Internet DRAFT - draft-yi-cats-hierarchical-metric-distribution
draft-yi-cats-hierarchical-metric-distribution
CATS X. Yi, Ed.
Internet-Draft N. Zhang, Ed.
Intended status: Standards Track China Unicom
Expires: 5 September 2024 H. Shi
Huawei
4 March 2024
Hierarchical methods of computing metrics distribution
draft-yi-cats-hierarchical-metric-distribution-00
Abstract
This document analyzes the necessarity of setting hierarchical
methods of computing metrics distribution. Besides, we propose the
workflow of hierarchical metric distribution for different CATS
frameworks.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 2
1.2. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Conventions and Definitions . . . . . . . . . . . . . . . . . 3
3. Definition and requirements of hierarchical metric
distribution . . . . . . . . . . . . . . . . . . . . . . 3
4. Optional hierarchical parameters . . . . . . . . . . . . . . 5
4.1. Geographical scope . . . . . . . . . . . . . . . . . . . 5
4.2. Number of service sites . . . . . . . . . . . . . . . . . 5
4.3. Other Options . . . . . . . . . . . . . . . . . . . . . . 5
5. Workflow of hierarchical metric distribution . . . . . . . . 5
5.1. Distributed model . . . . . . . . . . . . . . . . . . . . 6
5.2. Centralized model . . . . . . . . . . . . . . . . . . . . 6
5.3. Hybrid model . . . . . . . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . 6
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
8. Normative References . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
The path computation needs to process both network and computing
metrics in CATS. As described in [I-D.ldbc-cats-framework], after
the computing metrics are collected, they will be distributed to CATS
Path Selector (C-PS) for path computation. The C-PS can be
integrated into ingress CATS-Forwarders or deployed as a functional
component of a centralized controller. Computing metrics are defined
in [I-D.du-cats-computing-modeling-description]. And
[I-D.yao-cats-ps-usecases] describes the importance of the
representation and encoding of computing metrics. As service scale
increases, the data amount reported to C-PS and size of routing table
increases, which will bring greater processing pressure to network
devices. As a result, the service quality will be affected.
Therefore, it is necessary to set a hierarchical method of computing
metric distribution between service site and different C-PSes. The
hierarchical method can be set according to geographical scope
(distance or radius) or number of service sites, etc.
1.1. Terminology
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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. Conventions and Definitions
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. This document uses terms defined in
[I-D.ldbc-cats-framework]. We list them below for clarification. -
Computing-Aware Traffic Steering (CATS): An architecture that takes
into account the dynamic nature of computing resources and network
state to steer service traffic to a service instance. This
dynamicity is expressed by means of relevant metrics. - Ingress CATS-
Forwarder: An entity that steers service-specific traffic along a
CATS-computed path that leads to an Egress CATS-Forwarder that
connects to the most suitable service site that host the service
contact instance selected to satisfy the initial service request. -
Egress CATS-Forwarder: An entity that is located at the end of a
CATS-computed path and which connects to a CATS-serviced site. - CATS
Path Selector (C-PS): An entity that determines the path toward the
appropriate service location and service instances to meet a service
demand given the service status and network status information.
3. Definition and requirements of hierarchical metric distribution
The hierarchical method of cpmputing metrics is based on the CATS
framework defined in [I-D.ldbc-cats-framework](see Figure 1, the
figure is replicated here for better understanding).
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+-----+ +------+ +------+
+------+| +------+ | +------+ |
|client|+ |client|-+ |client|-+
+---+--+ +---+--+ +---+--+
| | |
| +----------------+ | +-----+----------+
+-+ C-TC#1 +-+ +-----+ C-TC#2 |
|----------------| | |----------------|
| |C-PS#1 | +------+ |CATS-Forwarder 4|
......| +----------|....|C-PS#2|..| |...
: |CATS-Forwarder 2| | | | | .
: +----------------+ +------+ +----------------+ :
: :
: +-------+ :
: Underlay | C-NMA | :
: Infrastructure +-------+ :
: :
: :
: +----------------+ +----------------+ :
: |CATS-Forwarder 1| +-------+ |CATS-Forwarder 3| :
:.| |..|C-SMA#1|.... | |....:
+---------+------+ +-------+ +----------------+
| | | C-SMA#2 |
| | +-------+--------+
| | |
| | |
+------------+ +------------+
+------------+ | +------------+ |
| Service | | | Service | |
| Contact | | | Contact | |
| Instance |-+ | Instance |-+
+------------+ +------------+
service site 1 service site 2
Figure 1: CATS-Functional-Components
The hierarchical metric distribution is defined as reporting
different levels of the computing metric to different C-PSes
according to geographical scope (distance or radius) or number of
service sites, etc. The C-PS classified as high priority receive
high-level computing metrics (full metric information). And the C-PS
classified as low priority only receives a simple computing metric
(i.e. available or unavailable). If the priorities are classified by
distance, then the near C-PS can be set to a higher priority. On the
one hand, setting a hierarchical method of computing metric
distribution can reduce the processing pressure of network devices
and the size of distribution data and routing table. On the other
hand, the increase in service delay caused by processing large
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amounts of data can be avoided. The impact is particularly obvious
when C-PS is deployed in CATS-Forwader. Therefore, hierarchical
method of computing metric distribution is particularly important in
distributed and hybrid model. In the distributed model，all computing
metrics are processed in C-PS in the ingress CATS-Forwarder. It is
better to set a suitable priority for each ingress CATS-Forwarder.
Therefore, the processing pressure of the CATS-Forwarder can be
relieved while maintaining sufficient service resource utilization.
In the centralized model, all computing metrics are processed in
centralized C-PS. A centralized C-PS may have a hierarchical control
system, and different levels of controllers can be set to receive
different levels of the computing metric. In the hybrid model,
computing metrics can be chosen to be processed in the ingress CATS-
Forwarder or centralized C-PS according to service types.
[I-D.yi-cats-hybrid-solution] has discussed how to choose the
appropriate processing location in different scenarios. Because not
all computing metrics need to be processed in the CATS-Forwarder in
hybrid model, the hierarchical method can be more flexible.
4. Optional hierarchical parameters
There are many options for classification according to what
parameters.
4.1. Geographical scope
If prioritizing based on geographic scope, whether the distance
between each network device is known needs to be considered. If the
distance is unknown, the distance can be measured through the network
packet transmission delay.
4.2. Number of service sites
TBD
4.3. Other Options
TBD
5. Workflow of hierarchical metric distribution
For different CATS frameworks, the workflow of hierarchical metric
distribution is different.
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5.1. Distributed model
The hierarchical policies are set in egress CATS-Forwarder.When an
egress CATS-Forwarder establishes a one-to-one neighbor relationship
with an ingress CATS-Forwarder, the egress CATS-Forwader determines
what level of computing metric to report to C-PS in this ingress
CATS-Forwarder.
5.2. Centralized model
The hierarchical policies are directly set in the hierarchical
controller of the centralized C-PS to determine what level of
computing metric will be received from different service sites.
5.3. Hybrid model
The hierarchical policies are set in both egress CATS-Forwarder and
centralized C-PS. Firstly, the egress CATS-Forwarder determine
whether to report the collected computing metrics to centralized C-PS
or C-PS in the ingress CATS-Forwarder according to the requirements
(delay or global utilization, etc.) of different service types. If
the CATS-Forwarder is selected, the hierarchical metric distribution
workflow follows the distributed model mentioned above. If there is
hierarchical control in hybrid model, the hierarchical metric
distribution workflow follows the centralized model mentioned above.
6. Security Considerations
TBD
7. IANA Considerations
TBD
8. 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>.
[I-D.ldbc-cats-framework]
Li, C., Du, Z., Boucadair, M., Contreras, L. M., and J.
Drake, "A Framework for Computing-Aware Traffic Steering
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Internet-Draft Hierarchical metric distribution for CAT March 2024
(CATS)", Work in Progress, Internet-Draft, draft-ldbc-
cats-framework-06, 8 February 2024,
<https://datatracker.ietf.org/doc/html/draft-ldbc-cats-
framework-06>.
[I-D.yao-cats-ps-usecases]
Yao, K., Trossen, D., Boucadair, M., Contreras, L. M.,
Shi, H., Li, Y., and S. Zhang, "Computing-Aware Traffic
Steering (CATS) Problem Statement, Use Cases, and
Requirements", Work in Progress, Internet-Draft, draft-
yao-cats-ps-usecases-03, 30 June 2023,
<https://datatracker.ietf.org/doc/html/draft-yao-cats-ps-
usecases-03>.
[I-D.du-cats-computing-modeling-description]
Du, Z., Fu, Y., Li, C., Huang, D., and Z. Fu, "Computing
Information Description in Computing-Aware Traffic
Steering", Work in Progress, Internet-Draft, draft-du-
cats-computing-modeling-description-02, 23 October 2023,
<https://datatracker.ietf.org/doc/html/draft-du-cats-
computing-modeling-description-02>.
[I-D.yi-cats-hybrid-solution]
Yi, X., Pang, R., and H. Shi, "Hybrid Computing and
Network Awareness and Routing Solution for CATS", Work in
Progress, Internet-Draft, draft-yi-cats-hybrid-solution-
02, 22 October 2023,
<https://datatracker.ietf.org/doc/html/draft-yi-cats-
hybrid-solution-02>.
Authors' Addresses
Xinxin Yi (editor)
China Unicom
Beijing
China
Email: yixx3@chinaunicom.cn
Naihan Zhang (editor)
China Unicom
Beijing
China
Email: zhangnh12@chinaunicom.cn
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Hang Shi
Huawei
Beijing
China
Email: shihang9@huawei.com
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