I am still a bit confused. Perhaps someone could do a timing diagram like the one Tomohiro did a while ago when we were discussing 2 phase commits. I will try to explain my confusion. My understanding has been that we agreed that provisioning would never be done without prior reservation. So it would seem that the question being discussed is "what is the time being requested in a reservation". If the reservation succeeds then provisioning can happen. It seems to me one question is how to define the start time being requested. The options seem to be that is is either 1) the time the circuit is actually provisioned and ready to use or 2) the time that provisioning of the circuit starts. In one case the previous connection may terminate sooner by the guard time and in the latter it may start later by the guard time. If it is (1) then a connection scheduled for now must have been started at [now - (start time)]. A second question is whether is is possible to request a connection that starts "now". This implies reserving a connection and initiating it as soon as it is reserved. Assume that start time is when provisioning a circuit starts (case 2 above). It seems that main issue with this is whether the time to reserve a connection is longer than the requestor is willing to wait. The time it takes depends on how many NSAs are "chained" to satisfy the request and how long each NSA takes to reserve the connection. This time is "authorization time" not guard time as I understand it. There is another issue with defining authorization as "now" instead of a specific time. The problem is that each NSA in a chain will think authorization happens at a slightly different time. I am not sure how important this is - it doesn't seem too important to me, but perhaps I am wrong. If provisioning starts after the reservation is complete, then everything should be reserved, if at a slightly different time. ---------------------------------- I think Guy is suggesting that start time is when provisioning starts (case 2) above. That seems simplest to me. I am not sure the provisioning time is important, and if not I would think it good to include "immediate" reservation John On Apr 9, 2010, at 11:15 AM, Guy Roberts wrote:
Tomohiro,
In this case, only some parts of inter-network connection will be provisioned.
Right, I forgot about this reason - it is a good point. Again, I think we are not complicating things too much if we have a rule that the Requester NSA cannot send a start time sooner than now+guardtime.
I think we can solve the chain issue by not forcing any value for the guard time. This can be a policy decision to suit the service type, equipment and number of networks involved.
Guy
-----Original Message----- From: Tomohiro Kudoh [mailto:t.kudoh@aist.go.jp] Sent: 09 April 2010 09:04 To: Jeroen van der Ham Cc: nsi-wg@ogf.org Subject: Re: [Nsi-wg] Immediate/Advance reservation (Re: NSI conf call minutes)
Hi Jeroen,
There is a problem for inter-network connection. During the discussions in some calls, the problem of synchronizing networks (managed by different NSAs) was discussed.
If you use the "now" type request for inter-network connection (without complicated coordination), the actual provisioning time of networks may be different. Moreover, some networks may provision resources before some other networks reply to the request, and such networks might deny the request. In this case, only some parts of inter-network connection will be provisioned.
The guard time is one of the simple solutions to solve this problem. I understand there can be multiple ways to cope with this, but all of them will introduce some complication to some part (note that we decided not to use 2PC for the v1.0). This is a design choice matter.
Regards,
Tomohiro
On Thu, 08 Apr 2010 09:27:59 +0200 Jeroen van der Ham <vdham@uva.nl> wrote:
On 07/04/2010 15:02, Tomohiro Kudoh wrote:
If a requester wants resources to be provisioned as soon as possible, it can set the start time parameter in a advance request to: (current time + guard time + a certain time required for message delivery).
In this way, immediate provisioning can be requested by an advance reservation request.
The procedure above seems overly complicated and if I really am pressed for time, and I miscalculate the (current time + guard time + delivery time) by a few seconds. Denying the request means that I have to do it all over again, making me even more pressed for time.
Why not keep things simple and always interpret a start time in the past as "now" ? (provided the end-time is in the future too) Would there be any problems associated with that?
Jeroen.
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