draft-ietf-spring-mpls-path-segment-00.txt   draft-ietf-spring-mpls-path-segment-01.txt 
Network Working Group W. Cheng Network Working Group W. Cheng
Internet-Draft H. Li Internet-Draft H. Li
Intended status: Standards Track China Mobile Intended status: Standards Track China Mobile
Expires: September 9, 2019 M. Chen Expires: March 19, 2020 M. Chen
Huawei Huawei
R. Gandhi R. Gandhi
Cisco Systems, Inc. Cisco Systems, Inc.
R. Zigler R. Zigler
Broadcom Broadcom
March 08, 2019 September 16, 2019
Path Segment in MPLS Based Segment Routing Network Path Segment in MPLS Based Segment Routing Network
draft-ietf-spring-mpls-path-segment-00 draft-ietf-spring-mpls-path-segment-01
Abstract Abstract
A Segment Routing (SR) path is identified by an SR segment list, one A Segment Routing (SR) path is identified by an SR segment list.
or partial segments of the list cannot uniquely identify the SR path. Only the full segment list identifies the full end-to-end path, and
Path identification is a pre-requisite for various use-cases such as one segment or a partial set of segments from the list cannot
performance measurement (PM) of an SR path. identify the SR path and distinguish it from other SR paths that may
be partially congruent. But path identification is a pre-requisite
for various use-cases such as performance measurement (PM) of an SR
path.
In SR for MPLS (SR-MPLS) the segment identifiers are stripped from
the packet through label popping as the packet transits the network.
This means that when a packet reaches the egress of the SR path, it
is not possible to determine on which SR path it traversed the
network.
This document defines a new type of segment that is referred to as This document defines a new type of segment that is referred to as
Path Segment, which is used to identify an SR path. When used, it is Path Segment, which is used to identify an SR path in an SR-MPLS
inserted at the ingress node of the SR path and immediately follows network. When used, it is inserted at the ingress node of the SR
the last segment of the SR path. The Path Segment will not be popped path and immediately follows the last segment identifier in the
off until it reaches the egress node of the SR path. segment list of the SR path. The Path Segment will not be popped off
until it reaches the egress node of the SR path.
Path Segment can be used by the egress node to implement path A Path Segment can be used by the egress node to implement path
identification hence to support various use-cases including SR path identification hence to support various use-cases including SR path
PM, end-to-end 1+1 SR path protection and bidirectional SR paths PM, end-to-end 1+1 SR path protection, and bidirectional SR paths
correlation. correlation.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 9, 2019.
This Internet-Draft will expire on March 19, 2020.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
1.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 3 1.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 3
2. Path Segment . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Path Segment . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Nesting of Path Segments . . . . . . . . . . . . . . . . . . 5 3. Nesting of Path Segments . . . . . . . . . . . . . . . . . . 5
4. Path Segment Allocation . . . . . . . . . . . . . . . . . . . 6 4. Path Segment Allocation . . . . . . . . . . . . . . . . . . . 6
5. Path Segment for PM . . . . . . . . . . . . . . . . . . . . . 6 5. Path Segment for PM . . . . . . . . . . . . . . . . . . . . . 7
6. Path Segment for Bi-directional SR Path . . . . . . . . . . . 7 6. Path Segment for Bi-directional SR Path . . . . . . . . . . . 7
7. Path Segment for End-to-end Path Protection . . . . . . . . . 7 7. Path Segment for End-to-end Path Protection . . . . . . . . . 7
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
9. Security Considerations . . . . . . . . . . . . . . . . . . . 8 9. Security Considerations . . . . . . . . . . . . . . . . . . . 8
10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 8 10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 8
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
12.1. Normative References . . . . . . . . . . . . . . . . . . 9 12.1. Normative References . . . . . . . . . . . . . . . . . . 9
12.2. Informative References . . . . . . . . . . . . . . . . . 9 12.2. Informative References . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction 1. Introduction
Segment Routing (SR) [RFC8402] is a source routed forwarding method Segment Routing (SR) [RFC8402] is a source routed forwarding method
that allows to directly encode forwarding instructions (called that allows to directly encode forwarding instructions (called
segments) in each packet, hence it enables to steer traffic through a segments) in each packet, hence it enables steering traffic through a
network without the per-flow states maintained on the transit nodes. network without the per-flow states maintained on the transit nodes.
Segment Routing can be instantiated on MPLS data plane or IPv6 data Segment Routing can be instantiated on an MPLS data plane or an IPv6
plane. The former is called SR-MPLS, the latter is called SRv6 data plane. The former is called SR-MPLS
[I-D.ietf-spring-segment-routing-mpls], the latter is called SRv6
[RFC8402]. SR-MPLS leverages the MPLS label stack to construct SR [RFC8402]. SR-MPLS leverages the MPLS label stack to construct SR
path, and SRv6 uses the a new IPv6 Extension Header (EH) called the paths.
IPv6 Segment Routing Header (SRH)
[I-D.ietf-6man-segment-routing-header] to construct SR path.
In an SR-MPLS network, when a packet is transmitted along an SR path, In an SR-MPLS network, when a packet is transmitted along an SR path,
the labels in the MPLS label stack will be swapped or popped. So the labels in the MPLS label stack will be swapped or popped. So
that no label or only the last label may be left in the MPLS label that no label or only the last label may be left in the MPLS label
stack when the packet reaches the egress node. Thus, the egress node stack when the packet reaches the egress node. Thus, the egress node
cannot determine from which SR path the packet comes. cannot determine along which SR path the packet came.
However, to support use cases like end-to-end 1+1 path protection However, to support use cases like end-to-end 1+1 path protection
(Live-Live case), bidirectional path correlation or performance (Live-Live case), bidirectional path correlation or performance
measurement (PM), the ability to implement path identification is a measurement (PM), the ability to implement path identification is a
pre-requisite. pre-requisite. More detail can be found in Section 5, 6, and 7.
Therefore, this document introduces a new segment that is referred to Therefore, this document introduces a new segment that is referred to
as Path Segment. A Path Segment is defined to uniquely identify an as the Path Segment. A Path Segment is defined to uniquely identify
SR path in the context of the egress node. It is normally used by an SR path in an SR-MPLS network in the context of the egress node.
egress nodes for path identification or correlation. It is normally used by egress nodes for path identification or
correlation.
1.1. Requirements Language 1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in "OPTIONAL" in this document are to be interpreted as described in
BCP14 [RFC2119][RFC8174] when, and only when, they appear in all BCP14 [RFC2119][RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
1.2. Abbreviations 1.2. Abbreviations
skipping to change at page 4, line 10 skipping to change at page 4, line 20
SR-MPLS: Segment Routing instantiated on MPLS data plane. SR-MPLS: Segment Routing instantiated on MPLS data plane.
SRv6: Segment Routing instantiated on IPv6 data plane SRv6: Segment Routing instantiated on IPv6 data plane
2. Path Segment 2. Path Segment
A Path Segment is a single label that is assigned from the Segment A Path Segment is a single label that is assigned from the Segment
Routing Local Block (SRLB) or Segment Routing Global Block (SRGB) of Routing Local Block (SRLB) or Segment Routing Global Block (SRGB) of
the egress node of an SR path. It means that the Path Segment is the egress node of an SR path. It means that the Path Segment is
unique in the context of the egress node of the SR path. When Path unique in the context of the egress node of the SR path. When a Path
Segment is used, the Path Segment MUST be inserted at the ingress Segment is used, the Path Segment MUST be inserted at the ingress
node and MUST immediately follow the last label of the SR path. The node and MUST immediately follow the last label of the SR path. The
Path Segment may be used to identify an SR-MPLS Policy, its Path Segment may be used to identify an SR-MPLS Policy, its
Candidate-Path (CP) or a SID List (SL) Candidate-Path (CP), or a SID List (SL)
[I-D.ietf-spring-segment-routing-policy] terminating on an egress [I-D.ietf-spring-segment-routing-policy] terminating on an egress
node depending on the use-case. node depending on the use-case.
The value of the TTL field of the Path Segment MUST be set to the The value of the TTL field in the MPLS label stack entry containing
same value of the last segment label of the SR path. If the Path the Path Segment MUST be set to the same value as the TTL of the last
label stack entry for the last segment in the SR path. If the Path
Segment is the bottom label, the S bit MUST be set. Segment is the bottom label, the S bit MUST be set.
Normally, the intermediate nodes will not see the Path Segment label Normally, the intermediate nodes will not see the Path Segment label
and do not know how to process it. A Path Segment presenting to an and do not know how to process it. A Path Segment presenting to an
intermediate node is an error condition. intermediate node is an error condition.
The egress node MUST pop the Path Segment. The egress node MAY use The egress node MUST pop the Path Segment. The egress node MAY use
the Path Segment for further processing. For example, when the Path Segment for further processing. For example, when
performance measurement is enabled on the SR path, it can trigger performance measurement is enabled on the SR path, it can trigger
packet counting or timestamping. packet counting or timestamping.
skipping to change at page 6, line 44 skipping to change at page 6, line 48
Associated Channel (G-ACh)) between the ingress node and the egress Associated Channel (G-ACh)) between the ingress node and the egress
node, and the ingress node of the SR path can directly send a request node, and the ingress node of the SR path can directly send a request
to the egress node to ask for a Path Segment. to the egress node to ask for a Path Segment.
Another way is to leverage a centralized controller (e.g., PCE, SDN Another way is to leverage a centralized controller (e.g., PCE, SDN
controller) to assign the Path Segment. PCEP based Path Segment controller) to assign the Path Segment. PCEP based Path Segment
allocation is defined in [I-D.li-pce-sr-path-segment], and SR-policy allocation is defined in [I-D.li-pce-sr-path-segment], and SR-policy
based path segment allocation is defined in based path segment allocation is defined in
[I-D.li-idr-sr-policy-path-segment-distribution]. [I-D.li-idr-sr-policy-path-segment-distribution].
A Path Segment can be used in the case of PHP, where some labels MAY
be popped off at the penultimate hop of an SR path, but the Path
Segment MUST NOT be popped off until it reaches at the egress LSR.
In the case of a Path Segment that is assigned by a centralized
controller, the controller must make sure (e.g., by some capability
discovery mechanisms) that the egress LSR knows and can process the
Path Segment.
5. Path Segment for PM 5. Path Segment for PM
As defined in [RFC7799], performance measurement can be classified As defined in [RFC7799], performance measurement can be classified
into Active, Passive and Hybrid measurement. For Passive into Active, Passive and Hybrid measurement. For Passive
measurement, path identification at the measuring points is the pre- measurement, path identification at the measuring points is the pre-
requisite. Path segment can be used by the measuring points (e.g., requisite. Path segment can be used by the measuring points (e.g.,
the ingress/egress nodes of an SR path) or a centralized controller the ingress/egress nodes of an SR path) or a centralized controller
to correlate the packets counts/timestamps that are from the ingress to correlate the packets counts/timestamps that are from the ingress
and egress nodes to a specific SR path, then packet loss/delay can be and egress nodes to a specific SR path, then packet loss/delay can be
calculated. calculated.
Performance Delay Measurement (DM) and Loss Measurements (LM) in SR Performance Delay Measurement (DM) and Loss Measurements (LM) in SR
networks with MPLS data plane can be found in networks with MPLS data plane can be found in
[I-D.gandhi-spring-sr-mpls-pm] and [I-D.gandhi-spring-udp-pm]. [I-D.gandhi-spring-sr-mpls-pm] and [I-D.gandhi-spring-udp-pm].
6. Path Segment for Bi-directional SR Path 6. Path Segment for Bi-directional SR Path
With the current SR architecture, an SR path is a unidirectional With the current SR architecture, an SR path is a unidirectional
path. In some scenarios, for example, mobile backhaul transport path. In some scenarios, for example, mobile backhaul transport
network, there are requirements to support bidirectional path, and network, there are requirements to support bidirectional paths, and
the path is normally treated as a single entity and both directions the path is normally treated as a single entity and both directions
of the path have the same fate, for example, failure in one direction of the path have the same fate, for example, failure in one direction
will result in switching at both directions. will result in switching at both directions.
MPLS supports this by introducing the concepts of co-routed MPLS supports this by introducing the concepts of co-routed
bidirectional LSP and associated bidirectional LSP. With SR, to bidirectional LSP and associated bidirectional LSP. With SR, to
support bidirectional path, a straightforward way is to bind two support bidirectional paths, a straightforward way is to bind two
unidirectional SR paths to a single bidirectional path. Path unidirectional SR paths to a single bidirectional path. Path
segments can be used to correlate the two unidirectional SR paths at Segments can be used to correlate the two unidirectional SR paths at
both ends of the paths. both ends of the paths.
[I-D.li-pce-sr-bidir-path] defines how to use PCEP and Path segment [I-D.li-pce-sr-bidir-path] defines how to use PCEP and Path segment
to initiate a bidirectional SR path, and to initiate a bidirectional SR path, and
[I-D.li-idr-sr-policy-path-segment-distribution] defines how to use [I-D.li-idr-sr-policy-path-segment-distribution] defines how to use
SR policy and Path segment to initiate a bidirectional SR path. SR policy and Path segment to initiate a bidirectional SR path.
7. Path Segment for End-to-end Path Protection 7. Path Segment for End-to-end Path Protection
For end-to-end 1+1 path protection (i.e., Live-Live case), the egress For end-to-end 1+1 path protection (i.e., Live-Live case), the egress
node of an SR path needs to know the set of paths that constitute the node of an SR path needs to know the set of paths that constitute the
primary and the secondary(s), in order to select the primary packet primary and the secondaries, in order to select the primary packet
for onward transmission, and to discard the packets from the for onward transmission, and to discard the packets from the
secondary(s). secondaries.
To do this, each path needs a path identifier that is unique at the To do this, each path needs a path identifier that is unique at the
egress node. Depending on the design, this is a single unique path egress node. Depending on the design, this is a single unique path
segment label chosen by the egress PE. segment label chosen by the egress PE.
There then needs to be a method of binding this path identifiers into There then needs to be a method of binding this path identifiers into
equivalence groups such that the egress PE can determine the set of equivalence groups such that the egress PE can determine the set of
packets that represent a single path and its secondary. packets that represent a single path and its secondary.
It is obvious that this group can be instantiated in the network by It is obvious that this group can be instantiated in the network by
an SDN controller. an SDN controller and that the Path Segment achieves the desired
function.
8. IANA Considerations 8. IANA Considerations
This document does not require any IANA actions. This document does not require any IANA actions.
9. Security Considerations 9. Security Considerations
This document does not introduce additional security requirements and This document does not introduce additional security requirements and
mechanisms other than the ones described in [RFC8402]. mechanisms other than the ones described in [RFC8402].
10. Contributors 10. Contributors
Many thanks to following contributors for their contribution to this The following individuals also contribute to this document.
document.
Greg Mirsky
ZTE Corp
Email: gregimirsky@gmail.com
Cheng Li
Huawei Technologies
Huawei Campus, No. 156 Beiqing Rd.
Beijing 100095
China
EMail: chengli13@huawei.com
Shuangping Zhan o Cheng Li, Huawei
ZTE
Email: zhan.shuangping@zte.com.cn o Lei Wang, China Mobile
Lei Wang o Shuangping Zhan, ZTE
China Mobile
Email: wangleiyj@chinamobile.com o Greg
11. Acknowledgements 11. Acknowledgements
The authors would like to thank Stewart Bryant, Alexander Vainshtein, The authors would like to thank Adrian Farrel, Stewart Bryant,
Andrew G. Malis and Loa Andersson for their review, suggestions and Alexander Vainshtein, Andrew G. Malis and Loa Andersson for their
comments to this document. review, suggestions and comments to this document.
The authors would like to acknowledge the contribution from Alexander The authors would like to acknowledge the contribution from Alexander
Vainshtein on "Nesting of Path Segments". Vainshtein on "Nesting of Path Segments".
12. References 12. References
12.1. Normative References 12.1. Normative References
[I-D.ietf-spring-segment-routing-mpls] [I-D.ietf-spring-segment-routing-mpls]
Bashandy, A., Filsfils, C., Previdi, S., Decraene, B., Bashandy, A., Filsfils, C., Previdi, S., Decraene, B.,
Litkowski, S., and R. Shakir, "Segment Routing with MPLS Litkowski, S., and R. Shakir, "Segment Routing with MPLS
data plane", draft-ietf-spring-segment-routing-mpls-18 data plane", draft-ietf-spring-segment-routing-mpls-22
(work in progress), December 2018. (work in progress), May 2019.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
skipping to change at page 9, line 46 skipping to change at page 9, line 43
progress), September 2018. progress), September 2018.
[I-D.gandhi-spring-udp-pm] [I-D.gandhi-spring-udp-pm]
Gandhi, R., Filsfils, C., daniel.voyer@bell.ca, d., Gandhi, R., Filsfils, C., daniel.voyer@bell.ca, d.,
Salsano, S., Ventre, P., and M. Chen, "UDP Path for In- Salsano, S., Ventre, P., and M. Chen, "UDP Path for In-
band Performance Measurement for Segment Routing band Performance Measurement for Segment Routing
Networks", draft-gandhi-spring-udp-pm-02 (work in Networks", draft-gandhi-spring-udp-pm-02 (work in
progress), September 2018. progress), September 2018.
[I-D.ietf-6man-segment-routing-header] [I-D.ietf-6man-segment-routing-header]
Filsfils, C., Previdi, S., Leddy, J., Matsushima, S., and Filsfils, C., Dukes, D., Previdi, S., Leddy, J.,
d. daniel.voyer@bell.ca, "IPv6 Segment Routing Header Matsushima, S., and d. daniel.voyer@bell.ca, "IPv6 Segment
(SRH)", draft-ietf-6man-segment-routing-header-16 (work in Routing Header (SRH)", draft-ietf-6man-segment-routing-
progress), February 2019. header-22 (work in progress), August 2019.
[I-D.ietf-spring-segment-routing-policy] [I-D.ietf-spring-segment-routing-policy]
Filsfils, C., Sivabalan, S., daniel.voyer@bell.ca, d., Filsfils, C., Sivabalan, S., daniel.voyer@bell.ca, d.,
bogdanov@google.com, b., and P. Mattes, "Segment Routing bogdanov@google.com, b., and P. Mattes, "Segment Routing
Policy Architecture", draft-ietf-spring-segment-routing- Policy Architecture", draft-ietf-spring-segment-routing-
policy-02 (work in progress), October 2018. policy-03 (work in progress), May 2019.
[I-D.li-idr-sr-policy-path-segment-distribution] [I-D.li-idr-sr-policy-path-segment-distribution]
Li, C., Chen, M., Dong, J., and Z. Li, "Segment Routing Li, C., Chen, M., Dong, J., and Z. Li, "Segment Routing
Policies for Path Segment and Bidirectional Path", draft- Policies for Path Segment and Bidirectional Path", draft-
li-idr-sr-policy-path-segment-distribution-01 (work in li-idr-sr-policy-path-segment-distribution-01 (work in
progress), October 2018. progress), October 2018.
[I-D.li-pce-sr-bidir-path] [I-D.li-pce-sr-bidir-path]
Li, C., Chen, M., Dhody, D., Cheng, W., Li, Z., Dong, J., Li, C., Chen, M., Cheng, W., Li, Z., Dong, J., Gandhi, R.,
and R. Gandhi, "PCEP Extension for Segment Routing (SR) and Q. Xiong, "PCEP Extensions for Associated
Bidirectional Associated Paths", draft-li-pce-sr-bidir- Bidirectional Segment Routing (SR) Paths", draft-li-pce-
path-02 (work in progress), October 2018. sr-bidir-path-06 (work in progress), August 2019.
[I-D.li-pce-sr-path-segment] [I-D.li-pce-sr-path-segment]
Li, C., Chen, M., Dhody, D., Cheng, W., Dong, J., Li, Z., Li, C., Chen, M., Cheng, W., Dong, J., Li, Z., Gandhi, R.,
and R. Gandhi, "Path Computation Element Communication and Q. Xiong, "Path Computation Element Communication
Protocol (PCEP) Extension for Path Segment in Segment Protocol (PCEP) Extension for Path Segment in Segment
Routing (SR)", draft-li-pce-sr-path-segment-03 (work in Routing (SR)", draft-li-pce-sr-path-segment-08 (work in
progress), October 2018. progress), August 2019.
[RFC7799] Morton, A., "Active and Passive Metrics and Methods (with [RFC7799] Morton, A., "Active and Passive Metrics and Methods (with
Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799, Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799,
May 2016, <https://www.rfc-editor.org/info/rfc7799>. May 2016, <https://www.rfc-editor.org/info/rfc7799>.
Authors' Addresses Authors' Addresses
Weiqiang Cheng Weiqiang Cheng
China Mobile China Mobile
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