Service Announcement Methods for CATS
draft-gao-cats-service-announcement-00
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| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Authors | Shuai Gao , Zhenghao Hu , Xiaoting Ma , 徐子恒 | ||
| Last updated | 2024-11-02 | ||
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draft-gao-cats-service-announcement-00
cats S. Gao
Internet-Draft Z. Hu
Intended status: Standards Track Beijing Jiaotong University
Expires: 7 May 2025 X. Ma
Z. Xu
China Telecom
3 November 2024
Service Announcement Methods for CATS
draft-gao-cats-service-announcement-00
Abstract
This document introduces network-layer service announcement solutions
based on architecture defined in [I-D.ldbc-cats-framework]. In
particular, the scheme describes how to disseminate computing service
information to clients and the control plane through service
announcement messages. This draft also proposes to classify the
attributes used to describe computing services and analyzes several
service querying mechanisms.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 7 May 2025.
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Analysis for DNS-based service announcement . . . . . . . . . 3
5. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 4
6. Computing service Attributes Classification . . . . . . . . . 6
6.1. Computing service Demand Attributes . . . . . . . . . . . 6
6.1.1. Computing resource demand . . . . . . . . . . . . . . 6
6.1.2. Network resource demand . . . . . . . . . . . . . . . 7
6.2. Computing service Information Attributes . . . . . . . . 7
7. Workflow of Network-layer Service Announcement . . . . . . . 7
7.1. Service Registration . . . . . . . . . . . . . . . . . . 7
7.2. Service Update . . . . . . . . . . . . . . . . . . . . . 8
7.3. Service Announcement Message . . . . . . . . . . . . . . 8
8. Service querying mechanism . . . . . . . . . . . . . . . . . 8
8.1. Centralized model . . . . . . . . . . . . . . . . . . . . 9
8.2. Distributed model . . . . . . . . . . . . . . . . . . . . 9
9. Security Considerations . . . . . . . . . . . . . . . . . . . 9
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
11.1. Normative References . . . . . . . . . . . . . . . . . . 9
11.2. Informative References . . . . . . . . . . . . . . . . . 9
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
As described in [draft-ietf-cats-framework-02], steering in CATS aims
to select the suitable service contact instance(s) from a set of
candidates. Particularly, the CATS architecture gives the
exemplifications of the service announcement workflow for distributed
design. However, the CATS framework does not provide the detailed
description of the specific process of service announcement.
Additionally, the application-layer DNS solutions for name resolution
in CATS face challenges in adapting to high-frequency dynamic
resolution and result in significant signaling overhead.
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This document proposes network-layer service announcement solutions
for CATS based on identifier resolution and mapping, and classifies
the attributes used to describe computing services. Several service
querying mechanisms are further analyzed based on the proposed
solutions.
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 [draft-ietf-cats-
framework-04]. In addition, the following terms are defined below:
*Computing service Attributes (CSA):* Attributes that multi-
dimensionally describe the computing service.
*Computing service Demand Attributes (CSDA):* Attributes that
describe the computing resources and network resources requirements
of the computing service.
*Computing service Information Attributes (CSIA):* Attributes that
detail the nature of the computing service and the methods of its
provision.
4. Analysis for DNS-based service announcement
The service announcement using the DNS mechanism involves the
following two phases:
Phase 1: When a computing service is instantiated at the service
site, it sends a registration message to the domain name server,
which includes the computing service's CS-ID and the network
identifier of the service site.
Phase 2: When a user requests a computing service, the CS-ID is sent
to the domain name server for hierarchical querying to obtain the
network identifier of the service site for communication.
However, using the DNS mechanism for service announcements faces
several challenges:
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The DNS mechanism is not designed for high-frequency resolution.
When the client first requests a computing service with CS-ID, the
mapping result is typically recorded and is used for subsequent
requests until the cache expires. Due to the dynamic nature of
computing resources at service sites, if the client continues to
request the same site based on a cached copy, the site or its
connecting links may be occupied, making it suboptimal for providing
the CS-ID specified computing service.
DNS service is normally at the application layer (Layer 7), and the
signaling flow between the service site and the DNS server would
introduce additional overhead. In CATS, a service site can provide
multiple computing services and a single computing service could be
accessed through multiple service sites. The resources occupied by
one computing service at the service site may also affect the
availability of other computing services. Thus, multiple edge sites
need to frequently announce the services they provide and their
availability to the DNS server, leading to network resource
consumption.
The resources of DNS servers are limited. Besides responding to
client mapping requests, frequent interactions with service sites
will consume a considerable amount of resources. Moreover, updating
and checking the information database at a high refresh rate can
potentially overload the servers.
5. Overview
As illustrated in Figure 1, a computing service is identified by a
unique CS-ID and instantiated through multiple edge service sites to
enable client access. CATS functional components are deployed at the
ingress CATS-Forwarder and egress CATS-Forwarder, where the C-SMA is
tasked with gathering the status of the service sites and service
instances, and interfacing with the control plane. The control plane
utilizes this information to perform service scheduling. When a user
node connects to the network, to protect the privacy of users, the
scheme employs a hashing algorithm to generate unique anonymous
identity identifiers for each user during the registration process.
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+---------+ |
| Client | |
+----+----+ |
| |
| |
+--------+--------+ |
| CATS-Forwarder 1| |
|--------+--------| |
| C-NMA | |
+--------+--------+ |
| | +---------+
+--+----------+--------------+--+ | | Control |
| Underlay | | | Plane |
| Infrastructure | | +---------+
+--+-------------+-----------+--+ |
| | |
+--------+--------+ +--------+--------+ |
| CATS-Forwarder 2| | CATS-Forwarder 3| |
|--------+--------| |--------+--------| |
| C-SMA | | C-SMA | |
+--------+--------+ +--------+--------+ |
| | |
| | |
+------+-----+ +----+------+ |
+------------+ | +------------+ | |
| Service | | | Service | | |
| Contact | | | Contact | | |
| Instance |-+ | Instance |-+ |
+------------+ +------------+ |
Service site 1 Service site 2
Figure 1: CATS Service Announcement Workflow
The service announcement process is established between the ingress
forwarder, the egress forwarder, and the control plane. After a
computing service is instantiated on a specific service site, the
brief service information and the service deployment status need to
be reported. The Service Contact Instance then updates it to the
connected egress CATS-Forwarders ("CATS-Forwarder 2/3"). And the
status is collected by C-SMAs and uploaded to the controllers. When
receiving the information of a new type of computing service, the
control plane is responsible for generating the CS-ID and sending it
to the egress CATS-Forwarder, which subsequently disseminates it to
other forwarders.
In particular, for any computing service deployed in the CATS for the
first time, the control plane could request the service instance to
upload service demands and service attributes, which are associated
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with the CS-ID. The information may then be relayed to the C-PS in
order to orchestrate the network and computing resources for
computing service requests, thereby ensuring the quality of service.
When querying the computing service, the clients do not need to
memorize the specific CS-ID, but describe their intentions by the
service attributes and map them to the CS-ID by the controllers (in
centralized model) or themselves (in distributed model). A service
request carrying CS-ID as the destination address is successively
routed to the ingress CATS-Forwarder, and is forwarded to the egress
CATS-Forwarder through the path computed by the C-PS component. At
egress CATS-Forwarder, the requests are forwarded to the
corresponding service contact instance which selects the instance
that can provide the service.
6. Computing service Attributes Classification
To enable the control plane to understand the characteristics of
different computing services and schedule network and computing
resources based on clients' demands, this document propose to
classify the computing service attributes and upload to the control
plane during the workflow of service announcement. Computing service
attributes could be categorized into two types: Computing service
Demand Attributes and Computing service Information Attributes. CSDA
describes the computing resources and network resources requirements
of the service, and CSIA details the nature of the computing service
and the methods of its provision.
6.1. Computing service Demand Attributes
Computing service demand attributes can be categorized into computing
resource demand and network resource demand.
6.1.1. Computing resource demand
Computing resource demand includes but not limited to the following
items.
Computing capability type: describes the computation type required to
run computing services, which could be categorized into logical
computing capability, parallel computing capability, neural network
computing capability and so on;
Computing performance: specifies the required computational
performance to ensure the quality of computing services, typically
measured in operations per second, such as FLOPS;
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Memory capacity: describes the memory size required by computing
services;
Disk capacity: describes the required disk size to ensure the quality
of computing service.
6.1.2. Network resource demand
Network resource demands define the network performance metrics to
guarantee the service experience, including latency, RTT, bandwidth,
jitter, and packet loss rate.
6.2. Computing service Information Attributes
Computing service information attributes include but not limited to
service model, service type, service provider, service name, and
service attribution domain.
Service model: Differentiate the methods how service sites provide
computing services, such as infrastructure services, platform
services, and software services.
Service type: Specify the types of computing services, such as video
rendering, scientific computing, cloud AR/VR, etc.
Service provider: Identify who provide the computing service.
Service name: Specifies the name of the computing service.
Service domain: Describe the area where the computing service is
provided.
7. Workflow of Network-layer Service Announcement
The service announcement processing and handling procedures could be
divided into two parts: service registration and service update.
7.1. Service Registration
For a new computing service that has not been registered in CATS
domain, the service contact instance is first notified of the service
information attributes after the computing service is instantiated at
the service site. It looks up the cache that stores the service
deployment information, and announce it to C-SMA through the network
layer service registration message if this is a new computing
service.
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Subsequently, if C-SMA also detects that the computing service has
not been registered, the service information attributes would be sent
to the control plane encapsulated in the registration packet. When
the registration packet is received by the control plane, it
generates a CS-ID for this new computing service and replies it to
the C-SMA. At C-SMA, CS-ID is encapsulated in service registration
response message and diffused to other CATS-Forwarders.
Additionally, the controller plane could request computing service
demand attributes from the service site that registered the new CS-
ID. This request is forwarded from the control plane to the service
site via the C-SMA. When the service site receives the request, it
returns the requested computing service demand attributes to the
control plane.
7.2. Service Update
To ensure integrated management of computing services, the control
plane needs to maintain a database of CS-IDs and related service
attributes. The information database includes an expiration time for
the mapping relationship, which encompasses the CS-ID and its bound
CIS-ID, as well as the CS-ID and its computing service attributes.
When the controller detects the expiration of the former mapping, it
sends an update request message to the service contact instance and
obtains the response information. If there is an update to the
mapping relationship, the control plane sends an update message to
the CATS-Forwarder, which then disseminates the update message; when
a CS-ID is no longer bound to any CIS-ID, the latter mapping enters
the expiration state and the control plane should decide whether to
clear the binding relationship based on remain cache size.
Additionally, when a service contact instance detects a change in the
state of a service instance, such as the addition of a new instance
of an available computing service or the removal of a service by the
service site, it should send a service update message to the C-SMA.
At C-SMA, two steps would be taken: 1. send a service update message
to the control plane announcing the change in the mapping
relationship between the CS-ID and the CIS-ID; 2. send a service
update message to the other CATS-Forwarders to announce the service
update.
7.3. Service Announcement Message
TBD
8. Service querying mechanism
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8.1. Centralized model
The client does not need to memorize the CS-ID, but describe
intentions by computing service information attributes. Before
service request, a service querying packet carrying the clients'
address and the computing service information attributes is
constructed and sent to the control plane via CATS-Forwarder. When
the controller receives the packet, it interprets and parses the
computing service information attributes in the packet. The
attributes are typically mapped to a CS-ID or a set of alternative
CS-IDs, and the mapping result is subsequently returned to clients.
8.2. Distributed model
In the distributed model, the CS-ID may contain semantics such as
service type, service name and other service information attributes.
The client could construct the CS-ID according to computing service
intents and encapsulates it into the service request packet, which is
then routed to the ingress CATS-Forwarder. At ingress CATS-
Forwarder, The request is matched by the C-PS component to select the
service instance as well as the network path that satisfy the
computing service demand attributes.
9. Security Considerations
TBD
10. IANA Considerations
TBD
11. References
11.1. 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>.
11.2. Informative References
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[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>.
Acknowledgements
TBD
Authors' Addresses
Shuai Gao
Beijing Jiaotong University
Beijing
China
Email: shgao@bjtu.edu.cn
Zhenghao Hu
Beijing Jiaotong University
Beijing
China
Email: 24110054@bjtu.edu.cn
Xiaoting Ma
China Telecom
Beijing
China
Email: maxt3@chinatelecom.cn
Ziheng Xu
China Telecom
Beijing
China
Email: xuzh24@chinatelecom.cn
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