Re: [Idr] questions about draft-ietf-idr-bgpls-srv6-ext-03

"Chengli (Cheng Li)" <> Mon, 07 September 2020 04:19 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id 59F603A080C; Sun, 6 Sep 2020 21:19:26 -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 nb5uVgXv96Co; Sun, 6 Sep 2020 21:19:24 -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 568C03A0812; Sun, 6 Sep 2020 21:19:24 -0700 (PDT)
Received: from (unknown []) by Forcepoint Email with ESMTP id B9368E5D825777B41B4E; Mon, 7 Sep 2020 05:19:19 +0100 (IST)
Received: from ( by ( with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1913.5; Mon, 7 Sep 2020 05:19:19 +0100
Received: from ( by ( with Microsoft SMTP Server (version=TLS1_0, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.1.1913.5 via Frontend Transport; Mon, 7 Sep 2020 05:19:18 +0100
Received: from ([]) by ([]) with mapi id 14.03.0487.000; Mon, 7 Sep 2020 12:19:16 +0800
From: "Chengli (Cheng Li)" <>
To: "" <>, "" <>
CC: "" <>, "" <>
Thread-Topic: [Idr] questions about draft-ietf-idr-bgpls-srv6-ext-03
Thread-Index: AQHWhMTdyDd/yMkMRUWuYUJ1jmPEyKlcicBg
Date: Mon, 07 Sep 2020 04:19:17 +0000
Message-ID: <>
References: <>
In-Reply-To: <>
Accept-Language: zh-CN, en-US
Content-Language: zh-CN
x-originating-ip: []
Content-Type: multipart/alternative; boundary="_000_C7C2E1C43D652C4E9E49FE7517C236CB02BC07BAdggeml529mbxchi_"
MIME-Version: 1.0
X-CFilter-Loop: Reflected
Archived-At: <>
Subject: Re: [Idr] questions about draft-ietf-idr-bgpls-srv6-ext-03
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Inter-Domain Routing <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Mon, 07 Sep 2020 04:19:26 -0000

Hi PSF and Ketan,

IMHO, the SRv6 SID Structure TLV can be included in the sub-TLV field of SRv6 END.X TLV, SRv6 LAN END.X TLV (for adj SIDs) and SRv6 SID NLRI(for node SIDs). So I guess it may be a typo, the SRv6 End should be SRv6 End.X.  We can double check the IANA section.

But from the text in Section 7, SRv6 SID attributes,

   This section specifies the new TLVs to be carried in the BGP Link
   State Attribute associated with the BGP-LS SRv6 SID NLRI.

The sub-TLVs defined in this section are associated with the SRv6 SID NLRI, so these sub-TLVs are associated with node SIDs. Regarding Adj SIDs, the information is included in the Link NLRI. If so, do we need to make a new upper level for SRv6 SID Structure sub-TLV? Because it is not only apply for node SIDs but also link/adj SIDs.

Regarding the second question.  I think,

·         an Adj-SID is included in the Link NLRI, with an optional SID Structure TLV as a sub-TLV. SRv6 SID NLRI and attributes are not needed to be included.

·         a Node SID is included in the SRv6 SID NLRI, with TLVs like SRv6 Endpoint Behavior TLV, SRv6 BGP Peer Node SID TLV, SRv6 SID Structure TLV in the SRv6 SID attributes to describe the information of the node SID.


From: Idr [] On Behalf Of
Sent: Monday, September 7, 2020 11:13 AM
Subject: [Idr] questions about draft-ietf-idr-bgpls-srv6-ext-03

Hi Ketan,

I have a question for section 7.3.  SRv6 SID Structure TLV, and hope to get your answer.

It described:

SRv6 SID Structure TLV is used to advertise the length of each

   individual part of the SRv6 SID as defined in

   [I-D.ietf-spring-srv6-network-programming].  It is an optional TLV

   for use in the BGP-LS Attribute for an SRv6 SID NLRI and as an

   optional sub-TLV of the SRv6 End, IS-IS SRv6 LAN End.X and OSPFv3

   SRv6 LAN End.X TLVs.  The TLV has the following format:

My question is:

1) Becasue section 7 mentions that "This section specifies the new TLVs to be carried in the BGP Link State Attribute associated with the BGP-LS SRv6 SID NLRI.",

    so, can "structure TLV" be also associated with BGP-LS Link NLRI ?

2) As the description, does it mean that an SRv6 SID NLRI can contain SRv6 SID Information TLV for END SID or LAN End.X SID, then "structure TLV" is also associated with BGP-LS Link NLRI ?

3) Why the description skip End.X SID ?