Internet DRAFT - draft-ding-idr-rtc-for-bgp-flow-sr
draft-ding-idr-rtc-for-bgp-flow-sr
IDR Working Group X. Ding
Internet-Draft Z. Tan
Intended status: Informational L. Wang
Expires: 12 September 2023 Huawei Technologies
11 March 2023
Route Target Constraint for BGP Flow Spec(BGP Flow) and BGP Segment
Routing Policies(BGP SR-Policy)
draft-ding-idr-rtc-for-bgp-flow-sr-00
Abstract
This document introduces an extension to the application scenarios of
Route Target Constraints (RTC). By using the global administrator
field of the IPv4 Address Specific Extended Community to represent a
network node and exchanging BGP Route-Target routes, a BGP speaker
could generate an egress policy for filtering one or a group of
network nodes, which could implement precise control and distribution
of services such as BGP Flow Spec and BGP Segment Routing Policies.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
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
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This Internet-Draft will expire on 12 September 2023.
Copyright Notice
Copyright (c) 2023 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
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Route Target Membership NLRI Advertisements . . . . . . . . . 3
3. Use case . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. BGP Flow Spec ORF . . . . . . . . . . . . . . . . . . . . 4
3.2. BGP Segment Routing Policies ORF . . . . . . . . . . . . 4
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . 6
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
6.1. Normative References . . . . . . . . . . . . . . . . . . 6
6.2. References . . . . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
BGP [RFC4271] has been used to distribute different types of routing
and policy information. In some scenarios, the distributed routing
information is specific for certain services, such as BGP/MPLS IP
VPNs.
Route Target Constraints (RTC) [RFC4684], extends Outbound Route
Filtering (ORF), describes how route targets are exchanged through
the BGP RTC address family on a BGP/MPLS IP VPN network to generate
egress policies. This feature enables the BGP/MPLS IP VPN network to
control the advertisement of VPN routing information in a more
refined manner.
This document introduces an extension to the application scenarios of
Route Target Constraints (RTC) [RFC4684] to control the distribution
of routing information to one or a group of network nodes, which
could implement precise control of services such as BGP Flow Spec
[RFC8955] and BGP Segment Routing Policies
[I-D.ietf-idr-segment-routing-te-policy].
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1.1. Terminology
This document introduces the following terms:
RTC Route Target Constraints [RFC 4684]
ORF Outbound Route Filtering
Flowspec BGP Flow Specification
SR-Policy BGP Segment Routing Policy
NLRI Network Layer Reachability Information
2. Route Target Membership NLRI Advertisements
The encapsulation of Route Target membership NLRI is defined in Route
Target Constraints (RTC) [RFC4684], the NLRI is advertised in BGP
UPDATE messages using the MP_REACH_NLRI and MP_UNREACH_NLRI
attributes. The (AFI, SAFI) value pair used to identify this NLRI is
(AFI=1, SAFI=132).
The route-target field in the NLRI indicates a network node and is
encoded as a IPv4 Address Specific Extended Community [RFC4360], as
shown blow:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| origin as |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x01 or 0x41 | Sub-Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Global Administrator |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Administrator |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Route Target membership NLRI Format
While encoding these fields:
* Global Administrator: 4 octets, indicates the router identifier of
the node. If the Global Administrator is set to 0.0.0.0, it means
that the peer node accepts all policy rules from the RR.
* Local Administrator: 2 octets, reserved for future use, MUST be
set to 0 upon the sender and MUST be ignored upon the receiver.
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3. Use case
This section describes a few use-case scenarios.
3.1. BGP Flow Spec ORF
+----------------------------------------------+
| +----------+ |
| |Controller| |
| +----------+ |
| | |
| | |
| +---------+ |
| | | |
| | RR | |
| | | |
| +---------+ |
| / \ |
| / \ |
| +---------+ +---------+ |
| | PE1 | | PE2 | |
| +---------+ +---------+ |
| Flow speaker 1 Flow speaker 2 |
| rt-id 1.1.1.1 rt-id 2.2.2.2 |
| AS 100 |
+----------------------------------------------+
Figure 2: BGP Flow Spec ORF
In the topology above, the Controller, PE1, and PE2 establish IBGP
peer relationships with the RR respectively. PE1 and PE2 are clients
of the RR. The Controller distributes Flowspec rules through the RR,
and the RR reflects the Flowspec rules to PE1 and PE2.
PE1 sends route target membership NLRI{100, 1.1.1.1:0} to the RR, and
PE2 sends route target membership NLRI{100, 2.2.2.2:0} to the RR.
After receiveing the UPDATE messages with Route Target Membership
NLRI, the RR will trigger the RIB-OUTS of the Flowspec route to match
the egress policies and update the route to PEs.
If hierarchical RRs are deployed, the RRs need to advertise all
received route target membership NLRI routes to the upper-layer RRs.
3.2. BGP Segment Routing Policies ORF
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+----------------------------------------------+
| +----------+ |
| |Controller| |
| +----------+ |
| | |
| | |
| +---------+ |
| | | |
| | RR | |
| | | |
| +---------+ |
| / \ |
| / \ |
| +---------+ +---------+ |
| | PE1 | | PE2 | |
| +---------+ +---------+ |
| Policy 1 Policy 2 |
| rt-id 1.1.1.1 rt-id 2.2.2.2 |
| AS 100 |
+----------------------------------------------+
Figure 3: BGP Segment Routing Policies ORF
It is described in BGP Segment Routing Policies
[I-D.ietf-idr-segment-routing-te-policy] that one or more route
targets SHOULD be attached to the advertisement, where each route
target identifies one or more intended headends for the advertised SR
Policy update. In the topology above, when the controller needs to
deliver SR policies to PE1 and PE2, it will advertises SR policies
with route target extended communities, SR Policy1 with {1.1.1.1:0}
and SR Policy2 with {2.2.2.2:0}, to RR. The RR will reflect SR
Policies to both PE1 and PE2. PEs need to do an ingress filtering,
by matching route target extended community with its own router-id.
In this case, PE1 will keep SR Policy1 and drop SR Policy2, as well
as PE2 will keep SR Policy2 and drop SR Policy1. During this
process, even though SR policies are correctly provisioned, the RR
advertises all routes to all peers, which may cause network
congestion.
The ORF operations described in this document work as an egress
filter on RR. PE1 sends route target membership NLRI{100, 1.1.1.1:0}
to the RR, and PE2 sends route target membership NLRI{100, 2.2.2.2:0}
to the RR. After receiving the Route Target Membership NLRI from the
PE, the RR generates a PE-specific egress filter. Before advertising
routes to PEs, the RR matches routes with egress policies, and will
only deliver SR policy1 to PE1 and SR policy1 to PE2 respectively.
In this way, services could be correctly deployed and network
bandwidth could be saved.
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4. IANA Considerations
TBD
5. Security Considerations
TBD
6. References
6.1. 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>.
[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>.
[RFC4684] Marques, P., Bonica, R., Fang, L., Martini, L., Raszuk,
R., Patel, K., and J. Guichard, "Constrained Route
Distribution for Border Gateway Protocol/MultiProtocol
Label Switching (BGP/MPLS) Internet Protocol (IP) Virtual
Private Networks (VPNs)", RFC 4684, DOI 10.17487/RFC4684,
November 2006, <https://www.rfc-editor.org/info/rfc4684>.
6.2. References
[I-D.ietf-idr-segment-routing-te-policy]
Previdi, S., Filsfils, C., Talaulikar, K., Mattes, P.,
Jain, D., and S. Lin, "Advertising Segment Routing
Policies in BGP", Work in Progress, Internet-Draft, draft-
ietf-idr-segment-routing-te-policy-20, 27 July 2022,
<https://datatracker.ietf.org/doc/html/draft-ietf-idr-
segment-routing-te-policy-20>.
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271,
DOI 10.17487/RFC4271, January 2006,
<https://www.rfc-editor.org/info/rfc4271>.
[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>.
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Authors' Addresses
Xiangfeng Ding
Huawei Technologies
No. 156 Beiqing Road
Beijing
100095
P.R. China
Email: dingxiangfeng@huawei.com
Zhen Tan
Huawei Technologies
No. 156 Beiqing Road
Beijing
100095
P.R. China
Email: tanzhen6@huawei.com
Lili Wang
Huawei Technologies
No. 156 Beiqing Road
Beijing
100095
P.R. China
Email: lily.wong@huawei.com
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