Network Address Translators
Network Address Translators WG
||Network Address Translators
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IP V4 Network Address Translation (NAT) has become an increasingly
common function in the Internet for a variety of reasons. NATs are used
to interconnect a private network consisting of unregistered IP
addresses with a global IP network using limited number of registered
IP addresses. NATs are also used to avoid address renumbering in a
private network when topology outside the private network changes for
variety of reasons. And, there are many other applications of NAT
A number of NAT deployments are currently in use and naturally, a large
number of internet applications work transparently with NATs. However,
there are applications for which NATs would fail and custom-specific
Application Level Gateways (ALGs) are required to perform translations
for those applications.
NAT has the potential to interrupt end-to-end nature of Internet
applications, thereby threatening end-to-end security and other
end-to-end functions. In addition, NAT has topology restrictions and
other constraints on the protocols and applications that run across
NATs. Thus NATs have a particular area of application and should not
be considered a general solution.
This working group will provide a forum to discuss applications of NAT
operation, limitations to NAT, and impact of NAT operation on internet
protocols and applications. The Working Group recognizes that NAT may
interfere with protocols that use cryptographic protection for
authentication, integrity or confidentiality. The Working Group will
NOT suggest changes in such protocols to make them NAT friendly when
such modification will significantly reduce the security provided by
those protocols. However, the Work Group will examine and discuss
alternative solutions, and other new ideas relating to this issue.
Broadly speaking, the objective of the work group is to come up with a
series of documents in the following categories.
The first category of documents will address what NAT is, how NAT works
and applications of NAT operation in address conservation, prevention
of address renumbering, load sharing and other areas.
The second category of documents will address requirements of NAT and
limitations to NAT operation. Specifically, this will include a
detailed list of applications which are known to have problems working
The third category of documents are Informational RFCs which will
specify NAT friendly application and protocol design guidelines,
interactions between NATs and applications such as DNS and protocols
such as IP sec. Particular emphasis will be placed on security issues.
The Work group will also examine and discuss various alternative
solutions, and other ideas to identify areas where NATs or other
protocols and applications can be improved to overcome the shortcomings
in interoperability or functionality.
The fourth category of documents will deal with network management of
Exploration of the use of NATs for load sharing is not within the scope
of this working group.
The goals and milestones section below lists just the subject matter of
issues to be covered. This is done so deliberately because there may be
some adjustments made to the packaging of the RFCs, while covering all
of the contents below. The work group will decide how to group the
contents into different RFCs.