Re: ISUP tunneling

[Jonathan Rosenberg <[e-mail]>]

"Adam B. Roach" wrote:
> 
> >I have a question regarding draft "ISUP parameters expected in SIP
> >messages"
> ><draft-roach-sip-isup-parameters-00.txt>. You describe that ISUP
> >messages
> >can be expected in a CANCEL or BYE request. I suppose that all messages
> >tunneled
> >onto SIP are carried in Content-Encoding header field, and this header
> >is defined in
> >SIP as being not applicable for CANCEL and BYE methods. What am I
> >missing here?
> 
> Nothing; I overlooked this fact when I put the draft together.
> Thanks for pointing this out. I will mention, in future versions
> of the draft, that the use of ISUP tunneling for this application
> adds the possibility of having Content-Encoding headers on
> BYE and CANCEL messages.
> 
> Henning, Jonathan, et al: is there a reason the Content-Encoding
> was marked as N/A on BYE and CANCEL? Could this be added to 2543
> when all the other bugfixes are put in?

The reason was that BYE was not supposed to carry any body.
Content-Length and
Content-Type are similarly not allowed. Clearly, if ISUP tunnelling is
done,
there is a need. I can see there might be other applications. Its easy
enough
to fix.

CANCEL is a different story. Its not end to end; its regenerated at each
proxy.
This means it cannot be protected by end to end authentication or
encryption. 
It can also be originated by proxies, unlike BYE, which cannot. I would
argue
that there never should be a body in a CANCEL. It should not be used to
convey
call information beyond "cancel the search".

-Jonathan R.
-- 
Jonathan D. Rosenberg                       Lucent Technologies
Member of Technical Staff                   101 Crawfords Corner Rd.
High Speed Networks Research                Holmdel, NJ 07733
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