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Description  |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to computer networks in general and more
particularly to methods for distributing information within said network.
2. Prior Art
The prior art abounds with computer networks in which server stations
transmit data bases to other stations connected to the network. FIG. 3 is
an example of such prior art network. There is shown a local area network
(LAN) in which relatively expensive server station 2, which has a
non-volatile storage unit 1 such as a disk or diskette unit enabling it to
store programs without dissipating them, is connected through wiring 5 to
a plurality of relatively inexpensive terminal stations 4A, ... 4N, which
do not have such storage unit 1, but has memory units 3, the contents of
which dissipate when the power is turned off. Such terminal stations 4A,
... 4N in the computer system can be used as terminal stations only when
they are remotely initial-loaded with a program from server station 2 as
soon as the power turns on. Thus, each of terminal stations 4A, ... 4N
request the initial program loading from server station 2 when the power
is turned on.
In the conventional initial program loading technique, there is a problem
in that, even if terminal station 4B issues an initial program loading
request while another terminal station 4A is performing the initial
program loading, because the initial program loading can be performed by
only one teminal station at a time, terminal station 4B must wait until
another terminal station completes the initial program loading, and the
initial program loading for terminal station 4B is started only when it is
completed for another terminal station. Stated another way, initial
program loading is done sequentially. Thus, even if a station requests
loading while another system is being loaded, the requesting station must
wait until the loading of the other station is completed. This waiting
unnecessarily extends the time that a station must wait to receive an
initial program load from a server station must wait to receive.
That is, as shown in FIG. 4, when terminal station 4A first issues an
initial program loading request at time X.sub.1, a program is divided by
frame (4 K bytes), and transmitted from server station 2 to terminal 4A.
Every time the terminal station 4A receives a frame, it transmits
acknowledge ACK to the server station. After it transmits the final frame,
server station 2 transmits signal EOD, indicating the completion of
program transmission, and terminal station 4A correspondingly transmits
acknowledge ACK indicating the completion of initial program loading to
server station 2. At this time Y.sub.1, the initial program loading is
completed for terminal 4A. During this period, for example, at time
X.sub.2, even if the user of terminal 4B turns on the power and requests
the initial program loading, he must wait until time Y.sub.1, and then the
initial program loading is performed until time Y.sub.2 by repeating the
same steps as for terminal station 4A.
Therefore, if the users of terminal stations 4A and 4B turn on the power
substantially at the same time, the user of the late terminal station 4B
takes time (Y.sub.2 - X.sub.2) for the initial program loading that is
about two times of normal initial program loading time (Y.sub.1 -
X.sub.1). It is easily appreciated that, when N terminal stations are
turned on at approximately the same time, the last station takes N times
of the time required for the first one. Therefore, even when the initial
program loading takes several seconds in normal time of (Y.sub.1 -
X.sub.1) if ten-odd terminal stations are turned on at approximately the
same time, the initial program loading for the latest terminal station
takes several minutes in certain circumstances, which is unbearable in
practical use.
It is not such a rare circumstance for a number of terminal stations to be
turned on at approximately the same time. It is commonly encountered, for
example, in the case where terminal stations are simultaneously turned on
at the start of a company or a school.
Therefore, the solution of this problem has been important in the
conventional initial program loading technique.
SUMMARY OF THE INVENTION
It is thus the main object of the present invention to provide an apparatus
and technique which allow programs and other information to be downloaded
more rapidly than was heretofore possible.
More particularly, an object of the invention is to provide a method that
can perform the initial program loading to each of a number of terminal
stations in a normal duration of time, or in substantially the same
duration of time as that required for performing the initial program
loading when only one terminal station requests it, even if a number of
terminal stations are turned on at approximately the same time and request
initial program loading.
The method, according to the invention, wherein the initial program loading
is separately performed from a server station to each of a plurality of
terminal stations in response to individual request from them, comprises
the following steps:
when one terminal station requests the initial program loading, initiating
transmission of a program from the server station in response to the
request in such a manner that all terminal stations can receive it,
when another terminal station issues a request of initial program loading
during initial program loading for one terminal station, causing another
terminal station to start receiving of the program being transmitted from
the server station from the middle, and
causing the server station to transmit portions of the program not received
by another terminal station sequentially after completion of the initial
program loading for one terminal station.
According to the initial program loading method of the invention, even
during the initial program loading for one terminal station, other
terminal stations can be initial program loaded in the middle of it, and
the server station transmits sequentially portions of the program not
received by other terminal stations once it transmits the entire program
to complete the initial program loading for one terminal station, so that
other terminal stations later starting the initial program loading
complete it only by taking only approximately the same amount of time as
for the initial one terminal station.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows an embodiment of the method of the invention performing the
initial program loading to a plurality of terminal stations.
FIG. 2 shows a block diagram of a server station and terminal stations used
for the embodiment.
FIG. 3 shows a prior art computer system to which the method of the
embodiment applies.
FIG. 4 shows a diagram illustrating a conventional initial loading method
for a plurality of terminal stations.
DESCRIPTION OF PREFERRED EMBODIMENT
FIG. 1 shows an embodiment of the initial program loading method for a
plurality of terminal stations. Server station 2 and terminal stations 4A
and 4B constitute the computer network of the local area network shown in
FIG. 3. In practice, the number of terminal stations may be several tens
or several hundreds. FIG. 2 shows configurations of server station 2 and
terminal stations 4A, ... 4N that are used for the method of the
invention. Server station 2 is a relatively expensive computer that has
storage unit 1 such as a disk or diskette unit for storing programs
without dissipating them. 20 is a means for reading data from storage unit
1. 21 is a means for attaching a destination to which terminal station the
data or program is transmittedwhen server station 2 transmits it to the
terminal stations 4A, ... 4N. Once the destination attaching means
attaches a destination called a group address (G/A) to data or a program
to be transmitted, all terminal stations of a predefined group can receive
data or a program with the destination. That is, the use of this group
address allows a program to be transmitted so that all terminal stations
can receive it. 22 is a means for analyzing acknowledge ACK, indicating
receipt of the initial program loading request from the terminal station
or the program. 23 is a table for storing the terminal stations of the
group, and store data indicating which terminal station issues the initial
program loading, which terminal station completes the initial program
loading, and, when a terminal station starts the initial program loading
in the middle, a frame number of the portion of the program immediately
before the start. The program transmitted from server station 2 to a
terminal station for the initial program loading is divided into n frames
of 4K bytes, each of which is provided with a frame number and
sequentially transmitted. 24 is used to detect errors or completion of all
operations of the initial program loading. 25 is an adapter card for the
local area network.
Terminal stations 4A, ... 4N have memory units 3, the contents of which
dissipate when the power is turned off. The memory unit is divided into n
partitions of 4K bytes each and stores parts of an initial program loaded
program in the order of the frame numbers. 42 is for analyzing frame
numbers of the program transmitted from server station 2, and storing them
in the corresponding partitions of memory unit 3. Structuring the memory
and frames in accordance with the teachings of the present invention
provides a quick and simple way for a terminal to determine whether or not
it receives the entire program or frames of the program are missing. This
benefit further lessened the time for downloading to multiple terminals.
43 is a means for detecting the end of the initial program loading. 44 is
an adapter card for a local area network.
Referring to FIG. 1 again, the method of the embodiment is described. Now,
at time X.sub.3, the first terminal station 4A is turned on and issues an
initial program loading request to server station 2. In response to the
request, server station 2 attaches destinations of group addresses (G/A)
to the program so that it can be received by all terminal stations, and
sequentially transmits it in a form that it is divided into frame numbers
1 to n. When terminal station 4A receives each frame, it transmits
acknowledge ACK to server station 2, and stores the program in the
partitions of memory unit 3 in the order of the frame numbers. Table 23 of
server station 2 reflects the fact that terminal station 4A has requested
the initial program loading. When, at time X.sub.4, another terminal
station 4B is turned on and requests the initial program loading, it
receives the program being transmitted from server station 2 from the next
frame 2 in the same manner as terminal station 4A, and sequentially stores
it in the partitions of its memory unit 3 corresponding to the frame
numbers. In this case, because terminal station 4B starts receiving from
frame 2, it does not store the program in the first partition in memory
unit 3 that should store frame 1, but sequentially stores it from the
partition for frame 2, that is ahead of the first address by 4K bytes.
Terminal station 4B similarly transmits acknowledge ACK' to server station
2 as it receives the frames of the program. Table 23 of server station 2
reflects the fact that terminal station 4B has requested the initial
program loading, and has started loading from frame 2 after frame 1 of the
program. When server station 2 completes transmission of frames from 1 to
n, it transmits signal EOD indicating this fact. Because terminal station
4A stores sequentially from the first frame 1, it transmits at time
Y.sub.3 signal ACK indicating the completion of the initial program
loading, and starts to run the loaded program. However, terminal station
4B started the initial program loading at frame 2 for initial program
loading of terminal station 4A, and therefore has not yet received the
first frame 1. This is recognized by server station 2 from table 23, and
by terminal station 4B from an empty space in its memory unit 3. Thus,
server station 2 transmits frame 1, which is at the beginning of the
program and not received by terminal station 4B, after completion of the
initial program loading for terminal station 4A. Terminal station 4B
transmits acknowledge ACK' to server station when it receives frame 1. At
time Y.sub.4 terminal station 4B completes the initial program loading and
starts to run the loaded program. Server station 2 knows from acknowledge
ACK' from terminal station 4B that all initial program loading is
completed, and stops the transmission.
As appreciated from the above description, when two terminal stations 4A
and 4B are turned on and request initial program loading at approximately
the same time, time (Y.sub.3 - X.sub.3) required for the initial program
loading for the first terminal station 4A is substantially equal to time
(Y.sub.4 - X.sub.4) required for the initial program loading for the
second terminal station 4B, and thus approximately equal to the time when
the server station performs the initial program loading for only one
terminal station. It is easily understood that it is true for a case where
more than two terminal stations are turned on at approximately the same
time. Therefore, even if a plurality of terminal stations request the
initial program loading at approximately the same time, the time required
for the initial program loading when viewed from a user of a terminal
station is that required for loading only to his station. Thus, the time
for the initial program loading when viewed from the terminal station is
never extended even when the terminal stations are turned on at
approximately the same time. Although, in the description of the
embodiment, the number of transmissions of acknowledge signal ACK is
increased by the number of terminal stations performing the initial
program loading, it does not access the disk or diskette unit, and
therefore the increase of time due to this is almost negligible.
While the invention has been particularly shown and described with
reference to the preferred embodiment thereof, it will be understood that
various changes of form and details may be made therein without departing
from the spirit and scope of the invention.
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