Internet Engineering Task Force (IETF) B. Niven-Jenkins, Ed.

Internet Engineering Task Force (IETF) B. Niven-Jenkins, Ed.
Request for Comments: 7975 Nokia
Category: Standards Track R. van Brandenburg, Ed.
ISSN: 2070-1721 TNO
October 2016

Request Routing Redirection Interface for
Content Delivery Network (CDN) Interconnection

Abstract

The Request Routing interface comprises (1) the asynchronous
advertisement of footprint and capabilities by a downstream Content
Delivery Network (CDN) that allows an upstream CDN to decide whether
to redirect particular user requests to that downstream CDN; and (2)
the synchronous operation of an upstream CDN requesting whether a
downstream CDN is prepared to accept a user request and of a
downstream CDN responding with how to actually redirect the user
request. This document describes an interface for the latter part,
i.e., the CDNI Request Routing Redirection interface.

Status of This Memo

This is an Internet Standards Track document.

This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.

Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7975.

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Copyright Notice

Copyright (c) 2016 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
(http://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 . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Interface Function and Operation Overview . . . . . . . . . . 4
4. HTTP-Based Interface for the Redirection Interface . . . . . 6
4.1. Information Passed in RI Requests and Responses . . . . . 8
4.2. JSON Encoding of RI Requests and Responses . . . . . . . 9
4.3. MIME Media Types Used by the RI Interface . . . . . . . . 11
4.4. DNS Redirection . . . . . . . . . . . . . . . . . . . . . 12
4.4.1. DNS Redirection Requests . . . . . . . . . . . . . . 12
4.4.2. DNS Redirection Responses . . . . . . . . . . . . . . 14
4.5. HTTP Redirection . . . . . . . . . . . . . . . . . . . . 17
4.5.1. HTTP Redirection Requests . . . . . . . . . . . . . . 17
4.5.2. HTTP Redirection Responses . . . . . . . . . . . . . 19
4.6. Cacheability and Scope of Responses . . . . . . . . . . . 22
4.7. Error Responses . . . . . . . . . . . . . . . . . . . . . 24
4.8. Loop Detection and Prevention . . . . . . . . . . . . . . 28
5. Security Considerations . . . . . . . . . . . . . . . . . . . 29
5.1. Authentication, Authorization, Confidentiality, and
Integrity Protection . . . . . . . . . . . . . . . . . . 29
5.2. Privacy . . . . . . . . . . . . . . . . . . . . . . . . . 30
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 31
6.1. CDNI Payload Type Parameter Registrations . . . . . . . . 31
6.1.1. CDNI RI Redirection Request Payload Type . . . . . . 31
6.1.2. CDNI RI Redirection Response Payload Type . . . . . . 31
6.2. RI Error Response Registry . . . . . . . . . . . . . . . 31
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 32
7.1. Normative References . . . . . . . . . . . . . . . . . . 32
7.2. Informative References . . . . . . . . . . . . . . . . . 34
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 34
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 35

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1. Introduction

A Content Delivery Network (CDN) is a system built on an existing IP
network that is used for large-scale content delivery, via
prefetching or dynamically caching content on its distributed
surrogates (caching servers). [RFC6707] describes the problem area
of interconnecting CDNs.

The CDNI Request Routing interface outlined in [RFC7336] is comprised
of:

1. The asynchronous advertisement of footprint and capabilities by a
downstream CDN (dCDN) that allows an upstream CDN (uCDN) to
decide whether to redirect particular user requests to that dCDN.

2. The synchronous operation of a uCDN requesting whether a dCDN is
prepared to accept a user request and of a dCDN responding with
how to actually redirect the user request.

This document describes an interface for the latter part, i.e., the
CDNI Request Routing Redirection interface (RI).

2. Terminology

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 [RFC2119].

This document reuses the terminology defined in [RFC6707].

The following additional terms are introduced by this document:

Application-Level Redirection: The act of using an application-
specific redirection mechanism for the request routing process of
a CDN. The Redirection Target (RT) is the result of a CDN's
routing decision at the time it receives a content request via an
application-specific protocol response. Examples of an
application-level redirection are HTTP 302 Redirection and Real
Time Messaging Protocol (RTMP) [RTMP] 302 Redirection.

DNS Redirection: The act of using DNS name resolution for the
request routing process of a CDN. In DNS Redirection, the DNS
name server of the CDN makes the routing decision based on a local
policy and selects one or more Redirection Targets (RTs) and
redirects the User Agent (UA) to the RT(s) by returning the
details of the RT(s) in response to the DNS query request from the
User Agent's DNS resolver.

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HTTP Redirection: The act of using an HTTP redirection response for
the request routing process of a CDN. The Redirection Target (RT)
is the result of the routing decision of a CDN at the time it
receives a content request via HTTP. HTTP Redirection is a
particular case of application-level redirection.

Redirection Target (RT): The endpoint to which the User Agent is
redirected. In CDNI, an 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.

3. Interface Function and Operation Overview

The main function of the CDNI Redirection interface (RI) is to allow
the request routing systems in interconnected CDNs to communicate to
facilitate the redirection of User Agent requests between
interconnected CDNs.

The detailed requirements for the Redirection interface and their
relative priorities are described in Section 5 of [RFC7337].

The User Agent will make a request to a request router in the uCDN
using one of either DNS or HTTP. The RI is used between the uCDN and
one or more dCDNs. The dCDN's RI response may contain a Redirection
Target with a type that is compatible with the protocol used between
the User Agent and uCDN request router. The dCDN has control over
the Redirection Target it provides. Depending on the returned
Redirection Target, the User Agent's request may be redirected to:

o The final surrogate, which may be in the dCDN that returned the RI
response to the uCDN or another CDN (if the dCDN delegates the
delivery to another CDN); or

o A request router (in the dCDN or another CDN), which may use a
different redirection protocol (DNS or HTTP) than the one included
in the RI request.

The Redirection interface operates between the request routing
systems of a pair of interconnected CDNs. To enable communication
over the Redirection interface, the uCDN needs to know the URI
(endpoint) in the dCDN to send CDNI request routing queries.

The Redirection interface URI may be statically preconfigured,
dynamically discovered via the CDNI Control interface, or discovered
via other means. However, such discovery mechanisms are not
specified in this document, as they are considered out of the scope
of the Redirection interface specification.

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The Redirection interface is only relevant in the case of Recursive
Request Redirection, as Iterative Request Redirection does not invoke
any interaction over the Redirection interface between interconnected
CDNs. Therefore, the scope of this document is limited to Recursive
Request Redirection.

In the case of Recursive Request Redirection, in order to perform
redirection of a request received from a User Agent, the uCDN queries
the dCDN so that the dCDN can select and provide a Redirection
Target. In cases where a uCDN has a choice of dCDNs, it is up to the
uCDN to decide (for example, via configured policies) which dCDN(s)
to query and in which order to query them. A number of strategies
are possible, including selecting a preferred dCDN based on local
policy, possibly falling back to querying an alternative dCDN(s) if
the first dCDN does not return a Redirection Target or otherwise
rejects the uCDN's RI request. A more complex strategy could be to
query multiple dCDNs in parallel before selecting one and using the
Redirection Target provided by that dCDN.

The uCDN->User Agent redirection protocols addressed in this document
are: DNS redirection and HTTP redirection. Other types of
application-level redirection will not be discussed further in this
document. However, the Redirection interface is designed to be
extensible and could be extended to support additional application-
level redirection protocols.

For both DNS and HTTP redirection, either HTTP or HTTPS could be used
to connect to the Redirection Target. When HTTPS is used to connect
to the uCDN, if the uCDN uses DNS redirection to identify the RT to
the User Agent, then the new target domain name may not match the
domain in the URL dereferenced to reach the uCDN; without operational
precautions, and in the absence of DNSSEC, this can make a legitimate
redirection look like a DNS-based attack to a User Agent and trigger
security warnings. When DNS-based redirection with HTTPS is used,
this specification assumes that any RT can complete the necessary
Transport Layer Security (TLS) handshake with the User Agent. Any
operational mechanisms this requires, e.g., private key distribution
to surrogates and request routers in dCDNs, are outside the scope of
this document.

This document also defines an RI loop prevention and detection
mechanism as part of the Redirection interface.

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4. HTTP-Based Interface for the Redirection Interface

This document defines a simple interface for the Redirection
interface based on HTTP [RFC7230], where the attributes of a User
Agent's requests are encapsulated along with any other data that can
aid the dCDN in processing the requests. The RI response
encapsulates the attributes of the RT(s) that the uCDN should return
to the User Agent (if it decides to utilize the dCDN for delivery)
along with the policy for how the response can be reused. The
examples of RI requests and responses below do not contain a complete
set of HTTP headers for brevity; only the pertinent HTTP headers are
shown.

The RI between the uCDN and dCDN uses the same HTTP interface to
encapsulate the attributes of both DNS and HTTP requests received
from User Agents, although the contents of the RI requests/responses
contain data specific to either DNS or HTTP redirection.

This approach has been chosen because it enables CDN operators to
only have to deploy a single interface for the RI between their CDNs,
regardless of the User Agent redirection method. In this way, from
an operational point of view, there is only one interface to monitor,
manage, develop troubleshooting tools for, etc.

In addition, having a single RI where the attributes of the User
Agent's DNS or HTTP request are encapsulated along with the other
data required for the dCDN to make a request routing decision, avoids
having to both 1) try to encapsulate or proxy DNS/HTTP/RTMP/
etc. requests and 2) find ways to somehow embed the additional CDNI
Request Routing Redirection interface properties/data within those
end-user DNS/HTTP/RTMP/etc. requests.

Finally, the RI is easily extendable to support other User Agent
request redirection methods (e.g., RTMP 302 redirection) by defining
additional protocol-specific keys for RI requests and responses along
with a specification about how to process them.

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The generic Recursive Request Redirection message flow between
Request Routing systems in a pair of interconnected CDNs is as
follows:

User Agent CDN B RR CDN A RR
|UA Request (DNS or HTTP) | |
|-------------------------------------------------->| (1)
| | |
| |HTTP POST to CDN B's RI |
| |URI encapsulating UA |
| |request attributes |
| |<------------------------| (2)
| | |
| |HTTP Response with body |
| |containing RT attributes |
| |of the protocol-specific |
| |response to return to UA |
| |------------------------>| (3)
| | |
| Protocol-specific response (redirection)|
|<--------------------------------------------------| (4)
| | |

Figure 1: Generic Recursive Request Redirection Message Flow

1. The User Agent sends its (DNS or HTTP) request to CDN A. The
Request Routing System of CDN A processes the request and,
through local policy, recognizes that the request is best served
by another CDN, specifically CDN B (or that CDN B may be one of a
number of candidate dCDNs it could use).

2. The Request Routing System of CDN A sends an HTTP POST to CDN B's
RI URI containing the attributes of the User Agent's request.

3. The Request Routing System of CDN B processes the RI request and,
assuming the request is well-formed, responds with an HTTP "200"
response with a message body containing the RT(s) to return to
the User Agent as well as parameters that indicate the properties
of the response (cacheability and scope).

4. The Request Routing System of CDN A sends a protocol-specific
response (containing the returned attributes) to the User Agent,
so that the User Agent's request will be redirected to the RT(s)
returned by CDN B.

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4.1. Information Passed in RI Requests and Responses

The information passed in RI requests splits into two basic
categories:

1. The attributes of the User Agent's request to the uCDN.

2. Properties/parameters that the uCDN can use to control the dCDN's
response or that can help the dCDN make its decision.

Generally, dCDNs can provide better routing decisions given
additional information about the content request, e.g., the URI of
the requested content or the User Agent's IP address or subnet. The
information required to base a routing decision on can be highly
dependent on the type of content delivered. A uCDN SHOULD only
include information that is absolutely necessary for delivering that
type of content. Cookies in particular are especially sensitive from
a security/privacy point of view and in general SHOULD NOT be
conveyed in the RI Requests to the dCDN. The information necessary
to be conveyed for a particular type of request is expected to be
conveyed out of band between the uCDN and dCDN. See Section 5.2 for
more detail on the privacy aspects of using RI Requests to convey
information about UA requests.

In order for the dCDN to determine whether it is capable of
delivering any requested content, it requires CDNI metadata related
to the content the User Agent is requesting. That metadata will
describe the content and any policies associated with it. It is
expected that the RI request contains sufficient information for the
Request Router in the dCDN to be able to retrieve the required CDNI
Metadata via the CDNI Metadata interface.

The information passed in RI responses splits into two basic
categories:

1. The attributes of the RT to return to the User Agent in the DNS
response or HTTP response.

2. Parameters/policies that indicate the properties of the response,
such as, whether it is cacheable, the scope of the response, etc.

In addition to details about how to redirect the User Agent, the dCDN
may wish to return additional policy information to the uCDN. For
example, the dCDN may wish to return a policy that expresses "this
response can be reused without requiring an RI request for 60 seconds
provided the User Agent's IP address is in the range 198.51.100.0 --
198.51.100.255".

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These additional policies split into two basic categories:

o Cacheability information signaled via the HTTP response headers of
the RI response (to reduce the number of subsequent RI requests
the uCDN needs to make).

o The scope of a cacheable response signaled in the HTTP response
body of the RI response, for example, whether the response applies
to a wider range of IP addresses than what was included in the RI
request.

The cacheability of the response is indicated using the standard HTTP
Cache-Control mechanisms.

4.2. JSON Encoding of RI Requests and Responses

The body of RI requests and responses is a JSON object [RFC7159] that
contains a dictionary of key:value pairs that MUST conform to
[RFC7493]. Senders MUST encode all (top-level object and sub-object)
keys specified in this document in lowercase. Receivers MUST ignore
any keys that are unknown or invalid.

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The following table defines the top-level keys and indicates whether
they are applicable to RI requests, RI responses, or both:

+----------+------------------+-------------------------------------+
| Key | Request/Response | Description |
+----------+------------------+-------------------------------------+
| dns | Both | The attributes of the UA's DNS |
| | | request or the attributes of the |
| | | RT(s) to return in a DNS response. |
| | | |
| http | Both | The attributes of the UA's HTTP |
| | | request or the attributes of the RT |
| | | to return in an HTTP response. |
| | | |
| scope | Response | The scope of the response (if it is |
| | | cacheable). For example, whether |
| | | the response applies to a wider |
| | | range of IP addresses than what was |
| | | included in the RI request. |
| | | |
| error | Response | Additional details if the response |
| | | is an error response. |
| | | |
| cdn-path | Both | A List of Strings. Contains a list |
| | | of the CDN Provider IDs of previous |
| | | CDNs that have participated in the |
| | | request routing for the associated |
| | | User Agent request. On RI requests, |
| | | it contains the list of previous |
| | | CDNs that this RI request has |
| | | passed through. On RI responses, it |
| | | contains the list of CDNs that were |
| | | involved in obtaining the final |
| | | redirection included in the RI |
| | | response. See Section 4.8. |
| | | |
| max-hops | Request | Integer specifying the maximum |
| | | number of hops (CDN Provider IDs) |
| | | this request is allowed to be |
| | | propagated along. This allows the |
| | | uCDN to coarsely constrain the |
| | | latency of the request routing |
| | | chain. |
+----------+------------------+-------------------------------------+

Table 1: Top-Level Keys in RI Requests/Responses

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A single request or response MUST contain only one of the dns or http
keys. Requests MUST contain a cdn-path key and responses MAY contain
a cdn-path key. If the max-hops key is not present, then there is no
limit on the number of CDN hops that the RI request can be propagated
along. If the first uCDN does not wish the RI request to be
propagated beyond the dCDN it is making the request to, then the uCDN
MUST set max-hops to 1.

The cdn-path MAY be reflected back in RI responses, although doing so
could expose information to the uCDN that a dCDN may not wish to
expose (for example, the existence of business relationships between
a dCDN and other CDNs).

If the cdn-path is reflected back in the RI response, it MUST contain
the value of cdn-path received in the associated RI request with the
final dCDN's CDN Provider ID appended. Transit CDNs MAY remove the
cdn-path from RI responses but MUST NOT modify the cdn-path in other
ways.

The presence of an error key within a response that also contains
either a dns or http key does not automatically indicate that the RI
request was unsuccessful as the error key MAY be used for
communicating additional (e.g., debugging) information. When a
response contains an error key as well as either a dns or http key,
the error-code SHOULD be 1xx (e.g., 100). See Section 4.7 for more
details about encoding error information in RI responses.

All implementations that support IPv4 addresses MUST support the
encoding specified by the 'IPv4address' rule in Section 3.2.2 of
[RFC3986]. Likewise, implementations that support IPv6 addresses
MUST support all IPv6 address formats specified in [RFC4291]. Server
implementations SHOULD use IPv6 address formats specified in
[RFC5952].

4.3. MIME Media Types Used by the RI Interface

RI requests MUST use a MIME media type of application/cdni as
specified in [RFC7736], with the Payload Type (ptype) parameter set
to 'redirection-request'.

RI responses MUST use a MIME media type of application/cdni as
specified in [RFC7736], with the Payload Type (ptype) parameter set
to 'redirection-response'.

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4.4. DNS Redirection

The following sections provide detailed descriptions of the
information that should be passed in RI requests and responses for
DNS redirection.

4.4.1. DNS Redirection Requests

For DNS-based redirection, the uCDN needs to pass the following
information to the dCDN in the RI request:

o The IP address of the DNS resolver that made the DNS request to
the uCDN.

o The type of DNS query made (usually either A or AAAA).

o The class of DNS query made (usually IN).

o The fully qualified domain name for which DNS redirection is being
requested.

o The IP address or prefix of the User Agent (if known to the uCDN).

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The preceding information is encoded as a set of key:value pairs
within the dns dictionary as follows:

+-------------+---------+-----------+-------------------------------+
| Key | Value | Mandatory | Description |
+-------------+---------+-----------+-------------------------------+
| resolver-ip | String | Yes | The IP address of the UA's |
| | | | DNS resolver. |
| | | | |
| qtype | String | Yes | The type of DNS query made by |
| | | | the UA's DNS resolvers in |
| | | | uppercase. The value of this |
| | | | field SHALL be set to either |
| | | | 'A' or 'AAAA'. |
| | | | |
| qclass | String | Yes | The class of DNS query made |
| | | | in uppercase (IN, etc.). |
| | | | |
| qname | String | Yes | The fully qualified domain |
| | | | name being queried. |
| | | | |
| c-subnet | String | No | The IP address (or prefix) of |
| | | | the UA in Classless Inter- |
| | | | Domain Routing (CIDR) format. |
| | | | |
| dns-only | Boolean | No | If True, then dCDN MUST only |
| | | | use DNS redirection and MUST |
| | | | include RTs to one or more |
| | | | surrogates in any successful |
| | | | RI response. CDNs MUST |
| | | | include the dns-only property |
| | | | set to True on any cascaded |
| | | | RI requests. Defaults to |
| | | | False. |
+-------------+---------+-----------+-------------------------------+

Table 2

An RI request for DNS-based redirection MUST include a dns
dictionary. This dns dictionary MUST contain the following keys:
resolver-ip, qtype, qclass, and qname; the value of each MUST be the
value of the appropriate part of the User Agent's DNS query/request.
For internationalized domain names containing non-ASCII characters,
the value of the qname field MUST be the ASCII-compatible encoded
(ACE) representation (A-label) of the domain name [RFC5890].

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An example RI request (uCDN->dCDN) for DNS-based redirection is as
follows:

POST /dcdn/ri HTTP/1.1
Host: rr1.dcdn.example.net
Content-Type: application/cdni; ptype=redirection-request
Accept: application/cdni; ptype=redirection-response

{
"dns" : {
"resolver-ip" : "192.0.2.1",
"c-subnet" : "198.51.100.0/24",
"qtype" : "A",
"qclass" : "IN",
"qname" : "www.example.com"
},
"cdn-path": ["AS64496:0"],
"max-hops": 3
}

4.4.2. DNS Redirection Responses

For a successful DNS-based redirection, the dCDN needs to return one
of the following to the uCDN in the RI response:

o The IP address(es) of (or the CNAME of) RTs that are dCDN
surrogates (if the dCDN is performing DNS-based redirection
directly to a surrogate); or

o The IP address(es) of (or the CNAME of) RTs that are Request
Routers (if the dCDN will perform request redirection itself). A
dCDN MUST NOT return an RT that is a Request Router if the dns-
only key is set to True in the RI request.

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The preceding information is encoded as a set of key:value pairs
within the dns dictionary as follows:

+-------+-----------+-----------+-----------------------------------+
| Key | Value | Mandatory | Description |
+-------+-----------+-----------+-----------------------------------+
| rcode | Integer | Yes | DNS response code (see |
| | | | [RFC6895]). |
| | | | |
| name | String | Yes | The fully qualified domain name |
| | | | the response relates to. |
| | | | |
| a | List of | No | Set of IPv4 Addresses of RT(s). |
| | String | | |
| | | | |
| aaaa | List of | No | Set of IPv6 Addresses of RT(s). |
| | String | | |
| | | | |
| cname | List of | No | Set of fully qualified domain |
| | String | | names of RT(s). |
| | | | |
| ttl | Integer | No | TTL in seconds of DNS response. |
| | | | Default is 0. |
+-------+-----------+-----------+-----------------------------------+

Table 3

A successful RI response for DNS-based redirection MUST include a dns
dictionary and MAY include an error dictionary (see Section 4.7). An
unsuccessful RI response for DNS-based redirection MUST include an
error dictionary. If a dns dictionary is included in the RI
response, it MUST include the rcode and name keys and it MUST include
at least one of the following keys: a, aaaa, or cname. The dns
dictionary MAY include both a and aaaa keys. If the dns dictionary
contains a cname key, it MUST NOT contain either an a or aaaa key.
For internationalized domain names containing non-ASCII characters,
the value of the cname field MUST be the ACE representation (A-label)
of the domain name.

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An example of a successful RI response (dCDN->uCDN) for DNS-based
redirection with both a and aaaa keys is listed below:

HTTP/1.1 200 OK
Date: Mon, 06 Aug 2012 18:41:38 GMT
Content-Type: application/cdni; ptype=redirection-response

{
"dns" : {
"rcode" : 0,
"name" : "www.example.com",
"a" : ["203.0.113.200", "203.0.113.201", "203.0.113.202"],
"aaaa" : ["2001:DB8::C8", "2001:DB8::C9"],
"ttl" : 60
}
}

A further example of a successful RI response (dCDN->uCDN) for DNS-
based redirection is listed below, in this case with a cname key
containing the FQDN of the RT.

HTTP/1.1 200 OK
Date: Mon, 06 Aug 2012 18:41:38 GMT
Content-Type: application/cdni; ptype=redirection-response

{
"dns" : {
"rcode" : 0,
"name" : "www.example.com",
"cname" : ["rr1.dcdn.example"],
"ttl" : 20
}
}

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4.5. HTTP Redirection

The following sections provide detailed descriptions of the
information that should be passed in RI requests and responses for
HTTP redirection.

The dictionary keys used in HTTP Redirection requests and responses
use the following conventions for their prefixes:

o c- is prefixed to keys for information related to the Client (User
Agent).

o cs- is prefixed to keys for information passed by the Client (User
Agent) to the Server (uCDN).

o sc- is prefixed to keys for information to be passed by the Server
(uCDN) to the Client (User Agent).

4.5.1. HTTP Redirection Requests

For HTTP-based redirection, the uCDN needs to pass the following
information to the dCDN in the RI request:

o The IP address of the User Agent.

o The URI requested by the User Agent.

o The HTTP method requested by the User Agent.

o The HTTP version number requested by the User Agent.

The uCDN may also decide to pass the presence and value of particular
HTTP headers included in the User Agent request to the dCDN.

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The preceding information is encoded as a set of key:value pairs
within the http dictionary as follows:

+-------------------+--------+-----------+--------------------------+
| Key | Value | Mandatory | Description |
+-------------------+--------+-----------+--------------------------+
| c-ip | String | Yes | The IP address of the |
| | | | UA. |
| | | | |
| cs-uri | String | Yes | The Effective Request |
| | | | URI [RFC7230] requested |
| | | | by the UA. |
| | | | |
| cs-method | String | Yes | The method part of the |
| | | | request-line as defined |
| | | | in Section 3.1.1 of |
| | | | [RFC7230]. |
| | | | |
| cs-version | String | Yes | The HTTP-version part of |
| | | | the request-line as |
| | | | defined in Section 3.1.1 |
| | | | of [RFC7230]. |
| | | | |
| cs-(<headername>) | String | No | The field-value of the |
| | | | HTTP header field named |
| | | | <HeaderName> as a |
| | | | string, for example, |
| | | | cs-(cookie) would |
| | | | contain the value of the |
| | | | HTTP Cookie header from |
| | | | the UA request. |
+-------------------+--------+-----------+--------------------------+

Table 4

An RI request for HTTP-based redirection MUST include an http
dictionary. This http dictionary MUST contain the following keys:
c-ip, cs-method, cs-version, and cs-uri; the value of each MUST be
the value of the appropriate part of the User Agent's HTTP request.

The http dictionary of an RI request MUST contain a maximum of one
cs-(<headername>) key for each unique header field-name (HTTP header
field). <headername> MUST be identical to the equivalent HTTP header
field-name encoded in all lowercase.

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In the case where the User Agent request includes multiple HTTP
header fields with the same field-name, it is RECOMMENDED that the
uCDN combine these different HTTP headers into a single value
according to Section 3.2.2 of [RFC7230]. However, because of the
plurality of already defined HTTP header fields and the inconsistency
of some of these header fields concerning the combination mechanism
defined in RFC 7230, the uCDN MAY have to deviate from using the
combination mechanism where appropriate. For example, it might only
send the contents of the first occurrence of the HTTP Headers
instead.

An example RI request (uCDN->dCDN) for HTTP-based redirection is as
follows:

POST /dcdn/rrri HTTP/1.1
Host: rr1.dcdn.example.net
Content-Type: application/cdni; ptype=redirection-request
Accept: application/cdni; ptype=redirection-response

{
"http": {
"c-ip": "198.51.100.1",
"cs-uri": "http://www.example.com",
"cs-version": "HTTP/1.1",
"cs-method": "GET"
},
"cdn-path": ["AS64496:0"],
"max-hops": 3
}

4.5.2. HTTP Redirection Responses

For a successful HTTP-based redirection, the dCDN needs to return one
of the following to the uCDN in the RI response:

o A URI pointing to an RT that is the selected dCDN surrogate(s) (if
the dCDN is performing HTTP-based redirection directly to a
surrogate); or

o A URI pointing to an RT that is a Request Router (if the dCDN will
perform request redirection itself).

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The preceding information is encoded as a set of key:value pairs
within the http dictionary as follows:

+-------------------+---------+-----------+-------------------------+
| Key | Value | Mandatory | Description |
+-------------------+---------+-----------+-------------------------+
| sc-status | Integer | Yes | The status-code part of |
| | | | the status-line as |
| | | | defined in Section |
| | | | 3.1.2 of [RFC7230] to |
| | | | return to the UA |
| | | | (usually set to 302). |
| | | | |
| sc-version | String | Yes | The HTTP-version part |
| | | | of the status-line as |
| | | | defined in Section |
| | | | 3.1.2 of [RFC7230] to |
| | | | return to the UA. |
| | | | |
| sc-reason | String | Yes | The reason-phrase part |
| | | | of the status-line as |
| | | | defined in Section |
| | | | 3.1.2 of [RFC7230] to |
| | | | return to the UA. |
| | | | |
| cs-uri | String | Yes | The URI requested by |
| | | | the UA/client. |
| | | | |
| sc-(location) | String | Yes | The contents of the |
| | | | Location header to |
| | | | return to the UA (i.e., |
| | | | a URI pointing to the |
| | | | RT(s)). |
| | | | |
| sc-(<headername>) | String | No | The field-value of the |
| | | | HTTP header field named |
| | | | <HeaderName> to return |
| | | | to the UA. For example, |
| | | | sc-(expires) would |
| | | | contain the value of |
| | | | the HTTP Expires |
| | | | header. |
+-------------------+---------+-----------+-------------------------+

Table 5

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Note: The sc-(location) key in the preceding table is an example of
sc-(<headername>) that has been called out separately as its presence
is mandatory in RI responses.

A successful RI response for HTTP-based redirection MUST include an
http dictionary and MAY include an error dictionary (see
Section 4.7). An unsuccessful RI response for HTTP-based redirection
MUST include an error dictionary. If an http dictionary is included
in the RI response, it MUST include at least the following keys:
sc-status, sc-version, sc-reason, cs-uri, and sc-(location).

The http dictionary of an RI response MUST contain a maximum of one
sc-(<headername>) key for each unique header field-name (HTTP header
field). <headername> MUST be identical to the equivalent HTTP header
field-name encoded in all lowercase.

The uCDN MAY decide to not return, override, or alter any or all of
the HTTP headers defined by sc-(<headername>) keys before sending the
HTTP response to the UA. It should be noted that in some cases,
sending the HTTP Headers indicated by the dCDN transparently on to
the UA might result in, for the uCDN, undesired behavior. As an
example, the dCDN might include sc-(cache-control),
sc-(last-modified), and sc-(expires) keys in the http dictionary,
through which the dCDN may try to influence the cacheability of the
response by the UA. If the uCDN would pass these HTTP headers on to
the UA, this could mean that further requests from the uCDN would go
directly to the dCDN, bypassing the uCDN and any logging it may
perform on incoming requests. Therefore, the uCDN is recommended to
carefully consider which HTTP headers to pass on, and which to either
override or not pass on at all.

An example of a successful RI response (dCDN->uCDN) for HTTP-based
redirection is a follows:

HTTP/1.1 200 OK
Date: Mon, 06 Aug 2012 18:41:38 GMT
Content-Type: application/cdni; ptype=redirection-response

{
"http": {
"sc-status": 302,
"sc-version": "HTTP/1.1",
"sc-reason": "Found",
"cs-uri": "http://www.example.com"
"sc-(location)":
"http://sur1.dcdn.example/ucdn/example.com",
}
}

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4.6. Cacheability and Scope of Responses

RI responses may be cacheable. As long as a cached RI response is
not stale according to standard HTTP Cache-Control or other
applicable mechanisms, it may be reused by the uCDN in response to
User Agent requests without sending another RI request to the dCDN.

An RI response MUST NOT be reused unless the request from the User
Agent would generate an identical RI request to the dCDN as the one
that resulted in the cached RI response (except for the c-ip field
provided that the User Agent's c-ip is covered by the scope in the
original RI response, as elaborated upon below).

Additionally, although RI requests only encode a single User Agent
request to be redirected, there may be cases where a dCDN wishes to
indicate to the uCDN that the RI response can be reused for other
User Agent requests without the uCDN having to make another request
via the RI. For example, a dCDN may know that it will always select
the same surrogates for a given set of User Agent IP addresses and in
order to reduce request volume across the RI or to remove the
additional latency associated with an RI request, the dCDN may wish
to indicate that set of User Agent IP addresses to the uCDN in the
initial RI response. This is achieved by including an optional scope
dictionary in the RI response.

Scope is encoded as a set of key:value pairs within the scope
dictionary as follows:

+---------+--------+-----------+------------------------------------+
| Key | Value | Mandatory | Description |
+---------+--------+-----------+------------------------------------+
| iprange | List | No | A List of IP subnets in CIDR |
| | of | | notation that this RI response can |
| | String | | be reused for, provided the RI |
| | | | response is still considered |
| | | | fresh. |
+---------+--------+-----------+------------------------------------+

Table 6

If a uCDN has multiple cached responses with overlapping scopes and a
UA request comes in for which the User Agent's IP matches with the IP
subnets in multiple of these cached responses, the uCDN SHOULD use
the most recent cached response when determining the appropriate RI
response to use.

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The following is an example of a DNS redirection response from
Section 4.4.2 that is cacheable by the uCDN for 30 seconds and can be
returned to any User Agent with an IPv4 address in 198.51.100.0/24.

HTTP/1.1 200 OK
Date: Mon, 06 Aug 2012 18:41:38 GMT
Content-Type: application/cdni; ptype=redirection-response
Cache-Control: public, max-age=30

{
"dns" : {
"rcode" : 0,
"name" : "www.example.com",
"a" : ["203.0.113.200", "203.0.113.201"],
"aaaa" : ["2001:DB8::C8", "2001:DB8::C9"],
"ttl" : 60
}
"scope" : {
"iprange" : ["198.51.100.0/24"]
}
}

The following is an example of an HTTP redirection response from
Section 4.5.2 that is cacheable by the uCDN for 60 seconds and can be
returned to any User Agent with an IPv4 address in 198.51.100.0/24.

Note: The response to the UA is only valid for 30 seconds, whereas
the uCDN can cache the RI response for 60 seconds.

HTTP/1.1 200 OK
Date: Mon, 06 Aug 2012 18:41:38 GMT
Content-Type: application/cdni; ptype=redirection-response
Cache-Control: public, max-age=60

{
"http": {
"sc-status": 302,
"cs-uri": "http://www.example.com"
"sc-(location)":
"http://sur1.dcdn.example/ucdn/example.com",
"sc-(cache-control)" : "public, max-age=30"
}
"scope" : {
"iprange" : ["198.51.100.0/24"]
}
}

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4.7. Error Responses

From a uCDN perspective, there are two types of errors that can be
the result of the transmission of an RI request to a dCDN:

1. An HTTP protocol error signaled via an HTTP status code,
indicating a problem with the reception or parsing of the RI
request or the generation of the RI response by the dCDN, and

2. An RI-level error specified in an RI response message.

This section deals with the latter type. The former type is outside
the scope of this document.

There are numerous reasons for a dCDN to be unable to return an
affirmative RI response to a uCDN. Reasons may include both dCDN
internal issues such as capacity problems, as well as reasons outside
the influence of the dCDN, such as a malformed RI request. To aid
with diagnosing the cause of errors, RI responses SHOULD include an
error dictionary to provide additional information to the uCDN as to
the reason/cause of the error. The intention behind the error
dictionary is to aid with either manual or automatic diagnosis of
issues. The resolution of such issues is outside the scope of this
document; this document does not specify any consequent actions a
uCDN should take upon receiving a particular error-code.

Error information (if present) is encoded as a set of key:value pairs
within a JSON-encoded error dictionary as follows:

+------------+---------+-----------+--------------------------------+
| Key | Value | Mandatory | Description |
+------------+---------+-----------+--------------------------------+
| error-code | Integer | Yes | A three-digit numeric code |
| | | | defined by the server to |
| | | | indicate the error(s) that |
| | | | occurred. |
| | | | |
| reason | String | No | A string providing further |
| | | | information related to the |
| | | | error. |
+------------+---------+-----------+--------------------------------+

Table 7

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The first digit of the error-code defines the class of error. There
are 5 classes of errors distinguished by the first digit of the
error-code:

1xx: Informational (no error): The response should not be
considered an error by the uCDN, which may proceed by redirecting
the UA according to the values in the RI response. The error-code
and accompanying description may be used for informational
purposes, e.g., for logging.

2xx: Reserved.

3xx: Reserved.

4xx: uCDN error: The dCDN cannot or will not process the request
due to something that is perceived to be a uCDN error, for
example, the RI request could not be parsed successfully by the
dCDN. The last two-digits may be used to more specifically
indicate the source of the problem.

5xx: dCDN error: Indicates that the dCDN is aware that it has
erred or is incapable of satisfying the RI request for some
reason, for example, the dCDN was able to parse the RI request but
encountered an error for some reason. Examples include the dCDN
not being able to retrieve the associated metadata or the dCDN
being out of capacity.

The following error-codes are defined and maintained by IANA (see
Section 6).

Error-codes with a "Reason" of "<reason>" do not have a defined value
for their 'reason'-key. Depending on the error-code semantics, the
value of this field may be determined dynamically.

+------+--------------+---------------------------------------------+
| Code | Reason | Description |
+------+--------------+---------------------------------------------+
| 100 | <reason> | Generic informational error-code meant for |
| | (see | carrying a human-readable string |
| | Description) | |
| | | |
| 400 | <reason> | Generic error-code for uCDN errors where |
| | (see | the dCDN cannot or will not process the |
| | Description) | request due to something that is perceived |
| | | to be a uCDN error. The reason field may |
| | | be used to provide more details about the |
| | | source of the error. |
| | | |

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| 500 | <reason> | Generic error-code for dCDN errors where |
| | (see | the dCDN is aware that it has erred or is |
| | Description) | incapable of satisfying the RI request for |
| | | some reason. The reason field may be used |
| | | to provide more details about the source of |
| | | the error. |
| | | |
| 501 | Unable to | The dCDN is unable to retrieve the metadata |
| | retrieve | associated with the content requested by |
| | metadata | the UA. This may indicate a configuration |
| | | error or that the content requested by the |
| | | UA does not exist. |
| | | |
| 502 | Loop | The dCDN detected a redirection loop (see |
| | detected | Section 4.8). |
| | | |
| 503 | Maximum hops | The dCDN detected the maximum number of |
| | exceeded | redirection hops exceeding max-hops (see |
| | | Section 4.8). |
| | | |
| 504 | Out of | The dCDN does not currently have sufficient |
| | capacity | capacity to handle the UA request. |
| | | |
| 505 | Delivery | The dCDN does not support the (set of) |
| | protocol not | delivery protocols indicated in the CDNI |
| | supported | Metadata of the content requested by the |
| | | UA. |
| | | |
| 506 | Redirection | The dCDN does not support the requested |
| | protocol not | redirection protocol. This error-code is |
| | supported | also used when the RI request has the dns- |
| | | only flag set to True and the dCDN is not |
| | | supported or is not prepared to return an |
| | | RT of a surrogate directly. |
+------+--------------+---------------------------------------------+

Table 8

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The following is an example of an unsuccessful RI response
(dCDN->uCDN) for a DNS-based User Agent request:

HTTP/1.1 500 Internal Server Error
Date: Mon, 06 Aug 2012 18:41:38 GMT
Content-Type: application/cdni; ptype=redirection-response
Cache-Control: private, no-cache

{
"error" : {
"error-code" : 504,
"description" : "Out of capacity"
}
}

The following is an example of a successful RI response (dCDN->uCDN)
for an HTTP-based User Agent request containing an error dictionary
for informational purposes:

HTTP/1.1 200 OK
Date: Mon, 06 Aug 2012 18:41:38 GMT
Content-Type: application/cdni; ptype=redirection-response
Cache-Control: private, no-cache

{
"http": {
"sc-status": 302,
"sc-version": "HTTP/1.1",
"sc-reason": "Found",
"cs-uri": "http://www.example.com"
"sc-(location)":
"http://sur1.dcdn.example/ucdn/example.com",
},
"error" : {
"error-code" : 100,
"description" :
"This is a human-readable message meant for debugging purposes"
}
}

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4.8. Loop Detection and Prevention

In order to prevent and detect RI request loops, each CDN MUST insert
its CDN Provider ID into the cdn-path key of every RI request it
originates or cascades. When receiving RI requests, a dCDN MUST
check the cdn-path and reject any RI requests that already contain
the dCDN's Provider ID in the cdn-path. Transit CDNs MUST NOT
propagate to any downstream CDNs if the number of CDN Provider IDs in
cdn-path (before adding its own Provider ID) is equal to or greater
than max-hops.

The CDN Provider ID uniquely identifies each CDN Provider during the
course of request routing redirection. It consists of the characters
AS followed by the CDN Provider's AS number, then a colon (':') and
an additional qualifier that is used to guarantee uniqueness in case
a particular AS has multiple independent CDNs deployed; for example,
"AS64496:0".

If a dCDN receives an RI request whose cdn-path already contains that
dCDN's Provider ID, the dCDN MUST send an RI error response that
SHOULD include an error-code of 502.

If a dCDN receives an RI request where the number of CDN Provider IDs
in cdn-path is greater than max-hops, the dCDN MUST send an RI error
response that SHOULD include an error-code of 503.

It should be noted that the loop detection and prevention mechanisms
described above only cover preventing and detecting loops within the
RI itself. Besides loops within the RI itself, there is also the
possibility of loops in the data plane; for example, if the IP
address(es) or URI(s) returned in RI responses do not resolve
directly to a surrogate in the final dCDN, there is the possibility
that a User Agent may be continuously redirected through a loop of
CDNs. The specification of solutions to address data-plane request
redirection loops between CDNs is outside of the scope of this
document.

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5. Security Considerations

Information passed over the RI could be considered personal or
sensitive, for example, RI requests contain parts of a User Agent's
original request and RI responses reveal information about the dCDN's
policy for which surrogates should serve which content/user
locations.

The RI interface also provides a mechanism whereby a uCDN could probe
a dCDN and infer the dCDN's edge topology by making repeated RI
requests for different content and/or UA IP addresses and correlating
the responses from the dCDN. Additionally, the ability for a dCDN to
indicate that an RI response applies more widely than the original
request (via the scope dictionary) may significantly reduce the
number of RI requests required to probe and infer the dCDN's edge
topology.

The same information could be obtained in the absence of the RI
interface, but it could be more difficult to gather as it would
require a distributed set of machines with a range of different IP
addresses, each making requests directly to the dCDN. However, the
RI facilitates easier collection of such information as it enables a
single client to query the dCDN for a redirection/surrogate selection
on behalf of any UA IP address.

5.1. Authentication, Authorization, Confidentiality, and Integrity
Protection

An implementation of the CDNI Redirection interface MUST support TLS
transport as per [RFC2818] and [RFC7230]. The use of TLS for
transport of the CDNI Redirection interface messages allows the dCDN
and uCDN to authenticate each other. Once they have mutually
authenticated each other, it allows:

o The dCDN and uCDN to authorize each other (to ensure they are
transmitting/receiving CDNI Redirection messages to/from an
authorized CDN);

o CDNI Redirection interface messages to be transmitted with
confidentiality; and

o The integrity of the CDNI Redirection interface messages to be
protected during the exchange.

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In an environment where any such protection is required, mutually
authenticated encrypted transport MUST be used to ensure
confidentiality of the redirection information; to do so, TLS MUST be
used (including authentication of the remote end) by the server side
(dCDN) and the client side (uCDN) of the CDNI Redirection interface.

When TLS is used, the general TLS usage guidance in [RFC7525] MUST be
followed.

5.2. Privacy

Information passed over the RI ought to be considered personal and
sensitive. In particular, parts of a User Agent's original request,
most notably the UA's IP address and requested URI, are transmitted
over the RI to the dCDN. The use of mutually authenticated TLS, as
described in the previous section, prevents any other party than the
authorized dCDN from gaining access to this information.

Regardless of whether the uCDN and dCDN use the RI, a successful
redirect from a uCDN to a dCDN will make that dCDN aware of the UA's
IP address. As such, the fact that this information is transmitted
across the RI does not allow the dCDN to learn new information. On
the other hand, if a uCDN uses the RI to check with multiple
candidate dCDNs, those candidates that do not end up getting
redirected to do obtain information regarding end-user IP addresses
and requested URIs that they would not have if the RI not been used.

While it is technically possible to mask some information in the RI
Request, such as the last bits of the UA IP address, it is important
to note that this will reduce the effectiveness of the RI in certain
cases. CDN deployments need to strike a balance between end-user
privacy and the features impacted by such masking. This balance is
likely to vary from one deployment to another. As an example, when
the UA and its DNS resolver is behind a Carrier-grade NAT, and the RI
is used to find an appropriate delivery node behind the same NAT, the
full IP address might be necessary. Another potential issue when
using IP anonymization is that it is no longer possible to correlate
an RI Request with a subsequent UA request.

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6. IANA Considerations

6.1. CDNI Payload Type Parameter Registrations

IANA has registered the following two new Payload Types in the
"Content Delivery Network Interconnection (CDNI) Parameters" registry
for use with the application/cdni MIME media type.

+----------------------+---------------+
| Payload Type | Specification |
+----------------------+---------------+
| redirection-request | RFC 7975 |
| | |
| redirection-response | RFC 7975 |
+----------------------+---------------+

Table 9

6.1.1. CDNI RI Redirection Request Payload Type

Purpose: The purpose of this payload type is to distinguish RI
request messages.

Interface: RI

Encoding: See Section 4.4.1 and Section 4.5.1

6.1.2. CDNI RI Redirection Response Payload Type

Purpose: The purpose of this payload type is to distinguish RI
response messages.

Interface: RI

Encoding: See Section 4.4.2 and Section 4.5.2

6.2. RI Error Response Registry

IANA has created a new "CDNI RI Error response code" subregistry
within the "Content Delivery Network Interconnection (CDNI)
Parameters" registry. The "CDNI RI Error response code" namespace
defines the valid values for the error-code key in RI error
responses. The CDNI RI Error response code MUST be a three-digit
integer.

Additions to the "RI Error response registry" will be made via
"Specification Required" as defined in [RFC5226].

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The Designated Expert will verify that new error-code registrations
do not duplicate existing error-code definitions (in name or
functionality), ensure that the new error-code is in accordance with
the error classes defined in Section 4.7 of this document, prevent
gratuitous additions to the namespace, and prevent any additions to
the namespace that would impair the interoperability of CDNI
implementations.

New registrations are required to provide the following information:

Code: A three-digit numeric error-code, in accordance with the
error classes defined in Section 4.7 of this document.

Reason: A string that provides further information related to the
error that will be included in the JSON error dictionary with the
'reason'-key. Depending on the error-code semantics, the value of
this field may be determined dynamically. In that case, the
registration should set this value to '<reason>' and define its
semantics in the description field.

Description: A brief description of the error-code semantics.

Specification: Reference to the specification that defines the
error-code in more detail.

The entries in Table 8 are registered by this document, with the
value of the 'Specification' field set to RFC 7975 (this document).

7. References

7.1. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://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,
<http://www.rfc-editor.org/info/rfc3986>.

[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, DOI 10.17487/RFC4291, February
2006, <http://www.rfc-editor.org/info/rfc4291>.

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RFC 7975 Request Routing Redirection October 2016

[RFC5952] Kawamura, S. and M. Kawashima, "A Recommendation for IPv6
Address Text Representation", RFC 5952,
DOI 10.17487/RFC5952, August 2010,
<http://www.rfc-editor.org/info/rfc5952>.

[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Message Syntax and Routing",
RFC 7230, DOI 10.17487/RFC7230, June 2014,
<http://www.rfc-editor.org/info/rfc7230>.

[RFC7159] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
2014, <http://www.rfc-editor.org/info/rfc7159>.

[RFC6895] Eastlake 3rd, D., "Domain Name System (DNS) IANA
Considerations", BCP 42, RFC 6895, DOI 10.17487/RFC6895,
April 2013, <http://www.rfc-editor.org/info/rfc6895>.

[RFC7493] Bray, T., Ed., "The I-JSON Message Format", RFC 7493,
DOI 10.17487/RFC7493, March 2015,
<http://www.rfc-editor.org/info/rfc7493>.

[RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre,
"Recommendations for Secure Use of Transport Layer
Security (TLS) and Datagram Transport Layer Security
(DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
2015, <http://www.rfc-editor.org/info/rfc7525>.

[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>.

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

[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818,
DOI 10.17487/RFC2818, May 2000,
<http://www.rfc-editor.org/info/rfc2818>.

[RFC5890] Klensin, J., "Internationalized Domain Names for
Applications (IDNA): Definitions and Document Framework",
RFC 5890, DOI 10.17487/RFC5890, August 2010,
<http://www.rfc-editor.org/info/rfc5890>.

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RFC 7975 Request Routing Redirection October 2016

[RTMP] Adobe Systems Incorporated, "Real-Time Messaging Protocol
(RTMP) specification", December 2012,
<http://www.adobe.com/go/spec_rtmp>.

7.2. Informative References

[RFC7337] Leung, K., Ed. and Y. Lee, Ed., "Content Distribution
Network Interconnection (CDNI) Requirements", RFC 7337,
DOI 10.17487/RFC7337, August 2014,
<http://www.rfc-editor.org/info/rfc7337>.

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

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

Acknowledgements

The authors would like to thank Taesang Choi, Francois Le Faucheur,
Matt Miller, Scott Wainner, and Kevin J. Ma for their valuable
comments and input to this document.

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RFC 7975 Request Routing Redirection October 2016

Contributors

The following persons have participated as co-authors to this
document:

Wang Danhua
Huawei
Email: [email protected]

He Xiaoyan
Huawei
Email: [email protected]

Ge Chen
China Telecom
Email: [email protected]

Ni Wei
China Mobile
Email: [email protected]

Yunfei Zhang
Email: [email protected]

Spencer Dawkins
Huawei
Email: [email protected]

Authors' Addresses

Ben Niven-Jenkins (editor)
Nokia
3 Ely Road
Milton, Cambridge CB24 6DD
United Kingdom

Email: [email protected]

Ray van Brandenburg (editor)
TNO
Anna van Buerenplein 1
The Hague 2595DA
The Netherlands

Phone: +31-88-866-7000
Email: [email protected]

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