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<?rfc tocdepth="4"?>
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<rfc category="std" docName="draft-ietf-cdni-request-routing-extensions-03" 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 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 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.</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 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.</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 used globally for all the hosts of the uCDN. 
      </t>
      <t>
         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.
      </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 make 
         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 the value for 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>
      <section anchor="redirect-target-capability-properties" title="Properties of Redirect Target Capability Object">
         <t>The Redirect Target capability object consists of the following properties:</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 a 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 a 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>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.
         </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": {
              "host": "us-east1.dcdn.com",
              "path-prefix": "/cache/1/",
              "include-redirecting-host": true          
          }
      },
      "footprints": [
          <Footprint objects>
      ]
    }
  ]
}
         ]]></artwork>
         </figure>
      </section> 
      <section anchor="dns-target" title="DnsTarget">
         <t>The DnsTarget object gives the target address for the DNS response to delegate 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 SHOULD NOT include a port number and, in case a port number is present,
                   the uCDN MUST ignore it.</t>

               <t>Mandatory-to-Specify: Yes.</t>
            </list></t>
         </list></t>
         <t>The following is an example of DnsTarget object:</t>
         <figure>
            <artwork><![CDATA[
 {
    "host": "service123.ucdn.example.dcdn.com"
 }
         ]]></artwork>
         </figure>
         <t>The following is an 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 necessary information to construct the target Location URI for HTTP redirection.</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.
                  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.</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 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 <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 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 
         or a hostname 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/or the uCDN hostname from the redirect URL that may have been used to 
         request the content from the dCDN.</t>

      <section anchor="fallback-target-metadata-properties" title="Properties Fallback Target Address Metadata Object">
         <t>The MI.FallbackTarget Metadata object consists of the following single property:</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 SHOULD NOT include a port number and,
                  in case a port number is present, the dCDN MUST ignore it.</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>

      
    <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 Types" 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-properties"/></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-properties"/></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 and privacy considerations as
         defined in Section 8 of <xref target="RFC8006"/> and in Section 7 of <xref target="RFC8008"/> respectively. 
      </t> 
        <section anchor="Privacy" title="Confidentiality and Privacy">
          <t>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 <xref target="RFC8006"/>.
          </t> 
        </section>
    </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>
