BGP Flowspec for Computing-Aware Traffic Steering
draft-lin-idr-cats-flowspec-ts-02
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| Last updated | 2025-03-16 (Latest revision 2024-11-08) | ||
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draft-lin-idr-cats-flowspec-ts-02
IDR C. Lin
Internet Draft New H3C Technologies
Intended status: Standards Track H. Yao
Expires: September 15, 2025 China Mobile
Z. Li
China Mobile
March 15, 2025
BGP Flowspec for Computing-Aware Traffic Steering
draft-lin-idr-cats-flowspec-ts-02
Abstract
Computing-Aware Traffic Steering (CATS) is a traffic engineering
approach that optimizes traffic steering to a given service instance
by taking into account the dynamic nature of both computing and
network resources. This document extends Version 2 of the BGP Flow
Specification (BGP-FS) to enable flow classification and path
selection for CATS flow categories, thus supporting the deployment
of CATS traffic optimization.
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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Internet-Drafts are draft documents valid for a maximum of six
months 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 15 September 2025.
Copyright Notice
Copyright (c) 2025 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
(http://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
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document must include Simplified BSD License text as described in
Section 4.e of the Trust Legal Provisions and are provided without
warranty as described in the Simplified BSD License.
Table of Contents
1. Introduction...................................................2
2. Requirements Language..........................................3
3. Terminology....................................................3
4. Flow Specifications for CATS ..................................4
4.1. Scenario 1................................................4
4.2. Scenario 2................................................5
4.3. Scenario 3................................................6
5. Extension of BGP-FS............................................7
5.1. MARK CS-ID Action ........................................7
5.2. Redirect to CSCI-ID Action................................9
6. IANA Considerations...........................................10
6.1. FSv2 IP Basic TLV Components.............................10
6.2. CATS Action..............................................10
7. Security Considerations.......................................11
8. References....................................................11
8.1. Normative References.....................................11
Authors' Addresses...............................................13
1. Introduction
A Flow Specification (Flow Spec) is an n-tuple consisting of several
matching criteria that can be applied to IP traffic [RFC8955]. The
Flow Spec conveys match conditions (each may include several
components) which are encoded using MP_REACH_NLRI and
MP_UNREACH_NLRI attributes [RFC4760], while the associated actions
such as redirect and traffic marking are encoded in BGP Extended
Communities [RFC4360][RFC5701]. The IPv4 NLRI component types and
traffic filtering actions sub-types are described in [RFC8955],
while the IPv6 related are described in [RFC8956].
[I-D.ietf-idr-flowspec-l2vpn] extends the flow-spec rules and
actions for Ethernet Layer 2 and L2VPN. [I-D.ietf-idr-flowspec-v2]
specifies BGP Flow Specification Version 2.
Computing-Aware Traffic Steering (CATS) is introduced in [draft-
ietf-cats-framework].In CATS network, the C-PS component performs
path selection based on the CS-ID and forwards service traffic
according to the selected path.
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This document specifies a new BGP Flow Spec Component Type to
support CATS traffic filtering. Traffic is classified and mapped to
the corresponding CS-ID using BGP Flow Spec rules, and path
selection is then performed based on the CS-ID. BGP Flow Spec
implements functions similar to the C-TC component.
On the other hand, BGP Flow Spec can also use CS-ID as a filtering
criterion. For the matched traffic, it forwards based on the actions
specified by BGP Flow Spec, replacing the path selection function of
C-PS. It also specifies traffic filtering actions to enable the
creation of the CS-ID in the outer tunnel encapsulation when matched
to the corresponding Flow Spec rules.
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 RFC 2119 [RFC2119] RFC 8174 [RFC8174] when, and only when,
they appear in all capitals, as shown here.
3. Terminology
This document makes use of the following terms:
Flow Spec: Flow Specification
BGP-FS: Border Gateway Protocol (BGP) Flow Specification (FS)
This document uses the following terms defined in
[I-D.ietf-cats-framework]:
* CATS
* CS-ID
* CSCI-ID
* Client
* Ingress CATS-Forwarder
* Egress CATS-Forwarder
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* C-PS
* C-SMA
* C-TC
4. Flow Specifications for CATS
The Flow Spec for CATS is shown in Figure 1, that is, the Controller
is used to set up BGP connection with the policy enforcement points
in CATS network.
+------------------+
/------| Controller |-----\ CS-ID 1
/ +------------------+ \ CSCI-ID 1
+------+ FS / | \ FS +------+
|Client|-\ / FS FS FS \ /-|Server|
+------+ \ +-/------+ +--/------|------\-----+ +--\-----+ / +------+
\-|Ingress | | | |Egress |-/
|CATS-FWD|--| CATS Network |--|CATS-FWD| CS-ID 1
/-| | | | | |-\ CSCI-ID 2
+------+ / +--------+ +----------------------+ +--------+ \ +------+
|Client|-/ \-|Server|
+------+ +------+
Figure 1. Flow Spec for CATS
The centralized model can be considered for the deployment of the
CATS framework as described in [draft-ietf-cats-framework]. This
document implements the functionalities of C-TC and C-PS under the
centralized model by extending BGP-FS.
4.1. Scenario 1
Flow entries are directly pushed to redirect traffic to the CSCI-ID
based on flow characteristics, enabling subsequent forwarding.
Rule 1
Filter: Flow characteristics
Action: Redirect to IPv4/IPv6 CSCI-ID
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+------------+
| BGP FS |
| Controller |
+------------+
| FlowSpec route to Ingress NLRI:
| Rule Condition: IP Extended Filter(Match Port, etc)
| Action : Redirect to IPv4/IPv6 CSCI-ID
|
| .-----.
| ( ) +------+
V .--( )--. -|Server|
+-------+ ( ) +-------+ / +------+
| |_( CATS Network )_| |-
|Ingress| ( ================> ) |Egress |-
+-------+ ( ) +-------+ \ +------+
'--( )--' -|Server|
( ) +------+
'-----'
Figure 2: Scenario 1 Examples
4.2. Scenario 2
The data layer of the traffic includes a CS-ID field. Rules are pushed
to filter based on the CS-ID, redirecting traffic to the CSCI-ID for forwarding.
Rule 1
Filter: IPv4/IPv6 CS-ID
Action: Redirect to IPv4/IPv6 CSCI-ID
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+------------+
| BGP FS |
| Controller |
+------------+
| FlowSpec route to Ingress NLRI:
| Rule Condition: IP Extended Filter(IPv4/IPv6 CS-ID)
| Action : Redirect to IPv4/IPv6 CSCI-ID
|
| .-----.
| ( ) +------+
V .--( )--. -|Server|
+-------+ ( ) +-------+ / +------+
| |_( CATS Network )_| |-
|Ingress| ( ================> ) |Egress |-
+-------+ ( ) +-------+ \ +------+
'--( )--' -|Server|
( ) +------+
'-----'
Figure 3: Scenario 2 Examples
4.3. Scenario 3
Flow characteristics mapped to the CS-ID; deploy rules to filter
based on the CS-ID and redirect traffic to the CSCI-ID for
forwarding..
Rule 1
Filter: Flow characteristics
Action: Mark IPv4/IPv6 CS-ID
Rule 2
Filter: IPv4/IPv6 CS-ID
Action: Redirect to IPv4/IPv6 CSCI-ID
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+------------+
| BGP FS |
| Controller |
+------------+
| FlowSpec route to Ingress NLRI:
| Rule Condition: IP Extended Filter(Match Port, etc)
| Action 1: Mark IPv4/IPv6 CS-ID
| Action 2: Redirect to IPv4/IPv6 CSCI-ID
|
| .-----.
| ( ) +------+
V .--( )--. -|Server|
+-------+ ( ) +-------+ / +------+
| |_( CATS Network )_| |-
|Ingress| ( ================> ) |Egress |-
+-------+ ( ) +-------+ \ +------+
'--( )--' -|Server|
( ) +------+
'-----'
Figure 4: Scenario 3 Examples
5. Extension of BGP-FS
5.1. MARK CS-ID Action
When implementing the C-TC function, the corresponding CS-ID is
assigned based on traffic characteristics, which are specified
according to the FSv2 Basic IP Filters.
If a rule is matched, execute the Mark CS-ID action.
[draft-ietf-idr-fsv2-ip-basic] defines "FSv2 Extended Community
Actions." Based on this, this document introduces a new action:
"Mark CS-ID."
"Mark IPv4 CS-ID" Action SubTLV has the format:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Action type(TBD1) | Length(4) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 CS-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: "Mark IPv4 CS-ID" Action SubTLV
"Mark IPv6 CS-ID" Action SubTLV has the format:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Action type(TBD2) | Length(16) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| IPv6 CS-ID |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: "Mark IPv6 CS-ID" Action SubTLV
5.2. Filter by CS-ID
[draft-ietf-idr-fsv2-ip-basic] defines the Components in the IP
Basic TLV. This document proposes a new Component for defining CS-ID
information from "FSv2 Components for IP Basic TLVs".
When filtering using FlowSpec rules, the condition can be specified
as the CS-ID.
This is primarily used to achieve the C-PS function of CATS based on
CS-ID for path selection.
Sub-TLV Definition
-------- ---------------------
TBD3 - IPv4 CS-ID
TBD4 - IPv6 CS-ID
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The IPv4 CS-ID Components has following format:
Filter defines: a list of match criteria for IPv4 CS-ID
Type: TBD3
length: variable
IPv4 value: [numeric_op, value]+
Each CS-ID is 4 bytes.
The IPv6 CS-ID Components has following format:
Filter defines: a list of match criteria for IPv6 CS-ID
Type: TBD4
length: variable
IPv6 value: [numeric_op, value]+
Each CS-ID is 16 bytes.
5.2. Redirect to CSCI-ID Action
While specifying the path, C-PS designates the CSCI-ID information.
"Redirect to IPv4 CSCI-ID" Action SubTLV has the format:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Action type(TBD5) | Length(4) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CSCI-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: "Redirect to IPv4 CSCI-ID" Action SubTLV
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"Redirect to IPv6 CSCI-ID" Action SubTLV has the format:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Action type(TBD6) | Length(4) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| IPv6 CSCI-ID |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: "Redirect to IPv6 CSCI-ID" Action SubTLV
6. IANA Considerations
6.1. FSv2 IP Basic TLV Components
[draft-ietf-idr-fsv2-ip-basic] defines the Components in the IP
Basic TLV.
This document requested to assign a new type code point from "FSv2
IP Basic TLV Components" registry for CS-ID.
Sub-TLV Definition
-------- ---------------------
TBD1 - IPv4 CS-ID This document
TBD2 - IPv6 CS-ID This document
6.2. CATS Action
New action Types are requested from "FSv2 Community Path Attribute
Actions":
TBD3: MARK IPv4 CS-ID Action
TBD4: MARK IPv6 CS-ID Action
TBD5: Redirect to CSCI-ID Action
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TBD6: Redirect to CSCI-ID Action
7. Security Considerations
TBD
8. References
8.1. Normative References
[RFC4360] Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended
Communities Attribute", RFC 4360, DOI
10.17487/RFC4360, February 2006, <https://www.rfc-
editor.org/info/rfc4360>.
[RFC4760] Bates, T., Chandra, R., Katz, D., and Y.
Rekhter, "Multiprotocol Extensions for BGP-4", RFC
4760, DOI 10.17487/RFC4760, January
2007, <https://www.rfc-editor.org/info/rfc4760>.
[RFC5701] Rekhter, Y., "IPv6 Address Specific BGP Extended Community
Attribute", RFC 5701, DOI 10.17487/RFC5701, November
2009, <https://www.rfc-editor.org/info/rfc5701>.
[RFC8955] Loibl, C., Hares, S., Raszuk, R., McPherson, D., and M.
Bacher, "Dissemination of Flow Specification Rules", RFC
8955, DOI 10.17487/RFC8955, December
2020, <https://www.rfc-editor.org/info/rfc8955>.
[RFC8956] Loibl, C., Ed., Raszuk, R., Ed., and S. Hares,
Ed., "Dissemination of Flow Specification Rules for
IPv6", RFC 8956, DOI 10.17487/RFC8956, December
2020, <https://www.rfc-editor.org/info/rfc8956>.
[I-D.ietf-idr-flowspec-l2vpn] Weiguo, H., Eastlake, D.
E., Litkowski, S., and S. Zhuang, "BGP Dissemination of L2
Flow Specification Rules", Work in Progress, Internet-
Draft, draft-ietf-idr-flowspec-l2vpn-23, 15 April
2024, <https://datatracker.ietf.org/doc/html/draft-ietf-
idr-flowspec-l2vpn-23>.
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[I-D.ietf-idr-flowspec-v2]Hares, S., Eastlake, D. E., Yadlapalli,
C., and S. Maduschke, "BGP Flow Specification Version 2",
Work in Progress, Internet-Draft, draft-ietf-idr-flowspec-
v2-04, 28 April 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-idr-
flowspec-v2-04>.
[I-D.ietf-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-ietf-cats-framework-05, 10 February 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-cats-
framework-05>.
[I-D.ietf-cats-usecases-requirements]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-ietf-cats-usecases-requirements-01,
23 October
2023,<https://datatracker.ietf.org/doc/html/draft-ietf-
cats-usecases-requirements-01>.
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Authors' Addresses
Changwang Lin
New H3C Technologies
China
Email: linchangwang.04414@h3c.com
Huijuan Yao
China Mobile
No.32 XuanWuMen West Street
Beijing
100053
China
Email: yaohuijuan@chinamobile.com
Zhenqiang Li
China Mobile
China
Email: lizhenqiang@chinamobile.com
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