2.8.2.2.2 Segment Retrieval Session Initiation
A client in hosted cache mode, either a peer that downloads content from a hosted cache or vice versa, performs the following actions when a segment retrieval session is initiated:
The client starts the Download Timer for that segment retrieval session.
Adds the server to the Server Information List of the segment ID and sets the corresponding server status as "free".
If the requested block ranges in the segment consist of three or fewer consecutive blocks, the client:
Starts a download schedule session if the Download Initiated Flag has not been set.
Otherwise, initiates a Retrieval Protocol GetBlockList request (MSG_GETBLKLIST) to the server.