Re: [Bier] What is Slice Aggregate?
Adrian Farrel <adrian@olddog.co.uk> Tue, 09 November 2021 19:41 UTC
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From: Adrian Farrel <adrian@olddog.co.uk>
To: 'Lizhenbin' <lizhenbin@huawei.com>, teas@ietf.org
Cc: bier@ietf.org, apn@ietf.org
Date: Tue, 09 Nov 2021 19:41:00 -0000
Organization: Old Dog Consulting
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Subject: Re: [Bier] What is Slice Aggregate?
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Hi Robin, Answering as pen-holder for draft-ietf-teas-ietf-network-slices, but providing a definitive answer for something that might need WG consensus. In line. From: BIER <bier-bounces@ietf.org> On Behalf Of Lizhenbin Sent: 09 November 2021 13:35 To: teas@ietf.org; apn@ietf.org Cc: bier@ietf.org Subject: [Bier] What is Slice Aggregate? Hi authors of draft-ietf-teas-ietf-network-slices, The authors of the draft draft-zzhang-bier-slicing-and-differentiation-00 mentioned in the draft: " [I-D.bestbar-teas-ns-packet] introduces the notion of Slice Aggregate which comprises of one of more IETF network slice traffic streams. A Slice Aggregate is identified by a Slice Selector (SS), and packets carry the SS so that associated forwarding treatment or S-PHB (Slice policy Per Hop Behavior - the externally observable forwarding behavior applied to a specific packet belonging to a slice aggregate) - can be applied along the path. " " The authors of this document believe that the IETF Network Slicing framework, when augmented by the Slice Aggregate, addresses the APN problem domain very well. " According to the past discussion, we think the slice aggregate means the underlay slice, that is the new terminology "network resource partition". If so, the Slice Selector should be the identifier of the network resource partition. But according to the draft-zzhang-bier-slicing-and-differentiation-00, the slice aggregate can be augmented to address the APN problem. In the recently published draft draft-li-apn-header-00, the APN attribute is defined including the APN ID (user group/application group) the packet belongs to , the Intent and APN parameters applied to the packet. It is apparent these attributes are totally different from the identifier of the underlay slice. Can you clarify the following about the slice aggregate: 1. What is slice aggregate? Is it the underlay network slice, the APN attribute-like parameters, both or other identifier? Or can it be all possible identifiers to identify a flow? I have no specific definition for a "slice aggregate." There is some text on the concept of "aggregating slices" in Section 6.5 of draft-ietf-teas-ietf-network-slices-05. But this is fairly high-level and conceptual acknowledgement that there may be some form of scaling required so that a network is not required to maintain state on every slice service it supports. As far as "identifiers in the underlay network" is concerned, I think that is entirely a choice for the solution. The solution mechanism needs to be able to deliver the high-level functionality that results in the slice service. I think it is likely that some form of "grouping" is needed, but that is not a requirement. If the designers of the solution believe that they have enough identifiers to handle the number of slices, and if they believe that the network can be provisioned and managed, then the solution is practical. In short, the framework does not force the solutions, but the solutions have to be able to deliver the function described in the framework. 2. What is the usage of the slice aggregate in the draft-ietf-teas-ietf-network-slices if it is not the network resource partition any more? Is it introduced a new identifier to identify a flow? As above, the concept of "slice aggregation" is only that: a concept. The text reads. These approaches are also sensitive to the scaling concerns of supporting a large number of IETF Network Slices within a single IP or MPLS network, and so offer ways to aggregate the slices so that the packet markings indicate an aggregate or grouping of IETF Network Slices where all of the packets are subject to the same routing and forwarding behavior. So, in this context, I think you can consider a slice aggregate to be equivalent to a "group" as described in the following text from 6.1 For scalability reasons, IETF Network Slices may be grouped together according to characteristics (including SLOs and SLEs). This grouping allows an operator to host a number of slices on a particular set of resources and so reduce the amount of state information needed in the network. The NSC is responsible for grouping the IETF Network Slice requests. 3. What is the scope of the slice aggregate work in the TEAS WG if it is a new identifier other than the resource partition? Will you go on to define the encapsulation and the protocol extensions for the new identifier or augment it to address the APN problem? I can't answer this question as editor of the framework document. It is a wider question for the working group, I think. Best, Adrian
- [Bier] What is Slice Aggregate? Lizhenbin
- Re: [Bier] What is Slice Aggregate? Toerless Eckert
- Re: [Bier] What is Slice Aggregate? Adrian Farrel
- Re: [Bier] What is Slice Aggregate? Lizhenbin