1 Introduction

The Peer Content Caching and Retrieval: Content Identification data structure specifies the Content Information Data Structure format used to uniquely identify content for discovery and retrieval purposes on a peer-to-peer network. This data structure is used within the Peer Content Caching and Retrieval service framework. The Content Information Data Structure is used in the discovery protocol specified in [MS-PCCRD] and the retrieval protocol described in [MS-PCCRR] to identify content for discovery, response, and retrieval requests. The Content Information Data Structure contains all the necessary information to allow a peer to uniquely specify content for discovery, and ensures the confidentiality and integrity of downloaded content. To satisfy these requirements, Content Information uses cryptographic hashing and encryption algorithms to encrypt and generate hashes of the content and includes a shared secret that is specific to that content.

The Peer Content Caching and Retrieval Framework is based on a peer-to-peer discovery and distribution model, where the peers themselves act as caches from which they serve other requesting peers. The framework supports the mode of using pre-provisioned hosted caches in place of peer-based caching. The framework is designed to reduce bandwidth consumption on branch-office wide-area-network (WAN) links by having clients retrieve content from distributed caches, when distributed caches are available, rather than from the content servers, which are often located remotely from branch offices over the WAN links. The main benefit of the framework is to reduce operation costs by reducing WAN link utilization, while providing faster downloads from the local area networks (LANs) in the branch offices.

Sections 1.7 and 2 of this specification are normative. All other sections and examples in this specification are informative.

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