Internet DRAFT - draft-liu-cats-bgp-epe-applicability
draft-liu-cats-bgp-epe-applicability
IDR X. Liu
Internet-Draft China Mobile
Intended status: Informational 10 July 2023
Expires: 11 January 2024
Using BGP EPE Control Plane for CATS
draft-liu-cats-bgp-epe-applicability-00
Abstract
This document describes an approach for using the BGP EPE Control
Plane [RFC8670] for CATS cross as domain steering traffic based on a
normalized metric that reflect the underlying network conditions and
other service-specific metrics collected from available service
locations.
Status of This Memo
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This Internet-Draft will expire on 11 January 2024.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Definition of Terms . . . . . . . . . . . . . . . . . . . . . 2
3. CATS information to be Distributed by BGP . . . . . . . . . . 3
4. BGP EPE for CATS . . . . . . . . . . . . . . . . . . . . . . 4
4.1. Metric collected and distributed . . . . . . . . . . . . 4
4.2. BGP Extension for CATS . . . . . . . . . . . . . . . . . 5
4.3. Implemention for BGP EPE CATS . . . . . . . . . . . . . . 5
5. Minimum Interval for Metrics Change Advertisement . . . . . . 6
6. Manageability Considerations . . . . . . . . . . . . . . . . 6
7. Security Considerations . . . . . . . . . . . . . . . . . . . 6
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
10.1. Normative References . . . . . . . . . . . . . . . . . . 6
10.2. Informative References . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
BGP (Border Gateway Protocol) is a dynamic routing protocol between
autonomous system AS (Autonomous System). The BGP EPE function is an
extension of BGP to Segment Routing to implement source routing
between AS.
Enabling BGP EPE?egress peer engineering [RFC8670], BGP Peer SID can
be assigned to inter-domain paths and Peer SID can be passed to the
network controller via BGP-LS extension. Through the rational
arrangement of IGP SID and BGP Peer SID, the controller can realize
the optimal path forwarding across the domain.
In addition to the Peer Node and Peer Adjacency, there is also the
Peer Set. Peer Set That is, a group of neighbors as a Set, and then
assign SID based on the group. This SID can also correspond to
multiple outgoing interfaces.
CATS is about finding an optimal service path for arrange a service
request, and thus about selecting one of the available service
instances that better optimize a set of metrics . The document
focuses on multiple AS domains traffic engineering .
2. Definition of Terms
This document makes use of the following terms:
Computing-Aware Traffic Steering (CATS): Aiming at computing and
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network resource optimization by steering traffic to appropriate
computing resources considering not only routing metric but also
computing resource metric.
Service: A monolithic functionality that is provided by an endpoint
according to the specification for said service. A composite
service can be built by orchestrating monolithic services.
Service instance: Running environment (e.g., a node) that makes the
functionality of a service available. One service can have several
instances running at different network locations.
Service identifier: Used to uniquely identify a service, at the same
time identifying the whole set of service instances that each
represents the same service behavior, no matter where those service
instances are running.
Service transaction: Has one or more service request that has
several flows which require the affinity because of the transaction
related state.
Computing Capacity: The ability of nodes with computing resource
achieve specific result output through data processing, including
but not limited to computing, communication, memory and storage
capacity.
3. CATS information to be Distributed by BGP
The goal of the proposed BGP extension is to distribute the metrics
collected by C-SMAs (CATS Service Metric Agents) to the CATS SDN
controller(centrial framwork) or ingress routers(distribued framwork)
to be used by the corresponding CATS Path Selectors . In this
document, We mainly propose a multi-domain centralized computing
force routing implementation scheme, combined with BGP EPE technology
to realize cats multi-domain traffic scheduling.
The detailed metrics collected by a C-SMA will be decided by the CATS
WG . And the encoding of the CATS metrics that will be selected by
the WG will be discussed in IDR WG . When a CATS ingress router
receives metrics updates for a Service ID from multiple CATS egress
routers, all those egress routers are considered as the next hops for
that Service ID . The Service ID is represented as an IPv4/IPv6
unicast address, which is assigned to a group of interfaces to which
the service instances are attached .
The CATS ingress router's BGP engine will send this metric to SDN
controller by BGP-LS protocol. According to the collected computing
power resource information and network information, the SDN
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controller generates an end-to-end segmentID list through the
computing path algorithm, which is sent to cats ingress through BGP
SR policy.
4. BGP EPE for CATS
4.1. Metric collected and distributed
As shown in Figure 1, computing service node 1 and node 2 are cloud
resource pools, which can provide computing power resource services.
The main functions of the computing power agent(C-SMA) module are as
follows:
Use restful protocol to collect the computing information of
computing service nodes. The computing information includes CPU
utilization, memory utilization, GPU utilization, storage capacity,
DPU utilization, energy efficiency of computing power nodes, etc.
The computing power agent module normalized the collected computing
information(metric) by PageRank algorithm to generate the
comprehensive computing power index metric. The larger the metric,
the more preferred.
Computing power information notification, as shown in Figure R11,
R12, as the exit router of computing power agent module, needs to
have BGP routing protocol capability. R9, R11, R 11 and R12 should
establish BGP neighbors respectively. The BGP update message passes
the above normalized metric value to R9 and R10.
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+---------+
| R12 |
+---------------+ +-----------------+ +------------+ | |
| SDN | | R8 | | | | C-SMA|
| | | | | | +---------+
| R2 | | | | R10 |
| | | R4 R6 | | |
| | | AS3 | | |
| R1 | +-----------------+ | |
| | | |
| | +----------------+ | |
| R3 | | | | |
| | | | | |
| | | R5 R7 | | R9 |
| | | | | | +----------+
| AS1 | | AS2 | | AS4 | | R11 |
+---------------+ +----------------+ +------------+ | |
| C-SMA|
+----------+
|
Figure 1: Modeling of BGP EPE For CSTS
4.2. BGP Extension for CATS
As shown in FIG. 1, the router R9 and R10 of AS4 receive the
computing information(metric) distributed by the R9 to its? all
peers.(the process flow of R9 is same R10, we use R9 for example in
following).The R9 as the export router of AS4 domain would to be
assigned a BGP prefix SID [RFC8669], while enabling BGP LU address
family(BGP label unicast address family). routers establishing IBGP
peers within inter-domain, and intra-domain establishing EBGP peers .
By extending the BGP update message that add a new BGP attribute
indicates the metric of the computing resource pool hanging under the
egress router. R1 can receive the BGP prefix-SID of R9 through the
message interaction between bgp peers. Finally, the metric will be
sent to SDN controller.
4.3. Implemention for BGP EPE CATS
Enabling BGP EPE[RFC7855] function on egress routers of each As
domain. After the device starts the EPE function, BGP peer SID will
be automatically assigned, and the SDN controller in the domain will
collect Peer SID, all BGP routes,the network information, the
topology information, the information from the EPE function in the
domain, and the metric which distributed by C-SMA of CATS.
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According to the business needs, the controller determines the last
jump of the egress equipment of the computing resource pool that
meets the computing requirements to generate SID-LIST. The
controller sends the SID-LIST to the forwarding entry device(ingress
device, R1 in Fig.1) through the border gateway protocol or the PCEP
protocol. Finally, in the cross-domain scenario, the appropriate
service center can be determined according to the computing
information(metirc), and at the same time, the traditional BGP based
on the shortest path selection, realizing the cross-domain computing
network traffic engineering.
5. Minimum Interval for Metrics Change Advertisement
As the metrics change can triger bgp provider send update message to
peer, the bgp route table may changed, and impact the path selection.
The route update interval was fifteen seconds for the IBGP peer, and
thirty seconds for the EBGP peer. The Minimum Interval for Metrics
Change Advertisement is configured to control the bgp message update
frequency to avoid bgp route oscillations . The minmun interval is
set equal or greater than bgp route fresh interval in best .
6. Manageability Considerations
The Edge Service Metadata described in this document are only
intended for propagating between Ingress and egress routers of one
single BGP domain . Only the selective services by clients are
considered as CATS Services, which are managed by one operator, even
though the routers can be by different vendors.
7. Security Considerations
BGP EPE CATS needs to follow the spring architecture[RFC7855], and be
consistent with the spring architecture?s security considerations.
8. IANA Considerations
In the current IANA definition, the number 41 to 127 are unused. The
type value (Type Code) of the computing-aware routing attribute is
defined as optional transitive, and the normalized metric attribute
type value is temporarily set to 127.
9. Acknowledgements
TBD.
10. References
10.1. Normative References
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[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>.
[RFC8670] Filsfils, C., Ed., Previdi, S., Dawra, G., Aries, E., and
P. Lapukhov, "BGP Prefix Segment in Large-Scale Data
Centers", RFC 8670, DOI 10.17487/RFC8670, December 2019,
<https://www.rfc-editor.org/info/rfc8670>.
[RFC8669] Previdi, S., Filsfils, C., Lindem, A., Ed., Sreekantiah,
A., and H. Gredler, "Segment Routing Prefix Segment
Identifier Extensions for BGP", RFC 8669,
DOI 10.17487/RFC8669, December 2019,
<https://www.rfc-editor.org/info/rfc8669>.
[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/info/rfc9085>.
[RFC9086] Previdi, S., Talaulikar, K., Ed., Filsfils, C., Patel, K.,
Ray, S., and J. Dong, "Border Gateway Protocol - Link
State (BGP-LS) Extensions for Segment Routing BGP Egress
Peer Engineering", RFC 9086, DOI 10.17487/RFC9086, August
2021, <https://www.rfc-editor.org/info/rfc9086>.
[RFC9087] Filsfils, C., Ed., Previdi, S., Dawra, G., Ed., Aries, E.,
and D. Afanasiev, "Segment Routing Centralized BGP Egress
Peer Engineering", RFC 9087, DOI 10.17487/RFC9087, August
2021, <https://www.rfc-editor.org/info/rfc9087>.
10.2. Informative References
[RFC7855] Previdi, S., Ed., Filsfils, C., Ed., Decraene, B.,
Litkowski, S., Horneffer, M., and R. Shakir, "Source
Packet Routing in Networking (SPRING) Problem Statement
and Requirements", RFC 7855, DOI 10.17487/RFC7855, May
2016, <https://www.rfc-editor.org/info/rfc7855>.
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[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-02, 22 June 2023,
<https://datatracker.ietf.org/doc/html/draft-yao-cats-ps-
usecases-02>.
Author's Address
Xingsheng Liu
China Mobile
No.32 XuanWuMen West Street
Beijing
100053
China
Email: liuxing0315@sohu.com
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