Operations, Administration and Maintenance (OAM) for Computing-Aware Traffic Steering
draft-fu-cats-oam-fw-00
| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Authors | 付华楷 , Bo Liu , Zhenqiang Li , Daniel Huang , Cheng Huang , Liwei Ma , Wei Duan | ||
| Last updated | 2024-03-04 | ||
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draft-fu-cats-oam-fw-00
CATS H. Fu
Internet-Draft ZTE Corporation
Intended status: Standards Track B. Liu
Expires: 4 September 2024 Z. Li
China Mobile
D.H. Huang
C. Huang
L. Ma
W. Duan
ZTE Corporation
3 March 2024
Operations, Administration and Maintenance (OAM) for Computing-Aware
Traffic Steering
draft-fu-cats-oam-fw-00
Abstract
This document describes an OAM framework for Computing-Aware Traffic
Steering (CATS). The proposed OAM framework enables the fault and
the performance management of end-to-end connections from clients to
networks and finally to computing instances. In the following
sections, the major components of the framework, the functionalities,
and the deployment considerations are elaborated in detail.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 4 September 2024.
Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Requirements and Motivation . . . . . . . . . . . . . . . . . 4
5. Framework and Components . . . . . . . . . . . . . . . . . . 5
5.1. Component . . . . . . . . . . . . . . . . . . . . . . . . 6
5.2. Deployment Consideration . . . . . . . . . . . . . . . . 8
6. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 10
7. Management . . . . . . . . . . . . . . . . . . . . . . . . . 10
7.1. Indicator Collection . . . . . . . . . . . . . . . . . . 10
8. Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . 11
9. Security Considerations . . . . . . . . . . . . . . . . . . . 11
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
12.1. Normative References . . . . . . . . . . . . . . . . . . 11
12.2. Informative References . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13
1. Introduction
As described in [I-D.ietf-cats-usecases-requirements], edge computing
provides lower response time and higher transmission rate than cloud
computing by moving computing instances to the network edge. To meet
the requirements of users that are highly distributive, service
providers deploy the same type of service instances at multiple edge
sites, which involves steering traffic from clients to the most
appropriate computing instance.
Compute-aware traffic steering (CATS) [I-D.ldbc-cats-framework] is a
traffic engineering approach [I-D.ietf-teas-rfc3272bis] developed to
address the aforementioned traffic steering problem. This approach
takes into account the dynamic nature of both the computing resources
and the network states to optimize the way that traffic is forwarded
towards a given service instance. Various metrics can be taken into
account to devise and enforce such service-specific and computing-
aware traffic steering policies.
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To achieve better service assurance, it is necessary to not only
rapidly detect whether the QoS provided by the computing networks
meets the SLA requirements of clients, but also dynamically trigger
the calculation and the adjustment of both the computing and the
networking services. There are OAM technologies developed for
Carrier Networks, but these technologies are only deployed in the
network domain to facilitate the operations and the maintenance of
network operators, and cannot provide measurements of an end-to-end
connection from a client to a computing instance.
To this end, this document proposes an OAM architecture based on the
CATS framework to extend the coverage of the existing OAM
technologies from purely the network to an end-to-end connection from
a client to the network and finally to the computing instances.
Besides the architecture, the major components and the associated
deployment considerations are also described.
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
This document makes use of the terms defined in [I-D.ldbc-cats-
framework].
* FM: Fault Management.
* PM: Performance Monitoring.
* SI-OAM: Service Instance OAM.
* TC-OAM: Traffic Classifier OAM.
* AF-OAM: Application Flow OAM.
* IOAM: In-situ OAM.
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4. Requirements and Motivation
The main objectives of OAM are to detect anomalies before they
intensify, reduce the number of traffic flows impacted by these
abnormalities, and ensure that network operators fulfill their QoS
guarantee commitments to meet the Service Level Agreement(SLA) of
clients.
As a traffic engineering method, computing-aware traffic steering
(CATS) takes into account the dynamic nature of both the computing
resources and the network states to optimize the way that traffic is
forwarded toward a given service instance. However, existing OAM
technologies developed for the carrier network cannot be used to
collect metrics associated with the computing resources. Therefore,
it is necessary to extend the existing OAM technologies to build an
end-to-end OAM for CATS. Key objectives include:
* Accelerating the convergence of the CATS control plane: In CATS,
the status information of the computing instances is collected by
the CATS Service Metric Agent (C-SMA) component and processed at
the control plane for performance monitoring and failure
detection. However, such a processing process cannot adapt to the
rapid change of the computing instance status. Consequently, it
is necessary to rapidly detect the degradation of both the
computing instances and the network states on the data plane, and
trigger CATS Path Selector (C-PS) convergence to avoid black
holes.
* Closed-loop network SLA evaluation guarantee: In CATS, the CATS
Path Selector (C-PS) calculates and selects the paths towards
appropriate egress PEs and computing service instances. In this
process, it is necessary to verify whether the calculation and the
selection results meet the SLA requirements of clients taking into
account both the network states and the computing instance status.
* Closed-loop guarantee of service flow SLAs: In CATS, subsequent
packets of service flows in an established session are forwarded
through the CATS Traffic Classifier (C-TC) to the same service
instance. However, during such a process, the computing/network
performance may degrade. To ensure consistent experience for end
users, it is necessary to measure the flow-level performance of
service instances and make appropriate adjustments, e.g., change
segments of routing paths or enable backup paths, according to the
SLA requirements.
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* Service fault delimiting and troubleshooting: When user experience
deteriorates, it is necessary to rapidly locate the fault on the
end-to-end path from the user terminal through the network to the
service instance to implement fast end-to-end fault location and
troubleshooting.
5. Framework and Components
The CATS OAM architecture is shown in Fig. 1. In this architecture,
both the CATS router and the Underlay node are deployed with the
existing OAM technologies that are developed for the Carrier Network.
These OAM technologies are used to detect anomalies and monitor
service performance in the network domain, and can be divided into
three categories: link OAM, tunnel OAM, and service OAM.
* In link OAM, anomaly detection and performance monitoring are
conducted for a single Ethernet link. The link layer is an
optional sublayer implemented in the data link layer between the
Logical Link Control (LLC) and the MAC sublayer in the Open
Systems Interconnection (OSI) model. Common detection tools of
link OAM include IEEE-802 .3ah.
* A tunnel bears multiple services so the tunnel OAM must ensure
that the performance of a given service is not degraded when the
network fails or the number of services in the tunnel increases.
As a result, failure detection and performance monitoring are
conducted on the LSP layer to implement service protection.
Common detection tools of tunnel OAM include ITU-T Y.1711, MPLS-
LM-DM, BFD, etc.
* Service OAM is generally conducted for the L2VPN/L3VPN service
layer that is provided by the network to evaluate the service
quality and protect services. Common detection tools of service
OAM include ITU-T Y.1731, TWAMP, STAMP, etc.
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+--------------------+
/--->| Carrier OAM Domain |<--\
/ +--------------------+ \
/ \
| Service OAM |
|<--------------------------------->|
| |
| Tunnel OAM |
|<--------------------------------->|
| |
| Link OAM | Link OAM |
|<--------------->|<--------------->|
| | |
+------+ +--+--------+ +---+----+ +--------+--+ +--------+
|client+-+ CATS- +----+underlay+---+ CATS- +-+service |
| | |Forwarder 1| | node | |Forwarder 2| |instance|
+------+ +-----------+ +--------+ +-----------+ +----+---+
^ ^ ^ |
| | | |
| | +---+----+ |
| | | SI_OAM |<-->|
| +--+-----+ +--------+ |
| | TC_OAM |<------------------------------------->|
| +--+-----+ |
| | |
| +--+-----+ |
+----+ AF_OAM |<------------------------------------->|
+--+-----+ /
\ /
\ +-----------------+ /
\------->| CATS OAM Domain |<----------/
+-----------------+
Figure 1: CATS OAM Functional Components
5.1. Component
To achieve the four objectives mentioned in Chapter 3, we designed a
CATS OAM architecture based on the CATS architecture and the existing
OAM technologies that are developed for the carrier network. This
CATS OAM architecture can flexibly support existing OAM detection
tools, e.g., the ones mentioned in the previous section, and consists
of the following three components:
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* SI-OAM component: The functions of this component include (but are
not limited to) detecting the failures that happen between the
CATS-Forwarder 2 and the service instance, and measuring the
associated metrics such as latency, packet loss, and bandwidth.
The SI-OAM component generally would not dive into the internal
structure of the network between the CATS-Forwarder 2 and the
service instance and only makes the measurements of the end-to-end
connection. These measurements are generally fed back to the
C-SMA component to achieve faster failure detection and
performance monitoring than the CATS control plane, which fulfills
the first objective.
* TC-OAM component: The functions of this component include but are
not limited to detecting the failures that happen between the
CATS-Forwarder 1 and the service instance of a certain specific
ID, and measuring the associated metrics such as delay and packet
loss. The testing packets are delivered through the CATS Path
Selector (C-PS) to the associated service instance according to
the corresponding forwarding table entry of the CATS Traffic
Classifier (C-TC) to verify whether the measurements of the
connection meet the service level agreement (SLA) requirements.
And if it does not, recalculation is triggered, which fulfills the
second objective.
* AF-OAM component: The functions of this component include but are
not limited to measuring the metrics such as delay, packet loss,
and bandwidth, of the service flow in CATS. In general, the user
experience of an active connection may be affected by a number of
factors, such as the processing latency of the service instances
may increase or the network performance may degrade due to the
increase of the incoming traffic to the service instance. For
CATS-Forwarder 1, it is necessary to evaluate whether the SLA
requirements of service flows are achieved, and if the SLA
requirements are not achieved, conduct appropriate path
adjustments to compensate for the deviation as much as possible to
ensure the clients have consistent experience. For client
terminals, if the experience is degraded, it is necessary to
accurately locate where the problem occurs and quickly conduct
troubleshooting. Consequently, this component fulfills the third
and fourth objectives. It should be noted that related OAM tools
can also be developed, so that the entire network stack (L2-L7)
can be observed for applications and the entire network stack,
instead of merely traditional application-level visibility or
network-level visibility, providing a comprehensive solution for
operators' efficiency.
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5.2. Deployment Consideration
To demonstrate the complete CATS OAM procedure, a proper OAM
detection tool needs to be selected and deployed on the network and
service instance hosts of the CATS OAM architecture. The selection
of OAM detection tools is out of the scope of this document.
+-------------------------+
+--------------+ Intelligent controller +-------------+
| +-------------------+-----+ |
| | |
v v v
+-----------+ +-----------+ +--------+
| CATS- | | CATS- | | Edge |
|Forwarder 1| |Forwarder 2| | Site |
| | | |Service| |
+--------+ |+---------+| |+---------+|Metrics|S-ID 1 |
| client | || C-PS || +--------+ || C-SMA |<-------|SI-ID 1 |
| | |+---------+|Network| |Network|+---------+| | |
|+------+| | ^ ^ |Metrics|Underlay|Metrics| ^ | |S-ID 1 |
||AF-OAM|+--+ | | |<------+ domain |<------| | |-------|SI-ID 2 |
|+--+---+| | | | | +--------+ | +---+--+| OWAMP | |
| | | | | | | | |SI-OAM|<------>|S-ID 2 |
+---+----+ | |+---+--+| OWAMP | +------+| |SI-ID 1 |
| | ||TC-OAM|+------------------------+-----------+------>| |
| | |+------+| | | |S-ID 2 |
| | ++-------+| IOAM | | |SI-ID 2 |
| | | AF-OAM |+------------------------+-----------+------>| |
| | +--------+| IOAM | | | |
+-------+-----------+------------------------+-----------+------>| |
+-----------+ +-----------+ +--------+
Figure 2: An Example Of CATS OAM Deployment
As illustrated in Fig. 2, the OWAMP and the IOAM tools are selected
as examples to describe how the CATS OAM component works with these
detection tools to fulfill the four objectives :
* Accelerating the convergence of the CATS control plane: The SI-OAM
component is deployed on the CATS-Forwarder 2 and the OWAMP tool
is used to measure the delay and packet loss from the CATS-
Forwarder 2 to the associated service instance. The source and
the destination IP of the detection packets are the CATS-Forwarder
2 interface IP and the service instance IP, respectively.
According to the returned packets, the status and the metrics of
both the service instance and the network that connects the
service instance with the clients are obtained. The SI-OAM
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component feeds back the measurement results to the C-SMA
component, which further spreads the computing resource
information in the CATS network to accelerate CATS Path Selector
(C-PS) convergence to avoid black holes.
* Closed-loop network SLA guarantee: The TC-OAM component is
deployed on the CATS-Forwarder 1 and the OWAMP tool is used to
measure the delay and packet loss from the CATS-Forwarder 1 to the
associated service instance. To ensure OWAMP packets are
delivered according to the table item of TC, the source and the
destination IP addresses of the detection packets are set to the
IP address of the interface of CATS-Forwarder 1 and the IP address
corresponding to the service ID, respectively. OWAMP packets
usually pass through the tunnel to the egress network and are
forwarded to the service instance. According to the returned
OWAMP packets, the TC-OAM obtains the measurement results and
feeds back the results to the C-PS component. If the measurement
results deviate from the expected SLAs, recalculation is triggered
to fulfill the closed-loop network SLA guarantee for the service
ID.
* Closed-loop SLA guarantee for service flow: for service flows that
have been initiated, the flow affinity function is executed to
guarantee that subsequent packets reach the same service instance
as the first packet. To conduct measuring and performance
monitoring for the entire end-to-end flows, the flow-based
detection tool such as IOAM is selected and the AF-OAM component
is deployed on the CATS-Forwarder 1. Note that the PostCard or
the PassPort modes are generally used in the flow-based detection
and a centralized collector is required to obtain the measurement
results and feed the results back to the C-PS. The network path
can be adjusted according to the difference between the OAM
measurement results and the SLA requirements to ensure a
consistent user experience.
* Service fault delimiting and troubleshooting: For fast
delimitation and troubleshooting under user experience
degradation, the AF-OAM component can be deployed on a user
terminal when a flow detection tool such as IOAM is performed.
The IOAM can use the postcard mode and can directly report the
location where packet loss or longer delay occurs according to the
measurement results obtained by a centralized collector. This is
a typical scenario of IOAM, and details are not described herein.
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6. Operation
The OAM architecture proposed in this document enables CATS to
provide robust operations capabilities while forwarding and routing.
It should be noted that both the testing packets and the data packets
should be delivered via the same path i.e., performance monitoring
must be conducted in-band, and the testing traffic must not affect
the data traffic. As a result, the testing traffic does shares the
treatments with the data flow being monitored but does not introduce
congestion when the network functions normally.
To be added.
7. Management
It is necessary to disclose a set of metrics to support the decision
of the operator. The following performance metrics are useful:
* Delay: elapsed time from the serving gateway to the service
instance.
* Packet loss: the number of lost packets divided by the total
number of packets being transmitted from the serving gateway to
the compute instance.
* For each CATS traffic flow, at least one metric that reflects the
end-to-end performance is reported.
* If multiple paths are used for service protection, the paths that
malfunction are detected.
* The service instances that malfunction are detected.
To be added.
7.1. Indicator Collection
The number of metrics and the frequency that these metrics are
collected need to be considered when designing the OAM mechanism.
The OAM mechanism may be distributed, centralized, or both. The
mechanism may be executed periodically or triggered by an event.
To be added.
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8. Maintenance
Service protection is designed to mitigate simple network failures
faster than the response time expected from the CATS control plane.
In the events that affect network operations, e.g., link contexts
change, network and computing devices crash/restart, and traffic
starts/ends, the CATS control plane needs to perform remediation and
re-optimization operations to ensure SLAs of all active flows are
satisfied. The control plane should continuously obtain the network
status and evaluate whether the current configurations are suitable.
To be added.
9. Security Considerations
TBD.
10. Acknowledgements
To be added upon contributions, comments and suggestions.
11. IANA Considerations
TBA
12. References
12.1. Normative References
[I-D.ldbc-cats-framework]
Li, C., Du, Z., Boucadair, M., Contreras, L. M., and J.
Drake, "A Framework for Computing-Aware Traffic Steering
(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>.
[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>.
[RFC4656] Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M.
Zekauskas, "A One-way Active Measurement Protocol
(OWAMP)", RFC 4656, DOI 10.17487/RFC4656, September 2006,
<https://www.rfc-editor.org/info/rfc4656>.
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[RFC7276] Mizrahi, T., Sprecher, N., Bellagamba, E., and Y.
Weingarten, "An Overview of Operations, Administration,
and Maintenance (OAM) Tools", RFC 7276,
DOI 10.17487/RFC7276, June 2014,
<https://www.rfc-editor.org/info/rfc7276>.
[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>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.
[RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J.,
Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
(SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020,
<https://www.rfc-editor.org/info/rfc8754>.
[RFC9378] Brockners, F., Ed., Bhandari, S., Ed., Bernier, D., and T.
Mizrahi, Ed., "In Situ Operations, Administration, and
Maintenance (IOAM) Deployment", RFC 9378,
DOI 10.17487/RFC9378, April 2023,
<https://www.rfc-editor.org/info/rfc9378>.
12.2. Informative References
[I-D.ietf-cats-usecases-requirements]
Yao, K., Trossen, D., Boucadair, M., Contreras, L. M.,
Shi, H., Li, Y., Zhang, S., and Q. An, "Computing-Aware
Traffic Steering (CATS) Problem Statement, Use Cases, and
Requirements", Work in Progress, Internet-Draft, draft-
ietf-cats-usecases-requirements-02, 1 January 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-cats-
usecases-requirements-02>.
[I-D.ietf-teas-rfc3272bis]
Farrel, A., "Overview and Principles of Internet Traffic
Engineering", Work in Progress, Internet-Draft, draft-
ietf-teas-rfc3272bis-27, 12 August 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-teas-
rfc3272bis-27>.
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[I-D.li-dyncast-architecture]
Li, Y., Iannone, L., Trossen, D., Liu, P., and C. Li,
"Dynamic-Anycast Architecture", Work in Progress,
Internet-Draft, draft-li-dyncast-architecture-08, 16
January 2023, <https://datatracker.ietf.org/doc/html/
draft-li-dyncast-architecture-08>.
Authors' Addresses
Huakai Fu
ZTE Corporation
Wuhan
China
Email: fu.huakai@zte.com.cn
Bo Liu
China Mobile
Beijing
China
Email: liubo@chinamobile.com
Zhenqiang Li
China Mobile
Beijing
China
Email: lizhenqiang@chinamobile.com
Daniel Huang
ZTE Corporation
Nanjing
China
Email: huang.guangping@zte.com.cn
Cheng Huang
ZTE Corporation
Shanghai
China
Email: huang.cheng13@zte.com.cn
Liwei Ma
ZTE Corporation
Nanjing
China
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Email: ma.liwei1@zte.com.cn
Wei Duan
ZTE Corporation
Nanjing
China
Email: duan.wei1@zte.com.cn
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