RESTCONF Extension to support Trace Context Headers

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Table of Contents

1. Introduction

Network automation and management systems commonly consist of multiple sub-systems and together with the network devices they manage, they effectively form a distributed system. Distributed tracing is a methodology implemented by tracing tools to follow, analyze and debug operations, such as configuration transactions, across multiple distributed systems. An operation is uniquely identified by a trace-id and through a trace context, carries some metadata about the operation. Propagating this "trace context" between systems enables forming a coherent view of the entire operation as carried out by all involved systems.¶

The W3C has defined two HTTP headers (traceparent and tracestate) for context propagation that are useful for distributed systems like the ones defined in [RFC8309]. The goal of this document is to adopt this W3C specification for the RESTCONF protocol.¶

This document does not define new HTTP extensions but makes those defined in [W3C-Trace-Context] optional headers for the RESTCONF protocol.¶

In [I-D.draft-ietf-netconf-trace-ctx-extension-01], the NETCONF protocol extension is defined and we will re-use several of the YANG and XML objects defined in that document for RESTCONF. Please refer to that document for additional context and example applications.¶

2. RESTCONF Extensions

A RESTCONF server MUST support the trace context traceparent header as defined in [W3C-Trace-Context].¶

A RESTCONF server SHOULD support the trace context tracestate header as defined in [W3C-Trace-Context].¶

  error-tag:      operation-failed
  error-type:     protocol
  error-severity: error

3. Security Considerations

There are two YANG modules specified in this document. These modules are completely empty, and therefore have very limited security considerations. Their purpose is only to indicate which trace context header versions the server supports using YANG Library [RFC8525].¶

Even though both YANG modules are empty, there are still some security considerations worth mentioning, however. This is because the functionality described in this document is in the form of additional HTTP headers (which cannot be described using YANG) relating to the network management protocol RESTCONF [RFC8040].¶

The traceparent and tracestate headers make it easier to track the flow of requests and their downstream effect on other systems. This is indeed the whole point with these headers. This knowledge could also be of use to bad actors that are working to build a map of the managed network.¶

All advice mentioned in the [W3C-Trace-Context] under the Privacy Considerations and Security Considerations also apply to this document.¶

The lowest RESTCONF layer is HTTPS, and the mandatory-to-implement secure transport is TLS [RFC8446].¶

The Network Configuration Access Control Model (NACM) [RFC8341] provides the means to restrict access for particular NETCONF or RESTCONF users to a preconfigured subset of all available NETCONF or RESTCONF protocol operations and content.¶

4. IANA Considerations

This document has no IANA actions.¶

5. Acknowledgments

The authors would like to acknowledge the valuable implementation feedback from Christian Rennerskog and Per Andersson. Many thanks to Raul Rivas Felix, Alexander Stoklasa, Luca Relandini and Erwin Vrolijk for their help with the demos regarding integrations. The help and support from Jean Quilbeuf and Benoît Claise has also been invaluable to this work.¶

Appendix A. Example RESTCONF calls

All examples from [RFC8040] Appendix B could be recreated in this seciton by adding the new header described in this document. We selected one example from that document as reference.¶

  POST /restconf/data/example-jukebox:jukebox/library HTTP/1.1
  Host: example.com
  Content-Type: application/yang-data+json
  traceparent: 00-405062f633be64ee006089dfca95a153-e021f9e263aad8e2-01
  tracestate: vendorname1=opaqueValue1,vendorname2=opaqueValue2

  {
    "example-jukebox:artist" : [
      {
        "name" : "Foo Fighters"
      }
    ]
  }

  HTTP/1.1 201 Created
  Date: Thu, 26 Jan 2017 20:56:30 GMT
  Server: example-server
  Location: https://example.com/restconf/data/\
      example-jukebox:jukebox/library/artist=Foo%20Fighters
  Last-Modified: Thu, 26 Jan 2017 20:56:30 GMT
  ETag: "b3830f23a4c"
  traceparent: 00-405062f633be64ee006089dfca95a153-e021f9e263aad8e2-01
  tracestate: vendorname1=opaqueValue1,vendorname2=opaqueValue2

  POST /restconf/data/example-jukebox:jukebox/library HTTP/1.1
  Host: example.com
  Content-Type: application/yang-data+json
  traceparent: 00-405062f633be64ee006089dfca95a153-e021f9e263aad8e2-01
  tracestate: SomeBadFormatHere

  {
    "example-jukebox:artist" : [
      {
        "name" : "Foo Fighters"
      }
    ]
  }

 HTTP/1.1 400 Bad Request
 Date: Tue, 20 Jun 2023 20:56:30 GMT
 Server: example-server
 Content-Type: application/yang-data+json

 { "ietf-restconf:errors" : {
     "error" : [
       {
         "error-type" : "protocol",
         "error-tag" : "operation-failed",
         "error-severity" : "error",
         "error-message" :
           "OTLP traceparent attribute incorrectly formatted",
         "error-info": {
           "ietf-netconf-otlp-context:meta-name" : "tracestate",
           "ietf-netconf-otlp-context:meta-value" :
             "SomeBadFormatHere",
           "ietf-netconf-otlp-context:error-type" :
             "ietf-netconf-otlp-context:bad-format"
         }
       }
     ]
   }
 }

Appendix B. Changes (to be deleted by RFC Editor)

Authors' Addresses