Re: [spring] WG Adoption Call for draft-dong-spring-sr-for-enhanced-vpn

"Dongjie (Jimmy)" <> Sun, 26 July 2020 02:35 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id 88A953A0916; Sat, 25 Jul 2020 19:35:26 -0700 (PDT)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -1.9
X-Spam-Status: No, score=-1.9 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, HTML_MESSAGE=0.001, RCVD_IN_MSPIKE_H2=-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 S-0YHwAV6tGd; Sat, 25 Jul 2020 19:35:23 -0700 (PDT)
Received: from ( []) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by (Postfix) with ESMTPS id 6F1173A090E; Sat, 25 Jul 2020 19:35:23 -0700 (PDT)
Received: from (unknown []) by Forcepoint Email with ESMTP id 101C8A9D9ABFB4E372A0; Sun, 26 Jul 2020 03:35:22 +0100 (IST)
Received: from ( by ( with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.1913.5; Sun, 26 Jul 2020 03:35:21 +0100
Received: from ( by ( with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1913.5; Sun, 26 Jul 2020 10:35:18 +0800
Received: from ([]) by ([]) with mapi id 15.01.1913.007; Sun, 26 Jul 2020 10:35:18 +0800
From: "Dongjie (Jimmy)" <>
To: Tarek Saad <>, James Guichard <>, "" <>
CC: "" <>
Thread-Topic: [spring] WG Adoption Call for draft-dong-spring-sr-for-enhanced-vpn
Thread-Index: AdZalG5COYT8S7GISwGDbTxQ2h/PJgH3ejEAAB+7zPA=
Date: Sun, 26 Jul 2020 02:35:18 +0000
Message-ID: <>
References: <> <>
In-Reply-To: <>
Accept-Language: en-US, zh-CN
Content-Language: zh-CN
x-originating-ip: []
Content-Type: multipart/alternative; boundary="_000_67ddb317132b4925899987941e4f3126huaweicom_"
MIME-Version: 1.0
X-CFilter-Loop: Reflected
Archived-At: <>
Subject: Re: [spring] WG Adoption Call for draft-dong-spring-sr-for-enhanced-vpn
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: "Source Packet Routing in NetworkinG \(SPRING\)" <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Sun, 26 Jul 2020 02:35:27 -0000

Hi Tarek,

Thanks for your comment, please see some replies inline:

From: spring [] On Behalf Of Tarek Saad
Sent: Sunday, July 26, 2020 2:57 AM
To: James Guichard <>om>;
Subject: Re: [spring] WG Adoption Call for draft-dong-spring-sr-for-enhanced-vpn

Hi WG,

This document is touching important topics regarding forwarding on specific set of resources in the network (such as those that define a network slice).
For this, it's important to be able to identify transiting traffic as belonging to a specific slice so as to impose the specific behavior upon forwarding the traffic on the associated resources.

This draft is proposing to allocate/assign different labels/SIDs (per topological element - either node or link) to identify the specific resource per slice and the respective forwarding behavior.
This may work for smaller networks (and for limited number of slices), but there are concerns that it would run into scale problems (related to # of required labels to allocate and amount of IGP state required for the different SIDs) - as number of topological elements in the network grows and number of vertical/ horizontal slices grows.

[Jie] Glad to know that you also think this is an important topic and can be useful for cases such as network slicing (while its applicability is general). This document describes the SR based mechanism for this. As mentioned in section 2 of this document, it requires additional SIDs and SRv6 Locators to be allocated, thus its applicability is for scenarios with limited number of virtual networks. The amount of IGP state is discussed in the relevant control plane drafts in LSR WG.

It might be useful to define a mechanism by which specific allocated resources for a given link or node are to be identified and not describe how virtual network topologies are to be constructed. This is because the topologies are not necessarily virtual and because there are a multiplicity of uses for this mechanism beyond constructing subsets of the underlay network topology.

We believe encoding the slice identifier separate from the forwarding instruction can yield better scale and still allow for steering on the specific resource. We intend to publish something along those lines in the coming next couple of weeks to gather more feedback.

[Jie] The scalability topic is further described in draft-dong-teas-enhanced-vpn-vtn-scalability in TEAS WG, which also provides some guidance for optimization, your review and comment to it are welcome. Thanks.

Best regards,


From: spring <<>> on behalf of James Guichard <<>>
Date: Wednesday, July 15, 2020 at 7:17 AM
To: "<>" <<>>
Cc: "<>" <<>>
Subject: [spring] WG Adoption Call for draft-dong-spring-sr-for-enhanced-vpn

Dear WG:

This email begins a 2 week WG adoption call for ending Wednesday 29th July 2020.

Please speak up if you support or oppose adopting this document into the WG. Please also provide comments/reasons for that support (or lack thereof). Silence will not be considered consent.


Jim, Joel & Bruno