Hi Radak- First - I am not necessarily against a change in the protocol...just not now. Lets finish version 2 - no more new changes. Wrap up what we have and get the specification out the door. Any new changes, especially to the protocol, require careful consideration. E.g. the state machines need to be reviewed - again. I suggest it be pushed to v3 for discussion. Second - on the technical aspects, if anything (including the PA) interupts the active circuit *for any reason* without prior acknowledgement by the RA, that constitutes an outage...as far as the user is concerned. The Release primitive allows the RA to inform the PA that the resources can now be taken out of service [temporarilly] without breaking contract. Third - the Release allows the user to tell the network that "I am not using this capacity *right now*" - and implicitly allow the network to use that capacity for something else- like best effort traffic, or maintenance, etc., without the interruption causing an alarm. This is IMO *very* useful. As yet another real use case: - a user reserves and tests a connection before it is actually needed (say for an important video presentation), the user can Release the connection until the required time, and then re-provision it with the confidence that the circuit engineering will be the same and thus the performance ought to be the same as tested - same latency, same path, same loss specifications, etc. Fourth - we do not have a means currently for the PA to request a Release of the RA (i.e. *up* the tree.) This would be the means by which a leaf node network - having no visibility to the upstream and down stream Connection segmentations could pass a Release request up the tree allowing all the agents in the tree to be properly notified/consulted. As for alternate use of the resources during a Released window, this is probably where we have not offered guidance. But the user has no expectation that his traffic will flow or resume until he has re-provisioned the Connection and received a ProvisionConfirm. During the released period, the resource can indeed be used for something else - how the "system" keeps track of this is an implementation issue. There is one proviso: that those resources are locked in some fashion to the Connection and will be available to re-provision when requested. When the user issues the re-Provision, the user should NOT get a reject based upon resource availability...but the [re-]provision might not be immediate - it might take a while as maintenance operations are concluded, or other traffic is groomed away...but the Provision() primitve already is acknowledged to be highly variable in provisioning times. Finally, the current Release should probably include an optional re-provision time. Or a duration for the Release. THis would allow the PA to know when the user will again need the circuit to be active and functioning properly. Sort of an auto-restart for re-provisioning.:-) So the Release seems to me to be quite useful - though it might want some additional features like the PA->RA capability above, or a duration, and perhaps some guidance on what is expected of the Connection performance parameters across a Release. So, IMO any changes to the protocol requires careful consideration. I do not think we should rush this or take this discussion formally now. I suggest that we make no change and leave Release as-is for version 2. We put it on the list of v3 issues and have the discussion then. Jerry On 2/28/13 5:26 AM, Radek Krzywania wrote:
Jerry, If you have maintenance, the resources are unavailable. This is either scheduled and system should not book resources in that time, or forced by situation which is a failure for NSI (cancel/reroute/reprovision). This must be simple. There is a lot of questions from non-NSI people on what is the release and what is it purpose. The only case I can imagine is when the link is shared by provisioned and best effort traffic, so releasing connection can speed up best-effort, no-guaranteed traffic for a while. Reprovisioning will decrease the bandwidth for best-effort traffic without much damage. How likely is that to happen? Is the regular IP traffic so high we need to clear on-demand connections whenever possible? If I booked the resources, I am paying for them despite of the fact I am using them currently or not. Release gives some flexibility and may have some use cases, but IMHO for sake of simplicity we should make it optional or get rid of it at all.
Best regards Radek
----------------------------------------------------------- Radek Krzywania e-mail: radek.krzywania@man.poznan.pl phone: +48 61 850 2526
Network R&D
Poznan Supercomputing and Networking Center Noskowskiego 12/14 61-704 Poznan Poland
-----Original Message----- From: nsi-wg-bounces@ogf.org [mailto:nsi-wg-bounces@ogf.org] On Behalf Of Jerry Sobieski Sent: Thursday, February 28, 2013 12:14 AM To: John MacAuley Cc: nsi-wg@ogf.org Group Subject: Re: [Nsi-wg] Release command
Hi John -
I know a number of implementations that have not implemented the Modify() command - and probably won't either. So lets remove it also. If you really want to simplify the protocol and SMs, get rid of Modify. :-)
but seriously... Use cases and historical context:
Many connections will be in service over weeks, months or years. The idea is to be able to drop the circuit from its "in service" state without releasing the reserved resources back to the available pool and risk those resources being allocated to other Connections. The potential for new reservations locking out or substantially changing the existing reservation was deemed unacceptable. The circuit could be re-provisioned as long as it was still within the reservation window.
The use case would be for periodic maintenance where the circuit would be affected but where the interruption is expected and should not constitute an error. Another use case can be where the reserved resources in one domain for a connection need to be modified (say a link is upgraded from 10 G to 100 G) - but the upstream or downstream domain resources should not be released back to the availability pool. When the circuit data plane is broken there is no way to guaranty the privacy or security or reliability of user data - the Release enables the user to halt traffic and allow the circuit to be fiddled with.... The other domains should not generate alarms or otherwise act as if the connection is fully functional - but its not an error either. Release is not just a cosmetic command.
I do not think there was an intention to modify the circuit as-built characteristics during a release - Indeed, I think the intent was to simply communicate to all NSAs in the tree that the data plane can be interupted without causing an "outage" or triggering alarms all up and down the path. So while we probably did not document in sufficient detail what the user would experience as result of a release and re-provision, the sentiment was that the circuit would be "essentially" the same after reprovisioning. (e.g. "The expected performance characteristics should be the same before and after a Release.") I do recall the discussion where we stipulated that the data flow *should* be actively blocked during a Release since to admit user data without confirmation that all segments were in service would pose a security and reliability flaw to the performance guarantees. However, I do not think anything about curtailing the flow at ingress made it into the spec.
A) Why is this difficult to implement?
B) To my recollection, the Release() was never considered an "optional" primitive in terms of implementation, just that it could be skipped in the life cycle protocol sequence thus allowing an active circuit to go directly to a Cancel state without passing through Released. (This means only that the protocol can skip the Release action in cases where it is not needed - not that it is an optional primitive in an NSI CS implementation.) So if it is not implemented I would consider it an incomplete implementation.
C) What behaviour are you thinking the Release is or is not doing? Or doing incorrectly?
This seems like a new proposal when we are trying to curtail any additional changes - particularly major changes which I think this is. I think we should retain the Release() primitive in its current form for v2. WE can revisit the issue in v3 ?
just my thoughts.. Jerry
Peoples,
I understand the usefulness of having a release command from a networking
Would it be possible for people to provide their customer use cases for
On 2/27/13 12:38 PM, John MacAuley wrote: perspective, but I know a number of implementations are not supporting it at the moment (and some have no intention of supporting it). With my new "lets make the state machine as simple as possible attitude" I started to wonder what is the customer use case for this command? Chin had one where someone wanted to keep their reservation, but wanted to free up bandwidth for others to use. This is an interesting use case, but not the behaviour of the current command as documented. Removal of this command can significantly simplify the protocol and state machine. this command? I am wondering if it is truly needed, or perhaps, we have the incorrect behaviour defined.
Thank you, John _______________________________________________ nsi-wg mailing list nsi-wg@ogf.org https://www.ogf.org/mailman/listinfo/nsi-wg
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