Network Working Group B. Niven-Jenkins Internet-Draft R. Murray Intended status: Standards Track G. Watson Expires: January 10, 2013 Velocix (Alcatel-Lucent) M. Caulfield K. Leung Cisco Systems July 9, 2012 CDN Interconnect Metadata draft-cjlmw-cdni-metadata-00 Abstract The CDNI Metadata Interface enables interconnected CDNs to exchange content distribution metadata in order to enable content acquisition and delivery. The CDNI metadata associated with a piece of content provides a downstream CDN with sufficient information for the downstream CDN to service content requests on behalf of an upstream CDN. This document describes both the core set of CDNI metadata and the protocol for exchanging that metadata. 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 January 10, 2013. Copyright Notice Niven-Jenkins, et al. Expires January 10, 2013 [Page 1] Internet-Draft CDN Interconnect Metadata July 2012 Copyright (c) 2012 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 . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 2. Design Principles . . . . . . . . . . . . . . . . . . . . . . 5 3. CDNI Metadata Data Model . . . . . . . . . . . . . . . . . . . 5 3.1. HostIndex, HostMetdata & PathMetadata objects . . . . . . 6 3.2. Remaining CDNI Metadata objects . . . . . . . . . . . . . 9 3.3. Metadata Inheritance . . . . . . . . . . . . . . . . . . . 12 4. Encoding-Independent CDNI Metadata Object Descriptions . . . . 12 4.1. CDNI Metadata Data Object Descriptions . . . . . . . . . . 12 4.1.1. HostIndex . . . . . . . . . . . . . . . . . . . . . . 13 4.1.2. HostMatch . . . . . . . . . . . . . . . . . . . . . . 13 4.1.3. HostMetadata . . . . . . . . . . . . . . . . . . . . . 13 4.1.4. Acquisition . . . . . . . . . . . . . . . . . . . . . 14 4.1.5. Delivery . . . . . . . . . . . . . . . . . . . . . . . 14 4.1.6. PathMatch . . . . . . . . . . . . . . . . . . . . . . 15 4.1.7. PathMetadata . . . . . . . . . . . . . . . . . . . . . 15 4.1.8. ACL . . . . . . . . . . . . . . . . . . . . . . . . . 15 4.1.9. ACLRule . . . . . . . . . . . . . . . . . . . . . . . 16 4.1.10. TimeWindow . . . . . . . . . . . . . . . . . . . . . . 16 4.1.11. Location . . . . . . . . . . . . . . . . . . . . . . . 17 4.1.12. Source . . . . . . . . . . . . . . . . . . . . . . . . 17 4.1.13. Auth . . . . . . . . . . . . . . . . . . . . . . . . . 17 4.1.14. Link . . . . . . . . . . . . . . . . . . . . . . . . . 18 4.2. CDNI Metadata Simple Data Type Descriptions . . . . . . . 19 4.2.1. Protocol . . . . . . . . . . . . . . . . . . . . . . . 19 4.2.2. Endpoint . . . . . . . . . . . . . . . . . . . . . . . 19 4.2.3. IPRange . . . . . . . . . . . . . . . . . . . . . . . 19 4.2.4. Pattern . . . . . . . . . . . . . . . . . . . . . . . 20 4.2.5. PatternFlags . . . . . . . . . . . . . . . . . . . . . 20 4.2.6. URI . . . . . . . . . . . . . . . . . . . . . . . . . 20 4.2.7. Time . . . . . . . . . . . . . . . . . . . . . . . . . 20 5. CDNI Metadata interface . . . . . . . . . . . . . . . . . . . 21 Niven-Jenkins, et al. Expires January 10, 2013 [Page 2] Internet-Draft CDN Interconnect Metadata July 2012 5.1. Transport . . . . . . . . . . . . . . . . . . . . . . . . 21 5.2. Retrieval of CDNI Metadata resources . . . . . . . . . . . 22 5.3. Bootstrapping . . . . . . . . . . . . . . . . . . . . . . 23 5.4. Encoding . . . . . . . . . . . . . . . . . . . . . . . . . 23 5.4.1. MIME Media Types . . . . . . . . . . . . . . . . . . . 23 5.4.2. JSON Encoding of Objects . . . . . . . . . . . . . . . 24 5.4.2.1. JSON Example . . . . . . . . . . . . . . . . . . . 25 5.4.3. XML Encoding of Objects . . . . . . . . . . . . . . . 27 5.4.3.1. XML Example . . . . . . . . . . . . . . . . . . . 28 5.5. Extensibility . . . . . . . . . . . . . . . . . . . . . . 30 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 31 7. Security Considerations . . . . . . . . . . . . . . . . . . . 31 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 31 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 31 9.1. Normative References . . . . . . . . . . . . . . . . . . . 31 9.2. Informative References . . . . . . . . . . . . . . . . . . 31 Appendix A. Relationship to the CDNI Requirements . . . . . . . . 32 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 33 Niven-Jenkins, et al. Expires January 10, 2013 [Page 3] Internet-Draft CDN Interconnect Metadata July 2012 1. Introduction CDNI enables a downstream CDN to service content requests on behalf of an upstream CDN. In the simplest use case, a content request received by the downstream CDN provides sufficient information for sending a response. More complex use cases require additional context, i.e. metadata. The CDNI metadata associated with a piece of content (or with a set of contents) provides a downstream CDN with sufficient information for servicing content requests on behalf of an upstream CDN in accordance with the policies defined by the upstream CDN. The CDNI Metadata Interface is introduced by [I-D.ietf-cdni-problem-statement] along with three other interfaces that may be used to compose a CDNI solution (Control, Request Routing and Logging). [I-D.davie-cdni-framework] expands on the information provided in [I-D.ietf-cdni-problem-statement] and describes each interface, and the relationships between them, in more detail. The requirements for the CDNI metadata interface are specified in [I-D.ietf-cdni-requirements] This document focuses on the CDNI Metadata interface which enables a downstream CDN to obtain CDNI Metadata from an upstream CDN so that the downstream CDN can properly process and respond to: o Redirection Requests received over the CDNI Request Routing protocol. o Content Requests received directly from User Agents. Specifically this document proposes: o A data structure for mapping content requests to CDNI Metadata properties (Section 3). o An initial set of CDNI Metadata properties (Section 4.1 through Section 4.2). o A RESTful web service for the transfer of CDNI Metadata (Section 5). 1.1. Terminology This document reuses the terminology defined in [I-D.ietf-cdni-problem-statement]. Additionally, the following terms are used throughout this document and are defined as follows: o Object - a collection of properties Niven-Jenkins, et al. Expires January 10, 2013 [Page 4] Internet-Draft CDN Interconnect Metadata July 2012 o Property - a key / value pair where the key is a property name and the value is the property value (possibly an object) 2. Design Principles The proposed CDNI Metadata Interface aims to achieve the following design principles: 1. Cacheability of CDNI metadata objects 2. Deterministic mapping from content requests to CDNI metadata properties 3. Support for DNS redirection as well as application-specific redirection (for example HTTP redirection) 4. Minimal duplication of CDNI metadata 5. Leverage existing protocols Cacheability improves the latency of acquiring metadata and therefore improves the latency of serving content requests. The CDNI Metadata Interface uses HTTP to achieve cacheability. Deterministic mappings from content requests to metadata properties eliminates ambiguity and ensures that the same policies are applied consistently by all downstream CDNs. Support for both HTTP and DNS redirection ensures that the CDNI Metadata Interface can be used for HTTP and DNS redirection and also meets the same design principles for both HTTP and DNS based redirection schemes. Minimal duplication of CDNI metadata provides space efficiency on storage in the CDNs, on caches in the network, and across the network between CDNs. Leveraging existing protocols avoids reinventing common mechanisms such as data structure encoding (e.g. XML, JSON) and data transport (e.g. HTTP). 3. CDNI Metadata Data Model The CDNI Metadata Model describes a data structure for mapping content requests to metadata properties. Metadata properties describe how to acquire, authorize, and deliver content from a downstream CDN. The data model relies on the assumption that these metadata properties may be aggregated based on the authoritative hostname of the content and subsequently on the resource path of the content. The data model associates a set of CDNI Metadata properties Niven-Jenkins, et al. Expires January 10, 2013 [Page 5] Internet-Draft CDN Interconnect Metadata July 2012 with a Hostname to form a default set of metadata properties for content delivered for that Hostname. That default set of metadata properties can be overridden by properties that apply to specific paths within a URI. Different Hostnames and URI paths will contain different sets of CDNI Metadata properties in order to describe the required behaviour when a dCDN surrogate is processing User Agent requests for content on that Hostname or URI path. As a result of this structure, significant commonality may exist between the CDNI Metadata properties specified for different Hostnames, different URI paths within a Hostname and different URI paths on different Hostnames. For example the definition of which User Agent IP addresses should be treated as being grouped together into a single network or geographic location is likely to be common for a number of different Hostnames. Another example is that although a uCDN is likely to have several different policies configured to express geo-blocking rules, it is likely that a single geo-blocking policy would be applied to multiple Hostnames delivered through the CDN. In order to enable the CDNI Metadata for a given Hostname or URI Path to be decomposed into sets of CDNI Metadata properties that can be reused by multiple Hostnames and URI Paths the CDNI Metadata interface specified in this document splits the CDNI Metadata into a number of objects. Efficiency is improved by enabling a single CDNI Metadata object (that is shared across Hostname and/or URI paths) to be retrieved by a dCDN once, even if it is referenced by the CDNI Metadata of multiple Hostnames. Section 3.1 introduces a high level description of the HostIndex, HostMetadata and PathMetadata objects and describes the relationships between those objects. Section 3.2 introduces a high level description of the remaining CDNI Metadata objects and describes the relationships between those objects as well as the relationships of those objects to HostMetadata and PathMetadata objects. Section 4.1 describes the specific properties of each object in more detail. 3.1. HostIndex, HostMetdata & PathMetadata objects A HostIndex object contains a list of Hostnames that may be delegated to the downstream CDN. The HostIndex is the starting point for accessing the uCDN's CDNI Metadata data store. It enables surrogates in the dCDN to deterministically discover, on receipt of a User Agent request for content, which other CDNI Metadata objects it requires in Niven-Jenkins, et al. Expires January 10, 2013 [Page 6] Internet-Draft CDN Interconnect Metadata July 2012 order to deliver the requested content. The HostIndex links end-user facing Hostnames to HostMetadata objects, which contain (or reference) the default CDNI Metadata required to serve content for that Hostname. When looking up CDNI Metadata, the downstream CDN looks up the requested Hostname in the HostIndex, from there it can find HostMetadata which describes delivery rules for a Hostname and PathMetadata which may override those rules for given URI paths within the Hostname. As well as containing the default CDNI Metadata for the specified Hostname, HostMetadata and PathMetadata objects may also contain PathMatch objects which in turn contain PathMetadata objects. PathMatch objects override the CDNI Metadata in the HostMetadata object or one or more preceding PathMetadata objects with more specific CDNI Metadata that applies to content requests matching the pattern defined in that PathMatch object. For the purposes of retrieving CDNI Metadata all other required CDNI Metadata objects and their properties are discoverable from the appropriate HostMetadata, PathMatch and PathMetadata objects for the requested content. The relationships between the HostIndex, HostMatch, HostMetadata, PathMatch and PathMetadata objects are described in Figure 1. +---------+ +---------+ +------------+ |HostIndex+---->|HostMatch|---->|HostMetadata+----------------+ +---------+ +---------+ +------+-----+ | | | V V +---------+ ************************ +--->|PathMatch| *Other Metadata Objects* | +---------+ ************************ | | ^ | V | | +------------+ | +--|PathMetadata+----------------+ +------------+ Key: ----> = References Figure 1: Relationships between the HostIndex, HostMetadata & PathMetadata CDNI Metadata Objects The table below describes the HostIndex, HostMetadata and PathMetadata objects in more detail. Niven-Jenkins, et al. Expires January 10, 2013 [Page 7] Internet-Draft CDN Interconnect Metadata July 2012 +--------------+----------------------------------------------------+ | Data Object | Description | +--------------+----------------------------------------------------+ | HostIndex | A HostIndex object lists the Hostnames that an | | | upstream CDN can provide CDNI metadata for and the | | | URIs to use for retrieving that CDNI Metadata. | | | For example, if "example.com" is a content | | | provider, the HostIndex object may include an | | | entry for "example.com" with the URI of the | | | associated HostMetadata object. These hostnames | | | are contained inside a list of HostMatch objects. | | HostMatch | A HostMatch object defines a hostname to match | | | against a requested host, and contains or | | | references a HostMetadata object which contains | | | CDNI Metadata properties to be applied when a | | | content request matches against the hostname. | | HostMetadata | A HostMetadata object contains (or references) the | | | default CDNI Metadata properties for content | | | served from that hostname, i.e. the CDNI Metadata | | | properties for content requests that do not match | | | any of the PathMatch objects contained or | | | referenced by that HostMetadata object. For | | | example, a HostMetadata object may describe the | | | metadata properties which apply to "example.com" | | | and may contain PathMatches for | | | "example.com/movies/*" and "example.com/music/*" | | | which reference corresponding PathMetadata objects | | | that contain the CDNI Metadata properties for | | | those specific URI paths. | | PathMatch | A PathMatch object defines a pattern to match | | | against the requested path, and contains or | | | references a PathMetadata object which contains | | | (or references) the CDNI Metadata properties to be | | | applied when a content request matches against the | | | defined URI path pattern. | Niven-Jenkins, et al. Expires January 10, 2013 [Page 8] Internet-Draft CDN Interconnect Metadata July 2012 | PathMetadata | A PathMetadata object contains the CDNI Metadata | | | properties for content served with the associated | | | URI path (defined in a PathMatch object). A | | | PathMetadata object may also contain PathMatch | | | objects in order to recursively define more | | | specific URI paths that require different (e.g. | | | more specific) CDNI Metadata to this one. For | | | example, the PathMetadata object which applies to | | | "example.com/movies/*" may describe CDNI metadata | | | which apply to that resource path and may contain | | | a PathMatch object for "example.com/movies/hd/*" | | | which would reference the corresponding | | | PathMetadata object for the | | | "example.com/movies/hd/" path prefix. | +--------------+----------------------------------------------------+ Table 1: HostIndex, HostMetadata and PathMetadata CDNI Metadata Objects 3.2. Remaining CDNI Metadata objects The HostMetadata and PathMetadata objects contain or can reference other CDNI Metadata objects that contain properties which describe how User Agent requests for content should be processed, for example where to acquire the content, authorization rules that should be applied, delivery location restrictions and so on. The properties associated with the processing of User Agent requests fall into two categories, Delivery and Acquisition. Delivery properties, such as Location based restrictions, are contained or referenced within a Delivery object. Acquisition properties, such as which Origin Server to use to acquire the content, are contained or referenced within an Acquisition Object. Delivery and Acquisition objects contain or reference other CDNI Metadata objects to define the properties and rules which should be applied when processing requests for content. In some cases the rules that should be applied are complex but also likely to be reusable and repeated across many HostMetadata or PathMetadata objects. The relationships between the HostMetadata and PathMetadata objects and the other CDNI Metadata objects (Delivery object, Acquisition object, etc.) required for CDNI request routing and delivery are illustrated in Figure 2. Niven-Jenkins, et al. Expires January 10, 2013 [Page 9] Internet-Draft CDN Interconnect Metadata July 2012 +-------------+ +----------------+ +--------------+ +--> | Acquisition | -----> | Source | | HostMetadata | | +-------------+ +----------------+ | - or - | ---+ | PathMetadata | | +-------------+ +----------------+ +--------------+ +--> | Delivery | --+--> | TimeWindow ACL | +-------------+ | +----------------+ | | +----------------+ +--> | Location ACL* | | +----------------+ | | +----------------+ +--> | Auth | +----------------+ *example ACL +----------------+ +----------------+ | Location ACL | = | ACL | +----------------+ +----------------+ | v +----------------+ | ACL Rules | +----------------+ | v +----------------+ | Location | +----------------+ Key: ----> = References Figure 2: Relationships between HostMetadata and PathMetadata and the other CDNI Metadata Objects The table below describes the remaining CDNI Metadata objects that were not defined in Section 3.1. Niven-Jenkins, et al. Expires January 10, 2013 [Page 10] Internet-Draft CDN Interconnect Metadata July 2012 +-------------+-----------------------------------------------------+ | Data Object | Description | +-------------+-----------------------------------------------------+ | Acquisition | Container object for metadata that applies to | | | content acquisition. | | Delivery | Container object for metadata that applies to | | | content delivery. | | Source | Information needed by a dCDN to acquire content. | | | For example the host to contact, the protocol to | | | use for acquisition and any authentication and | | | authorization methods that should be used. | | ACL | Contains or references a list of ACLRules that are | | | used to define any delivery restrictions that must | | | be applied e.g. Location restrictions or Time | | | based restrictions. | | ACLRule | Contains or references a list of objects which | | | define to what the restrictions should be applied | | | e.g. an ACLRule may reference a Location Object if | | | a location based ACL is required. | | TimeWindow | Start and end time used to specify windows of | | | availability or unavailability for the content. | | Location | Geographic or network location identified by | | | country code, BGP AS number, or subnet to which | | | content may (or may not) be delivered. | | Auth | Method and credentials for authentication and | | | authorization including URI-signing, token-base, | | | etc. | +-------------+-----------------------------------------------------+ Table 2: Content Distribution Metadata Data Objects The relationships in Figure 1 and Figure 2 are summarised in Table 3 below and the properties of each object are described in Section 4.1. +--------------+----------------------------------------------------+ | Data Object | Objects it References | +--------------+----------------------------------------------------+ | HostIndex | 0 or more HostMetadata objects. | | HostMetadata | 0 or more PathMatch objects. 0 or 1 Delivery | | | objects. 0 or 1 Acquisition objects. | | PathMatch | 1 PathMetadata object. | | PathMetadata | 0 or more PathMatch objects. 0 or 1 Delivery | | | objects. 0 or 1 Acquisition objects. | | Acquisition | 0 or more Source objects. | | Delivery | 0 or more ACL objects. 0 or more Auth objects. | | ACL | 0 or more ACLRule objects. | Niven-Jenkins, et al. Expires January 10, 2013 [Page 11] Internet-Draft CDN Interconnect Metadata July 2012 | ACLRule | 0 or more Location objects or 0 or more TimeWindow | | | objects. | +--------------+----------------------------------------------------+ Table 3: Relationships between CDNI Metadata Objects 3.3. Metadata Inheritance In the data model, a HostMetadata object may contain (or reference) multiple PathMetadata objects. Each PathMetadata object may in turn contain (or reference) other PathMetadata objects. These relationships form a tree. The tree of HostMetadata objects and PathMetadata objects forms an inheritance tree. Each node in the tree inherits the property values set by its parent. In the tree, a child may override any property value which has been set by its parent. If a HostMetadata object sets the value of a property, that value may be overridden by a PathMetadata object (the child of the HostMetadata object). If a PathMetadata object contains (or references) other PathMetadata objects as children, then those children PathMetadata objects may override the property values set by the parent PathMetadata object. If a child node overrides the value of a list, then the entire list is replaced with the value set by the child node. If a child node overrides the value of an object, then the whole object is replaced with the value set by the child node. 4. Encoding-Independent CDNI Metadata Object Descriptions This section provides the definitions of each object type declared in Section 3. The definition of each object contains an unordered set of properties. The type of some properties is another CDNI Metadata object and in those cases the value of the property can be either an object of that type (the object is embedded) or a Link object that describes a URI and relationship that can be dereferenced to retrieve the CDNI Metadata object that should be used as the value of that property. 4.1. CDNI Metadata Data Object Descriptions Each of the sub-sections below describes the properties associated with the data objects defined in Table 2. Niven-Jenkins, et al. Expires January 10, 2013 [Page 12] Internet-Draft CDN Interconnect Metadata July 2012 4.1.1. HostIndex The HostIndex object is the entry point into the CDNI Metadata hierarchy. An incoming content request is matched against the list of hosts to find the HostMatch object which applies to the request. Property: hosts Description: List of HostMatch objects Type: List of HostMatch Mandatory: Yes. 4.1.2. HostMatch The HostMatch object contains a hostname to match against and a metadata object to apply if a match is found. Property: hostname Description: String to match against the requested host. Type: String Mandatory: Yes Property: hostmetadata Description: CDNI Metadata to apply when delivering content that matches this pattern. Type: HostMetadata Mandatory: Yes 4.1.3. HostMetadata The HostMetadata object contains both metadata that applies to content requests for a particular host and a list of pattern matches for finding more specific metadata based on the resource path in a content request. Property: acquisition Description: Container for content acquisition related metadata. Type: Acquisition Mandatory: No. No default. Property: delivery Description: Container for content delivery related metadata. Type: Delivery Mandatory: No. No default. Property: paths Description: Path specific rules. First match applies. Type: List of PathMatch Mandatory: No. Default apply the properties defined in this HostMetadata object to all paths. Niven-Jenkins, et al. Expires January 10, 2013 [Page 13] Internet-Draft CDN Interconnect Metadata July 2012 Property: hostname Description: The end-user facing Hostname for this HostMetadata object. Type: Hostname Mandatory: Yes. 4.1.4. Acquisition Metadata which provides the dCDN information about content acquisition e.g. how to contact an uCDN Surrogate or an Origin Server. The sources are not necessarily the actual Origin Servers operated by the CSP but might be a set of Surrogates in the uCDN. Property: sources Description: Sources from which the dCDN can acquire content. Type: List of Source Mandatory: No. Defaults to empty list. 4.1.5. Delivery Metadata related to content delivery, e.g. delivery restrictions or content authorization methods. Property: locations Description: Access control list which applies restrictions to delivery based on client location. Type: ACL Mandatory: No. Defaults is allow all locations. Property: times Description: Access control list which applies restrictions to delivery based on request time. Type: ACL Mandatory: No. Defaults is allow all times. Property: auth Description: Options for authenticating content requests. All options in the list are equally valid. Type: List of Auth Mandatory: No. Defaults is no auth. Property: protocol Description: The delivery protocol to be used for content requests that match this HostMetadata object. Type: protocol Mandatory: Yes. Property: active Description: Enable or disable delivery from this host. Type: boolean Niven-Jenkins, et al. Expires January 10, 2013 [Page 14] Internet-Draft CDN Interconnect Metadata July 2012 Mandatory: No. Default yes. 4.1.6. PathMatch The PathMatch object contains an expression to match against and a metadata object to apply if a match is found. Property: pattern Description: String to match against the requested path, i.e. against the [RFC3986] path-absolute. Type: Pattern Mandatory: Yes Property: patternflags Description: Flags to control the pattern match. Type: List of PatternFlags Mandatory: No. Default Case-sensitive infix matching. Property: pathmetadata Description: CDNI Metadata to apply when delivering content that matches this pattern. Type: PathMetadata Mandatory: Yes 4.1.7. PathMetadata A PathMetadata object contains the CDNI Metadata properties for content served with the associated URI path (defined in a PathMatch object). Note that if CDNI metadata is used as an input to CDNI request routing and DNS-based redirection is employed, then any metadata at the PathMetadata level or below will be inaccessible at request routing time. PathMetadata objects may contain any of the properties of a HostMetadata object with the following exceptions: o PathMetadata objects MUST NOT contain a hostname property. o PathMetadata objects MUST NOT contain a protocol property. o The presence of an sources property is OPTIONAL. 4.1.8. ACL An ACL object contains or references a list of ACLRule objects which define a set of restrictions to apply to content delivery e.g. Location restrictions. An ACL may reference or contain ACLRules referencing or containing Location or TimeWindow objects but not both. Niven-Jenkins, et al. Expires January 10, 2013 [Page 15] Internet-Draft CDN Interconnect Metadata July 2012 Property: aclrules Description: Type: List of ACLRule Mandatory: No. Default no rules. 4.1.9. ACLRule An ACLRule contains or references a list of either TimeWindow or Location objects. ACLRule objects are used to construct ACL to apply restrictions to content delivery. Note: Although both the allow and deny properties are optional, one and only one of them MUST be present in an ACLRule. An ACLRule must also only refer to one of Location or TimeWindow but not both and should only refer to the objects relevant to the ACL type as defined by Delivery Metadata i.e. a Delivery Metadata object with an ACL with relationship of LocationACL must not reference TimeWindow objects further down in the Metadata hierarchy. Property: allow Description: List of either Locations (Location ACL) or Time Windows (TimeWindow ACL) which must be allowed. Type: List of Location or TimeWindow Mandatory: No. Default implicit Allow. Property: deny Description: List of either Locations (Location ACL) or Time Windows (TimeWindow ACL) which must be denied. Type: List of Location or TimeWindow Mandatory: No. Default implicit Deny. 4.1.10. TimeWindow A TimeWindow object describes a time range which may be applied by an ACLRule, e.g. Start 09:00AM 01/01/2000 End 17:00PM 01/01/2000. Property: start Description: The start time of the window. Type: Time Mandatory: Yes Property: end Description: The end time of the window. Type: Time Mandatory: Yes Niven-Jenkins, et al. Expires January 10, 2013 [Page 16] Internet-Draft CDN Interconnect Metadata July 2012 4.1.11. Location A Location object describes a Location which may be applied by an ACLRule, e.g. a Location may be an IPv4 address range or a geographic location. Property: iprange Description: A set of IP Addresses. Type: List of IPRange. Mandatory: Yes [Ed: Location as specified above only supports the Class 1a names described in [I-D.jenkins-cdni-names]. Need to add support for Class 1b names to a later version.] 4.1.12. Source A Source object describes the Source which should be used by the dCDN for content acquisition, e.g. a Surrogate within the uCDN or an alternate Origin Server, the protocol to be used and any authentication method. Property: auth Description: Authentication method to use when requesting content from this source. Type: Auth Mandatory: No. Default is no authentication. Property: endpoints Description: Origins from which the dCDN can acquire content. Type: List of EndPoint Mandatory: Yes. Property: protocol Description: Protocol to use for content acquisition. Type: Protocol Mandatory: Yes. 4.1.13. Auth An Auth object defines authentication and authorization methods to be used during content delivery and content acquisition, e.g. methods such as tokenization and URL Signing. Property: type Description: A string containing the authentication type "url- signing", "url-token", "http-basic", or "http-digest". The type dictates which optional fields are present and valid in the rest of the object. The "url-signing" type refers to URL signing authentication. The "url-token" type refers to token- Niven-Jenkins, et al. Expires January 10, 2013 [Page 17] Internet-Draft CDN Interconnect Metadata July 2012 based authentication. The "basic" and "digest" types refer to HTTP Basic and Digest access authentication. Type: String Mandatory: Yes. Property: algo Description: A string containing the signature algorithm (e.g. "md5", "sha-1", etc.). Type: String Mandatory: Yes, if type is "url-signing". Property: symmetric Description: A boolean if true, URL signing uses symmetric keys, otherwise asymmetric. Type: boolean Mandatory: Yes, if type is "url-signing". Property: key Description: A hex-encoded number containing the public key for verifying signatures, only valid if "symmetric" field is set to false. Type: boolean Mandatory: Yes, if type is "url-signing". Property: username Description: A string containing the username for "basic" and "digest" types. Type: String Mandatory: Yes, if type is "basic" or "digest". Property: password Description: A string containing the password for "basic" and "digest" types. Type: String Mandatory: Yes, if type is "basic" or "digest". 4.1.14. Link A link object may be used in place of any of the objects described above. Links can be used to avoid duplication if the same metadata information is repeated within the metadata tree. When a link replaces an object, its href property is set to the URI of the resource, its rel property is set to the name of the property it is replacing, and its type property is set to the type of the object it is replacing. Property: href Description: The URI of the of the addressable object being referenced. Type: URI Mandatory: Yes Niven-Jenkins, et al. Expires January 10, 2013 [Page 18] Internet-Draft CDN Interconnect Metadata July 2012 Property: rel Description: The Relationship between the referring object and the object it is referencing. Type: String Mandatory: Yes Property: type Description: The type of the object being referenced. Type: String Mandatory: Yes 4.2. CDNI Metadata Simple Data Type Descriptions This section describes the simpler data types that are used for properties of CDNI Metadata objects. 4.2.1. Protocol This type only appears in Links. Links with this type are not machine readable but rather represent particular feature sets of a protocol defined in a specification and implemented in code. The URI contained in the link needs to be defined for each delivery protocol with an associated interoperable feature set. The following examples are illustrative: o http://url.cdni.ietf.example/protocol/delivery/http/rfcABCD o http://url.cdni.ietf.example/protocol/delivery/rtmp/rfcEFGH o http://url.vendorY.ietf.example/protocol/delivery/rtmp/releaseP.Q [Editor's Note: It may be more appropriate to use the 'tag' URI scheme [RFC4151] for these URIs.] 4.2.2. Endpoint A hostname (with optional port) or an IP address (with optional port). Note: Client implementations MUST support IPv4 addresses encoded as specified by the 'IPv4address' rule in Section 3.2.2 of [RFC3986] and MUST support all IPv6 address formats specified in [RFC4291]. Server implementations SHOULD use IPv6 address formats specified in [RFC5952]. 4.2.3. IPRange One of: Niven-Jenkins, et al. Expires January 10, 2013 [Page 19] Internet-Draft CDN Interconnect Metadata July 2012 o A range of consecutive IP addresses (IPv4 or IPv6) expressed as Address1-Address2 which does not have to be to power of two aligned, for example the range 192.0.2.1-192.0.2.10 is valid. The first Address in the range MUST be 'lower' than the final address in the range. o A valid IP subnet (IPv4 or IPv6) expressed using CIDR notation. o A single IP address (IPv4 or IPv6). Note: Client implementations MUST support IPv4 addresses encoded as specified by the 'IPv4address' rule in Section 3.2.2 of [RFC3986] and MUST support all IPv6 address formats specified in [RFC4291]. Server implementations SHOULD use IPv6 address formats specified in [RFC5952]. 4.2.4. Pattern A pattern for string matching paths. The string may contain the wildcards * and ?. o * matches any sequence of characters (including the empty string). o ? matches exactly one character. Escaping: The three literals \ , * and ? should be escaped as \\, \* and \? 4.2.5. PatternFlags A set of flags indicating how a pattern match is made. The flags are: o Case-insensitive - Perform a case insensitive match (absence indicates case-sensitive match). o Prefix - Match against the start of the string (absence indicates that a match may start anywhere in the string). o Suffix - Match against the end of the string (absence indicates that a match may end anywhere in the string). Absence of both Prefix and Suffix results in a match against any part of the string (infix). 4.2.6. URI A URI as specified in [RFC3986]. 4.2.7. Time A time value expressed in seconds since Unix epoch in the UTC timezone. Niven-Jenkins, et al. Expires January 10, 2013 [Page 20] Internet-Draft CDN Interconnect Metadata July 2012 5. CDNI Metadata interface This section specifies an interface to enable a Downstream CDN to retrieve CDNI Metadata objects from an Upstream CDN. The interface can be used by a Downstream CDN to retrieve CDNI Metadata objects either dynamically as required by the Downstream CDN to process received requests (for example in response to receiving a CDNI Request Routing request from an Upstream CDN or in response to receiving a request for content from a User Agent) or in advance of being required. The CDNI Metadata interface is built on the principles of RESTful web services. This means that requests and responses over the interface are built around the transfer of representations of hyperlinked resources. A resource in the context of the CDNI Metadata interface is any object in the Data Model (as described in Section 3 through Section 4.1). In the general case a CDNI Metadata server makes each instance of an addressable CDNI Metadata object available via a unique URI that returns a representation of that instance of that CDNI Metadata object. When an object needs to reference another addressable CDNI Metadata object (for example a HostIndex object referencing a HostMetadata object) it does so by including a link to the referenced object. CDNI Metadata servers are free to assign whatever structure they desire to the URIs for CDNI Metadata objects and CDNI Metadata clients MUST NOT make any assumptions regarding the structure of CDNI Metadata URIs or the mapping between CDNI Metadata objects and their associated URIs. Therefore any URIs present in the examples below are purely illustrative and are not intended impose a definitive structure on CDNI Metadata interface implementations. 5.1. Transport The CDNI Metadata interface uses HTTP as the underlying protocol transport. The HTTP Method in the request defines the operation the request would like to perform. Servers implementing the CDNI Metadata interface MUST support the HTTP GET and HEAD methods. The corresponding HTTP Response returns the status of the operation in the HTTP Status Code and returns the current representation of the resource (if appropriate) in the Response Body. HTTP Responses from servers implementing the CDNI Metadata interface that contain a Niven-Jenkins, et al. Expires January 10, 2013 [Page 21] Internet-Draft CDN Interconnect Metadata July 2012 response body SHOULD include an ETag to enable validation of cached versions of returned resources. The CDNI Metadata interface specified in this document is a read-only interface. Therefore support for other HTTP methods such as PUT, POST and DELETE etc. is not specified. Server implementations of this interface SHOULD reject all methods other than GET and HEAD. As the CDNI Metadata interface builds on top of HTTP, CDNI Metadata servers may make use of any HTTP feature when implementing the CDNI Metadata interface, for example a CDNI Metadata server may make use of HTTP's caching mechanisms to indicate that the returned response/ representation can be reused without re-contacting the CDNI Metadata server. 5.2. Retrieval of CDNI Metadata resources In the general case a CDNI Metadata server makes each instance of an addressable CDNI Metadata object available via a unique URI and therefore in order to retrieve CDNI Metadata, a CDNI Metadata client first makes a HTTP GET request for the URI of the HostIndex which provides the CDNI Metadata client with a list of Hosts (along with their public facing hostnames) that the upstream CDN may delegate to the downstream CDN. In order to retrieve the CDNI Metadata for a particular request the CDNI Metadata client processes the received HostIndex object and finds the corresponding HostMetadata entry (by matching the hostname in the request against the hostnames in the HostIndex). The CDNI metadata client then makes a GET request for the URI specified in the href key of that Host's entry in the HostIndex. In order to retrieve the most specific metadata for a particular request, the CDNI metadata client inspects the HostMetadata for references to more specific PathMetadata objects. If any PathMetadata match the request, the CDNI metadata client makes another GET request for the PathMetadata. Each PathMetadata object may also include references to yet more specific metadata. If this is the case, the CDNI metadata client continues requesting PathMetadata recursively. Where a downstream CDN is interconnected with multiple upstream CDNs, the downstream CDN must decide which upstream CDN's metadata should handle a particular User Agent request. In the case of where application level redirection (e.g. HTTP 302 redirects) is being used between CDNs, it is expected that the downstream CDN will be able to determine the upstream CDN that Niven-Jenkins, et al. Expires January 10, 2013 [Page 22] Internet-Draft CDN Interconnect Metadata July 2012 redirected a particular request from information contained in the received request (e.g. via the URI in case of HTTP redirection across CDNs). With knowledge of which upstream CDN routed the request, the downstream CDN can choose the correct metadata server. In the case of DNS redirection there is not sufficient information carried in the DNS request from User Agents to determine the upstream CDN that redirected a particular request and therefore downstream CDNs may have to apply local policy when deciding which upstream CDN's metadata to apply. 5.3. Bootstrapping The URI for the HostIndex object of a given upstream CDN needs to be either discovered by or configured in the downstream CDN. All other objects/resources are then discoverable from the HostIndex object by following the links in the HostIndex object and the referenced HostMetadata and PathMetadata objects. If the URI for the HostIndex object is not manually configured in the downstream CDN then the HostIndex URI could be discovered via the CDNI Control interface. An upstream CDN would advertise the URI of the HostIndex object to the downstream CDN via the CDNI Control Interface. 5.4. Encoding Object are resources that may be: o Addressable, where the object is a resource that may be retrieved or referenced via its own URI. o Embedded, where the object is contained (or inlined) within a property of an addressable object. In the descriptions of objects we use the term "X contains Y" to mean either Y is directly embedded in X or that Y is linked to by X. It is generally a deployment choice for the uCDN implementation to decide when and which CDNI Metadata objects to embed and which are separately addressable. 5.4.1. MIME Media Types All MIME types are prefixed with "application/cdni." The MIME type for each object matches the type name of that object as defined by this document.Table 4 lists a few examples of the MIME Media Type for each object (resource) that is retrievable through the CDNI Metadata interface. The MIME type suffix depends on the metadata encoding, either "+xml" or "+json". Niven-Jenkins, et al. Expires January 10, 2013 [Page 23] Internet-Draft CDN Interconnect Metadata July 2012 +--------------+-------------------------------+ | Data Object | MIME Media Type | +--------------+-------------------------------+ | HostIndex | application/cdni.HostIndex | | HostMatch | application/cdni.HostMatch | | HostMetadata | application/cdni.HostMetadata | | PathMatch | application/cdni.PathMatch | | PathMetadata | application/cdni.PathMetadata | +--------------+-------------------------------+ Table 4: MIME Media Types for CDNI Metadata resources See http://www.iana.org/assignments/media-types/index.html for reference. 5.4.2. JSON Encoding of Objects One possible encoding for a CDNI Metadata object is a JSON object containing a dictionary of (key,value) pairs where the keys are the property names and the values are the associated property values. The keys of the dictionary are the names of the properties associated with the object and are therefore dependent on the specific object being encoded (i.e. dependent on the MIME Media Type of the returned resource). Likewise, the values associated with each key are dependent on the specific object being encoded (i.e. dependent on the MIME Media Type of the returned resource). Dictionary keys in JSON are case sensitive and therefore any dictionary key defined by this document (for example the names of CDNI Metadata object properties) MUST always be represented in lowercase. In addition to the properties of the object, the following three additional keys defined below may be present in any object. Key: base Description: Provides a prefix for any relative URLs in the object. This is similar to the XML base tag [XML-BASE]. If absent, all URLs in the remainder of the document must be absolute URLs. Type: URI Mandatory: No Key: links Description: The links of this object to other addressable objects. Any property may be replaced by a link to an object with the same type as the property it replaces. Niven-Jenkins, et al. Expires January 10, 2013 [Page 24] Internet-Draft CDN Interconnect Metadata July 2012 Type: List of Link Mandatory: Yes 5.4.2.1. JSON Example A downstream CDN may request the HostIndex and receive the following object of type "application/cdni.HostIndex+json": { "host": [ { "hostname": "video.example.com", "links": [ { "rel": "hostmetadata", "type": "HostMetadata", "href": "http://metadata.ucdn.com/video" } ] }, { "hostname": "images.example.com", "links": [ { "rel": "hostmetadata", "type": "HostMetadata", "href": "http://metadata.ucdn.com/images" } ] } ] } If the incoming request has a Host header with "video.example.com" then the downstream CDN would fetch from the next metadata object from "http://metadata.ucdn.com/video" expecting a MIME type of "application/cdni.HostMetadata+json": { "hostname": "video.example.com", "acquisition": { "source": [ { "links": [{ "rel": "auth", "type": "Auth", "href": "http://metadata.ucdn.com/auth1234" }], Niven-Jenkins, et al. Expires January 10, 2013 [Page 25] Internet-Draft CDN Interconnect Metadata July 2012 "endpoint": "acq1.ucdn.com", "protocol": "ftp" }, { "links": [{ "rel": "auth", "type": "Auth", "href": "http://metadata.ucdn.com/auth1234" }], "endpoint": "acq2.ucdn.com", "protocol": "http" } ] }, "delivery": { "location": { "aclrule": { "deny": { "iprange": "192.168.0.0/16" } } }, "auth": { }, "protocol": "http", "active": "true" }, "path": [ { "pattern": "/videos/trailers/*", "patternflags": "prefix", "links": [{ "rel": "pathmetadata", "type": "PathMetadata", "href": "http://metadata.ucdn.com/videos/trailers" }] }, { "pattern": "/videos/movies/*", "patternflags": "prefix", "links": [{ "rel": "pathmetadata", "type": "PathMetadata", "href": "http://metadata.ucdn.com/videos/movies" }] } ] } Niven-Jenkins, et al. Expires January 10, 2013 [Page 26] Internet-Draft CDN Interconnect Metadata July 2012 Suppose the path of the requested resource matches the "/video/ movies/*" pattern, the next metadata requested would be for "http://metadata.ucdn.com/video/movies" with an expected type of "application/cdni.PathMetadata": { "delivery": { "auth": { } }, "path": { "pattern": "/videos/movies/hd/*", "patternflags": "prefix", "links": [{ "rel": "pathmetadata", "type": "PathMetadata", "href": "http://metadata.ucdn.com/videos/movies/hd" }] } } Finally, if the path of the requested resource also matches the "/videos/movies/hd/*" pattern, the downstream CDN would also fetch the following object from "http://metadata.ucdn.com/videos/movies/hd" with MIME type "application/cdni.PathMetadata": { "delivery": { "time": { "aclrule": { "allow": { "start": "1213948800", "end": "1327393200" } } } } } 5.4.3. XML Encoding of Objects Another possible encoding for a CDNI Metadata object is an XML document containing elements with tag names which match property names and values which match the associated property values. Tag names of elements are the names of the properties associated with the object and are therefore dependent on the specific object being Niven-Jenkins, et al. Expires January 10, 2013 [Page 27] Internet-Draft CDN Interconnect Metadata July 2012 encoded (i.e. dependent on the MIME Media Type of the returned resource). Likewise, the values associated with each element are dependent on the specific object being encoded (i.e. dependent on the MIME Media Type of the returned resource). Lists are encoded by repeating the singular form of a property name. For example the "hosts" property is a list of "HostMatch" objects. This list would be encoded as multiple "host" elements. Link objects are a special case. If a Link object replaces a property then a "link" element replaces the expected element. The properties of the Link object are encoded as XML attributes. The type attribute is set to the MIME type of the target object. The href attribute is set to the URI of the target object. The rel attribute is set to the name of the element being replaced. 5.4.3.1. XML Example A downstream CDN may request the HostIndex and receive the following object of type "application/cdni.HostIndex+json": video.example.com images.example.com If the incoming request has a Host header with "video.example.com" then the downstream CDN would fetch from the next metadata object from "http://metadata.ucdn.com/video" expecting a MIME type of "application/cdni.HostMetadata+json": Niven-Jenkins, et al. Expires January 10, 2013 [Page 28] Internet-Draft CDN Interconnect Metadata July 2012 video.example.com acq1.ucdn.com ftp acq2.ucdn.com http 192.168.0.0/16 http true /videos/trailers/* prefix /videos/movies/* prefix Suppose the path of the requested resource matches the "/video/ movies/*" pattern, the next metadata requested would be for "http://metadata.ucdn.com/video/movies" with an expected type of "application/cdni.PathMetadata": Niven-Jenkins, et al. Expires January 10, 2013 [Page 29] Internet-Draft CDN Interconnect Metadata July 2012 /videos/movies/hd/* prefix Finally, if the path of the requested resource also matches the "/videos/movies/hd/*" pattern, the downstream CDN would also fetch the following object from "http://metadata.ucdn.com/videos/movies/hd" with MIME type "application/cdni.PathMetadata": 5.5. Extensibility The set of metadata properties may be extended with proprietary and / or custom properties. New properties may be added to any existing object. The names of such properties MUST begin with an "x-" prefix. If a property is vendor specific, then "x-vendor-" SHOULD be used as the name prefix, where the "vendor" string is replaced by the name of the vendor. The values of new properties MAY include an "ignorable" property with a boolean type. If "ignorable" is set to true, then request routers and surrogates in any interconnected CDN MAY safely ignore the new property. If "ignorable" is set to false, then a CDN which does not understand the property MUST NOT service a request for the corresponding content. Niven-Jenkins, et al. Expires January 10, 2013 [Page 30] Internet-Draft CDN Interconnect Metadata July 2012 6. IANA Considerations This document requests the registration of the "application/cdni" MIME type. 7. Security Considerations The CDNI Metadata Interface is expected to be secured as a function of the transport protocol (e.g. HTTP authentication). If a malicious metadata server is contacted by a downstream CDN, the malicious server may provide metadata to the downstream CDN which denies service for any piece of content to any user agent. The malicious server may also provide metadata which directs a downstream CDN to a malicious origin server instead of the actual origin server. A malicious metadata client could request metadata for a piece of content from an upstream CDN. However, given the current set of metadata properties, no useful information would be compromised. 8. Acknowledgements The authors would like to thank David Ferguson and Francois le Faucheur for their valuable comments and input to this document. 9. References 9.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 4291, February 2006. [RFC5952] Kawamura, S. and M. Kawashima, "A Recommendation for IPv6 Address Text Representation", RFC 5952, August 2010. 9.2. Informative References [I-D.davie-cdni-framework] Davie, B. and L. Peterson, "Framework for CDN Interconnection", draft-davie-cdni-framework-00 (work in progress), July 2011. Niven-Jenkins, et al. Expires January 10, 2013 [Page 31] Internet-Draft CDN Interconnect Metadata July 2012 [I-D.ietf-cdni-problem-statement] Niven-Jenkins, B., Faucheur, F., and N. Bitar, "Content Distribution Network Interconnection (CDNI) Problem Statement", draft-ietf-cdni-problem-statement-03 (work in progress), January 2012. [I-D.ietf-cdni-requirements] Leung, K. and Y. Lee, "Content Distribution Network Interconnection (CDNI) Requirements", draft-ietf-cdni-requirements-02 (work in progress), December 2011. [I-D.zyp-json-schema] Zyp, K. and G. Court, "A JSON Media Type for Describing the Structure and Meaning of JSON Documents", draft-zyp-json-schema-03 (work in progress), November 2010. [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, January 2005. [RFC4151] Kindberg, T. and S. Hawke, "The 'tag' URI Scheme", RFC 4151, October 2005. [RFC4287] Nottingham, M., Ed. and R. Sayre, Ed., "The Atom Syndication Format", RFC 4287, December 2005. [XML-BASE] Marsh, J., Ed. and R. Tobin, Ed., "XML Base (Second Edition) - http://www.w3.org/TR/xmlbase/", January 2009. Appendix A. Relationship to the CDNI Requirements Section 6 of [I-D.ietf-cdni-requirements] lists the requirements for the CDNI Metadata Distribution interface. This section outlines which of those requirements are met by the CDNI Metadata interface specified in this document. All metadata requirements are met either directly or indirectly by the CDNI Metadata Interface described in this document. The following paragraphs describe notable exceptions. Requirements related to pre-positioning of metadata are not met directly by this document. Triggering metadata pre-positioning is beyond the scope of the CDNI Metadata interface. However, the interface as described by this document supports pulling metadata on- Niven-Jenkins, et al. Expires January 10, 2013 [Page 32] Internet-Draft CDN Interconnect Metadata July 2012 demand for the purpose of pre-positioning. Requirement META-13 relating to feedback from the downstream CDN to the upstream CDN with respect to metadata is not directly supported by the pull-based interface described in this document. As an alternative, the downstream CDN may use the CDNI Logging interface to convey error conditions related to metadata. Requirement META-18 relating to surrogate cache behavior parameters is supported via extensibility. However, the example parameters in META-18 are not described in this document. Authors' Addresses Ben Niven-Jenkins Velocix (Alcatel-Lucent) 3 Ely Road Milton, Cambridge CB24 6AA UK Email: ben@velocix.com Rob Murray Velocix (Alcatel-Lucent) 3 Ely Road Milton, Cambridge CB24 6AA UK Email: rmurray@velocix.com Grant Watson Velocix (Alcatel-Lucent) 3 Ely Road Milton, Cambridge CB24 6AA UK Email: gwatson@velocix.com Niven-Jenkins, et al. Expires January 10, 2013 [Page 33] Internet-Draft CDN Interconnect Metadata July 2012 Matt Caulfield Cisco Systems 1414 Massachusetts Avenue Boxborough, MA 01719 USA Phone: +1 978 936 9307 Email: mcaulfie@cisco.com Kent Leung Cisco Systems 3625 Cisco Way San Jose 95134 USA Phone: +1 408 526 5030 Email: kleung@cisco.com Niven-Jenkins, et al. Expires January 10, 2013 [Page 34]