[Serusers] Instant Messaging User Agent Interoperability problem

[Samuel Osorio Calvo]

Hi!

Regarding IM within SIP, there are two modes: paging and session.
The first is a kind of sms service, where users sends *few* messages(if you are not a teenager... ;) ) . This is provided by the standard SIP request MESSAGE.
The session mode provides the typical chat scenario, where users are typing *constantly* message and they are exchanged in (soft) real time. This is provided by the MSRP protocol defined by the IETF's group SIMPLE. In that case, the MSRP session parameters are carried in the SDP body of the INVITE. Once the Offer/Answer is completed, both end points can send messages via the MSRP session.

For both modes, SIP proxies (SER) do not require extended capabilities because in both cases SIP requests (MESSAGE for paging and INVITE for session) are proxied normally and finally arrive to the end points. The main difference lies in the UA: the paging mode is widely supported because almost all UA supports MESSAGE request, while the session mode is not yet so extended because MSRP is quite new. 

Although Messenger started (>4.6 I think) with plain SIP supporting only MESSAGE requests, it needed a chat session mode to be implemented and since MSRP was not still finished, microsoft decided to develop its own protocol (strange, isn't it?). That is why new versions of microsoft messenger are not compatible with standard SIP UA.

Once MSRP is extended (there's an open source implementation in www.sipfoundry.org), standard SIP UA (excluding microsfot thing) will be fully interoperable both in paging mode (MESSAGE) and session mode (MSRP).

My 0.02,

Samuel.


Unclassified.
>>> "Victor Huertas Garcia" <vhuertas at hotmail.com> 07/01/05 12:40PM >>>


Hi all,

I am testing the Instant Message Service with the SER v0.8.14 and I see that 
it routes them correctly towards the destination user agent. However, what I 
have seen is a tremendous imcompatibility between user agents of different 
vendors.

Here just a bit of this:

IM between two Windows Messenger 4.7.

What I see it that the very first MESSAGE in the conversation is sent 
towards the SER and it routes it perfectly but the subsequent MESSAGES are 
exchange between both Messengers directly!!! It is weird... but this is how 
it is working.

IM between Window Messenger 4.7 and EyeBeam v1.1

The EyeBeam always send the MESSAGES towards the SIP proxy and messenger 
receive them with no problem. However, when the messenger tries to send a 
MESSAGE in the conversation it even doesn't send the packet (I tried to 
capture it with Ethereal and no packet was sent at all) and subsequently 
tell you that the text message could not be delivered to the destination.

IM between EyeBeam v1.1

No problem at all.

IM involving Windows Messenger 5.1

This version of messenger sends an INVITE to the destination before issuing 
the MESSAGE. With EyeBeam is a total disaster and the comunication is not 
possible.


My conclusion is that the SER has not implication in such incompatibility at 
all and that is a matter of interoperability among vendors and different 
implementations of SIMPLE. Do you agree?

Thanks in advance

Victor


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