Address Plus Port (aplusp) Concluded WG

Note: The data for concluded WGs is occasionally incorrect.

WG Name Address Plus Port
Acronym aplusp
Area Internet Area (int)
State Concluded
Charter charter-ietf-aplusp-01 Approved
Dependencies Document dependency graph (SVG)
Personnel Chairs Christian Jacquenet
Dan Wing
Area Director Ralph Droms

Charter for Working Group

By the end of 2012, it is expected that the Regional Internet Registries
(RIRs) will have no more public IPv4 addresses to allocate. IPv6 is the
only perennial solution to solve this IPv4 address shortage, therefore
IPv6 deployment must not be delayed. However, at the exhaustion date,
offering only access to the IPv6 Internet won't be satisfactory for the
customers because a lot of services will remain IPv4-only accessible.

The challenge for ISPs is to be able to offer access to the IPv4
Internet to new customers, with a steady IPv4 public address pool.
Several solutions have been proposed, they all rely on the principle of
sharing an IPv4 public address among several customers at the same time.
They extend the address space in adding port information. They differ on
the way they manage the port value. Solutions can be classified into two
main families: CGN-based solutions and A+P solutions.

CGN-based solutions propose the introduction of a Network Address and
Port Translator (NAPT) function [RFC3022] in the ISP network, denoted as
Carrier Grade NAT (CGN), or Large Scale NAT (LSN) [I-D.nishitani-cgn],
or Provider NAT. The CGN is responsible for translating private
addresses to publicly routable addresses. Private addresses are assigned
to customers, a pool of public addresses is assigned to the CGN, the
number of public addresses is much smaller than the number of customers.
A public address of the CGN pool will therefore be shared by several
customers at the same time.

A+P solutions avoid the presence of a CGN function. They assign the same
IP public address to several customers at the same time (shared
address). They also assign a restricted port range to each customer so
that two customers with the same IP address have two different port
ranges that do not overlap. These solutions are called A+P
(Address+Port) [I-D.ymbk-aplusp], or Port Range

Work for the first solution group is currently hosted in the softwire
and behave WGs. Despite a lot of drafts available for the second group
of solutions, there is no official place in the IETF yet, to discuss and
validate the A+P related work. A first non-forming WG BoF (shara) in
IETF74 San Francisco demonstrated significant interest among the
Internet community. The purpose of this BoF is to establish goals for a
new working group that will host A+P work.


Date Milestone