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

Joel Halpern Direct <> Tue, 17 November 2020 10:05 UTC

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To: Stewart Bryant <>
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From: Joel Halpern Direct <>
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Date: Tue, 17 Nov 2020 05:05:37 -0500
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Subject: Re: [Teas] Thoughts about draft-nsdt-teas-ietf-network-slice-definition and isolation
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Stewart, I think you are raising an interesting question, but one where 
I got lost part way through.

Can you elaborate one what you mean by "something analogous to MTIE and 
TDEV to describe packet and network interaction".

Thank you,

On 11/17/2020 4:57 AM, Stewart Bryant wrote:
>> 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
> Stewart