U.S. patent number RE37,401 [Application Number 08/637,843] was granted by the patent office on 2001-10-02 for fault recovery system of a ring network.
This patent grant is currently assigned to Fujitsu Limited. Invention is credited to Yuji Takizawa, Kazuo Yamaguchi, Haruo Yamashita.
United States Patent |
RE37,401 |
Yamashita , et al. |
October 2, 2001 |
Fault recovery system of a ring network
Abstract
A fault recovery system of a ring network based on a synchronous
transport module transmission system, having a fault data writing
unit for writing, when an input fault is detected by a node, fault
data in a predetermined user byte in an overhead of a frame flowing
through both a working line and a protection line running in
opposite directions to each other. By detecting the fault data in a
supervision node or a node just before the fault position, the
supervision node or the node just before the fault position
executes a loopback operation.
Inventors: |
Yamashita; Haruo (Kawasaki,
JP), Takizawa; Yuji (Kawasaki, JP),
Yamaguchi; Kazuo (Hiratsuka, JP) |
Assignee: |
Fujitsu Limited (Kawasaki,
JP)
|
Family
ID: |
14763414 |
Appl.
No.: |
08/637,843 |
Filed: |
April 25, 1996 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
696742 |
May 7, 1991 |
05307353 |
Apr 26, 1994 |
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Foreign Application Priority Data
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May 9, 1990 [JP] |
|
|
2-119524 |
|
Current U.S.
Class: |
714/717; 714/4.5;
714/716 |
Current CPC
Class: |
H04J
3/085 (20130101); H04Q 11/04 (20130101); H04J
2203/0042 (20130101); H04J 2203/006 (20130101); H04J
2203/0089 (20130101); Y10S 370/907 (20130101) |
Current International
Class: |
H04J
3/08 (20060101); H02H 003/05 (); H03K
019/003 () |
Field of
Search: |
;714/717,716,712,2,4
;370/224,907 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
79426 |
|
May 1983 |
|
EP |
|
91129 |
|
Oct 1983 |
|
EP |
|
0102222 |
|
Mar 1984 |
|
EP |
|
0115658 |
|
Aug 1984 |
|
EP |
|
144953 |
|
Jun 1985 |
|
EP |
|
212701 |
|
Mar 1987 |
|
EP |
|
2114858 |
|
Aug 1983 |
|
GB |
|
2115649 |
|
Sep 1983 |
|
GB |
|
2260876 |
|
Apr 1993 |
|
GB |
|
53-68046 |
|
Jun 1978 |
|
JP |
|
56-75747 |
|
Jun 1981 |
|
JP |
|
56-119556 |
|
Sep 1981 |
|
JP |
|
56-112156 |
|
Sep 1981 |
|
JP |
|
56-112157 |
|
Sep 1981 |
|
JP |
|
56-112158 |
|
Sep 1981 |
|
JP |
|
56-149851 |
|
Nov 1981 |
|
JP |
|
57-173245 |
|
Oct 1982 |
|
JP |
|
57-173246 |
|
Oct 1982 |
|
JP |
|
58-117746 |
|
Jul 1983 |
|
JP |
|
59-57544 |
|
Apr 1984 |
|
JP |
|
58-80043 |
|
May 1984 |
|
JP |
|
59-91757 |
|
May 1984 |
|
JP |
|
58-80042 |
|
May 1984 |
|
JP |
|
59-158649 |
|
Sep 1984 |
|
JP |
|
60-46636 |
|
Mar 1985 |
|
JP |
|
60-136444 |
|
Jul 1985 |
|
JP |
|
60-197044 |
|
Oct 1985 |
|
JP |
|
60-197045 |
|
Oct 1985 |
|
JP |
|
60-236543 |
|
Nov 1985 |
|
JP |
|
61-1145 |
|
Jan 1986 |
|
JP |
|
61-2447 |
|
Jan 1986 |
|
JP |
|
61-58352 |
|
Mar 1986 |
|
JP |
|
61-58351 |
|
Mar 1986 |
|
JP |
|
61-292439 |
|
Dec 1986 |
|
JP |
|
61-292438 |
|
Dec 1986 |
|
JP |
|
62-94036 |
|
Apr 1987 |
|
JP |
|
62-98839 |
|
May 1987 |
|
JP |
|
62-214748 |
|
Sep 1987 |
|
JP |
|
63-46029 |
|
Feb 1988 |
|
JP |
|
63-43445 |
|
Feb 1988 |
|
JP |
|
63-161748 |
|
Jul 1988 |
|
JP |
|
63-263944 |
|
Oct 1988 |
|
JP |
|
63-316541 |
|
Dec 1988 |
|
JP |
|
1-12637 |
|
Jan 1989 |
|
JP |
|
1-105637 |
|
Apr 1989 |
|
JP |
|
1-105636 |
|
Apr 1989 |
|
JP |
|
1-112848 |
|
May 1989 |
|
JP |
|
1-112849 |
|
May 1989 |
|
JP |
|
1-143539 |
|
Jun 1989 |
|
JP |
|
1-221953 |
|
Sep 1989 |
|
JP |
|
1-221954 |
|
Sep 1989 |
|
JP |
|
1-221955 |
|
Sep 1989 |
|
JP |
|
1-196738 |
|
Nov 1989 |
|
JP |
|
2-10949 |
|
Jan 1990 |
|
JP |
|
2-10948 |
|
Jan 1990 |
|
JP |
|
2-10946 |
|
Jan 1990 |
|
JP |
|
2-81537 |
|
Mar 1990 |
|
JP |
|
85/93183 |
|
Jul 1985 |
|
WO |
|
Other References
Fukui et al., "Optical Subscriber Network Architecture for
Broadband ISDN", Intl. Conf. on Comm. '88, Jun. 12-15, 1988, p.
883-889. .
Hajikano et al., "Asynchronous Transfer Mode Switching Architecture
for Broadband ISDN", Intl. Conf. on Comm. '88, Jun. 12-15, 1988,
pp. 911-915. .
Nishisno et al., "Broadband Switching System Configuration and
Access Protocol", Intl. Conf. on Comm. '88, Jun. 12-15, 1988, pp.
928-933. .
Haney, R. D., "Rethinking Networks: A Coordinated Approach",
Mini-Micro Systems, Jul. 1985, pp. 145-153. .
Newman et al., "The QPSX MAN", IEEE Communications Magazine, vol.
26, No. 4, Apr. 1988, pp. 20-28. .
Rocher, E. Y., "Information Outlet, ULAN Versus ISDN", IEEE
Communications Magazine, Apr. 1987, vol. 25, No. 4, pp. 18-32.
.
Rokugo et al., "An Asynchronouse DS3 Cross-Connect System with
Add/Drop Capability", GLOBECOM '88, Nov. 28-Dec. 1, 1988, pp.
1555-1559. .
Fujimoto et al., "Broadband Subscriber Loop Network: Optical
Shuttle Bus", IEICE Technical Report, Oct. 28, 1987, pp. 51-58.
.
Taniguchi et al., "Experimental Broadband Subscriber Loop Network
`Otpical Shuttle Bus`", [English Abstract], IEICE Technical Report,
Jul. 22, 1988, pp. 1-6. .
Nakai et al., "A study on Highly Reliable Control in Loop Network
Systems", [English Abstract], IEICE Technical Report, Apr. 23,
1986, pp. 31-36. .
Ohnishi et al., "ATM Ring Protocol and Performance", Intl. Conf. on
Comm. '89, Jun. 11-14, 1989, pp. 394-398. .
Bellcore GR-1230-CORE (Issue 1), SONET Bi-directional Line-Switched
Ring Equipment Generic Criteria, Dec. 1993. .
Bellcore TR-NWT-000253 (Issue 2), Synchronous Optical Network
(SONET) Transport Systems: Common Generic Criteria, Dec. 1991.
.
CCITT Recommendations G.707 (Blue Book), Synchronous Digital
Hierarchy Bit Rates, Nov. 1988. .
CCITT Recommendations G.708 (Blue Book), Network Node Interface for
the Synchronous Digital Hierarchy, Nov. 1988. .
CCITT Recommendations G.709 (Blue Book), Synchronous Multiplexing
Structure, Nov. 1988. .
Kremer, A Bi-directional Ring APS Algorithm Which Deterministically
Prevents Misconnections, Contribution to T1 Standards Project
(T1X1.5/91-126), Jul. 15, 1991. .
Minami et al., High-Speed Optical Loop Network for Flexible
Multi-Service Integration, FUJITSU Sci. Tech.J., vol. 22, No. 22,
No. 2, Jun. 1986, pp. 106-114. .
Kingsley, Choices in Sonet Ring Architecture, Business
Communications Review, Jun. 1994, pp. 61-65. .
Wu et al., Feasibility Study of a High-Speed SONET Self-Healing
Ring Architecture in Future Interoffice Networks, IEEE
Communications Magazine, Nov. 1990, pp. 33-51. .
Ritchie et al., SYNTRAN--A new direction for digital transmission
terminals, IEEE Communications Magazine, vol. 23, No. 11, Nov.
1985, pp. 20-25. .
Prisco et al., Fiber Optic Regional Area Network, IEEE
Communications Magazine, vol. 23, No. 11, Nov. 1985, pp. 26-39.
.
McDonald, Recovery From Telecommunications Deregulation, IEEE
Communications Magazine, vol. 23, No. 11, Nov. 1985, pp. 40-41.
.
Ballart et al., SONET: Now it's the standard optical network, IEEE
Communications Magazine, Mar. 1989, pp. 8-15. .
Sosnosky et al., SONET Ring Applications for Survivable Fiber Loop
Networks, IEEE Communications Magazine, Jun. 1991, pp. 51-58. .
Boehm et al., Standardized Fiber Optic Transmission Systems--A
Synchronous Optical Network View, IEEE Journal on Selected Areas in
Communications, vol. SAC-4, No. 9, Dec. 1986, pp. 1424-1431. .
Reedy, The TDM Ring--A Fiber Optic Transport System for Campus or
Metropolitan Networks, IEEE Journal on Selected Areas in
Communications, vol. SAC-4, No. 9, Dec. 1986, pp. 1474-1483. .
Kerner et al., An Analysis of Alternative Architecture for the
Interoffice Network, IEEE Journal on Selected Areas in
Communications, vol. SAC-9, No. 9, Dec. 1986, pp. 1404-1413. .
Cardwell et al., Computer-Aided Design Procedures for Survivable
Fiber Optic Telephone Networks., IEEE Journal on Selected Areas in
Communications, vol. 7, No. 8, Oct. 1989, pp. 1188-1197. .
Wu et al., Survivable Network Architectures for Broadband Fiber
Optic Networks: Model and Performance Comparisons, IEEE Journal of
Lightwave Technologies, vol. 6, No. 11, Nov. 1988, pp. 1698-1709.
.
Tsai et al., A comparison of Strategies for Survivable Network
Design: Reconfigurable and Conventional Approaches, GLOBCOM '90
Conference Record, Dec. 2-5, 1990, pp. 301.1-301.1.7. .
Ellefson, Migration of Fault Tolerant Networks, GLOBCOM '90
Conference Record, Dec. 2-5, 1990, pp. 301.4.1-301.4.7. .
Ishii et al., Virtual Sub-container Multiplexing Method for Optical
Subscriber System, GLOBCOM '90 Conference Record, Dec. 2-5, 1990,
pp. 303.1.1-303.1.5. .
Iwashita et al., Evaluation of Fiber Network Configurations in
Access Networks, GLOBCOM '90 Conference Record, Dec. 2-5, 1990, pp.
303.5.1-303.5.5. .
Smith, Sonet Self-healing Networks, GLOBCOM '90 Conference Record,
Dec. 2-5, 1990, pp. 304.6.1-304.6.5. .
Wu et al., A Class of Self-Healing Ring Architectures for SONET
Nework Applications, GLOBCOM '90 Conference Record, Dec. 2-5, 1990,
pp. 403.2.1-403.2.8. .
Yan et al., Bandwidth Management in a Sonet Transport Network,
GLOBCOM '90 Conference Record, Dec. 2-5, 1990, pp.
705B.2.1-705B.2.7. .
Uenoya et al., Operation, Administration and Maintenance Systems of
the Optical Fiber Loop, GLOBCOM '90 Conference Record, Dec. 2-5,
1990, pp. 802.5.1-802.5.5. .
Catania et al., Performance-Reliability Improvement in a
Distributed System, GLOBCOM '89 Conference Record, Nov. 27-30,
1989, pp. 9.4.1-9.4.8. .
Wu et al., High-Speed Self-Healing Architectures for Future
Interoffice Networks, GLOBCOM '89 Conference Record, Nov. 27-30,
1989, pp. 23.1.1-23.1.7. .
Conlisk, Topology and Survivability of Future Transport Networks,
GLOBCOM '89 Conference Record, Nov. 27-30, 1989, pp. 23.5.1-23.5.9.
.
Karol et al., High-Performance Optical Local and Metropolitan Area
Networks: Enhancements of FDDI and IEEE 802.6 DQDB, GLOBCOM '89
Conference Record, Nov. 27-30, 1989, pp. 28.3.1-28.3.8. .
Asatani, Network Node Interface for New Synchronous Digital
Networks: Concepts and Standardization, GLOBCOM '88 Conference
Record, Nov. 28-Dec. 1, 1988, pp. 4.5.1-4.5.7. .
Nosu et al., Performance Consideration on High Capacity Optical FDM
Networks, GLOBCOM '88 Conference Record, Nov. 28-Dec. 1, 1988, pp.
15.6.1-15.6.5. .
Ohno et al., Optical High Speed (100Mbps) Token Ring System GLOBCOM
'88 Conference Record, Nov. 28-Dec. 1, 1988, pp. 20.4.1-20.4.8.
.
DeWilde et al., Integrated Switch and Cross-Connect Systems as a
Flexible Transport Network, GLOBCOM '88 Conference Record, Nov.
28-Dec. 1, 1988, pp. 21.5.1-21.5.4. .
Fujimoto et al., Experimental Broadband Drop/Insert Cross-Connect
System: 1.8 Gbit/s Optical Shuttle Bus, GLOBCOM '88 Conference
Record, Nov. 28-Dec. 1, 1988, pp. 29.6.1-29.6.6. .
Flanagan et al., Application Benefits of SONET Networking, GLOBCOM
'88 Coference Record, Nov. 28-Dec. 1, 1988, pp. 30.3.1-30.3.5.
.
Boehm, The SONET Interface and Network Applications, GLOBCOM '88
Conference Record, Nov. 28-Dec. 1, 1988, pp. 30.4.1-30.4.5. .
Sandesara et al., SONET Intra-Office Interconnect Signal. GLOBCOM
'88 Conference Record, Nov. 28-Dec. 1, 1988, pp. 30.5.1-30.5.7.
.
Ohta et al., A Dynamically Controllable ATM Transport Network Based
on the Virtual Path Concept, GLOBCOM '88 Conference Record, Nov.
28-Dec. 1, 1988, pp. 39.2.1-39.2.5. .
Sandesara et al., Synchronous Optical Network Format and Terminal
Applications, GLOBCOM '87 Conference Record, Nov. 15-18, 1987, pp.
13.1.1-13.1.5. .
Aragaki et al., A Fiber-Optic Point-to-Multipoint Interface
Configuration for ISDN Broadband Access, GLOBCOM '87 Conference
Record, Nov. 15-18, 1987, pp. 13.3.1-13.3.5. .
Hughes, SONET in California: Pacific Bell's Plans for the Physical
Layer Wideband Access, GLOBCOM '87 Conference Record, Nov. 15-18,
1987, pp. 13.4.1-13.4.3. .
Grover, The SELFHEALING Network: A Fast Distributed Restoration
Technique for Networking using Digital Crossconnect Machines,
GLOBCOM '87 Conference Record, Nov. 15-18, 1987, pp. 28.2.1-28.2.6.
.
Nakano et al., VLSI for Digital Cross-Connect Switch in Broad-Band
Access Network, GLOBCOM 'Conference Record, Nov. 15-18, 1987, pp.
28.6.1-28.6.5. .
Fujimoto et al., Broadband Subscriber Loop System using
Multi-Gigabit Intelligent Optical Shuttle Nodes, GLOBCOM '87
Conference Record, Nov. 15-18, 1987, pp. 37.3.1-37.3.6. .
Shimizu et al., A High-Speed Optical Transport Network with
Flexible Access Capabilities, GLOBCOM '87 Conference Record, Nov.
15-18, 1987, pp. 37.6.1-37.6.5. .
Wakabayashi et al., A Synchronous DS3 Add/Drop Multiplexer with
Cross-Connect, GLOBCOM '86 Conference Record, Dec. 1-4, 1986, pp.
33.5.1-33.5.5. .
Yukawa et al., Fiber Optics System Applications for Private
Communication Networks, GLOBCOM '86 Conference Record, Dec. 1-4,
1986, pp. 34.3.1-34.3.6. .
Harvey et al., Network Planning for the SYNTRAN Add/Drop Multiplex
(ADM), GLOBCOM '86 Conference Record, Dec. 1-4, 1986, pp.
45.3.1-45.3.5. .
Lewis et al., A Model of Slip Impairment in Synchronous Digital
Transmission, GLOBCOM '86 Conference Record, Dec. 1-4, 1986, pp.
45.6.1-45.6.5. .
Minami et al., 200 MB/S Synchronous TDM Loop Optical LAN suitable
for Multi-Service Integration, GLOBCOM '85 Conference Record, Dec.
2-5, 1985, pp. 1.4.1-1.4.6. .
Iguchi et al., Multi-Channel, Multi-Drop Digital Video Transmission
Equipments for Optical CATV, GLOBCOM '85 Conference Record, Dec.
2-5, 1985, pp. 1.5.1-1.5.5. .
Patir et al., An Optical Fiber based Integrated LAN or MAGNET's
Testbed Environment, GLOBCOM '85 Conference Record, Dec. 2-5, 1985,
pp. 1.6.1-1.6.5. .
Brandsma, PHILAN: A Fiber-Optic Ring for Integrated Traffic,
GLOBCOM '85 Conference Record, Dec. 2-5, 1985, pp. 15.5.1-15.5.4.
.
Ohno et al., Multipurpose Optical Loop Network, GLOBCOM '85
Conference Record, Dec. 2-5, 1985, 34.6.1-34.6.6. .
Boehm et al., SONET (Synchronous Optical Network), GLOBCOM '85
Conference Record, Dec. 2-5, 1985, pp. 46.8.1-46.8.8. .
Lecoy et al., Design and Realization of Optical Fiber Data Buses,
GLOBCOM '84 Conference Record, Nov. 26-29, 1984, pp. 2.2.1-2.2.5.
.
Ballart et al., Restructured DS3 Format for Synchronous
Transmission (SYNTRAN), GLOBCOM '84 Conference Record, Nov. 26-29,
1984, pp. 31.2.1-31.2.7. .
Jones et al., TDM Ring: A DS1 Transport System for Local Networks,
GLOBCOM '84 Conference Record, Nov. 26-29, 1984, pp. 42.2.1-42.2.8.
.
Maruta et al., SONET based Network Architecture and its
applications, ICC '90 Conference Record, Apr. 16-19, 1990, pp.
321.1.1-321.1.5. .
Flanagan, Planning a SONET Network, ICC '90 Conference Record, Apr.
16-19, 1990, pp. 321.2.1-321.2.6. .
McConnell, Utilizing Fiber Optic Rings for Network Survivability
and Restoration, ICC '90 Conference Record, Apr. 16-19, 1990, pp.
321.3-321.3.4. .
Lau, An Architecture for a SONET Self-Healing Ring, Contribution to
T1 Standards Project (T1X1.5/89-088), May 10, 1989. .
Nishida et al., Phase 2 SONET APS: Dual Control for APS Scheme,
Contribution to T1 Standards Project (T1X1.5/89-054), Apr. 24,
1989. .
Hasegawa et al., Protection Switching in a SONET Ring Architecture,
Contribution to T1 Standards Project (T1X1.5/89-053), Apr. 12,
1989. .
CCITT Study Group XV Working Party 5 Geneva, Question: 29/XV
(Characteristics of digital systems on optical fiber cables for the
synchronous hierarchy), Nov. 20 to Dec. 1, 1989. .
Hasegawa et al., APS in a Sonet Ring Architecture, Contribution to
T1 Standards Project (T1X1.5/89-114), Jul. 20, 1989. .
Boehm et al., Reliability of a Self-healing SONET Ring
Architecture, Contribution to T1 Standards Project (TX1.5/90-065),
Apr. 20, 1990. .
Boehm et al., Overhead Usage for Protection Switching in a
Self-healing SONET Ring, Contribution to T1 Standards Project
(T1X1.5/90-066), Apr. 20, 1990. .
Constable, G.R., "Fiberoptic LANs: The System Integrator's
Perspective", Laser Focus, vol. 23, No. 3, Mar. 1987, pp. 112-120.
.
Yuji Takizawa et al., "Self-Healing Broadband SDH-Ring " 1990
Spring National Convention Record, The Institute of Electronics,
Information and Communication Engineers, Mar. 18-21, 1990, p. 3-130
(in Japanese with English Translation). .
H. Yamashita et al., "Flexible Synchronous Broad-Band Subscriber
Loop System: Optical Shuttle Bus", , Journal of Lightwave
Technology, vol. 7 No. 11, Nov. 1989, pp. 1788-1797. .
Japanese Search Report for Application JP-2-119524, mailed Jul. 29,
1997. .
European Search Report, The Hague, Dec. 19, 1991..
|
Primary Examiner: Le; Dieu-Minh T.
Attorney, Agent or Firm: Staas & Halsey
Claims
We claim:
1. A centralized control type ring network based on a synchronous
transport module transmission system, having a fault recovery
system for recovering a fault in said centralized control type ring
network, said centralized control type ring network comprising:
optical fiber transmission lines including a working line and a
protection line running in opposite directions to each other;
a plurality of drop/insert nodes connected to each other through
said optical fiber transmission lines;
a supervision node, connected through said optical fiber
transmission lines to said drop/insert nodes;
each of said drop/insert nodes having
input fault detecting means for detecting an input fault on the
working line or the protection line,
fault data writing means for writing, when said input fault is
detected by said input fault detecting means, fault data in a
predetermined user byte in an overhead of a frame flowing through
both of the working line and the protection line, and
user byte passing means for passing said user byte as is through
said node, when an input fault is not detected by said input fault
detecting means;
said supervision node having
fault data detecting means for detecting the fault data in said
user byte transmitted from the node which has detected said input
fault through the downstream sides of the working line and the
protection line of said node which has detected said input
fault;
fault position determining means for determining, based on said
fault data detected by said fault data detecting means, a node
which has detected said input fault;
writing means for writing, into said user bytes, loopback requests
for requesting nodes located immediately downstream and upstream of
the fault position and closest to said supervision node, to execute
loopback operations; and
sending means for sending said loopback requests through said
working line and said protection line to said nodes located
downstream and upstream of the fault position, whereby said nodes
located immediately downstream and upstream of the fault position
and closest to said supervision node execute loopback operations to
recover the fault.
2. A ring network as claimed in claim 1, wherein said synchronous
transport module transmission system is a system according to a
recommendation of CCITT G.707, 708, and 709.
3. A ring network as claimed in claim 1, wherein said fault data
includes a node identification number for identifying the node
which has detected the input fault.
4. A ring network as claimed in claim 1, wherein said fault data
includes fault line information indicating whether said input fault
has occurred on said working line or on said protection line.
5. A ring network as claimed in claim 4, wherein said fault data
includes fault reporting information.
6. A ring network as claimed in claim 4, wherein said loopback
requests are formed by rewriting said fault data to include a node
identification number of a node at which the loopback should be
executed, and loopback request information.
7. A ring network as claimed in claim 1, wherein said loopback
requests are formed by using another byte other than said
predetermined user byte in said overhead of said frame.
8. A ring network as claimed in claim 7, wherein said other type in
said overhead of said frame is the K1 byte or the K2 byte according
to a recommendation of CCITT G.707, 708, and 709.
9. A ring network as claimed in claim 1, wherein said writing means
includes rewriting means for rewriting said fault data transmitted
through said working line into a first loopback request and for
rewriting said fault data transmitted through said protection line
into a second loopback request, and said sending means through said
protection line and for sending said second loopback request to
said working line.
10. A ring network as claimed in claim 1, wherein said ring network
is a bidirectional ring network comprising a pair of clockwise and
counterclockwise working lines and a pair of counterclockwise and
clockwise protection lines.
11. A ring network as claimed in claim 10, comprising a plurality
of pairs of said working lines and a single pair of said protection
lines.
12. A distributed control type ring network based on a synchronous
transport module transmission system, having a fault recovery
system, said distributed control type ring network comprising:
optical fiber transmission lines including a working line and a
protection line running in opposite directions to each other;
a plurality of drop/insert nodes connected to each other through
said optical fiber transmission lines,
each of said drop/insert nodes having
input fault detecting means for detecting an input fault on the
working line or the protection line,
fault data and loopback request writing means for writing, when
said input fault is detected by said input fault detecting means,
fault data and a loopback request in a predetermined user byte in
an overhead of a frame flowing through both the working line and
the protection line.Iadd.,.Iaddend.
loopback executing means for executing, based on said fault data
detected by said fault data detecting means, a loopback when said
node is located immediately upstream of said input fault and
adjacent to a node which has not detected an input fault; and
said node executing said loopback returning, in response to said
loopback request, a loopback response by the use of said
predetermined user byte to said node which has detected said input
fault.
13. A ring network as claimed in claim 12, characterized in that
said synchronous transport module transmission system is the system
according to a recommendation of CCITT G.707, 708, and 709.
14. A ring network as claimed in claim 12, wherein said fault data
includes a node identification number for identifying the node
which has detected the input fault.
15. A ring network as claimed in claim 14, wherein said fault data
includes fault line information indicating whether said input fault
has occurred on said working line or on said protection line.
16. A ring network as claimed in claim 15, wherein said fault data
includes fault reporting information.
17. A ring network as claimed in claim 16, wherein said loopback
request is formed by rewriting said fault reporting information in
said fault data.
18. A ring network as claimed in claim 12, wherein said loopback
request is formed by using another byte other than said
predetermined user byte in said overhead of said frame.
19. A ring network as claimed in claim 18, wherein said other byte
in said overhead of said frame is the K1 byte or the K2 byte
according to a recommendation of CCITT G. 707, 708 and 709.
20. A ring network as claimed in claim 12, wherein said ring
network is a bidirectional ring network comprising a pair of
clockwise and counterclockwise working lines and a pair of
counterclockwise and clockwise protection lines.
21. A ring network as claimed in claim 20, comprising a plurality
of pairs of said working lines and a single pair of said protection
lines.
22. A hybrid type ring network based on a synchronous transport
module transmission system, having a fault recovery system, said
hybrid type ring network comprising:
optical fiber transmission lines including a working line and a
protection line running in opposite directions to each other;
and
a plurality of drop/insert nodes connected to each other through
said optical fiber transmission lines, each of said drop/insert
nodes including
input fault detecting means for detecting an input fault on the
working line or the protection line,
selecting means for dropping the input signal from said protection
line when the input signal from said working line is faulty, for
dropping the input signal from said working line when the input
signal from said protection line is faulty, and for dropping the
input signal from said working line when both are normal, and
passing the signal as is when the signal is not to be dropped;
fault data writing means for writing, when said input fault is
detected by said input fault detecting means, fault data in a
predetermined user byte in an overhead of a frame flowing through
both of the working line and the protection line; and
user type passing means for passing, when an input fault is not
detected by said input fault detecting means, said user byte as is
through said node.
23. A fault recovery system of a hybrid type ring network as
claimed in claim 22, characterized in that said synchronous
transport module transmission system is a system according to
.[.the.]. a recommendation of CCITT G. 707, 708, and 709.
24. A fault recovery system of a hybrid ring network as claimed in
claim 22, wherein said fault data includes a node identification
number for identifying the node which has detected the input
fault.
25. A fault recovery system of a hybrid ring network as claimed in
claim 22, wherein said fault data includes fault line information
indicating whether said input fault has occurred on said working
line or on said protection line..Iadd.
26. A node for communication through a ring network having a
plurality of nodes interconnected by first and second transmission
lines, the first transmission line transporting a transmission
signal frame including an overhead byte around the ring network in
a first direction and the second transmission line transporting a
transmission signal frame including an overhead byte around the
ring network in a second direction opposite to the first direction,
the node comprising:
detecting means for detecting a fault on an upstream side of the
first transmission line; and
transmitting means for transmitting to a downstream side of the
first transmission line, in response to the fault detected by said
detecting means, a request signal for directing a received
transmission signal frame from the upstream side of the first
transmission line to a downstream side of the second transmission
line by inserting the request signal onto the overhead byte of the
transmission signal frame..Iaddend..Iadd.
27. The node according to claim 26, wherein said transmitting means
transmits the request signal to the downstream sides of both of the
first and second transmission lines..Iaddend..Iadd.
28. The node according to claim 26, wherein the first transmission
line is a working line for the transmission signal frame and the
second transmission line is a protection line for the transmission
signal frame..Iaddend..Iadd.
29. The node according to claim 26, wherein said transmitting means
transmits, via the second transmission line, the request signal
addressed to an adjacent node connected thereto on the upstream
side of the first transmission line on which the fault is
detected..Iaddend..Iadd.
30. A node for communication through a ring network having a
plurality of nodes interconnected by first and second transmission
lines, the first transmission line transporting a transmission
signal frame including an overhead byte around the ring network in
a first direction and the second transmission line transporting a
transmission signal frame including an overhead byte around the
ring network in a second direction opposite to the first direction,
said node comprising:
a fault detector, to detect a fault on an upstream side of the
first transmission line; and
an overhead processor to insert, in response to the fault detected
by said fault detector, a request signal for directing a received
transmission signal frame from the upstream side of the first
transmission line to a downstream side of the second transmission
line onto the overhead byte of the transmission signal frame, and
to transmit the transmission signal frame to a downstream side of
the first transmission line..Iaddend..Iadd.
31. The node according to claim 30, wherein the overhead processor
transmits the transmission signal frame to the downstream side of
both the first transmission line and the second transmission
line..Iaddend..Iadd.
32. The node according to claim 30, wherein the first transmission
line is a working line for the transmission signal frame and the
second transmission line is a protection line for the transmission
signal frame..Iaddend..Iadd.
33. The node according to claim 30, wherein the overhead processor
inserts, onto the overhead byte, the request signal addressed to an
adjacent node connected thereto via the first transmission line on
the upstream side of which the fault is detected, and the second
transmission line..Iaddend..Iadd.
34. A node for communication through a ring network having a
plurality of nodes interconnected by first and second transmission
lines, the first transmission line transporting a transmission
signal frame including an overhead byte around the ring network in
a first direction and the second transmission line transporting a
transmission signal frame including an overhead byte around the
ring network in a second direction opposite to the first direction,
said node comprising:
receiving means for receiving the transmission signal frame from an
upstream side of the first transmission line;
detecting means for detecting a request signal to direct a received
transmission signal frame from the upstream side of the first
transmission line to the downstream side of the second transmission
line, the request signal inserted onto the overhead byte of the
received transmission signal frame and originated at a different
node detecting a fault on the first transmission line upstream of
the different node; and
directing means for directing, in response to the request signal
detected by said detecting means, a received transmission signal
frame from the upstream side of the first transmission lines to the
downstream side of the second transmission line..Iaddend..Iadd.
35. The node according to claim 34, wherein the first transmission
line is a working line for the transmission signal frame and the
second transmission line is a protection line for the transmission
signal frame..Iaddend..Iadd.
36. A node for communication through a ring network having a
plurality of nodes interconnected by first and second transmission
lines, the first transmission line transporting a transmission
signal frame including an overhead byte around the ring network in
a first direction and the second transmission line transporting a
transmission signal frame including an overhead byte around the
ring network in a second direction opposite to the first direction,
said node comprising:
a signal receiver to receive a transmission signal frame from an
upstream side of the first transmission line;
an overhead processor, operatively connected to the signal
receiver, to detect a request signal for directing a received
transmission signal frame from the upstream side of the first
transmission line to a downstream side of the second transmission
line, the request signal inserted onto the overhead byte of the
received transmission signal frame and originated at a different
node detecting a fault on the first transmission line upstream of
the different node; and
a route selector to direct a received signal frame from the
upstream side of the first transmission line to the downstream side
of the second transmission line in response to the request signal
detected by said overhead processor..Iaddend..Iadd.
37. The node according to claim 36, wherein the first transmission
line is a working line for the transmission signal frame and the
second transmission line is a protection line for the transmission
signal frame..Iaddend..Iadd.
38. A ring network, comprising:
a first transmission line for transporting a transmission signal
frame including an overhead byte around said ring network in a
first direction;
a second transmission line for transporting a transmission signal
frame including an overhead byte around said ring network in a
second direction opposite to the first direction; and
a plurality of nodes connected by said first and second
transmission lines, each node including:
a fault detector to detect a fault on an upstream side of said
first transmission line; and
an overhead processor to insert, in response to the fault detected
by said fault detector, a request signal for directing a
transmission signal frame received from the upstream side of said
first transmission line to a downstream side of said second
transmission line onto the overhead byte of the transmission signal
frame, and to transmit the transmission signal frame to the
downstream side of said first transmission line..Iaddend..Iadd.
39. A ring network, comprising:
a first transmission line for transporting a transmission signal
frame including an overhead byte around said ring network in a
first direction;
a second transmission line for transporting a transmission signal
frame including an overhead byte around said ring network in a
second direction opposite to the first direction; and
a plurality of nodes connected by said first and second
transmission lines, each node including:
a signal receiver to receive a transmission signal frame from an
upstream side of said first transmission line;
an overhead processor, operatively connected to said signal
receiver, to detect a request signal for directing a transmission
signal frame from the upstream side of said first transmission line
to a downstream side of said second transmission line, the request
signal inserted onto the overhead byte of the transmission signal
frame and originated at a different node detecting a fault on the
first transmission line upstream of the different node; and
a route selector to direct another signal frame from the upstream
side of said first transmission line to the downstream side of said
second transmission line in response to the detected request
signal..Iaddend..Iadd.
40. A method of recovering from a fault in a ring network having a
plurality of nodes interconnected by first and second transmission
lines, the first transmission line transporting a first
transmission signal frame including an overhead byte around the
ring network in a first direction and the second transmission line
transporting a second transmission signal frame including an
overhead byte around the ring network in a second direction
opposite to the first direction, comprising:
detecting a fault on an upstream side of the first transmission
line;
inserting a request signal for directing a transmission signal
frame received from the upstream side of the first transmission
line to a downstream side of the second transmission line onto the
overhead byte of the transmission signal frame in response to
detection of the fault; and
transmitting the transmission signal frame to the downstream side
of the first transmission line..Iaddend..Iadd.
41. The method according to claim 40, wherein said inserting
includes the step of addressing the request signal to a node
located immediately upstream along the first transmission line on
which the fault is detected..Iaddend..Iadd.
42. The method according to claim 40, wherein said transmitting
includes transmitting the transmission signal frame to the
downstream sides of both the first and the second transmission
lines..Iaddend..Iadd.
43. A method of recovering from a fault in a ring network having a
plurality of nodes interconnected by first and second transmission
lines, the first transmission line transporting a first
transmission signal frame including an overhead byte around the
ring network in a first direction and the second transmission line
transporting a second transmission signal frame including an
overhead byte around the ring network in a second direction
opposite to the first direction, comprising:
detecting a fault on an upstream side of the first transmission
line;
inserting a request signal for directing a transmission signal
frame received from the upstream side of the first transmission
line to a downstream side of the second transmission line onto the
overhead byte of the transmission signal frame in response to
detection of the fault;
transmitting the transmission signal frame to a downstream side of
the first transmission line;
receiving the transmission signal frame from the upstream side of
the first transmission line;
detecting the request signal from the overhead byte of the
transmission signal frame; and
directing the transmission signal frame from the upstream side of
the first the transmission line to the downstream side of the
second transmission line in response to detection of the request
signal..Iaddend..Iadd.
44. The method according to claim 43, wherein said inserting
includes addressing the request signal to a node located
immediately upstream along the first transmission line on which the
fault is detected..Iaddend..Iadd.
45. The method according to claim 43, wherein said transmitting
includes transmitting the transmission signal frame to the
downstream side of both the first and the second transmission
lines..Iaddend..Iadd.
46. A method of recovering from a fault in a ring network having a
plurality of nodes interconnected by first and second transmission
lines, the first transmission line transporting a first
transmission signal frame including an overhead byte around the
ring network in a first direction and the second transmission line
transporting a second transmission signal frame including an
overhead byte around the ring network in a second direction
opposite to the first direction, comprising:
receiving the transmission signal frame from an upstream side of
the first transmission line;
detecting a request signal to direct a received transmission signal
frame from the upstream side of the first transmission line to a
downstream side of the second transmission line, the request signal
inserted onto the overhead byte of the received transmission signal
frame and originated at a different node detecting a fault on the
first transmission line upstream of the different node; and
directing, in response to the request signal, the received
transmission signal frame from the upstream side of the first
transmission line to the downstream side of the second transmission
line..Iaddend.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fault recovery system of a ring
network, and more particularly to a fault recovery system of a ring
network based on a synchronous transport module (STM) transmission
system called a new synchronization system.
Ring networks based on the synchronous transport module (STM)
transmission system such as a synchronous digital hierarchy (SDH)
or synchronous optical network (SONET) the standardization of which
has been developed in the CCITT or United States T1 Committee, are
expected to be applied to subscriber systems (Urban Networks) in
the future. The STM transmission system is applied to a high speed
and broad band system of more than 155.52 Mbps. When a ring
network, based on such a STM transmission system which is a high
speed and broad band optical transmission system, is constructed,
the ability to survive a fault in the network is important and
should be considered from the beginning of the construction of the
system, since a network fault can have a great influence on the
transfer of information in a modern information society.
2. Description of the Related Art
As a conventionally proposed network fault recovery system, there
are recovery systems employing a loopback used in a local area
network (LAN) and so forth. These conventional recovery systems,
however, are networks based on packet communication through
predetermined protocols, and therefore, there are problems in that
it takes a long processing time of several seconds to recover from
a fault because the fault must be recovered by the use of the
above-mentioned predetermined protocols. Since the recovery time in
a new synchronization system should be shorter than, for example,
50 msec, a recovery method which uses these protocols cannot be
employed in a new synchronization system.
On the other hand, for point to point communication, the standard
usage of automatic protection scheme (APS) bytes (K1 and K2 bytes
in an STM frame) for a switching control between a working line and
a protection line has been recommended by the CCITT or the United
States T1 Committee. For application to a ring network, however,
standard usage has not been proposed.
A fault recovery system applied to a ring network is disclosed in
Japanese Patent Publication 1-45782, published on Oct. 4, 1989.
This fault recovery system, however, is not applied to the STM
transmission system. Further, in this document, if multiple faults
occur in the working line and the protection line, the positions of
the faults cannot be determined.
SUMMARY OF THE INVENTION
Accordingly, the present invention has an object to provide, based
on the synchronous transport module (STM) transmission system, a
system for rapidly and efficiently recovering a ring network even
when multiple faults occurs.
There is provided, according to the present invention, a
centralized control type ring network based on a synchronous
transport module transmission system, with a fault recovery system
for recovering a fault in the ring network. The ring network
provides optical fiber transmission lines including a working line
and a protection line running in opposite directions to each other,
a plurality of drop/insert nodes connected .[.to,.]. .Iadd.to
.Iaddend.each other through the optical fiber transmission lines
and a supervision node, connected through the optical fiber
transmission lines to the drop/insert nodes.
Each of the drop/insert nodes .[.has:.]. .Iadd.has .Iaddend.an
input fault detecting unit for detecting an input fault on the
working line or the protection line. A fault data writing unit is
also provided within each drop/insert node for writing, when the
input fault is detected by the input fault detecting unit, fault
data into a predetermined user byte within an overhead of a frame
flowing through both the working line and the protection line. A
user byte passing unit is also provided with each drop/insert node
for passing the user byte as is, when an input fault is not
detected by the input fault detecting unit, through the node.
The supervision node has a fault data detecting unit for detecting
the fault data in the user byte transmitted from the node which has
detected the input fault through the downstream sides of the
working line and the protection line of the node which has detected
the input fault. A fault position determining unit is also provided
within the supervision node for determining, based on the fault
data detected by the fault data detecting unit, a node which has
detected the input fault. A writing unit is also provided within
the supervision node for writing, into the user bytes, loopback
requests for requesting nodes located immediately downstream and
upstream of the fault position and closest to the supervision node,
to execute loopback operations. Finally, a sending unit for sending
the loopback requests through the working line and the protection
line to the nodes located immediately downstream and upstream of
the fault position and closest to the supervision node. Based on
this construction, the nodes located immediately downstream and
upstream of the fault position and closest to the supervision node
execute loopback operations to recover from the fault.
According to another aspect of the present invention, there is
provided a distributed control type ring network based on a
synchronous transport module transmission system, with a fault
recovery system for recovering a fault in the ring network. The
distributed control type ring network provides optical fiber
transmission lines including a working line and a protection line
running in opposite directions to each other. A plurality of
drop/insert nodes is also provided connected to each other through
the optical fiber transmission lines.
Each of the drop/insert nodes has an input fault detecting unit for
detecting an input fault on the working line or the protection
line. Each drop/insert node also has fault data and loopback
request writing unit for writing, when the input fault is detected
by the input fault detecting unit, fault data and a loopback
request into a predetermined user byte within an overhead of a
frame flowing through both the working line and the protection
line. A loopback executing unit is also provided within each
drop/insert node for executing, based on the fault data detected by
the fault data detecting unit, a loopback when the node is located
immediately upstream of the input fault and adjacent to a node
which has not detected an input fault. The node executing the
loopback returns, in response to the loopback request, a loopback
response by the use of the predetermined user byte to the node
which has detected the input fault.
Based on this construction, as in the construction described in the
previous aspect of the invention, the nodes located immediately
upstream of the fault position and adjacent to a node which has not
detected an input fault execute loopback operations to recover from
the fault.
Although the invention described herein can be provided in many
different forms of varying detail, without departing from the basic
concept and spirit of the invention, preferred details of the above
aspects of the prevent invention are described below.
It is preferable that the synchronous transport module transmission
system is a system according to the recommendation of CCITT G.707,
708, and 709.
It is preferable that the fault data includes a node identification
number for identifying the node which has detected the input
fault.
It is preferable that the fault data includes fault line
information indicating whether the input fault has occurred on the
working line or on the protection line.
It is preferable that the fault data includes fault reporting
information.
It is preferable that the loopback requests are formed by rewriting
the fault data to include a node identification number of a node at
which the loopback should be executed, and to include loopback
request information.
It is preferable that the loopback requests are formed by using
another byte within the overhead of the frame, other than the
predetermined user byte in the overhead of the frame.
It is preferable that the other byte in the overhead of the frame
is the K1 byte or the K2 byte according to the recommendation of
CCITT G.707, 708, and 709.
It is preferable that the writing unit has a rewriting unit for
rewriting the fault data transmitted through the working line into
a first loopback request and for rewriting the fault data
transmitted through the protection line into a second loopback
request, and that the sending unit has a unit for sending the first
loopback request through the protection line and for sending the
second loopback request to the working line.
It is preferable that the ring network is a bidirectional ring
network comprising a pair of clockwise and counterclockwise working
lines and a pair of counterclockwise and clockwise protection
lines.
It is preferable that the system comprises a plurality of pairs of
the working lines and a single pair of the protection lines.
According to still another aspect of the present invention, there
is provided a hybrid type ring network based on a synchronous
transport module transmission system, with a fault recovery system
for recovering a fault in the ring network. The hybrid type ring
network provides optical fiber transmission lines including a
working line and a protection line running in opposite directions
to each other, and a plurality of drop/insert nodes connected to
each other through the optical fiber transmission lines.
Each of the drop/insert nodes has a selecting unit for dropping the
input signal from the protection line when the input signal from
the working line is faulty, for dropping the input signal from the
working line when the input signal from the protection line is
faulty, and for dropping the input signal from the working line
when both are normal, and passing the signal as is when the signal
is not to be dropped.
BRIEF DESCRIPTION OF THE DRAWINGS
The above object and features of the present invention will be more
apparent from the following description of the preferred
embodiments with reference to the accompanying drawings,
wherein:
FIG. 1 is a format diagram of an overhead of the STM frame used in
a fault recovery system of a ring network according to the present
invention;
FIGS. 2A to 2C are principal construction diagrams of the fault
recovery system of a centralized control type ring network
according to an embodiment of the present invention;
FIGS. 3A to 3C are principal construction diagrams of the fault
recovery system of a distributed control type ring network
according to another embodiment of the present invention;
FIGS. 4A to 4D are diagrams showing examples of various ring
constructions used in the present invention;
FIG. 5 is a principal construction diagram of the fault recovery
system of a hybrid ring according to still another embodiment of
the present invention;
FIGS. 6A to 6C are diagrams for explaining an F1 byte in the
overhead used in the present invention;
FIG. 7 is a block diagram showing a construction example of a
drop/insert node and a supervision node constructing the
centralized control type or the distributed control type ring
according to the present invention;
FIGS. 8A to 8C are diagrams showing an example of a break in the
working line causing a fault in the centralized control type ring
according to still another embodiment of the present invention;
FIGS. 9A to 9C are diagrams showing an example of breaks in both
the working line and the protection line causing a fault in the
centralized control type according to still another embodiment of
the present invention;
FIGS. 10A to 10C are diagrams showing an example of when plural
faults occur in the centralized control type ring according to
still another embodiment of the present invention;
FIGS. 11A to 11C are diagrams showing an example when both the
working line and the protection line are cut causing a fault in the
distributed control type ring according to still another embodiment
of the present invention;
FIGS. 12A to 12C are diagrams showing an example of when plural
faults occur in the distributed control type ring according to
still another embodiment of the present invention;
FIG. 13 is a block diagram showing a construction example of each
drop/insert node in the hybrid ring used in the system of the
present invention; and
FIG. 14 is a diagram showing evaluations of various fault states in
the hybrid ring used in the system of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Currently, preparation is underway of international standardization
of the method of using the overhead bytes in the STM frame format
of the synchronous transport module (STM) transmission system. In
view of this, the inventors of the present invention have
considered using the overhead bytes for recovering faults in a ring
network.
Namely, FIG. 1 shows a frame format of the above-mentioned STM (in
particular the frame format of the STM-1), in which bytes labelled
A1, A2, B1, B2, C1, D1-D12, E1, E2, K1, and K2 respectively
represent bytes, usage of which is already internationally
standardized. The other labelled bytes, namely the F1 byte and Z1
and Z2 bytes have not yet been internationally standardized but are
determined to be used for domestic or national use. Note that the
remaining bytes are assigned for domestic use.
Accordingly, in the present invention, by using the unused bytes
such as the latter F1 byte or Z1 and Z2 bytes as user bytes (UB),
these bytes can be utilized to recover a fault in a ring network of
the new synchronization system (hereinafter simply referred to as a
ring network) constructed by optical fiber transmission lines
forming a working line (W) and a protection line (P) running in
opposite directions to each other.
In the Case of a Centralized Control Type Ring Network (FIGS. 2A to
2C)
This ring network, as shown in FIG. 2A, is constructed by
drop/insert nodes (nodes A-D for example in the figure, and
hereinafter also referred to simply as nodes), and a supervision
node SV. Throughout all the embodiments described in this
specification, it is assumed that all of the nodes are provided in
advance with node identification numbers. First, as shown in FIG.
2A, when an input fault F (marked by x) of a working line W (or a
protection line P as well) is detected by a node A by detecting a
clock signal error and so forth, the node A writes fault data FD in
a predetermined user byte UB in the overhead of each of the STM
frames flowing through the working line W and the protection line
P, and transmits the STM frames including the written fault data FD
to the downstream sides of the working line W and the protection
line P.
When the drop/insert node does not detect an input fault, it passes
the user bytes as they are to the supervision node SV, and
therefore, the fault data FD in the user bytes UB are transmitted
from the working line W and the protection line P.
The supervision node SV determines the position of the fault F by
detecting and analyzing the fault data, as shown in FIG. 2B, and
writes a loopback request LBR. The loopback request LBR requires
the nodes A and B located immediately downstream and upstream of
the fault position and closest to the supervision node SV, to
execute loopback operations, into the user byte UB. The written
loopback request LBR is transmitted through the protection line P
and through the node D to the node A. The loopback request LBR is
also transmitted through the working line W and through the nodes C
and D to the node B.
As a result, as shown in FIG. 2C, the loopbacks are executed by
these nodes A and B to recover the fault.
In this case, instead of utilizing the user byte UB for
transmitting the loopback request, it may be possible to transmit
the loopback request by using K1 and K2 bytes which are
internationally standardized. In this case, conformity with the
international standardization is achieved.
In the Case of a Distributed Type Ring Network (FIGS. 3A to 3C)
In this ring network, there is no supervision node, and the
respective drop/insert nodes are in an equal relation to each
other.
Accordingly, as shown in FIG. 3A, when the drop/insert node A
detects an input fault of the working line W (or of the protection
line P as well), it writes fault data FD including a loopback
request LBR into the user bytes UB in the STM frames of the working
line W and the protection line P. The user bytes UB including the
fault data FD and the loopback request LRB are transmitted to the
downstream sides of the working line W and the protection line
P.
In a similar way to that shown in FIG. 2A, the nodes C and D pass
the user bytes UB as they are. Among the respective nodes which
receive the fault data, the node B located immediately upstream of
the input fault and adjacent to the node C detects that there is a
fault position at the output side of the node B. As a result, as
shown in FIG. 3B, the node B executes the loopback operation and
returns the loopback request LBR to the node A which transmitted
the loopback requirement LBR.
When the node A receives the loopback request LBR, the node A
executes the loopback operation based on the returned loopback
request LBR so that, as shown in FIG. 3C, the loopback between the
nodes A and B is completed and the fault is restored.
Note, in either of the centralized control type or distributed
control type, not only the case is possible where the ring network
is constructed by a working line W and a protection line P
corresponding to each other in a 1:1 relation as shown in FIG. 4A,
but a unidirectional ring constructed by a plurality of working
lines and a single protection line (W1-W3 and P1 in FIG. 4B) is
also possible. A bidirectional ring is also possible which is
constructed by a pair of clockwise and counterclockwise working
lines W1 and W2 and a pair of counterclockwise and clockwise
protection lines P1 and P2 as shown in FIG. 4C. Further, the fault
can also be restored by constructing a bidirectional ring having a
plurality of pairs of working lines W1 to W6 and a single pair of
protection lines P1 and P2 as shown in FIG. 4D.
In the Case of a Hybrid-type Ring Network (FIG. 5)
In this case also, similar to the distributed control type shown in
FIGS. 3A to 3C, there is no supervision node, and therefore the
respective drop/insert nodes are in an equal relation to each
other. As shown in FIG. 5, when a fault occurs in a point between
the nodes A and B, the signal from the node A through the
downstream side of the working line W is transmitted through the
nodes D, E, and C until it is received by the node B. However, the
signal from the node A through the protection line P continues to
be transmitted through the loop if there is no countermeasure.
In the hybrid ring, a selecting unit is provided in each node for
selecting a signal to be dropped as follows. Namely, in each node,
if the input signal from the working line W indicates a fault, the
input signal from the protection line P is dropped; if the input
signal from the protection line P indicates a fault, the input
signal from the working line W is dropped; and if both input
signals are normal, the input signal from the working line W is
dropped. If, however, the channel should not be dropped, the input
signal is passed as it is.
In this case, similar to the case of FIGS. 2A to 2C and FIGS. 3A to
3C, when each node detects an input fault in the working line W or
the protection line P, fault data is written in the user bytes and
is transmitted downstream of the working line W and the protection
line P, and when an input fault is not detected, the user bytes are
passed as they are, whereby, in the case of FIG. 5, the fault state
between the nodes A and B can be evaluated with reference to the
user bytes UB.
In the following paragraphs, embodiments of a fault recovery system
of a ring network relating to the present invention are described
in more detail.
First, the F1 byte in the STM-1 frame format shown in FIG. 1 is
used as a predetermined user byte in the overhead used in the
system of the present invention. This byte however, may be the Z1
or Z2 byte assigned for national use, or may be one utilizing
various modifications.
FIG. 6A shows an embodiment of the F1 byte. In this embodiment,
bits b1 and b2 are assigned as indicators. When the bit b1 is "0",
the bit b1 indicates whether there is a fault on the working line;
and when b1 is "1", it indicates whether there is a fault on the
protection line. When the bit b2 is "0", the bit b2 indicates a
fault report; and if the bit b2 is "1", it indicates that the node
identification number of the node which should accept the loopback
request (protection switching) is being conveyed. Also, the bits
b3-b8 are assigned to the identification number of a node for
identifying the node relating to the fault.
In an F1 byte as above, since only 6 bits can be used as node
number data, when the number of nodes exceeds 2.sup.6 =64, it is
impossible to identify all nodes using the 6 bits. In this case,
two continuous bytes, a first F1 byte and a second F1 byte having,
all .[.total.]. .Iadd.total, .Iaddend.12 free bits as shown in FIG.
6B, may be utilized. The heading bit b1 of the first F1 byte is
defined as "0" so that the first F1 byte conveys fault data
relating to the working line W, and the heading bit b1 of the
second byte F1 is defined as "1" so that the second F1 byte conveys
fault data relating to the protection line P. These bytes are
respectively used for detecting faults on the working line P and
the protection line W. An example of the first F1 byte and the
second F1 byte is shown in FIG. 6C, wherein (1) shows that both the
working line and the protection line are in normal states, (2)
shows that the node "3" on the protection line has detected an
input fault because the bits b7 and b8 in the second F1 byte are
"1", and (3) shows that the node "1" on the working line has
detected an input fault because the bit b8 in the first F1 byte is
"1".
In the following description, for the sake of simplicity, the first
F1 byte and the second F1 byte are combined and indicated as F1
(#n,#k,S) as shown in FIG. 6D, where #n indicates a node number
which has detected a fault on the working line, #k indicates a node
number which has detected a fault in the protection line, and S
indicates whether the data indicates a fault report ("0") or a
loopback request ("1").
In the following, the fault recovery system in the above-described
respective rings will be described using the above-mentioned F1
byte.
Centralized Control Type Ring
FIG. 7 shows an embodiment of a drop/insert node or a supervision
node used in the centralized control type ring network, which is
constructed by a receiving unit 1 and a transmitting unit 3 for the
working line W, a receiving unit 4 and a transmitting unit 2 for
the protection line P, overhead processing units 5 and 6, and a
data drop/insert/pass processing unit 7. The receiving units 1 and
4 are respectively constructed by light receiving units 11 and 41
connected to the working line W and the protection line P for
converting light input signals into electrical signals, overhead
dropping units 12 and 42 for dropping the overhead from the
electrical signals to provide to the overhead processing units 5
and 6, and main signal processing units 13 and 43 for processing
main signals other than the overheads and for sending the dropped
and passed signals to the data drop/insert/pass processing unit 7.
The transmitting units 2 and 3 are respectively constructed by main
signal processing units 21 and 31 for processing the inserted and
passed signals from the data drop/insert/pass processing unit 7,
overhead inserting units 22 and 32 for inserting overheads from the
overhead processing units 5 and 6 into the inserted and passed
signals, and light transmitting units 23 and 33 for converting the
thus generated electric signals into light signals and for
transmitting them to the protection line P and the working line W,
respectively. Note, the process relating to the overhead is carried
out by the overhead processing units 5 and 6.
1 An Example of a Cut Causing a Fault in the Working line W (see
FIG. 8)
For the case when a fault is caused by a cut in the working line W
of an optical fiber between the node A and node B, the fault
recovery system of the present invention will now be described.
Referring to FIG. 8A, the node A, which has detected, by its light
receiving unit 11, the input fault of the working line W such as a
missing clock signal, loads the node identification number of the
node A on the F1 byte and transmits the F1 byte. In this case, a
fault data F1(A,-,0) and a loopback request K(W.fwdarw.P) are
transmitted from the node A to the downstream side of the working
line W through the communication between the overhead processing
units 5 and 6, and fault data F1(A,-,0) is also transmitted from
the node A to the downstream side of the protection line P through
the communication between the overhead processing units 5 and 6.
The loopback request K(W.fwdarw.P) is formed by rewriting the K1 or
K2 byte in the STM-1 frame format. Note that, the loopback request
K is, as described with reference to FIG. 1, internationally
standardized. Therefore, when the K1 or K2 byte is used for the
loopback request instead of using the S bit in the F1 byte, it
conforms with the international standardization. By contrast, when
the S bit (b2 in the F1 byte) is used for the loopback request, the
loopback request can also be executed, and therefore, the loopback
request K is not always used.
Since the node D is normal, it passes the F1 byte transmitted from
the node A through the working line W, and the nodes B and C pass
the F1 byte transmitted from the node A through the protection line
P. In each of the nodes D, B, and C, the input signal itself is
passed through the route in which the receiving unit 1, the data
drop/insert/pass processing unit 7, and the transmitting unit 3 are
connected.
Referring to FIG. 8B, the supervision node SV detects in its
overhead processing units 5 and 6 the fault data (F1 byte plus K
byte or F1 byte) transmitted from the node A through the working
line W and the protection line P, analyzes the new situation
including the fault data to determine the node A located
immediately downstream of the fault position and closest to the
supervision node SV, and transmits, to the protection line P, a
loopback request (instruction) K(W.fwdarw.K) and fault data F1
(A,A,1) requiring execution of a loopback at the node A and a fault
data F1(A,A,1). The supervision node SV also transmits a loopback
request K(W.fwdarw.P) and a fault data F1(B,B,1) requiring a
loopback be effected at the node B immediately upstream of the
fault position and closest to the supervision node SV. The node A
detects the loopback request from the supervision node SV, carries
out this loopback, and then returns a loopback response
K(W.fwdarw.P) and F1(A,A,1) through the working line W to the
supervision node SV. The node B also carries out the loopback, and
then returns a response K(W.fwdarw.P) and F1(B,B,1) to the
supervision node SV through the protection line P.
Referring to FIG. 8C, the supervision node SV receives the loopback
responses from the nodes A and B, and acknowledges that a fault
recovery route (loopback route) has been completed. After
completion of the fault recovery, the supervision node SV resets
the F1 byte to be all zeroes and transmits F1(-,-,0) to the working
line W and the protection line P. Accordingly, in a stationary
state where no fault occurs, the supervision node SV detects the
F1(A,-,0) from the working line W and F1(-,B,0) from the protection
line P.
2 An Example of Cuts Causing Faults in the Working Line W and the
Protection Line P (see FIGS. 9A to 9C)
For the case when faults caused by cuts in both the working line W
and the protection line P between the node A and the node B occurs,
the fault recovery system of the present invention is
described.
Referring to FIG. 9A, the node A, which has detected an input fault
on the working line W, transmits F1(A,-,0) and a loopback request
K(W.fwdarw.P) to the downstream side of the working line W, and
transmits F1(A,-,0) to the downstream side of the protection line
P; and the node B, which has detected the input fault on the
protection line P, transmits F1(-,B,0) to the downstream side of
the protection line P.
In this case, even if the F1(A,-,0) is transmitted from the node A
to the downstream side of the protection line P, it does not reach
the node B because the optical fiber of the protection line P
between the node A and the node B is cut. Similarly, even when
F1(-,B,0) is transmitted from the node B to the downstream side of
the working line W, F1(-,B,0) on the working line W does not reach
the node A because of the fiber cut (cut in W). Since the node D is
normal, it passes the F1 byte transmitted from the node A through
the working line W, and the node C passes the F1 byte transmitted
from the node B through the protection line P.
Referring to FIG. 9B, the supervision node SV detects the loopback
request K(W.fwdarw.P) and the fault data F1(A,-,0) transmitted from
the node A through the working line W, detects the fault data
F1(-,B,0) transmitted from the node B through the protection line
P, analyzes this new situation including the fault data to
determine the position of the fault, transmits a loopback request
K(W.fwdarw.P) requiring to loopback at the node A and F1(A,A,1) to
the downstream side of the protection line P, and transmits a
loopback request K(W.fwdarw.P) requiring a loopback at the node B
and F1(B,B,1) to the downstream side of the working line W.
The node A detects the loopback request from the supervision node
SV through the protection line P, carries out this loopback
operation, and then returns a response K(W.fwdarw.P) and F1(A,A,1).
The node B also carries out the loopback operation and then returns
a response K(W.fwdarw.P) and F1(B,B,1) to the supervision node
SV.
Referring to FIG. 9C, the supervision node SV acknowledges the
completion of a fault recovery route (loopback route) by receiving
the loopback responses from the nodes A and B. After the completion
of the fault recovery, the supervision node SV resets the F1 bytes
to be all zeroes and transmits them to the working line W and the
protection line P. Accordingly, in the stationary state in which
there is no fault in the ring network, the supervision node SV
detects the F1(A,-,0) from the working line W and the F1(-,B,0)
from the protection line P.
3 An Example of Plural Faults (see FIGS. 10A to 10C)
For the case when both the working line W and the protection line P
between the nodes A and B are cut and when the protection line P is
cut between the nodes D and A, the fault recovery system of the
present invention will be described.
Referring to FIG. 10A, similar to the above example shown in FIG.
9A, the node A transmits a loopback request K(W.fwdarw.P) and
F1(A,A,0) through the downstream side of the working line W to the
supervision node SV, and node B transmits fault data F1(-,B,0)
through the downstream side of the protection line P to the
supervision node SV.
Referring to FIG. 10B, the supervision node SV analyzes the new
situation including the fault state to determine the position of
the fault. Then the supervision node SV transmits a loopback
request K(W.fwdarw.P) requiring a loopback at the node D and
F1(D,D,1) to the downstream side of the protection line P, and
transmits a loopback request K(W.fwdarw.P) requiring to loopback at
the node B and F1(B,B,1) to the downstream side of the working line
W. Then, the node D detects the loopback request from the
supervision node SV, carries out this loopback operation, and
returns a response K(W.fwdarw.P) and F1(D,D,1) to the supervision
node SV. The node B also detects the loopback request from the
supervision node SV, carries out this loopback operation, and
returns a response K(W.fwdarw.P) and F1(B,B,1) to the supervision
node SV.
Referring to FIG. 10C, the supervision node SV acknowledges the
completion of a fault recovery route (loopback route) by receiving
the loopback responses from the nodes D and B. After the completion
of the fault recovery, the supervision node SV resets the F1 bytes
to be all zeroes and transmits them to the working line W and the
protection line P. Accordingly, in a stationary state in which
there is no fault, the supervision node SV detects F1(D,-,0) from
the working line W and F1(-,B,0) from the protection line P.
Distributed Control Type Ring
In this distributed control type ring network, there is no
supervision node, and the respective drop/insert nodes are placed
in an equal relation to each other. In this case also, the example
of the construction shown in FIG. 7 can be applied, and the
difference from the centralized control type ring is that, since
there is no supervision node, the F1 bytes are not reset by the
supervision node, and the others are processed in a similar way to
those in the centralized control type ring.
1 An Example of Cuts Causing Faults in the Working Line W and the
Protection Line P (see FIGS. 11A to 11C)
For the case when both the working line W and the protection line P
between the nodes A and B are cut, the fault recovery system of the
present invention will be described.
Referring to FIG. 11A, the node A which has detected a fault on the
working line W transmits F1(A,*,0) and a loopback request
K(W.fwdarw.P) to the downstream side of the working line W, and
transmits F1(A,*,0) to the downstream side of the protection line
P. In this case, in the initial state of the fault, there is a
possibility that the node A may not have been informed on the fault
on the protection line P because the fault on the protection line P
is at the output side of the node A, so that the node A may
transmit F1(A,*,0) to the downstreams of the working line W and the
protection line P. The node A, however, will have been informed of
the fault on the protection line P from the later received fault
data from the node B through the protection line P. After the node
A acknowledges the fault on the protection line P, the node A
transmits F1(A,B,-) to the downstream sides of the working line W
and the protection line P. In this case, * represents a time
dependent parameter. Note, in this case also, if the K bytes of the
loopback request are not used as mentioned before, a loopback
request to an other node is realized by changing the "0" in the
F1(A,*,0) to "1".
The node B which has detected a fault on the protection line P
transmits F1(*,B,0) of the F1 bytes containing the node
identification number of the node B, to the downstream sides of
both the working line W and the protection line P. In this case,
the F1(A,*,0) on the protection line P does not reach the node B
because of the cut fiber (P cut), and the F1(*,B,0) on the working
line W does not reach the node A because of the cut fiber (W cut).
The nodes D, E, and C pass the F1 byte transmitted from the node A
through the working line W, and the nodes C, E, and D pass the F1
byte transmitted from the node B through the protection line P.
Referring to FIG. 11B, the node B detects the loopback request
K(W.fwdarw.P) and the fault data including the F1(A,*,0)
transmitted from the node A through the working line W. By
analyzing the fault data F1(A,*,0), the node B recognizes that its
own node B is placed immediately upstream of the fault position,
i.e., just before the node A which has transmitted the fault data.
This recognition is possible because all of the nodes are provided
with their own node identification numbers in advance. Accordingly,
the fault on the protection line P between the nodes A and B is
determined so that a loopback operation is executed at the node B.
The node B then transmits a loopback response K(W.fwdarw.P) and
F1(A,B,0) through the protection line P to the node A.
Referring to FIG. 11C, the node A receives the loopback response
K(W.fwdarw.P) and the F1(A,B,0) from the node B through the
protection line P so that it determines the position of the fault
on the working line W between the nodes A and B. Then the node A
executes a loopback operation from the protection line P to the
working line W. In this way, it is recognized that the fault
recovery route (loopback route) has been completed, and, in a
stationary state after the fault recovery completion, the F1(A,B,0)
is transmitted through the working line W and the protection line
P.
3 An Example of Plural Faults (see FIGS. 12A to 12C)
For the case when faults occur due to cut in both the working line
W and the protection line P between the node A and the node B, and
a cut in the working line W between the nodes B and C, the fault
recovery system of the present invention will be described.
Referring to FIG. 12A, the node A transmits a loopback request
K(W.fwdarw.P) and F1(A,*,0) through the downstream side of the
working line W to the node C, and the node B transmits F1(B,B,0)
through the downstream side of the protection line P to the node A
since both the working line W and the protection line P are in
their input fault states.
Referring to FIG. 12B, the node C detects the fault on the working
line W between the node C and the node B based on the fault data
F1(B,B,0) transmitted from the node B through the protection line P
and the fault data F1(A,*,0) from the node A. The node C analyzes
this new situation, executes a loopback operation, and transmits a
loopback response K(W.fwdarw.P) and F1(A,C,0) to the node A through
the protection line P.
Referring to FIG. 12C, the node A, which receives this loopback
response K(W.fwdarw.P) and F1(A,C,0) from the node C, determines
the fault on the working line W between the nodes A and B. Then,
the node A executes the loopback operation at the node A to
complete the fault recovery route (loopback route). In the
stationary state after completion of the fault recovery completion,
F1(A,C,0) is transmitted through the working line W and the
protection line P.
Hybrid Ring
In this case also, there is no supervision node so that the
respective nodes have an equal relation to each other.
FIG. 13 schematically shows the construction of each node. In the
figure, the same reference as those in FIG. 7 represent the same
parts, and, also included are a selector 8 for selecting data to be
dropped or passed from or the receiving unit 1 or 4 to the data
drop/insert/pass processing unit 7, a distributing unit 9 for
distributing the inserted or passed data from the data
drop/insert/pass processing unit 7 to the transmitting units 2 or
3, and a control circuit 10 for controlling the selector 8. The
control circuit 10 selects a normal signal from the signals
received by the receiving units 1 and 4. When both are normal, the
control circuit 10 selects the receiving signal on the working line
W. However, the selector 8 is controlled only when the drop/insert
mode is effected for the corresponding channel which needs to be
dropped or inserted. In the case of another channel, namely, when
the channel is not to be dropped or inserted, the receiving units 1
and 4 and the transmitting units 3 and 2 are connected straight
through as illustrated in the figure by a dotted line. Note, the
discrimination of whether or not the signal is normal can be
carried out based on a cut in the input signal or by a lack of
frame synchronization. It may also be discriminated by an alarm
indication or a pointer indicating an abnormal in H1 and H2 pointer
bytes included in the overhead of the STM frame which is processed
by the overhead processing units 5 and 6.
Examples of faults in the hybrid ring using the node having such a
construction as described above, are illustrated in FIG. 14.
(1) An Example When the Working Line W Between the Nodes A and B is
Cut
In this case, as the F1 byte of the fault data, the F1 byte
F1(A,-,0) which is the same as the one shown in FIGS. 8A to 8C is
output from the nodes A and B (time t1). In the node A, since an
input fault occurs on the working line W, only the received signal
transmitted from the node D through the protection line P is
determined as normal and is received byte by byte. Also, in the
node B, the received signal from the node C through the working
line W and the received signal from the node A through the
protection line P are received as normal and are received byte by
byte. Therefore, the control circuit 10 in the node B switches the
selector 8 to receive with priority the received signal from the
working line W. Note, the other nodes C, D, and E only pass the
received signals on the working line W and the protection line
P.
After this, even at a time t2, after some time has passed from the
time t1, the state of the F1 byte is unchanged.
Thus, through the working line W and the protection line P, the
node A and the node B communicate with each other without
loopback.
Also, since the overhead is used in this case also, the fault
evaluation (of a cut in the working line W between the nodes A and
B) can be executed in a way similar to that mentioned above in the
nodes A and B.
(2) An Example When Both the Working Line W and the Protection Line
P Between the Nodes A and B are cut
In this case, the F1 bytes F1(A,-,0) and F1(-,B,0) as the fault
data, which are the same F1 bytes as shown in FIGS. 9A to 9C and
FIGS. 11A to 11C, are output from the nodes A and B, respectively
(time t1). The node A receives only the receiving signal
transmitted from the node D through the protection line P as a
normal signal because the input fault occurs on the working line W
between the nodes A and B, the node B receives only the receiving
signal transmitted from the node C through the working line W as a
normal signal because the input fault occurs on the protection line
P between the nodes A and B.
After this, at a time t2, since both the node A and the node B have
been informed, respectively, of the faults on the protection line P
and the working line W, the F1 bytes become F1(A,B,0) as
illustrated in FIG. 14(2).
Thus, through the working line W and the protection line P, the
node A and the node B communicate with each other without
loopback.
Also, through the use of the used byte in this case also, the fault
evaluation (of a cut in the working line W between the nodes A and
B) can be executed in the nodes A and B in a way similar to that
mentioned before.
(3) An Example When Both the Working Line W and the Protection Line
P Between the Nodes A and B are Cut and the Working line W between
the Nodes B and C is Cut
In this case, the F1 bytes F1(A,-,0) and F1(B,B,0) as the fault
data, which are the same F1 bytes as shown in FIGS. 10A to 10C and
FIGS. 12A to 12C, flow through the working line W and the
protection line P (time t1). The node A receives only the receiving
signal transmitted from the node D through the protection line P as
a normal signal because the input fault occurs on the working line
W between the nodes A and B, the node B cannot receive a signal
because the input faults occur on both the working line W and the
protection line P, and the node C receives with priority the
receiving signal transmitted from the node E through the working
line W as a normal signal.
At a time t2 after a certain amount of time has passed, the node A
detects the input fault of the node B so that the F1 byte F1(A,B,0)
as illustrated in the figure flows through the working line W.
Thus, through the working line W and the protection line P, the
nodes A and C communicate with each other without loopback.
In this case also, since the overhead is used, the fault evaluation
(of a cut in the working and protection lines between the nodes A
and B, and a cut in the working line W between the nodes B and C)
can be executed in the nodes A, B, and C in a way similar to that
mentioned before.
Thus, in the hybrid ring also, by applying the overhead, the
ability to respond to a fault in a ring (especially the case of a
plurality of faults or a catastrophic fault) can be increased.
As described above, according to the fault recovery system of a
ring network relating to the present invention, by utilizing a
predetermined user byte in the overhead of the STM frame used in
the synchronous transport module transmitting system, an input
fault detected in any node in a centralized control type ring,
distributed control type ring, or hybrid ring is transferred to
another node, whereby the supervision node or the drop/insert node
detects the position of the fault to execute a loopback operation
or a hybrid process. Therefore, since no protocol is used in the
fault recovery process, the fault can be recovered in a short
time.
* * * * *