MPLS Working Group W. Cheng
Internet-Draft China Mobile
Intended status: Standards Track X. Min
Expires: March 12, 2021 ZTE
T. Zhou
Huawei
X. Dong
FiberHome
Y. Peleg
Broadcom
September 8, 2020
Encapsulation For MPLS Performance Measurement with Alternate Marking
Method
draft-cheng-mpls-inband-pm-encapsulation-04
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
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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. Security Considerations . . . . . . . . . . . . . . . . . . . 10
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
9.1. Normative References . . . . . . . . . . . . . . . . . . 11
9.2. 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. Synonymous Flow Label (SFL), which
is introduced in [I-D.ietf-mpls-sfl-framework], is identified as a
method of accomplishing MPLS flow identification. This document
employs a method, other than SFL, to accomplish MPLS flow
identification. The method described in this document is simple and
flexible, furthermore, it complies with the current MPLS forwarding
paradigm.
On one hand, the method described in this document is complementary
to the SFL method [I-D.ietf-mpls-sfl-framework]
[I-D.bryant-mpls-sfl-control], the former targets at hop-by-hop
performance measurement, and the latter targets at end-to-end
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performance measurement, furthermore, the former supports the
application scenario where Flow-ID is applied to MPLS LSP and MPLS
VPN synchronously, and the latter doesn't support this kind of
application scenario. On the other hand, the method described in
this document is 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 but the latter introduces a
new In-situ OAM header, furthermore, the former allows the network
nodes to report the refined data (e.g. calculated performance
metrics) associated with a specified flow, nevertheless the latter
requests the network nodes to report the data (e.g. ingress interface
and egress interface) associated with a specified packet.
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.
1.1. Conventions Used in This Document
1.1.1. Abbreviations
ELC: Entropy Label Capability
ERLD: Entropy Readable Label Depth
FLC: Flow-ID Label Capability
FRLD: Flow-ID Readable Label Depth
LSP: Label Switched Path
MPLS: Multi-Protocol Label Switching
NMS: Network Management System
PM: Performance Measurement
PW: PseudoWire
SFL: Synonymous Flow Label
SID: Segment ID
SR: Segment Routing
TC: Traffic Class
TTL: Time to Live
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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
Flow-ID Label Indicator 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
[I-D.ietf-mpls-spl-terminology]. 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
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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 LSP.
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+----------------------+
| LSP |
| Label |
+----------------------+
| Extension | <--+
| Label | |
+----------------------+ |--- cSPL
| Flow-ID Label | |
| Indicator | <--+
+----------------------+
| Flow-ID |
| Label |
+----------------------+
| VPN |
| Label |
+----------------------+ <= Bottom of stack
| |
| Payload |
| |
+----------------------+
Figure 2: Applying Flow-ID to MPLS LSP
(2) Layout of Flow-ID Label when applied to MPLS VPN traffic.
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+----------------------+
| LSP |
| Label |
+----------------------+
| VPN |
| Label |
+----------------------+
| Extension | <--+
| Label | |
+----------------------+ |--- cSPL
| Flow-ID Label | |
| Indicator | <--+
+----------------------+
| Flow-ID |
| Label |
+----------------------+ <= Bottom of stack
| |
| Payload |
| |
+----------------------+
Figure 3: Applying Flow-ID to MPLS VPN
(3) Layout of Flow-ID Label when applied to both MPLS LSP and MPLS
VPN traffic.
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+----------------------+
| LSP |
| Label |
+----------------------+
| Extension | <--+
| Label | |
+----------------------+ |--- cSPL
| Flow-ID Label | |
| Indicator | <--+
+----------------------+
| Flow-ID |
| Label |
+----------------------+
| VPN |
| Label |
+----------------------+
| Extension | <--+
| Label | |
+----------------------+ |--- cSPL
| Flow-ID Label | |
| Indicator | <--+
+----------------------+
| Flow-ID |
| Label |
+----------------------+ <= Bottom of stack
| |
| Payload |
| |
+----------------------+
Figure 4: Applying Flow-ID to both MPLS LSP and MPLS VPN
Note that here VPN 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].
Also 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 LSP and Flow-ID Label applied to MPLS VPN share the same
value space.
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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o 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.
o The transit nodes look up 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.
o 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:
o 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 IP traffic 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 IP traffic flow and the corresponding allocated
Flow-ID(s).
o In the case of automatic trigger, the ingress node would identify
the IP traffic flow entering the measured path, export the
characteristics of the identified IP traffic 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 IP traffic 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 VPN traffic is enabled, then one Flow-ID
applied to MPLS VPN would be generated; if the performance
measurement on LSP tunnel is enabled, then one Flow-ID applied to
MPLS LSP would be generated; if both of them are enabled, then two
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Flow-IDs respectively applied to MPLS VPN and MPLS LSP would be
generated.
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. How the ingress node knows the Flow-ID Label processing
node has the FLC is outside the scope of this document.
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 appropriate FRLD for each Flow-ID Label is outside the
scope of this document.
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. 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.
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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.
7. IANA Considerations
In the Special-Purpose MPLS Label Values registry defined in
[SP-MPLS-Label], a new Extended Special-Purpose MPLS Label Value for
Flow-ID Label Indicator is requested from IANA as follows:
+-----------------------+----------------+--------------+-----------+
| Extended Special- | Description | Semantics | Reference |
| Purpose MPLS Label | | Definition | |
| Value | | | |
+-----------------------+----------------+--------------+-----------+
| TBA1 | Flow-ID Label | Section 2 | This |
| | Indicator | | Document |
+-----------------------+----------------+--------------+-----------+
Table 1: New Extended Special-Purpose MPLS Label Value for Flow-ID
Label Indicator
8. 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.
9. References
9.1. 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>.
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[SP-MPLS-Label]
"Special-Purpose MPLS Label Values", 2019,
<https://www.iana.org/assignments/mpls-label-values/mpls-
label-values.xml>.
9.2. Informative References
[I-D.bryant-mpls-sfl-control]
Bryant, S., Swallow, G., and S. Sivabalan, "A Simple
Control Protocol for MPLS SFLs", draft-bryant-mpls-sfl-
control-08 (work in progress), June 2020.
[I-D.ietf-ippm-ioam-data]
Brockners, F., Bhandari, S., and T. Mizrahi, "Data Fields
for In-situ OAM", draft-ietf-ippm-ioam-data-10 (work in
progress), July 2020.
[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", draft-ietf-ippm-ioam-direct-
export-01 (work in progress), August 2020.
[I-D.ietf-mpls-sfl-framework]
Bryant, S., Chen, M., Swallow, G., Sivabalan, S., and G.
Mirsky, "Synonymous Flow Label Framework", draft-ietf-
mpls-sfl-framework-10 (work in progress), August 2020.
[I-D.ietf-mpls-spl-terminology]
Andersson, L., Kompella, K., and A. Farrel, "Special
Purpose Label terminology", draft-ietf-mpls-spl-
terminology-03 (work in progress), August 2020.
[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>.
[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>.
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[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>.
Authors' Addresses
Weiqiang Cheng
China Mobile
Beijing
China
Email: chengweiqiang@chinamobile.com
Xiao Min
ZTE
Nanjing
China
Email: xiao.min2@zte.com.cn
Tianran Zhou
Huawei
Beijing
China
Email: zhoutianran@huawei.com
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Ximing Dong
FiberHome
Wuhan
China
Email: dxm@fiberhome.com
Yoav Peleg
Broadcom
USA
Email: yoav.peleg@broadcom.com
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