CDNI Request Routing Extensions
draft-ietf-cdni-request-routing-extensions-07

Document Type Active Internet-Draft (cdni WG)
Last updated 2019-10-17 (latest revision 2019-09-24)
Replaces draft-finkelman-cdni-rr-sva-extensions
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Network Working Group                                       O. Finkelman
Internet-Draft                                                     Qwilt
Intended status: Standards Track                               S. Mishra
Expires: March 26, 2020                                          Verizon
                                                      September 23, 2019

                    CDNI Request Routing Extensions
             draft-ietf-cdni-request-routing-extensions-07

Abstract

   Open Caching is a use case of Content Delivery Networks
   Interconnetion (CDNI) in which the commercial Content Delivery
   Network (CDN) is the upstream CDN (uCDN) and the ISP caching layer
   serves as 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 also applicable to
   CDNI use cases in general.

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.

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 March 26, 2020.

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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
   (https://trustee.ietf.org/license-info) 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  . . . . . . . . . . . . . . . . .   3
     2.1.  Properties of Redirect Target Capability Object . . . . .   5
     2.2.  DnsTarget . . . . . . . . . . . . . . . . . . . . . . . .   6
     2.3.  HttpTarget  . . . . . . . . . . . . . . . . . . . . . . .   7
     2.4.  Usage Example . . . . . . . . . . . . . . . . . . . . . .   9
   3.  Fallback Target Address Metadata  . . . . . . . . . . . . . .  10
     3.1.  Properties of Fallback Target Address Metadata Object . .  11
     3.2.  Usage Example . . . . . . . . . . . . . . . . . . . . . .  12
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  14
     4.1.  CDNI Payload Types  . . . . . . . . . . . . . . . . . . .  14
       4.1.1.  CDNI FCI RedirectTarget Payload Type  . . . . . . . .  14
       4.1.2.  CDNI MI FallbackTarget Payload Type . . . . . . . . .  14
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  14
     5.1.  Confidentiality and Privacy . . . . . . . . . . . . . . .  15
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  15
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  15
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  15
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  16
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  16

1.  Introduction

   The Open Caching working group of the Streaming Video Alliance (SVA)
   is focused on the delegation of video delivery requests from
   commercial CDNs to a caching layer at the Internet Service Provider's
   (ISP) network.  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).  This document defines and registers
   CDNI generic metadata object [RFC8006] and CDNI Footprint and

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   Capabilities object [RFC8008] that are required for Open Caching
   request routing.  For consistency with other CDNI documents this
   document follows the CDNI convention of uCDN (upstream CDN) and dCDN
   (downstream CDN) to represent the commerical CDN and ISP caching
   layer respectively.

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

   o  Redirect Target Capability (for dCDN advertising redirect target
      address)

   o  Fallback Target Metadata (for uCDN configuring fallback target
      address)

1.1.  Terminology

   The following terms are used throughout this document:

   o  FQDN - Fully Qualified Domain Name

   o  CDN - Content Delivery Network

   Additionaly, this document reuses the terminology defined in
   [RFC6707], [RFC7336], [RFC8006], [RFC8007], and [RFC8008].
   Specifically, we use the following CDNI acronyms:

   o  FCI - Footprint and Capability Interface (see [RFC8008])

   o  MI - Metadata Interface (see [RFC8006])

   o  uCDN, dCDN - Upstream CDN and Downstream CDN respectively (see
      [RFC7336])

   o  RT - Redirection Target.  Endpoint for redirection from uCDN to
      dCDN.

   o  RR - Request Router.  An element responsible for routing user
      requests.

2.  Redirect Target Capability

   Iterative request redirection is defined in Section 1.1 of [RFC7336]
   and elaborated by examples in Sections 3.2 and 3.4 of [RFC7336].  A
   Redirection Target (RT) is defined in Section 2 of [RFC7975] for
   Recursive Request Redirection as:

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      "The endpoint to which the User Agent is redirected.  In CDNI, a
      RT may point to a number of different components, some examples
      include a surrogate in the same CDN as the request router, a
      request router in a dCDN, or a surrogate in a dCDN".

   In this document we adopt the same defintion of the RT for the
   Iterative Request Redirect use case.  This use case requires the
   provisioning of the RT address to be used by the uCDN in order to
   redirect to the dCDN.  RT 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 address, it
   may not be suitable to advertise it during bootstrap.  A more dynamic
   and footprint oriented interface is required.  Section 4.3 of
   [RFC7336] suggests that it could be one of the roles of the FCI
   [RFC8008].  Following this suggestion we have, therefore, chosen to
   use the CDNI Footprint and Capabilities interface for redirect target
   address 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 this
   case, the uCDN can redirect to that dCDN address, only if the User
   Agent request was to one of these uCDN hosts.

   A redirect target for DNS redirection is an IPv4 address used as an A
   record response, an IPv6 address used as an AAAA record response or a

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   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 available.

   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]).

   If the redirect target capability object does not contain a target or
   the target is empty, the uCDN MUST interpret it as "no target
   available for these uCDN hosts for the specified footprint".  In case
   such a target was already advertised in a previous FCI object, the
   uCDN MUST interperet it as an update that deletes the previous
   redirect target.

2.1.  Properties of Redirect Target Capability Object

   The Redirect Target capability object consists of the following
   properties:

      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
         [RFC8006])

         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, AAAA record or
         CNAME record.

         Type: DnsTarget object (see Section 2.2)

         Mandatory-to-Specify: No.  If the dns-target is not present or
         empty the uCDN MUST interpret it as "no dns-target available".

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      Property: http-target

         Description: Target URI for a HTTP redirect.

         Type: HttpTarget object (see Section 2.3)

         Mandatory-to-Specify: No.  If the http-target is not present or
         empty the uCDN MUST interpret it as "no http-target available".

   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
   target.  The capabilities object is serialized as a JSON object as
   defined in Section 5 of [RFC8008]

   {
     "capabilities": [
       {
         "capability-type": "FCI.RedirectTarget",
         "capability-value": {
             "redirecting-hosts": [
                "a.service123.ucdn.example.com",
                "b.service123.ucdn.example.com"
             ],
             "dns-target": {
                "host": "service123.ucdn.dcdn.example.com"
             },
             "http-target": {
                 "host": "us-east1.dcdn.example.com",
                 "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

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         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": "service123.ucdn.dcdn.example.com"
    }

   The following is an example of a DNS query for uCDN address
   "a.service123.ucdn.example.com" and the corresponding CNAME
   redirection response:

    Query:
    a.service123.ucdn.example.com:
    type A, class IN

    Response:
    a.service123.ucdn.example.com:
    type CNAME, class IN, cname service123.ucdn.dcdn.example.com

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.

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         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
         URL.

         Type: Boolean.

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

   Example of HttpTarget object with a path-prefix and include-
   redirecting-host:

   {
      "host": "us-east1.dcdn.example.com",
      "path-prefix": "/cache/1/",
      "include-redirecting-host": true
   }

   Example of a HTTP request for content at uCDN host
   "a.service123.ucdn.example.com" 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:

    Request:
    GET /vod/1/movie.mp4 HTTP/1.1
    Host: a.service123.ucdn.example.com

    Response:
    HTTP/1.1 302 Found
    Location: http://us-east1.dcdn.example.com/cache/1/
    a.service123.ucdn.example.com/vod/1/movie.mp4

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2.4.  Usage Example

   Before requests can be routed from the uCDN to the dCDN the CDNs must
   exchange service configurations between them.  Using the MI the uCDN
   advertises out-of-band its hosts to the dCDN, each host is designated
   by a host name and has its own specific metadata (see Section 4.1.2
   of [RFC8006].  The dCDN, using the FCI, advertises, also out-of-band,
   the redirect target address object defined in Section 2.1 for the
   relevant uCDN hosts.  The following is a generalized example of the
   message flow between an upstream CDN and a downstream dCDN.  For
   simplicity, we focus on the sequence of messages between the uCDN and
   dCDN and not on how they are passed.

     dCDN                                                    uCDN
       +                                                       +
       |                                                       |
   (1) | MI:  host: s123.ucdn.example.com                      |
       |      host-metadata: < metadata >                      |
       <-------------------------------------------------------+
       |                                                       |
   (2) | FCI:  capability-type: FCI.RedirectTarget             |
       |       redirecting-hosts: us-east1.dcdn.example.com    |
       |       target host: s123.ucdn.example.com              |
       +------------------------------------------------------->
       |                                                       |
       |                                                       |
       +                                                       +

       Figure 1: Redirect target address advertisement

   1.  The uCDN advertises a host (s123.ucdn.example.com) with the host
       metadata.

   2.  The dCDN adveritses its FCI objects to the uCDN including a
       FCI.RedirectTarget object that contains the redirect target
       address (us-east1.dcdn.example.com) specified for that uCDN host.

   Once the redirect target has been set, the uCDN can start redirecting
   user requests to the dCDN.  The following is a generic sequence of
   redirection using the host and redirect target that were advertised
   in Figure 1 above.

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   End User                  dCDN                   uCDN RR
       +                       +                       +
       |                       |                       |
   (1) | Request sent s123.ucdn.example.com            |
       +-----------------------+----------------------->
       |                       |                       |
   (2) | Redirect to us-east1.dcdn.example.com         |
       <-----------------------+-----------------------+
       |                       |                       |
   (3) | Request us-east1.dcdn.example.com             |
       +----------------------->                       |
       |                       |                       |
   (4) | Response              |                       |
       <-----------------------+                       |
       |                       |                       |
       +                       +                       +

       Figure 2: Generic requests redirection sequence

   1.  The End User sends a request (DNS or HTTP) to the uCDN Request
       Router (RR).

   2.  Using the previously advertised Redirect Target, the uCDN
       redirects the request to the dCDN.

   3.  The End User sends a request to the dCDN.

   4.  The dCDN either sends a response or reroutes it, for example, to
       a dCDN surrogate.

3.  Fallback Target Address Metadata

   Open Caching requires that the uCDN provides 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 different 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.

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   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, AAAA
   record or CNAME record in case of DNS redirection or a hostname for
   HTTP redirect.

   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
   dCDN.

3.1.  Properties of 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
         client.

         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.

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

3.2.  Usage Example

   The uCDN advertises out-of-band the fallback target address to the
   dCDN, so that the dCDN may redirect a request back to the uCDN in
   case the dCDN cannot serve it.  Using the MI the uCDN advertises its
   hosts to the dCDN, along with their specific host metadata (see
   Section 4.1.2 of [RFC8006].  The Fallback Target generic metadata
   object is encapsulated within the "host-metadata" property of each
   host.  The following is an example of a message flow between an
   upstream CDN and a downstream dCDN.  For simplicity, we focus on the
   sequence of messages between the uCDN and dCDN, not on how they are
   passed.

     dCDN                                                    uCDN
       +                                                       +
       |                                                       |
   (1) | MI:  host: s123.ucdn.example.com                      |
       |      host-metadata:                                   |
       |          < metadata objects >                         |
       |          < MI.FallbackTarget                          |
       |            host: fallback-a.service123.ucdn.example > |
       |          < metadata objects >                         |
       <-------------------------------------------------------+
       |                                                       |
   (2) | FCI:  capability-type: FCI.RedirectTarget             |
       |       redirecting-hosts: us-east1.dcdn.example.com    |
       |       target host: s123.ucdn.example.com              |
       +------------------------------------------------------->
       |                                                       |
       |                                                       |
       +                                                       +

       Figure 3: Advertisement of host metadata with Fallback Target

   1.  The uCDN advertises a host (s123.ucdn.example.com) with the host
       metadata.  The host-metadata property contains a
       MI.FallbackTarget object.

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   2.  The dCDN adveritses its FCI objects to the uCDN including a
       FCI.RedirectTarget object that contains the redirect target
       address (us-east1.dcdn.example.com) specified for that uCDN host.

   The following is a generic sequence of redirection using the
   configurations that were advertised in Figure 3 above.  In this case
   the dCDN redirects back to the uCDN fallback target address.

   End User              dCDN            uCDN fallback          uCDN RR
       +                   +                   +                   +
       |                   |                   |                   |
   (1) | Request sent s123.ucdn.example.com    |                   |
       +-------------------+-------------------+------------------->
       |                   |                   |                   |
   (2) | Redirect to us-east1.dcdn.example.com |                   |
       <-------------------+-------------------+-------------------+
       |                   |                   |                   |
   (3) | Request us-east1.dcdn.example.com     |                   |
       +------------------->                   |                   |
       |                   |                   |                   |
   (4) | Redirect back to fallback-a.service123.ucdn.example       |
       <-------------------+                   |                   |
       |                   |                   |                   |
   (5) | Request fallback-a.service123.ucdn.example                |
       +--------------------------------------->                   |
       |                   |                   |                   |
   (6) | Response          |                   |                   |
       <-------------------+-------------------+                   |
       |                   |                   |                   |
       +                   +                   +                   +

       Figure 4: Redirection to Fallback Target

   1.  The End User sends a request (DNS or HTTP) to the uCDN Request
       Router (RR).

   2.  Using the previously advertised Redirect Target, the uCDN
       redirects the request to the dCDN.

   3.  The End User sends a request to the dCDN.

   4.  The dCDN cannot handled the request and, therefore, redirects it
       back to the uCDN fallback target address.

   5.  The End User sends the request to the uCDN fallback target
       address.

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   6.  The uCDN either sends a response or reroutes it, for example, to
       a uCDN surrogate.

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
   [RFC7736]:

                  +--------------------+---------------+
                  | 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
   advertisement)

   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]
   respectively.

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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,
              <https://www.rfc-editor.org/info/rfc1034>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [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,
              <https://www.rfc-editor.org/info/rfc3986>.

   [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, <https://www.rfc-editor.org/info/rfc6707>.

   [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,
              <https://www.rfc-editor.org/info/rfc7231>.

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   [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, <https://www.rfc-editor.org/info/rfc7336>.

   [RFC7975]  Niven-Jenkins, B., Ed. and R. van Brandenburg, Ed.,
              "Request Routing Redirection Interface for Content
              Delivery Network (CDN) Interconnection", RFC 7975,
              DOI 10.17487/RFC7975, October 2016,
              <https://www.rfc-editor.org/info/rfc7975>.

   [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,
              <https://www.rfc-editor.org/info/rfc8006>.

   [RFC8007]  Murray, R. and B. Niven-Jenkins, "Content Delivery Network
              Interconnection (CDNI) Control Interface / Triggers",
              RFC 8007, DOI 10.17487/RFC8007, December 2016,
              <https://www.rfc-editor.org/info/rfc8007>.

   [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,
              <https://www.rfc-editor.org/info/rfc8008>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

7.2.  Informative References

   [RFC7736]  Ma, K., "Content Delivery Network Interconnection (CDNI)
              Media Type Registration", RFC 7736, DOI 10.17487/RFC7736,
              December 2015, <https://www.rfc-editor.org/info/rfc7736>.

   [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,
              <https://www.rfc-editor.org/info/rfc7871>.

Authors' Addresses

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   Ori Finkelman
   Qwilt
   6, Ha'harash
   Hod HaSharon  4524079
   Israel

   Email: ori.finkelman.ietf@gmail.com

   Sanjay Mishra
   Verizon
   13100 Columbia Pike
   Silver Spring, MD  20904
   USA

   Email: sanjay.mishra@verizon.com

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