Internet DRAFT - draft-han-pce-path-computation-fg-transport
draft-han-pce-path-computation-fg-transport
PCE Working Group L. Han
Internet-Draft China Mobile
Intended status: Standards Track H. Zheng
Expires: 5 September 2024 Huawei Technologies
M. Wang
Y. Zhao
China Mobile
4 March 2024
Path Computation and Control Extention Requirements for Fine-Granularity
Transport Network
draft-han-pce-path-computation-fg-transport-01
Abstract
This document focuses on the requirements for path computation and
control of the fine-granularity transport network. It provides the
general context of the use cases of path computation and the
considerations on the requirements of PCE extension in such fine-
granularity transport network.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Path Computation Requirements in Fine-grain Transport
Network . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Use Cases of Fine-grain Path Computation . . . . . . . . . . 5
6. Requirements of PCE Extension for Fine-grain Transport
Network . . . . . . . . . . . . . . . . . . . . . . . . . 6
7. PCEP Extension for Fine-grain Transport Network . . . . . . . 6
8. Manageability Consideration . . . . . . . . . . . . . . . . . 6
9. Security Considerations . . . . . . . . . . . . . . . . . . . 6
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
11. Normative References . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
With the proposal of new service demand, the technology of the
transport network is constantly developing. TDM based Optical
Transport Network (OTN) and Metro Transport Network (MTN)
technologies are both moving towards fine- grain hard slices. The
vertical industries and dedicated line services have higher
requirements on isolation, security and reliability but with smaller
bandwidth. Fine-grain TDM technology can provide the flexible
N*10Mbps bandwidth for these connections.
ITU-T has a series of recommendations for fgOTN (fine grain OTN ) and
fgMTN (fine grain MTN). The fgOTN overview is defined in
[ITU-T_G.709.20], fgOTN layer architecture is defined in
[ITU-T_G.872], fgOTN Interface and server adaptation is defined in
[ITU-T_G.709], fgOTN equipment is defined in [ITU-T_G.798], fgOTN
synchronization is defined in [ITU-T_G.8251], fgOTN management
requirementsis defined in [ITU-T_G.874] and protocol-neutral
information model is defined in [ITU-T_G.875]. The fgMTN overview is
defined in[ITU-T_G.8312.20], fgMTN layer architecture is defined in
[ITU-T_G.8310], fgMTN interface is defined in [ITU-T_G.8312], fgMTN
equipment is defined in [ITU-T_G.8321], fgMTN synchronization is
defined in [ITU-T_G.mtn-sync] , and management requirement and
information model is defined in [ITU-T_G.8350]. Both the fgOTN and
fgMTN protection are defined in [ITU-T_G.808.4].
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The new fine-grain transport technology will significantly increase
the number of path connections in the network compared to the
traditional connections based on optical wavelength or ODUk with
larger bandwidth. For the future massive fine-grain channel
connections, how to effectively perform end-to-end path computation
and control will be an important technical topic.
The architecture of a Path Computation Element (PCE)-based model has
been presented in [RFC4655]. It discusses PCE-based implementations
including composite, external, and multiple PCE path computation.
[RFC8779]addresses the extensions required for GMPLS applications and
routing requests, for example, for Optical Transport Networks (OTNs)
and Wavelength Switched Optical Networks (WSONs). Due to the new
features of fine-grain technology, PCE may need to be extended.
This document focuses on the requirements for path computation and
control of the fine-grain transport network. Section 3 provides the
general context of the use cases of path computation. Section 4
provides the considerations on the requirements of PCE extension in
such fine-grain transport network.
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.
3. Terminology
Domain:
A domain, as defined in [RFC4655], is "any collection of network
elements within a common sphere of address management or path
computation responsibility". Specifically, within this document,
we mean a part of an operator's network under common management
(i.e., under shared operational management using the same
instances of a tool and the same policies). Network elements are
often grouped into domains based on technologies, vendor profiles,
or geographic proximity.
FG:
Fine Grain
MTN:
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Metro Transport Network
OTN:
Optical Transport Network
4. Path Computation Requirements in Fine-grain Transport Network
Compared to traditional optical networks, fine-grain transport
networks require more quantity, faster, and more flexible path set-up
and removing capabilities. The path computation architecture should
be reliable, scalable and efficient to facilitate the configuration
of a large amount of fine-granularity channel connections.
+-----------------------+ +------------------------+
| Domain A | | Domain B |
+-+-+ +--+ +--+ ++-+ +-++ +--+ +--+ +-+-+
--->|PE1+---+P1+----+P2+---->+P4|------>|P5+----+P6+----+P7+---->+PE2|--->
+-+-+ +--+ +--+ ++-+ +-++ +--+ +--+ +-+-+
| | | |
+-----------------------+ +------------------------+
^ ^
| |
+-----------------E2E fine-grain connection----------------+
Figure 1: Scenario of E2E fine-grain connection
o The number of fine-grain TDM channels will significantly increase:
FgOTN and fgMTN support 10Mbit/s level tributary slots
granularity. One ODU2 channel can support up to 952 fgOTN
connections. One 5Gbps MTN channel can support up to 480 fgMTN
connections. For transport devices with a switching capacity of
several Tbps, they can support fine-grain channel connections of
tens of thousands or even tens of thousands. Therefore, for the
network, the number of connections throughout the entire network
will significantly increase.
o According to service requirements, fine-grain paths may change
frequently and dynamically:
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One fine-grain channel can carry and correspond to a certain CBR
or Ethernet service, rather than serving as a large optical
channel. When the services appear or end, or its bandwidth
changes, or the destination address changes, they will cause
changes in fine-grain channels. Therefore, compared to serving as
an optical bandwidth channel for the routers, the fine-granularity
channels serve directly as service channels, which are more likely
to change.
5. Use Cases of Fine-grain Path Computation
To address the massive fine-grain path computation issues, it is
necessary to combine centralized control systems and distributed
control protocols. On the one hand, a centralized control system is
used to calculate the global optimal routing and develop resource
scheduling strategies. On the other hand, distributed control
protocols between devices are used to perform operations such as
cross connection configuration and time slot occupation assignment.
The applications of fine-grain path computation and related
capabilities at least include:
o Fine-grain path set-up:
The control system calculates service routing in a centralized way
and sends messages to the source node. Then, the connection is
established between devices through connection control signaling.
The end-to-end fine-grain connections may cross one or more
domains.
o Fine-grain resource management:
The topology and resource information of fine-grain devices and
slots need to be collected and reported, so that the centralized
system can calculate new routes based on this information and
allocate slot resources for the new connections.
o Fine-grain path update:
During the connection, fine-grain channels can undergo hitless
bandwidth adjustment. When channel bandwidth increases or
decreases, time slots need to be added or removed. It is needed
to control and update the existing path parameter.
o Fine-grain path removal:
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When the service no longer needs this connection, it is necessary
to remove this fine-grain channel and release the corresponding
resources.
o Service awareness and mapping:
In order to accurately match the fine-grain service requirements,
the service awareness and mapping function for fine-grain
transport network have been defined
in[I-D.liu-ccamp-optical2cloud-problem-statement]. The PE device
learns and identifies the packet header carried by client services
(including source and destination MAC or IP addresses etc). Then
it reports the identified client services to the control system.
The control system selects or creates connection(s) acorrding to
service requirements, and configures the mapping between service
and connection(s).
6. Requirements of PCE Extension for Fine-grain Transport Network
The centralized computation model of PCE architecture seems to be
suitable for the fine-grain transport network, while the PCEP (PCE
communication protocol) needs to be extended to meet the fine-grain
transport requirements.
The path calculation request/reply message from the PCC or the PCE
must contain the information specifying appropriate fine-grain
channel attributes, including the fine-grain switching capability/
type, the fine-grain server layer type, the fine-grain time slots,
the fine-grain client ID, end-to-End fine-granularity path protection
type, etc.
The protocol and signaling should support the application of fine-
grain path set-up/update/removal and resource management.
7. PCEP Extension for Fine-grain Transport Network
Fine-grain path set-up/adjustment,service awareness and mapping and
fine- grain resource management may be invovled in PCEP extensions.
The specific extentions will continue to apply in the future.
8. Manageability Consideration
TBD
9. Security Considerations
TBD
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10. IANA Considerations
TBD
11. Normative References
[I-D.liu-ccamp-optical2cloud-problem-statement]
Liu, S., Zheng, H., Guo, A., Zhao, Y., and D. King,
"Problem Statement and Gap Analysis for Connecting to
Cloud DCs via Optical Networks", Work in Progress,
Internet-Draft, draft-liu-ccamp-optical2cloud-problem-
statement-05, 11 October 2023,
<https://datatracker.ietf.org/doc/html/draft-liu-ccamp-
optical2cloud-problem-statement-05>.
[ITU-T_G.709]
ITU-T, "ITU-T G.709: Interfaces for the optical transport
network;", https://www.itu.int/rec/T-REC-G.709.
[ITU-T_G.709.20]
ITU-T, "ITU-T G.709.20: Overview of fine grain
OTN;", Work in progress.
[ITU-T_G.798]
ITU-T, "ITU-T G.798: Characteristics of optical transport
network hierarchy equipment functional
blocks;", https://www.itu.int/rec/T-REC-G.798.
[ITU-T_G.808.4]
ITU-T, "ITU-T G.808.4: Linear protection for fgMTN and
fgOTN;", Work in progress.
[ITU-T_G.8251]
ITU-T, "ITU-T G.8251: The control of jitter and wander
within the optical transport network
(OTN);", https://www.itu.int/rec/T-REC-G.8251.
[ITU-T_G.8310]
ITU-T, "ITU-T G.8310: Architecture of the metro transport
network; 01/2024", Work in progress, January 2024.
[ITU-T_G.8312]
ITU-T, "ITU-T G.8312:Interfaces for metro transport
networks; 01/2024", https://www.itu.int/rec/T-REC-G.8312,
January 2024.
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[ITU-T_G.8312.20]
ITU-T, "ITU-T G.8312.20:Overview of fine grain MTN;
01/2024", https://www.itu.int/rec/T-REC-G.8312.20,
January 2024.
[ITU-T_G.8321]
ITU-T, "ITU-T G.8321:Characteristics of metro transport
network equipment functional
blocks;", https://www.itu.int/rec/T-REC-G.8321.
[ITU-T_G.8350]
ITU-T, "ITU-T G.8350: Management and Control of metro
transport networks;", https://www.itu.int/rec/T-REC-
G.8350.
[ITU-T_G.872]
ITU-T, "ITU-T G.872: Architecture of the optical transport
network;", https://www.itu.int/rec/T-REC-G.872.
[ITU-T_G.874]
ITU-T, "ITU-T G.874: Management aspects of optical
transport network elements;", https://www.itu.int/rec/T-
REC-G.874.
[ITU-T_G.875]
ITU-T, "ITU-T G.875: Optical transport network: Protocol-
neutral management information model for the network
element view;", https://www.itu.int/rec/T-REC-G.875.
[ITU-T_G.mtn-sync]
ITU-T, "ITU-T G.mtn-sync:Synchronization aspects of metro
transport network", Work in progress.
[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>.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004,
<https://www.rfc-editor.org/info/rfc3688>.
[RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
Computation Element (PCE)-Based Architecture", RFC 4655,
DOI 10.17487/RFC4655, August 2006,
<https://www.rfc-editor.org/info/rfc4655>.
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[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>.
[RFC8779] Margaria, C., Ed., Gonzalez de Dios, O., Ed., and F.
Zhang, Ed., "Path Computation Element Communication
Protocol (PCEP) Extensions for GMPLS", RFC 8779,
DOI 10.17487/RFC8779, July 2020,
<https://www.rfc-editor.org/info/rfc8779>.
Authors' Addresses
Liuyan Han
China Mobile
No.32 Xuanwumen west street
Beijing, 100053
China
Email: hanliuyan@chinamobile.com
Haomian Zheng
Huawei Technologies
H1, Huawei Xiliu Beipo Village, Songshan Lake.
Dongguan
Guangdong, 523808
China
Email: Zhenghaomian@huawei.com
Minxue Wang
China Mobile
No.32 Xuanwumen west street
Beijing, 100053
China
Email: wangminxue@chinamobile.com
Yang Zhao
China Mobile
No.32 Xuanwumen west street
Beijing, 100053
China
Email: zhaoyangyj@chinamobile.com
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