Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1999-06-24
2004-03-16
Pham, Chi (Department: 2667)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S404000, C370S248000
Reexamination Certificate
active
06707823
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a network designing method and to a recording medium on which the control program is recorded. Particularly, the present invention is to provide a method of designing an inter-ring connection network with a fault-recoverable feature.
Ring systems have been used in order to secure communications by quickly using an alternate line when a failure occurs in a communication system (refer to, Tsong-Ho wu, Fiber Network Survivability, 1992, Artech House).
FIG. 10
illustrates the topology of a communication network where the ring systems can be installed. The topology consists of nodes
1
and spans
2
. A ring system is formed by the ring
3
. The ring
3
represents a closed path which does not contain the same nodes
1
of two or more and the same nodes
2
of two or more.
As shown in
FIGS. 11 and 13
, the ring system consists of an add drop multiplexers (ADMS)
61
to
64
and fibers
7
and
71
to
74
. The ADM
61
is set up to the node
1
configuring the ring
3
. The fiber
71
is set up to the span
3
configuring the ring
3
. Plural ring systems may be set up to the same ring
3
.
The ADM
6
, as shown in
FIG. 12
, separates the channel
103
to be received from the fiber
75
or inserts the channel
104
to be transmitted in the fiber
76
. Specifically, the channel
101
with the slot #
1
allocated and the channel
102
with the slot #
2
allocated can pass through the ADM
6
while the slot numbers are not changed. The channel
103
with the slot #
3
allocated is branched from the fiber
75
to receive by the ADM
6
. The channel
104
with the slot #
4
allocated is inserted in the fiber
76
to transmit from the ADM
6
. The slot represents identifying channels multiplexed within a single fiber. Specifically the time slot in time division multiplex corresponds to the wavelength in wave division multiplex.
As disclosed in the foregoing literature, the ring system is roughly classified into a bi-directional ring system and an uni-directional ring system.
FIG. 11
illustrates the configuration of the bi-directional ring system
8
. Referring to
FIG. 11A
, a group of working fibers are set up in the bi-directional ring system
8
to accommodate bi-directional channels between certain ADMs in a normal state.
For example, the channels
106
and
107
are bi-directionally installed along the path routing counterclockwise from the ADM
61
to the ADM
64
. Moreover, a group of spare fibers that can accommodate bi-directional channels are installed for the failure. At a system failure, the ADMs connected to both ends of the spare fiber group changes the fiber connection. As shown in
FIG. 11B
, when the working fiber
71
and the spare fiber
72
between the ADMs
62
and
63
are cut, the ADM
62
is connected to the spare fiber
73
while ADM
63
is connected to the spare fiber
74
. Thus, the channel
106
is changed to the channel
108
so that the channel routing from the ADM
64
to the ADM
61
is secured.
FIG. 13
shows slot numbers allocated to respective channels on the uni-directional fiber set between ADMs in the bidirectional ring system
8
. In this example, it is assumed that
32
channels per fiber at maximum can be multiplexed. Each ADM, as shown in
FIG. 11
, does not change the slot number of the channel
10
passing through the ADM. Hence, the same slot number must be allocated to the fiber through which each channel
10
is routed.
Referring to
FIG. 13
,
8
channels are set between the ADMs
61
and
63
. Slot numbers #
12
to #
19
are respectively allocated to the
8
channels along the path routing clockwise or counterclockwise between the ADM
61
and the ADM
63
. The channel with #
20
allocated is set along the path routed counterclockwise between the ADMs
63
and
64
. The channels with the slot numbers #
1
to #
7
are set along the path routing clockwise between the ADMs
61
and
64
. The channels with the slot numbers #
1
to #
11
are set along the path routing counterclockwise between the ADMs
61
and
64
.
FIG. 13
shows the method wherein the bi-directional ring system
8
detours around a failure in span units. In addition, there is the failure detouring method which changes channels used across each node pair from channels on a clockwise or counterclockwise routing path to the channels with the same slot on a counterclockwise or clockwise routing path.
In the bi-directional ring system shown in
FIG. 11
, if the ADM
62
is failed, each of the ADMs
61
and
63
turns back the channels within the working fiber to a spare fiber, so that the failed channel can be restored.
FIG. 14
illustrates the configuration of the unidirectional ring system. As shown in
FIG. 14A
, the unidirectional ring system
9
simultaneously accommodates in a normal state a group of bidirectional channels in the clockwise direction and a group of bi-directional channels in the counterclockwise direction, which are installed between a group of ADMs
6
. For example, the bi-directional channels
109
and
1011
routing between the ADMs
61
and
64
are accommodated clockwise within the uni-directional working fiber
77
. Another group of bi-directional channels
1010
and
1012
arc accommodated counterclockwise within the spare fiber
78
. The ADM
61
receives two channels
109
and
1010
while the ADM
64
receives two channels
1011
and
1012
. As shown in
FIG. 14B
, cutting the working fiber
77
and the spare fiber
78
between the ADMs
62
and
63
does not adversely affect the channels
1010
and
1011
so that the bi-directional channel between the ADMs
61
and
64
can be secured.
The uni-directional ring system
9
shown in
FIG. 14
can secure the bi-directional channels even in a failure of the ADM
62
. Unlike the bi-directional ring system
8
, the uni-directional system accommodates the bi-directional channels installed between arbitrary ADMs in a uni-directional direction (clockwise or counterclockwise) circled from a node
1
to another node
1
within the ring
3
. In this case, the maximum number of channels required between ADMs within each ring system is equal to the total number of slots per fiber.
FIG. 15
is a schematic diagram illustrating an inter-ring connection network where plural bi-directional ring systems
81
to
83
are connected together. When a channel is set between different nodes
1
not belonging to the same ring
3
, it must be routed via plural different bi-directional systems installed in different rings
3
. For example, in the bi-directional ring systems
81
and
82
respectively installed in different rings
3
, the cross connect unit (XC)
5
interconnects the ADMs
66
and
67
in the same node
14
. The XC unit has the cross connect function of arbitrarily connecting a routing channel from a certain port to another port and the slot conversion function of converting the slot number allocated to the channel routing each port.
The ADM
68
belonging to the bi-directional ring system
82
is connected to the ADM
69
belonging to the bi-directional ring system
83
. When the channel
105
is set between the ADM
65
installed to the node
13
and the ADM
68
installed to the node
15
, the slot #
1
is allocated to the route between the ADMs
65
and
66
belonging to the bi-directional ring system
81
while the slot #
3
is allocated to the route between the ADMs
67
and
68
belonging to the bi-directional ring system
82
.
In this case, the XC
5
switches the slot number #
1
to the slot number #
3
. When the XC
5
performs the slot conversion by interconnecting different bi-directional ring systems
8
, independent slot numbers can be allocated to bi-directional ring systems through which channels are routed. As a result, the improved channel accommodation efficiency can be expected, compared with the case of no connection with the XC
5
. However, it should be noted that when the XC
5
in the node
14
is in a trouble state, the channel
105
cannot be recovered.
There
Dickstein Shapiro Morin & Oshinsky LLP.
Hoang Thai D
NEC Corporation
Pham Chi
LandOfFree
Network designing method and recording medium on which the... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Network designing method and recording medium on which the..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Network designing method and recording medium on which the... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3208879