Hi Bruno,
thank you for your thorough review, constructive comments, and helpful suggestions. Please find my notes below tagged by GIM>>. I attached the new working version of the draft and the diff that highlights all the updates.
Regards,
Greg
On Mon, Sep 2, 2024 at 4:53 AM Bruno Decraene via Datatracker <noreply@xxxxxxxx> wrote:
Reviewer: Bruno Decraene
Review result: Has Issues
Hello
I have been selected to do a routing directorate “early” review of this draft.
https://datatracker.ietf.org/doc/html/draft-ietf-mpls-mna-usecases-11
Document: draft-ietf-mpls-mna-usecases-11
Reviewer: Bruno Decraene
Review Date: 2024-09-02
Intended Status: Informational
Summary:
I have some minor concerns about this document that I think should be
resolved before it is submitted to the IESG.
Comments:
The document reads well and is interesting to read. Thank you.
GIM>> Thank you for your kind words, Bruno.
I think that the document and the abstract should better indicate how use cases
have been selected. In particular
- I think that the Abtract should better states how use cases have been
selected (and rejected). Abstract has two sentences about this while one should
be enough. And they differ ("community interest" vs "actively discussed").
GIM>> I think that "community interest" describes the attitude towards MNA work in general, while "actively discussed" is intended to reflect the situation with the use cases.
Especially since some uses cases have been moved to appendix,
GIM>> Indeed, over the course of the discussion, the feedback received from groups that work with the MPLS data plane indicated that theese groups have not yet reached consensus on the proposed solutions. The authors proposed moving these cases to the appendix rather than removing them altogether for the historical value. It appears that the WG agreed and supported that update.
and some of the
uses cases could be read as "motivating MNA" while some could be read as "could
(possibly) use MNA is MNA existed".
GIM>> I agree that some use cases, e.g., NOFRR, can be realized by using an assigned SPL. Some other use cases also can be supported by assigning a dedicated SPL. As the available number of bSPLs is limited, it is very likely that the respective solutions will use eSPL, i.e., two LSEs. In that regard, MNA improves utilization of SPL space.
- Ideally, each use case could better indicate which category it falls into.
(e.g., it's difficult to assume that the Segment Routing use case (section 2.5)
which has probably not been discussed in the SPRING WG is one use case
motivating MNA work and implementation)
GIM>> Yes, although the use case described in Section 2.5 seems useful, I also cannot find a document on that topic that have been submitted for the discussion by SPRING WG. Do you propose removing this section?
§1 Introduction
" The current state of the art requires allocating a new special-purpose label
[RFC3032] or extended special-purpose label. To conserve that limited
resource, an MPLS Network Action (MNA) approach was proposed to extend the MPLS
architecture." I don't feel that extended special-purpose label is such a
limited ressource. So you may want to rephase/split and indicate other reasons
for MNA (e.g., stack size when multiple MNA are used in the same packet, common
framework simplifying implementation...)
GIM>> Would the following updated text be clearer:
OLD TEXT:
The current state
of the art requires allocating a new special-purpose label [RFC3032]
or extended special-purpose label. To conserve that limited
resource, an MPLS Network Action (MNA) approach was proposed to
extend the MPLS architecture. MNA is expected to enable functions
that may require carrying additional ancillary data within the MPLS
packets, as well as a means to indicate the ancillary data is present
and a specific action needs to be performed on the packet.
NEW TEXT:
The current state
of the art requires allocating a new special-purpose label [RFC3032]
or extended special-purpose label. To conserve that limited
resource, an MPLS Network Action (MNA) approach was proposed to
extend the MPLS architecture. MNA is expected to enable functions
that may require carrying additional ancillary data within the MPLS
packets, as well as a means to indicate the ancillary data is present
and a specific action needs to be performed on the packet.
---
"This document lists various use cases that could benefit extensively from the
MNA framework [I-D.ietf-mpls-mna-fwk]."
This reads as a normative reference to me. So I'd rather move the reference to
normative. Alternative, you could rephrase to make the use case independent of
the framework.
GIM>> Thank you for the suggestion. I moved it to the Normative References list.
§1.1 Terminology
"The MPLS Ancillary Data (AD) is classified as:
residing within the MPLS label stack and referred to as In Stack Data (ISD), and
residing after the Bottom of Stack (BoS) and referred to as Post Stack Data
(PSD)."
I'd rather say :s/and/or
GIM>> I think that "and" is appropriate in characterizing two types of MPLS Ancillary Data. But I noticed hypen missing in ISD and PSD. Fixed these.
§1.2.1. Acronyms and Abbreviations
Thanks for expanding the acronym. But someone not familiar with the accronym
may also not be familiar with the concept. So I think adding a refence to the
RFC defining it would help.
GIM>> I know that some documents provide references in Abbreviation section. I find that references in the body of the document is sufficiently useful to a reader.
Also GDF has been moved to appendix. Is is still necessary in this list?
GIM>> I agree; removed.
§2.2.2. Alternate Marking Method
Given that the MPLS WG already provided a solution for the use case, it would
be good to indicate why this is still a use case to work on and why adding a
second solution would be helpful.
GIM>> As I understand it, the WG decided that the publication of draft-ietf-mpls-inband-pm-encapsulation is to fix squatting of the code point and the MNA-based solution will be considered:
Considering the MPLS performance measurement with the Alternate-
Marking method can also be achieved by MNA encapsulation, it is
agreed that this document will be made Historic once the MNA solution
of performance measurement with the Alternate-Marking method is
published as an RFC.
§2.4. NSH-based Service Function Chaining
"This approach, however, can benefit from the framework introduced with MNA "
It's not crystal clear to me what "this" refers to. e.g., RFC8595 or
draft-ietf-mpls-mna-usecases? May be clarifying would help.
GIM>> I hope that the following update makes it clearer:
NEW TEXT:
The approach in [RFC8595] introduces some limitations discussed in
[I-D.lm-mpls-sfc-path-verification]. However, that approach can
benefit from the framework introduced with MNA in
[I-D.ietf-mpls-mna-fwk].
§2.5. Network Programming
Has this Segment Routing use case been discussed in the SPRING WG? I don't
recall so. This comes back to the question of how the use cases have been
selected.
GIM>> The work on MNA was first conducted by the Open DT chartered by MPLS, PALS, and DetNet WGs. Once fundamental MNA documents matured, they were adopted by the MPLS WG. After that MNA work, as I understand it, has been conducted as part of MPLS WG agenda.
§3. Existing MPLS Use cases
This section is not clear to me. Is this expected to be count as use cases for
MNA? Justifying MNA? Using MNA? (if so why would those existing MPLS use cases
be changed to use MNA) Could this be clarified. -- "It is expected that new use
cases described in this document will allow" by "new" do you mean "additional
uses case that will be descibed in the future" in which cases this seems
unlikely after RFC publication. Or do you mean the new use cases described in
this document. If so do you mean all use cases or a select number of use cases.
If so may be they could be referenced in the sentence.
GIM>> That section is intended as the reminder to the authors of drafts that propose MNA-based solutions for the use cases listed in this document as well as for any applications in the future. I agree that "new" is confusing in the sentence. I propose the following update:
NEW TEXT:
MNA-based solutions for the use cases described in this document and
proposed in the future are expected to allow for coexistence and
backward compatibility with all existing MPLS services.
§4. Co-existence of the MNA Use Cases
MPLS allows for hierarchy. e.g., with Carriers' carrier. It would be good for
this section to cover the co-existence of MNA at multiple level of the
hierarchy. e.g. how MNA can freely be used by the customer carrier without
interference with the supporting carrier use of MNA.
GIM>> I think that the the questions of MNA deployment are outside the scope of the document that is aimed at listing generic use cases that benefit from MNA. Deployment of MNA-based solutions should be discussed in respective drafts that define the solution for the particular case listed in this document.
§6. Security Considerations
"This document introduces no new security considerations."
I think that the above point has security implications and that they should be
covered in this section.
§ Appendix A. Use Cases for Continued Discussion
Again, what are the considerations for moving some of the use cases to appendix?
If the only reason is ongoing discussion, shouldn't we wait for the conclusion
of those discussions before publishing this document?
Thanks,
Regards,
--Bruno
MPLS Working Group T. Saad
Internet-Draft Cisco Systems, Inc.
Intended status: Informational K. Makhijani
Expires: 9 March 2025 Independent
H. Song
Futurewei Technologies
G. Mirsky
Ericsson
5 September 2024
Use Cases for MPLS Network Action Indicators and MPLS Ancillary Data
draft-ietf-mpls-mna-usecases-12
Abstract
This document presents use cases that have a common feature that may
be addressed by encoding network action indicators and associated
ancillary data within MPLS packets. There is community interest in
extending the MPLS data plane to carry such indicators and ancillary
data to address the use cases that are described in this document.
The use cases described in this document are not an exhaustive set,
but rather the ones that are actively discussed by members of the
IETF MPLS, PALS, and DetNet working groups.
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 9 March 2025.
Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved.
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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
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Conventions used in this document . . . . . . . . . . . . 3
1.2.1. Acronyms and Abbreviations . . . . . . . . . . . . . 3
2. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. No Further Fast Reroute . . . . . . . . . . . . . . . . . 4
2.2. Applicability of Hybrid Measurement Methods . . . . . . . 4
2.2.1. In-situ OAM . . . . . . . . . . . . . . . . . . . . . 5
2.2.2. Alternate Marking Method . . . . . . . . . . . . . . 5
2.3. Network Slicing . . . . . . . . . . . . . . . . . . . . . 6
2.4. NSH-based Service Function Chaining . . . . . . . . . . . 6
2.5. Network Programming . . . . . . . . . . . . . . . . . . . 7
3. Existing MPLS Use cases . . . . . . . . . . . . . . . . . . . 7
4. Co-existence of the MNA Use Cases . . . . . . . . . . . . . . 8
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 8
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
8.1. Normative References . . . . . . . . . . . . . . . . . . 8
8.2. Informative References . . . . . . . . . . . . . . . . . 9
Appendix A. Use Cases for Continued Discussion . . . . . . . . . 12
A.1. Generic Delivery Functions . . . . . . . . . . . . . . . 12
A.2. Delay Budgets for Time-Bound Applications . . . . . . . . 12
A.3. Stack-Based Methods for Latency Control . . . . . . . . . 13
Contributors' Addresses . . . . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13
1. Introduction
This document describes use cases that introduce functions that
require special processing by forwarding hardware. The current state
of the art requires allocating a new special-purpose label [RFC3032]
or extended special-purpose label. An MPLS Network Action (MNA)
[RFC9613] approach was proposed to extend the MPLS architecture. MNA
is expected to enable functions that may require carrying additional
ancillary data within the MPLS packets, as well as a means to
indicate the ancillary data is present and a specific action needs to
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be performed on the packet.
This document lists various use cases that could benefit extensively
from the MNA framework [I-D.ietf-mpls-mna-fwk]. Supporting a
solution of the general MNA framework provides a common foundation
for future network actions that can be exercised in the MPLS data
plane.
1.1. Terminology
The following terminology is used in the document:
RFC 9543 Network Slice
is interpreted as defined in [RFC9543]. Furthermore, this
document uses "network slice" interchangeably as a shorter version
of the RFC 9543 Network Slice term.
The MPLS Ancillary Data (AD) is classified as:
* residing within the MPLS label stack and referred to as In-
Stack Data (ISD), and
* residing after the Bottom of Stack (BoS) and referred to as
Post-Stack Data (PSD).
1.2. Conventions used in this document
1.2.1. Acronyms and Abbreviations
ISD: In-Stack data
PSD: Post-Stack data
MNA: MPLS Network Action
NAI: Network Action Indicator
AD: Ancillary Data
DEX: Direct Export
I2E: Ingress to Edge
HbH: Hop by Hop
PW: Pseudowire
BoS: Bottom of Stack
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ToS: Top of Stack
NSH: Network Service Header
FRR: Fast Reroute
IOAM: In-situ Operations, Administration, and Maintenance
G-ACh: Generic Associated Channel
LSP: Label Switched Path
LSR: Label Switch Router
NRP: Network Resource Partition
AMM: Alternative Marking Method
2. Use Cases
2.1. No Further Fast Reroute
MPLS Fast Reroute [RFC4090], [RFC5286] and [RFC7490] is a useful and
widely deployed tool for minimizing packet loss in the case of a link
or node failure.
Several cases exist where, once a Fast Reroute (FRR) has taken place
in an MPLS network and a packet is rerouted away from the failure, a
second FRR impacts the same packet on another node and may result in
traffic disruption.
In such a case, the packet impacted by multiple FRR events may
continue to loop between the label switch routers (LSRs) that
activated FRR until the packet's TTL expires. That can lead to link
congestion and further packet loss. To avoid that situation, packets
that FRR has redirected will be marked using MNA to preclude further
FRR processing.
2.2. Applicability of Hybrid Measurement Methods
MNA can be used to carry information essential for collecting
operational information and measuring various performance metrics
that reflect the experience of the packet marked by MNA. Optionally,
the operational state and telemetry information collected on the LSR
may be transported using MNA techniques.
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2.2.1. In-situ OAM
In-situ Operations, Administration, and Maintenance (IOAM), defined
in [RFC9197] and [RFC9326], might be used to collect operational and
telemetry information while a packet traverses a particular path in a
network domain.
IOAM can run in two modes: Ingress to Edge (I2E) and Hop by Hop
(HbH). In I2E mode, only the encapsulating and decapsulating nodes
will process IOAM data fields. In HbH mode, the encapsulating and
decapsulating nodes and intermediate IOAM-capable nodes process IOAM
data fields. The IOAM data fields, defined in [RFC9197], can be used
to derive the operational state of the network experienced by the
packet with the IOAM Header that traversed the path through the IOAM
domain.
Several IOAM Option-Types have been defined:
* Pre-allocated Trace
* Incremental Trace
* Edge-to-Edge
* Proof-of-Transit
* Direct Export (DEX)
With all IOAM Option-Types except for the Direct Export (DEX), the
collected information is transported in the trigger IOAM packet. In
the IOAM DEX Option [RFC9326], the operational state and telemetry
information are collected according to a specified profile and
exported in a manner and format defined by a local policy. In IOAM
DEX, the user data packet is only used to trigger the IOAM data to be
directly exported or locally aggregated without being carried in the
IOAM trigger packets.
2.2.2. Alternate Marking Method
The Alternate Marking Method (AMM), defined in [RFC9341] and
[RFC9342]) is an example of a hybrid performance measurement method
([RFC7799]) that can be used in the MPLS network to measure packet
loss and packet delay performance metrics. [RFC8957] defined the
Synonymous Flow Label framework to realize AMM in the MPLS network.
The MNA is an alternative mechanism that can be used to support AMM
in the MPLS network.
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2.3. Network Slicing
An RFC 9543 Network Slice service ([RFC9543]) provides connectivity
coupled with network resource commitments and is expressed in terms
of one or more connectivity constructs. Section 5 of
[I-D.ietf-teas-ns-ip-mpls] defines a Network Resource Partition (NRP)
Policy as a policy construct that enables the instantiation of
mechanisms to support one or more network slice services. The
packets associated with an NRP may carry a marking in their network
layer header to identify this association, referred to as an NRP
Selector. The NRP Selector maps a packet to the associated network
resources and provides the corresponding forwarding treatment onto
the packet.
A router that requires the forwarding of a packet that belongs to an
NRP may have to decide on the forwarding action to take based on
selected next-hop(s), and the forwarding treatment (e.g., scheduling
and drop policy) to enforce based on the associated per-hop behavior.
In this case, routers that forward traffic over a physical link
shared by multiple NRPs need to identify the NRP to which the packet
belongs to enforce their respective forwarding actions and
treatments.
MNA technologies can signal actions for MPLS packets and carry data
essential for these actions. For example, MNA can carry the NRP
Selector [I-D.ietf-teas-ns-ip-mpls] in MPLS packets.
2.4. NSH-based Service Function Chaining
[RFC8595] describes how Service Function Chaining can be realized in
an MPLS network by emulating the Network Service Header (NSH)
[RFC8300] using only MPLS label stack elements.
The approach in [RFC8595] introduces some limitations discussed in
[I-D.lm-mpls-sfc-path-verification]. However, that approach can
benefit from the framework introduced with MNA in
[I-D.ietf-mpls-mna-fwk].
MNA can be used to extend NSH emulation using MPLS labels [RFC8595]
to support the functionality of NSH Context Headers, whether fixed or
variable-length. For example, MNA could support Flow ID [RFC9263]
that may be used for load-balancing among Service Function Forwarders
and/or the Service Functions within the same Service Function Path.
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2.5. Network Programming
In Segment Routing (SR), an ingress node steers a packet through an
ordered list of instructions called "segments". Each of these
instructions represents a function to be called at a specific
location in the network. A function is locally defined on the node
where it is executed and may range from simply moving forward in the
segment list to any complex user-defined behavior.
Network Programming combines SR functions to achieve a networking
objective beyond mere packet routing.
Encoding a pointer to a function and its arguments within an MPLS
packet transport header may be desirable. MNA can be used to encode
the FUNC::ARGs to support the functional equivalent of FUNC::ARG in
SRv6 as described in [RFC8986].
3. Existing MPLS Use cases
Several services can be transported over MPLS networks today. These
include providing Layer-3 (L3) connectivity (e.g., for unicast and
multicast L3 services), and Layer-2 (L2) connectivity (e.g., for
unicast Pseudowires (PWs), multicast E-Tree, and broadcast E-LAN L2
services). In those cases, the user service traffic is encapsulated
as the payload in MPLS packets.
For L2 service traffic, it is possible to use Control Word (CW)
[RFC4385] and [RFC5085] immediately after the MPLS header to
disambiguate the type of MPLS payload, prevent possible packet
misordering, and allow for fragmentation. In this case, the first
nibble the data that immediately follows after the MPLS BoS is set to
0000b to identify the presence of PW CW.
In addition to providing connectivity to user traffic, MPLS may also
transport OAM data (e.g., over MPLS Generic Associated Channels
(G-AChs) [RFC5586]). In this case, the first nibble of the data that
immediately follows after the MPLS BoS is set to 0001b. It indicates
the presence of a control channel associated with a PW, LSP, or
Section.
Bit Index Explicit Replication (BIER) [RFC8296] traffic can also be
encapsulated over MPLS. In this case, BIER has defined 0101b as the
value for the first nibble in the data that immediately appears after
the bottom of the label stack for any BIER-encapsulated packet over
MPLS.
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For pseudowires, the Generic Associated Channel [RFC7212] uses the
first four bits of the PW control word to provide the initial
discrimination between data packets and packets belonging to the
associated channel, as described in [RFC4385].
MPLS can be used as the data plane for DetNet [RFC8655]. The DetNet
sub-layers, forwarding, and service are realized using the MPLS label
stack, the DetNet Control Word [RFC8964], and the DetNet Associated
Channel Header [RFC9546].
MNA-based solutions for the use cases described in this document and
proposed in the future are expected to allow for coexistence and
backward compatibility with all existing MPLS services.
4. Co-existence of the MNA Use Cases
Two or more of the discussed cases may co-exist in the same packet.
That may require the presence of multiple ancillary data (whether In-
stack or Post-stack ancillary data) to be present in the same MPLS
packet.
For example, IOAM may provide essential functions along with network
slicing to help ensure that critical network slice SLOs are being met
by the network provider. In this case, IOAM can collect key
performance measurement parameters of network slice traffic flow as
it traverses the transport network.
5. IANA Considerations
This document has no IANA actions.
6. Security Considerations
This document introduces no new security considerations.
7. Acknowledgement
The authors gratefully acknowledge the input of the members of the
MPLS Open Design Team. Also, the authors sincerely thank Loa
Andersson, Xiao Min, and Jie Dong for their thoughtful suggestions
and help in improving the document.
8. References
8.1. Normative References
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[I-D.ietf-mpls-mna-fwk]
Andersson, L., Bryant, S., Bocci, M., and T. Li, "MPLS
Network Actions (MNA) Framework", Work in Progress,
Internet-Draft, draft-ietf-mpls-mna-fwk-10, 6 August 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-mpls-
mna-fwk-10>.
8.2. Informative References
[I-D.ietf-teas-ns-ip-mpls]
Saad, T., Beeram, V. P., Dong, J., Wen, B., Ceccarelli,
D., Halpern, J. M., Peng, S., Chen, R., Liu, X.,
Contreras, L. M., Rokui, R., and L. Jalil, "Realizing
Network Slices in IP/MPLS Networks", Work in Progress,
Internet-Draft, draft-ietf-teas-ns-ip-mpls-04, 28 May
2024, <https://datatracker.ietf.org/doc/html/draft-ietf-
teas-ns-ip-mpls-04>.
[I-D.lm-mpls-sfc-path-verification]
Liu, Y. and G. Mirsky, "MPLS-based Service Function
Path(SFP) Consistency Verification", Work in Progress,
Internet-Draft, draft-lm-mpls-sfc-path-verification-03, 11
June 2022, <https://datatracker.ietf.org/doc/html/draft-
lm-mpls-sfc-path-verification-03>.
[I-D.stein-srtsn]
Stein, Y. J., "Segment Routed Time Sensitive Networking",
Work in Progress, Internet-Draft, draft-stein-srtsn-01, 29
August 2021, <https://datatracker.ietf.org/doc/html/draft-
stein-srtsn-01>.
[I-D.zzhang-intarea-generic-delivery-functions]
Zhang, Z. J., Bonica, R., Kompella, K., and G. Mirsky,
"Generic Delivery Functions", Work in Progress, Internet-
Draft, draft-zzhang-intarea-generic-delivery-functions-03,
11 July 2022, <https://datatracker.ietf.org/doc/html/
draft-zzhang-intarea-generic-delivery-functions-03>.
[RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001,
<https://www.rfc-editor.org/info/rfc3032>.
[RFC4090] Pan, P., Ed., Swallow, G., Ed., and A. Atlas, Ed., "Fast
Reroute Extensions to RSVP-TE for LSP Tunnels", RFC 4090,
DOI 10.17487/RFC4090, May 2005,
<https://www.rfc-editor.org/info/rfc4090>.
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[RFC4385] Bryant, S., Swallow, G., Martini, L., and D. McPherson,
"Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for
Use over an MPLS PSN", RFC 4385, DOI 10.17487/RFC4385,
February 2006, <https://www.rfc-editor.org/info/rfc4385>.
[RFC5085] Nadeau, T., Ed. and C. Pignataro, Ed., "Pseudowire Virtual
Circuit Connectivity Verification (VCCV): A Control
Channel for Pseudowires", RFC 5085, DOI 10.17487/RFC5085,
December 2007, <https://www.rfc-editor.org/info/rfc5085>.
[RFC5286] Atlas, A., Ed. and A. Zinin, Ed., "Basic Specification for
IP Fast Reroute: Loop-Free Alternates", RFC 5286,
DOI 10.17487/RFC5286, September 2008,
<https://www.rfc-editor.org/info/rfc5286>.
[RFC5586] Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed.,
"MPLS Generic Associated Channel", RFC 5586,
DOI 10.17487/RFC5586, June 2009,
<https://www.rfc-editor.org/info/rfc5586>.
[RFC7212] Frost, D., Bryant, S., and M. Bocci, "MPLS Generic
Associated Channel (G-ACh) Advertisement Protocol",
RFC 7212, DOI 10.17487/RFC7212, June 2014,
<https://www.rfc-editor.org/info/rfc7212>.
[RFC7490] Bryant, S., Filsfils, C., Previdi, S., Shand, M., and N.
So, "Remote Loop-Free Alternate (LFA) Fast Reroute (FRR)",
RFC 7490, DOI 10.17487/RFC7490, April 2015,
<https://www.rfc-editor.org/info/rfc7490>.
[RFC7799] Morton, A., "Active and Passive Metrics and Methods (with
Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799,
May 2016, <https://www.rfc-editor.org/info/rfc7799>.
[RFC8296] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A.,
Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation
for Bit Index Explicit Replication (BIER) in MPLS and Non-
MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January
2018, <https://www.rfc-editor.org/info/rfc8296>.
[RFC8300] Quinn, P., Ed., Elzur, U., Ed., and C. Pignataro, Ed.,
"Network Service Header (NSH)", RFC 8300,
DOI 10.17487/RFC8300, January 2018,
<https://www.rfc-editor.org/info/rfc8300>.
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[RFC8595] Farrel, A., Bryant, S., and J. Drake, "An MPLS-Based
Forwarding Plane for Service Function Chaining", RFC 8595,
DOI 10.17487/RFC8595, June 2019,
<https://www.rfc-editor.org/info/rfc8595>.
[RFC8655] Finn, N., Thubert, P., Varga, B., and J. Farkas,
"Deterministic Networking Architecture", RFC 8655,
DOI 10.17487/RFC8655, October 2019,
<https://www.rfc-editor.org/info/rfc8655>.
[RFC8957] Bryant, S., Chen, M., Swallow, G., Sivabalan, S., and G.
Mirsky, "Synonymous Flow Label Framework", RFC 8957,
DOI 10.17487/RFC8957, January 2021,
<https://www.rfc-editor.org/info/rfc8957>.
[RFC8964] Varga, B., Ed., Farkas, J., Berger, L., Malis, A., Bryant,
S., and J. Korhonen, "Deterministic Networking (DetNet)
Data Plane: MPLS", RFC 8964, DOI 10.17487/RFC8964, January
2021, <https://www.rfc-editor.org/info/rfc8964>.
[RFC8986] Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer,
D., Matsushima, S., and Z. Li, "Segment Routing over IPv6
(SRv6) Network Programming", RFC 8986,
DOI 10.17487/RFC8986, February 2021,
<https://www.rfc-editor.org/info/rfc8986>.
[RFC9197] Brockners, F., Ed., Bhandari, S., Ed., and T. Mizrahi,
Ed., "Data Fields for In Situ Operations, Administration,
and Maintenance (IOAM)", RFC 9197, DOI 10.17487/RFC9197,
May 2022, <https://www.rfc-editor.org/info/rfc9197>.
[RFC9263] Wei, Y., Ed., Elzur, U., Majee, S., Pignataro, C., and D.
Eastlake 3rd, "Network Service Header (NSH) Metadata Type
2 Variable-Length Context Headers", RFC 9263,
DOI 10.17487/RFC9263, August 2022,
<https://www.rfc-editor.org/info/rfc9263>.
[RFC9326] Song, H., Gafni, B., Brockners, F., Bhandari, S., and T.
Mizrahi, "In Situ Operations, Administration, and
Maintenance (IOAM) Direct Exporting", RFC 9326,
DOI 10.17487/RFC9326, November 2022,
<https://www.rfc-editor.org/info/rfc9326>.
[RFC9341] Fioccola, G., Ed., Cociglio, M., Mirsky, G., Mizrahi, T.,
and T. Zhou, "Alternate-Marking Method", RFC 9341,
DOI 10.17487/RFC9341, December 2022,
<https://www.rfc-editor.org/info/rfc9341>.
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[RFC9342] Fioccola, G., Ed., Cociglio, M., Sapio, A., Sisto, R., and
T. Zhou, "Clustered Alternate-Marking Method", RFC 9342,
DOI 10.17487/RFC9342, December 2022,
<https://www.rfc-editor.org/info/rfc9342>.
[RFC9543] Farrel, A., Ed., Drake, J., Ed., Rokui, R., Homma, S.,
Makhijani, K., Contreras, L., and J. Tantsura, "A
Framework for Network Slices in Networks Built from IETF
Technologies", RFC 9543, DOI 10.17487/RFC9543, March 2024,
<https://www.rfc-editor.org/info/rfc9543>.
[RFC9546] Mirsky, G., Chen, M., and B. Varga, "Operations,
Administration, and Maintenance (OAM) for Deterministic
Networking (DetNet) with the MPLS Data Plane", RFC 9546,
DOI 10.17487/RFC9546, February 2024,
<https://www.rfc-editor.org/info/rfc9546>.
[RFC9613] Bocci, M., Ed., Bryant, S., and J. Drake, "Requirements
for Solutions that Support MPLS Network Actions (MNAs)",
RFC 9613, DOI 10.17487/RFC9613, August 2024,
<https://www.rfc-editor.org/info/rfc9613>.
Appendix A. Use Cases for Continued Discussion
Several use cases for which MNA can provide a viable solution have
been discussed. The discussion of these aspirational cases is
ongoing.
A.1. Generic Delivery Functions
The Generic Delivery Functions (GDFs), defined in
[I-D.zzhang-intarea-generic-delivery-functions], provide a new
mechanism to support functions analogous to those supported through
the IPv6 Extension Headers mechanism. For example, GDF can support
fragmentation/reassembly functionality in the MPLS network by using
the Generic Fragmentation Header. MNA can support GDF by placing a
GDF header in an MPLS packet within the Post-Stack Data block
[I-D.ietf-mpls-mna-fwk]. Multiple GDF headers can also be present in
the same MPLS packet organized as a list of headers.
A.2. Delay Budgets for Time-Bound Applications
The routers in a network can perform two distinct functions on
incoming packets, namely forwarding (where the packet should be sent)
and scheduling (when the packet should be sent). IEEE-802.1 Time
Sensitive Networking (TSN) and Deterministic Networking provide
several mechanisms for scheduling under the assumption that routers
are time-synchronized. The most effective mechanisms for delay
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minimization involve per-flow resource allocation.
Segment Routing (SR) is a forwarding paradigm that allows encoding
forwarding instructions in the packet in a stack data structure
rather than being programmed into the routers. The SR instructions
are contained within a packet in the form of a First-in, First-out
stack dictating the forwarding decisions of successive routers.
Segment routing may be used to choose a path sufficiently short to be
capable of providing a bounded end-to-end latency but does not
influence the queueing of individual packets in each router along
that path.
When carried over the MPLS data plane, a solution is required to
enable the delivery of such packets that can be delivered to their
final destination within a given time budget. One approach to
address this use case in SR-MPLS was described in [I-D.stein-srtsn].
A.3. Stack-Based Methods for Latency Control
One efficient data structure for inserting local deadlines into the
headers is a "stack", similar to that used in Segment Routing to
carry forwarding instructions. The number of deadline values in the
stack equals the number of routers the packet needs to traverse in
the network, and each deadline value corresponds to a specific
router. The Top-of-Stack (ToS) corresponds to the first router's
deadline, while the MPLS BoS refers to the last. All local deadlines
in the stack are later or equal to the current time (upon which all
routers agree), and times closer to the ToS are always earlier or
equal to times closer to the MPLS BoS.
The ingress router inserts the deadline stack into the packet
headers; no other router needs to know the time-bound flows'
requirements. Hence, admitting a new flow only requires updating the
ingress router's information base.
MPLS LSRs that expose the ToS label can also inspect the associated
"deadline" carried in the packet (either in the MPLS stack as ISD or
after BoS as PSD).
Contributors' Addresses
Loa Anderssen
Bronze Dragon Consulting
Email: loa@xxxxx
Authors' Addresses
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Tarek Saad
Cisco Systems, Inc.
Email: tsaad.net@xxxxxxxxx
Kiran Makhijani
Independent
Email: kiran.ietf@xxxxxxxxx
Haoyu Song
Futurewei Technologies
Email: haoyu.song@xxxxxxxxxxxxx
Greg Mirsky
Ericsson
Email: gregimirsky@xxxxxxxxx
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