1.2. Community Tackle Port Translation (NAPT)
NAPT extends the notion of translation one step additional by additionally
translating transport identifier (e.g., TCP and UDP port numbers,
ICMP question identifiers). This permits the transport identifiers of a
variety of personal hosts to be multiplexed into the transport
identifiers of a single exterior handle. NAPT permits a set of hosts
to share a single exterior handle. Word that NAPT may be mixed
with Primary NAT so {that a} pool of exterior addresses are utilized in
conjunction with port translation.For packets outbound from the personal community, NAPT would translate
the supply IP handle, supply transport identifier and associated fields
similar to IP, TCP, UDP and ICMP header checksums. Transport identifier
may be one in every of TCP/UDP port or ICMP question ID. For inbound packets, the
vacation spot IP handle, vacation spot transport identifier and the IP
and transport header checksums are translated.