EP0752178A1 - Protection scheme for sdh add/drop multiplexer - Google Patents
Protection scheme for sdh add/drop multiplexerInfo
- Publication number
- EP0752178A1 EP0752178A1 EP95911448A EP95911448A EP0752178A1 EP 0752178 A1 EP0752178 A1 EP 0752178A1 EP 95911448 A EP95911448 A EP 95911448A EP 95911448 A EP95911448 A EP 95911448A EP 0752178 A1 EP0752178 A1 EP 0752178A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- card
- tributary
- protection
- faulty
- cards
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 230000005540 biological transmission Effects 0.000 description 2
- 230000003139 buffering effect Effects 0.000 description 1
- 238000012790 confirmation Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 230000002688 persistence Effects 0.000 description 1
- 230000001360 synchronised effect Effects 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J3/00—Time-division multiplex systems
- H04J3/02—Details
- H04J3/14—Monitoring arrangements
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J3/00—Time-division multiplex systems
- H04J3/02—Details
- H04J3/08—Intermediate station arrangements, e.g. for branching, for tapping-off
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J2203/00—Aspects of optical multiplex systems other than those covered by H04J14/05 and H04J14/07
- H04J2203/0001—Provisions for broadband connections in integrated services digital network using frames of the Optical Transport Network [OTN] or using synchronous transfer mode [STM], e.g. SONET, SDH
- H04J2203/0057—Operations, administration and maintenance [OAM]
- H04J2203/006—Fault tolerance and recovery
Definitions
- the system is one which operates on the synchronous digital hierarchy (S.D.H.) and
- AdMux add drop multiplexer
- the multiplex controller being arranged to switch signals from
- the switching between cards may be done automatically under the control of the multiplex controller or altematively it may be hand controlled. In the latter case it will be controlled via a suitable management interface of the network.
- the arrangement is preferably such that when the faulty tributary card has been replaced, the controller will switch out the protection card and revert to the use of the tributary card.
- switching is preferably
- switch unit protection mechanism or to prevent an indication of switch unit failure in the case of an unprotected switch unit, the maximum duration of any disruption of traffic from the output of the switch unit, due to switching between tributary cards, will be within the
- the figure shows the tributary cards “1” to “n” and a protection card “10".
- Each of the tributary cards is connected to a line termination unit (LTU) respectively "11", "12”,
- the protection card "10” is connected to its own LTU "20".
- Each of the LTU's is connected to a multiplex controller "21”, as shown, and each of the LTU's, apart from the
- LTU 20 has a switching mechanism which is connected to a protection bus "23" so that the
- LTU "20" can be switched through to one of the other appropriate LTU's. Each of the units also has an output port.
- any plesiochronous digital hierarchical signal (P.D.H.) received on an LTU can be routed either directly to the card associated with the LTU or to the protection bus "23". All switching is under the control of the controller "21" and operation of the switch automatically disconnects the rest of the protection bus to the left of the card being protected, as viewed in fig. 1.
- the related protection termination unit is inserted. This unit connects the protection
Landscapes
- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Time-Division Multiplex Systems (AREA)
- Detection And Prevention Of Errors In Transmission (AREA)
- Monitoring And Testing Of Exchanges (AREA)
Abstract
An SDH telecommunications system includes a plurality of tributary cards through which signals are switched, a protection card is included for the tributary cards and a multiplex controller controls the output of a plurality of line termination (LTU's) units there being one unit provided respectively for each tributary card including the protection card, the multiplex controller being arranged to switch signals from a faulty tributary card to the protection card through the LTU associated with the faulty tributary card but without involving any switching taking place within the faulty tributary card so as to effectively replace the faulty tributary card.
Description
PROTECTION SCHEME FOR SDH ADD/DROP MULTIPLEXER
This invention relates to a telecommunications system protection scheme for
protecting tributary cards in the system and enabling them to be replaced when faulty.
The system is one which operates on the synchronous digital hierarchy (S.D.H.) and
the information is transmitted in bit form in a series of bytes of information. The
information is sent at 34/45 and 140 megabit levels and incorporates the add drop multiplexer system. This is usually referred to as an AdMux. The invention is intended as a protection scheme against card failure and as a maintenance tool to minimize disruption of tributary traffic during tributary card replacement. The mechanism should not affect the
external traffic interfaces and protection is provided only for the tributary cards and with signals being supplied to and received from the same traffic ports before and after switching between cards.
According to the present invention a SDH telecommunications system includes a plurality of tributary cards through which signals are switched, a protection card is included for the tributary cards and a multiplex controller controls the output of a plurality of line termination (LTU's) units there being one unit provided respectively for each tributary card
including the protection card, the multiplex controller being arranged to switch signals from
a faulty tributary card to the protection card through the LTU associated with the faulty tributary card but without involving any switching taking place within the faulty tributary card so as effectively to replace the faulty tributary card.
Thus the protection switching is effected without any involvement of the failed card. The present invention thus guarantees the successful operation of the protection system
irrespective of the failure mode of the tributary card. This would not be the case where the
protection operation pretended upon some functional involvement of the faulty tributary
card.
The switching between cards may be done automatically under the control of the multiplex controller or altematively it may be hand controlled. In the latter case it will be controlled via a suitable management interface of the network.
The arrangement is preferably such that when the faulty tributary card has been replaced, the controller will switch out the protection card and revert to the use of the tributary card.
In this invention it is necessary that for automatic operation, the protection switching shall be performed on the following internally detected criteria, the following of which are examples :-
(a) internal interface check disparity errors
(b) failure to respond to control poll (c) failure of control bus protocol checks
(d) maturing of on-card watchdog timer
(e) on-card program checksum error
(f) failure of on-card ASIC poll cycle
(g) ASIC internal buffer overflow/underflow
In order that the protection switching, whether it is automatic or manual, takes place
correctly, the following sequence of events has to be followed:-
1 the switch card protection must be disabled to the protection card
2 traffic is duplicated to the protection card
3 the protection card is down-loaded with its configuration
4 the output buffer on the failed card is disabled and the associated LTU is switched.
5 the protection output buffer on the buffering card is then enabled.
It will be appreciated that there will be some delay in the transmission of
information during the switching from a faulty tributary card to the protection card. If the system is operated on automatic control under the control of the multiplex controller, normally such switching should be completed within 3 seconds of detection of a fault condition at the tributary card. With manual operation however, switching is preferably
completed within 8 seconds, which is the time measured from the entry of the command at
the appropriate interface to the confirmation to the operator.
It will be appreciated that during the period in which the selected input traffic is
switched over, errors will be generated in the container bytes. For compatibility with the
switch unit protection mechanism, or to prevent an indication of switch unit failure in the case of an unprotected switch unit, the maximum duration of any disruption of traffic from
the output of the switch unit, due to switching between tributary cards, will be within the
persistence check period of the switch diagnostic message check.
In order that the invention may be readily understood, one example of the switching system architecture embodying the invention will now be described, with reference to the
single figure of the accompanying drawings which show in diagrammatic form the
connections between the tributary cards being protected and the multiplex controller.
The figure shows the tributary cards "1" to "n" and a protection card "10". Each of the tributary cards is connected to a line termination unit (LTU) respectively "11", "12",
"In", and the protection card "10" is connected to its own LTU "20". Each of the LTU's is connected to a multiplex controller "21", as shown, and each of the LTU's, apart from the
LTU 20, has a switching mechanism which is connected to a protection bus "23" so that the
LTU "20" can be switched through to one of the other appropriate LTU's. Each of the units also has an output port. Thus any plesiochronous digital hierarchical signal (P.D.H.) received on an LTU can be routed either directly to the card associated with the LTU or to the protection bus "23". All switching is under the control of the controller "21" and operation of the switch automatically disconnects the rest of the protection bus to the left of the card being protected, as viewed in fig. 1.
In this example there are five protection buses, three for 34/45 megabits, one for 34 megabit transmux, and one for 140 megabit signals. The "a" connections on the termination units of the 34 megabit cards are connected to the 34 megabit protection bus "1" and the "b"
terminals to the 34 megabit protection bus "2", etc. The 140 megabit card will only use the
termination terminal "d" which has access to the 140 megabit protection bus. The 34
megabit transmux card will use the termination unit, terminal "a". The protection card "10"
is located in the slot in the switching assembly immediately to the right of the tributary
cards "1" to "n" to be protected. In the termination unit slot associated with the protection
card, the related protection termination unit is inserted. This unit connects the protection
bus to the inputs and outputs of the protection card.
It will be appreciated that in operation one of the tributary cards, "1" to "n", will be immediately switched out of action and the protection card will be switched into circuit. The protection card "10" will then route via the unit "20" onto the appropriate protection
bus "23" to the relevant LTU so that transmission can continue. This provides an effective
and swift re-routing of signals and enables the protection to operate so that the system is not out of action while a working card is changed. When the working card has been replaced the system automatically changes back and the protection card "10" is cut out of operation.
Claims
1. A SDH telecommunications system including a plurality of tributary cards through
which signals are switched, a protection card is included for the tributary cards and a
multiplex controller controls the output of a plurality of line termination (LTUs) units there
being one unit provided respectively for each tributary card including the protection card, the multiplex controller being arranged to switch signals from a faulty tributary card to the protection card through the LTU associated with the faulty tributary card but without involving any switching taking place within the faulty tributary card so as effectively to replace the faulty tributary card.
2. A telecommunications system as claimed in Claim 1 in which there are means to automatically effect the switching between the cards.
3. A telecommunications system as claimed in Claim 1 in which there are means to enable manual control of the switching between the cards.
4. A telecommunications system having the arrangements substantially as hereinbefore described with reference to the accompany drawing.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9405771A GB9405771D0 (en) | 1994-03-23 | 1994-03-23 | Telecommunications system protection scheme |
| GB9405771 | 1994-03-23 | ||
| PCT/GB1995/000618 WO1995026084A1 (en) | 1994-03-23 | 1995-03-21 | Protection scheme for sdh add/drop multiplexer |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| EP0752178A1 true EP0752178A1 (en) | 1997-01-08 |
Family
ID=10752383
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP95911448A Withdrawn EP0752178A1 (en) | 1994-03-23 | 1995-03-21 | Protection scheme for sdh add/drop multiplexer |
Country Status (7)
| Country | Link |
|---|---|
| EP (1) | EP0752178A1 (en) |
| JP (1) | JPH09510589A (en) |
| CN (1) | CN1146836A (en) |
| AU (1) | AU689557B2 (en) |
| GB (2) | GB9405771D0 (en) |
| WO (1) | WO1995026084A1 (en) |
| ZA (1) | ZA952347B (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SE504533C2 (en) * | 1995-06-01 | 1997-03-03 | Ericsson Telefon Ab L M | Demultiplexer, protective switching unit, telecommunications network and method of demultiplexing |
| SE504521C2 (en) * | 1995-06-01 | 1997-02-24 | Ericsson Telefon Ab L M | Multiplexer, protective switching unit, telecommunication network and method of multiplexing |
| US6925052B1 (en) | 1999-10-01 | 2005-08-02 | Agilent Technologies, Inc. | Multi-channel network monitoring apparatus, signal replicating device, and systems including such apparatus and devices, and enclosure for multi-processor equipment |
| GB2394849A (en) * | 1999-10-01 | 2004-05-05 | Agilent Technologies Inc | Multi-channel replicating device for broadband optical signals, and systems including such devices |
| CN101136711B (en) * | 2007-09-29 | 2011-11-23 | 中兴通讯股份有限公司 | Optical terminal service, clock, cross service high integration veneer service smooth switch system of SDH system |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2266644A (en) * | 1992-04-25 | 1993-11-03 | Plessey Telecomm | Overhead transmissions in a data communication system |
| GB9311106D0 (en) * | 1993-05-28 | 1993-07-14 | Plessey Telecomm | Switch plane maintenance |
-
1994
- 1994-03-23 GB GB9405771A patent/GB9405771D0/en active Pending
-
1995
- 1995-03-20 GB GB9505559A patent/GB2290432B/en not_active Expired - Fee Related
- 1995-03-21 WO PCT/GB1995/000618 patent/WO1995026084A1/en not_active Application Discontinuation
- 1995-03-21 AU AU19019/95A patent/AU689557B2/en not_active Ceased
- 1995-03-21 JP JP7524481A patent/JPH09510589A/en active Pending
- 1995-03-21 EP EP95911448A patent/EP0752178A1/en not_active Withdrawn
- 1995-03-21 CN CN95192715A patent/CN1146836A/en active Pending
- 1995-03-22 ZA ZA952347A patent/ZA952347B/en unknown
Non-Patent Citations (1)
| Title |
|---|
| See references of WO9526084A1 * |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2290432A (en) | 1995-12-20 |
| ZA952347B (en) | 1995-12-15 |
| CN1146836A (en) | 1997-04-02 |
| GB9505559D0 (en) | 1995-05-03 |
| JPH09510589A (en) | 1997-10-21 |
| GB2290432B (en) | 1998-06-10 |
| AU689557B2 (en) | 1998-04-02 |
| AU1901995A (en) | 1995-10-09 |
| GB9405771D0 (en) | 1994-05-11 |
| WO1995026084A1 (en) | 1995-09-28 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
| 17P | Request for examination filed |
Effective date: 19961015 |
|
| AK | Designated contracting states |
Kind code of ref document: A1 Designated state(s): BE DE ES FR IE IT NL |
|
| 17Q | First examination report despatched |
Effective date: 19980303 |
|
| STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN |
|
| 18D | Application deemed to be withdrawn |
Effective date: 19980714 |