As revised 2006.05.04
Bionic Buffalo Tech Note #55
5. UserNetwork Download Protocol
The download protocol is a simple protocol used to transfer files, data, or objects from server to client.
There are three variations (called scenarios), sharing the same message formats but operating
flowcontrolled download is similar to ftp or other oneonone file transfer protocols, using flow
control, requests for specific blocks, and sliding windows
nonflowcontrolled download omits requests for specific blocks; a server can transfer to
multiple clients at once
carousel download involves repeated transmissions from the server, independent of client
requests; a specialized form, object carousels, defines the encapsulation of certain types of
DSMCC objects within the data
When download uses twoway communication, the channels often are asymmetric, with the data sent in
a high speed channel such as an MPEG data stream. In the carousel scenario, it is often used to send data
common to all clients, as electronic program guides, stock tickers, weather information, or software
With object carousels, copies of the objects are sent to the client, and the methods for those objects are
implemented on the client. Therefore, the object copies appear to be local objects, although they
originated on the server.
Of all the DSMCC protocols, download (especially carousel download) is the most common. Often
carousels are used when no other DSMCC protocols are used. The download portion of DSMCC has
been incorporated into other specifications.
6. UserNetwork Channel Change Protocol
The channel change protocol is defined to allow a client to change channels remotely in a switched
digital broadcast (SDB) environment. The SDB client makes channel change requests to an SDB server,
which is part of an interworking unit (IWU).
CCP and IWUs exist in environments where the IWU can receive more channels than the client. For
example, a great number of channels might be brought into an IWU in a neighbourhood using a high
bandwidth connection, while individual clients or homes in the neighbourhood are capable of receiving
only a few channels at a time. CCP can be used to select from the channels available at the IWU.
Copyright 2006 Bionic Buffalo. All rights reserved.
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