Re: [Dyncast] Updates on Dyncast drafts

Aijun Wang <> Tue, 23 February 2021 03:12 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id 10C6F3A24F0 for <>; Mon, 22 Feb 2021 19:12:39 -0800 (PST)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -1.896
X-Spam-Status: No, score=-1.896 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, HTML_MESSAGE=0.001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001] autolearn=ham autolearn_force=no
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id L22LL68ZAPlp for <>; Mon, 22 Feb 2021 19:12:35 -0800 (PST)
Received: from ( []) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by (Postfix) with ESMTPS id C17A53A24EF for <>; Mon, 22 Feb 2021 19:12:34 -0800 (PST)
Received: from DESKTOP2IOH5QC (unknown []) by (Hmail) with ESMTPA id 015D11C00D1; Tue, 23 Feb 2021 11:12:29 +0800 (CST)
From: "Aijun Wang" <>
To: "'Dirk Trossen'" <>, <>
Cc: "'Linda Dunbar'" <>
References: <> <00a001d70732$03a652b0$0af2f810$> <>
In-Reply-To: <>
Date: Tue, 23 Feb 2021 11:12:29 +0800
Message-ID: <009301d70991$b8584720$2908d560$>
MIME-Version: 1.0
Content-Type: multipart/alternative; boundary="----=_NextPart_000_0094_01D709D4.C67D5BE0"
X-Mailer: Microsoft Outlook 16.0
Thread-Index: AQJARhSlo6UN8wd+7gkUi2Z5IHQxNQJg+rqkAhJeIBipbvS3kA==
Content-Language: zh-cn
X-HM-Tid: 0a77ccdfb996d993kuws015d11c00d1
Archived-At: <>
Subject: Re: [Dyncast] Updates on Dyncast drafts
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Tue, 23 Feb 2021 03:12:39 -0000

Hi, Dirk:


I think the mapping between D-SID and D-BID is more like DNS mapping. If so,
current architecture is not solely one routing solution, but related to the
deployment of upper-layer(for example, DNS-like system). 

For routing area, I think they mainly consideration how to accomplish the
optimal path to D-BID, and don't care the mapping between D-SID and D-BID.


For protocol-specific  contribution, I think you can pay attention to LSR
for IGP extension related draft, and IDR for BGP extension related draft.

Actually, there are two related drafts has already been posted that related
to Dyncast, I think you can refer them:
eta-data-01( BGP Extension)
ext-02 (OSPF Extension)


Can the above two drafts address the requirements of Dyncast?



Best Regards


Aijun Wang

China Telecom


From: <> On Behalf Of Dirk
Sent: Monday, February 22, 2021 4:24 PM
To: Aijun Wang <>cn>;
Subject: Re: [Dyncast] Updates on Dyncast drafts


Hi Aijun,


Many thanks for the comments. Please see inline as [DOT].







From: Aijun Wang [] 
Sent: 20 February 2021 03:42
To: Dirk Trossen < <>
>; <> 
Subject: RE: [Dyncast] Updates on Dyncast drafts


Hi, Dirk:


I have a quick review of the usecase and architecture draft that you
provides and think this is one interesting topic to discuss within IETF.

Regarding to the usecase draft, as I known, there are also other SDO(ITU
etc.) studying on this topic, can anyone share what their progress now and
can we refer to their work to prove the necessary of such service needed in
the network?

Regarding to the architecture draft, I am litter confusion about two mapping
components as described in section 5. " Dyncast Control-plane vs Data-plane

1.     Why we need the mapping of (D-SID, D-BID)?  

We are mentioning "Dynamic Anycast" architecture, why don't' use just one
unique D-SID in several locations for one service?  The router have the
capabilities to select what's the most optimal path to reach the service
that identified by D-SID.

[DOT] The D-SID provides the identification of the service, while the D-BID
provides the mapping onto a specific service instance being selected as a
destination for a service request towards D-SID. What you describe, i.e.,
"to select the most optimal path to reach the service" is done by the
D-Router by mapping the D-SID onto a specific service instance (using the
metrics to perform the selection), this instance being identified through
D-BID. What I'm not sure is what you mean with "in several locations for one
service"? The service has indeed a single identifier and is being realized
in different locations, those network locations being identified by D-BID. I
wonder if you are suggesting to use a fully routed model, i.e., route
directly on the D-SID instead of mapping the D-SID to the D-BID? The reason
for doing the latter is to enable an ingress architecture, i.e., focusing
the dyncast capability in the ingress while re-using the locator-based
addressing and routing in the network. This minimizes necessary change,
i.e., allows for using existing routers beyond the dyncast ingress. 


2.     Why we need the mapping between D-Router and D-Forwarder?

It seems not easy to introduces the D-Forwarder entity into the network,
also the mapping between them. I think we should first focus on utilizing
the existing network devices to accomplish the aim.

[DOT] The D-Forwarder is motivated in the arch draft by allowing for pushing
the D-SID to D-BID mapping closer to the client. It is an optional
component, i.e., you can entirely rely on the D-router only. 


The answers to your questions are inline below [WAJ].


Best Regards


Aijun Wang

China Telecom




From: <>
< <> > On Behalf Of
Dirk Trossen
Sent: Tuesday, February 16, 2021 1:18 AM
To: <> 
Subject: [Dyncast] Updates on Dyncast drafts


Dear All,


For the preparation to the planned side meeting at the upcoming IETF110
(more details on this will follow in a separate email), it is our intention
to formulate use cases, problems and architectural requirements for
addressing those problems in order to focus this side meeting on the
following two main questions:

1.       Are the use cases compelling and the problems worth to be discussed
and possibly solved in the routing area?

[WAJ] Yes, I think it is possibly solved in the routing area.

[DOT] apologies for the unclear wording from my side: this question is not
really about solving the problems in the routing area as a matter of
possibility but whether we should solve these problems in the routing area
rather than relying on higher, e.g., application-level solutions.


2.       What would be the best approach in doing so within the IETF, e.g.,
through a new WG focusing on dyncast or through contributions to existing,
protocol-specific WGs, with problem and requirements kept as contributions
to the RTG WG?

        [WAJ] Based on current information about the use case and the aim, I
think contributions to existing, protocol-specific WGs is feasible.

[DOT] Could you please point out those protocol-specific WGs to contribute
solutions to?


Depending on what the community thinks, we will go for a more formal meeting
at IETF111. 


As input material for our discussion, we have uploaded the following three
Dyncast drafts to the datatracker, namely the Dyncast use case and problem
statement at and the
Dyncast requirements at We have also
uploaded a draft outlining a possible Dyncast architecture at


Any comments or views on either of those two questions above are warmly
welcome in preparation to the planned side meeting. We hope to see many of
you there.





Dirk (on hehalf of the authors of the Dyncast drafts)