[Nsi-wg] Immediate/Advance reservation (Re: NSI conf call minutes)

Mon Apr 12 06:21:51 CDT 2010

Hi John-   (I'm back...:-)

These are all very important points, and regarding the temporal 
scheduling and timing issues these concern me too.    IMO, the solutions 
we have discussed do not sit well with folks generally speaking - I know 
I feel like we have created a complex monster to deal with what the user 
believes to be a relatvely simple request: I need a connection now, 
please.  (Meaning: I need a connection by any means you have currently 
avalaible and I only want to know if you have it completed or that your 
can't do it at the moment.)

I will contact a couple of you to catch up on the current state of the 
discussion before I comment more. 

Thanks
Jerry

John Vollbrecht wrote:
> 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 at aist.go.jp]
>> Sent: 09 April 2010 09:04
>> To: Jeroen van der Ham
>> Cc: nsi-wg at 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 at 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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