Method and apparatus for identifying a failed span in a network of span interconnected nodes

• US 5,233,600 A
• Filed: 08/06/1990
• Issued: 08/03/1993
• Est. Priority Date: 08/06/1990
• Status: Expired due to Fees

• Current Assignee: Alcatel Network Systems India Limited (Nokia Corporation)
• Original Assignee: Alcatel Network Systems India Limited (Nokia Corporation)
• Inventors: Pekarske, Robert J.
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): MARCELO, MELVIN C
• Application Number:
  US07/562,785
• Time in Patent Office: 1,093 Days
• Field of Search: 370/13, 370/13.1, 370/14, 370/15, 370/16, 370/17, 370/110.1, 371/8.2, 371/11.2, 371/20.1, 371/20.2
• US Class Current: 370/228
• CPC Class Codes: H04J 3/14 Monitoring arrangements for SDH/SONET rings H04J3/085
• CPC Class Codes: H04M 3/2254 in networks
• CPC Class Codes: H04Q 3/0016 Arrangements providing connection between exchanges
• CPC Class Codes: H04Q 3/0079 involving restoration of networks, e.g. disaster recovery, self-healing networks

Abstract

A method is illustrated for identifying which one of a plurality of signal transmitting spans in a communication network of signal spans, such as bundles or sets of DS3 signals, has been interrupted by some type of failure. This identification is based on a local level knowledge, as opposed to prior art network level knowledge, by monitoring each circuit in a given span for either a directly observable signal impairment, or an alarm indication signal (AIS) and sending an IDLE whenever a directly observable signal impairment or an alarm indication signal is detected and declaring that the channel immediately upstream from that node has failed when either the directly observable signal impairment or the alarm indication signal is received for longer than a predetermined period of time. Such a determination as to the whereabouts of a failed span can then be used for other processes such as implementation of a network restoration scheme.

Claims

1. A method for identifying which span, in a distributed intelligence network having an arbitrary number of intelligent cross-connect switch nodes and an arbitrary number of spans interconnecting said nodes is the site of a break in communications, each said span having working circuits between nodes designated for transmitting actual communications traffic and some of said spans having spare circuits between nodes capable of, but not designated for, transmitting actual communications traffic, at least some of said spans including circuitry for detecting a DOSI (directly observable signal impairment) and for outputting an AIS (alarm indication signal) signal to nodes downstream in response to such detection of DOSI, said method comprising the steps of each node:

a) periodically monitoring each circuit received in a given span for either a DOSI or an AIS signal;

b) sending an IDLE signal downstream whenever a DOSI or an AIS signal is detected and timing the period of detection of said DOSI or said AIS signal; and

c) declaring failure of the channel in the span immediately upstream from said node when either a DOSI or an AIS signal is detected for longer than a predetermined period of time.

2. A method for identifying which circuit bundle, in a distributed intelligence network having an arbitrary number of intelligent nodes and an arbitrary number of circuit bundles interconnecting said nodes, is the site of a break in communications, each said circuit bundle having working circuit channels between nodes designated for transmitting actual communications traffic and some of said circuit bundles having spare circuit channels between nodes capable of, but not designated for, transmitting actual communications traffic, at least some of said circuit bundles including circuitry for detecting DOSI (directly observable signal impairment) and for outputting a signal having a first format to nodes downstream in response to such detection of DOSI, said method comprising the steps of each node:

a) monitoring each circuit channel received in a given circuit bundle for DOSI or a signal having a first format;

b) sending a second format signal downstream whenever a DOSI or a received signal of the first format is detected and timing the period of detection of said DOSI or said signal having the first format; and

c) declaring failure of the channel in the circuit bundle immediately upstream from said node and which contains the circuit in question when either a DOSI or a signal having said first format is detected for longer than a predetermined period of time.

3. A signaling system comprising, in combination:

a plurality of cross connect switch nodes;

communication signal carrying circuit bundles interconnecting said nodes at least some of which circuit bundles include both spare and working circuit channels;

first means, contained within at least some of said circuit bundles, for detecting DOSI (directly observable signal impairment of received signal) and for outputting a given format first signal to nodes downstream in response to such detection of DOSI;

second means, comprising a part of each one of said switch nodes, for monitoring each circuit channel received in a given circuit bundle for DOSI or a signal having said given format;

third means, comprising a part of each one of said switch nodes, for sending a signal having a further format downstream whenever a DOSI or a signal of the given format is detected and for timing the period of reception of said DOSI or said signal having the given format; and

fourth means, comprising a part of each one of said switch nodes, for declaring failure of the channel in the circuit bundle immediately upstream from said node and which contains the circuit in question when either a DOSI indication, or a signal having said given format is received by said node for longer than a predetermined period of time.

4. A signal switching node for use in a communication system including a plurality of switching nodes for handling and redistributing received traffic obtained via communication signal carrying circuit bundles interconnecting said nodes where at least some of said circuit bundles include intelligent devices to detect upstream DOSI (directly observable signal impairment of received signal) to output a given format first signal downstream in response to such detection comprising, in combination:

first means for monitoring each circuit channel received on a given circuit bundle for DOSI or a signal having a given format;

second means for sending a signal having a second format downstream whenever a DOSI is detected and for timing the period of detection of the DOSI;

third means for sending the second format signal downstream whenever a signal of the given format is detected and for timing the period of reception of said signal having said given format; and

fourth means for broadcasting a third format signal to other signal switching nodes in the communication system declaring failure of a circuit channel in the circuit bundle immediately upstream from said node when either a DOSI or a signal having said given format is received by said node for longer than a predetermined period of time.

5. A method for identifying that a failure has occured immediately upstream from a given intelligent node, in a distributed intelligence network having an arbitrary number of similarly operating intelligent nodes and an arbitrary number of circuit bundles interconnecting said nodes, each said circuit bundle having working circuit channels between nodes designated for transmitting actual communications traffic and some of said circuit bundles having spare circuit channels between nodes capable of, but not designated for, transmitting actual communications traffic, at least some of said circuit bundles including circuitry for detecting DOSI (directly observable signal impairment) and for outputting a signal having a first format to nodes downstream in response to such detection of DOSI, said method comprising the steps of:

a) monitoring each circuit channel received in a given circuit bundle of a network of multi-circuit channel circuit bundle interconnected intelligent nodes for DOSI or an signal having a first format;

b) sending a signal having a second format downstream whenever a DOSI or a received signal of the first format is detected and timing the period of detection of said DOSI or said signal having the first format; and

d) declaring failure of the channel in the circuit bundle immediately upstream from said node and which contains the circuit in question when either a DOSI or a signal having the first format is received for longer than a predetermined period of time.

6. A signal switching node for use in a communication system including a plurality of identical switching nodes comprising, in combination:

first means for receiving a plurality of upstream signal circuit channels as part of a given circuit bundle in a communication system;

second means for outputting a like plurality of circuit channels as part of at least one downstream circuit bundle in the communication system;

third means for monitoring each circuit channel received for a DOSI (directly observable signal impairment) or an AIS signal having a first format;

fourth means for sending an IDLE second format signal downstream whenever a DOSI or an AIS signal of the first format is detected;

fifth means for timing the period of detection of DOSI or of said AIS signal having the first format; and

sixth means for declaring failure of a circuit channel in the circuit bundle immediately upstream from said node when either

a) a DOSI is detected for longer than a predetermined period of time, or

b) an AIS signal having the first format is received by said node for longer than a predetermined period of time.