Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
2002-02-06
2004-11-09
Cangialosi, Salvatore (Department: 2661)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S352000
Reexamination Certificate
active
06816495
ABSTRACT:
BACKGROUND OF THE INVENTION
In general, the present invention relates to a communication network which is built by using connection switching exchanges, such as an ATM (Asynchronous Transfer Mode) device, and a frame relay, each for implementing a plurality of logical connections on a single logical connection line and which is used for switching a plurality of logical connections of a plurality of communication lines, while rewriting connection identifiers in the connection switching exchanges. More particularly, the present invention relates to a connection switching network control method, a connection switching apparatus and a connection switching network management unit which are appropriate for implementing a high-speed and/or reliable large scale IP/(Internet Protocol) network which can easily recover even in the case of errors.
With regard to a connection switching exchange represented by the conventional ATM device and a frame relay, an example of the ATM device is described on pages 17 to 23 of a book entitled ‘ATM Network Bible with Illustrative Diagram’ published by Ohm Corporation in 1995.
FIG. 2
is a diagram showing the functions and structure of the conventional connection switching exchange in a simple and plain manner. The connection switching exchange
1
is connected to terminating nodes, such as communication terminals and gateways to another network or to other connection switching exchanges, each serving as an adjacent apparatus directly connected thereto by communication lines
2
. In the figure, there are communication lines
2
-
1
to
2
-
9
. The connection switching exchange
1
has a function of setting a plurality of logical connections
3
through each of the communication lines
2
, each for connecting the connection switching exchange to a directly connected adjacent apparatus. In the figure, there are shown logical connections
3
-
1
-
1
,
3
-
1
-
2
and
3
-
1
-
3
set up through the communication line
2
-
1
, a logical connection
3
-
8
-
1
set up through the communication line
2
-
8
and logical connections
3
-
9
-
1
and
3
-
9
-
2
set up through the communication line
2
-
9
.
The connection switching exchange further has a function of linking two logical connections
3
set in a single communication line
2
or in two communication lines
2
to each other. Any two logical connections
3
are linked to each other by a communication-line control mechanism
8
, a switching-table search mechanism
7
, a connection-identifier transformation mechanism
5
and a switch mechanism
6
, which are provided for each of the communication lines
2
, by using a switching table
4
provided for each communication line
2
or provided in common to the entire connection switching exchange
1
. In the example shown in
FIG. 2
, the switching table
4
, the switching-table search mechanism
7
and the connection-identifier transformation mechanism
5
form a communication-line interface
19
for each of the communication lines
2
. In the figure, there are shown line interfaces
19
-
1
,
19
-
2
,
19
-
8
and
19
-
9
.
The switching table
4
is a table showing information on each pair of logical connections to be linked to each other. More particularly, the switching table
4
shows mapping relations from information on communication lines and connection identifiers assigned to the logical connections on the input side to information on communication lines used by logical connections on the output side and connection identifiers assigned to the logical connections on the output side, as well as information on attributes of the logical connections, such as band attributes. In the example shown in
FIG. 2
, the connection identifiers
3
-
1
-
1
,
3
-
1
-
2
and
3
-
1
-
3
using the communication line
2
-
1
on the input side are associated respectively with the connection identifier
3
-
8
-
1
using the communication line
2
-
8
and the connection identifiers
3
-
9
-
1
and
3
-
9
-
2
using the communication line
2
-
9
on the output side. In this example, the switching table
4
is provided individually for each of the communication lines
2
.
Since a switching table
4
is associated with each communication line
2
, information for input-side communication line
2
is not present in the switching table
4
. More particularly, the switching table
4
comprises a column
41
showing connection identifiers assigned to input-side logical connections, a column
42
showing information on output-side communication lines, a column
43
showing connection identifiers assigned to logical connections using the output-side communication lines shown in the entry of column
42
, a column
44
showing logical connection attributes and a column
45
showing validity bits each indicating whether the line entry is valid or invalid.
The configuration of the switching table
4
varies to a certain degree in dependence on the technique of implementation of a switching-table search mechanism described below. In some cases, a column entry showing connection identifiers assigned to logical connections using communications lines on the input side is also omitted as is the case with information on communication lines on the input side. In the switching table shown in
FIG. 2
, the column
45
is used for showing validity bits each indicating whether the line entry is valid or invalid. As an alternative, without using the column
45
, a special value can be used in one of columns
41
-
43
to indicate that the information on a communication line or a connection identifier assigned to a communication line in the column entry for the input or output side is invalid. It should be noted that, in the case of the ATM, the connection identifier used in the switching table
4
is a pair of values representing a VPI (Virtual Path Identifier) and a VCI (Virtual Channel Identifier) respectively.
The communication-line control mechanism
8
is connected to its respective communication line
2
, and operates to execute input/output control in accordance with a technique for exchanging physical signals with the communication line
2
. More specifically, the communication-line control mechanism
8
converts data received serially from the communication line
2
into certain data packet units. A data packet
60
obtained as a result of such conversion is delivered to the connection-identifier transformation mechanism
5
by way of a signal line
51
. When the communication-line mechanism
8
receives a data packet
60
from the switch mechanism
6
by way of a signal line
57
, to be more specific, a signal line
57
-
1
,
57
-
2
,
57
-
8
or
57
-
9
, on the other hand, the communication-line mechanism
8
serially outputs the data packet
60
to the communication line
2
in accordance with the established technique for exchanging physical signals with the communication line
2
.
The connection-identifier transformation mechanism
5
is a mechanism for rewriting connection-identifier information
62
recorded in the header
61
of a data packet
60
received by the connection switching exchange
1
. As described above, a data packet
60
received from one of the communication lines
2
is processed by the communication line control mechanism
8
associated with the communication line
2
before being delivered to the connection-identifier transformation mechanism
5
by way of the signal line
51
. Before rewriting connection-identifier information
62
recorded in the header
61
of the data packet
60
, the connection-identifier transformation mechanism
5
first of all stores the data packet
60
temporarily and then delivers the connection-identifier information
62
recorded in the header
61
of the data packet
60
to the switching-table search mechanism
7
through a signal line
52
.
The switching-table search mechanism
7
searches the switching table
4
for a specific table entry
40
of the switching table
4
through a signal line
53
by using the connection-identifier information
62
recorded in the header
61
of the data packet
60
received through the sign
Kawakita Kenji
Miyamoto Takanori
Nishikado Takashi
Antonelli Terry Stout & Kraus LLP
Cangialosi Salvatore
Hitachi , Ltd.
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