Traditional IP Network Address Translator (Traditional NAT) (RFC3022)
Original Publication Date: 2001-Jan-01
Included in the Prior Art Database: 2019-Feb-14
Internet Society Requests For Comment (RFCs)
P. Srisuresh: AUTHOR [+1]
The NAT operation described in this document extends address translation introduced in RFC 1631 and includes a new type of network address and TCP/UDP port translation. In addition, this document corrects the Checksum adjustment algorithm published in RFC 1631 and attempts to discuss NAT operation and limitations in detail. This memo provides information for the Internet community.
Network Working Group P. Srisuresh Request for Comments: 3022 Jasmine Networks Obsoletes: 1631 K. Egevang Category: Informational Intel Corporation January 2001
Traditional IP Network Address Translator (Traditional NAT)
Status of this Memo
This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited.
Copyright (C) The Internet Society (2001). All Rights Reserved.
The NAT operation described in this document extends address translation introduced in RFC 1631 and includes a new type of network address and TCP/UDP port translation. In addition, this document corrects the Checksum adjustment algorithm published in RFC 1631 and attempts to discuss NAT operation and limitations in detail.
Basic Network Address Translation or Basic NAT is a method by which IP addresses are mapped from one group to another, transparent to end users. Network Address Port Translation, or NAPT is a method by which many network addresses and their TCP/UDP (Transmission Control Protocol/User Datagram Protocol) ports are translated into a single network address and its TCP/UDP ports. Together, these two operations, referred to as traditional NAT, provide a mechanism to connect a realm with private addresses to an external realm with globally unique registered addresses.
The need for IP Address translation arises when a network’s internal IP addresses cannot be used outside the network either for privacy reasons or because they are invalid for use outside the network.
Network topology outside a local domain can change in many ways. Customers may change providers, company backbones may be reorganized, or providers may merge or split. Whenever external topology changes
Srisuresh & Egevang Informational [Page 1]
RFC 3022 Traditional NAT January 2001
with time, address assignment for nodes within the local domain must also change to reflect the external changes. Changes of this type can be hidden from users within the domain by centralizing changes to a single address translation router.
Basic Address translation would (in many cases, except as noted in [NAT-TERM] and section 6 of this document) allow hosts in a private network to transparently access the external network and enable access to selective local hosts from the outside. Organizations with a network setup predominantly for internal use, with a need for occasional external access are good candidates for this scheme.
Many Small Office, Home Office (SOHO) users and telecommuting employees have multiple Network nodes in their office, running TCP/UDP applications, but have a single IP address assigned to their remote access router by their service provider to access remote networks. This ever increasing community of remote access users would be benefited by NAPT, which would permit multiple nodes in a local network to simultaneously access remote networks using the single IP address...