[maarten]

As an experiment I am trying to use the SPA3000 as a PSTN Gateway, with Microsoft LCS as the SIP Proxy and Windows Messenger 5 as the client. I try to call out through the PSTN, directly from the phone dialer that is hidden in Messenger.

The SPA fails to register with LCS as the Proxy. I fear this has to do with the fact that I could not find a way to tell the SPA to use TCP as the SIP transport (LCS does not support UDP for security reasons).

Can someone confirm if the SPA3000 is compatible with Microsoft LCS or not? Has anyone tried this? Does the SPA-3000 support SIP over TCP? (which I did expected after reading the datasheet).

[PhoneBoy]

I don't see a way to tell the Sipura to use TCP instead of UDP.

[maarten]

The SPA3000 datasheet states it complies to the SIPv2 standard, RFC 3261. Section 18 of this RFC says:

All SIP elements MUST implement UDP and TCP. SIP elements MAY implement other protocols.

Making TCP mandatory for the UA is a substantial change from RFC 2543. It has arisen out of the need to handle larger messages, which MUST use TCP, as discussed below. Thus, even if an element never sends large messages, it may receive one and needs to be able to handle them.

If the SPA3000 does not support TCP then it clearly does not conform to SIPv2 and RFC3261. (The same goes for Microsoft LCS btw, but they don't claim to).

Is the problem that there is no way to instruct SPA3000 to send TCP or is it also not able to receive it?

[Sipura_Technology]

SIP over TCP is not supported on SPA3000.

The TCP support is not mandatory for a User Agent. For the proxy server, support of both is mandatory.

[maarten]

The TCP support is not mandatory for a User Agent

Thanks for the clear answer. However, as I quoted in my earlier post, I think the RFC quite clearly states that it *is*. Sipura should at least update the datasheet to warn that SIP over TCP transport is not supported. This would have prevented me from buying it, I knew I needed it and I specifically checked.

Can Sipura implement SIP over TCP in a future firmware version? (and maybe TLS as well, while at it?) This is important for users and businesses who live in the Microsoft universe, as it enables for them the type of applications for which some Asterisk users already use their SPA's (telecommuting etc). I probably don't have to convince Sipura there is a large user-base there.

Of course you could argue that Microsoft should support UDP (they do in Messenger) but this "Thrusted Compunting" thing seems to make them unwilling to do so in LCS.