Seems pertinent to the situation so may as well mention it....

 

Most modern UACs are RFC3261 compliant and shouldn't have this problem. However, I have seen similar problems with this "vsf" parameter on other systems, namely interconnecting a VoiceMaster platform with OpenSER 1.1.1 using uac_replace_from.

 

In this particular scenario VoiceMaster was receiving the 200 OK reply from OpenSER but was responding with an ACK in which the "vsf" parameters had been modified (i.e. changed from a mixture of lower and uppercase characters to only lowercase).

 

Somewhere in the RFC it seems to suggest that if a UAC does not understand the "vsf" parameters it should not modify them in the response it sends back so clearly in this case, the VoiceMaster system was at fault. Nonetheless it resulted in some rather ackward behaviour in OpenSER, since after the uac_replace_from function was applied to the received ACK, the "From" field was replaced with gibberish, which once forwarded to the destination gateway or SIP A/S, the SIP A/S was unable to process. Hence, you ended up with the behaviour you described above, - i.e. the 200 OK is retransmitted over and over again until the request finally timed out.

 

(By "gibberish" I am referring to garbage characters like you would see in a binary file. Perhaps the result of a memory leak.)
 

I can only imagine that such UACs are perhaps conforming to the older RFC 2543 SIP standard, which does not use such parameters.

 

 

On 03/01/2008, Iņaki Baz Castillo <ibc@in.ilimit.es> wrote:

On Thursday 03 January 2008 12:36:24 Jesus Rodriguez wrote:
> Hola Iņaki,
>
> > The problem is that this "200 OK" from OpenSer to Linksys PAP is not
> > recognized by Linksys PAP
> > who doesn't reply with an ACK (just ignores the "200 OK"), so the
> > "200 OK" is resent again
> > and again by Asterisk.
> >
> > This issue just occurs with the Linksys PAP:
> >  Product Name:  PAP2-NA
> >  Software Version:  2.0.12(LS)  Hardware Version:  0.03.4
>
> I would recommend to upgrade the firmware version of the PAP2. Version
> 2.0.12 is a pretty old.

Yes, I upgraded to 3.1.22(LS) and the issue has dissapeared.

Anyway it scares me a little if some UAC don't allow certains parameters as:
vsf=AAAAAAAAAB8AAAAAAAAAAAAAAAAAAAAAAEBvcGVuc2VyLmlsaW1pdC5lcw--

Maybe Linksys with old firmware didn't accepted that parameter because it's
very long. Other parameters as "dialog" were allowed in Record-Route header.

Obviosly it's a bug in Linksys, but hope it doesn't occur in other common
UACs.

Thank a lot ;)



--
Iņaki Baz Castillo
ibc@in.ilimit.es

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