Linda，
Let's instantiate the service in CAN as a rendering algorithm (RA), CAN is
employed to select a proper RA instance among many of them across mupltiple
sites according to the computing status asscociated with RA. RA identification
in the CAN data plane is thus phiscal position independant, and CAN routing
nodes play the role of switching RA service among different instances when
necessary. when it comes to the L4 connection such as TCP connection which is
the "service link" you quoted from my sentence, it's conveniently possible to
make this connection stable when it would be otherwise as the service instance
shifts without CAN scheme.
Regards,
Daniel Huang
黄光平 huangguangping
架构团队/有线规划部 Wireline architecture team./Wireline Product R&D Institute
南京市雨花区软件大道50号中兴通讯2号楼
R&D Building, ZTE
Corporation Software Road No.50,
Yuhua District, Nanjing, P..R.China, 210012
M: +86 13770311052
E: [email protected]
www.zte.com.cn
原始邮件
发件人：LindaDunbar
收件人：黄光平10039714;[email protected];
抄送人：[email protected];[email protected];[email protected];[email protected];
日 期 ：2022年06月21日 22:49
主 题 ：Re: [Dyncast] CAN BoF issues #4 #15 #36
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Daniel,
What does service link mean in your sentence? Can you give an example?
“it's determined at CAN ingress through "routing" of the service identification
which actually could also be used to establish the service link at layer 4…”
Thank you very much,
Linda
From: rtgwg <[email protected]> On Behalf Of [email protected]
Sent: Tuesday, June 21, 2022 4:53 AM
To: [email protected]
Cc: [email protected]; [email protected]; [email protected]; [email protected]
Subject: Re:[Dyncast] CAN BoF issues #4 #15 #36
Hi Peng,
as far as issue 36 is concerned, here's a distinctive perspecitve I would like
to bring up CAN architecture in terms of its potential benefits against the
ongoing solutions such as DNS & GSLB which would inherently bring extra
messages and thus latency. When it comes to service instance selection process,
it's done by DNS & GSLB or its equivalent node, while it's determined at CAN
ingress through "routing" of the service identification which actually could
also be used to establish the service link at layer 4, therefore the service
link would remain intact when the service end node shifts through CAN routing
policies.
in case of service node changing in service transaction, CAN routing logically
plays the role of DNS & GSLB and there would be no extra messages incurred
other than extra state brought in CAN nodes when necessary.
Best regards,
Daniel Huang
黄光平 huangguangping
架构团队/有线规划部 Wireline architecture team./Wireline Product R&D Institute
南京市雨花区软件大道50号中兴通讯2号楼
R&D Building, ZTE Corporation Software Road No.50,
Yuhua District, Nanjing, P..R.China, 210012
M: +86 13770311052
E: [email protected]
www.zte.com.cn
原始邮件
发件人：[email protected]
收件人：dyncast;
抄送人：rtgwg;jgs;Tony Li;cjbc;
日 期 ：2022年06月21日 17:27
主 题 ：[Dyncast] CAN BoF issues #4 #15 #36
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Dear All,
Here are the responses to issues #4 #15 #36, which are related to the
requirements of mobility, latency and flow affinity. Any comments are welcome.
This email is also copied to the questioner
(https://datatracker.ietf.org/doc/minutes-113-can/), hope for further
suggestions and confirmations. Thanks.
#4 Do the mobility issues and associated protocols are also in scope? There are
scenarios where routing alone would not be sufficient.
Might need routing+mobility solutions. From the routing side, the service
affinity are needed.
Supporting the affinity to a particular service instance while moving as a
client will need a solution (which will depend on the realization of such
affinity).
Supporting mobility across service instances, i.e. the moving from one service
instance to another mid-way of an ongoing transaction, will need extra
precaution, likely as a solution at the application layer but possibly
supported through the CAN infrastructure.
#15 It seems impossible to satisfy that requirement simultaneously with the
latency requirement.
Fulfilling the session persistence (or affinity) requirement together with any
latency requirement may indeed be a challenge, e.g., when long running sessions
occur across varying compute conditions at smaller timescale. In this case, CAN
may support session mobility from the possibly overloaded serving service
instance to a new, better suitable, one (see also issue #4) during the ongoing
session to mitigate the otherwise negative impact on latency. The methods with
which CAN may support this are in scope of CAN’s proposed work
#36 Need to understand if there are requirement to avoid extra messages or 1ms
of latency.
Extra messages, such as incurred in off-path systems like DNS, lead to possibly
significant latency, particularly when incurred frequently in scenarios where
possible service endpoints may need to change frequently. The use cases
attempted to cover this. Generally, avoiding extra messages in any solution CAN
may develop is a standard requirements for any engineering solution, following
the simplification principle.
Any detailed discussion is expected to be only within dyncast mailing list. You
can also check and add your comments to any of
them(https://github.com/CAN-IETF/CAN-BoF-ietf113/issues).
Regards,
Peng
--------------------------------------------------------------------------------
[email protected]
From: Linda Dunbar
Date: 2022-05-11 06:11
To: [email protected]
Subject: [Dyncast] Categories of the CAN BoF issues
CAN BoF proponents:
Many thanks for creating the CAN BoF issues tracking in the Github:
https://github.com/CAN-IETF/CAN-BoF-ietf113/issues/created_by/CAN-IETF?page=1&q=is%3Aopen+is%3Aissue+author%3ACAN-IETF
I went through the issues captured in the Github and characterized them into
groups. Some issues can be lumped together for the discussion. There are quite
a few issues related to the requirements, which need to be clarified.
Best Regards, Linda
Issues associated with Applications vs. Underlay networks:
Consider not to load underlay network with application details. #35
We have multiple upper layer application. Do we have additional needs for
routing(e.g. WG?) or we are using those applications and won't need such new
WG? #30
It needs application information too, so it can't just make a decision at the
network layer. #23
This is not striked as a routing problem; it's all service discovery that can
be done in higher layers. #21
3GPP and URSP solve this based on UPF selection. It uses both endpoint +
application. #20
One overlay plane per application. Resources/metric specific to the plane. #19
How does the application layer or the transport layer learn the network status
to steering traffic? #16
Need more clear requirements for CAN (to be addressed by
draft-liu-dyncast-ps-usecases):
Need to understand if three are requirement to avoid extra messages or 1ms of
latency #36
Regarding the flow affinity, is it from network perspective or from
application/computation perspective? #33
How to effectively compute paths? Shall we put CPUs into account? #32
What happens when the user moves? If so we also need to move application
context. #25
It can only move the services around as fast as it can update the routing
plane. which comes back to the point about service discovery (waiting for
convergence/distribution as opposed to just updating the SD server) #24
Whether the interests of the organization deploying the application and the
organization providing the network connectivity are aligned. Google doesn't
worry about this because they are both. #17
The question is more what the scope and semantic of information is that will
need to cross organizational boundaries. This needs further study, in
particular when assuming stakeholder division between service and network
provider.
It seems impossible to satisfy that requirement simultaneously with the latency
requirement. #15
It wasn't clear that how hard of a requirement session persistence is. #13
A session usually creates ephemeral state. If execution changes from one (e.g.,
virtualized) service instance to another, state/context needs transfer to
another. Such required transfer of state/context makes it desirable to have
session persistence (or instance affinity) as the default, removing the need
for explicit context transfer, while also supporting an explicit state/context
transfer (e.g., when metrics change significantly).
Should it select UPF based on the application? Steering is done per user? or
per application? #9
This seems to assume conventional non-distributed applications just running at
the edge. what about modern frameworks like Sapphire? and Ray? #7
It would be good to understand the multi-site requirements of such framework,
which I have understood to mainly run in single DCs.
Relation to 3GPP UPF #6
Relation to ALTO #5
Do the mobility issues and associated protocols are also in scope? There are
scenarios where routing alone would not be sufficient. #4
What is the position in the edge location regarding to UPF? #3
Is there some sort of authorization model so that an edge can indicate whether
or not it will provide compute services? #2
What is CNC and the relationship with CAN #1
Measurement of the Computing Resources (to be addressed by
draft-du-computing-resource-representation):
It is hard to use existing work to measure the computation, but we can optimize
the latency through the performance monitoring. We have performance/measurement
matrix over there. #34
Clarifications on the computing resource, its requirements and characteristics
would be helpful. #27
Each application may have a different definition of "resources" these then have
to be boiled down into a single topology Network Aware Computing (NAC! :) does
scale #14
Is computing resource measurable? #10
It is, and how to use the measurement would be solution related. See IFIP
Networking 2022 paper on how to simply expose “computing capability” and
achieve better steering with such simple measure.
Why compute resource is different with other resources? #8
Load Balance based solutions:
The point is that we need a standardized LB protocol #18
The LB as part of the application itself is superior (part of the distributed
application itself is to obtain and keep updating the "best" unicast location
to use). #22
If there is anything missing from current lbs that would prevent their use
as-is? other than there is for market reasons no interop standard between
different lbs? #12
For the load balance, should it learn the network’s status? #11
Dyncast based Solution issues:
For Dyncast, when the time is short, is it possible for the router to decide
the routing? It is too fast. #31
Is dyncast proposed to encapsulate? #29
Will CAN dyncast impact each and every router? How to avoid loops? #28
What's the assumed scale of a D-router? 10 ^ 6 sessions? 100^ 8? What's the
assumed update rate? !Gb? 1Tb? #26
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