Re: [Dyncast] CAN BoF issues and the next steps

[Dirk Trossen <[e-mail]>]

All,

Responding to the various aspects in a single response:

1.      @all: we are working on an update to the arch draft, which will hopefully make the ingress-based service instance selection architecture (ISISA, quite a mouthful) clearer.

a.      This shows that the ingress is the decision point

b.      With it, the intermediary routing nodes need no knowledge of the selection process (or its data)

c.      With it, we hopefully clarify that the process is one of service instance selection (hence the longish name), not path selection. For the latter, the routing policies applied to steer traffic to the binding IP will be used.

d.      Other clarifications will hopefully also improve the document

2.      @Tony,Joel: the use case document (problems with existing solutions) already mentions client-based selection. There are a number of issues with this, which hopefully a clearer gap analysis (still discussing how to capture such analysis) will shed light on. But yes, it is an option which we have recognized.

3.      @Tony: there are two aspects of mobility, namely that of a client moving and, possibly, that of a service instance ‘moving’. The approaches to both are different. It is to be seen/decided, if we want to include the mobility aspect (if so, which ones) into the scope of work.

I hope this clarifies albeit in forward-reference to a to-be-updated draft.

Best,

Dirk


From: Dyncast [mailto:[e-mail]] On Behalf Of [e-mail]
Sent: 13 April 2022 06:15
To: Tony Li <[e-mail]>; Aijun Wang <[e-mail]>; Halpern' <[e-mail]>
Cc: [e-mail]; Peng Liu <[e-mail]>; Luigi IANNONE <luigi.iannone=[e-mail]>
Subject: Re: [Dyncast] CAN BoF issues and the next steps

Hi, Tony, Aijun, Joel:

    Multiple solutions exist here. But I suggest that we do not maintain per UE status in the Ingress.


A general procedure is as following:
1、      A client tries to access the service by using the anycast address
2、      The Ingress makes a decision which server to connect, and tunnels the anycast packet to the specific Egress
3、   The Egress forwards the anycast packet to the specific server, which can provide the service
4、            After the connection is established, the UE can communicate with the server by using the unicast address.


________________________________
[e-mail]<mailto:[e-mail]> & [e-mail]<mailto:[e-mail]>

From: Tony Li<mailto:[e-mail]>
Date: 2022-04-13 11:27
To: Aijun Wang<mailto:[e-mail]>
CC: dyncast<mailto:[e-mail]>; liupengyjy<mailto:[e-mail]>; Luigi IANNONE<mailto:luigi.iannone=[e-mail]>
Subject: Re: [Dyncast] CAN BoF issues and the next steps

Hi Aijun,

My understanding of the requirements was that a particular UE was supposed to be bound to a server for the lifetime of a ’transaction’ and that includes across the UE rehoming to a different source. Thus, the entire network needs to make a consistent and fixed decision per UE. Doing so in a dynamic environment would seem to be most challenging: you would need to synchronize forwarding state across the entire network instantly.

Making a single decision at the ingress and propagating that state seems somewhat easier.

And easier still is Joel’s proposal: have the UE pick one (from a centralized broker?) and then rely on unicast. :-)

Regards,
T


> On Apr 12, 2022, at 7:59 PM, Aijun Wang <[e-mail]<mailto:[e-mail]>> wrote:
>
> Hi, Joel:
> If you use binding address behind the ANYCAST address, it is possible. But if you use the ANYCAST address directly, you can't.
> For my understanding, the latter scenario is more popular.
>
>
> Best Regards
>
> Aijun Wang
> China Telecom
>
> -----Original Message-----
> From: Joel M. Halpern <[e-mail]<mailto:[e-mail]>>
> Sent: Wednesday, April 13, 2022 10:55 AM
> To: Aijun Wang <[e-mail]<mailto:[e-mail]>>; 'Luigi IANNONE' <luigi.iannone=[e-mail]<mailto:luigi.iannone=[e-mail]>>; [e-mail]<mailto:[e-mail]>; 'dyncast' <[e-mail]<mailto:[e-mail]>>
> Subject: Re: [Dyncast] CAN BoF issues and the next steps
>
> If the ingress edge does the calculation, makes the determination, and tunnels the traffic to the right place then the underlay routing system does not need to know anything about these metrics or the decision processes made by the edge.
>
> Yours,
> Joel
>
> On 4/12/2022 10:52 PM, Aijun Wang wrote:
>> Hi, Luigi:
>> Why only the ingress need such decision? I think all the routers
>> in-path need such information(routing metric +compute metric), to
>> achieve the optimal "instance selection".
>>
>> Best Regards
>>
>> Aijun Wang
>> China Telecom
>>
>> -----Original Message-----
>> From: [e-mail]<mailto:[e-mail]> <[e-mail]<mailto:[e-mail]>> On Behalf Of
>> Luigi IANNONE
>> Sent: Tuesday, April 12, 2022 3:04 PM
>> To: Aijun Wang <[e-mail]<mailto:[e-mail]>>; 'Joel M. Halpern'
>> <[e-mail]<mailto:[e-mail]>>; [e-mail]<mailto:[e-mail]>; 'dyncast'
>> <[e-mail]<mailto:[e-mail]>>
>> Subject: Re: [Dyncast] CAN BoF issues and the next steps
>>
>> Hi,
>>
>>> But, with the placement of the ANYCAST application servers closing to
>>> the users in different sites, the bottleneck to influence the E2E
>>> application performance is not only the network metric, the metric
>>> for the application servers play a major role now.
>>> It is time to consider both the network metric and application server
>>> metric together to achieve such goals.
>>
>> I think that Joel is not against the above (routing metric +compute
>> metric = instance selection).
>> I think that he is more inline with Dirk's position, meaning that it
>> is not necessarily the routing layer that has to be "enhanced" with
>> compute metrics.
>> Rather, an in-path decision based on both metrics should be made by
>> some (CAN ) element.
>> My personal take is that the ingress is well suited for that (since
>> for sure it is in-path).
>> Then you have the choice of various ways on how to steer the traffic.
>>
>> Ciao
>>
>> L.
>>
>>
>>
>>
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