Re: [Teas] Thoughts about draft-nsdt-teas-ietf-network-slice-definition and isolation

Stewart Bryant <> Tue, 17 November 2020 09:57 UTC

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From: Stewart Bryant <>
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Date: Tue, 17 Nov 2020 09:57:39 +0000
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Cc: Stewart Bryant <>, Adrian Farrel <>,, Joel Halpern Direct <>,
To: Jeff Tantsura <>
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Subject: Re: [Teas] Thoughts about draft-nsdt-teas-ietf-network-slice-definition and isolation
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> On 9 Nov 2020, at 23:37, Jeff Tantsura <> wrote:
> I don’t think mixing performance objectives with isolation is a great idea though, 
> an SLA doesn’t change because there’s someone else sharing infrastructure with you, it is well understood that any changes within other customers should not affect you.

No, but in this class of networks the interaction between customers may be a lot more sensitive and detailed than we are used to. For example the single metrics that we normally associate with delay and jitter will likely become a mask in the same way that time and frequency transfer system find necessary to completely specify and instrument the behaviour of the subs system. We will likely need something analogous to MTIE and TDEV to describe packet and network interaction.

I therefore think it is useful to have an umbrella term for concept and the set of metrics that are of necessity more complex and critical than we are used to.

A possible alternative umbrella term is network cross talk. We understand the concept of crosstalk at the physical layer. The concept here in terms of performance is that packets do not interact at the micro level as well as the more normal macro level.

However, isolation has other feature that we need to think about under this umbrella, for example the need to only mix certain types of traffic allow (or exclude) traffic to flow over certain geographies or through nodes manufactured by certain countries. We do not have to agree with these constraints, but we need to accept that they are becoming a reality.

Now we could achieve the above by buying dedicated fibre or dedicated hardware, but that that does not support economies of scale.

I would be fine with us using a term other than isolation, but I think it is worthwhile highlighting that we are not in “ordinary” SLA territory with this, but that it is more complex and more detailed, and a top level term to group these characteristics is in my view helpful.

Best regards