Internet-Draft BGP FlowSpec Path Scheduling October 2023
Zhang, et al. Expires 25 April 2024 [Page]
Workgroup:
IDR
Internet-Draft:
draft-zzd-idr-flowspec-path-scheduling-00
Published:
Intended Status:
Standards Track
Expires:
Authors:
L. Zhang, Ed.
Huawei
T. Zhou
Huawei
J. Dong
Huawei

BGP Flow Specification Extensions for Path Scheduling

Abstract

Path scheduling is required in many network scenarios. For example, some links or nodes will be shut down in the tidal network when the traffic decreases, which may lead to the expiration of some routing paths.

This document defines a new type of component for BGP Flow Specification to identify the packets arrived at different time slot. Based on that, the headend can steer packets into different paths at different time.

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 working documents as Internet-Drafts. The list of current Internet-Drafts is at https://datatracker.ietf.org/drafts/current/.

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 25 April 2024.

Table of Contents

1. Introduction

[RFC8955] and [RFC8956] define the BGP [RFC4271] Flow Specification (FlowSpec) that allows conveying flow specifications and traffic Action/Rules associated. BGP Flow specifications are encoded within the MP_REACH_NLRI and MP_UNREACH_NLRI attributes [RFC4760]. Rules (Actions associated) are encoded in Extended Community attribute [RFC4360]. The BGP Flow Specification function allows BGP Flow Specification routes that carry traffic policies to be transmitted to BGP Flow Specification peers to steer traffic.

[I-D.ietf-idr-ts-flowspec-srv6-policy] describes BGP flow specification usage that are used to steer data flow into an SR Policy which can steer traffic into a specific path.

The existing traffic filter rules and actions in FlowSpec are always effective and will steer specific traffic into one Policy once been delivered to the headend. However, there are many scenarios that need to schedule routing paths in the network.

[I-D.zzd-tvr-use-case-tidal-network] introduces the tidal network, in which the topology of the network will change periodically over time. The topology change may cause some of the paths invalid, and lead to path reselection or even recalculation. However, the reselection or recalculation takes a period of time, which will affect packet forwarding and cause problems such as packet disorder and packet loss. On a network with predictable topology changes, the controller knows future topology changes, it can deliver several policies for different topology to the headend in advance. Then the headend steers traffic to different policies based on time to prevent packet forwarding from being affected by topology changes.

This document defines a new type of component for BGP Flow Specification to identify the packets arrived at different time slot. Based on that, the headend can steer packets into different paths at different time.

1.1. 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. Motivation

[I-D.zzd-tvr-use-case-tidal-network] introduces the time variant routing scenario in the tidal network, in which the traffic volume varies greatly at different time. In order to reduce the power consumption, some of the links and nodes may be shut down when the traffic is at a low level.

In this scenario, the SR policy originator can generate several policies for different topologies. The headend doesn’t need to wait for the advertisement of topology change and just steer traffic in to different policies based on the flowSpec with scheduling time information, the affection of topology change is minimized.

3. Scheduling time information in FlowSpec

[RFC8955] defines 12 Components to identify different traffics. Based on [RFC8955], this document defines a new Component to identify the arrival time of packets, so as to enable Policies scheduling.

Encoding: <type (1 octet), length (1 octet), scheduling time information (variabile)]+>

Defines the time information that matches the arrival time of packets. This component matches if either the arrival time of an IP packet in the scope of scheduling time information.

The Scheduling time information has two formats according to the change regularity of network topology. They are Aperiodic Scheduling Time Information (ASTI) and Periodic Scheduling Time Information (PSTI).

3.1. Aperiodic Scheduling Time Information

The ASTI indicates one or more group of matching time slot (each includes the enable time and disable time) for the packets. The format of ASTI is shown as follows:

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      |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                          Enable Time                          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                         Disable Time                          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                                                               |
/                          Variable                             /
|                                                               |
Figure 1: Format of ASTI

Type: used to identify the type of scheduling time information. The value and corresponding types are shown as follows:

Table 1
Value Type
0x01 Aperiodic Scheduling Time Information
0x02 Periodic Scheduling Time Information

Enable Time: the time in seconds indicates the start time when the packets matching.

Disable Time: the time in seconds indicates the end time when the packets matching.

Variable: one or more groups of time information (A information group is composed of Enable Time and Disable time) may be included in one ASTI.

3.2. Periodic Scheduling Time Information

The PSTI indicates one or more group of periodic matching time slot (each includes period, enable time and disable time) for the packets. The format of PSTI is shown as follows:

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      |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                            Period                             |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                          Enable Time                          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                         Disable Time                          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                                                               |
/                          Variable                             /
|                                                               |
Figure 2: Format of PSTI

Type: as defined in clause “Aperiodic Scheduling Time Information”

Length: the size of the value field in octets.

Period: the time in seconds between the enable time of one repetition and the enable time of the next repetition.

Enable Time: the time in seconds indicates when the path(s) is(are) enabled.

Disable Time: the time in seconds indicates when the path(s) is(are) disabled

Variable: one or more groups of time information(A information group is composed of Period, Enable Time and Disable time) may be included in one PSTI.

4. Procedures

When the headend device (as a FlowSpec client) receives a instruction with scheduling time information from a BGP FlowSpec Controller, it will steer the traffic packets matching the time slot and other conditions in the Flowspec instruction into a specific Policy.

And the packets will be encapsulated with an SR List <S1, S2, S3> in the headend device, then send the packets to the TailEnd device along the path indicated by the SR list.

5. Security Considerations

These extensions to BGP FlowSpec do not add any new security issues to the existing protocol.

6. IANA Considerations

This document defines a new Component in the registry " Flow Spec Component Types" to be assigned by IANA:

Table 2
Value Description Reference
TBD1 Scheduling Time Information This document

7. References

7.1. Normative References

[RFC8955]
Loibl, C., Hares, S., Raszuk, R., McPherson, D., and M. Bacher, "Dissemination of Flow Specification Rules", RFC 8955, DOI 10.17487/RFC8955, , <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, , <https://www.rfc-editor.org/info/rfc8956>.
[RFC4760]
Bates, T., Chandra, R., Katz, D., and Y. Rekhter, "Multiprotocol Extensions for BGP-4", RFC 4760, DOI 10.17487/RFC4760, , <https://www.rfc-editor.org/info/rfc4760>.
[I-D.ietf-idr-ts-flowspec-srv6-policy]
Wenying, J., Liu, Y., Zhuang, S., Mishra, G. S., and S. Chen, "Traffic Steering using BGP FlowSpec with SR Policy", Work in Progress, Internet-Draft, draft-ietf-idr-ts-flowspec-srv6-policy-03, , <https://datatracker.ietf.org/doc/html/draft-ietf-idr-ts-flowspec-srv6-policy-03>.
[RFC2119]
Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <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, , <https://www.rfc-editor.org/info/rfc8174>.

7.2. Informative References

[RFC4271]
Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A Border Gateway Protocol 4 (BGP-4)", RFC 4271, DOI 10.17487/RFC4271, , <https://www.rfc-editor.org/info/rfc4271>.
[RFC4360]
Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended Communities Attribute", RFC 4360, DOI 10.17487/RFC4360, , <https://www.rfc-editor.org/info/rfc4360>.
[I-D.zzd-tvr-use-case-tidal-network]
Zhang, L., Zhou, T., Dong, J., and N. Nzima, "Use Case of Tidal Network", Work in Progress, Internet-Draft, draft-zzd-tvr-use-case-tidal-network-02, , <https://datatracker.ietf.org/doc/html/draft-zzd-tvr-use-case-tidal-network-02>.

Authors' Addresses

Li Zhang (editor)
Huawei
Beiqing Road
Beijing
China
Tianran Zhou
Huawei
Jie Dong
Huawei