Electrical computers and digital processing systems: multicomput – Computer-to-computer protocol implementing – Computer-to-computer data streaming
Reexamination Certificate
1998-02-19
2001-01-09
Burgess, Glenton B. (Department: 2757)
Electrical computers and digital processing systems: multicomput
Computer-to-computer protocol implementing
Computer-to-computer data streaming
C709S203000, C709S213000, C709S217000, C709S219000, C709S201000
Reexamination Certificate
active
06173329
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a distributed multimedia server device for delivering multimedia data to a plurality of terminals in response to a request from each terminal, and a distributed multimedia server data access method to be used in delivering multimedia data from a distributed multimedia server device to a plurality of terminals or storing multimedia data into a distributed multimedia server device from a multimedia data input device.
2. Description of the Background Art
Conventionally, a service for delivering multimedia data to each terminal has been realized by a single multimedia server device.
FIG. 1
shows a schematic configuration of a conventional single multimedia server device, in which a communication control unit
111
carries out communications with terminals and a central control unit
112
controls the multimedia server device as a whole, while a memory unit
113
temporarily stores multimedia data, etc. at a time of delivery to a terminal and a storage unit
115
stores multimedia data, where data transfers among the communication control unit
111
, the central control unit
112
, the memory unit
113
and the storage unit
115
are provided by a system bus
114
.
In a case of a single multimedia server device as shown in
FIG. 1
, there is a limitation on a maximum number of simultaneously connectable terminals due to a transfer neck of the system bus
114
and an input/output rate neck of the storage unit
115
. For this reason, there has been a proposition to increase the maximum number of simultaneously connectable terminals by using a distributed multimedia server device in which a plurality of server modules are connected through a network.
FIG. 2
shows a system configuration using a conventional distributed multimedia server device, in which each one of terminals
211
to
21
L issues a multimedia data read request to a distributed multimedia server device
23
through a terminal side network
22
and playbacks received multimedia data. Here, the terminal side network
22
is a network connecting the terminals
211
to
21
L with the distributed multimedia server device
23
.
The distributed multimedia server device
23
comprises server modules
2311
to
231
M for carrying out delivery of multimedia data with respect to terminals, and a control module
232
for receiving requests from terminals and issuing multimedia data delivery requests to the server modules.
One multimedia data is divided into fixed length multimedia blocks and distributedly stored in a plurality of server modules
2311
to
231
M. Note that each one of the server modules
2311
to
231
M has a configuration similar to that shown in
FIG. 1
so that each server module can operate as a single multimedia server device. The delivery of multimedia data using this distributed multimedia server device is carried out as follows.
(1) A multimedia data read request containing an identifier of a program to be read is transmitted from a terminal
21
i
to the control module
232
via the terminal side network
22
.
(2) A multimedia data delivery request is transmitted from the control module
232
to all the server modules
2311
to
231
M via the terminal side network
22
.
(3) Each of the server modules
2311
to
231
M delivers multimedia block that is distributedly stored in each server modules to the terminal
21
i
via the terminal side network
22
, while maintaining synchronization with respect to the other server modules so that the terminal does not receive multimedia data from a plurality of server modules simultaneously.
(4) The multimedia data delivery for a plurality of terminals is carried out simultaneously in a similar manner. In other words, there can be cases where a destination terminal of multimedia block deliver by one server module is different for successive multimedia blocks to be delivered.
However, the conventional distributed multimedia server device has been associated with the following problems.
(1) There is a need for each server module to maintain synchronization with respect to the other server modules so that the terminal does not receive multimedia data from a plurality of server modules simultaneously.
(2) The server module sequentially delivers multimedia data to different terminals, but when the terminal side network
22
is connection-less, there can be cases where multimedia data are not delivered to the terminal as intended because of collisions in the network so that the playback at the terminal can be interrupted. On the other hand, when the terminal side network
22
is connection oriented, there is a need for one server module to either maintain connections with all the terminals or repeat connection set up and release with respect to the terminals in short time intervals dictated by multimedia block delivery time.
In the former case it is necessary to maintain connections even while multimedia data delivery does not take place, whereas in the latter case a processing for connection set up and release causes overhead and an effective connection time during which multimedia data delivery can be carried out becomes relatively short, so that the utilization efficiency of the terminal side network
22
is low in either case.
(3) There is a need to provide the control module
232
for centralized control of the distributed multimedia server device
23
as a whole, besides the server modules
2311
to
231
M for carrying out multimedia data delivery.
(4) When the terminal side network
22
or the communication protocol between the terminals
211
to
21
L and the distributed multimedia server device
23
is changed, this change will affect all the server modules
2311
to
231
M.
Now, according to the conventional distributed multimedia server data access method, multimedia data for one program is divided into fixed length segments and stored cyclically among the server modules
2311
to
231
M. Then, a segment access at one server module is carried out in synchronization with segment accesses at the other server modules.
More specifically, the data read processing by the conventional distributed multimedia server data access method is carried out according to a sequence chart of
FIG. 3
as follows.
(1) The control module
232
receives a read request for a certain program from the terminal
21
i.
(2) The control module
232
issues a delivery request containing a synchronization information to the server module
2311
that stores a top segment of the requested program.
(3) The control module
232
then issues a delivery request containing a synchronization information to all the other server modules so that the other server modules sequentially carry out the data read processing in synchronization according to the synchronization information in such a manner that no interruption occurs in the playback at the terminal
21
i.
(4) Each server module reads relevant segments according to the synchronization information notified from the control module
232
, and transfers the read out segments to the terminal
21
i.
Next, as a concrete example of the conventional distributed multimedia server data access method, the time-slot centralized management scheme in which each server module manages a plurality of time-slots will be described.
Here, for the sake of simplicity, it is assumed that the distributed multimedia server device has two server modules where a server module #1 has three storage devices
2151
,
2152
and
2153
and a server module #2 has three storage devices
2251
,
2252
and
2253
.
FIG. 4
shows a timing chart for the time-slot processing used in the conventional multimedia server data access method for this exemplary case. In
FIG. 4
, six time-slot sequences each comprising twenty-four time-slots TS
01
, TS
02
, . . . , TS
24
of the equal interval are periodically generated in six storage devices. Each one of cycle
011
, cycle
012
, . . . , cycle
016
indicates a period for reading four time-slots constituting the time-slot sequence (a sub-cycle), and cycl
Fukazawa Katsuhiko
Nishimura Kazutoshi
Sasaki Chikara
Suzuki Hideharu
Burgess Glenton B.
Greer Burns & Crain Ltd.
Nippon Telegraph and Telephone Corporation
Salad Abdullahi E.
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