SR Policy for Reverse Path
draft-lp-spring-sr-policy-reverse-path-00

Document Type Active Internet-Draft (individual)
Authors Liu Yao  , Shaofu Peng 
Last updated 2021-01-27
Stream (None)
Intended RFC status (None)
Formats plain text xml pdf htmlized (tools) htmlized bibtex
Stream Stream state (No stream defined)
Consensus Boilerplate Unknown
RFC Editor Note (None)
IESG IESG state I-D Exists
Telechat date
Responsible AD (None)
Send notices to (None)
SPRING WG                                                         Y. Liu
Internet-Draft                                                   S. Peng
Intended status: Standards Track                         ZTE Corporation
Expires: July 31, 2021                                  January 27, 2021

                       SR Policy for Reverse Path
               draft-lp-spring-sr-policy-reverse-path-00

Abstract

   This document introduces a method of dynamically configuring the
   return path for an SR path.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on July 31, 2021.

Copyright Notice

   Copyright (c) 2021 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Liu & Peng                Expires July 31, 2021                 [Page 1]
Internet-Draft     SR Policy for Reverse Segment List       January 2021

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  SR Policy for Bidirectional Path  . . . . . . . . . . . . . .   2
     2.1.  BGP Extensions for Advertising Segment List . . . . . . .   3
     2.2.  Illustration  . . . . . . . . . . . . . . . . . . . . . .   4
     2.3.  Difference from Path Segment  . . . . . . . . . . . . . .   5
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   5.  Normative References  . . . . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   Echo-BFD [RFC5880] can be used to monitor an SR Policy between the
   local and the remote BFD peers.  As defined in [RFC5880], the remote
   BFD system does not process the payload of an Echo BFD.

   A BSID can be used to specify the return path of an Echo BFD packet.

   As introduced in [I-D.ietf-spring-bfd], the sender MAY use a Binding
   SID (BSID) [RFC8402] that has been bound with the SR Policy that
   ensures the return of a packet to that particular node and a BSID MAY
   be associated with the SR Policy that is the reverse to the SR Policy
   programmed onto the BFD Echo packet by the sender.

   One way to implement this is through static configuration, e.g,
   configure the BSID corresponding to the return path for each segment
   list when enable BFD for an SR policy or an segment list.

   This document introduces a method of dynamically configuring the
   return path for an SR path, which can be used to specify the return
   path in Echo BFD for SR, ICMPv6 for SRv6, etc.

2.  SR Policy for Bidirectional Path

   In order to specify the return path for an segment list when
   delivering the SR Policy, and the tail node can return the packet
   according to the specified return path, this document proposes
   extensions of SR Policy.  It allows the segment list to have its own
   BSID.

   When delivering SR policy, the BSID of the segment list and the
   corresponding BSID of the return segment list can be carried
   together.

Liu & Peng                Expires July 31, 2021                 [Page 2]
Internet-Draft     SR Policy for Reverse Segment List       January 2021

2.1.  BGP Extensions for Advertising Segment List

   Segment List sub-TLV is introduced in
   [I-D.ietf-idr-segment-routing-te-policy] and it includes the elements
   of the paths (i.e., segments).

   This document introduces two optional sub-sub-tlvs of Segment List
   sub-TLV, Binding SID Sub-TLV and Reverse Binding SID Sub-TLV.

   The Binding SID sub-TLV has the following format:

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Show full document text