BGP FlowSpec Extension for Traffic Scheduling

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Table of Contents

1. Introduction

[RFC8955] and [RFC8956] have defined commonly used traffic filtering conditions and actions for IPv4 and IPv6. The traffic filtering conditions are used as NLRI and the traffic filtering actions are used as Extended Community in BGP FlowSpec routing. [I-D.ietf-idr-flowspec-v2] defines BGP Flow Specification Version 2. More refined traffic management can be achieved by traffic scheduling that matches the rules through the traffic filtering conditions and the corresponding actions carried in BGP FlowSpec routes.¶

This document defines two new extended community for traffic filtering actions of BGP flowspec, which respectively represent the minimum rate guarantee and congestion management for the flow, in order to better realize traffic scheduling through BGP FlowSpec routes.¶

2. Extended Community Flow Specification Actions

This document defines two new extended community: minimum bandwidth guarantee and congestion management.¶

    Type Vlue     Action                       Encoding
    ---------------------------------------------------------------
    TBD1    CBR (Minimum rate guarantee)   2-octet AS, 4-octet Rate

    TBD2    CM (Congestion Management)     1-octet Queue value

The specific encoding for the first new extended community is shown as follows:¶

     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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |           TBD1                |           ASN                 |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                          Rate                                 |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Where,¶

Type: 2 bytes, representing the minimum rate guarantee attribute, to be allocated by IANA.¶

ASN: 2 bytes, representing the AS number.¶

Rate: 4 bytes, representing the minimum guaranteed rate, expressed in IEEE floating point format, units being bytes per second. The router sets the traffic flow as fast forwarding based on this attribute, ensuring that the CBR is the Rate value.¶

The specific encoding for the second new extended community defined in this document is shown as follows:¶

     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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |           TBD2                |           Queue               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Where,¶

Type: 2 bytes, representing congestion management attribute, to be allocated by IANA.¶

Queue: 2 byte, indicating the type used for queue scheduling. The lower three bits have values from 0 to 7, representing queues BE, AF1, AF2, AF3, AF4, EF, CS6, and CS7, corresponding to the commonly used 8 queues currently, and the other bits are reserved. After the router is configured with congestion management mechanism (which may be queue technologies such as FIFO, PQ, CQ, RTPQ, WFQ, CBQ, CBR, etc., not discussed in this document), traffic of different queue types will be forwarded according to the corresponding queue scheduling technology.¶

3. Use Cases

This section describes how to use the defined new extended community in real scenarios.¶

Example 1:¶

The traffic with a destination address of 2.2.2.0/24 and DSCP of 3 requires a guaranteed minimum rate of 30 Mb/s. The BGP FlowSpec controller advertises a BGP route to the Ingress Router, carrying the following information.¶

Flow Specification NLRI encoding:¶

    Length     Destination            DSCP
    ---------------------------------------------------------
    0x08       01 18 02 02 02         0B 81 0C

Extended Community:¶

    Type         ASN                Rate
    ---------------------------------------------------------
    TBD1         00 00              01 c9 c3 80

Parsing the NLRI encoding of the above route as the traffic filtering condition: destination address is 2.2.2.0/24 and DSCP is 3. Traffic that matches this condition will perform the action carried in the Extended Community: minimum traffic rate guarantee of 30M, so as to achieve traffic scheduling.¶

Example 2:¶

The traffic with a destination address of 192.0.2.0/24 and DSCP of 3 is set to AF2 queue. The router forwards the message according to its configured queue scheduling method. The BGP FlowSpec controller advertises a BGP route to the Ingress Router, carrying the following information.¶

Flow Specification NLRI encoding:¶

    Length     Destination            DSCP
    ---------------------------------------------------------
    0x08       01 18 c0 00 02         0B 81 0C

Extended Community:¶

    Type          Queue
    ----------------------------
    TBD1          00 02

Parsing the NLRI encoding of the above route as the traffic filtering condition: destination address is 192.2.2.0/24 and DSCP is 3. Traffic that matches this condition will perform the action carried in the Extended Community: traffic queue is AF2, so as to achieve traffic scheduling.¶

4. IANA Considerations

For the purpose of this work, the following two Extended Communities require IANA assignments.¶

TBD1 for CBR (Minimum rate guarantee, bytes).¶

TBD2 for CM (Congestion Management).¶

Authors' Addresses