Internet-Draft NAS Combination May 2022
Liu & Zhang Expires 25 November 2022 [Page]
Workgroup:
Network Working Group
Internet-Draft:
draft-liu-mpls-nas-combination-00
Published:
Intended Status:
Standards Track
Expires:
Authors:
Y. Liu
ZTE
Z. Zhang
ZTE

Combination Method of NASs

Abstract

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

Status of This Memo

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

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This Internet-Draft will expire on 25 November 2022.

Table of Contents

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].

1.2. Terminology

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

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.

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                              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ---------------
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, , <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, , <https://www.rfc-editor.org/info/rfc2119>.

5.2. Informative References

[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, , <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, , <https://www.rfc-editor.org/info/rfc4221>.

Authors' Addresses

Yao Liu
ZTE
Nanjing
China
Zheng Zhang
ZTE
Nanjing
China