Multiplex communications – Data flow congestion prevention or control – Flow control of data transmission through a network
Reexamination Certificate
1999-03-03
2004-05-11
Chin, Wellington (Department: 2664)
Multiplex communications
Data flow congestion prevention or control
Flow control of data transmission through a network
C370S223000, C370S225000
Reexamination Certificate
active
06735171
ABSTRACT:
BACKGROUND OF INVENTION
(1) Field of the Invention
This invention relates to an SDH (Synchronous Digital Hierarchy) transmission system, an SDH transmission equipment and a line switching control method in the SDH transmission system which can be favorably used for making the line configuration of the SDH transmission system redundant.
(2) Description of the Related Art
Recently, an introduction of so called SDH network [called SONET (Synchronous Optical NETwork) in North America]) has been planned in every countries in the world along with the standardization of the transmission technique or method of SDH network recommended by ITU-T (while the SONET is recommended by Bellcore). This SDH network (SDH transmission system) is constructed by using various transmission equipment in accordance with SDH transmission system such as line terminal equipment or regenerator (hereinafter called “SDH transmission equipment” or “SDH equipment”).
As shown in
FIG. 9
, for example, the SDH transmission system
100
usually makes the line which connects an SDH equipment
200
with an SDH equipment
300
have a redundant configuration for enhancing the reliability of communication by providing a protection line
500
besides a work line
400
and once a fault such as a disconnection of line occurs on the work line
400
, the communication line is readily switched to the protection line
500
so as to avoid the disconnection of communication (main signal) caused by the line fault.
In the SDH network, the switching between the above-mentioned work line
400
and the protection line
500
is controlled with APS (Automatic Protection System) byte (K
1
, K byte) defined in a section overhead (SOH) 11 of a transmission frame [STM: Synchronous Transfer Module (STS: Synchronous Transport Signal in SONET)] having a frame format as shown in
FIG. 11
, for example.
In
FIG. 11
, a portion which follows SOH
11
is called as payload
12
and in this payload
12
, a given number [e.g. 3 for VC-
3
(approximately 51 Mb/s) and 1 for VC-
4
(approximately 150 Mb/s)] of desired communication data (main signal) such as ATM (Asynchronous Transfer Mode) cells are stored as lower order virtual containers (VC) corresponding to its transmission speed and their stored locations [the head (J
1
byte) of the path overhead (POH)
13
] are indicated by AU pointers
14
of SOH
11
.
For realizing the above-mentioned APS control function, the SDH equipment
200
(
300
), as shown in
FIG. 10
, for example, at least comprises a work unit
201
W (
301
W) which performs a transmission processing (bidirectional) through the work line
400
(a down-line
400
A, an up-line
400
B) and a protection unit
201
P (
301
P) which functions as a backup for this work line
201
W(
301
W) and performs a transmission processing (bidirectional) through the protection line
500
(a down-line
500
A, an up-line
500
B). The SDH equipment
200
(
300
) further includes an APS control firmware
202
(
302
) which performs a switching (APS) control between these units
201
W,
201
P (
301
W,
301
P).
In this case, however, the same signals (transmission frames) are transmitted through the work down-line
400
A (or the up-line
400
B) and the protection down-line
500
A (or the up-line
500
B) respectively and, in an usual operation, the reception terminal (SDH equipment
200
,
300
) selectively receives either one of signals (e.g. the signal having a better quality).
In
FIG. 10
, numerals
203
(
303
) indicate main signal transmission parts, numerals
204
(
304
) indicate POH insertion processing parts for inserting POH
13
into the transmitting main signals, numerals
205
(
305
) indicate POH termination processing parts which terminate POH
13
of the main signals after a termination of SOH
11
, and numeral
206
(
306
) indicate main signal reception parts for receiving main signals after termination of POH
13
.
In
FIG. 10
, numerals
600
,
700
respectively indicate microcomputers (&mgr;-COM). Using these microcomputers
600
,
700
, a maintenance man of the network individually sets setting information on APS control such as a unidirectional/bidirectional switching operation, a 1+1/1+N switching operation to respective APS control firmware (hereinafter simply referred to as “firmware”)
202
,
302
.
Here, “the unidirectional switching operation” means, for example, an operation to switch both work down-line
400
A and work up-line
400
B to the protection down-line
500
A and the protection up-line
500
B when a fault occurs on the work down-line
400
A, while “the bidirectional switching operation” means, for example, an operation to switch only the down-line
400
A to the protection down-line
500
A when a fault occurs on the down-line
400
A.
The “1+1 switching operation” means a switching operation used when the protection line is configured such that one protection line corresponds to one work line, while the “1+N switching operation” means a switching operation used when the protection line is configured such that one protection line corresponds to a plurality (N: integers more than 2) of work lines. In the configuration shown in
FIG. 10
, since the work units
201
W and
301
W (the protection units
201
P and
301
P) respectively include the down-line
400
A (
500
A) and the up-line
400
B (
500
B), the APS setting information to be set to the firmwares
202
and
302
become the “1+1 switching operation” and the “unidirectional switching operation”.
Incidentally, as shown in
FIG. 10
, the work unit
201
W (
301
W) is provided with a line fault detection/SOH termination part
211
W (
311
W), a high impedance part (switching part)
212
W (
312
W) and an SOH insert processing part
213
W (
313
W), while the protection unit
201
P (
301
P) is provided with a line fault detection/SOH termination part
211
P (
311
P), a high impedance part (switching part)
212
P (
312
P) and an SOH insert processing part
213
P (
313
P).
Here, the SOH insert processing parts
213
W,
213
P (
313
W,
313
P) respectively build up their transmission frames (synchronous transfer modules) by giving (inserting) the SOH
11
to the main signals addressed to the opposite side equipment
300
(
200
) in which the POH is already inserted. During this insert processing of the SOH
11
, “the switching request” and the “switching response” generated in the firmware
202
(
302
) are inserted and transmitted to the opposite side equipment
300
(
200
) as the APS byte (K
1
, K byte) of the SOH
11
.
The line fault detection/SOH termination parts (hereinafter simply referred to as the “termination parts”)
211
W,
311
W (
211
P,
311
P) respectively detect a fault of the work line
400
(the protection line
500
) by monitoring fault factors such as an input disconnection of optical signals (transmission frame) or the deterioration of input optical signals with an application (software) during the communication operation using the work units
201
W,
301
W (the protection units
201
P,
301
P), while the termination parts
211
W,
311
W (
211
P,
311
P) detect the “switching request” or the “switching response” from the opposite side equipment
300
(
200
) which are inserted to the SOH
11
as the APS byte by terminating the SOH
11
of the reception-side transmission frame.
Furthermore, when the line fault is detected at the termination part
211
W(
311
W) or
211
P (
311
P), the firmware
202
(
302
) recognizes the content of the fault and performs the transmission and reception of the APS byte between the opposite side equipment
300
(
200
) through the protection line
500
(or the work line
400
) and performs the switching control between the work unit
201
W (
301
W) and the protection unit
201
P (
301
P) of the own side equipment.
The above switching control is performed in such a manner that the firmware
202
(
302
) controls the conducting state and nonconducting state of the switching parts
212
W,
212
P (
312
W,
312
P) and such a control is always performed in response to the
Chin Wellington
Schultz William
LandOfFree
SDH transmission system, SDH transmission equipment and line... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with SDH transmission system, SDH transmission equipment and line..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and SDH transmission system, SDH transmission equipment and line... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3238613