This isn't 100% true.  I've seen situations where loops occur in  
voice networks where you send a call to one of your carriers and  
receive the same call from one of your customers (who also happens to  
be a carrier) because your carrier's carrier is your customer.

Max-Forwards will eventually stop this loop if you're not doing loop  
detection.

-Daniel

On Mar 5, 2007, at 3:13 AM, YOSHIKAWA Tomoyuki wrote:

> Hello,
>
> Epexegetically,
> SIP responses trace a fixed-route which is indicated by Via header.
> Via header is set, when SIP request is transmitted.
> Hence, SIP responses do not loop.
> It is unnecessary to use Max-Forwards header on SIP request.
>
>
>
> On Thu, 1 Mar 2007 16:51:12 -0000
> Attila.Sipos at vegastream.com (Attila Sipos) wrote:
>
>>
>> The Max-Forwards header serves no purpose in SIP responses.
>>
>> It is used to check that a SIP request does not traverse
>> too mnay hops.  In other words it is a primitive tool to
>> prevent a scenario where SIP messages loop infinitely
>> (in the absence of loop detection algorithms).
>>
>> Regards,
>> Attila
>>
>>
>>
>>
>> -----Original Message-----
>> From: sip-implementors-bounces at cs.columbia.edu
>> [mailto:sip-implementors-bounces at cs.columbia.edu]On Behalf Of  
>> Satyendra
>> Tiwari
>> Sent: 01 March 2007 12:24
>> To: sip-implementors at cs.columbia.edu
>> Subject: [Sip-implementors] Max-Forward Header
>>
>>
>> Hello,
>>
>> Is Max-Forward header mandatory in SIP responces?
>> If optional then why?
>>
>>
>>
>>
>>
>> Thanks And Regards,
>> Satyendra Tiwari
>> Alcatel-Lucent
>> _______________________________________________
>> Sip-implementors mailing list
>> Sip-implementors at cs.columbia.edu
>> https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
>>
>
> _______________________________________________
> Sip-implementors mailing list
> [email protected]
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