WO2000069148A2

WO2000069148A2 - Telecommunications system failure recovery

Info

Publication number: WO2000069148A2
Application number: PCT/IL2000/000229
Authority: WO
Inventors: Tomer Tankel; Shimon Yannay
Original assignee: Tundo Communication And Telephony Ltd.
Priority date: 1999-05-11
Filing date: 2000-04-18
Publication date: 2000-11-16
Also published as: WO2000069148A3; AU3985900A

Abstract

A telephony system including a data network, a plurality of telephony devices each operatively associated with the data network and operative to request telephony services, via the data network, in accordance with a telephony protocol, at least two telephony switches including a first telephony switch and a second telephony switch, each of the at least two telephony switches being operatively associated with the data network and operative to fulfill telephony service requests received via the data network in accordance with the telephony protocol and each including a system information database, the system information database being operative to store configuration information defining a plurality of characteristics of each of the telephony devices. The first telephony switch includes a first data replication subsystem operative to replicate the stored configuration information to the system information database included in the second telephony switch. Related apparatus and methods are also provided.

Description

TELECOMMUNICATIONS SYSTEM FAILURE RECOVERY FIELD OF THE INVENTION

The present invention relates to telephony systems, and in particular to apparatus

and methods for providing recovery from failures in telephony systems.

BACKGROUND OF THE INVENTION

Telephony switches are well known in the art. Typical prior art telephony switches

which might be used on private premises, as opposed to being used as part of the

public switched telephone network (PSTN), include switches available from Lucent

Technologies and the AS5300 switch available from Cisco. Telephony switches are

generally used to provide telephony services to end units such as conventional

telephones, the services typically including basic services such as call establishment,

routing of calls to other switches or to the PSTN, and other well known services.

Advanced services may also be included, as is well known in the art.

One example of a prior art protocol which can be used in a telephony system

including telephone switches is the H.323 v. 2 protocol of the International

Telecommunications Union (ITU), published in 1998.

The problem of failure of a telephony system component, such as a telephony

switch, is well known in the art. When a switch fails, various problems typically occur,

including: inability of the switch to receive calls; loss of existing calls; inability of

establishing new calls; long failure periods; and inability to recover in case of a site

disaster.

Existing solutions to the problem of switch failure are typically based on the use of a a shadow switch, including a backup switch which shadows ongoing operations and,

at the time of failure, takes over for the failed switch. Generally, shadow machines are

limited by a maximum physical distance from the master machine. In a case where a shadow machine is limited to be at the same physical location as the main machine, the shadow machine may also become inoperative in the case of a physical disaster. Generally, failure detection and recovery time for prior art shadow based systems is

approximately 10 minutes.

Technologies related to those of the present invention are described in a co-pending

application entitled ''System for Building a Telephony Application", filed on the same

day as the present application, having the same inventors and assigned to the same

assignee as the present application. The "System for Building a Telephony

Application" application is hereby incorporated herein by reference.

The disclosures of all references mentioned above and throughout the present

specification are hereby incorporated herein by reference.

SUMMARY OF THE INVENTION

The present invention seeks to provide an improved telephony system. In one preferred embodiment of the present invention, an improved telephony system

including an improved telephony switch is provided. In another preferred

embodiment, the telephony switch may be provided alone.

In the present invention, a disaster recover mechanism which does not require the

use of redundant shadow machines is provided. In the present invention, one switch

uses peer-to-peer communication, as is well known in the art, to redundantly store

important system information relating to the one switch on another active switch. In

case of a failure of the first switch, operation is moved to the second switch, using the

redundant stored information in the second switch or in another appropriate location.

Preferably, failures are detected using a keep-alive system.

There is thus provided in accordance with a preferred embodiment of the present

invention a telephony system including a data network, a plurality of telephony

devices each operatively associated with the data network and operative to request

telephony services, via the data network, in accordance with a telephony protocol, at

least two telephony switches including a first telephony switch and a second telephony

switch, each of the at least two telephony switches being operatively associated with

the data network and operative to fulfill telephony service requests received via the

data network in accordance with the telephony protocol and each including a system

information database, the system information database being operative to store

configuration information defining a plurality of characteristics of each of the

telephony devices, wherein the first telephony switch includes a first data replication

subsystem operative to replicate the stored configuration information to the system information database included in the second telephony switch.

Further in accordance with a preferred embodiment of the present invention the

second telephony switch includes a second data replication subsystem operative to

replicate the stored configuration information to the system information database

included in the first telephony switch.

Still further in accordance with a preferred embodiment of the present invention the

at least two telephony switches also includes a third telephony switch, and the second

telephony switch includes a second data replication subsystem operative to replicate

the stored configuration information to the system information database included in

the third telephony switch.

Additionally in accordance with a preferred embodiment of the present invention

the telephony protocol includes H.323.

There is also provided in accordance with another preferred embodiment of the

present invention a telephony switch for use in a telephony system including a data

network and a plurality of telephony devices each operatively associated with the data

network and operative to request telephony services, via the data network, in

accordance with a telephony protocol, the telephony switch including a network

adapter operative to provide communications via a data network between the

telephony switch and a plurality of telephony devices and to receive telephony service

requests from the telephony devices, a system information database, the system

information database being operative to store configuration information defining a

plurality of characteristics of each of the telephony devices, and a first data replication

subsystem operative to replicate the stored configuration information to a second

system information database external to the telephony switch. Further in accordance with a preferred embodiment of the present invention the

second system information database external to the telephony switch is included in a second telephony switch.

telephony protocol includes H.323.

There is also provided in accordance with another preferred embodiment of the

present invention a method for providing recovery in a telephony system after the

failure of a telephony switch included in the system, the method including providing a

first telephony switch having an internal switch database for storing information and

replication capability to replicate the stored information in another database external to

the telephony switch, operating the first telephony switch, including storing system

information in the internal switch database, replicating the stored system information

to an external database external to the first telephony switch, detecting failure of the

first telephony switch, in response to a result of the detecting step, failing over

operations of the first telephony switch to a second telephony switch, using replicated

system information in the external database.

Further in accordance with a preferred embodiment of the present invention the

second telephony switch is selected based, at least in part, on a load of the second

telephony switch, from a plurality of available telephony switches.

method also includes performing load balancing between the second telephony switch

and at least one other telephony switch.

Additionally in accordance with a preferred embodiment of the present invention

the step of detecting failure includes detecting failure using a keep-alive count. Moreover in accordance with a preferred embodiment of the present invention the external database is included in the second telephony switch.

There is also provided in accordance with another preferred embodiment of the present invention a method for use in a telephony system including a data network and

a plurality of telephony devices each operatively associated with the data network and

operative to request telephony services, via the data network, in accordance with a

telephony protocol, the method including providing communications via a data

network between a telephony switch and a plurality of telephony devices and receiving

telephony service requests from the telephony devices, storing configuration

information defining a plurality of characteristics of each of the telephony devices, and

replicating the stored configuration information to a backup system information

database.

Further in accordance with a preferred embodiment of the present invention the

storing step includes storing in a system information database included in a first

telephony switch.

backup system information database is included in a second telephony switch.

Additionally in accordance with a preferred embodiment of the present invention

the telephony protocol includes H.323.

There is also provided in accordance with another preferred embodiment of the

present invention, in a telephony system operative to provide failover of a telephony

switch upon failure of the telephony switch to update a keep-alive count, a load

balancing method comprising providing a plurality of telephony switches, identifying

one of the plurality of telephony switches as an overloaded telephony switch, and failing to respond to at least one keep-alive message directed to the overloaded telephony switch, thus causing at least one device associated with the overloaded

telephony switch to fail over to another one of the plurality of telephony switches.

Further in accordance with a preferred embodiment of the present invention the

method also includes determining whether a sufficient number of devices have failed

over, and responding to at least one keep-alive message based, at least in part, on a

result of the determining step.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be understood and appreciated more fully from the following detailed description, taken in conjunction with the drawings in which:

Fig. 1 is a simplified partly pictorial, partly block diagram illustration of a

telephony system having failure recover characteristics, the system being constructed

and operative in accordance with a preferred embodiment of the present invention;

Fig. 2 is a simplified flowchart illustration of a preferred method of operation of the

apparatus of Fig. 1 ;

Fig. 3 is a simplified flowchart illustration of a preferred load balancing method of

operation of the apparatus of Fig. 1; and

Fig. 4 is a simplified block diagram illustration of a preferred implementation of a

portion of the apparatus of Fig. 1.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Reference is now made to Fig. 1 which is a simplified partly pictorial, partly block diagram illustration of a telephony system having failure recovery characteristics, the

system being constructed and operative in accordance with a preferred embodiment of

the present invention. The system of Fig. 1 preferably comprises a plurality of

telephony switches 100, comprising at least a first switch 110 and a second switch

120.

It is appreciated that a larger number of telephony switches 100 may be provided,

only two telephony switches 100 being shown in Fig. 100 for sake of simplicity of

description. Furthermore, it is appreciated that an alternative preferred embodiment of

the present invention comprises a subcombination of the system of Fig. 1 comprising a

single telephony switch 100, typically without the additional components shown in the

system of Fig. 1.

The system of Fig. 1 also preferably comprises a data network 130, which may

comprise any appropriate data network as is well known in the art, such as, for

example, a LAN or a WAN.

The system of Fig. 1 also preferably comprises a plurality of telephony devices

140: a preferred implementation of the telephony devices 140 is described below with

reference to Fig. 4. Each of the telephony devices 140 is preferably operatively

associated with a plurality of end units 150 such as conventional telephones or other

communication devices. It is appreciated that a wide variety of appropriate telephony

devices 140 and end units 150. including telephony devices and end units which are

well known in the art. may be used. It is further appreciated that other types of

telephony device 140. including devices associated only with a single end unit or themselves comprising an end unit, may be used.

The system of Fig. 1 also preferably comprises a gateway 155, typically comprising

any appropriate gateway, as is well known in the art. operative to connect the

remainder of the system of Fig. 1 to the public switched telephone network (PSTN)

160 or to another outside telephone network. Preferably, the gateway 155 also has

failover capabilities similar to those described below with reference to the telephony

switch 100.

Each telephony switch 100 preferably comprises, in addition to conventional

components well known in the art of telephone switches, the following elements,

typically in operative association with each other and with the conventional

components:

1. a network adapter 170, the network adapter 170 being preferably operative to

mediate bi-directional communications between the telephony switch 100 and the

network 130;

2. a system information database 180, typically implemented in a combination of

computer hardware and software as is well known in the art and preferably comprising

an appropriate commercially available database management system, such as, for

example: Oracle v. 8, commercially available from Oracle Corporation World

Headquarters, 500 Oracle Parkway, Redwood Shores, CA 94065 USA.

3. a replication subsystem 190. typically implemented in software and preferably

being operative to replicate, as is well known in the field of database management

systems, at least a portion of the system information database 180 to a different

database not comprised in the same telephony switch 100 as the replication subsystem

190. The replication subsystem 190 may comprise suitable commercially available software, typically supplied together with a commercially available database management system, as mentioned above with reference to the system information database 180; typically the commercially available software is include in a

commercially available database management system, as described above.

It is appreciated that various components of the system of Fig. 1, including each

telephony switch 100 and each telephony device 140, may be implemented in a

suitable combination of hardware and software, as is well known in the art. It is

further appreciated that one or more of the plurality of telephony switches 100

comprised in the system of Fig. 1 may comprise conventional telephony switches (not

shown), which conventional switches may not comprise at least unit 190 of the

telephony switches 100 shown in Fig. 1.

The operation of the system of Fig. 1 is now briefly described. The first telephony

switch 1 10 and the second telephony switch 120 each operate, similarly to

conventional telephone switches, to provide telephony services in response to

telephony service requests received via the network 130 from one or more of the end

units 140. During provision of these services, each of the first telephony switch 110

and the second telephony switch 120 stores in the respective system information

database 180 comprised therein information regarding the end units 140.

Typically the stored information comprises identification and configuration

information sufficient to maintain connection with and provide services to the end

units 140: additional information may also be stored. When information,

predetermined to be a type of information important for maintaining service in the

even of component failure, is stored in the system information database 180, the

replication subsystem 190 replicates the stored information to another external database. For example, when information is stored in the system information database 180 of the first switch 1 10 concerning end units 200 serviced by the first switch 1 10, the information may preferably be replicated to the system information database 180

of the second switch 120.

The case of storing in a database comprised in the second switch 120 is by way of

example only, and is not meant to limit the generality of the foregoing.

Upon failure of the first switch 110, operations may thus be easily continued by the

second switch 120. Any appropriate method may be used to determine that the first

switch 1 10 has failed such as, for example, a keep alive method as is well known in the art.

Upon failure to update keep alive, either spontaneously by the first switch 110 or by

failure to respond to a message from another component of the system such as an end

unit 140 or the second switch 120, the other component of the system which detects

the failure to update keep-alive preferably initiates fail-over to the second switch 120.

Alternatively, a component which detects failure to update keep-alive may notify

another component which initiates fail-over to the second switch 120. It will be

appreciated that an appropriate choice of keep alive parameters may thus allow rapid

failover in the system of Fig. 1.

Reference is now made to Fig. 2, which is a simplified flowchart illustration of a

preferred method of operation of the system of Fig. 1. The method of Fig. 2 preferably

comprises the following steps:

A switch is operated normally, preferably in a manner similar to that of prior art

switches: during operation, system information is stored in an internal switch database

(step 210). During normal operation as described in step 210, stored data in the internal switch database is replicated to another database external to the switch, typically a database in another switch (step 220). Upon loss of keep-alive update or upon another appropriate indication of failure of the switch which has been replicating stored data, switch operations are failed over to another switch, using replicated data

in the other database to continue operations (step 230).

Referring back to Fig. 1 , it is appreciated that the apparatus of Fig. 1 may also

perform load balancing as is well known in the art. In the present invention, a

particular type of load balancing is possible in that an overloaded switch, such as a

switch which receives connection of a plurality of devices upon failure of another

switch, may cause load balancing to occur by failing to respond to keep-alive

messages for a period of time, such as a predetermined period of time or until load on

the overloaded switch drops to a predetermined load. Preferably, devices become

attached to other switches according to the load of the switch to which attachment is

made; this may also be true in the method of Fig. 2, in that failover may occur to the

least loaded switch.

Reference is now made to Fig. 3, which is a simplified flowchart illustration of a

preferred load balancing method of operation of the system of Fig. 1. The method of

Fig. 3 is self-explanatory in light of the above explanation.

Reference is now made to Fig. 4, which is a simplified block diagram illustration of

a preferred implementation of any of the telephony devices 140 of Fig. 1. The

components of the apparatus of Fig. 4 may be implemented in any suitable

combination of hardware and software, as is well known in the art.

The apparatus of Fig. 4 preferably comprises a digitized voice unit 240 and an

audio packetizer 250 operatively associated therewith. The digitized voice unit 240 is preferably operative to receive and send audio from and to an associated end unit such as any one or more of the end units 150 of Fig. 1 on one side; to digitize the audio if

necessary: and to forward the digitized audio to or receive digitized audio from the audio packetizer 250. The audio packetizer 250 is preferably operative to packetize

received digitized audio and to send the packetized digitized audio over a network

such as the data network 130 of Fig. 1. The audio packetizer 250 is also preferably

operative to receive packets from the network and to deliver digitized audio to the

digitized voice unit 240.

The apparatus of Fig. 4 also preferably comprises the following components:

- telephony signaling apparatus 260;

- a state machine 270;

- an interface and failover layer 280; and

- an H.323 stack 290.

Preferably, the telephony signaling apparatus 260 is operatively associated with the

state machine 270, which is operatively associated with the interface and failover layer

280. which is operatively associated with the H.323 stack 290, which is operatively

associated with a network such as the data network 130 of Fig. 1. The units 260, 270,

280. and 290 preferably each operate bi-directionally, similarly to the digitized voice

unit 240 and the audio packetizer 250 as previously explained. For the sake of

simplicity of description only and without limiting the generality of the present

invention, the units 260. 270. 280, and 290 will be described below as if they operated

uni-directionally.

Telephony signaling apparatus 260 is preferably operative to receive telephony

signals, as are well known in the art. from the end unit associated therewith and to report the received signals to the state machine 270. The state machine 270 is preferably operative to track calls and telephony states. The interface and failover

layer 280 is preferably operative to provide the state machine 270 with a convenient interface to the H.323 stack 290. and is responsible for connecting calls to a switch,

such as the first telephony switch 1 10 of Fig. 1. Preferably, failover functions of the

telephony device 140. as described above with reference to Figs. 1 - 3, are

implemented in the interface and failover layer 280, said implementation being

self-explanatory with reference to the above discussion of Fig. 1 - 3.

The H.323 stack 290 preferably comprises any appropriate standard H.323 stack, as

is well known in the art, the H.323 stack 290 being operatively associated with the

network.

It is appreciated that various features of the invention which are, for clarity,

described in the contexts of separate embodiments may also be provided in

combination in a single embodiment. Conversely, various features of the invention

which are. for brevity, described in the context of a single embodiment may also be

provided separately or in any suitable subcombination.

It will be appreciated by persons skilled in the art that the present invention is not

limited by what has been particularly shown and described hereinabove. Rather the

scope of the invention is defined only by the claims which follow:

Claims

What is claimed is:

CLAIMS 1. A telephony system comprising:

a data network:

a plurality of telephony devices each operatively associated with the data network

and operative to request telephony services, via the data network, in accordance with a

telephony protocol;

at least two telephony switches comprising a first telephony switch and a second

telephony switch, each of said at least two telephony switches being operatively

associated with the data network and operative to fulfill telephony service requests

received via the data network in accordance with the telephony protocol and each

comprising:

a system information database, the system information database being operative

to store configuration information defining a plurality of characteristics of each of said

telephony devices, wherein

said first telephony switch comprises a first data replication subsystem operative to

comprised in said second telephony switch.

2. Apparatus according to claim 1 and wherein said second telephony switch

comprises a second data replication subsystem operative to replicate the stored

configuration information to the system information database comprised in said first

telephony switch.

3. Apparatus according to claim 1 and wherein said at least two telephony switches also comprises a third telephony switch, and

said second telephony switch comprises a second data replication subsystem operative to replicate the stored configuration information to the system information

database comprised in said third telephony switch.

4. Apparatus according to claim 1 and wherein said telephony protocol comprises

H.323.

5. A telephony switch for use in a telephony system comprising a data network and a

plurality of telephony devices each operatively associated with the data network and

telephony protocol, said telephony switch comprising:

a network adapter operative to provide communications via a data network between

said telephony switch and a plurality of telephony devices and to receive telephony

service requests from said telephony devices;

a system information database, the system information database being operative to

store configuration information defining a plurality of characteristics of each of said

telephony devices; and

a first data replication subsystem operative to replicate the stored configuration

information to a second system information database external to said telephony

switch.

6. Apparatus according to claim 5 and wherein said second system information database external to said telephony switch is comprised in a second telephony switch.

7. Apparatus according to claim 5 and wherein said telephony protocol comprises H.323.

8. A method for providing recovery in a telephony system after the failure of a

telephony switch comprised in the system, the method comprising:

providing a first telephony switch having an internal switch database for storing

information and replication capability to replicate the stored information in another

database external to the telephony switch;

operating the first telephony switch, including storing system information in the

internal switch database;

replicating the stored system information to an external database external to the

first telephony switch;

detecting failure of the first telephony switch;

in response to a result of the detecting step, failing over operations of the first

telephony switch to a second telephony switch, using replicated system information in

the external database.

9. A method according to claim 8 and wherein said second telephony switch is

selected based, at least in part, on a load of said second telephony switch, from a

plurality of available telephony switches.

10. A method according to claim 8 and also comprising: performing load balancing between the second telephony switch and at least one other telephony switch.

1 1. A method according to claim 8 and wherein the step of detecting failure

comprises detecting failure using a keep-alive count.

12. A method according to claim 8 and wherein the external database is comprised

in the second telephony switch.

13. A method for use in a telephony system comprising a data network and a plurality of telephony devices each operatively associated with the data network and operative to request telephony services, via the data network, in accordance with a telephony protocol, said method comprising: providing communications via a data network between a telephony switch and a

plurality of telephony devices and receiving telephony service requests from said

telephony devices;

storing configuration information defining a plurality of characteristics of each of

said telephony devices; and

replicating the stored configuration information to a backup system information

database.

14. A method according to claim 13 and wherein said storing step comprises storing

in a system information database comprised in a first telephony switch.

15. A method according to claim 14 and wherein said backup system information database is comprised in a second telephony switch.

16 A method according to claim 13 and wherein said telephony protocol comprises

H 323

17 In a telephony system operative to provide failover of a telephony switch upon

failure of the telephony switch to update a keep-alive count, a load balancing method

comprising

providing a plurality of telephony switches;

identifying one of the plurality of telephony switches as an overloaded telephony

switch, and

failing to respond to at least one keep-alive message directed to the overloaded

telephony switch, thus causing at least one device associated with the overloaded

18 A method according to claim 17 and also comprising,

determining whether a sufficient number of devices have failed over; and

responding to at least one keep-alive message based, at least in part, on a result of

the determining step