MPLS Working Group W. Cheng
Internet-Draft China Mobile
Intended status: Standards Track X. Min
Expires: 28 April 2022 ZTE Corp.
T. Zhou
Huawei
X. Dong
FiberHome
Y. Peleg
Broadcom
25 October 2021
Encapsulation For MPLS Performance Measurement with Alternate Marking
Method
draft-ietf-mpls-inband-pm-encapsulation-02
Abstract
This document defines the encapsulation for MPLS performance
measurement with alternate marking method, which performs flow-based
packet loss, delay, and jitter measurements on live traffic.
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 28 April 2022.
Copyright Notice
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Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions Used in This Document . . . . . . . . . . . . 3
1.1.1. Abbreviations . . . . . . . . . . . . . . . . . . . . 3
1.1.2. Requirements Language . . . . . . . . . . . . . . . . 4
2. Flow-based PM Encapsulation in MPLS . . . . . . . . . . . . . 4
2.1. Examples for Applying Flow-ID Label in a label stack . . 5
3. Procedures of Encapsulation, Look-up and Decapsulation . . . 8
4. Procedures of Flow-ID allocation . . . . . . . . . . . . . . 9
5. FLC and FRLD Considerations . . . . . . . . . . . . . . . . . 10
6. Equal-Cost Multipath Considerations . . . . . . . . . . . . . 10
7. Security Considerations . . . . . . . . . . . . . . . . . . . 11
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
10.1. Normative References . . . . . . . . . . . . . . . . . . 12
10.2. Informative References . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13
1. Introduction
[RFC8321] describes a passive performance measurement method, which
can be used to measure packet loss, delay, and jitter on live
traffic. Since this method is based on marking consecutive batches
of packets, the method is often referred to as Alternate Marking
Method. [RFC8372] discusses the desired capabilities for MPLS flow
identification, in order to perform a better in-band performance
monitoring of user data packets.
This document defines the encapsulation for MPLS performance
measurement with alternate marking method, which performs flow-based
packet loss, delay, and jitter measurements on live traffic. The
encapsulation defined in this document supports monitoring at
intermediate nodes, as well as flow identification at both transport
and service label.
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This document employs a method, other than Synonymous Flow Label
(SFL), to accomplish MPLS flow identification. The method described
in this document is complementary to the SFL method [RFC8957]
[I-D.ietf-mpls-sfl-control], the former mainly aims at hop-by-hop
performance measurement, and the latter mainly aims at end-to-end
performance measurement. Different sets of flows may use different
methods.
The method described in this document is also complementary to the
In-situ OAM method [I-D.ietf-ippm-ioam-data]
[I-D.ietf-ippm-ioam-direct-export], the former doesn't introduce any
new header whereas the latter introduces a new In-situ OAM header,
furthermore, the former requests the network nodes to report the data
used for performance measurement, and the latter requests the network
nodes to report the data used for operational and telemetry
information collection. One set of flows may use both of the two
methods concurrently.
1.1. Conventions Used in This Document
1.1.1. Abbreviations
ACL: Access Control List
cSPL: Composite Special Purpose Label
ECMP: Equal-Cost Multipath
ELC: Entropy Label Capability
ERLD: Entropy Readable Label Depth
eSPL: Extended Special Purpose Label
FLC: Flow-ID Label Capability
FLI: Flow-ID Label Indicator
FRLD: Flow-ID Readable Label Depth
LSP: Label Switched Path
MPLS: Multi-Protocol Label Switching
NMS: Network Management System
PHP: Penultimate Hop Popping
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PM: Performance Measurement
PW: PseudoWire
SFL: Synonymous Flow Label
SID: Segment ID
SPL: Special Purpose Label
SR: Segment Routing
TC: Traffic Class
TTL: Time to Live
VC: Virtual Channel
VPN: Virtual Private Network
1.1.2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. Flow-based PM Encapsulation in MPLS
Flow-based MPLS performance measurement encapsulation with alternate
marking method 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extension Label (15) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flow-ID Label Indicator (TBA1) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flow-ID Label | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Flow-based PM Encapsulation in MPLS
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Flow-ID Label Indicator (FLI) is an Extended Special Purpose Label
(eSPL), which is combined with the Extension Label (XL, value 15) to
form a Composite Special Purpose Label (cSPL), as defined in
[RFC9017]. Flow-ID Label Indicator is defined in this document as
value TBA1.
Analogous to Entropy Label Indicator [RFC6790], the TC and TTL for
the Extension Label and the Flow-ID Label Indicator SHOULD follow the
same field values of that label immediately preceding the Extension
Label, otherwise, the TC and TTL for the Extension Label and the
Flow-ID Label Indicator MAY be different values if it is known that
the Extension Label will not be exposed as the top label at any point
along the LSP. The S bit for the Extension Label and the Flow-ID
Label Indicator MUST be zero.
Flow-ID label is used as MPLS flow identification [RFC8372], its
value should be unique within the administrative domain. Flow-ID
values can be allocated by an external NMS or a controller, based on
measurement object instance such as LSP or PW. There is a one-to-one
mapping between Flow-ID and flow. The specific method on how to
allocate the Flow-ID values is described in Section 4.
Analogous to Entropy Label [RFC6790], the Flow-ID label can be placed
at either the bottom or the middle of the MPLS label stack, and the
Flow-ID label MAY appear multiple times in a label stack.
Section 2.1 of this document provides several examples to illustrate
how to apply Flow-ID label in a label stack. Again analogous to
Entropy Label, the TTL for the Flow-ID label MUST be zero to ensure
that it is not used inadvertently for forwarding, the TC for the
Flow-ID label may be any value, the S bit for the Flow-ID Label
depends on whether or not there are more labels in the label stack.
Besides flow identification, a color-marking field is also necessary
for alternate marking method. To achieve the purpose of coloring the
MPLS traffic, the current practice when writing this document is to
reuse the Flow-ID label's TC, i.e., using TC's highest order two bits
(called double-marking methodology [RFC8321]) as color-marking bits.
Alternatively, allocating multiple Flow-ID labels to the same flow
may be used for the purpose of alternate marking.
2.1. Examples for Applying Flow-ID Label in a label stack
Three examples on different layout of Flow-ID label (4 octets) are
illustrated as follows:
(1) Layout of Flow-ID label when applied to MPLS transport.
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+----------------------+
| LSP |
| Label |
+----------------------+
| Extension | <--+
| Label | |
+----------------------+ |--- cSPL
| Flow-ID Label | |
| Indicator | <--+
+----------------------+
| Flow-ID |
| Label |
+----------------------+
| Application |
| Label |
+----------------------+ <= Bottom of stack
| |
| Payload |
| |
+----------------------+
Figure 2: Applying Flow-ID to MPLS transport
Note that here if penultimate hop popping (PHP) is in use, the PHP
LSR that recognizes the cSPL MAY choose not to pop the cSPL and the
following Flow-ID label, otherwise the egress LSR would be excluded
from the performance measurement.
Also note that in other examples of applying Flow-ID to MPLS
transport, one LSP label can be substituted by multiple SID labels in
the case of using SR Policy, and the combination of cSPL and Flow-ID
label can be placed between SID labels, as specified in Section 5.
(2) Layout of Flow-ID label when applied to MPLS service.
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+----------------------+
| LSP |
| Label |
+----------------------+
| Application |
| Label |
+----------------------+
| Extension | <--+
| Label | |
+----------------------+ |--- cSPL
| Flow-ID Label | |
| Indicator | <--+
+----------------------+
| Flow-ID |
| Label |
+----------------------+ <= Bottom of stack
| |
| Payload |
| |
+----------------------+
Figure 3: Applying Flow-ID to MPLS service
Note that here application label can be MPLS PW label, MPLS Ethernet
VPN label or MPLS IP VPN label, and it's also called VC label as
defined in [RFC4026].
(3) Layout of Flow-ID label when applied to both MPLS transport and
MPLS service.
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+----------------------+
| LSP |
| Label |
+----------------------+
| Extension | <--+
| Label | |
+----------------------+ |--- cSPL
| Flow-ID Label | |
| Indicator | <--+
+----------------------+
| Flow-ID |
| Label |
+----------------------+
| Application |
| Label |
+----------------------+
| Extension | <--+
| Label | |
+----------------------+ |--- cSPL
| Flow-ID Label | |
| Indicator | <--+
+----------------------+
| Flow-ID |
| Label |
+----------------------+ <= Bottom of stack
| |
| Payload |
| |
+----------------------+
Figure 4: Applying Flow-ID to both MPLS transport and MPLS service
Note that for this example the two Flow-ID values appearing in a
label stack MUST be different, that is to say, Flow-ID label applied
to MPLS transport and Flow-ID label applied to MPLS service share the
same value space. Also note that the two Flow-ID label values are
independent from each other, e.g., two packets can belong to the same
VPN flow but to two different LSP flows, or two packets can belong to
two different VPN flows but to the same LSP flow.
3. Procedures of Encapsulation, Look-up and Decapsulation
The procedures for Flow-ID label encapsulation, look-up and
decapsulation are summarized as follows:
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* The ingress node inserts the Extension Label, the Flow-ID Label
Indicator, alongside with the Flow-ID label, into the MPLS label
stack. At the same time, the ingress node sets the color-marking
field, as needed by alternate-marking technique, and sets the
Flow-ID value, as defined in this document.
* The transit nodes lookup the Flow-ID label with the help of the
Extension Label and the Flow-ID Label Indicator, and transmit the
collected information to an external NMS or a controller, which
includes the values of the block counters and the timestamps of
the marked packets, along with the value of the Flow-ID, referring
to the procedures of alternate marking method. Note that in order
to lookup the Flow-ID label, the transit nodes need to perform
some deep packet inspection beyond the label at the top of the
label stack used to take forwarding decisions.
* The egress node pops the Extension Label and the Flow-ID Label
Indicator, alongside with the Flow-ID label, from the MPLS label
stack. This document doesn't introduce any new procedure
regarding to the process of the decapsulated packet.
4. Procedures of Flow-ID allocation
There are two ways of allocating Flow-ID, one way is to allocate
Flow-ID by manual trigger from the network operator, and the other
way is to allocate Flow-ID by automatic trigger from the ingress
node, details are as follows:
* In the case of manual trigger, the network operator would manually
input the characteristics (e.g. IP five tuples and IP DSCP) of
the measured flow, then the NMS or the controller would generate
one or two Flow-IDs based on the input from the network operator,
and provision the ingress node with the characteristics of the
measured flow and the corresponding allocated Flow-ID(s).
* In the case of automatic trigger, the ingress node would identify
the flow entering the measured path, export the characteristics of
the identified flow to the NMS or the controller by IPFIX
[RFC7011], then the NMS or the controller would generate one or
two Flow-IDs based on the export from the ingress node, and
provision the ingress node with the characteristics of the
identified flow and the corresponding allocated Flow-ID(s).
The policy pre-configured at the NMS or the controller decides
whether one Flow-ID or two Flow-IDs would be generated. If the
performance measurement on MPLS service is enabled, then one Flow-ID
applied to MPLS service would be generated; if the performance
measurement on MPLS transport is enabled, then one Flow-ID applied to
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MPLS transport would be generated; if both of them are enabled, then
two Flow-IDs respectively applied to MPLS service and MPLS transport
would be generated, in this case the transit nodes need to lookup
both of the two Flow-IDs by default, and that can be changed to e.g.
lookup only the Flow-ID applied to MPLS transport by configuration.
Whether using manual trigger or using automatic trigger, the NMS or
the controller MUST guarantee every generated Flow-ID is unique
within the administrative domain.
5. FLC and FRLD Considerations
Analogous to the Entropy Label Capability (ELC) defined in Section 5
of [RFC6790], and the Entropy Readable Label Depth (ERLD) defined in
Section 4 of [RFC8662], the Flow-ID Label Capability (FLC) and the
Flow-ID Readable Label Depth (FRLD) are defined in this document.
Both FLC and FRLD have the similar semantics with ELC and ERLD to a
router, except that the Flow-ID is used in its flow identification
function while the Entropy is used in its load-balancing function.
The ingress node MUST insert each Flow-ID label at an appropriate
depth, which ensures the node that needs to process the Flow-ID label
has the FLC. The ingress node SHOULD insert each Flow-ID label
within an appropriate FRLD, which is the minimum FRLD of all on-path
nodes that needs to read and use the Flow-ID label in question. How
the ingress node knows the Flow-ID label processing node has the FLC
and the appropriate FRLD for each Flow-ID label are outside the scope
of this document, whereas [I-D.xzc-lsr-mpls-flc-flrd] provides a
method to achieve that.
When SR paths are used as transport, the label stack grows as the
number of on-path segments increases, if the number of on-path
segments is high, that may become a challenge for the Flow-ID label
to be placed within an appropriate FRLD. In order to overcome this
potential challenge, an implementation MAY provide flexibility to the
ingress node to place Flow-ID label between SID labels, i.e.,
multiple identical Flow-ID labels at different depths MAY be
interleaved with SID labels, when that happens a sophisticated
network planning may be needed and it's beyond the scope of this
document.
6. Equal-Cost Multipath Considerations
Analogous to what's described in Section 5 of [RFC8957], under
conditions of Equal-Cost Multipath (ECMP), the introduction of a
Flow-ID label may cause the same problem as the introduction of an
SFL, and the two solutions proposed for the problem caused by the
introduction of SFL would also apply here.
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7. Security Considerations
This document introduces the performance measurement domain that is
the scope of a Flow-ID label. The Flow-ID Label Indicator and Flow-
ID label MUST NOT be signaled and distributed outside one performance
measurement domain. Improper configuration so that the Flow-ID label
being passed from one domain to another would likely result in
potential Flow-ID conflicts.
To prevent packets carrying Flow-ID label from leaking from one
domain to another, the domain boundary nodes SHOULD deploy some
policies (e.g., ACL) to filter out the packets. Specifically, in the
sending end, the domain boundary node SHOULD filter out the packets
that carry the Flow-ID Label Indicator and are sent to other domain;
in the receiving end, the domain boundary node SHOULD drop the
packets that carry the Flow-ID Label Indicator and are from other
domains.
8. IANA Considerations
In the Special-Purpose MPLS Label Values registry defined in [SPL], a
new Extended Special-Purpose MPLS Label Value for Flow-ID Label
Indicator is requested from IANA as follows:
+==========================+===============+============+===========+
| Extended Special-Purpose | Description | Semantics | Reference |
| MPLS Label Value | | Definition | |
+==========================+===============+============+===========+
| TBA1 | Flow-ID | Section 2 | This |
| | Label | | Document |
| | Indicator | | |
+--------------------------+---------------+------------+-----------+
Table 1: New Extended Special-Purpose MPLS Label Value for Flow-
ID Label Indicator
9. Acknowledgements
The authors would like to acknowledge Loa Andersson, Tarek Saad,
Stewart Bryant, Rakesh Gandhi, Greg Mirsky, Aihua Liu, Shuangping
Zhan and Ming Ke for their careful review and very helpful comments.
The authors would like to acknowledge Italo Busi and Chandrasekar
Ramachandran for their insightful MPLS-RT review and very helpful
comments.
10. References
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10.1. Normative References
[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>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[SPL] IANA, "Special-Purpose Multiprotocol Label Switching
(MPLS) Label Values",
<https://www.iana.org/assignments/mpls-label-values/>.
10.2. Informative References
[I-D.ietf-ippm-ioam-data]
Brockners, F., Bhandari, S., and T. Mizrahi, "Data Fields
for In-situ OAM", Work in Progress, Internet-Draft, draft-
ietf-ippm-ioam-data-15, 3 October 2021,
<https://www.ietf.org/archive/id/draft-ietf-ippm-ioam-
data-15.txt>.
[I-D.ietf-ippm-ioam-direct-export]
Song, H., Gafni, B., Zhou, T., Li, Z., Brockners, F.,
Bhandari, S., Sivakolundu, R., and T. Mizrahi, "In-situ
OAM Direct Exporting", Work in Progress, Internet-Draft,
draft-ietf-ippm-ioam-direct-export-07, 13 October 2021,
<https://www.ietf.org/archive/id/draft-ietf-ippm-ioam-
direct-export-07.txt>.
[I-D.ietf-mpls-sfl-control]
Bryant, S., Swallow, G., and S. Sivabalan, "A Simple
Control Protocol for MPLS SFLs", Work in Progress,
Internet-Draft, draft-ietf-mpls-sfl-control-01, 10 July
2021, <https://www.ietf.org/archive/id/draft-ietf-mpls-
sfl-control-01.txt>.
[RFC4026] Andersson, L. and T. Madsen, "Provider Provisioned Virtual
Private Network (VPN) Terminology", RFC 4026,
DOI 10.17487/RFC4026, March 2005,
<https://www.rfc-editor.org/info/rfc4026>.
[RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and
L. Yong, "The Use of Entropy Labels in MPLS Forwarding",
RFC 6790, DOI 10.17487/RFC6790, November 2012,
<https://www.rfc-editor.org/info/rfc6790>.
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[RFC7011] Claise, B., Ed., Trammell, B., Ed., and P. Aitken,
"Specification of the IP Flow Information Export (IPFIX)
Protocol for the Exchange of Flow Information", STD 77,
RFC 7011, DOI 10.17487/RFC7011, September 2013,
<https://www.rfc-editor.org/info/rfc7011>.
[RFC8321] Fioccola, G., Ed., Capello, A., Cociglio, M., Castaldelli,
L., Chen, M., Zheng, L., Mirsky, G., and T. Mizrahi,
"Alternate-Marking Method for Passive and Hybrid
Performance Monitoring", RFC 8321, DOI 10.17487/RFC8321,
January 2018, <https://www.rfc-editor.org/info/rfc8321>.
[RFC8372] Bryant, S., Pignataro, C., Chen, M., Li, Z., and G.
Mirsky, "MPLS Flow Identification Considerations",
RFC 8372, DOI 10.17487/RFC8372, May 2018,
<https://www.rfc-editor.org/info/rfc8372>.
[RFC8662] Kini, S., Kompella, K., Sivabalan, S., Litkowski, S.,
Shakir, R., and J. Tantsura, "Entropy Label for Source
Packet Routing in Networking (SPRING) Tunnels", RFC 8662,
DOI 10.17487/RFC8662, December 2019,
<https://www.rfc-editor.org/info/rfc8662>.
[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>.
[RFC9017] Andersson, L., Kompella, K., and A. Farrel, "Special-
Purpose Label Terminology", RFC 9017,
DOI 10.17487/RFC9017, April 2021,
<https://www.rfc-editor.org/info/rfc9017>.
Authors' Addresses
Weiqiang Cheng
China Mobile
Beijing
China
Email: chengweiqiang@chinamobile.com
Xiao Min
ZTE Corp.
Nanjing
China
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Email: xiao.min2@zte.com.cn
Tianran Zhou
Huawei
Beijing
China
Email: zhoutianran@huawei.com
Ximing Dong
FiberHome
Wuhan
China
Email: dxm@fiberhome.com
Yoav Peleg
Broadcom
United States of America
Email: yoav.peleg@broadcom.com
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