WG Action: RECHARTER: Behavior Engineering for Hindrance Avoidance (behave)

[IESG Secretary <[e-mail]>]

The charter of the Behavior Engineering for Hindrance Avoidance (behave)
working group in the Transport Area of the IETF has been updated.  For
additional information, please contact the Area Directors or the working
group Chairs.


Behavior Engineering for Hindrance Avoidance (behave)
-----------------------------------------------------
Last Modified: 2009-09-09

Current Status: Active Working Group

Additional information is available at tools.ietf.org/wg/behave
Chair(s):

    * Dan Wing <[e-mail]>
    * Dave Thaler <[e-mail]>

Transport Area Director(s):

    * Magnus Westerlund <[e-mail]>
    * Lars Eggert <[e-mail]>

Transport Area Advisor:

    * Magnus Westerlund <[e-mail]>

Mailing Lists:
General Discussion: [e-mail]
To Subscribe: [e-mail]
In Body: In Body: subscribe
Archive: http://www.ietf.org/mail-archive/web/behave

Description of Working Group:

The behavior of NATs varies from one implementation to another. As a 
result it is very difficult for applications to predict or discover the 
behavior of these devices. Predicting and/or discovering the behavior of 
NATs is important for designing application protocols and NAT traversal 
techniques that work reliably in existing networks. This situation is 
especially problematic for end-to-end applications where one or both 
end-points are behind a NAT, such as multiuser games, interactive 
multimedia and P2P download.

The working group documents best current practices to enable NATs to 
function in as deterministic a fashion as possible. The NAT behavior 
practices will be application independent. This has already completed 
for UDP, TCP, DCCP, Multicast and ICMP. It continues with SCTP and any 
additional protocol deemed necessary to handle. The WG has documented 
approaches for characterizing and testing NAT devices.

BEHAVE will develop protocol-independent toolkits usable by application 
protocols for NAT traversal. The WG has already produced an update of 
the binding discovery protocol STUN. It will now produce a relay 
protocol that focuses on security and is usable with both IPv4 and IPv6, 
and capable of relaying between the two IP versions.

Due to the WG's experience with translators and their behavior it has 
been given the following tasks to help encourage migration to IPv6. To 
support deployments where communicating hosts require using different 
address families (IPv4 or IPv6), address family translation is 
needed to establish communication. In BEHAVE's specification work on 
this topic it will coordinate with the V6ops WG on requirements and 
operational considerations.

"An IPv4 network" or "an IPv6 network" in the descriptions below refer 
to a network with a clearly identifiable administrative domain (e.g., an 
enterprise campus network, a mobile operator's cellular network, a 
residential subscriber network, etc.). It will also be that network that 
deploys the necessary equipment for translation.

The BEHAVE WG will design solutions for the following six translation
scenarios; other scenarios are out of scope:

1. An IPv6 network to IPv4 Internet, i.e. perform translation between 
IPv4 and IPv6 for packets in uni- or bi-directional flows that are 
initiated from an IPv6 host towards an IPv4 host. The translator 
function is intended to service a specific IPv6 network of arbitary 
size. Port translation is necessary on the IPv4 side for efficient IPv4 
address usage.

2. IPv6 Internet to an IPv4 network, i.e. perform translation between 
IPv4 and IPv6 for packets in uni- or bi-directional flows that are 
initiated from an IPv6 host towards an IPv4 host. The translator 
function is intended to service a specific IPv4 network using either 
private or public IPv4 addresses. This scenario has different 
constraints compared to (1), e.g. the IPv4 hosts that are to be 
reachable over IPv6 can be enumerated. Therefore, the WG should attempt 
to design a simpler solution with less impact on applications.

3. An IPv4 network to IPv6 Internet, i.e. perform translation between 
IPv4 and IPv6 for packets in uni- or bi-directional flows that are 
initiated from an IPv4 host towards an IPv6 host. The translator 
function is intended to service a specific IPv4 network using either 
public or private IPv4 address space.

4. IPv4 Internet to an IPv6 network, i.e. perform translation between 
IPv4 and IPv6 for packets in uni- or bi-directional flows that are 
initiated from an IPv4 host towards an IPv6 host. The translator 
function is intended to service a specific IPv6 network where selected 
IPv6 hosts and services are to be reachable.

5. An IPv6 network to an IPv4 network, i.e., perform translation between
IPv6 and IPv4 for packets in uni- or bi-directional flows that are 
initiated from an IPv6 host towards an IPv4 host.  The translation 
function is intended to service a specific IPv6 network of arbitrary 
size and a specific IPv4 network of arbitrary size (neither of which are 
the Internet).

6. An IPv4 network to an IPv6 network, i.e., perform translation between
IPv4 and IPv6 for packets in uni- or bi-directional flows that are 
initiated from an IPv4 host towards an IPv6 host.  The translation 
function is intended to service a specific IPv6 network of arbitrary 
size and a specific IPv4 network of arbitrary size (neither of which are 
the Internet).

All translation solutions shall be capable of handling flows using TCP, 
UDP, DCCP, and SCTP, unless they prevent a timely completion of the work 
item. The parts of ICMP that can be translated are also required to work 
across a translation solution.  Additional protocols directly on top of 
IP may be supported. Translation mechanisms must handle IP 
fragmentation.

The translators should support multicast traffic and its control traffic
(IGMP and MLD) across them, both Single Source Multicast (SSM) and Any 
Source Multicast (ASM). However, the WG may determine that it becomes 
too complex or too difficult to realize with maintained functionality, 
for some or all cases of multicast functionality.

Translation mechanisms cannot transparently support protocols that embed
network addresses within their protocol messages without application 
level gateways (ALGs). Because ALGs have security issues (like blocking 
usage of TLS), are error prone and brittle, and hinder application 
development, the usage of ALGs in the defined translators should be 
avoided. Instead application developers will need to be aware and use 
mechanisms that handle the address family translation. ALGs may be 
considered only for the most crucial of legacy applications.

DNS is a crucial part in making a large number of applications work 
across a translator. Thus the solution to the above translation cases 
shall include recommendations for DNS. If additional DNS functionality 
is needed, it may be developed. Any DNS extensions must be developed 
together with the DNSEXT WG, including issuing a joint WG last call for 
any documents.

The WG needs to determine the best method for providing address space to
a translator in the different deployment cases and documenting the pros 
and cons of the suggested approaches. The WG is to seek input from the 
Routing, Operations and Internet areas.

Solutions may solve more than one of the cases, however timely delivery
is more important than a unified solution.

Goals and Milestones:

Done	  Submit BCP that defines unicast UDP behavioral requirements 
for NATs to IESG
Done	  Submit a BCP that defines TCP behavioral requireents for NATs 
to IESG
Done	  Submit a BCP that defines ICMP behavioral requirements for 
NATs to IESG
Done	  Submit informational that discusses current NAT traversal 
techniques used by applications
Done	  Submit BCP that defines multicast UDP
Done	  Submit revision of RFC 3489 to IESG behavioral requirements for 
NATs to IESG
Done	  Submit informational document for rfc3489bis test vectors
Done	  Submit experimental document that describes how an application 
can determine the type of NAT it is behind
Done	  Submit BCP document for DCCP NAT behavior
Dec 2009  Submit to IESG: SCTP NAT behavior (BCP)
Done      Submit to IESG: relay protocol (std)
Done      Determine relative prioritization of the four translation 
cases. Documented in IETF74 minutes.
Sep 2009  Submit to IESG: relaying of a TCP bytestream (std)
Dec 2009  Submit to IESG: IPv6 relay protocol (std)
Done      Determine what solutions(s) and components are needed to solve 
each of the four cases. Create new milestones for the solution(s) and 
the components. Documented in IETF74 minutes.
Done      Submit to IESG:  TURN-URI document (std)
Dec 2009  Submit to IESG:  framework for IPv6/IPv4 translation (info)
Dec 2009  Submit to IESG:  stateless IPv6/IPv4 translation (std)
Dec 2009  Submit to IESG:  stateful IPv6/IPv4 translation (std)
Dec 2009  Submit to IESG:  DNS rewriting for IPv6/IPv4 translation (std)
Jan 2010  Submit to IESG:  FTP ALG for IPv6/IPv4 translation (std)
Jan 2010  Submit to IESG:  IPv6 prefix for IPv6/IPv4 translator (std)
Mar 2010  Submit to IESG:  large scale NAT requirements (BCP)