CDNI SVA Request Routing ExtensionsQwilt6, Ha'harashHod HaSharon4524079Israel+972-72-2221647orif@qwilt.comVerizon13100 Columbia PikeSilver SpringMD20904USAsanjay.mishra@verizon.comThe 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 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 RFC 2119.This document defines objects needed for Open Caching request routing. For that purpose it
extends CDNI metadata and CDNI Footprint and Capabilities .
For consistency, this document follows the CDNI notation of uCDN
(the commercial CDN) and dCDN (the ISP caching layer).The CDNI metadata interface is described in .The CDNI footprint and capability interface is described in .This document reuses the terminology defined in , , , and .Additionally, the following terms are used throughout this document
and are defined as follows:
SVA - Streaming Video Alliance.OC - SVA Open Caching.RR - Request Router.CP - Content Provider (video).Open Caching uses iterative request redirect as defined in .
In order for the uCDN to redirect to the dCDN it requires redirect target addresses.
The redirect targets are defined as part of the Footprint and Capabilities interface.Use casesFootprint: The dCDN may want to have different targets per footprint.
Note that a dCDN may spread across multiple geographies. This makes it
easier to route client request 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.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 addresses the uCDN should use in order
to redirect a client to the uCDN. Targets are represented as endpoint objects as defined in .Property: target-addressesDescription: Target addresses to which the uCDN can redirect the client, listed in order of priority.Type: Array of target-address objects (see )Mandatory-to-Specify: No. The dCDN can advertise the redirect targets to the uCDN statically, or by some other meansExample of Redirect Target Capability object (which contains two target-address objects) that describes which target addreses in the dCDN
the uCDN should use in order to redirect the client to the dCDN.A target-address object describes the address to be used by the uCDN when redirecting
a client to the dCDN.Endpoints within a target-address object MUST be treated as equivalent/equal.
A dCDN can specify an array of target-addresses, ordered by preference, within
a RedirectTargets capability object. Then, for each target-address object ranked by
preference, a dCDN can specify an array of endpoints that are equivalent
(e.g., a pool of servers that are not behind a load balancer).Property: endpointsDescription: Endpoint addresses to which the uCDN can redirect the client.
If multiple endpoints are specified, they are all equal, i.e., the list is not ordered by preference.Type: Array of Endpoint objects (see section 4.3.3 of ).Mandatory-to-Specify: Yes.Example of Target Address object (which contains two endpoint objects) that descibes which endpoint addreses in the dCDN
the uCDN should use in order to to redirect the client to the dCDN.Open Caching requires that the uCDN should provide fallback servers to the
dCDN to be used in cases where the dCDN cannot properly handle the request.
To avoid redirect loops, the fallback servers' addresses 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 server address. The fallback server is defined as a generic metadata object
(see section 3.2 of )Use casesFailover: A dCDN request router receives a request but has no caches
to which it can route the request to. This can happen in the case of
failures, or temporary network overload. In these cases, the router may
choose to redirect the request back to the uCDN fallback address.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 metadata object is used to indicate the server addresses the dCDN should use in order
to redirect a client back to the uCDN. Fallbacks addresses are represented as endpoint objects as defined in .Property: fallback-addressesDescription: Fallback Addresses to which the uCDN can redirect the client, listed in order of priority.Type: Array of fallback-address objects (see )Mandatory-to-Specify: No. The dCDN can advertise the redirect addresses to the uCDN statically, or by some other meansExample of MI.Fallback Metadata object (which contains two fallback-address objects) that describes which hosts addreses in the uCDN
the dCDN should use in order to redirect the client back to a fallback address at the uCDN.A fallback-address object describes the address to be used by the dCDN when redirecting
a client back to the dCDN due to failure, error, or other conditions in the dCDN.Endpoints within a fallback-address object MUST be treated as equivalent/equal.
A uCDN can specify an array of fallback-addresses, ordered by preference, within
a Fallback metadata object. Then, for each fallback-address object ranked by
preference, a uCDN can specify an array of endpoints that are equivalent
(e.g., a pool of servers that are not behind a load balancer).Property: endpointsDescription: Endpoint addresses to which the dCDN can redirect the client.
If multiple endpoints are specified, they are all equal, i.e., the list is not ordered by preference..Type: Array of Endpoint objects (see section 4.3.3 of )Mandatory-to-Specify: Yes.Property: protocolDescription: Network protocol to use when redirecting to this fallback server.Type: Protocol (see section 4.3.2 of )Mandatory-to-Specify: Yes.Example of Fallback Address object (which contains two endpoint objects) that descibes which endpoint addreses in the uCDN
the dCDN should use in order to to redirect the client to the uCDN.This document requests the registration of the following CDNI
Payload Types under the IANA CDNI Payload Type registry :Payload TypeSpecificationFCI.RedirectTargetesRFCthisMI.FallbackRFCthis[RFC Editor: Please replace RFCthis with the published RFC
number for this document.]Purpose: The purpose of this payload type is to
distinguish RedirectTargets FCI objectsInterface: FCIEncoding: see Purpose: The purpose of this payload type is to
distinguish Fallback MI objects (and any associated capability advertisement)Interface: MI/FCIEncoding: see 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 and respectively.TBD.TBD.