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<?rfc toc="yes"?>
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<?rfc tocdepth="4"?>
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<rfc category="std" docName="draft-ietf-cdni-request-routing-extensions-02" ipr="trust200902">
  <front>
    <title abbrev="CDNI Request Routing Extensions">CDNI Request Routing Extensions</title>

    <author fullname="Ori Finkelman" initials="O." surname="Finkelman">
      <organization>Qwilt</organization>

      <address>
        <postal>
          <street>6, Ha'harash</street>

          <city>Hod HaSharon</city>

          <region></region>

          <code>4524079</code>

          <country>Israel</country>
        </postal>

        <phone>+972-72-2221647</phone>

        <email>ori.finkelman.ietf@gmail.com</email>
      </address>
    </author>

    <author fullname="Sanjay Mishra" initials="S." surname="Mishra">
      <organization>Verizon</organization>

      <address>
        <postal>
          <street>13100 Columbia Pike</street>

          <city>Silver Spring</city>

          <region>MD</region>

          <code>20904</code>

          <country>USA</country>
        </postal>

        <phone></phone>

        <email>sanjay.mishra@verizon.com</email>
      </address>
    </author>
    
    <date/>

    <abstract>
      <t>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.</t>
    </abstract>

    <note title="Requirements Language">
      <t>The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
      "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
      document are to be interpreted as described in <xref
      target="RFC2119">RFC 2119</xref>.</t>
    </note>
  </front>

  <middle>
    <section title="Introduction">
      <t>This document defines objects needed for Open Caching request routing. For that purpose it 
         extends CDNI metadata <xref target="RFC8006"/> and CDNI Footprint and Capabilities <xref target="RFC8008"/>.
         For consistency, this document follows the CDNI notation of uCDN 
         (the commercial CDN) and dCDN (the ISP caching layer).</t>
      
      <t>This document also registers CDNI Payload Types <xref target="RFC7736"/> for the defined objects:
          <list style="symbols">
            <t>Redirect Target Capability (for dCDN advertising redirect target address)</t>
            <t>Fallback Target Metadata (for uCDN configuring fallback target address)</t>            
          </list>
      </t>
        
      <section anchor="terminology" title="Terminology">
        <t>This document reuses the terminology defined in <xref
        target="RFC6707"/>, <xref target="RFC8006"/>, <xref target="RFC8007"/>, and <xref target="RFC8008"/>.</t>

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

          <list style="symbols">
            <t>RR - Request Router</t>            
            <t>CP - Content Provider</t>           
          </list>
        </t>
      </section>

    </section>


        <section anchor="redirect-target-capability" title="Redirect Target Address Capability Object">
          <t>Iterative request redirect as defined in section 1.1 of <xref target="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 due to scaling issues a dCDN may need to split different 
             regions over multiple targets, or due to network problems the dCDN may have to change the target address. 
             Due to this variable and dynamic nature of the redirect target, it may not be 
             suitable to advertise it during bootstrap, and 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.</t>
             
          <t>Use cases<list style="symbols">
              <t>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 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.</t>

              <t>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.</t>

          </list></t>
          <t>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 it can be set globally for all the hosts of the uCDN. 
          </t>
          <t>
             When 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 these uCDN hosts.
          </t>
          <t>
             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 <xref target="RFC1034"/>) of the uCDN DNS router. Note that DNS routers take 
             routing decisions based on either the DNS resolver's IP address or the client IP address when EDNS0 client-subnet 
             is used (see <xref target="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.
          </t>
          <t>
             A redirect target for HTTP redirection is the URI to be used as a value of the Location header of a HTTP redirect 3xx response, 
             typically a 302 (Found) (see section 7.1.2 of <xref target="RFC7231"/> and section 6.4 of <xref target="RFC7231"/>). 
          </t>
          <t><list style="empty">
             <t>Property: redirecting-hosts<list style="empty">

               <t>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 <xref target="RFC8006"/>.</t>

               <t>Type: A list of Endpoint objects (see section 4.3.3 of <xref target="RFC8006"/>)</t>

               <t>Mandatory-to-Specify: No. If not present, or empty, the redirect target applies to all hosts of the redirecting uCDN.</t>
             </list></t>
             <t>Property: dns-target<list style="empty">

               <t>Description: Target address for DNS A record or CNAME record.</t>

               <t>Type: DnsTarget object (see <xref target="dns-target"/>)</t>

               <t>Mandatory-to-Specify: No. but at least one of "dns-target" or "http-target" MUST be present and non empty.</t>
             </list></t>
             <t>Property: http-target<list style="empty">

               <t>Description: Target URI for HTTP redirect.</t>

               <t>Type: HttpTarget object (see <xref target="http-target"/>)</t>

               <t>Mandatory-to-Specify: No. but at least one of "dns-target" or "http-target" MUST be present and non empty.</t>
             </list></t>
 
          </list></t>
        <t>Example of Redirect Target Capability object 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.
        </t>

        <figure>
          <artwork><![CDATA[
{
  "capabilities": [
    {
      "capability-type": "FCI.RedirectTarget",
      "capability-value": {
          "redirecting-hosts": [
             "a.service123.ucdn.example.com", 
             "b.service123.ucdn.example.com"
          ]
          "dns-target": {
             "host": "service123.ucdn.example.dcdn.com"
          }
          "http-target": {
             <Properties of an HttpTarget object>
          }
      },
      "footprints": [
          <Footprint objects>
      ]
    }
  ]
}
             ]]></artwork>
          </figure>

            <section anchor="dns-target" title="DnsTarget">
              <t>The DnsTarget object gives the instructions to construct the target address for the DNS response 
                 for delegation from the uCDN to the dCDN.</t>
                              
              <t><list style="empty">
                <t>Property: host<list style="empty">

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

                   <t>Type: Endpoint object as defined in section 4.3.3 of <xref target="RFC8006"/> 
                      with the limitation that it MUST NOT include a port number.</t>

                   <t>Mandatory-to-Specify: Yes.</t>
                </list></t>
             </list></t>
             <t>Example of DnsTarget object:</t>
     
            <figure>
              <artwork><![CDATA[
 {
    "host": "service123.ucdn.example.dcdn.com"
 }
                 ]]></artwork>
              </figure>
              <t>Example of a DNS query for uCDN address "a.service123.ucdn.example.com" and the corresponding CNAME redirection response:</t>
            <figure>
              <artwork><![CDATA[
 Query:
 a.service123.ucdn.example.com: 
 type A, class IN 
 
 Response:
 a.service123.ucdn.example.com: 
 type CNAME, class IN, cname service123.ucdn.example.dcdn.com
                 ]]></artwork>
              </figure>  
            </section>

            <section anchor="http-target" title="HttpTarget">
              <t>The HttpTarget object gives the instructions to construct the target Location URI for http redirection 
                 from the uCDN to the dCDN.</t>
                              
              <t><list style="empty">
                <t>Property: host<list style="empty">

                   <t>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 <xref target="RFC3986"/>.</t>

                   <t>Type: Endpoint object as defined in section 4.3.3 of <xref target="RFC8006"/>.</t>

                   <t>Mandatory-to-Specify: Yes.</t>
                </list></t>
                <t>Property: path-prefix<list style="empty">

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

                   <t>Type: A prefix of a path-absolute as defined in section 3.3 of <xref target="RFC3986"/>. 
                      The prefix MUST end with a trailing slash, to indicate the end of the last path segment in the prefix.</t>

                   <t>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.</t>
                </list></t>
                <t>Property: include-redirecting-host<list style="empty">

                   <t>Description: A flag indicating whether or not to include the redirecting host as the first path segment after the path-prefix.
                      In case this flag is 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. In case this flag is true and there is no path-prefix, the uCDN redirecting 
                      host MUST be prepended as the first path segment in the redirect URL.</t>

                   <t>Type: Boolean.</t>

                   <t>Mandatory-to-Specify: No. Default value is False.</t>
                </list></t>         
             </list></t>
             <t>Example of HttpTarget object with a path-prefix and include-redirecting-host:</t>
     
            <figure>
              <artwork><![CDATA[
{
   "host": "us-east1.dcdn.com",
   "path-prefix": "/cache/1/",
   "include-redirecting-host": true
}
                 ]]></artwork>
              </figure>
              <t>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:</t>
            <figure>
              <artwork><![CDATA[
 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.com/cache/1/
 a.service123.ucdn.example.com/vod/1/movie.mp4
                 ]]></artwork>
              </figure>  
            </section>                   
        </section>

        <section anchor="fallback-target-metadata" title="Fallback Target Address Metadata">
          <t>Open Caching requires that the uCDN should provide 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 than the original address at the uCDN 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 <xref target="RFC8006"/>)</t>
             
          <t>Use cases<list style="symbols">
              <t>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.</t>
            
              <t>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 a client 
                 located outside the dCDN footprint coverage. In such cases, the  router may 
                 choose to redirect the request back to the uCDN fallback address.</t>

              <t>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.</t>
            </list></t>

          <t>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 <xref target="RFC8006"/>.</t>
               
          <t>The uCDN fallback target address may be used as a DNS A record or CNAME record in case of DNS redirection 
             mode or a host name for HTTP redirect.</t>

          <t>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 the uCDN host name from the redirect URL that may have been used to 
             request the content from the dCDN.</t>

          <t><list style="empty">
            <t>Property: host<list style="empty">
            
               <t>Description: Target address to which the dCDN can redirect the client.</t>

               <t>Type: Endpoint object as defined in section 4.3.3 of <xref target="RFC8006"/> 
                  with the limitation that in case of DNS delegation, it MUST NOT include a port number.</t>

               <t>Mandatory-to-Specify: Yes.</t>
            </list></t>
          </list></t>    
 
          <t>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.</t>

          <figure>
            <artwork><![CDATA[
{
   "generic-metadata-type": "MI.FallbackTarget",
   "generic-metadata-value":
    {
       "host": "fallback-a.service123.ucdn.example"
    }
}
         ]]></artwork>
          </figure> 
      </section>

      
    <section anchor="IANA" title="IANA Considerations">

      <section anchor="IANA.payload" title="CDNI Payload Types">

        <t>This document requests the registration of the following CDNI Payload Types 
           under the IANA CDNI Payload Type registry defined in <xref target="RFC7736"/>:</t>

        <texttable>
          <ttcol align="left">Payload Type</ttcol>
          <ttcol align="left">Specification</ttcol>

          <c>FCI.RedirectTarget</c>
          <c>RFCthis</c>
          
          <c>MI.FallbackTarget</c>
          <c>RFCthis</c>
          
        </texttable>

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

        
        
        <section anchor="IANA.payload.RedirectTarget" title="CDNI FCI RedirectTarget Payload Type">
          <t>Purpose: The purpose of this payload type is to
             distinguish RedirectTarget FCI objects</t>
          <t>Interface: FCI</t>
          <t>Encoding: see <xref target="redirect-target-capability"/></t>
        </section>
        <section anchor="IANA.payload.FallbackTarget" title="CDNI MI FallbackTarget Payload Type">
          <t>Purpose: The purpose of this payload type is to
             distinguish FallbackTarget MI objects (and any associated capability advertisement)</t>
          <t>Interface: MI/FCI</t>
          <t>Encoding: see <xref target="fallback-target-metadata"/></t>
        </section>

       </section>
    </section>

    <section anchor="Security" title="Security Considerations">
      <t>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 considerations as 
         defined in <xref target="RFC8006"/> and <xref target="RFC8008"/> respectively.</t>
    </section>

    <section anchor="Acknowledgements" title="Acknowledgements">
      <t>TBD.</t>
    </section>
    
    <section anchor="Contributors" title="Contributors">
      <t>TBD.</t>
    </section>


  </middle>

  <back>
    <references title="Normative References">

      <?rfc include="reference.RFC.1034" ?>
      
      <?rfc include="reference.RFC.2119" ?>
                       
      <?rfc include="reference.RFC.3986" ?>

      <?rfc include="reference.RFC.7231" ?>
                       
      <?rfc include="reference.RFC.8006" ?>

      <?rfc include="reference.RFC.8007" ?>

      <?rfc include="reference.RFC.8008" ?>
          
    </references>

    <references title="Informative References">
      <?rfc include="reference.RFC.6707" ?>
      
      <?rfc include="reference.RFC.7336" ?>   
           
      <?rfc include="reference.RFC.7736" ?>

      <?rfc include="reference.RFC.7871" ?>
                                              

    </references>
  </back>
</rfc>
