Note: Descriptions are shown in the official language in which they were submitted.
CA 02203941 1997-06-26
COMMUNICATION SYSTEM RECONFIGURABLE
WITH REDUCED SWITCHING NODE BURDEN
The present invention relates generally to communications systems
and more specifically to a reconfigurable communications system in which
switching nodes are interconnectable by transmission links according to network
configuration signals supplied from a network control center, and is a divisional of
Serial No. 2,170,417, which itself is a divisional of Serial No. 2,039,371, filed March
28, 1991.
According to conventional reconfigurable communications systems, a
network control center is provided with a memory in which network configuration
data are stored in a matrix pattern of rows and columns so that the rows
correspond respectively to predefined network configurations and the columns
correspond respectively to switching nodes of the system. When the system traffic
is imbalanced due to varying user's communications needs or a varying community
of interest, a command is entered into a management console specifying one of
the predefined network configurations which is selected as the best for balancing
the system's traffc. The network configuration data corresponding to the selected
configuration is retrieved from the memory and sent to the switching nodes to
reconfigure the network.
However, there is a wide range of user's needs. To meet the varying
user's demands many network configurations must be predefined, and hence a
large capacity memory is required for storing corresponding network configuration
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data to achieve a high level of flexibility. In addition, during the network
reconhguration phases, each switching node clears all of its static connections in
response to the signal from the network control center before it establishes newstatic connections. However, this increases the burden of the controller of eachswitching node.
Application Serial No. 2,170,418, filed on March 28, 1991, which is also
a divisional of the parent Application Serial No. 2,039,371, relates to a
communications system which reduces the amount of data to be stored in a
network management memory necessary for network configuration.
That divisional application provides a method and an apparatus for
factoring network configuration data into first component data and second
component data, storing the first and second component data into memory and
multiplying appropriate first and second component data to obtain desired network
configuration data for transmission to switching nodes.
Specifically, that divisional application provides a communications
system having a plurality of switching nodes, each being capable of establishingand removing relatively static connections between transmission links in response
to network configuration signals and of establishing relatively dynamic connections
through the established static connections in response to information pertaining to
call-by-call connection requests from user terminals, wherein the system includes
a network control center having a management console to which a command is
entered as an indication of a desired one of a plurality of predefined network
configurations. Circuit status bits (first component data) are stored in a first matrix
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pattern of rows associated with the predefined network configurations and columns
associated with predefined circuit configurations, and destination status codes
(second component data) are stored in a second matrix pattern of rows associatedwith the circuit configurations and columns associated with the switching nodes,each of the circuit configurations comprising one or more transmission links. Each
of the bits stored in each column of the first matrix pattern indicates the presence
or absence of the circuit configuration associated with the column of the first matrix
pattern, and each of the codes indicates the presence or absence of transmissionlinks from each switching node to possible destination nodes. In response to a
command entered to the management console, the binary values of the circuit
status bits stored in one of the rows of the first matrix pattern are respectively
multiplied with binary values of the destination status codes stored in each column
of the second matrix pattern, and the multiplied binary values are summed so that
network configuration data is derived with respect to a desired network
configuration. The network configuration data is then transmitted to the switching
nodes to reconfigure the system.
The parent application describes and claims a communications system
with the ability to detect a difference between first and second network
configuration data corresponding respectively to an existing network configuration
and a new network configuration which is currently non-existent, and transmitting
the difference as a network configuration signal to switching nodes.
More specifically, the parent application provides a communications
system having a plurality of switching nodes, each being capable of establishing - 3 -
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and removing relatively static connections between transmission links in response
to network configuration signals and of establishing relatively dynamic connections
through the established static connections in response to information pertaining to
call-by-call connection requests from user terminals, wherein the system includes
a network control center having a management console to which a command is
entered as an indication of a desired one of a plurality of predefined network
configurations. Circuit status bits are stored in a first matrix pattern of rowsassociated with the predefined network configurations and columns associated with
predefined circuit configurations, and destination status codes are stored in a
second matrix pattern of rows associated with the circuit configurations and
columns associated with the switching nodes. Each of the circuit configurations
comprises one or more transmission links, and each of the bits stored in each
column of the first matrix pattern indicates the presence or absence of the circuit
configuration associated with the column of the first matrix pattern, and each of the
codes indicates the presence or absence of transmission links from each switching
node to possible destination nodes. In response to a command entered to the
management console, the circuit status bits are retrieved from one of the rows of
the first matrix pattern and the destination status codes are retrieved from each
column of the second matrix pattern, and the binary values of the retrieved circuit
status bits are multiplied with the binary values of the retrieved destination status
codes and the multiplied binary values are summed to derive network configuration
data associated with a first network configuration. In response to a second
command entered to the management console, a similar process is repeated to
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derive network configuration data associated with a second network configuration.
A difference is detected between the network configuration data successively
derived with respect to the first and second network configurations and transmitted
as network configuration signals to the switching nodes.
The parent application also describes and claims a communications
system in which the circuit status bits are retrieved from each row of the first matrix
pattern and the destination status codes are retrieved from each column of the
second matrix pattern. The binary values of the retrieved circuits status bits are
respectively multiplied with the binary values of the retrieved destination status
codes, the multiplied binary values being summed together to derive network
configuration data for each of the predefined network configurations. The network
configuration data derived for the predefined network configurations are stored into
a memory. In response to a command entered to the console, a pair of first and
second network configuration data are retrieved from the memory, with the first
network configuration data being associated with a new network configuration andthe second network configuration data being associated with a previous network
configuration. A difference between the network configuration data of the pair is
detected and transmitted as the network configuration signals to the switching
nodes.
According to one aspect of the present invention, there is provided a
communications system having a plurality of switching nodes each being capable
of establishing and removing relatively static connections between transmission
links in response to network configuration signals and of establishing relatively
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dynamic connections through the established static connections in response to
information pertaining to call-by-call connection requests from user terminals, a
network controller comprising:
memory means for storing a plurality of network configuration data
corresponding respectively to distinct network configurations of the system, thenetwork configuration data indicating presence or absence of transmission links
from each switching node to possible destination nodes;
control means for retrieving first and second network configuration data
corresponding respectively to an existing network configuration and a most recent
network configuration from the memory means, and generating a code indicative
of a difference between the first and second network configuration data; and
means for transmitting the difference indicative code to a
corresponding one of the switching nodes as the network configuration signals.
Another aspect of the invention provides a communications system
having a plurality of switching nodes each being capable of establishing and
removing relatively static connections between transmission links in response tonetwork configuration signals and of establishing relatively dynamic connectionsthrough the established static connections in response to information pertaining to
call-by-call connection requests from user terminals, and a network control center
having a memory for storing a plurality of network configuration data corresponding
respectively to distinct network configurations of the system, the network
configuration data indicating presence or absence of transmission links from each
switching node to possible destination nodes, a method comprising the steps of:
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a) retrieving first and second network configuration data
corresponding respectively to an existing network configuration and a most recent
network configuration from the memory;
b) generating a code indicative of a difference between the first and
second network configuration data; and
c) transmitting the difference indicative code from the network
control center to a corresponding one of the switching nodes as the network
configuration signals.
Thus, the communications system of the present invention reduces the
burden taken by each switching node of the system during a network
reconfiguration phase. A plurality of network configuration data corresponding
respectively to distinct network configurations are stored in a memory, and first and
second network configuration data corresponding respectively to an existing
network configuration and a new network configuration are retrieved from the
memory. A determination is made if there is a difference between the first and
second network configuration data. The second network configuration data is sentto switching nodes as network configuration signals if it is determined that there is
a difference between the first and second network configuration data. A code
indicative of such a difference may be detected and transmitted, instead of the
second network configuration data, to only those switching nodes requiring network
reconfiguration .
The embodiments of the invention will now be described, by way of
example, with reference to the accompanying drawings, in which:
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Figure 1 shows in block form a communications network having a
network control center;
Figure 2 shows a list of circuit status bits stored in memory in a matrix
format tabulated according to network configurations and circuit configurations;Figure 3 shows a list of destination status codes stored in the memory
in a matrix format tabulated according to circuit configurations and switching nodes;
Figures 4A through 4G show the contents of the destination status
codes of respective circuit configurations stored in the memory in a matrix format
tabulated according to source and destination switching nodes;
Figure 5 shows in flowchart form a sequence of programmed
instructions performed by the controller of Figure 1;
Figure 6 shows modified program instructions performed by the
controller of Figure 1;
Figures 7A through 7E show in matrix form network configuration data
of predefined network configurations stored in locations of the memory accessible
as a function of network identifiers and switching node identifiers;
Figure 8A shows in flowchart form a sequence of programmed
instructions performed by the controller according to the present invention;
Figure 8B shows in flowchart form a sequence of modified instructions
according to the present invention;
Figure 9A shows in flowchart form a sequence of modified program
instructions according to the present invention; and
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Figure 9B shows in flowchart form a sequence of further modified
program instructions according to the present invention.
Referring now to Figure 1, there is shown a communications network
according to the present invention. The network is made up of a plurality of
switching nodes 2 for servicing user's data terminals 1. For purposes of
disclosure, five switching nodes 2, through 25 are shown interconnected by full-duplex transmission links 3, through 39. A network controller 4 is provided for
setting up relatively static connections between switching nodes of the network by
entering commands at a management console 6.
Each switching node has a digital switching matrix that responds to
signalling information from the user terminals pertaining to call-by-call connection
requests by establishing a circuit-switched connection or a packet-switched
connection, depending on the mode of operation of the system. To permit instant
reconfiguration of the network, each switching node has a digital cross-connect
function that responds to a network configuration signal from the network control
center 4 by establishing a relatively static connection to one or more switchingnodes.
Network control center 4 is made up of a network controller 5, a
management console 6, a network management memory 7, and transmitters
81 ~ 85 which are associated respectively with switching nodes 2, ~ 25 through
respective control channels 9. As will be described, when a traffic imbalance
occurs in the network, manual command input is supplied from console 6 to
controller 5 indicating a network identifier (m) which reconfigures the original
CA 02203941 1997-06-26
configuration to eliminate the trafffic imbalance (where m is an identifier uniquely
indicating a particular network configuration). In response to this signal, controller
5 searches through the memory 7 and generates network configuration data (Nmn)
for each switching node 2n and applies it to a corresponding transmitter 8n~ in which
it is converted into a format indicating a sequence of destination nodes or linkidentifiers followed by a 0 or a 1 indicating respectively the provisioning or
disconnecting of a link to a destination.
The communications network of this invention comprises a plurality of
circuit configurations. For purposes of disclosure, seven different circuit
configurations and five different network configurations are predetermined, and
more than one circuit configuration is chosen from the seven circuit configurations
for each of the five network configurations.
In the network management memory 7 is stored a circuit configuration
table 10 as shown in Figure 2. Circuit configuration table 10 is a list of circuit
status bits (Emp)~ where p identifies a particular circuit configuration. Each circuit
status bit Emp is either a binary 1 indicating the presence of a circuit configuration
or a binary 0 indicating the absence of any circuits. A unique set of Emp bits is
assigned to each network configuration. A network configuration m = 1, for
example, is assigned a set of bits E1" E,2, E,3, E,4, E15, E,6 and E17, which are
respectively, "1", "1", "0", "0", "0", "0" and "0". Therefore, network configuration
m = 1 is made up of circuit configurations p = 1 and p = 2, and a network
configuration m = 2 is assigned a set of bits circuit status bits E21, E22, E23, E24, E25,
E26 and E27, which are respectively, "1", "0", "1", "0", "1", "0" and "0". Therefore,
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network configuration m = 2 is made up of circuit configurations p = 1, p = 3 and
p = 5.
As shown in Figure 3, the circuit configurations are represented by a
destination status channel table 11 which is stored in the network management
memory 7. Each of the seven circuit configurations is identified by a set of
destination status codes Cpn which correspond respectively to switching nodes 2nFor example, circuit configuration p = 1 is given by a set of codes C1" C12, C13, C14
and C15 and circuit configuration p = 2 is represented by a set of codes C21, C22,
C23, C24 and C2s
Details of the destination status codes will be described with reference
to Figures 4A ~ 4G.
Circuit configuration p = 1 is formed by link 32 between nodes 21 and
22 and link 33 between nodes 22 and 24 (Figure 4A). A list of codes C1n (where
n = 1, 2, . ..5) is given in a table 1 2A which indicates the destination status of circuit
configuration p = 1. A binary 1 in the destination status codes indicates the
presence of a link from a source node to a destination node which is specified by
the position of the bit in the code and a binary 0 indicates the absence of such a
link. In this case, code C1, for source node 21 is "01000", indicating that there is
a link available between nodes 21 and 22. Likewise, code C12 for source node 22
is represented by "10010", indicating that links are available between node 22 and
node 21 and between nodes 22 and 24. Code C14 for source node 24 is represented
by "01000", indicating that a link is available between nodes 24 and 22. The other
CA 0220394l l997-06-26
codes C,3 and C,5 are represented by all zeros indicating no links are available for
switching nodes 23 and 25.
In like manner, circuit configuration p = 2 is formed by link 37 between
nodes 24 and 25 and link 38 between nodes 23 and 25 (Figure 4B). A list of codesC2n is given in table 12B, indicating the destination status of circuit configuration
p = 2. Circuit configuration p = 3 is formed by link 35 between nodes 22 and 23 and
link 36 between nodes 22 and 25 (Figure 4C). A table 12C contains a list of codes
C3n for the destination status of circuit configuration p = 3. Circuit configuration
p = 4 is formed by link 34 between nodes 2, and 24 (Figure 4D). A list of codes C4n
for the destination status of circuit configuration 4 is given in table 12D. Circuit
configuration p = 5 is formed by link 38 between nodes 23 and 25 (Figure 4E). A
list of codes C5n for the destination status of circuit configuration 5 is given in table
12E. Circuit configuration p = 6 is formed by link 3, between nodes 2, and 23
(Figure 4F). A list of codes C6n for the destination status of circuit configuration 4
is given in table 12F. Finally, circuit configuration p = 7 is formed by link 39between nodes 2, and 25 (Figure 4G). A list of codes C7n for the destination status
of circuit configuration p = 7 is given in table 12G. Tables 12A ~ 12G are stored
in memory 7.
Figure 5 is a flowchart describing a sequence of programmed
instructions which are executed by network controller 5 for deriving network
configuration data Nmn from the circuit status bits Emp and destination status code
Cpn just described. Network configuration data Nmn is represented as follows:
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Nmn = ~ Emi Cin
i=1
The program is activated in response to a signal from management
console 6 when a network identifier m is determined for reconfiguring an existing
configuration. Program execution starts with step 20 in which variables p and n are
both reset to 1. Exit then is to step 21 which directs the reading of circuit status
bits Emp and destination status codes Cpn from memory 7 using variables m, p andn as address pointers. Control proceeds to step 22 in which circuit status bits Emp
are multiplied with destination status codes Cpn. Assume that if m is determinedto be equal to 1, E,1 and C" are fetched from memory 7 and multiplied together
to produce a product Nmn(j). Since E" = 1 and C" = 01000, N"(,) is equal to 01000
(see Figures 2 and 4A). Control advances to step 23 to store Nmn(p) into memory
7, and moves to decision step 24 to determine if p is equal to the total number of
the circuit configurations, i.e., 7. If the answer is negative, control goes to step 25
in which p is incremented by 1, with control returning to step 21 to repeat steps 22
and 23. Therefore, in the second pass through steps 22 and 23, N"(2) = E,2 x C2,= 1 x 00000 = 00000 is obtained (Figures 2 and 4B). In this way, the following
relations are obtained for switching node 2, as steps 22 and 23 are executed
seven times:
N"(,) = E1, x C" = 1 x 01000 = 01000 (Figures 2, 4A)
N"(2) = E,2 x C2, = 1 x 00000 = 00000 (Figures 2, 4B)
N"(3~ = E,3 x C3, = 0 x 00000 = 00000 (Figures 2, 4C)
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N"(4) = E,4 x C4, = 0 x 00010 = 00000 (Figures 2 4D)
N"(s) = E,5 x C5, = 0 x 00000 = 00000 (Figures 2 4E)
N"(6) = E,6 x C6, = 0 x 00100 = 00000 (Figures 2 4F)
N"(7) = E,7 x C7, = 0 x 00001 = 00000 (Figures 2 4G)
If an affirmative decision is made in step 24 control exits to step 26
to give a total (N") of the N"(,) through N"(7) values which is equal to 01000.
Network configuration data N" obtained at step 26 is stored into a most recent
data storage location of memory 7 (step 27).
Exit then is to step 28 in which controller 5 applies N" to transmitter
8" which in turn transmits this data as a network configuration signal to switching
node 2,. Control proceeds to step 29 to reset p to 1 and moves to step 30 to
check to see if n is equal to the total number of switching nodes i.e. 5. If theanswer is negative control moves to step 31 to increment n by 1 and returns to
step 21 to repeat the process for switching nodes 22 through 25 to obtain the
following network configuration data N,2 N,3 N,4 and N,5.
N,2 = ~ E,p Cj2
= E" C,2 + E,2 C22 + E,3 C32 + E,4 C42 + E~s Cs2 + E~6 C62
+ E,7 C72
= C,2 + C22
= 10010 + 00000
= 10010
N,3 = ~ E,p Cj3
= E" C,3 + E,2 C23
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= 00000 + 00001
= 00001
N,4 = ~ E,p Cj4
= E" C,4 + E,2 C24
= 01000 + 00001
= 01001
N,5 = ~ E,p C;s
= E" C,5 + E,2 C2s
= 000000 + 00110
1 0 = 001 1 0
If the decision is affirmative at step 30, control terminates the program
execution.
Therefore, network configuration signals N,2 through N,5 are transmitted
to switching nodes 22 ~ 25, respectively, from transmitters 82 ~ 85, to configure the
communications network as shown in Figure 7A, which is a combination of circuit
configurations p = 1 and p = 2. A list of network configuration data N" ~ N,5 istabulated as shown in a table 13A.
It is seen that the amount of data to be stored in network management
memory 7 is significantly reduced and hence a wide range of network
configurations can be accommodated, providing a high level of system flexibility.
Figure 6 is a flowchart in which network configuration data for networks
with identifiers m = 1 through m = 5 are prepared in advance and stored in memory
7 for later retrieval. Program execution begins with step 40, which initializes
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variables m, p and n by resetting them each to 1. Exit then is to step 41 to read
Emp and Cpn, using variables m, p and n as address pointers. Data Emp and Cpn are
then multiplied together to obtain Nmn(p) (step 42), which is stored into memory 7
(step 43). Variable p is checked to see if p = 7 (step 44). If the answer is
negative, p is incremented by 1 (step 45) and steps 41 to 43 are repeated, so that
N1,(1) through N1,(7) are stored into memory 7.
With the answer being affirmative in step 44, control exits to step 46
to give a total sum N11 of the N"(,) through N11(7) values. Exit then is to step 47 to
store N11 into memory 7 as network configuration data for switching node 2,.
Variable p is then reset to 1 (step 48) and variable n is checked to see if it equals
the total number of switching nodes (step 49). If the answer is negative, n is
incremented by 1 (step 50) and steps 41 through 48 are repeated for switching
nodes 22 through 25. In this way, N11 through N15 are stored in memory 7 as table
13A (Figure 7A) for a network configuration m = 1.
Exit then is to step 51 which checks to see if m = 5. If the answer is
negative, m is incremented by 1 (step 52), and steps 41 to 49 are repeated againto produce N21 through N25 for switching nodes 21 through 25, respectively, which
are connected in a network configuration identified with m = 2, which is formed by
circuit configurations 1 and 3.
More specifically, network configuration data N21 through N2s are
obtained by the following calculations, and stored in table 13B (Figure 7B):
N21 = ~ E2p Cp
= E21 C11 + E22 C21 + E23 C31 + E24 C41 + E25 C5, + E
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+ E27 C71
= C" + C3, +C5~
= 01000 + 00000 + 00000
= 01000
N22 = ~ E2p Cp2
= C-2 + C32 + C52
= 10010 + 00101 + 00000
= 10111
N23 = ~ E2p Cp3
= C,3 + C33 + C53
= 00000 + 01000 + 00001
= 01001
N24 = ~ E2p Cp4
= C,4 + C34 + C54
= 01000 + 00000 + 00000
= 01000
N25 = ~ E2p Cp5
= C,5 + C35 + C55
= 00000 + 01000 + 00100
= 01100
With m = 3, network configuration data N3, through N35 are obtained
by the following calculations, and stored in table 13C (Figure 7C):
N3, = ~ E3p Cp,
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- = E3, C" + E32 C21 + E33 C3, + E34 C4, + E35 C5~ + E36 C6
+ E37 C7,
= C" + C3, + C4~
= 01000 + 00000 + 00010
= 01010
N32 = ~ E3p Cp2
= C12 + C32 + C42
= 10010 + 00101 + 00000
= 10111
N33 = ~ E3p Cp3
= C,3 + C33 + C43
= 00000 + 01000 + 00000
= 01000
N34 = ~ E3p Cp4
= C,4 + C34 + C44
= 01000 + 00000 + 10000
= 11000
N35 = ~ E3p Cp5
= C,5 + C35 + C45
= 00000 + 01000 + 00000
= 01000
With m = 4, network configuration data N4, through N45 are obtained
by the following calculations, and stored in table 13D (Figure 7D):
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N4, = ~ E4p Cp,
= E4~ C11 + E42 C2. + E43 C31 + E44 C41 + E45 C51 + E46 C
+ E47 C71
= C" + C5, + C6-
= 01000 + 00000 + 00100
= 01100
N42 = ~ E4p Cp2
= C-2 + C52 + C62
= 10010 + 00000 + 00000
= 10010
N43 = ~ E4p Cp3
= C,3 + C53 + C63
= 00000 + 00001 + 10000
= 10001
N44 = ~ E4p Cp4
= C,4 + C54 + C64
= 01000 + 00000 + 00000
= 01000
N45 = ~ E4p Cp5
= C,5 + C55 + C65
= 00000 + 00100 + 00000
= 00100
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With m = 5, network configuration data N5, through N55 are obtained
by the following calculations, and stored in table 13E (Figure 7E):
N5, = ~ E5p Cp,
= E5~ C" + E52 C21 + E53 C3, + E54 C4, + E55 C5, + E56 C6
+ E57 C7,
= C6- + C7~
= 00100 + 00001
= 00101
N52 = ~ E5p Cp2
= C62 + C72
= 00000 + 00000
= 00000
N53 = ~ E5p Cp3
= C63 + C73
= 10000 + 00000
= 10000
N54 = ~ E5p Cp4
= C64 + C74
= 00000 + 00000
= ~~~~~
N55 = ~ E5p Cp5
= C65 + C75
= 00000 + 10000
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= 10000
Figure 8A is a flowchart according to an embodiment of the present
invention, which is intended to reduce the burden of the switching nodes during
system reconfiguration phases by transmitting new network configuration data to
those nodes requiring reconfiguration, rather than transmitting them to all switching
nodes. If a new network reconfiguration request is made, the program starts withoperations step 60 which directs the moving of network configuration data Nmn,
pertaining to the existing network to a new location of memory 7. Exit then is to
step 61 which directs the setting of variable m to the new network identifier ~).
Subroutine 62 follows, which directs the executing of the steps of Figure 5 by
skipping step 28 as indicated by line 32 (Figure 5) to obtain new network
configuration data Njn Control exits to step 63 to set variable n equal to 1. Exit
then is to step 64 to read existing network configuration data Nmn and new network
configuration data Njn Modulo-2 summation is performed bit-by-bit between data
Nmn and Njn to produce a differential signal Sn (step 65). Control proceeds to step
66 to check to see if Sn is equal to zero. If the answer is afffirmative, control exits
to step 68 and, if negative, moves to step 67 to send the new network configuration
data Njn to switching node 2n. Step 68 is then executed by checking to see if
n = 5. If the answer is negative, variable n is incremented by 1 (step 69) to repeat
the process until n = 5. Therefore, new network configuration data are sent to
those switching nodes needing reconfiguration.
The amount of data to be transmitted during network reconfiguration
phases can be further reduced by transmitting to those switching nodes requiring - 21 -
CA 02203941 1997-06-26
network reconfiguration data bits pertaining only to the routes or destinations of
such nodes where changes are to be effected. The instructions shown in Figure
8B are generally similar to those of Figure 8A except that step 67 of Figure 8A is
replaced with step 67A. Following a decision that Sn is not equal to 0 (step 66),
exit is to step 67A in which all bits of differential data Sn are searched for a binary
"1" which indicates that a route change is to be effected. Bit position data
representative of the bit positions in which a binary "1" is detected are transmitted
via transmitter 8n to switching node 2n~ On receiving the bit position data, switching
node 2n checks it against the current states of the links (routes). If the link
specified by the bit position data is a regular (currently active) link, it is
disconnected from the network and put into the list of spare links. If the specified
link is in the list of spares, it is established as a regular link and stricken from the
list of spare links.
Figure 9A is a flowchart according to a further embodiment of this
invention. According to this modification, network configuration data prepared
according to the flowchart of Figure 6 are utilized for subsequent network
reconfigurations.
The program of Figure 9A is executed in response to a command input
indicating a new network identifier. In step 70, variable m is set equal to the
identifier of the existing network and variable j is set equal to the new network
identifier. Variable n is set to 1 (step 71), and existing and new network
configuration data Nmn and Njn are recalled from memory 7 (step 72). Modulo-2
summation is performed bit-by-bit between data Nmn and Njn to produce a
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differential signal Sn (step 73). Control proceeds to step 74 to check to see if Sn
is equal to zero. If the answer is afffirmative, control exits to step 76 to store Njm
in memory, and if negative it moves to step 75 to send new network configurationdata Njn to switching node 2n. Step 77 is then executed by checking to see if n =
5. If the answer is negative, variable n is incremented by 1 (step 78) and control
returns to step 72 to repeat the process until n = 5.
The program of Figure 9A is modified as shown in Figure 9B, which
is similar to Figure 9A, with the exception that step 75 of Figure 9A is replaced with
step 75A which is identical to step 67A of Figure 8B. Following a decision that Sn
is not equal to 0 (step 74), exit is to step 75A in which all bits of differential data
Sn are searched for a binary "1" which indicates that a route change is to be
effected. Bit position data representative of the bit positions in which a binary "1"
is detected are transmitted via transmitter 8n to switching node 2n. On receiving
the bit position data, switching node 2n checks it against the current states of the
links (routes). If the link specified by the bit position data is a regular (currently
active) link, it is disconnected from the network and put into the list of spare links.
If the specified link is in the list of spares, it is established as a regular link and
stricken from the list of spare links.
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