Re: [straw] WGLC for draft-ietf-straw-sip-traceroute-01.txt

Great - new rev being submitted now...

On Mar 11, 2014, at 5:26 AM, Dawes, Peter, Vodafone Group <Peter.Dawes@vodafone.com> wrote:

> Hi Hadriel,
> My confusion with 3.1 came from the mixture of introductory description (the UAS half of a B2BUA does not technically need to inspect the Max-Forwards header) with normative specification in the same paragraph, but I accept that the MUST makes it clear which is which. The other comments related to potentially shortening the text a little and not to errors or ambiguity.
> 
> Thanks for the answers, I have no more comments.
> 
> Peter
> 
> -----Original Message-----
> From: Hadriel Kaplan [mailto:hadriel.kaplan@oracle.com] 
> Sent: 10 March 2014 21:25
> To: Dawes, Peter, Vodafone Group
> Cc: straw@ietf.org
> Subject: Re: [straw] WGLC for draft-ietf-straw-sip-traceroute-01.txt
> 
> 
> On Mar 10, 2014, at 3:33 PM, Dawes, Peter, Vodafone Group <Peter.Dawes@vodafone.com> wrote:
> 
>> Hi Hadriel,
>> Apologies for not being very clear with my comment about lack of clarity :-)
>> 
>> The draft describes behaviour for a UAC, B2BUA, and UAS. Is the paragraph below from clause 3.1 an instruction to a B2BUA implementer on how to process Max-Forwards or a warning that some B2BUAs will cause the mechanism to fail?
> 
> It's an instruction - it has the word "MUST", and it says right at the end:
>  ...This document also
>  requires such behavior in order to succeed, therefore a B2BUA
>  supporting the traceroute mechanism defined in this document MUST
>  also comply with [draft-loop-detection].
> 
> 
>> A couple of other small questions, is the first sentence "As currently defined in [RFC3261], the UAS half of a B2BUA does not technically need to inspect the Max-Forwards header field value for received requests - only Proxies do. " needed?
> 
> Yes, I think it sets the context for this being a change in behavior.
> 
> 
>> Also, regarding complying with [draft-loop-detection] does a B2BUA need to do more than "inspect the value in order to prevent loops, as well as copy and decrement the value as if it were a Proxy"? If so it would be good to say something like ", therefore a B2BUA supporting the traceroute mechanism defined in this document MUST also comply with the Max-Forwards behaviour and all other procedures in [draft-loop-detection]"
> 
> Isn't that synonymous with "MUST also comply with [draft-loop-detection]"?
> 
> I must be missing something obvious to you in reading that paragraph, because it sounds like you're saying it doesn't say X when it says X to me.
> :)
> 
> -hadriel
> 
> 
>> -----Original Message-----
>> From: Hadriel Kaplan [mailto:hadriel.kaplan@oracle.com] 
>> Sent: 10 March 2014 17:09
>> To: Dawes, Peter, Vodafone Group
>> Cc: straw@ietf.org
>> Subject: Re: [straw] WGLC for draft-ietf-straw-sip-traceroute-01.txt
>> 
>> Hi Peter,
>> sorry for the delay in responding to this!
>> comments inline...
>> 
>> On Dec 17, 2013, at 7:04 AM, Dawes, Peter, Vodafone Group <Peter.Dawes@vodafone.com> wrote:
>> 
>>> I think the draft text in clause 3.1 Processing a Received Max-Forwards Header Field (lines 206 - 208)] "As currently defined in [RFC3261], the UAS half of a B2BUA does not technically need to inspect the Max-Forwards header field value for received requests - only Proxies do." should be clearer in terms of what the implementer actually has to do. 
>> 
>> It says:
>>  As currently defined in [RFC3261], the UAS half of a B2BUA does not
>>  technically need to inspect the Max-Forwards header field value for
>>  received requests - only Proxies do.  This behavior was updated by
>>  [draft-loop-detection], such that a compliant B2BUA needs to both
>>  inspect the value in order to prevent loops, as well as copy and
>>  decrement the value as if it were a Proxy.  This document also
>>  requires such behavior in order to succeed, therefore a B2BUA
>>  supporting the traceroute mechanism defined in this document MUST
>>  also comply with [draft-loop-detection].
>> 
>> 
>> How is that not clear?
>> 
>> 
>>> You replied that "...I think it is in fact in doubt.  I know of many B2BUAs which do in fact decrement max-forwards. (and I think they're right to)". So what does the implementer do? Be happy that they might not need to change too much? Make sure all of their B2BUAs decrement Max-Forwards whether they will loopback media or not? Be aware that if they don't want their B2BUA to decrement Max-Forwards then they can't use this mechanism? Something else?
>> 
>> See above.
>> 
>> -hadriel
>> 
> 
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