Internet DRAFT - draft-liu-mpls-nas-combination
draft-liu-mpls-nas-combination
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.
Status of This Memo
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This Internet-Draft will expire on 25 November 2022.
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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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