Re: [Sipping] Draft: Functions of Current SBCs

[Eunsoo Shim <[e-mail]>]

Hi, Jonathan,

The document you referred to in the below was very helpful for me.
In particular, I feel the problem mentioned in the text below can affect
the end users and the organization having the (SIP-)ALG noticeably today.

"

Furthermore, extensions to SIP, such as UPDATE
[17] add additional cases. Even if both endpoints in a call support
this specification, they will not be able to implement it if the ALG
does not support it. Of course, the fact that it is not supported by
the ALG will be hard to ascertain because of the diagnostic issues
described above.

"
SIP-ALGs who do not understand a certain extension of the SIP messages
will discard the messages even though the SIP messages are legitimate.
This problem indeed happened in deployments.
Regards,

Eunsoo


Jonathan Rosenberg wrote:

> inline.
>
> Roy, Radhika wrote:
>
>> Medhavi:
>>
>> We did discuss this during RFC 3261 (Jonathan R. - is this ALG
>> example for modifying SDP an exception or we are missing something?).
>
>
> Proxies are not permitted to modify SDP, period. A SIP ALG that does
> so is a violation of RFC3261. Indeed, ALGs present many problems, of
> which SDP rewriting is just one. Please take a look at:
>
> http://www.ietf.org/internet-drafts/draft-iab-nat-traversal-considerations-00.txt
>
>
> -Jonathan R.

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