Distribution of Service Metadata in BGP-LS
draft-ls-idr-bgp-ls-service-metadata-01
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|---|---|---|---|
| Authors | Cheng Li , Hang Shi , Tao He , Ran Pang , Guofeng Qian | ||
| Last updated | 2023-04-18 (Latest revision 2023-02-24) | ||
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draft-ls-idr-bgp-ls-service-metadata-01
Inter-Domain Routing C. Li, Ed.
Internet-Draft H. Shi, Ed.
Intended status: Standards Track Huawei Technologies
Expires: 28 August 2023 T. He
R. Pang
China Unicom
G. Qian
Huawei Technologies
24 February 2023
Distribution of Service Metadata in BGP-LS
draft-ls-idr-bgp-ls-service-metadata-01
Abstract
In edge computing, a service may be deployed on multiple instances
within one or more sites, called edge service. The edge service is
associated with an ANYCAST address in IP layer, and the route of it
with potential service metatdata will be distributed to the network.
The Edge Service Metadata can be used by ingress routers to make path
selections not only based on the routing cost but also the running
environment of the edge services.
The service route with metadata can be collected by a PCE(Path
Compute Element) or an analyzer for calculating the best path to the
best site/instance. This draft describes a mechanism to collect the
information of the service routes and related service metadata in
BGP-LS.
About This Document
This note is to be removed before publishing as an RFC.
The latest revision of this draft can be found at
https://VMatrix1900.github.io/draft-service-metadata-in-BGP-LS/draft-
ls-idr-bgp-ls-service-metadata.html. Status information for this
document may be found at https://datatracker.ietf.org/doc/draft-ls-
idr-bgp-ls-service-metadata/.
Discussion of this document takes place on the Inter-Domain Routing
Working Group mailing list (mailto:idr@ietf.org), which is archived
at https://mailarchive.ietf.org/arch/browse/idr/. Subscribe at
https://www.ietf.org/mailman/listinfo/idr/.
Source for this draft and an issue tracker can be found at
https://github.com/VMatrix1900/draft-service-metadata-in-BGP-LS.
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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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This Internet-Draft will expire on 28 August 2023.
Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
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Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. BGP-LS Extension for Service in a Site . . . . . . . . . . . 3
2.1. Prefix NLRI . . . . . . . . . . . . . . . . . . . . . . . 4
2.2. Attributes . . . . . . . . . . . . . . . . . . . . . . . 4
2.2.1. Metadata Path Attribute TLV . . . . . . . . . . . . . 5
2.3. Prefix SID Attribute TLV . . . . . . . . . . . . . . . . 6
2.3.1. Color Attribute TLV . . . . . . . . . . . . . . . . . 6
3. Security Considerations . . . . . . . . . . . . . . . . . . . 7
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
5. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 8
6. Normative References . . . . . . . . . . . . . . . . . . . . 8
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
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1. Introduction
Many services deploy their service instances in multiple sites to get
better response time and resource utilization. These sites are often
geographically distributed to serve the user demand. For some
services such as VR/AR and intelligent transportation, the QoE will
depend on both the network metrics and the compute metrics. For
example, if the nearest site is overloaded due to the demand
fluctuation, then steer the user traffic to a another light-loaded
sites may improve the QoE.
[I-D.ietf-idr-5g-edge-service-metadata] descirbes the BGP extension
of distributing service route with network and computing-related
metrics. The router connected to the site will received the service
routes and service metadata sent from devices inside the egdge site,
and then generates the corresponding routes and distributes them to
ingress routers. However, the route with service metadata on the
router connected to the site can be also collected by a central
Controller for calculating the best path to the best site.
This document defines an extension of BGP-LS to carry the service
metadata along with the service route. Using the service metadata
and the service route, the controller can calculate the best site for
the traffic, giving each user the best QoE.
1.1. Terminology
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. BGP-LS Extension for Service in a Site
The goal of the BGP-LS extension is to collect the information of the
service prefix and metadata of the service, such as network metrics
and compute metrics. A service is identified by an prefix, and this
information is carried by existing prefix NLRI TLV. Other
information including service metadata are carried by attributes
TLVs.
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2.1. Prefix NLRI
A service is identified by a prefix, and the Prefix NLRI defined in
the [RFC7752] is used to collect the prefix information of the
service. The format of the Prefix NLRI is shown in Figure 1 for
better understanding.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+
| Protocol-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identifier |
| (64 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Local Node Descriptors (variable) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Prefix Descriptors (variable) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: The IPv4/IPv6 Topology Prefix NLRI Format
Specifically, the service prefix is carried by the IP Reachability
Information TLV(Figure 2) inside the Prefix Descriptor field. The
Prefix Length field contains the length of the prefix in bits. The
IP Prefix field contains the most significant octets of the prefix.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix Length | IP Prefix (variable) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: IP Reachability Information TLV Format
2.2. Attributes
The following three prefix attribute TLVs are used to carry the
metadata of a service instance:
1. Metadata Path Attribute TLV carries the compute metric of the
service instance such as site preference, capacity index and load
measurement defined in [I-D.ietf-idr-5g-edge-service-metadata].
2. Prefix SID TLV carries a Prefix SID associated to the edge site.
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3. Color Attribute TLV carries the service requirement level
information of the service
2.2.1. Metadata Path Attribute TLV
The Metadata Path Attribute TLV is an optional attribute to carry the
Edge Service Metadata defined in the
[I-D.ietf-idr-5g-edge-service-metadata]. It contains multiple sub-
TLVs, with each sub-TLV containing a specific metric of the Edge
Service Metadata. This document define a new TLV in BGP-LS, which
reuse the name and the format of Metadata Path Attribute TLV.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Value (multiple Metadata sub-TLVs) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Metadata Path Attribute TLV format
* Type: identify the Metadata Path Attribute, to be assigned by
IANA.
* Length: the total number of the octets of the value field.
* Value: contains multiple sub-TLVs.
There are three types of Edge Service Metadata sub-TLVs defined in
[I-D.ietf-idr-5g-edge-service-metadata]:
1. Site Preference Index indicates the preference to choose the
site.
2. Capacity Index indicates the capability of a site. One Edge Site
can be in full capacity, reduced capacity, or completely out of
service.
3. Load Measurement indicates the load level of the site.
To collect these information, this document defines TLVs reusing the
name and format of the TLVs defined in
[I-D.ietf-idr-5g-edge-service-metadata].
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2.3. Prefix SID Attribute TLV
In some cases, there may be multiple sites connect to one
Edge(egress) router through different interfaces. Generally, a
overlay path, such a overlay tunnel will be used between the ingress
router and the egress for steering the traffic to the best site
correctly. In SR-MPLS networks or SRv6 networks, a prefix SID is
needed. For example, some SRv6 Endpoint Behaviors such as End.DX6,
End.X can be encoded for each site so that the egress router can
steer the traffic to the corresponding site. The Prefix SID TLV
defined [RFC9085] can be used to collect this information.
The Prefix SID TLV is an optional TLV to carry the Prefix SID
associated to the edge site. The TLV format is illustrated in
Figure 4.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Value (Prefix SID sub-TLV) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Prefix-SID TLV format
* Type: 1158, identify the Prefix SID Attribute.
* Length: the total number of the octets of the value field.
* Value: contains Prefix SID sub-TLV.
2.3.1. Color Attribute TLV
Color is used to indicate the service level. For example, different
site may have different level of service capability which is taken
into account of by the controller when calculate the path to the
egress router. More details can be added in the future revision.
The TLV format(shown in Figure 5) is similar to the BGP Color
Extended Community defined in [RFC9012].
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Color Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Color Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: Color Attribute TLV format
* Type: identify the Color Attribute, to be assigned by IANA.
* Length: 6, length of Flags + Color Value.
* Flags and Color is the same as defined in [RFC9012]. Color Value:
32 bit value of color.
3. Security Considerations
TBD
4. IANA Considerations
This document requires IANA to assign the following code points from
the registry called "BGP-LS Node Descriptor, Link Descriptor, Prefix
Descriptor, and Attribute TLVs":
+=======+==============================+===============+
| Value | Description | Reference |
+=======+==============================+===============+
| TBD1 | Metadata Path Attribute Type | Section 2.2.1 |
+-------+------------------------------+---------------+
| TBD2 | Site Preference Sub-Type | Section 2.2.1 |
+-------+------------------------------+---------------+
| TBD3 | Capacity Sub-Type | Section 2.2.1 |
+-------+------------------------------+---------------+
| TBD4 | Load Measurement Sub-Type1: | Section 2.2.1 |
| | Aggregated-Cost | |
+-------+------------------------------+---------------+
| TBD5 | Load Measurement Sub-Type2: | Section 2.2.1 |
| | Raw-Measurements | |
+-------+------------------------------+---------------+
| TBD6 | Color Attribute Type | Section 2.3.1 |
+-------+------------------------------+---------------+
Table 1
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5. Contributors
Xiangfeng Ding
email: dingxiangfeng@huawei.com
6. Normative References
[I-D.ietf-idr-5g-edge-service-metadata]
Dunbar, L., Majumdar, K., Wang, H., and G. S. Mishra, "BGP
Extension for 5G Edge Service Metadata", Work in Progress,
Internet-Draft, draft-ietf-idr-5g-edge-service-metadata-
00, 2 December 2022,
<https://datatracker.ietf.org/doc/html/draft-ietf-idr-5g-
edge-service-metadata-00>.
[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/rfc/rfc2119>.
[RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
S. Ray, "North-Bound Distribution of Link-State and
Traffic Engineering (TE) Information Using BGP", RFC 7752,
DOI 10.17487/RFC7752, March 2016,
<https://www.rfc-editor.org/rfc/rfc7752>.
[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/rfc/rfc8174>.
[RFC9012] Patel, K., Van de Velde, G., Sangli, S., and J. Scudder,
"The BGP Tunnel Encapsulation Attribute", RFC 9012,
DOI 10.17487/RFC9012, April 2021,
<https://www.rfc-editor.org/rfc/rfc9012>.
[RFC9085] Previdi, S., Talaulikar, K., Ed., Filsfils, C., Gredler,
H., and M. Chen, "Border Gateway Protocol - Link State
(BGP-LS) Extensions for Segment Routing", RFC 9085,
DOI 10.17487/RFC9085, August 2021,
<https://www.rfc-editor.org/rfc/rfc9085>.
[RFC9252] Dawra, G., Ed., Talaulikar, K., Ed., Raszuk, R., Decraene,
B., Zhuang, S., and J. Rabadan, "BGP Overlay Services
Based on Segment Routing over IPv6 (SRv6)", RFC 9252,
DOI 10.17487/RFC9252, July 2022,
<https://www.rfc-editor.org/rfc/rfc9252>.
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Acknowledgements
The authors would like to thank Haibo Wang, LiLi Wang, Jianwei Mao
for their help.
Authors' Addresses
Cheng Li (editor)
Huawei Technologies
Beijing
China
Email: c.l@huawei.com
Hang Shi (editor)
Huawei Technologies
Beijing
China
Email: shihang9@huawei.com
Tao He
China Unicom
Beijing
China
Email: het21@chinaunicom.cn
Ran Pang
China Unicom
Beijing
China
Email: pangran@chinaunicom.cn
Guofeng Qian
Huawei Technologies
Beijing
China
Email: qianguofeng@huawei.com
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