- Nsi-wg - lists.ogf.org

Fwd: NSI service instantiation or provisioning signalling
by John Vollbrecht 13 Apr '10

13 Apr '10

I apparently didn't send this to the NIS group by accident. Begin forwarded message: > From: ""Joan A. García-Espín"" <jage(a)i2cat.net> > Date: April 13, 2010 5:05:49 AM GMT-04:00 > To: John Vollbrecht <jrv(a)internet2.edu> > Subject: Re: NSI service instantiation or provisioning signalling > > Hi John, > > I am very sorry but somehow I missed your email. My apologises. > >> A- Some points that I think we agree on (I could be wrong) - >> 1) An NSA will have a state machine (or equivalent). That state >> machine will have a set of states including reserved and active. >> The issue we are talking about has to do with going between the >> reserved and active state. > Right, agreed. > >> 2) A triggering event of some sort will be what causes the NSA to >> change states (and perhaps do some other things). > Right also. > >> B- The discussion of ways to instantiate a connection seems to me >> to have aspects >> 1) who generates the signal to the state machine >> 2) what other actions does the signal cause to happen > Exactly, depending on who signals the instantiation, the service > workflow may be affected in one way or another. The discussion is > about which option is the best for being included in v1.0. > >> C- There are questions about how to signal state between NSAs >> 1) is there a "master" that initiates the signal or is it >> independently done >> 2) if one NSA fails how do others know and keep in sync > Right. > >> Of A, B and C - I hope we agree about A. >> I think B maybe needs some discussion, but I think we could agree >> pretty quickly >> C is harder, and I think needs more discussion of how NSAs keep >> state. Some of this might be put off till after A and B are done >> and in the doc (in my opinion). > > Right also > > fully aligned! > -- > Joan A. García-Espín > CTX, i2CAT Foundation > > > > > > El 06/04/2010, a las 23:59, John Vollbrecht escribió: > >> I am a bit confused by the discussion on this. So I suggest >> abstracting out the issues bit to see where we agree or disagree. >> >> A- Some points that I think we agree on (I could be wrong) - >> 1) An NSA will have a state machine (or equivalent). That state >> machine will have a set of states including reserved and active. >> The issue we are talking about has to do with going between the >> reserved and active state. >> 2) A triggering event of some sort will be what causes the NSA to >> change states (and perhaps do some other things). >> >> B- The discussion of ways to instantiate a connection seems to me >> to have aspects >> 1) who generates the signal to the state machine >> 2) what other actions does the signal cause to happen >> >> C- There are questions about how to signal state between NSAs >> 1) is there a "master" that initiates the signal or is it >> independently done >> 2) if one NSA fails how do others know and keep in sync >> >> Of A, B and C - I hope we agree about A. >> I think B maybe needs some discussion, but I think we could agree >> pretty quickly >> C is harder, and I think needs more discussion of how NSAs keep >> state. Some of this might be put off till after A and B are done >> and in the doc (in my opinion). >> >> Does this make any sense? >> >> John >> >> >> >> On Apr 6, 2010, at 9:57 AM, Joan A. García-Espín wrote: >> >>> Hi Jerry, thanks for your comments! >>> >>> I've extracted some of your comments and added my view (just for >>> avoiding large in-line discussion). >>> >>>> By definition, #3 above is out of scope for the NSI protocol. >>>> If some other agent (or control plane) wants to initiate the >>>> provisioning, it does so thru a mechanism that is defined within >>>> the NSI protocol. I expect #1 will suffice if some external >>>> agent needs to kick it off. >>> >>> As for #3, I was thinking of an scenario where the NRM >>> automatically (internally) triggers the provisioning. In this >>> case, the service plane could consider letting the NSA in charge >>> of that NRM polling it for the reservation status, and notifying >>> the rest of NSAs in the provisioning tree later on (upwards >>> approach). >>> >>>> Hmm...I think I have to disagree strongly. >>> >>> Good :) >>> >>>> When we expect these NSAs to start based on independent clocks >>>> and without verification that the service/control plane >>>> associated with this connection is even functioning, I think we >>>> introduce a myriad of complexities that need to be discussed in >>>> detail. Mostly, blind provisioning is different in a tree >>>> structured service plane than in OSCARS or AutoBahn or a GMPLS >>>> style service plane. We need to understand these issues better >>>> before we wave our hands and say its simple. >>> >>> My view: the Service Plane is an abstract layer where NSAs >>> interact for allowing network service provisioning (we all agree >>> on this). One of the key factors here is that NSI aims at >>> supporting not only reservations (time dimension is desirable >>> here), but also advance reservations or book ahead (time dimension >>> is compulsory). Therefore, time synchronisation is something that >>> we know, sooner or later, will appear on stage. The NSI cannot >>> force implementers to use a given time sync method, but we can >>> recommend its use as a way for precise service provisioning and >>> for lowering the rate of unsatisfied services (error handling >>> gains importance). >>> >>>> - The start time may be weeks or months after the request was >>>> reserved. How do we know if the service tree for that connection >>>> is still functioning? For instance, if the service tree is >>>> broken, how do we expect the provisioning to complete? (At least >>>> with requester initiated provisioning we get a request sent down >>>> the tree that verifies the service tree is still in place.) >>> >>> NS status query is a primitive, afaik. An NSA can use it for >>> periodically/punctually verify the service tree. Which NSA? I'd >>> say the one who first initiated the service provisioning (root NSA). >>> >>>> - With independent provisioning, i.e. independent state changes, >>>> we don't have any means of determining the state of the >>>> connection unless we communicate that state up and down the >>>> service tree. We know what our state is, but we have no way of >>>> predicting the state of our parent/child NSAs and so we have no >>>> way to validate that the protocol is functioning properly. >>> >>> For the sake of a good functioning, people implementing option #3 >>> must implement a robust notification mechanism. I agree with you >>> that independent and not-notified changes at a given point in the >>> tree produce undesired situations. I don't think we have to worry >>> about future implementations, just provide a flexible interface >>> for doing so. >>> >>>> - If we flood Provision() requests up and/or down the tree to >>>> communicate to our parent/children NSAs that we auto-induced a >>>> state transition for a connection, how do we handle collisions of >>>> Provision() requests? Are there any race conditions or hysteresis? >>> >>> Again, I think this is an implementation problem and is useful for >>> the people working on error handling. >>> >>>> -If we send Provision() requests up the tree...is that any >>>> different than sending them down the tree? Are they handled any >>>> differently? If not, would it simplify the protocol if only the >>>> root initiated the Provision() requests based on a timer? i.e. >>>> does having all NSAs independently kick off timers cause >>>> unnecessary complexity? >>> >>> We faced this problem in the Phosphorus project time ago, when >>> designing Inter-Domain Broker communication protocol for our >>> Harmony tool. After long discussions, we concluded this could be >>> easily handled by a proper security infrastructure. Any NSA should >>> be able to know who its neighbours are and what are they allowed >>> to request. In the case of managing a GMPLS control plane with >>> manual instantiation of the connection at the UNI, we needed a >>> mechanism to notify the service plane the connection was >>> provisioned, and thus we implemented the notification service. >>> Alternatively, if notification not available, we could use a >>> polling mechanism and latter flooding of the reservation state >>> among all service plane entities involved. I agree that it adds >>> complexity, but I mentioned it basing on a use case from Phosphorus. >>> >>>> - if we do have a protocol that handles mid-tree flooding of >>>> state changes, could this also be useful for the release() >>>> function or for possible error or failure mode handling scenarios? >>> >>> In my mind, I was not considering mid-tree, only changes flooded >>> from root NSA or network-attached NSA. >>> >>>> - What happens if the wall clocks in the NSA are not "adequately" >>>> synchronized. Can we assume that wall clock synchronization is >>>> a non-issue? If not, what does "adequate" mean in this context? >>> >>> As I mentioned before, since we are considering calendars to be >>> used in a per network (in general, per resource) for advance >>> reservations, we should recommend that time sync is used, at least. >>> >>>> - How does a requester determine if/when a connection is in- >>>> service? Do we simply fire data at it until we see it pop out >>>> the other end? How do we know that? What can we say >>>> definitively about the connection state form the user's service >>>> perspective as we move from reserved to inservice..? (Even a few >>>> milliseconds could result in megabytes of information being >>>> leaked out or lost from a connection. This is both very poor >>>> service quality as well as a security risk.) >>> >>> This problem is present at *any* provision strategy and should be >>> discussed. The trivial solution (inject and expect it be >>> transmitted) is something that can cause severe data losses, as >>> you mention. From my past experience, when using a provisioning >>> system, one cannot be 100% sure the path is provisioned until data >>> plane is tested (i.e. ping). Assuming the network hardware works >>> well, we need the NRM to control path set up. Then we have several >>> options, but the most typical are (i) implement a way the NRM >>> tells its parent NSA the connection is UP, and the let the NSA >>> propagate this information along the service tree upwards or (ii) >>> implement a polling loop in the NSA in charge of the NRM, until >>> "connection UP" is obtained, and proceed with the flooding. In any >>> of these cases, "connection UP" messages from NRM should be >>> aggregated for building up "path segment UP", until a whole "path >>> UP" is ready. Then, the original requester can be notified. Please >>> note these are only some options, many others can be designed. NSI >>> protocol should not stick to any of them, but consider them for >>> making NSI flexible enough (=> will ease adoption). >>> >>>> - Is it adequate to have provisioned() segments in-service before >>>> all segments are in-service? Does this cause a timing issue in >>>> the tree that could result in mis-routed data? Do we need to >>>> stipulate some atomic function that allows data to begin flowing >>>> that is different than simply configuring the path? >>> >>> This can happen, given that networks cooperating in the connection >>> provisioning are independent. Thinking on this, I get the >>> impression we need some message from the service plane to the app >>> where we say the whole path is in-service. >>> >>>> Finally, I assert that there is no significant legacy application >>>> base that should dictate how NSI protocol functions just so that >>>> they don't have to change. If there are some requirements that >>>> those application need that NSI needs to support, ok...but I >>>> don't think its a good idea to make a future protocol act in some >>>> way just because thats the way we've always done it. (That logic >>>> says lets not change anything...:-) >>> >>> I fully agree Jerry, hope you did not understand otherwise, sorry >>> if I expressed wrongly myself. >>> My comments were two-fold: >>> - First, we should make the first release of the NSI implement >>> the options we think are easier to adopt, but in any case limit it >>> to them. >>> - Second, future-proofed NSI protocol needs firstly to be present- >>> proof. Bad early adoption means hard future adoption. >>> >>>> My proposal: >>>> 1) I think we should do a "requester initiated provisioning" >>>> request down the tree as a first simplest provisioning initiation >>>> process. 2a) If we can work through the mid-tree messaging and >>>> state transition in a prompt manner, we could include that also >>>> in V1.0, but I think it may be more complex. 2b)A simple interim >>>> solution would be to have the first PA that sees a "provider >>>> initiated provisioning" request to assume that responsibility and >>>> passes a "requester initiated provisioning" request to all >>>> children. Then that first PA sends provision() requests down the >>>> tree to start the process just as with a requester initiated >>>> provisioning. >>> >>> If we go for requester-initiated provisioning, we need to control >>> both reservation and provisioning calendars, don't we? I mean, >>> reservation requests will only serve as a "medium access control" >>> mechanism, purely signalling, not really influencing in the >>> provisioning. In this case, the user has to mind about both >>> reservation and instantiation. >>> What about the time lapse between user requesting provisioning and >>> data plane effectively up...? >>> >>>> I know I can be a bit brusque with some of this - hope it all >>>> make sense and was not too curt. >>> >>> >>> It all makes sense. Please mind I always want to broaden the >>> applicability of the NSI and to strength its flexibility, since >>> for me they're the key for easy adoption (of course, without >>> running to generic). >>> >>> My best regards, >>> -- >>> Joan A. García-Espín >>> CTX, i2CAT Foundation >>> >>> >>> >>> >>> >>> El 02/04/2010, a las 22:39, Jerry Sobieski escribió: >>> >>>> Hi Joan- >>>> >>>> I have some reservations to what you suggest below...please let >>>> me know what you think... >>>> >>>> Joan A. García-Espín wrote: >>>>> >>>>> <<Some long discussions on how best to initiate the >>>>> ‘provisioning’ phase of operation. Several methods were >>>>> discussed, but none agreed: >>>>> >>>>> 1. Provisioning initiated by signal i.e. a message on the >>>>> NSI interface. >>>>> 2. Provisioning initiated by a timer local to the provider NSA >>>>> 3. Provisioning initiated by a signal not on the NSI >>>>> interface e.g on a separate control plane >>>>> >> >>>> By definition, #3 above is out of scope for the NSI protocol. >>>> If some other agent (or control plane) wants to initiate the >>>> provisioning, it does so thru a mechanism that is defined within >>>> the NSI protocol. I expect #1 will suffice if some external >>>> agent needs to kick it off. >>>>> >>>>> My vision is that ANY of the procedures should be supported in >>>>> the NSI. Therefore, NSI must implement the required flag(s) in >>>>> the service characterisation or specific signalling message(s) >>>>> for automatic activation, but all of them might be considered >>>>> optional for allowing either one or the other model to be used >>>>> by requester. >>>> The remaining #1 and # 2 amount to "Requester initiated" and >>>> "Provider initiated". And either could be initiated via a timer >>>> expiring, or by some other event in a work flow, etc. It seems >>>> to me the *simplest* thing to do is to have the requester >>>> initiate the provisioning. This is just like we have always done >>>> it with UNIs or RSVP or any other protocol, so it is well >>>> understood. Because it is initiated at the root of the request >>>> tree, it flows down the tree and back up in a very determinitic >>>> fashion. We know when each segment is fully provisioned. There >>>> is no special handling, it does not add complexity to have the >>>> provision request slide down the request tree just like the >>>> reservation() request did initially. >>>> So, it is my proposal that we have at least #1 in version1: the >>>> connection is provisioned on requester sending a "provision()" >>>> request/command to the provider. And when a >>>> "ProvisionComplete()" message is received, the connection is >>>>> >>>>> From a pragmatic viewpoint, option 2 is the best candidate for >>>>> NSI release 1.0, since does not assume that either the requester >>>>> app or the control plane have the capability to perform an >>>>> automatic activation/instantiation of the connection. Basically, >>>>> this means that legacy compatibility is ensured in early >>>>> implementations, although having to implement time sync in the >>>>> NSA. This is a good point in general because: (i) most of the >>>>> apps/middlewares are not used to deal with generic GMPLS UNI and >>>>> thus don't implement automatic signalling in the app <-> control >>>>> plane interface, and secondly (ii) not all control planes or >>>>> provisioning/management systems implement calendars and >>>>> consequently cannot natively support advance reservations (that >>>>> would be emulated at the service plane). >>>> Hmm...I think I have to disagree strongly. >>>> When we expect these NSAs to start based on independent clocks >>>> and without verification that the service/control plane >>>> associated with this connection is even functioning, I think we >>>> introduce a myriad of complexities that need to be discussed in >>>> detail. Mostly, blind provisioning is different in a tree >>>> structured service plane than in OSCARS or AutoBahn or a GMPLS >>>> style service plane. We need to understand these issues better >>>> before we wave our hands and say its simple. >>>> >>>> Here is a list of some issues in no particular order: >>>> >>>> - The start time may be weeks or months after the request was >>>> reserved. How do we know if the service tree for that connection >>>> is still functioning? For instance, if the service tree is >>>> broken, how do we expect the provisioning to complete? >>>> (At least with requester initiated provisioning we get a request >>>> sent down the tree that verifies the service tree is still in >>>> place.) >>>> >>>> - With independent provisioning, i.e. independent state changes, >>>> we don't have any means of determining the state of the >>>> connection unless we communicate that state up and down the >>>> service tree. We know what our state is, but we have no way of >>>> predicting the state of our parent/child NSAs and so we have no >>>> way to validate that the protocol is functioning properly. >>>> >>>> - If we flood Provision() requests up and/or down the tree to >>>> communicate to our parent/children NSAs that we auto-induced a >>>> state transition for a connection, how do we handle collisions of >>>> Provision() requests? Are there any race conditions or hysteresis? >>>> -If we send Provision() requests up the tree...is that any >>>> different than sending them down the tree? Are they handled any >>>> differently? If not, would it simplify the protocol if only the >>>> root initiated the Provision() requests based on a timer? i.e. >>>> does having all NSAs independently kick off timers cause >>>> unnecessary complexity? >>>> >>>> - if we do have a protocol that handles mid-tree flooding of >>>> state changes, could this also be useful for the release() >>>> function or for possible error or failure mode handling scenarios? >>>> >>>> - What happens if the wall clocks in the NSA are not "adequately" >>>> synchronized. Can we assume that wall clock synchronization is >>>> a non-issue? If not, what does "adequate" mean in this context? >>>> >>>> - How does a requester determine if/when a connection is in- >>>> service? Do we simply fire data at it until we see it pop out >>>> the other end? How do we know that? What can we say >>>> definitively about the connection state form the user's service >>>> perspective as we move from reserved to inservice..? (Even a few >>>> milliseconds could result in megabytes of information being >>>> leaked out or lost from a connection. This is both very poor >>>> service quality as well as a security risk.) >>>> >>>> - Is it adequate to have provisioned() segments in-service before >>>> all segments are in-service? Does this cause a timing issue in >>>> the tree that could result in mis-routed data? Do we need to >>>> stipulate some atomic function that allows data to begin flowing >>>> that is different than simply configuring the path? >>>> >>>> We do not have currently any notion of what these NSI protocol >>>> requirements entail. >>>> >>>> I do not differentiate between a timer event kicking off >>>> provisioning or some other non-calendar related event (say a work >>>> flow task completing) that defines the kickoff point. Whatever >>>> event occurs generates a Provision() request within that NSA >>>> which causes the state machine to transition. >>>> Finally, I assert that there is no significant legacy application >>>> base that should dictate how NSI protocol functions just so that >>>> they don't have to change. If there are some requirements that >>>> those application need that NSI needs to support, ok...but I >>>> don't think its a good idea to make a future protocol act in some >>>> way just because thats the way we've always done it. (That logic >>>> says lets not change anything...:-) >>>> >>>> My proposal: >>>> 1) I think we should do a "requester initiated provisioning" >>>> request down the tree as a first simplest provisioning initiation >>>> process. 2a) If we can work through the mid-tree messaging and >>>> state transition in a prompt manner, we could include that also >>>> in V1.0, but I think it may be more complex. 2b)A simple interim >>>> solution would be to have the first PA that sees a "provider >>>> initiated provisioning" request to assume that responsibility and >>>> passes a "requester initiated provisioning" request to all >>>> children. Then that first PA sends provision() requests down the >>>> tree to start the process just as with a requester initiated >>>> provisioning. >>>> >>>> I know I can be a bit brusque with some of this - hope it all >>>> make sense and was not too curt. >>>> >>>> Glad påsk! >>>> Jerry >>>>> >>>>> Best regards and have a nice Easter holidays, >>>>> -- >>>>> Joan A. García-Espín >>>>> Network Technologies Cluster (CTX) >>>>> i2CAT Foundation >>>>> C/ Gran Capità 2-4, office 203, Nexus I building >>>>> 08034 Barcelona, Catalonia (Spain) >>>>> >>>>> T: +34 93 553 2518 >>>>> F: +34 93 553 2520 >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>> >> >

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Re: [Nsi-wg] Immediate/Advance reservation (Re: NSI conf call minutes)
by Gigi Karmous-Edwards 13 Apr '10

13 Apr '10

I completely agree with Radek's statements below. Compared to today's time to get a circuit... many users will be extremely happy with an "ASAP type" of response. Gigi Radek Krzywania wrote: > Hi, > I tried to catch up the discussion, hope I did not missed anything. > What is hard for me to understand is why are we trying to define measurable parameters (connection activation time) basing on non-deterministic, immeasurable parameters (guard time). Even if we measured how much time it takes to reserve and activate connection in a domain, we have only statistical view on how much time it MAY (SHOULD) take. Any change to the network, NSI architecture, HW, or even SF may extend this time unexpectedly, without prior notification. This is not something we can measure (or we need to do that constantly, changing guard time value every time, which in fact does not solve everything). IMHO we can't promise something we could not prove or be sure of. I am happy to measure guard time, add safe value (e.g. res + activation takes 4 minutes, + 2 minutes safe time = 6 minutes) and say to we SHOULD deliver a connection in less than 6 minutes. If we say we MUST provide it in less than 6 minutes, we have an issue. > I am rather more familiar with the option where connection is delivered as soon as possible, which means each domain performs reservation, then signalling is initialized immediately after resources are booked. Does user care if he gets it now = current time, or = current time + "gurad time or whatever"? I suppose not. If I want a circuit now, I expect to get it ASAP, which does not means it's deterministic. I am fine with knowledge I will get it around 6 minutes (statistically), but I must be immediately notified about activation. If we want to go into time details, we will get into very funny things like GPS synchronisation between users, NSA agents, networks, and domains. This is not a real-time system, not everything is deterministic, and not everything can be guaranteed. We can reconsider naming of the service, and change it from immediate to ASAP. > I am not sure if we should focus on this small issue, while facing resources guarantee in advance reservation mode. Try to guarantee there anything for 100% in 2 months time period:) Even if you assume no network/HW failures. > > Best regards > Radek > > ________________________________________________________________________ > Radoslaw Krzywania Network Research and Development > Poznan Supercomputing and > radek.krzywania(a)man.poznan.pl Networking Center > +48 61 858 20 28 http://www.man.poznan.pl > ________________________________________________________________________ > > > >> -----Original Message----- >> From: nsi-wg-bounces(a)ogf.org [mailto:nsi-wg-bounces@ogf.org] On Behalf Of >> Artur Barczyk >> Sent: Tuesday, April 13, 2010 10:11 AM >> To: Inder Monga >> Cc: nsi-wg(a)ogf.org; Guy Roberts >> Subject: Re: [Nsi-wg] Immediate/Advance reservation (Re: NSI conf call >> minutes) >> >> Hi Inder, >> >> I see, thanks for this clarification. >> >> I still think we are introducing an artificial decision step here, which >> will just be confusing to the end-user (and make the whole system >> more complex), and I still wonder about the necessity of it. >> Please see in-line: >> >> >> On 04/12/2010 11:15 PM, Inder Monga wrote: >> >>> Hi All, >>> >>> I feel there is a lot of confusion, so let me try to explain my >>> case/understanding. >>> >>> 1. Guard-time: >>> This concept was proposed for Advanced Scheduling only. This can be a >>> default value and it does not have to be an "exact" measurement of >>> provisioning times. It only handles path computation and reservation >>> times across domains. >>> >>> What does it mean to a user? >>> A user CANNOT ask for a advanced reservation connection with Tstart < >>> Tnow + Guard-time. If a user asks with a Tstart lower that Tnow + >>> Guard-time, the scheduled request is rejected outright. >>> >> Imagine I try to make a connection "NOW", and it gets refused after >> N minutes due to lack of resources. Then I try "2 minutes from now", and >> it gets rejected straight off. >> We shouldn't aim at having expert users who would understand this. >> I think the system should behave in the same (and deterministic) way, >> independent of what the user states in reservation time. >> (Btw - that the reservation and provisioning time might vary does not >> make it less deterministic.) >> >> >>> With an ADvanced Scheduling function, provisioning initiation can happen >>> from both the user or the provider. >>> >>> 2. On-Demand Service: In my opinion, Guard-time does not prevent an >>> On-Demand service as specified by Jerry. They co-exist. >>> An on-demand service, with Tstart = ASAP can be implemented very easily. >>> The service starts when the "provisioning complete" message is received >>> by the user. If the user does not receive that message, it continues to >>> wait. >>> >> Exactly what I was aiming at - but the same logic can apply to any time >> between "NOW" and the guard time, or doesn't it? >> All you need to do, if the start time is reached before the reservation >> is complete, to wait for the latter. >> >> >>> Does this make more sense? >>> >>> I will answer specifics below. >>> >>> >> [...] >> >> >>>> What I meant is that if that time has passed by the time the provider >>>> NSA gets notified of the reservation acceptance along the path, it >>>> should proceed directly to provisioning. >>>> >>> In advanced reservation, the open question is what should a domain do if >>> Tstart comes, and it has not got a reservation complete or provision >>> message? Should it delete the connection or provision its own set of >>> resources? Chin and I include this case in the error recovery document >>> to be published soon. >>> >> No, no - simply wait for the reservation to complete. Only then will >> you know if it succeeded in the first place. >> >> IMO, the provisioning and reservation systems cannot be completely >> decoupled. The provisioning stage should actually never be reached >> until a reservation is complete. It is dependent on the outcome of the >> path computation as well as resource reservation. Never go to provisioning >> before you know you can have the resources. >> >> >>>> You have to do this anyway, to protect against the guard time being >>>> set too short. In which case you can just as well set the guard time to 0. >>>> >>>> That's just common sense, IMO, what it means when I would ask for >>>> immediate >>>> circuit provisioning. "Please give it to me as soon as you're able to, >>>> I'm waiting." >>>> >>>> The thing not to forget is that someone can ask for a circuit not only >>>> "now", >>>> >>> I think the "now" case is actually, "as soon as possible" - which is the >>> on-demand case. Then it just waits for the right message from the >>> Provider Agent before it knows the connection is available to be used. >>> >> Yes, absolutely agree - that's a discussion terminology, which I'd be >> happy to change :-) >> However, we need to be precise on what we mean. An "ASAP" reservation, >> from a user's point of view, could mean really "any time possible, starting >> from now", i.e. also in 2 hours, if the resources will only then become >> available. >> I am not sure BoD does mean that. >> Will in such a case a BoD reservation be converted into a scheduled one? >> >> >>>> but "a minute from now", which would lead to the same problem if the >>>> time to >>>> >>> A minute from now actually becomes a "scheduled connection" and there is >>> where the problem really starts. >>> >> I am sorry I have missed large parts of this discussion, being kept off with >> other workload. Sorry if I am coming back to things which might be obvious >> to you by now. >> But I do not really understand where the problem really is. >> You mention the provisioning system to have to decide what to do >> if the reservation step is not complete - but I think the right design >> decision >> would be that the system should never actually be in such a state. >> (Sorry, I am falling into thinking in terms of state machines here, but >> well, >> that's what I start to believe would be good here.) >> >> Is there other reasons? >> >> Cheers, >> Artur >> >> >>> I feel we should support both Advanced Reservation with guard-time and >>> On-demand connection service. >>> >>> Inder >>> >>> >>>> process the reservation is longer than a minute (as it most probably >>>> will be >>>> in the next future). >>>> So the "now" string as in your option 2) would only work for a singular >>>> subset of the >>>> problem. >>>> >>>> Cheers, >>>> Artur >>>> >>>> >>>> >>>>> Guy >>>>> >>>>> >>>>> >>>>> -----Original Message----- >>>>> From: Artur Barczyk [mailto:Artur.Barczyk@cern.ch] >>>>> Sent: 12 April 2010 17:28 >>>>> To: nsi-wg(a)ogf.org <mailto:nsi-wg@ogf.org> >>>>> Subject: Re: [Nsi-wg] Immediate/Advance reservation (Re: NSI conf >>>>> call minutes) >>>>> >>>>> Hi, >>>>> >>>>> I think guard time is a shaky concept, as who can tell how long it should >>>>> be - it can/will depend on the number of domains the circuit >>>>> contains, the >>>>> speed of each reservation/provisioning system as well as the load on the >>>>> system, and will be variable over time (hoping for faster >>>>> reservation/provisioning >>>>> systems in the future). >>>>> >>>>> But: if in step 5, the "wait for start time" means t_start <= t_current, >>>>> then the >>>>> provider will immediately pass on to provisioning. >>>>> What needs to be done however is to have the duration of the reservation >>>>> reflect the time difference between desired start time and the effective >>>>> one. >>>>> >>>>> I am sure I am missing something..? >>>>> >>>>> Cheers, >>>>> Artur >>>>> >>>>> >>>>> >>>>> On 04/12/2010 11:12 AM, Guy Roberts wrote: >>>>> >>>>>> Jeroen, >>>>>> >>>>>> Yes, that is correct. But the mechanism will be the same for >>>>>> advance reservations, just a later start time. >>>>>> >>>>>> Guy >>>>>> >>>>>> -----Original Message----- >>>>>> From: Jeroen van der Ham [mailto:vdham@uva.nl] >>>>>> Sent: 12 April 2010 08:19 >>>>>> To: Guy Roberts >>>>>> Cc: John Vollbrecht; nsi-wg(a)ogf.org <mailto:nsi-wg@ogf.org> >>>>>> Subject: Re: [Nsi-wg] Immediate/Advance reservation (Re: NSI conf >>>>>> call minutes) >>>>>> >>>>>> To sum this up, this describes a situation where there is no prior >>>>>> reservation and provisioning is started immediately because the >>>>>> startTime is meant as a "now"? >>>>>> >>>>>> Jeroen. >>>>>> >>>>>> >>>>>> On 09/04/2010 18:56, Guy Roberts wrote: >>>>>> >>>>>>> John, >>>>>>> >>>>>>> My thinking of how it could work is as follows (though the details >>>>>>> are really part of the protocol definition group's work): >>>>>>> >>>>>>> StartTime= time when the provisioning is begun. This is the only >>>>>>> possible meaning for StartTime since we have no way of knowing how >>>>>>> long the provisioning will take in advance of the provisioning >>>>>>> being performed. i.e provisioning completion time is >>>>>>> non-deterministic. For consistency as an asynchronous system, the >>>>>>> completion of provisioning (in-service) is pushed by the NRM to the >>>>>>> Provider which in turn sends this to the Requestor as a notification. >>>>>>> >>>>>>> >>>>>>> Locally initiated provisioning: >>>>>>> 1. The Requester NSA creates a request with a start time >>>>>>> (StartTime). StartTime= NSAs current time + Requester guard time. >>>>>>> Eg 12:00pm + 5 minutes = 12:05pm. >>>>>>> 2. Provider validates the start time as being at least the provider >>>>>>> guard time away from now. (note requester and provider guard times >>>>>>> could be a little different to allow for transmission delay of request) >>>>>>> 3. Provider begins the reservation process (12:01pm) >>>>>>> 4. Provider completes the reservation (12:02pm) >>>>>>> 5. Provider waits for the startTime (12:05pm) >>>>>>> 6. Provider starts provisioning locally (12:05pm) >>>>>>> 7. Provider waits for confirmation of provisioning from NRM (12:06pm) >>>>>>> 8. Provider sends a notification to the requestor NSA to notify >>>>>>> that the connection is in-service (12:06pm) >>>>>>> >>>>>>> Provisioning signalled by Requester: >>>>>>> 1. The Requester NSA creates a request with a start time >>>>>>> (StartTime). StartTime= NSAs current time + Requester guard time. >>>>>>> Eg 12:00pm + 5 minutes = 12:05pm. >>>>>>> 2. Provider validates the start time as being at least the provider >>>>>>> guard time away from now. (note requester and provider guard times >>>>>>> could be a little different to allow for transmission delay of request) >>>>>>> 3. Provider begins the reservation process (12:01pm) >>>>>>> 4. Provider completes the reservation (12:02pm) >>>>>>> 5. Provider waits for the startTime (12:05pm) >>>>>>> 6. Provider waits for the signal to provision (12:10pm) >>>>>>> 7. Provider initiates provisioning of the Connection (12:10pm) >>>>>>> 7. Provider waits for confirmation of provisioning from NRM (12:11pm) >>>>>>> 8. Provider sends a notification to the requestor NSA to notify >>>>>>> that the connection is in-service (12:11pm) >>>>>>> >>>>>>> >>>>>>> Guy >>>>>>> >>>>>>> >>>>>>> >>>>>>> -----Original Message----- >>>>>>> From: John Vollbrecht [mailto:jrv@internet2.edu] >>>>>>> Sent: 09 April 2010 17:28 >>>>>>> To: Guy Roberts >>>>>>> Cc: John Vollbrecht; Tomohiro Kudoh; Jeroen van der Ham; >>>>>>> nsi-wg(a)ogf.org <mailto:nsi-wg@ogf.org> >>>>>>> Subject: Re: [Nsi-wg] Immediate/Advance reservation (Re: NSI conf >>>>>>> call minutes) >>>>>>> >>>>>>> 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(a)ogf.org <mailto: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(a)uva.nl <mailto: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. >>>>>>>>> >>>>>>>> >>>>>>>> _______________________________________________ >>>>>>>> nsi-wg mailing list >>>>>>>> nsi-wg(a)ogf.org <mailto:nsi-wg@ogf.org> >>>>>>>> http://www.ogf.org/mailman/listinfo/nsi-wg >>>>>>>> _______________________________________________ >>>>>>>> nsi-wg mailing list >>>>>>>> nsi-wg(a)ogf.org <mailto:nsi-wg@ogf.org> >>>>>>>> http://www.ogf.org/mailman/listinfo/nsi-wg >>>>>>>> >>>>>>> _______________________________________________ >>>>>>> nsi-wg mailing list >>>>>>> nsi-wg(a)ogf.org <mailto:nsi-wg@ogf.org> >>>>>>> http://www.ogf.org/mailman/listinfo/nsi-wg >>>>>>> >>>>>>> >>>>>>> >>>>>> _______________________________________________ >>>>>> nsi-wg mailing list >>>>>> nsi-wg(a)ogf.org <mailto:nsi-wg@ogf.org> >>>>>> http://www.ogf.org/mailman/listinfo/nsi-wg >>>>>> >>>> -- >>>> Dr Artur Barczyk >>>> California Institute of Technology >>>> c/o CERN, 1211 Geneve 23, Switzerland >>>> Tel: +41 22 7675801 >>>> _______________________________________________ >>>> nsi-wg mailing list >>>> nsi-wg(a)ogf.org <mailto:nsi-wg@ogf.org> >>>> http://www.ogf.org/mailman/listinfo/nsi-wg >>>> >>> --- >>> Inder Monga http://100gbs.lbl.gov >>> imonga(a)es.net <mailto:imonga@es.net> http://www.es.net >>> (510) 499 8065 (c) >>> (510) 486 6531 (o) >>> >>> >> -- >> Dr Artur Barczyk >> California Institute of Technology >> c/o CERN, 1211 Geneve 23, Switzerland >> Tel: +41 22 7675801 >> _______________________________________________ >> nsi-wg mailing list >> nsi-wg(a)ogf.org >> http://www.ogf.org/mailman/listinfo/nsi-wg >> > > _______________________________________________ > nsi-wg mailing list > nsi-wg(a)ogf.org > http://www.ogf.org/mailman/listinfo/nsi-wg >

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NSI conf call tomorrow
by Guy Roberts 13 Apr '10

13 Apr '10

Hi All, The following is dial-in information for Wednesday's NSI call: Time: 7:30 PDT 10:30 EDT, 15:30 BST, 16:30 CEST, 23:30 JST Call: +1-734-615-7474 (Please use if you do not pay for Long Distance) or +1-866-411-0013 (toll free US/Canada Only) Enter access code: 0155180 Agenda: 1. Review action points from last meeting 2. Advance/immediate reservations 3. STPs 4. Other issues Guy ------------------------------------------------------------------------------------------------------------------ Guy Roberts, Ph.D Network Engineering & Planning DANTE - www.dante.net<http://www.dante.net/> Tel: +44 (0)1223 371 316 City House, 126-130 Hills Road Cambridge, CB2 1PQ, UK ------------------------------------------------------------------------------------------------------------------

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Advanced vs. immediate reservation
by Guy Roberts 13 Apr '10

13 Apr '10

Hi All, I think I agree with Inder's analysis that we can support two types of connection request, immediate and advanced, as long as these two services have some constraints which I have summarized in this table: Service type startTime endTime State change State change Res->Sch Sch->Prov Immediate string: '0' >startTime asap Signalled only Advanced >Now + guardTime >startTime <startTime Signalled & local All other state changes are fixed: I -> Res: occurs as soon as the connection request is received Prov -> IS: occurs as soon as provisioning has been completed by NRM IS -> Rel: occurs after Cancel request has been processed. Note 1: '<' means before, '>' means after Note 2: A Connection has following states: Idle (I), Reserving (Res), Scheduled (Sch), Provisioning (Prov), In-service (IS), Released (Rel). The question for v1.0 is do we need to support the immediate mode or can we use near-immediate mode where we set the startTime close to 'now'? Guy ------------------------------------------------------------------------------------------------------------------ Guy Roberts, Ph.D Network Engineering & Planning DANTE - www.dante.net<http://www.dante.net/> Tel: +44 (0)1223 371 316 City House, 126-130 Hills Road Cambridge, CB2 1PQ, UK ------------------------------------------------------------------------------------------------------------------

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immediate and advanced reservations in v1.0
by Guy Roberts 12 Apr '10

12 Apr '10

Hello All, Based on recent discussions I see two competing models for solving immediate type connection requests. Option 1: In the first solution (based on a proposal by Inder and described by Kudoh-san) a start-time of Now+GuardTime is used, where GuardTime is a hold-off time to prevent race conditions. We allow provisioning to be signalled either by the requester NSA and locally by the provider NSA. The guard-time is chosen by policy and is the (worst-case) time taken for reservation to complete. In this model, there is no distinction between near-immediate and advanced, the difference is only in the start time provided by the requester. The problem with option 1 is that it could be very slow - in large systems the guard-time could be several minutes. Option 2: An alternative solution to this problem (proposed by Jerry) would be to use the 'now' string in the start time. To prevent race conditions, instigation of provision must be signalled from the Requester. This would ensure that the provisioning phase is only begun once all reservations are completed. The down-side with this proposal is that it would preclude support for locally instigated provisioning based on the Providers timer. In this model the immediate reservation is distinguished by putting the 'now' string in the start time field. If you believe that we have a requirement to support local instigation of provisioning, then this will make option 2 unworkable. Too quickly gather feedback on these options, I have prepared the following web survey, please complete if you have an opinion on this topic: http://www.surveymonkey.com/s/R8KGD9F Guy ------------------------------------------------------------------------------------------------------------------ Guy Roberts, Ph.D Network Engineering & Planning DANTE - www.dante.net<http://www.dante.net/> Tel: +44 (0)1223 371 316 City House, 126-130 Hills Road Cambridge, CB2 1PQ, UK ------------------------------------------------------------------------------------------------------------------

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new/modified NSI requirements
by Guy Roberts 09 Apr '10

09 Apr '10

Hello all, Following on from today's NSI discussions, the following new NSI requirements are proposed. Could you please take a look and let me know if you are happy to accept these as agreed requirements? Guy ---------------- Not UNI like: R1.1.10 The NSI architecture must not force services requests to originate from any specific NSA. (i.e. this is different to MPLS UNI which only allows connections requests that terminate on the node associated with the UNI) Provisioning complete notification: D2.1.12a The Notify function must support a notification to indicate that provisioning has been completed. (this is to allow local timer based initiation of provisioning to be notified to the Requester NSA) Provisioning initiation methods: D2.2.6 Connection provisioning is initiated in two possible ways: 1: When a Requestor NSA signals to the Provider NSA. 2: Once a scheduled resource reaches the start time. (I guess this implies the need for some way of indicating which type of initiation of provisioning should be used) Advanced reservation and near-immediate reservation method: D2.2.13 A requester NSA will create advanced reservation type Connection requests by setting a start time and end time. D2.2.14 A requester NSA will be able to request near-immediate Connections by setting a start time soon after the current time, subject to guard time limits. Note that the guard time concept is added here to allow validation of start times that are near-to-present-time. This makes start times more deterministic and reduces race conditions and other problems during connection creation -Guy Roberts 4/7/10 4:56 PM D2.2.15 A Provider NSA when scheduling a Connection request will perform a guard time test on the start time as follows: If the start time is less than current time + guard time then the connection request will be rejected. D2.2.16 The guard time will be agreed based on local policy and managed by the NSA. ------------------------------------------------------------------------------------------------------------------ Guy Roberts, Ph.D Network Engineering & Planning DANTE - www.dante.net<http://www.dante.net/> Tel: +44 (0)1223 371 316 City House, 126-130 Hills Road Cambridge, CB2 1PQ, UK ------------------------------------------------------------------------------------------------------------------

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minutes for today's NSI conf call
by Guy Roberts 07 Apr '10

07 Apr '10

Minutes from today's call can be found here: http://forge.gridforum.org/sf/go/doc15954?nav=1 Guy ------------------------------------------------------------------------------------------------------------------ Guy Roberts, Ph.D Network Engineering & Planning DANTE - www.dante.net<http://www.dante.net/> Tel: +44 (0)1223 371 316 City House, 126-130 Hills Road Cambridge, CB2 1PQ, UK ------------------------------------------------------------------------------------------------------------------

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tomorrow's NSI call
by Guy Roberts 06 Apr '10

06 Apr '10

Hi All, The following is dial-in information for Wednesday's NSI call: Time: 7:30 PDT 10:30 EDT, 15:30 BST, 16:30 CEST, 23:30 JST Call: +1-734-615-7474 (Please use if you do not pay for Long Distance) or +1-866-411-0013 (toll free US/Canada Only) Enter access code: 0155180 Agenda: 1. Review action points from last meeting 2. Review Architecture deliverable feedback 3. Is architecture deliverable v1.0 ready for submission? 4. NSI service instantiation or provisioning signalling 5. Other issues Guy ------------------------------------------------------------------------------------------------------------------ Guy Roberts, Ph.D Network Engineering & Planning DANTE - www.dante.net<http://www.dante.net/> Tel: +44 (0)1223 371 316 City House, 126-130 Hills Road Cambridge, CB2 1PQ, UK ------------------------------------------------------------------------------------------------------------------

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NSI requriements document
by Guy Roberts 31 Mar '10

31 Mar '10

http://docs.google.com/Doc?docid=0AZTOJNVUoixhZGZ4cjRiemtfMzQyaGZtOG4yZ2o&h… ------------------------------------------------------------------------------------------------------------------ Guy Roberts, Ph.D Network Engineering & Planning DANTE - www.dante.net<http://www.dante.net/> Tel: +44 (0)1223 371 316 City House, 126-130 Hills Road Cambridge, CB2 1PQ, UK ------------------------------------------------------------------------------------------------------------------

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FW: submission for NSI arch
by Guy Roberts 31 Mar '10

31 Mar '10

Hello all, Please find attached submission on NSI inter-network topology model from John Vollbrecht. Guy -----Original Message----- From: John Vollbrecht [mailto:jrv@internet2.edu] Sent: 30 March 2010 17:52 To: Guy Roberts; Jerry Sobieski; Tomohiro Kudoh; Joan Antoni Garcia Espin Cc: John Vollbrecht Subject: submission for NSI arch Guy and all -- This took longer than I had hoped to finish. Please distribute it to the NSI group as a whole if you think it appropriate. I include Joan on this because I think (hope) he will be interested in the authorization/topology issues in section 2- especially since he has volunteered to do something with the concept of "owning". Attached is a submission for NSI protocol spec. I am not sure how it fits with what exists now, but I think it could be in a introduction or overview section. A couple notes - I did not use the term STP. I tried, but it didn't seem to fit, and I still have a problem with understanding its precise definition in different circumstances. This can be changed once we sort this out. I tried to separate the part that deals with multi-NSA infrastructures from the basic interface description. I think this works, but maybe not. I added some description of the interaction between NSA authorization and transport topology. I hope this is a good start and can be useful in separating discussions of topology and authorization which probably should happen in a limited way before releasing the recommendation I included some high level description of paths. I think (hope) this is good intro to some of the stuff Jerry has written. As a interesting note, in the path discussion it describes path as Path == [ingress (-egress, ingress)* - egress] It is interesting to note that the term (-egress, ingress) might be considered a Point or edge (or even a link) between networks I am most interested in reactions and comments. Thanks John

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