RE: How to transport BFCP in the presence of NATs

[<[e-mail]>]

There has been much discussion of this NAT issue with DCCP and SCTP on the DCCP mailing list of late - see archives. Should they do a general UDP encap, or specific per-protocol UDP?

It's hard to care about protocols that no-one will use... the people who do care care about only their protocol, so protocol-specific encaps (which no-one will use either) are inevitable.

-----Original Message-----
From: [e-mail] [mailto:[e-mail]] On Behalf Of Gonzalo Camarillo
Sent: 19 July 2010 13:01
To: [e-mail]
Subject: How to transport BFCP in the presence of NATs

Folks,

BFCP (Binary Floor Control Protocol), defined in RFC 4582, runs between a client and a floor control server. Generally, the floor control server has a public IP address. The client establishes a TCP connection towards the floor control server so that, even if the client is behind a NAT, everything works.

However, in some existing deployment scenarios the floor control server functionality is implemented in an endpoint, which may be behind a NAT.
A typical session between two endpoints in these scenarios consist of a BFCP connection and one or more media streams (e.g., audio and video) between them. In this type of scenario, NAT traversal becomes a problem.

Existing deployments implement different approaches to address the fact that the floor control server is not directly reachable. One of these approaches consists of transporting BFCP over UDP instead of over TCP (this approach is documented in the draft below). In this way, the endpoints can use ICE to find connectivity between them.

https://datatracker.ietf.org/doc/draft-sandbakken-xcon-bfcp-udp/

An alternative approach would be to still use TCP as a transport and use ICE TCP. However, the success rate of ICE TCP is not high enough at this point. Yet another alternative would be to tunnel BFCP over TCP over UDP.

The XCON WG is aware of the guidelines given in RFC 5405 but would like to ask the transport community for further guidance on this issue.

Note that this is actually a general issue that will affect any protocol for which TCP would be the natural transport but that would need to run between endpoints in NATted environments. RELOAD
(draft-ietf-p2psip-base) would be an example of a similar protocol (which currently intends to use ICE TCP).

Given that this issue appear to be more general than BFCP and may affect other protocols, we would appreciate to get input on how to proceed.

Thanks,

Gonzalo