Network Working Group K. Ma
Internet-Draft Azuki Systems, Inc.
Intended status: Standards Track October 7, 2011
Expires: April 9, 2012
Content Distribution Network Interconnection (CDNI) Metadata Interface
draft-ma-cdni-metadata-00
Abstract
Content publishers (CPs) often use multiple Content Delivery Networks
(CDNs) to deliver content to consumers. Though existing interactions
between CPs and individual CDNs are beyond the scope of CDN
interconnection (CDNI), it is important to understand the management
capabilities and features available with existing non-interconnected
multi-CDN deployments. Before migrating to CDNI, CPs must first
assess the suitability of CDNI as a replacement for their existing
non-interconnected multi-CDN deployments. CDN feature configuration
and capability advertisement and enforcement is likely to occur
through the CDNI metadata interface (MI). This document describes an
approach to implementing the CDNI MI through the use of an extensible
metadata model and a light-weight HTTP-based API.
Requirements Language
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 [RFC2119].
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 9, 2012.
Copyright Notice
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Copyright (c) 2011 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
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described in the Simplified BSD License.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5
1.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 5
2. CDNI Metadata Data Model . . . . . . . . . . . . . . . . . . . 6
2.1. Domain Table . . . . . . . . . . . . . . . . . . . . . . . 7
2.2. Hostname Table . . . . . . . . . . . . . . . . . . . . . . 7
2.3. Agent Table . . . . . . . . . . . . . . . . . . . . . . . 8
2.4. Metadata Table . . . . . . . . . . . . . . . . . . . . . . 9
2.4.1. Hierarchical Metadata . . . . . . . . . . . . . . . . 10
3. CDNI Metadata Protocol . . . . . . . . . . . . . . . . . . . . 11
3.1. Domain API . . . . . . . . . . . . . . . . . . . . . . . . 12
3.1.1. Domain Creation . . . . . . . . . . . . . . . . . . . 13
3.1.2. Domain Update . . . . . . . . . . . . . . . . . . . . 13
3.1.3. Domain Retrieval . . . . . . . . . . . . . . . . . . . 14
3.1.4. Domain Removal . . . . . . . . . . . . . . . . . . . . 14
3.1.5. Domain Errors . . . . . . . . . . . . . . . . . . . . 15
3.2. Agent API . . . . . . . . . . . . . . . . . . . . . . . . 15
3.2.1. Agent Creation . . . . . . . . . . . . . . . . . . . . 16
3.2.2. Agent Update . . . . . . . . . . . . . . . . . . . . . 16
3.2.3. Agent Retrieval . . . . . . . . . . . . . . . . . . . 16
3.2.4. Agent Removal . . . . . . . . . . . . . . . . . . . . 17
3.2.5. Agent Errors . . . . . . . . . . . . . . . . . . . . . 17
3.3. Metadata API . . . . . . . . . . . . . . . . . . . . . . . 18
3.3.1. Metadata Creation . . . . . . . . . . . . . . . . . . 18
3.3.2. Metadata Update . . . . . . . . . . . . . . . . . . . 20
3.3.3. Metadata Retrieval . . . . . . . . . . . . . . . . . . 21
3.3.4. Metadata Removal . . . . . . . . . . . . . . . . . . . 23
3.3.5. Metadata Errors . . . . . . . . . . . . . . . . . . . 24
4. Metadata Definitions . . . . . . . . . . . . . . . . . . . . . 24
4.1. Global Metadata . . . . . . . . . . . . . . . . . . . . . 24
4.2. Content Publisher Metadata . . . . . . . . . . . . . . . . 24
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25
6. Security Considerations . . . . . . . . . . . . . . . . . . . 25
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 25
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 25
8.1. Normative References . . . . . . . . . . . . . . . . . . . 25
8.2. Informative References . . . . . . . . . . . . . . . . . . 25
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 26
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1. Introduction
The use cases described in the CDNI use case document
[I-D.bertrand-cdni-use-cases] provide motivational use cases for CDN
interconnection (CDNI). They describe reasons and situations where
CDNI provides a benefit to CDN vendors as well as content service
providers (CSPs). Additional use cases exist which describe how CDNs
are used today, however, these use cases often involve specific
features (e.g., customized content transformations, content security,
client authentication and filtering, content acquisition optimization
and redundancy, etc.) which are beyond the scope of CDNI. Though the
features themselves are not relevant to CDNI, the ability to support
those features or enforce policies related to those features in a
generic and extensible manner should be considered when designing
CDNI interfaces. The ability to support feature parity with existing
deployment models (i.e., non-CDNI-based CDN federation) may help to
remove barriers to CDNI adoption.
Though certain interfaces are out of scope of CDNI, e.g.:
o upstream CDN (uCDN) configuration by the CP
o uCDN content acquisition
o uCDN content delivery
o downstream CDN (dCDN) content acquisition
o end user (EU) content acquisition
o third party workflow management
o third party request routing
An awareness of these interfaces and an understanding of the
restrictions which they may impose on CDNI request routing is useful
for understanding the needs of the CDNI metadata interface (MI). As
described in the "Dynamic CDNI Metadata Acquisition Example" section
in the CDNI framework document [I-D.davie-cdni-framework], upon
receiving a request routing interface (RRI) request, the MI MAY be
used to retrieve metadata that is "considered" before responding to
the RRI request. To that end, the MI MUST define a deterministic
method for handling metadata processing. Though the definition and
interpretation of any individual piece of metadata is beyond the
scope of CDNI, a well-defined method for how to respond to a RRI
request when any unknown metadata value is encountered MUST be
supported.
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This document describes a simple data model for representing CDNI
metadata and a simple protocol for creating and retrieving CDNI
metadata in an opaque manner. The term opaque, in this case, should
be understood to mean: without understanding the underlying meaning
or interpretation of the metadata being represented. The metadata
model and retrieval protocol SHOULD be completely independent of the
definition of individual metadata values. The metadata model and
retrieval protocol MUST also define default behaviors for dealing
with metadata processing errors. The document defines a list of
metadata which are likely applicable to a broad range of CDNI
deployments. The document also provides a separate list of metadata
which are likely to be desirable to content publishers (CPs). This
document is not intended to suggest that any additional interfaces or
requirements are needed beyond those already specified in the CDNI
requirements document [I-D.lefaucheur-cdni-requirements], nor is this
document intended to suggest that any out of scope interfaces or
content publisher feature functionality should be brought into scope.
The metadata examples provided are intended only to illustrate
possible features that interconnected CDNs may wish to support and
the extensibility of the metadata model to handle those situations.
1.1. Terminology
[Ed. insert terminology reference]
1.2. Abbreviations
o CDN: Content Distribution Network
o uCDN: Upstream Content Distribution Network
o dCDN: Downstream Content Distribution Network
o CDNI: Content Distribution Network Interconnection
o CP: Content Publisher
o CSP: Content Service Provider
o EU: End User
o NSP: Network Service Provider
o RRI: Request Routing Interface
o MI: Metadata Interface
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2. CDNI Metadata Data Model
The simple data model is shown in Figure 1 below. It includes a top
level Domain object which describes the site(s) to which metadata is
associated. The term site, in this case, should be understood to
mean a collection of related content assets access through a single
portal or Web-site. The Domain is described by one or more Hostnames
through which the site is accessed and which SHOULD be recognized
when processing content requests. The Domain is also associated with
zero or more opaque Metadata objects. The Metadata objects are each
associated with a URI within the Domain and accessible through any of
the Hostnames and accessed using URI prefix matching to allow for
hierarchical associations between individual Metadata and sets of
Metadata. Each Domain is also associated with one or more Agent
objects. Agents represent entities which require access to metadata
(e.g., CPs or dCDNs). An Agent is associated with each Metadata
entry allowing different Metadata values to be returned to different
Agents.
+----------+
| | 1
| Agent +---------------+
| | |
+----+-----+ |
| 1..* |
| |
| 1 | 1
+----+-----+ +----+-----+
| | 1 0..* | |
| Domain +----------+ Metadata |
| | | |
+----+-----+ +----------+
| 1
|
| 1..*
+----+-----+
| |
| Hostname |
| |
+----------+
Figure 1: CDNI Metadata Data Model
The following sections describe an example implementation of the
metadata scheme described above using a standard SQL database.
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2.1. Domain Table
The Domain object contains basic information related to the site
being described. The example shown contains a primary key index and
a unique name for the site. An OPTIONAL site description (e.g., a
textual description of the site and its content) and site provider
(e.g., the name of the CP or CSP which owns the content) information
is also included.
CREATE TABLE "domain" ("domain_id" serial primary key,
"name" character varying(255) NOT NULL,
"provider" character varying(255),
"description" character varying(4095));
CREATE UNIQUE INDEX index_domain ON domain (name);
The Domain is the central object for binding metadata. The example
Domain shown below highlights the descriptive nature of the Domain
object:
domain_id: 1
name: acme
provider: acme rocket-powered products, inc
description: fine purveyors of high quality anvils, rubber bands,
bird seed, and rocket powered footwear
2.2. Hostname Table
The Hostname object contains basic hostname information related to
the site being described. The example shown requires a primary key
index, a string containing the hostname, and a foreign key reference
to the domain to which this Hostname is associated. A uniqueness
constraint is imposed on hostname/domain_id pairs to prevent
duplicate Hostname entries for a given Domain.
CREATE TABLE "hostname" ("hostname_id" serial primary key,
"hostname" character varying(255) NOT NULL,
"domain_id" integer NOT NULL);
CREATE UNIQUE INDEX index_hostname ON hostname (hostname, domain_id);
Hostname Table Definition
The Hostname objects list the hostnames through which the Domain
content may be accessed. The example Hostnames shown below represent
two DNS addresses through which the site may be accessed:
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hostname_id: 1
hostname: wile.e.coyote.acme.com
domain_id: 1
hostname_id: 2
hostname: road.runner.acme.com
domain_id: 1
2.3. Agent Table
The Agent object contains basic information for authenticating
entities which require access to Metadata. The example shown
contains a primary key index, a string containing the username, a
string containing the password (possibly hashed or encrypted), a
boolean value for differentiating between full read/write access
(e.g., for CPs) and read only access (e.g., for dCDNs), and a foreign
key reference to the domain to which this Agent is associated. A
uniqueness constraint is imposed on username/domain_id pairs to
prevent duplicate Agent entries for a given Domain.
CREATE TABLE "agent" ("agent_id" serial primary key,
"username" character varying(255) NOT NULL,
"password" character varying(255) NOT NULL,
"read_only" boolean DEFAULT false NOT NULL,
"domain_id" integer NOT NULL);
CREATE UNIQUE INDEX index_agent ON agent (username, domain_id);
Hostname Table Definition
The Agent objects manage Metadata access rights. The example Agents
shown below represent a CP Agent with write privileges and a dCDN
Agent with read-only permissions:
agent_id: 1
username: acme_cp
password: xxx
read_only: false
domain_id: 1
agent_id: 2
username: acme_dcdn
password: yyy
read_only: true
domain_id: 1
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2.4. Metadata Table
The Metadata object contains the actual individual pieces of metadata
for the site being described. The example shown contains a primary
key index, a string containing the URI(s) to which the metadata
applies, a name/value pair of strings which represent the name and
value of the Metadata, respectively, as well as a boolean value
stating whether or not enforcement of the given Metadata is
mandatory. An OPTIONAL ttl value and timeout field are included to
support metadata invalidation. The table also contains a foreign key
reference to the Domain to which this Metadata is associated and a
foreign key reference to the Agent to whom this Metadata is intended.
A compound uniqueness constraint is also applied to each uri/name/
domain_id/agent_id tuple to prevent a given Metadata from being
ambiguously applied multiple times to the same URI in a given Domain
for a given Agent.
CREATE TABLE "metadata" ("metadata_id" serial primary key,
"uri" character varying(4095) NOT NULL,
"name" character varying(255) NOT NULL,
"value" character varying(4095) NOT NULL,
"mandatory" boolean DEFAULT false NOT NULL,
"ttl" integer DEFAULOT 0 NOT NULL,
"timeout" timestamp without time zone,
"domain_id" integer NOT NULL,
"agent_id" integer NOT NULL);
CREATE UNIQUE INDEX index_metadata ON metadata (uri, name,
domain_id, agent_id);
The name/value pair is represented as simple opaque strings. The MI
has no understanding of any inherent meaning for the Metadata names
or values. Metadata names SHOULD be properly defined and registered,
and any implied functionality SHOULD be agreed upon a priori by CDN
operators, however, these negotiations are beyond the scope of CDNI.
The intent of the mandatory boolean is to identify Metadata that MUST
be enforced by all CDNs. If a CDN is unable to understand or is
unable to comply with the Metadata, it MUST NOT deliver the content
being requests. For dCDNs, the mandatory flag defines how to respond
to RRI requests when unknown Metadata is encountered. If Metadata is
marked as mandatory, then the dCDN MUST NOT accept the RRI request if
it does not know how to process that piece of Metadata. If the MI
request resulted from a "recursive" RRI request, then the dCDN MUST
return an error to the uCDN; if the MI request resulted from an
"iterative" RRI request, then the dCDN MUST respond with a 403
Forbidden status code to the EU.
The OPTIONAL ttl value is provided to allow configuration of a
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Metadata TTLs. The ttl MUST be specified in seconds and the timeout
field SHOULD be populated by the local MI processor and used
internally, to prevent the need for clock synchronization between MI
processors.
The association of each Metadata to an Agent allows different Agents
to retrieve different Metadata values for a given URI in the given
Domain. This is intended to allow CDNs to separate upstream Metadata
from downstream Metadata (e.g., a uCDN content acquisition URL may
point to a CP origin, however the content acquisition URL that the
dCDN retrieves from the uCDN may point at a surrogate in the uCDN).
2.4.1. Hierarchical Metadata
In order to support hierarchical metadata, '/*' SHOULD be allowed as
the last part of the URI hierarchy, signifying the application of
this Metadata value to all URIs which match this URI prefix. If
multiple Metadata are defined with overlapping prefixes, the URI with
the longest prefix match MUST be used. The uniqueness constraint on
the uri/name/domain_id tuple should allow for unambiguous resolution
of Metadata priority.
Given the following three Metadata, the value of the color Metadata
object is defined four times within the same Domain but for different
URIs and Agents.
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metadata_id: 1
uri: /*
name: color
value: blue
mandatory: false
ttl: 0
domain_id: 1
agent_id: 2
metadata_id: 1
uri: /*
name: color
value: gold
mandatory: false
ttl: 0
domain_id: 1
agent_id: 1
metadata_id: 2
uri: /grass/*
name: color
value: brown
mandatory: false
ttl: 0
domain_id: 1
agent_id: 2
metadata_id: 3
uri: /grass/on/the/other/side/*
name: color
value: green
mandatory: false
ttl: 0
domain_id: 1
agent_id: 2
The default value for the color metadata (signified by the all
encompassing URI "/*") is blue for the dCDN Agent and gold for the CP
Agent. Alternate colors are associated with requests from the dCDN
Agent for URIs that begin with "/grass". By default /grass has a
color of brown, except when requesting "/grass/on/the/other/side/"
which is green.
3. CDNI Metadata Protocol
The Domain, Agent, and Metadata creation/retrieval protocols are
defined in the following sections. All use a simple HTTP-based
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approach. The protocol, in general, SHOULD be data format agnostic.
The examples shown herein use an XML representation for MI requests/
responses, however, other well-defined representations (e.g., JSON)
are also acceptable. The protocol shown provides an example of the
functionality required to support the data model described in Section
2, however, any protocol which allows for the creation, modification,
retrieval, and removal of Domains, Agents, and Metadata could also be
acceptable.
It is assumed that a well-known hostname to which MI requests should
be sent is configured through the CDNI bootstrap data. Bootstrap
information is sent through the CDNI control interface, as described
in the CDNI requirements document [I-D.lefaucheur-cdni-requirements].
This CDNI MI bootstrap data corresponds to the MI SEED information
described in the CDNI framework document [I-D.davie-cdni-framework].
The MI APIs described herein are intended to be serviced by the MI
running on that host. The actual entity which processes the requests
is inconsequential, as long as it has access to the metadata
database.
Domain and Agent configurations must exist prior to Metadata
creation/retrieval. Domains and Agents MAY be created as a part of
an off-line business negotiation process or as a part of the CDNI
bootstrapping process. Domains and Agents do not necessarily need to
be created dynamically using the APIs described below, however, the
APIs are included for completeness. When the Domain and Agent APIs
are used, access to the APIs SHOULD be secured using SSL with client
authentication as described in the Security Considerations section.
New content and Metadata MAY be uploaded at any time. The Metadata
API MUST support dynamic creation and modification of Metadata by
valid Agents. Though the Metadata API SHOULD also be secured using
SSL with client authentication as described in the Security
Considerations section, an additional Agent authentication mechanism
is REQUIRED to properly filter requests and results. In the examples
shown below, HTTP basic authentication is used for Agent
authentication, though other methods (e.g., HTTP digest
authentication or URL hashing) could also be used.
3.1. Domain API
Domain creation/update is distinguished from domain retrieval by the
HTTP method. Domain creation/update MUST use the POST method.
Domain retrieval MUST use the GET method. The Domain MUST be removed
if there are no Hostnames associated with the domain (i.e., removing
all the Hostnames from the Domain MUST force the removal of the
Domain itself, and all of its associated Agents and Metadata).
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All metadata MUST be associated with a Domain. A Domain is created/
modified/retrieved using the "/CDNI/MI/domain" API. The domain API
REQUIRES a single query string argument "domain" which specifies the
name of the Domain to be created/modified/retrieved.
A simple XML representation of the information provided to the domain
creation/update API or returned from the domain retrieval API is
shown below:
...
3.1.1. Domain Creation
The following example creates a new Domain "acme":
POST /CDNI/MI/domain?domain=acme HTTP/1.1
Host: host.mi.cdni.example.com
Accept: */*
Content-Length: 185
Content-Type: application/x-www-form-urlencoded
acme
acme
wec.acme.com
rr.acme.com
3.1.2. Domain Update
The following example updates the "acme" Domain:
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POST /CDNI/MI/domain?domain=acme HTTP/1.1
Host: host.mi.cdni.example.com
Accept: */*
Content-Length: 335
Content-Type: application/x-www-form-urlencoded
acme rocket-powered products, inc
fine purveyors of high quality anvils, rubber bands,
bird seed, and rocket powered footwear
wile.e.coyote.acme.com
road.runner.acme.com
3.1.3. Domain Retrieval
The following example retrieves the updated "acme" Domain
information:
GET /CDNI/MI/domain?domain=acme HTTP/1.1
Host: host.mi.cdni.example.com
Accept: */*
HTTP/1.1 200 OK
Content-Length: 335
Connection: close
Content-Type: text/xml
acme rocket-powered products, inc
fine purveyors of high quality anvils, rubber bands,
bird seed, and rocket powered footwear
wile.e.coyote.acme.com
road.runner.acme.com
The MI MAY support bulk retrieval of Domains through the use of a
comma separated list of Domain names in the domain query string
parameter.
3.1.4. Domain Removal
The following example removes the "acme" Domain by updating the
Domain to remove all Hostnames:
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POST /CDNI/MI/domain?domain=acme HTTP/1.1
Host: host.mi.cdni.example.com
Accept: */*
Content-Length: 34
Content-Type: application/x-www-form-urlencoded
3.1.5. Domain Errors
Any update or retrieval request with malformed XML SHOULD respond
with a 400 Bad Request status code. Ancillary unknown tags MAY be
ignored.
Any update or retrieval request for a Domain which does not exist
SHOULD respond with a 404 Not Found status code.
3.2. Agent API
Agent creation/update is distinguished from Agent retrieval by the
HTTP method. Agent creation/update MUST use the POST method. Agent
retrieval MUST use the GET method. The Agent MUST be removed if the
password field is empty (i.e., updating the password to be an empty
string MUST force removal of the entire Agent object and all of it's
associated Metadata).
All metadata MUST be associated with an Agent. An Agent is created/
modified/retrieved using the "/CDNI/MI/agent" API. The agent API
REQUIRES a single query string argument "domain" which specifies the
name of the Domain to which the Agent has access.
A simple XML representation of the information provided to the agent
creation/update API or returned from the agent retrieval API is shown
below:
...
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3.2.1. Agent Creation
The following example creates two new Agents "acme_cp" and
"acme_dcdn" for the "acme" Domain:
POST /CDNI/MI/agent?domain=acme HTTP/1.1
Host: host.mi.cdni.example.com
Accept: */*
Content-Length: 253
Content-Type: application/x-www-form-urlencoded
acme_cp
xxx
false
acme_dcdn
zzz
false
3.2.2. Agent Update
The following example updates the "acme_dcdn" Agent in the "acme"
Domain:
POST /CDNI/MI/agent?domain=acme HTTP/1.1
Host: host.mi.cdni.example.com
Accept: */*
Content-Length: 136
Content-Type: application/x-www-form-urlencoded
acme_dcdn
yyy
true
3.2.3. Agent Retrieval
The following example retrieves the updated Agent information for the
"acme" Domain:
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GET /CDNI/MI/agent?domain=acme HTTP/1.1
Host: host.mi.cdni.example.com
Accept: */*
HTTP/1.1 200 OK
Content-Length: 252
Connection: close
Content-Type: text/xml
acme_cp
xxx
false
acme_dcdn
yyy
true
3.2.4. Agent Removal
The following example removes the "acme_dcdn" Agent from the "acme"
Domain by setting the password to an empty string:
POST /CDNI/MI/agent?domain=acme HTTP/1.1
Host: host.mi.cdni.example.com
Accept: */*
Content-Length: 91
Content-Type: application/x-www-form-urlencoded
acme_dcdn
3.2.5. Agent Errors
Any update or retrieval request with malformed XML SHOULD respond
with a 400 Bad Request status code. Ancillary unknown tags MAY be
ignored.
Any update or retrieval requests for an Agent which does not exist
SHOULD respond with a 404 Not Found status code.
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3.3. Metadata API
Metadata creation/update is distinguished from domain retrieval by
the HTTP method. Metadata creation/update MUST use the POST method.
Metadata retrieval MUST use the GET method. Metadata MUST be removed
if the value field is empty (i.e., updating the value to be an empty
string MUST force removal of the entire Metadata entry).
The Metadata for a Domain is created/modified/retrieved using the
"/CDNI/MI/metadata/" API. The metadata API REQUIRES a single query
string argument "domain" which specifies the name of the Domain to
which the Metadata being created/modified/retrieved belongs. Two
additional OPTIONAL arguments MAY also be provided when retrieving
metadata: "name" which specifies the name of the metadata field to
create/modify/retrieve and "uri" which specifies a URI for which the
metadata must apply.
A simple XML representation of the information provided to the
metadata creation/update API or returned from the metadata retrieval
API is shown below:
...
3.3.1. Metadata Creation
The following example creates a new default Metadata "origin" for the
"acme_dcdn" and "acme_cp" Agents in the "acme" Domain, issued by the
"acme_cp" Agent:
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POST /CDNI/MI/metadata?domain=acme HTTP/1.1
Host: host.mi.cdni.example.com
Accept: */*
Authorization: Basic YWNtZV9jcDp4eHg=
Content-Length: 382
Content-Type: application/x-www-form-urlencoded
/*
origin
edge.ucdn.com
true
acme_dcdn
/*
origin
anvil.acme.com
true
acme_cp
The following example creates three new Metadata "color" for the
"acme_dcdn" and "acme_cp" Agents in the "acme" Domain, issued by the
"acme_cp" Agent:
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POST /CDNI/MI/metadata?domain=acme HTTP/1.1
Host: host.mi.cdni.example.com
Accept: */*
Authorization: Basic YWNtZV9jcDp4eHg=
Content-Length: 576
Content-Type: application/x-www-form-urlencoded
/grass/*
color
brown
false
acme_dcdn
/grass/on/the/other/side/*
color
green
true
acme_dcdn
/glasses/*
color
violet
false
acme_dcdn
3.3.2. Metadata Update
The following example updates the "color" Metadata for the
"/glasses/*" portion of the "acme" Domain and "acme_dcdn" Agent,
issued by the "acme_cp" Agent:
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POST /CDNI/MI/metadata?domain=acme HTTP/1.1
Host: host.mi.cdni.example.com
Accept: */*
Authorization: Basic YWNtZV9jcDp4eHg=
Content-Length: 202
Content-Type: application/x-www-form-urlencoded
/glasses/*
color
rose
true
acme_dcdn
3.3.3. Metadata Retrieval
The following example retrieves the Metadata for the URI "/grass/on/
this/side" in the "acme" Domain. The request was issued by and the
results are filtered for the "acme_dcdn" Agent:
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GET /CDNI/MI/domain?domain=acme&uri=/grass/on/this/side HTTP/1.1
Host: host.mi.cdni.example.com
Accept: */*
Authorization: Basic YWNtZV9kY2RuOnl5eQ==
HTTP/1.1 200 OK
Content-Length: 381
Connection: close
Content-Type: text/xml
/*
origin
edge.ucdn.com
true
acme_dcdn
/grass/*
color
brown
false
acme_dcdn
The following example retrieves all "color" Metadata for the "acme"
Domain. The request was issued by and the results are filtered for
the "acme_dcdn" Agent:
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GET /CDNI/MI/domain?domain=acme&name=color HTTP/1.1
Host: host.mi.cdni.example.com
Accept: */*
Authorization: Basic YWNtZV9kY2RuOnl5eQ==
HTTP/1.1 200 OK
Content-Length: 573
Connection: close
Content-Type: text/xml
/grass/*
color
brown
false
acme_dcdn
/grass/on/the/other/side/*
color
green
true
acme_dcdn
/glasses/*
color
rose
true
acme_dcdn
3.3.4. Metadata Removal
The following example removes the default "origin" Metadata for
the"acme_dcdn" Agent in the "acme" Domain by setting the value to an
empty string, issued by the "acme_cp" Agent:
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POST /CDNI/MI/metadata?domain=acme HTTP/1.1
Host: host.mi.cdni.example.com
Accept: */*
Authorization: Basic YWNtZV9jcDp4eHg=
Content-Length: 134
Content-Type: application/x-www-form-urlencoded
/*
origin
acme_dcdn
3.3.5. Metadata Errors
Any update or retrieval request with malformed XML SHOULD respond
with a 400 Bad Request status code. Ancillary unknown tags MAY be
ignored.
Any update or retrieval request for a uri/name/domain_id tuple which
does not exist SHOULD respond with a 404 Not Found status code.
Any request which lacks a valid Agent authorization MUST respond with
a 401 Unauthorized status code.
4. Metadata Definitions
This section defines an initial set of CDNI Metadata.
4.1. Global Metadata
This section defines a base set of Metadata which SHOULD be supported
by all CDNI implementations.
TBD.
4.2. Content Publisher Metadata
This section defines an OPTIONAL set of Metadata, useful to CP
deployments, which MAY be supported by CDNI implementations.
TBD.
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5. IANA Considerations
This memo includes no request to IANA.
6. Security Considerations
There are a number of security concerns associated with the MI.
Metadata may be used to influence CDNI request routing. Metadata may
describe content acquisition parameters or content security
restrictions. Altering Metadata or inhibiting Metadata discovery may
impact content distribution. Some MI concerns include:
o Intercepting and discarding Metadata requests to prevent content
acquisition may be used as a denial of service attack.
o Altering content acquisition Metadata to prevent content
acquisition may be used as a denial of service attack.
o Spoofing content security Metadata to disable delivery
restrictions may be used to circumvent rights management.
To combat these concerns, unauthorized access to the MI MUST be
prevented. The use of SSL with client authentication SHOULD be used
for all MI APIs. Deployments in controlled environments where
physical security and IP address white-listing is employed MAY choose
not to use SSL.
7. Acknowledgements
The authors would like to thank Daniel Biagini, Gilles Bertrand, and
Raj Nair for their helpful reviews and comments.
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
8.2. Informative References
[I-D.bertrand-cdni-use-cases]
Bertrand, G., Stephan, E., Watson, G., Burbridge, T.,
Eardley, P., and K. Ma, "Use Cases for Content Delivery
Network Interconnection draft-bertrand-cdni-use-cases-02",
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July 2011.
[I-D.davie-cdni-framework]
Davie, B., Ed. and L. Peterson, Ed., "Framework for CDN
Interconnection draft-davie-cdni-framework-00", July 2011.
[I-D.lefaucheur-cdni-requirements]
Leung, K., Lee, Y., Le Faucheur, F., Viveganandhan, M.,
and G. Watson, "Content Distribution Network
Interconnection (CDNI) Requirements
draft-lefaucheur-cdni-requirements-02", July 2011.
Author's Address
Kevin J. Ma
Azuki Systems, Inc.
43 Nagog Park
Acton, MA 01720
USA
Phone: +1 978-844-5100
Email: kevin.ma@azukisystems.com
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