Re: [Teas] Network slicing framework : Issue #2 : How many connectivity matrices in a slice?
Xufeng Liu <xufeng.liu.ietf@gmail.com> Thu, 07 October 2021 20:42 UTC
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From: Xufeng Liu <xufeng.liu.ietf@gmail.com>
Date: Thu, 07 Oct 2021 16:42:39 -0400
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To: "Joel M. Halpern" <jmh@joelhalpern.com>
Cc: TEAS WG <teas@ietf.org>
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Subject: Re: [Teas] Network slicing framework : Issue #2 : How many connectivity matrices in a slice?
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In this case, there is slice-a for traffic class A with slo-A, and slice-b for traffic class B with slo-B. There is another base slice-c under both slice-a and slice-b. The slo-C on slice-c limits the total traffic. Thanks, - Xufeng On Thu, Oct 7, 2021 at 3:27 PM Joel M. Halpern <jmh@joelhalpern.com> wrote: > Do you consider the use case where there is a ingress limit on the total > traffic thata a consumer can send across a set of traffic classes, and > there are separate SLOs for those separate classes, to be a case we need > to address? > > It seems legitimate to me. And multiple connectivity matrices in a > slice seems the natural way to address it. > > Yours, > Joel > > On 10/7/2021 3:19 PM, Xufeng Liu wrote: > > I would like to have: > > - Support of one connectivity matrix per slice is mandatory > > > > But not have: > > - Support of more than one connectivity matrix per slice is in the > > architecture > > but is optional to implement > > > > Allowing the second option would unnecessarily complicate the user > > experience, without providing any additional capabilities, as commented > > below in-line. > > > > Thanks, > > - Xufeng > > > > On Tue, Sep 28, 2021 at 1:17 PM Adrian Farrel <adrian@olddog.co.uk > > <mailto:adrian@olddog.co.uk>> wrote: > > > > Hi Tarek, ____ > > > > __ __ > > > > You’ve called out some good cases for consideration.____ > > > > __ __ > > > > >> For example, a consumer may want a slice that is ultra-low > latency, > > and they may know that they want to send traffic from A to B, from A > > to C and multicast from D to A, B, and C.____ > > > > [TS]: I agree that creating multiple matrices (per service type) to > > address the above usecase makes sense and makes it simpler for the > > IETF slice service consumer to reference a single ultra-low latency > > slice. ____ > > > > * In such case, wouldn’t the service type (unicast/multicast) be > > enough to differentiate what connectivity matrix the traffic > > would pick – as opposed to requiring an additional ID (one for > > identifying slice, and one for identifying the connectivity > > matrix).____ > > > > [AF] There are two points to consider:____ > > > > * How the customer specifies the connectivity supported by the > > slice____ > > * How the implementation identifies the connectivity matrix and > > places traffic on the matrix____ > > > > So, in this case, there is no traffic flow anticipated from A to D > > or from B to C, etc. Thus, it is not good enough to specify the set > > of endpoints, it is also important to specify the connectivity > > between those endpoints so that the provider knows that there is no > > need to provision resources for connectivity that will not be > used.____ > > > > How the connectivity is actually implemented in the network (and > > even how traffic is policed, and how SLIs are measured) is up to the > > provider/implementer. If (this may be a big if) the traffic is > > simply routed, then it would not be necessary for the provider to > > match traffic to a connectivity matrix – they would simply route it, > > and in this case the provider’s network is unaware of the > > connectivity matrix. On the other hand, if some form of > > connection-oriented approach is taken then while the traffic is > > simply routed/classified at the ingress endpoint, there is some > > relationship between connection matrix and reserved resources (think > > of MPLS-TE). ____ > > > > If, in all this, there is no policing at the ingress endpoint, then > > admission control or use of resources in the transit network may > > need to be more carefully associated with the “flow” i.e. the > > connectivity matrix.____ > > > > __ __ > > > > * Does it make sense to have two “same type” connectivity matrices > > (for example, two p2p connectivity matrices for two connections > > between A and B)? I can see two cases:____ > > o If the two parallel connections (between A and B) have same > > SLOs, then why not aggregate into 1 connection/connectivity > > matrix?____ > > > > [AF] I think that if they have the same SLOs and the same > > connectivity, then you would probably have them as a single matrix > > (summing the bandwidth, but keeping the latency constant, for > > example). But you would not be required to do that. Again, it might > > depend on policing and how you want to manage the SLOs. For example, > > two parallel connectivity matrices from A to B each with a required > > throughput of X Mbps is not the same as one matrix from A to B with > > throughput 2X – this is because A is not the traffic source: traffic > > comes from upstream of the slice endpoint and may originate at > > different applications, hosts, or sites.____ > > > > __ __ > > > > Again consider MPLS-TE LSPs. You might, for convenience and > > scalability tunnel two parallel LSPs down one hierarchical LSP. The > > capacity of the H-LSP is the sum of the children, but the children > > have their own rights!____ > > > > __ __ > > > > Of course, in this case, the SLOs might only be identical today. > > They might be available to change tomorrow, and in that case it is a > > lot easier to have two separate (“parallel”) matrices.____ > > > > __ __ > > > > o If the two parallel connections (between A and B) have > > different SLOs, then are they still same slice? wouldn’t it > > be better to just have them in two different slices?____ > > > > [AF] This is the nub of the question. It is a multi-dimensional > > problem (because of the many SLOs) with a hierarchy of ownership. > > Customer àslice àmatrix. You end up with the same number of leaves > > in the tree, but the branches are at different places. And, further, > > you could hang the SLOs at any point in the tree (for example at the > > matrix as currently proposed, or at the slice). > > > > [Xufeng]: If the slices can be organized hierarchically, the original > > desired behavior can be achieved: in addition to the three separate > > slices described earlier, we can have a base (underlay) slice that > > supports all these three slices. The base slice can serve as a construct > > containing all three connectivity matrices, without introducing > > additional connectivity-matrix-id. > > > > ____ > > > > __ __ > > > > A part of this debate is: suppose two connectivity matrices have 98% > > agreement on their SLOs, but one SLO is fractionally different. Does > > that require two slices?____ > > > > __ __ > > > > But please be aware that describing the architecture is not > > engineering the YANG model! With the current proposal, I would > > probably still write a YANG model that had default SLOs per > > customer, with variations per slice, with additional variations per > > matrix.____ > > > > __ __ > > > > And also recall that how the network protocol implementations choose > > to implement adherence to SLOs is open for discussion. If they need > > some form of indicator/index to tell them what to do, this value > > will be “mapped” from {customer, slice, matrix} and it is not > > important (to the architecture) how that mapping is performed.____ > > > > __ __ > > > > o it is not clear in such case what creating two matrices “of > > same type” is solving? Is it loadbalance, redundancy, ?____ > > > > [AF] It is not clear to me that anyone (except for you :-) has > > raised the case of two parallel matrices with identical SLOs. I am > > not convinced that they would be used (although my throughput > > example, above) is a possible case. But equally important to me is > > the question: why would we prevent this when it comes for free?____ > > > > __ __ > > > > Cheers,____ > > > > Adrian____ > > > > __ __ > > > > *From: *Teas <teas-bounces@ietf.org <mailto:teas-bounces@ietf.org>> > > on behalf of Adrian Farrel <adrian@olddog.co.uk > > <mailto:adrian@olddog.co.uk>> > > *Date: *Monday, September 27, 2021 at 12:29 PM > > *To: *'TEAS WG' <teas@ietf.org <mailto:teas@ietf.org>> > > *Subject: *[Teas] Network slicing framework : Issue #2 : How many > > connectivity matrices in a slice?____ > > > > Hi, > > > > Igor raised this especially in the context of how traffic is > > identified for association with a connectivity matrix that belongs > > to a slice. > > > > Consider the definition of connectivity matrix in the current draft > > and as discussed in issue #1. > > > > A consumer may want multiple connectivity matrices in their > > "contract" with the provider. In the example with four edge nodes > > (A, B, C, D), their may be traffic that flows between some edges, > > but not between others. > > > > For example, a consumer may want a slice that is ultra-low latency, > > and they may know that they want to send traffic from A to B, from A > > to C and multicast from D to A, B, and C. > > > > It is, of course, possible to express this as three separate slices. > > And this is perfectly acceptable. We must not make any definitions > > that prevent this from being the case. > > > > However, it seems likely that the consumer (and the operator) would > > prefer to talk about "the consumer's low latency slice". That is, to > > bundle these three connections into one construct. However, they are > > distinctly different connections and must be understood as such. > > Indeed, they may have some different SLOs associated (for example, > > A-B may require more bandwidth than A-C). > > > > By allowing (but not mandating) multiple connectivity matrices in a > > single slice service, we facilitate this administrative group. > > > > One could also imagine (but I do not pre-judge the network slice > > service YANG model definition) a default set of SLOs that apply to > > all connectivity matrices in a slice, and specific modified SLOs per > > connectivity matrix. > > > > Now, to Igor's point. This is about how traffic arriving at an edge > > (say a PE) is mapped to the correct connection. I promised a Venn > > diagram, but words are easier 😊 > > > > If we take the model of a port-based VPN, then one approach might be > > to map the (virtual or physical) port number or VLAN ID to the > > network slice. But clearly (and this was Igor's point) this doesn't > > identify the connectivity matrix if there is more than one matric > > per slice. > > > > A solution I offered is that the VLAN ID could identify {slice, > > connectivity matrix}. At that PE, for a given AC to a CE, it is > > necessary to expose with a separate VLAN ID for each {slice, > > connectivity matrix}. That does not mean: > > - we need a global unique identifier for each connectivity matrix > > - we need a per-PE unique identifier for each connectivity matrix > > > > I am *very* cautious about discussing potential technology solutions > > because they are just that. It is not the business of a framework to > > direct solutions work. But I provide this example solution just to > > show that it is possible. > > > > Consider also, how traffic is placed on LSPs or on SFCs. The answer > > is that there is some form of classification performed at the head > > end. In many cases, this is as simple as examination of the > > destination address (traffic is "routed" onto the LSP). In other > > cases there is deeper analysis of the 5-tuple and even other packet > > parameters. Often this will be enough, but when there are multiple > > "parallel" connections to the same destination, some form of choice > > must be made: how that choice is made can be configured in an > > implementation, and may include looking at additional information > > (such as a VLAN ID) passed from the consumer. > > > > Note that the identity of the connectivity matrix is not needed > > anywhere except at the ingress edge node. It may be that the > > connectivity matrix is mapped to some internal network structure > > (such as an LSP) and that that provides an implicit identification > > of the connectivity matrix, and it may be that a solution technology > > chooses to keep an identifier of the connectivity matrix with each > > packet, but that is not a requirement of the architecture. > > > > I think what I have said is: > > - Support of one connectivity matrix per slice is mandatory > > - Support of more than one connectivity matrix per slice is in the > > architecture > > but is optional to implement > > - There are ways that a protocol solution could achieve this function > > - I have heard some voices asking for the association of multiple > > connectivity > > matrices with a single slice > > - I have not heard anyone providing examples of harm this would cause > > > > Please discuss. > > > > Adrian > > > > > > > > > > _______________________________________________ > > Teas mailing list > > Teas@ietf.org <mailto:Teas@ietf.org> > > https://www.ietf.org/mailman/listinfo/teas > > <https://www.ietf.org/mailman/listinfo/teas>____ > > > > _______________________________________________ > > Teas mailing list > > Teas@ietf.org <mailto:Teas@ietf.org> > > https://www.ietf.org/mailman/listinfo/teas > > <https://www.ietf.org/mailman/listinfo/teas> > > > > > > _______________________________________________ > > Teas mailing list > > Teas@ietf.org > > https://www.ietf.org/mailman/listinfo/teas > > >
- [Teas] Network slicing framework : Issue #2 : How… Adrian Farrel
- Re: [Teas] Network slicing framework : Issue #2 :… John E Drake
- Re: [Teas] Network slicing framework : Issue #2 :… Ogaki, Kenichi
- Re: [Teas] Network slicing framework : Issue #2 :… Krzysztof Szarkowicz
- Re: [Teas] ***フリーメール*** Re: Network slicing frame… Ogaki, Kenichi
- Re: [Teas] ***フリーメール*** Re: Network slicing frame… Krzysztof Szarkowicz
- Re: [Teas] ***フリーメール*** Re: Network slicing frame… Adrian Farrel
- Re: [Teas] ***フリーメール*** Re: Network slicing frame… Krzysztof Szarkowicz
- Re: [Teas] ***フリーメール*** Re: Network slicing frame… Adrian Farrel
- Re: [Teas] ***フリーメール*** Re: Network slicing frame… Ogaki, Kenichi
- Re: [Teas] ***フリーメール*** Re: Network slicing frame… Krzysztof Szarkowicz
- Re: [Teas] ***フリーメール*** Re: Network slicing frame… Krzysztof Szarkowicz
- Re: [Teas] ***フリーメール*** Re: Network slicing frame… John E Drake
- Re: [Teas] ***フリーメール*** Re: Network slicing frame… Ogaki, Kenichi
- Re: [Teas] Network slicing framework : Issue #2 :… Tarek Saad
- Re: [Teas] Network slicing framework : Issue #2 :… Tarek Saad
- Re: [Teas] Network slicing framework : Issue #2 :… Krzysztof Szarkowicz
- Re: [Teas] Network slicing framework : Issue #2 :… Adrian Farrel
- Re: [Teas] ***フリーメール*** Re: Network slicing frame… Krzysztof Szarkowicz
- Re: [Teas] Network slicing framework : Issue #2 :… Igor Bryskin
- Re: [Teas] Network slicing framework : Issue #2 :… Krzysztof Szarkowicz
- Re: [Teas] Network slicing framework : Issue #2 :… Jeff Tantsura
- Re: [Teas] ***フリーメール*** Re: ***フリーメール*** Re: Netw… Ogaki, Kenichi
- Re: [Teas] ***フリーメール*** Re: ***フリーメール*** Re: Netw… Krzysztof Szarkowicz
- Re: [Teas] Network slicing framework : Issue #2 :… mohamed.boucadair
- Re: [Teas] Network slicing framework : Issue #2 :… Dongjie (Jimmy)
- Re: [Teas] Network slicing framework : Issue #2 :… John E Drake
- Re: [Teas] Network slicing framework : Issue #2 :… Kiran Makhijani
- Re: [Teas] Network slicing framework : Issue #2 :… Xufeng Liu
- Re: [Teas] Network slicing framework : Issue #2 :… Joel M. Halpern
- Re: [Teas] Network slicing framework : Issue #2 :… John E Drake
- Re: [Teas] Network slicing framework : Issue #2 :… Xufeng Liu
- Re: [Teas] Network slicing framework : Issue #2 :… John E Drake
- Re: [Teas] Network slicing framework : Issue #2 :… jmh.direct
- Re: [Teas] Network slicing framework : Issue #2 :… Xufeng Liu
- Re: [Teas] Network slicing framework : Issue #2 :… Xufeng Liu
- Re: [Teas] Network slicing framework : Issue #2 :… John E Drake
- Re: [Teas] Network slicing framework : Issue #2 :… Xufeng Liu
- Re: [Teas] Network slicing framework : Issue #2 :… Xufeng Liu
- Re: [Teas] Network slicing framework : Issue #2 :… John E Drake
- Re: [Teas] Network slicing framework : Issue #2 :… t petch