Network Working Group                                             Y. Liu
Internet-Draft                                                  Z. Zhang
Intended status: Standards Track                                     ZTE
Expires: 25 November 2022                                    24 May 2022


                       Combination Method of NASs
                   draft-liu-mpls-nas-combination-00

Abstract

   This document provides an alternate mechanism to provide different
   ordering of in-stack data for MNA solutions which leverage the fixed
   bit catalogs.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   2
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Combination of NASs . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Different Ordering of Network Action/In-stack Data  . . .   3
     2.2.  C-bit in the Indicator  . . . . . . . . . . . . . . . . .   4
     2.3.  Encoding Example  . . . . . . . . . . . . . . . . . . . .   4
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   5.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     5.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     5.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   There is significant interest in developing the MPLS data plane to
   address the requirements of new applications
   [I-D.ietf-mpls-mna-usecases].  As introduced in
   [I-D.andersson-mpls-mna-fwk], the MPLS Network Actions (MNA)
   technologies aim to solve this.  An MNA solution is envisioned as a
   set of network action sub-stacks(NAS), each consists of label,
   indicators and in-Stack Data.

   One MNA solution may choose to encode the set of network actions as a
   list of bits in the network action indicator, and the ordering of the
   in-stack data LSEs corresponds to the ordering of the network action
   indicators.  If the meaning and ordering of the bits in the network
   action indicator is fixed, then the ordering of the network action
   and the corresponding possible in-stack data in the NAS are fixed
   either.

   Solutions leveraging the fixed bit catalogs are efficient for LSRs to
   process, but there may be scenarios where the ordering of the network
   actions/in-stack datas expected is not the ordering specified in the
   network action indicator.

   This document provides an alternate mechanism to provide different
   ordering of in-stack data for MNA solutions which leverage the fixed
   bit catalogs and makes these solutions more flexible.

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].



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1.2.  Terminology

   The terminologies follows [I-D.andersson-mpls-mna-fwk].

   *  Ancillary Data (AD): Data relating to the MPLS packet that may be
      used to affect the forwarding or other processing of that packet,
      either at an Label Edge Router (LER) [RFC4221] or Label Switching
      Router (LSR).  This data may be encoded within a network action
      sub-stack (see below) (in-stack data), and/or after the bottom of
      the label stack (post-stack data).

   *  Network Action: An operation to be performed on a packet.  A
      network action may affect router state, packet forwarding, or it
      may affect the packet in some other way.  A network action is said
      to be present if there is an indicator in the packet that invokes
      the action.

   *  Network Action Indication (NAI): An indication in the packet that
      a certain network action is to be perfomed.  There may be
      associated ancillary data in the packet.

   *  Network Action Sub-Stack (NAS): A set of related, contiguous Label
      Stack Entries (LSEs).  The first LSE is the Network Action Sub-
      stack Indicator.  The TC and TTL values in the sub-stack may be
      redefined.

   *  Network Action Sub-Stack Indicator (NSI): An LSE that contains a
      special label that indicates the start of a Network Action Sub-
      stack.

2.  Combination of NASs

2.1.  Different Ordering of Network Action/In-stack Data

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                Label                  |x x x|S|x x|x|x x x|A|B|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                    Figure 1: Bit-cataloged Indicator

   Figure 1 show an example of a bit-cataloged indicator in the NAS
   (using the TC and TTL repurposed method).

   Bit A indicates that network action A and the corresponding in-stack
   ancillary data A is present when set to 1.




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   Bit B indicates that network action B and the corresponding in-stack
   ancillary data A is present when set to 1.

   If bit A and bit B are both set to 1, it indicates that both network
   action A and network action B are present, and the LSE which carries
   data A is followed by that which contains data B.

   If it is required that data B is located before data A in the packet,
   an single NAS based on the fixed-bit approach can't fulfill this
   requirement.

2.2.  C-bit in the Indicator

   This document introduces a continue bit (C-bit) in the indicator as
   shown in the encoding example in Figure 2.

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                Label                  |x x x|S|x x|C|x x x|x|x|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Figure 2: C-bit in the Indicator

   When C-bit is set to 1, it indicates that there's another NAS
   following and the LSR SHOULD continue to look for the beginning of
   the next NAS and process it.

   With C-bit, NASs can be combined together as a whole to express
   different ordering of network actions and in-stack data.

2.3.  Encoding Example

   Figure 3 shows an encoding example of the combination of NASs
   leveraging C-bit.

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ---------------
     |                Label                  |x x x|S|x x|1|x x x|0|1|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   NAS-1
     |                         Data   B                              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ---------------
     |                Label                  |x x x|S|x x|0|x x x|1|0|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   NAS-2
     |                         Data   A                              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ---------------




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                    Figure 3: Combination of NASs

   For the indicator in NAS-1:

   C=1: there's another NAS following.

   B=1: Data B is included.

   For the indicator in NAS-2:

   C=0: there's no NAS following.

   A=1: Data A is included.

3.  IANA Considerations

   IANA is requested to create a new registry to assign a bit position
   for C-bit of the network action indicator. .

                     +==============+=============+===============+
                     | Bit Position | Description | Reference     |
                     +==============+=============+===============+
                     |  TBA         | Continue to | This document |
                     |              |  next NAS   |               |
                     +--------------+-------------+---------------+

4.  Security Considerations

   This document introduces no new security considerations.

5.  References

5.1.  Normative References

   [I-D.andersson-mpls-mna-fwk]
              Andersson, L., Bryant, S., Bocci, M., and T. Li, "MPLS
              Network Actions Framework", Work in Progress, Internet-
              Draft, draft-andersson-mpls-mna-fwk-01, 27 April 2022,
              <https://datatracker.ietf.org/doc/html/draft-andersson-
              mpls-mna-fwk-01>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

5.2.  Informative References




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   [I-D.ietf-mpls-mna-usecases]
              Saad, T., Makhijani, K., Song, H., and G. Mirsky, "Use
              Cases for MPLS Network Action Indicators and MPLS
              Ancillary Data", Work in Progress, Internet-Draft, draft-
              ietf-mpls-mna-usecases-00, 19 May 2022,
              <https://datatracker.ietf.org/doc/html/draft-ietf-mpls-
              mna-usecases-00>.

   [RFC4221]  Nadeau, T., Srinivasan, C., and A. Farrel, "Multiprotocol
              Label Switching (MPLS) Management Overview", RFC 4221,
              DOI 10.17487/RFC4221, November 2005,
              <https://www.rfc-editor.org/info/rfc4221>.

Authors' Addresses

   Yao Liu
   ZTE
   Nanjing
   China
   Email: liu.yao71@zte.com.cn


   Zheng Zhang
   ZTE
   Nanjing
   China
   Email: zhang.zheng@zte.com.cn
























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