Network Working Group                                       O. Finkelman
Internet-Draft                                                     Qwilt
Intended status: Standards Track                               S. Mishra
Expires: January 29, February 10, 2020                                       Verizon
                                                           July 28,
                                                          August 9, 2019

                    CDNI Request Routing Extensions


   The Open Caching working group of the Streaming Video Alliance is
   focused on the delegation of video delivery requests from commercial
   CDNs to a caching layer at the ISP.  In that aspect, Open Caching is
   a specific use case of CDNI, where the commercial CDN is the upstream
   CDN (uCDN) and the ISP caching layer is the downstream CDN (dCDN).
   The extensions specified in this document to the CDNI Metadata and
   FCI interfaces are derived from requirements raised by Open Caching
   but are applicable to CDNI use cases in general.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   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
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at

   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 January 29, February 10, 2020.

Copyright Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   ( 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 extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Redirect Target Capability Object . . . . . . . . . . . . . .   3
     2.1.  Properties of Redirect Target Capability Object . . . . .   4
     2.2.  DnsTarget . . . . . . . . . . . . . . . . . . . . . . . .   6
     2.3.  HttpTarget  . . . . . . . . . . . . . . . . . . . . . . .   6
   3.  Fallback Target Address Metadata  . . . . . . . . . . . . . .   8
     3.1.  Properties Fallback Target Address Metadata Object  . . .   9
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
     4.1.  CDNI Payload Types  . . . . . . . . . . . . . . . . . . .   9
       4.1.1.  CDNI FCI RedirectTarget Payload Type  . . . . . . . .  10
       4.1.2.  CDNI MI FallbackTarget Payload Type . . . . . . . . .  10
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
     5.1.  Confidentiality and Privacy . . . . . . . . . . . . . . .  10
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  10
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  11
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction

   This document defines objects needed for Open Caching request
   routing.  For that purpose it extends CDNI metadata [RFC8006] and
   CDNI Footprint and Capabilities [RFC8008].  For consistency, this
   document follows the CDNI notation of uCDN (the commercial CDN) and
   dCDN (the ISP caching layer).

   This document also registers CDNI Payload Types [RFC7736] for the
   defined objects:

   o  Redirect Target Capability (for dCDN advertising redirect target

   o  Fallback Target Metadata (for uCDN configuring fallback target

1.1.  Terminology

   This document reuses the terminology defined in [RFC6707], [RFC8006],
   [RFC8007], and [RFC8008].

   Additionally, the following terms are used throughout this document
   and are defined as follows:

   o  RR - Request Router

   o  CP - Content Provider

2.  Redirect Target Capability Object

   Iterative request redirect as defined in section 1.1 of [RFC7336]
   requries the provisioning of a redirect target address to be used by
   the uCDN in order to redirect to the dCDN.  Redirect target addresses
   can vary between different footprints, for example, between different
   regions, and they may also change over time, for example as a result
   of network problems.  Given this variable and dynamic nature of the
   redirect target, it may not be suitable to advertise it during
   bootstrap.  A more dynamic and footprint oriented interface is
   required.  Therefore, we have chosen to use the CDNI Footprint and
   Capabilities interface for redirect target advertisement.

   Use cases

   o  Footprint: The dCDN may want to have a different target per
      footprint.  Note that a dCDN may spread across multiple
      geographies.  This makes it easier to route client requests to a
      nearby request router.  Though this can be achieved using a single
      canonical name and Geo DNS, that approach has limitations; for
      example a client may be using a third party DNS resolver, making
      it impossible for the redirector to detect where the client is
      located, or Geo DNS granularity may be too rough for the
      requirement of the application.

   o  Scaling: The dCDN may choose to scale its request routing service
      by deploying more request routers in new locations and advertise
      them via an updatable interface like the FCI.

   The Redirect Target capability object is used to indicate the target
   address the uCDN should use in order to redirect a client to the
   dCDN.  A target may be attached to a specific uCDN host, a list of
   uCDN hosts, or used globally for all the hosts of the uCDN.

   When a dCDN is attaching the redirect target to a specific uCDN host
   or a list of uCDN hosts, the dCDN MUST advertise the hosts within the
   Redirect Target capability object as "redirecting-hosts".  In that
   case, the uCDN can redirect to that dCDN address, only if the request
   was directed to one of those uCDN hosts.

   A redirect target for DNS redirection is an IP address used as an A
   record response or a FQDN used as an alias in a CNAME record response
   (see [RFC1034]) of the uCDN DNS router.  Note that DNS routers make
   routing decisions based on either the DNS resolver's IP address or
   the client IP address when EDNS0 client-subnet is used (see
   [RFC7871]).  The dCDN may choose to advertise redirect targets and
   footprints to cover both cases.  A uCDN DNS router implemenation
   SHOULD prefer routing based on client IP address when it is

   A redirect target for HTTP redirection is the URI to be used as the
   value for the Location header of a HTTP redirect 3xx response,
   typically a 302 (Found) (see section 7.1.2 of [RFC7231] and section
   6.4 of [RFC7231]).

2.1.  Properties of Redirect Target Capability Object

   The Redirect Target capability object consists of the following

      Property: redirecting-hosts

         Description: One or more uCDN hosts to which this redirect
         target is attached.  A redirecting host SHOULD be a host that
         was published in a HostMatch object by the uCDN as defined in
         section 4.1.2 of [RFC8006].

         Type: A list of Endpoint objects (see section 4.3.3 of

         Mandatory-to-Specify: No.  If not present, or empty, the
         redirect target applies to all hosts of the redirecting uCDN.

      Property: dns-target

         Description: Target address for a DNS A record or CNAME record.

         Type: DnsTarget object (see Section 2.2)

         Mandatory-to-Specify: No. but at least one of "dns-target" or
         "http-target" MUST be present and non-empty.

      Property: http-target

         Description: Target URI for a HTTP redirect.

         Type: HttpTarget object (see Section 2.3)

         Mandatory-to-Specify: No, but at least one of "dns-target" or
         "http-target" MUST be present and non-empty.

   The following is an example of a Redirect Target capability object
   serialization that advertises a dCDN target address that is attached
   to a specific list of uCDN "redirecting-hosts".  A uCDN host that is
   included in that list can redirect to the advertised dCDN redirect

     "capabilities": [
         "capability-type": "FCI.RedirectTarget",
         "capability-value": {
             "redirecting-hosts": [
             "dns-target": {
                "host": "" ""
             "http-target": {
                 "host": "", "",
                 "path-prefix": "/cache/1/",
                 "include-redirecting-host": true
         "footprints": [
             <Footprint objects>

2.2.  DnsTarget

   The DnsTarget object gives the target address for the DNS response to
   delegate from the uCDN to the dCDN.

      Property: host

         Description: The host property is a hostname or an IP address,
         without a port number.

         Type: Endpoint object as defined in section 4.3.3 of [RFC8006]
         with the limitation that it SHOULD NOT include a port number
         and, in case a port number is present, the uCDN MUST ignore it.

         Mandatory-to-Specify: Yes.

   The following is an example of DnsTarget object:

       "host": "" ""

   The following is an example of a DNS query for uCDN address
   "" and the corresponding CNAME
   redirection response:

    type A, class IN

    type CNAME, class IN, cname

2.3.  HttpTarget

   The HttpTarget object gives the necessary information to construct
   the target Location URI for HTTP redirection.

      Property: host

         Description: Hostname or IP address and an optional port, i.e.,
         the host and port of the authority component of the URI as
         described in section 3.2 of [RFC3986].

         Type: Endpoint object as defined in section 4.3.3 of [RFC8006].

         Mandatory-to-Specify: Yes.

      Property: path-prefix

         Description: A path prefix for the HTTP redirect Location
         header.  The original path is appended after this prefix.

         Type: A prefix of a path-absolute as defined in section 3.3 of
         [RFC3986].  The prefix MUST end with a trailing slash, to
         indicate the end of the last path segment in the prefix.

         Mandatory-to-Specify: No.  If this property is absent or empty,
         the uCDN MUST NOT prepend a path prefix to the original content
         path, i.e., the original path MUST appear in the location URI
         right after the authority component.

      Property: include-redirecting-host

         Description: A flag indicating whether or not to include the
         redirecting host as the first path segment after the path-
         prefix.  If set to true and a "path-prefix" is used, the uCDN
         redirecting host MUST be added as a separate path segment after
         the path-prefix and before the original URL path.  If set to
         true and there is no path-prefix, the uCDN redirecting host
         MUST be prepended as the first path segment in the redirect

         Type: Boolean.

         Mandatory-to-Specify: No.  Default value is False.

   Example of HttpTarget object with a path-prefix and include-

      "host": "", "",
      "path-prefix": "/cache/1/",
      "include-redirecting-host": true

   Example of a HTTP request for content at uCDN host
   "" and the corresponding HTTP response
   with Location header used for redirecting the client to the dCDN
   using the the http-target in the above example:

    GET /vod/1/movie.mp4 HTTP/1.1

    HTTP/1.1 302 Found

3.  Fallback Target Address Metadata

   Open Caching requires that the uCDN provide a fallback target server
   to the dCDN, to be used in cases where the dCDN cannot properly
   handle the request.  To avoid redirect loops, the fallback target
   server's address at the uCDN MUST be differnet from the original uCDN
   address from which the client was redirected to the dCDN.  The uCDN
   MUST avoid further redirection when receiving the client request at
   the fallback target.  The fallback target is defined as a generic
   metadata object (see section 3.2 of [RFC8006])

   Use cases

   o  Failover: A dCDN request router receives a request but has no
      caches to which it can route the request.  This can happen in the
      case of failures or temporary network overload.

   o  No coverage: A dCDN request router receives a request from a
      client located in an area inside the footprint but not covered by
      the dCDN caches or outside the dCDN footprint coverage.  In such
      cases, the router may choose to redirect the request back to the
      uCDN fallback address.

   o  Error: A cache may receive a request that it cannot properly
      serve, for example, some of the metadata objects for that service
      were not properly acquired.  In this case, the cache may resolve
      to redirect back to uCDN.

   The Fallback target metadata object is used to indicate the target
   address the dCDN should use in order to redirect a client back to the
   uCDN.  Fallback target is represented as endpoint objects as defined
   in section 4.3.3 of [RFC8006].

   The uCDN fallback target address may be used as a DNS A record or
   CNAME record in case of DNS redirection or a hostname for HTTP

   When using HTTP redirect to route a client request back to the uCDN,
   it is the dCDN's responsibility to use the original URL path as the
   client would have used for the original uCDN request, stripping, if
   needed, the dCDN path-prefix and/or the uCDN hostname from the
   redirect URL that may have been used to request the content from the

3.1.  Properties Fallback Target Address Metadata Object

   The MI.FallbackTarget Metadata object consists of the following
   single property:

      Property: host

         Description: Target address to which the dCDN can redirect the

         Type: Endpoint object as defined in section 4.3.3 of [RFC8006]
         with the limitation that in case of DNS delegation it SHOULD
         NOT include a port number and, in case a port number is
         present, the dCDN MUST ignore it.

         Mandatory-to-Specify: Yes.

   Example of a MI.FallbackTarget Metadata object that designates the
   host address the dCDN should use as fallback address to redirect back
   to the uCDN.

       "generic-metadata-type": "MI.FallbackTarget",
           "host": "fallback-a.service123.ucdn.example"

4.  IANA Considerations

4.1.  CDNI Payload Types

   This document requests the registration of the following CDNI Payload
   Types under the IANA "CDNI Payload Types" registry defined in

                  | Payload Type       | Specification |
                  | FCI.RedirectTarget | RFCthis       |
                  | MI.FallbackTarget  | RFCthis       |

   [RFC Editor: Please replace RFCthis with the published RFC number for
   this document.]

4.1.1.  CDNI FCI RedirectTarget Payload Type

   Purpose: The purpose of this payload type is to distinguish
   RedirectTarget FCI objects

   Interface: FCI

   Encoding: see Section 2.1

4.1.2.  CDNI MI FallbackTarget Payload Type

   Purpose: The purpose of this payload type is to distinguish
   FallbackTarget MI objects (and any associated capability

   Interface: MI/FCI

   Encoding: see Section 3.1

5.  Security Considerations

   This specification is in accordance with the CDNI Metadata Interface
   and the CDNI Request Routing: Footprint and Capabilities Semantics.
   As such, it is subject to the security and privacy considerations as
   defined in Section 8 of [RFC8006] and in Section 7 of [RFC8008]

5.1.  Confidentiality and Privacy

   The redirect Target FCI object potentially exposes information about
   the internal strcture of the dCDN network.  A third party could
   intercept the FCI transactions and use the information to attack the
   dCDN.  An implemenation of the FCI MUST therefore use strong
   authentication and encryption and strictly follow the directions for
   securing the interface as defined for the Metadata Interface in
   Section 8.3 of [RFC8006].

6.  Acknowledgements

   The authors thank Nir B.  Sopher for reality checks against
   production use cases, his contribution is significant to this
   document.  The authors also thank Ben Niven-Jenkins for his review
   and feedback and Kevin J.  Ma for his guidance throughout the
   development of this document including his regular reviews.

7.  References

7.1.  Normative References

   [RFC1034]  Mockapetris, P., "Domain names - concepts and facilities",
              STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, DOI 10.17487/RFC3986, January 2005,

   [RFC7231]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
              DOI 10.17487/RFC7231, June 2014,

   [RFC8006]  Niven-Jenkins, B., Murray, R., Caulfield, M., and K. Ma,
              "Content Delivery Network Interconnection (CDNI)
              Metadata", RFC 8006, DOI 10.17487/RFC8006, December 2016,

   [RFC8007]  Murray, R. and B. Niven-Jenkins, "Content Delivery Network
              Interconnection (CDNI) Control Interface / Triggers",
              RFC 8007, DOI 10.17487/RFC8007, December 2016,

   [RFC8008]  Seedorf, J., Peterson, J., Previdi, S., van Brandenburg,
              R., and K. Ma, "Content Delivery Network Interconnection
              (CDNI) Request Routing: Footprint and Capabilities
              Semantics", RFC 8008, DOI 10.17487/RFC8008, December 2016,

7.2.  Informative References

   [RFC6707]  Niven-Jenkins, B., Le Faucheur, F., and N. Bitar, "Content
              Distribution Network Interconnection (CDNI) Problem
              Statement", RFC 6707, DOI 10.17487/RFC6707, September
              2012, <>.

   [RFC7336]  Peterson, L., Davie, B., and R. van Brandenburg, Ed.,
              "Framework for Content Distribution Network
              Interconnection (CDNI)", RFC 7336, DOI 10.17487/RFC7336,
              August 2014, <>.

   [RFC7736]  Ma, K., "Content Delivery Network Interconnection (CDNI)
              Media Type Registration", RFC 7736, DOI 10.17487/RFC7736,
              December 2015, <>.

   [RFC7871]  Contavalli, C., van der Gaast, W., Lawrence, D., and W.
              Kumari, "Client Subnet in DNS Queries", RFC 7871,
              DOI 10.17487/RFC7871, May 2016,

Authors' Addresses

   Ori Finkelman
   6, Ha'harash
   Hod HaSharon  4524079


   Sanjay Mishra
   13100 Columbia Pike
   Silver Spring, MD  20904