[asterisk-dev] Via/maddr: (was Re: [Code Review] Properly route responses according to the Via headers in the request)

Olle E. Johansson oej at edvina.net
Tue Jan 4 03:07:01 CST 2011

4 jan 2011 kl. 09.34 skrev Klaus Darilion:

> Am 03.01.2011 21:05, schrieb Simon Perreault:
>> On 01/03/11 12:30, Klaus Darilion wrote:
>>> Actually they can rather easy tell you where to send response - they
>>> just have to send from this certain IP address (in case of UDP).
>>> Thus I think maddr is a "bug".
>> maddr is intended to contain a multicast address. In general you can't
>> just use this kind of address as source without breaking a ton of other
>> things (e.g. ICMP replies come to mind).
> Ok, this makes sense. But why should a response be sent to a multicast address at all?
If the request was sent to multicast, it's a natural result to send the response there too,
to make sure that all recipients of the request got the response.

Now, I haven't seen many implementations of SIP over Multicast. It is used as a 
test on every SIPit and makes all phones ring... 


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