2.1.2 Protocol Relationships

The following figure shows the protocol layering relationships for the Content Caching and Retrieval member protocols. The default relationship, which is indicated by a solid arrow, is "is transported by". The "includes" notation means that a protocol document includes a second document by reference (for example, [MS-SMB2] includes [MS-FSCC]). Member protocols are shown in shaded boxes.

Content Caching and Retrieval can be initiated both by SMB2 and HTTP. A Background Intelligent Transfer Service (BITS) client can use the system and acts as an HTTP client.

A content client can use either HTTP or HTTPS for communication with a hosted cache server specifically while it offers content.<4> The content is then retrieved by using the Peer Content Caching and Retrieval: Retrieval Protocol, as described in [MS-PCCRR].

A content client uses the Peer Content Caching and Retrieval Discovery Protocol, as described in [MS-PCCRD] (an implementation of [WS-Discovery]), to locate peer computers with cached content.

The majority of traffic in the system is performed by the Peer Content Caching and Retrieval: Retrieval Protocol, as described in [MS-PCCRR]. This protocol is used to transfer actual content regardless of the protocol that retrieved the content metadata.

Figure 6: Protocol relationships for Content Caching and Retrieval