Guilherme Balena Versiani wrote:
> Hello Paul,
>
> Paul Kyzivat wrote:
>
>> erol turac wrote:
>>
>>
>>> how can proxies edit c line in sdp? which rules can be applied to c line by
>>> proxies?
>>>
>>> I have a sip client behind nat which insert its own private IP at session
>>> level (c line under m line)
>>> and NAT adds its own public IP into c line at media level before forwarding
>>> 200 OK to proxy.
>>> Here, proxy removes c line at media level and forward 200 OK to ingress side
>>> with private IP at session level.
>>> Is it valid behaviour for proxies?
>>>
>>>
>> No. Proxies are not permitted to alter the body of a message.
>>
>> Paul
>>
>>
>
> Why? IETF people normally use SHOULD, MUST, etc terms to these
> affirmatives. I see no reason why a SIP element acting as 'proxy' can't
> change SDP contents...
Easy one. For requests, RFC3261 section 16.6 step 1:
The proxy MUST NOT add to, modify,
or remove the message body.
And for responses, RFC3261 section 16.7 step 9:
The proxy MUST NOT add to, modify, or
remove the message body.
If it breaks these rules, it is no longer acting as a proxy.
> I think you are trying to match the desired
> server behavior to some 'documented' or 'prompt' solution, such as the
> very old discussion about SIP Proxy versus B2BUA.
The question was 'is it valid behaviour for proxies?', to which the
answer is 'No'. Is it valid for B2BUAs? Well, they are less well
defined, so you get more flexibility in what you do. Whether it is
valid or not for a particular situation will depend on what the
requirements for the B2BUA actually are.
Michael
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