Subject: Re: [NSIS] Receiver Initiated Reservation - Teardown

From: Andrew McDonald <[email-masked]>
Date: Mon, 28 Aug 2006 10:12:27 +0100

Hi Bernd, Elena,

Checking through some old e-mails, I came across this:

Bernd Schloer wrote:
> Elena Scialpi wrote:
 >> Bernd Schloer wrote:
>>>
>>> RSVP has two types of teardown-messages: PathTear and ResvTear. The 
>>> QoS NSLP is only allowed to send a RESERVE towards the QNR. How can a 
>>> receiver initiated reservation be torn down? The QNR is not allowed.
>>
>> I think that a reservation can be torn down by a RESERVE message ( 
>> with TEAR flag set) from both, QNI and QNR, entity.
>> Only RESERVE for resource reservation MUST travel from QNI to QNR and 
>> not in the opposite direction.
>>
> That would make sense. But section 5.4.1 says:
> 
>    RESERVE messages MUST only be sent towards the QNR.
> 
> In my opinion this includes also RESERVE messages with set T-Flag.

I'm in agreement with Bernd on what the current text says - The 
intention is that this applies both to the reservation-making RESERVE 
and the reservation-removing RESERVE (i.e. it applies to all RESERVE 
messages). The reasoning behind this was to do with authorization - if 
only the peer QNE that established the reservation can manipulate it 
(change it, remove it, etc), it makes the reasoning simpler about 
whether a RESERVE is authorized or not.

I think that the situation being envisaged is not unique to receiver 
initiated reservations. A similar situation could apply with a pair of 
sender initiated reservations for a bidirectional flow, where one end 
decides to terminate the user data session and so cause the reservation 
to also be torn down. Some end-to-end communication will be performed as 
part of the user data flow, which would provide the information to the 
other signalling endpoint necessary for it to decide to tear down the 
reservation from its end. In the past, I believe, we've considered that 
sufficient when looking at this particular issue.

regards,

Andrew

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