Distribution of Service Metadata in BGP FlowSpec

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Table of Contents

1. Introduction

Many modern services deploy their service instances in multiple sites to get better response time and resource utilization. These sites are often geographically distributed to serve the user demand. For some services such as VR/AR and intelligent transportation, the QoE will depend on both the network metrics and the compute metrics. For example, if the nearest site is overloaded due to the demand fluctuation, then steer the user traffic to another light-loaded sites may improve the QoE. To steer the traffic to the best site, the computing metadata of the site needs to be collected.¶

[I-D.ietf-idr-5g-edge-service-metadata] describes the BGP extension of distributing service route with network and computing-related metrics. The router connected to the site will received the service routes and service metadata sent from devices inside the edge site, and then generates the corresponding routes and distributes them to ingress routers. However, the route with service metadata on the router connected to the site can be also collected by a central controller using BGP LS. Then the central controller may process the metadata and distributes the result to the ingress router using BGP FlowSpec.¶

This document defines an extension of BGP FlowSpec to carry the service metadata along with the service route which is received from the controller. Using the service metadata and the service route, the ingress router can calculate the best site for the traffic, giving each user the best QoE.¶

2. BGP FlowSpec Extension for Service Metadata

The goal of the BGP FlowSpec extension is to distribute the information of the service route and metadata. A service is identified by an prefix and this information is carried using the existing Destination Prefix Component specified in [RFC8955] and [RFC8956]. [I-D.ietf-idr-ts-flowspec-srv6-policy] defines that the Color Extended Community and BGP Prefix-SID attribute is carried in the context of the FlowSpec NLRI.¶

In addition to that, this document proposes to carry the service metadata attribute(See Figure 1). The ingress router can compare the compute metric of different sites and steer the traffic into the best one using the SR policy. The metadata can be original values defined in [I-D.ietf-idr-5g-edge-service-metadata] or an aggregated one calculated using original values.¶

   +------------+
   |  BGP FS    |
   | Controller |
   +------------+
      | FlowSpec route to Ingress:
      |   NLRI: Destination Prefix
      |   Redirect to IPv6 Nexthop: Egress's Address
      |   Policy Color: C1
      |   PrefixSID: End.X1
      |   Service Metadata: Compute metric
      |          .-----.
      |         (       )
      V     .--(         )--.
+-------+  (                 )  +------+          +---------+
|       |_( SRv6 Core Network )_|      | (End.X1) |         |
|Ingress| ( ================> ) |Egress|----------|   Site  |
+-------+  (SR List<S1,S2,S3>)  +------+          +---------+
            '--(         )--'
                (       )
                 '-----'

   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
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |    Aggregated Metadata Type   |            Length             |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |            Aggregated Metric Value (4 octets)                 |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

3. Security Considerations

TBD¶

4. IANA Considerations

This document requires IANA to assign the following code points from the registry called "BGP Path Attributes":¶

Authors' Addresses