EP1186143A1 - Procede de transition entre voies de transport base sur la qualite de service - Google Patents

Procede de transition entre voies de transport base sur la qualite de service

Info

Publication number
EP1186143A1
EP1186143A1 EP00936312A EP00936312A EP1186143A1 EP 1186143 A1 EP1186143 A1 EP 1186143A1 EP 00936312 A EP00936312 A EP 00936312A EP 00936312 A EP00936312 A EP 00936312A EP 1186143 A1 EP1186143 A1 EP 1186143A1
Authority
EP
European Patent Office
Prior art keywords
type
path
communication path
quality
switching
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Withdrawn
Application number
EP00936312A
Other languages
German (de)
English (en)
Inventor
Kevin R. Smith
Theodore E. Edwards
Richard L. West
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nortel Networks Ltd
Original Assignee
Nortel Networks Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Nortel Networks Ltd filed Critical Nortel Networks Ltd
Publication of EP1186143A1 publication Critical patent/EP1186143A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q3/00—Selecting arrangements
    • H04Q3/64—Distributing or queueing
    • H04Q3/66—Traffic distributors
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M7/00—Arrangements for interconnection between switching centres
    • H04M7/0024—Services and arrangements where telephone services are combined with data services
    • H04M7/0057—Services where the data services network provides a telephone service in addition or as an alternative, e.g. for backup purposes, to the telephone service provided by the telephone services network
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M2207/00—Type of exchange or network, i.e. telephonic medium, in which the telephonic communication takes place
    • H04M2207/20—Type of exchange or network, i.e. telephonic medium, in which the telephonic communication takes place hybrid systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M3/00—Automatic or semi-automatic exchanges
    • H04M3/42—Systems providing special services or facilities to subscribers
    • H04M3/42314—Systems providing special services or facilities to subscribers in private branch exchanges
    • H04M3/4234—Remote access to features of PBX or home telephone systems-teleworking in a PBX
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M7/00—Arrangements for interconnection between switching centres
    • H04M7/009—Arrangements for interconnection between switching centres in systems involving PBX or KTS networks
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M7/00—Arrangements for interconnection between switching centres
    • H04M7/12—Arrangements for interconnection between switching centres for working between exchanges having different types of switching equipment, e.g. power-driven and step by step or decimal and non-decimal
    • H04M7/1205—Arrangements for interconnection between switching centres for working between exchanges having different types of switching equipment, e.g. power-driven and step by step or decimal and non-decimal where the types of switching equipement comprises PSTN/ISDN equipment and switching equipment of networks other than PSTN/ISDN, e.g. Internet Protocol networks
    • H04M7/1275—Methods and means to improve the telephone service quality, e.g. reservation, prioritisation or admission control
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q2213/00—Indexing scheme relating to selecting arrangements in general and for multiplex systems
    • H04Q2213/13034—A/D conversion, code compression/expansion
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q2213/00—Indexing scheme relating to selecting arrangements in general and for multiplex systems
    • H04Q2213/1309—Apparatus individually associated with a subscriber line, line circuits
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q2213/00—Indexing scheme relating to selecting arrangements in general and for multiplex systems
    • H04Q2213/13093—Personal computer, PC
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q2213/00—Indexing scheme relating to selecting arrangements in general and for multiplex systems
    • H04Q2213/13103—Memory
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q2213/00—Indexing scheme relating to selecting arrangements in general and for multiplex systems
    • H04Q2213/13141—Hunting for free outlet, circuit or channel
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q2213/00—Indexing scheme relating to selecting arrangements in general and for multiplex systems
    • H04Q2213/13166—Fault prevention
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q2213/00—Indexing scheme relating to selecting arrangements in general and for multiplex systems
    • H04Q2213/13167—Redundant apparatus
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q2213/00—Indexing scheme relating to selecting arrangements in general and for multiplex systems
    • H04Q2213/13196—Connection circuit/link/trunk/junction, bridge, router, gateway
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q2213/00—Indexing scheme relating to selecting arrangements in general and for multiplex systems
    • H04Q2213/13204—Protocols
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q2213/00—Indexing scheme relating to selecting arrangements in general and for multiplex systems
    • H04Q2213/1322—PBX
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q2213/00—Indexing scheme relating to selecting arrangements in general and for multiplex systems
    • H04Q2213/1325—Priority service
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q2213/00—Indexing scheme relating to selecting arrangements in general and for multiplex systems
    • H04Q2213/13299—Bus
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q2213/00—Indexing scheme relating to selecting arrangements in general and for multiplex systems
    • H04Q2213/13389—LAN, internet

Definitions

  • the present invention relates to improving the quality of service of data transmissions, and more particularly, to ensuring a certain level of the quality of service of time sensitive data transmissions over networks .
  • PSTN public switched telephone network
  • a proposed alternative to communicating voice over a PSTN is communicating voice over a packet network, such as a local area network (LAN) or wide area network (WAN) .
  • a packet network such as a local area network (LAN) or wide area network (WAN) .
  • WAN wide area network
  • VOIP voice over internet protocol
  • Information is communicated over the Internet m the form of a formatted unit of data called a packet using Transmission Control Protocol/Internet Protocol (TCP/IP) .
  • TCP/IP Transmission Control Protocol/Internet Protocol
  • voice is packetized then communicated over the network.
  • An advantage of communicating voice over the Internet is the elimination of long distance toll charges when communicating between different local calling areas.
  • businesses can save significant toll expenses.
  • one drawback of the Internet is its unregulated access and indeterminate bandwidth.
  • the amount of network traffic can increase substantially at certain times of the day and at any given moment, which may thereby overload the network.
  • data packets being transported over the network may be delayed or even lost .
  • the extent to which data packets are delayed or lost can be quantified to provide a relative quality of service (QOS) measure that indicates the suitability of the network to deliver packets m a timely and/or acceptable manner. Delayed delivery of data packets is not typically acceptable during a live conversation because the delay causes broken or staggered speech delivery. Consequently, when the network QOS is poor, the communicating parties are often forced to terminate their Internet-based call and to initiate more traditional telephone network-based calls .
  • QOS quality of service
  • one type of voice communication system utilizes an IP network m combination with a PSTN.
  • the system determines whether the QOS of the IP network meets an acceptable QOS standard. If the QOS of the IP network is acceptable at call initiation, the call is routed via the IP network. Otherwise, the call is routed over the PSTN. While this system is helpful at the time of call initiation, this system does not remedy a reduction m the QOS for an Internet-based telephone call when the voice communication is m progress over the Internet. Consequently, m this type system, when the QOS for a voice communication unacceptably deteriorates during the communication, the communicating parties must terminate the IP-based telephone call and place another call via a PSTN.
  • systems or methods consistent with the present invention enable an existing communication occurring over a first type network to be communicated m high quality manner over another network when the quality of service of the first type network deteriorates.
  • Such systems and methods enable a time sensitive (e.g. real -time) communication, such as a telephone call or other streaming data, to be automatically switched between various communication paths based on the quality of service of one of the paths .
  • a system or method consistent with the present invention evaluates data " communication routing paths for use m routing time sensitive (e.g. real -time) communications over the paths. Such systems and methods evaluate whether the quality of data transmission over a first type communication path is acceptable and switches the time sensitive communication from the first type communication path to a second type communication path if the quality of transmission is not acceptable .
  • time sensitive e.g. real -time
  • the switching of the time sensitive communication may occur from an internet network to a circuit switched telephone network.
  • the time sensitive communication may include a voice communication, such as a telephone call, or other types of time sensitive communication. Additionally, a time sensitive communication may be switched from the second type communication path to the first type communication path if the quality of transmission over the first type communication path is acceptable .
  • the quality of service of the first type communication path is determined by transmitting data packets across the first type transmission path. Data packet delay and loss may be evaluated. Such systems and methods may determine the importance of a plurality of the communications and prioritize switching of the communications from the first type communication path to the second type communication path based on the importance of the communications . A certain amount of the second type communication path may be reserved for receiving switched higher importance communications. In another aspect consistent with the present invention, a system or method evaluates whether the quality of data transmission over a first type communication path is acceptable and switches a time sensitive communication from a second type communication path to the first type communication path if the quality of transmission over the first type communication path is acceptable.
  • the first type communication path may be an internet protocol network and the second type communication path may be a circuit-switched network.
  • the quality of data transmission over a first type communication path is evaluated and a time sensitive communication is switched back and forth between the first type communication path and a second type communication path based on the quality of service of the first type communication path.
  • the time sensitive communication may be switched back and forth between an internet network and a circuit switched telephone network.
  • the quality of telephone call transmissions along a first type telephone call transmission path is evaluated to determine if it meets preselected criteria. If the transmission quality meets the criteria, an existing telephone call is switched from a second type telephone call transmission path to the first type telephone call transmission path when the quality of service along the first type telephone type call transmission path meets the preselected criteria.
  • BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram of a system for switching data communications between data paths consistent with the present invention
  • Fig. 2 is a block diagram of a PBX system transceiver consistent with the present invention
  • Fig. 3 is a block diagram of a remote call unit consistent with the present invention
  • Fig. 4 is a block diagram of another embodiment consistent with the present invention for switching data communications between data paths; and Figs. 5a and 5b are flow diagrams consistent with the present invention.
  • a system or process consistent with the present invention transitions the communication of data between different types of transport paths based on the quality of service ("QOS") of one of the transport paths.
  • the data may include streaming data, such as voice, audio, video or other types of data where delivery time is important. This type data may be generally referred to as streaming media.
  • streaming media Such data communications are often transmitted from the source, received, and perceived, with respect to the transmission time from the source, m a relatively short time frame (e.g. m realtime) and may be generally referred to as time sensitive communications.
  • one path is designated as a preferred transport path -and another path is designated as an alternate transport path.
  • the QOS of the preferred transport path is determined by tracking data packets across the path
  • the QOS may be expressed m terms of packet delay or m terms of packet loss rate.
  • the data stream or streams being transmitted across the preferred transport path may be redirected to the alternate transport path.
  • the alternate transport path may be used for a fixed period of time, for the duration of one or more redirected data streams, or until an acceptable QOS is established on the preferred transport path. If one of these conditions is met, the redirected data streams on the alternate transport paths can be transmitted back to the preferred transport path.
  • the transport paths, between which the data streams are redirected or switched are different types of transport paths, such as paths having different communication protocols.
  • the preferred transport path may be an Internet protocol (IP) network and the alternate transport path may be a circuit- switched network, such as a public switched telephone network (PSTN) .
  • IP Internet protocol
  • PSTN public switched telephone network
  • a system consistent with the present invention measures certain indicators of network traffic and dynamically adapts the system to ensure that a certain level of QOS is provided for a voice communication.
  • the alternate path transport system includes a packet network, such as a wide area network (WAN) 14, and a PSTN 18 for alternately transporting data between two locations based on measured QOS parameters of the preferred transport path, which m this example is the WAN 14.
  • the WAN 14 is discussed herein as an Internet network, but may be an ATM network or other suitable packet network.
  • the Internet is a massive set of network facilities, connected by routers, that enable various devices to communicate without regard to where they are located on the network.
  • TCP/IP transmission control protocol/Internet protocol
  • IP specifies rules for routing data
  • TCP specifies rules for ensuring m sequence delivery of data.
  • the WAN 14 is coupled between the two locations 20 and 22 via routers 26 and 28.
  • IP specifies rules for routing data
  • TCP specifies rules for ensuring m sequence delivery of data.
  • the WAN 14 is coupled between the two locations 20 and 22 via routers 26 and 28.
  • the call may be automatically switched to the PSTN 18 so that the call may be continued without interruption and with a higher QOS If the QOS of the WAN 14 later meets a specified threshold value, telephone calls that were initiated on the PSTN 18 or that were switched to the PSTN 18 may be re-routed-Dver the WAN 14.
  • a system consistent with the present invention is particularly useful m a distributed private branch exchange (PBX) environment where a PBX system 30 and associated telephones 32 are used at location 20 and where remote access to the PBX system 30 is provided at location 22 for remote telephones 34 via a remote call unit 36.
  • PBX system suitable for use with the present invention for handling integrated voice, data, and video is a Meridian 1 system available from Nortel Networks Corporation of Montreal Canada.
  • the Meridian 1 enables PBX functions to be extended to remote locations by providing distributed PBX communications between the main PBX system and the remote call unit 36.
  • the remote call unit 36 enables full featured PBX services to be provided to a selected number of users of telephones 34.
  • the QOS of the WAN 14 is constantly monitored at each end.
  • the system When the QOS of the WAN 14 falls below a preselected threshold for a preselected duration, the system will establish a call between the host PBX system 30 and the remote call unit 36 over PSTN 18.
  • the call to establish the PSTN connection may be initiated from either the remote location 22 by the remote call unit 36 or the host site by the PBX system 30, depending on a user selected option.
  • Multiple PSTN connections may be established between the host and remote site depending on the bandwidth required to service all currently active calls on the WAN 14.
  • calls or voice packet streams are rerouted from the WAN 14 to the PSTN 18.
  • the system moves as many calls as possible from the WAN 14 to the PSTN 18. If there are not enough lines or bandwidth to move all of the active calls from the WAN 14 to the PSTN 18, users identified as high priority users will have their calls moved to the PSTN 18 before lower priority calls are moved. Lower priority users' calls continue across the WAN 14 until the users terminate their calls or until additional telephone lines become available on the PSTN 18. It should be appreciated by those skilled m the art that other priority schemes such as a random scheme or first-m, first-out scheme that switches calls based on the order m which the calls where placed. New calls are routed over the PSTN 18 if circuits switched bandwidth of the PSTN 18 is available. Otherwise, new calls are blocked.
  • the transition between one transport path and another transport path is essentially transparent to the user, although the transition occurs during an active call or communication.
  • the transition appears transparent to the users for several reasons: the WAN 14 and PSTN 18 transport packetized voice data; the packetized voice data is automatically reformatted for and transitioned to the particular network designated for transport based on the QOS measure; and the system 10 ensures that an acceptable communication path, between - li ⁇
  • the locations 20 and 22 is established on the transport path over which the communication will be switched before switching the communication.
  • the users may notice an improvement m the voice quality when the transition takes place.
  • the users may notice a several second delay while the PSTN call or connection is being established .
  • the QOS test is continuously performed to determine when an acceptable QOS has been restored to the WAN 14.
  • An administrator may configure a QOS threshold and a duration that the threshold is to satisfy before voice traffic will be returned to the WAN 14.
  • the system prevents calls from being switched back and forth between the two transport paths during short or ephemeral improvements m the QOS of the WAN 14. After an acceptable QOS measurement is established for the specified duration, active calls are moved back to the WAN 14 and all new calls and signaling are placed over the WAN 14.
  • the ability to automatically transition calls between different types of transport paths is enabled m the system 10 by providing control or transceiver units, the PBX system 30 and the remote call unit 36, at the terminal ends of the transport paths at the locations 20 and 22.
  • the transceiver units can control or ensure the set up of a communication path to a particular destination telephone over one path while the communication to that telephone is occurring over another path.
  • the PBX system 30 and the remote call unit 36 have access to and may initiate a communication over either transport path and coordinate operations to determine which transport path should be used and wiien a suitable communication path has been established for the communication of data packets along the selected path.
  • the PBX system 30 initiates a call to the remote call unit 36, the remote call unit 36 answers the call and the PBX system 30 and remote call unit 36 communicate to determine if an acceptable PSTN connection can be made to support the calls that need to be transferred.
  • the PBX system 30 and remote call unit 36 continue to communicate to determine the QOS of the WAN 14.
  • the PBX system 30 sends data packets over the WAN 14 to the remote call unit 36 to which the remote call unit 36 responds back to the PBX system 30 to determine the QOS of the WAN 14.
  • the QOS of the WAN 14 is determined by measuring average packet delay or packet loss rate. Average packet delay is calculated using statistics gathered from the system's jitter buffer, as known to those skilled m the art.
  • a jitter buffer collects data packets received over the WAN 14 and is used to facilitate smooth play out of voice packet data.
  • the statistics derived from the packets m the jitter buffer are: minimum packet holding time m the jitter buffer; maximum packet holding time m the jitter buffer; and peak holding time m the jitter buffer. By accumulating these statistics over time, the system can calculate an average packet delay value through the IP network. As the system detects an increasing trend m the average packet delay, a user-defined threshold is referenced to determine the appropriate time to fall back or transition to the PSTN connection .
  • Packet loss is determined by measuring the number of packets that are dropped from the network over a specified time. Lost packet measurements are maintained by accumulating packet header information and voice decoder statistics. These statistics are: voice decoder under run; voice decoder over run; out of sequence packet reception; and time stamp values m the packet header. By accumulating these statistics over time, an accurate lost packet count can be determined. When the lost packet count reaches a user selected threshold, the calls may be transitioned to the PSTN 18 as discussed herein.
  • the IP network is continuously monitored to determine the appropriate time to restore voice traffic.
  • Pseudo voice packets or test data packets are placed on the IP network by both the PBX system 30 and the remote call unit 36.
  • This traffic is not sent as a continuous stream but rather sent m short bursts at a high bit rate, to approximate live voice traffic. Both ends gather the statistics based on this test traffic to determine a current congestion or QOS level on the network.
  • packet time stamps and sequence numbers the following parameters are monitored during offline testing (i.e.
  • the system may be set to move voice traffic to PSTN connections during specified periods of the day. This allows the user to avoid QOS degradation during known peak traffic times on the WAN 14. Additionally, user-defined options may be included that configures the system to always use the WAN network 14 or always use the PSTN connections based on the selected option.
  • the PBX system 30 includes a central processing unit (CPU) 202, a call processor 206, a voice digitizer 210, a line card 214, Internet gateway (ITG) 216, a voice over IP (VOIP) format unit 218, a PSTN format unit 222, a QOS analysis unit 226, a transport path control unit 230, a jitter buffer 234, a PBX system bus 238, and an input/output (I/O) interface 242.
  • CPU central processing unit
  • call processor 206 the voice digitizer 210
  • line card 214 includes Internet gateway (ITG) 216, a voice over IP (VOIP) format unit 218, a PSTN format unit 222, a QOS analysis unit 226, a transport path control unit 230, a jitter buffer 234, a PBX system bus 238, and an input/output (I/O) interface 242.
  • I/O input/output
  • Data is communicated between components of the PBX system via the PBX system bus 238.
  • the CPU 202 m conjunction with computer programs and other circuits control the operations of the PBX system 30. It should be appreciated that many of the components illustrated may be implemented m software stored m memd y modules, hardware, or a combination thereof.
  • the call processor 206 is a generalization of the components, known m the art, of a PBX system that receive and distribute incoming and outgoing calls.
  • the call processor 206 receives and distributes data packets, such as voice data packets, from and to the WAN 14 and
  • the Internet gateway 216 processes data that is received from or output to the internet to enable the appropriate communication, as known to those skilled m the art.
  • Voice associated with outgoing calls from the telephones 32 are digitized by the voice digitizer 210 and are directed to either the VOIP format unit 218 or the PSTN format unit 222 depending on the transport path mode selected by the transport path control unit 230.
  • the VOIP format unit 218 formats a digitized voice packet for transmission over the WAN 14 and the PSTN format unit 222 formats digitized voice packets for transmission over the PSTN 18.
  • the transport path control unit 230 selects the transport path mode that determines the transport path over which the data packets are to be routed.
  • the transport path control unit 230 causes a PSTN telephone call to be initiated to the remote call unit 36 for switching calls to the PSTN 18 and causes termination of PSTN connections when the calls are switched from the PSTN to the WAN 14.
  • the transport path mode is selected based on the QOS of the WAN 14 as determined by the QOS analysis unit 226.
  • the QOS analysis unit 226 determines the QOS of the WAN 14, as discussed above, by analyzing data collected in the jitter buffer 234.
  • IP mode is selected by the transport path control unit 230 and calls are routed over the WAN 14. Otherwise, PSTN mode is selected by the transport path control unit 230 and calls are routed over the PSTN 18.
  • the PBX system 30 illustrated includes an Internet gateway line card 214 which provides ports for supporting remote users.
  • the line card 214 emulates a standard digital line card, such as the digital line card (XDLC) sold by Nortel Networks and provides PBX functionality to remote users.
  • XDLC digital line card
  • Each port on the line card 214 is configured in accordance with the PBX ' s databases so that the line card appears to be a locally connected standard digital line card to the PBX system.
  • the line card 214 relays voice and signaling for each port to the associated telephone at the remote site, using digital trunks, an integrated 10 base T interface (voice over IP) or integrated v.35 interface (voice over frame relay) .
  • Voice data is compressed and packetized for transport regardless of the connection type being Used.
  • Voice over IP connections are supported by a 10 base T Ethernet interface for connection to the TCP/IP data network through the router or hub.
  • Voice data is packetized and formatted as UDP/IP packets and PBX signaling data is transmitted as TCP/IP packets.
  • the data is HDLC framed
  • IGW internet gateway
  • the remote call unit 36 supports multiple digital telephone lines and may support an analog connection for fax or modem traffic.
  • the remote call unit 36 relays voice and signaling information from the digital phones connected at the remote site to the host PBX system 30.
  • Each port on the remote call unit 36 is passed to the host site across a basic rate ISDN trunk of the PSTN 18 or through an integrated 10 base T Ethernet voice over IP connection of the WAN 14.
  • the remote call unit 36 has components that perform many of the functions as like or similar components of the PBX system 30.
  • the remote call unit includes a central processing unit (CPU) 302, a call processor 306, a voice digitizer 310, a line card 314, an Internet gateway 316, a voice ove ⁇ I? format unit 318, a PSTN format unit 322, a QOS analysis unit 326, a transport path control unit 330, a jitter buffer 334, a call unit system bus 338, and an input/output (I/O) interface 342.
  • CPU central processing unit
  • call processor 306 a voice digitizer 310
  • line card 314 an Internet gateway 316
  • voice ove ⁇ I? format unit 318 a PSTN format unit 322
  • QOS analysis unit 326 a transport path control unit 330
  • jitter buffer 334 a jitter buffer 334
  • call unit system bus 338 an input/output (I/O) interface 342.
  • I/O input/out
  • the transport path control unit 330 is operable to perform the same functions as the transport path control unit 230 (Fig. 2) .
  • the transport path control unit 330 directs the packetized voice from telephones 34 to the VOIP format unit 318 or PSTN format unit 322 depending on the mode determined by the PBX system, which is relayed to the remote call unit 36.
  • the remote call unit 36 receives a signal from the PBX system 30 to enable the appropriate switching of data paths and signals at the remote call unit 30.
  • PSTN or IP packets are received at the remote call unit 36, the packets are directed to appropriate format unit for translation.
  • Alternate path transport system 400 includes two PBX systems 410 and 420 at locations 412 and 422, respectively, that are enabled to automatically switch an existing call or streaming data communication between a WAN 430 or PSTN 440 depending on the QOS of the WAN 430.
  • the system 400 illustrates PBX systems that are retrofitted to be consistent with the present invention.
  • the PBX systems 410 and 420 are trunk side ITG systems which are not able themselves to call out to another system to coordinate the transfer of calls between WAN 430 and ⁇ PSTN 440 during a live or existing communication.
  • the PBX systems 410 and 420 at each location 412 and 422 have been coupled to remote call units 450 and 460, as described m connection with Fig. 3, to enable the PBX systems 410 and 420 to operate consistent with the present invention.
  • the remote call units 450 and 460 are coupled between the PBX systems 410 and 420 and the WAN 430 and operate as line side internet gateway systems.
  • the remote call units 450 and 460 enable control over both the terminal ends of WAN 430 and PSTN 440 connections between the two locations 412 and 422.
  • Routers such as routers 470 and 480, route data traffic of the PBX systems 410 and 420 and computer systems 454 and 464 over the WAN 430.
  • a typical PBX system configured for communication of voice over IP sets up calls to be routed either as VOIP calls or PSTN calls at the time of call initiation.
  • the remote call units 450 and 460 are positioned between the routers 470 and 480 and the PBX systems 410 and 420 to coordinate the switching of telephone calls between the two transport paths during a communication.
  • the line side and the internet gateway associated with the voice communication can automatically control switching between two types of transport paths during an existing communication.
  • the PBX systems 410 and 420 are coupled to the remote call units 450 and 460 via dedicated LAN connections 452 and 462 and also are coupled to the remote call units 450 and 460 via telephone line connections 458 and 568.
  • Either remote call unit 450 or 460 may monitor the quality of service of the WAN similar to the manner discussed above in connection with the PBX systerr 30.
  • the remote call unit 450 may be designated as the primary or switching remote call unit and when the QOS of the WAN falls below a preselected threshold, the remote call unit 450 places a call to the other remote call unit 460 over the PSTN 440 via the PBX system 410 through telephone line 458.
  • the remote call units 450 and 460 handshake, via the telephone lines 458 and 468 over the PSTN 440, to set up transfer of calls from the WAN 430 to the PSTN 440.
  • the remote calls units When calls are transferred from the WAN 430 to the PSTN 440, the remote calls units continue to monitor the QOS of the WAN 430 by communicating pseudo voice traffic to determine packet delay and loss as discussed above. When the QOS of the WAN 430 returns to an acceptable quality, the remote call unit 450 transitions the calls from the PSTN 440 back to the WAN 430. C . Processes
  • a flow diagram of the processes consistent with the present invention is illustrated.
  • the mode of operation of the alternate transport system is determined (step 514) and the priority of" the dialing number and dialed number is determined (step 516) .
  • the system may be initialized to a user selected mode.
  • telephone calls on certain telephone lines may be designated as high priority calls.
  • Certain high priority calls are routed through the PSTN always, regardless of the mode of operation of the system (step 518) . If the system is operating m PSTN mode and all PSTN lines are being used, new calls are blocked. It should be noted that a certain amount of PSTN lines or bandwidth may be reserved for high priority calls.
  • the mode of operation (IP or PSTN) of the alternate transport path system is evaluated (step 524) . If the mode is IP mode (step 524) , the call is routed through the WAN (step 528) . If, however, the mode is PSTN mode (step 524) , the call is routed through the PSTN network (step 530) . By routing the call through the PSTN network when the QOS on the preferred network is below the predefined threshold, a higher QOS of the call can be ensured. After a call or calls have been initiated on either network, the system constantly monitors tfte QOS of the WAN based on the mode of operation (step 536) .
  • IP or PSTN mode functions performed and thresholds monitored may vary.
  • the QOS measure is compared to an PSTN mode threshold.
  • the PSTN mode threshold is used to determine when calls that are currently being transported on the PSTN network are to be switched back to the IP network.
  • the IP mode threshold may include two measurements: t e actual QOS as measured by analyzing data packets and tne length of time that the QOS has been maintained above a specified threshold. The length of time measure is usea to avoid switching PSTN calls back to the IP network based on a QOS measure that was a momentary improvemen .
  • the QOS measure is compared with the PSTN mode threshold (step 554) and if the QOS measure is not greater than the PSTN mode threshold, calls are allowe ⁇ to continue on the PSTN network (to step 510) . If, however, the QOS measure is greater than the PSTN mode threshold, the PSTN calls which are not required to be communicated over the PSTN network at all times are switched to the preferred or IP network (step 558) .
  • the QOS measure is compared to a back-up service or IP mode threshold (step 570) .
  • the back-up service threshold is the value that quantifies the minimum level of QOS that is acceptable on the IP network. If the QOS measure is greater than or equal to the back-up service threshold, the calls that are currently being transported across the IP network are allowed to continue across the network (to step 510) . If the QOS measure is less than the back-up service threshold (step 572), the existing telephone calls are identified for potential switching to the PSTN network. For the current calls being transported over the IP network 14, the priority value, if any, is determined for the calls (step 580) .
  • the system also determines the number of PSTN lines available for the calls (step 582) .
  • the number of calls switched from the IP network to the PSTN lines typically equals the number of available PSTN lines. Calls are switched to the PSTN network m the order of priority to ensure that high priority calls are transferred to the PSTN network (step 586) .
  • transport paths Although only two types of transport paths have been discussed m detail, it should be appreciated that other types of transport paths may be used m connection with the present invention. Additionally, it should be appreciated that a system operating consistent with the present invention may switch an existing communication among two or more transport paths based on QOS criteria selected for the transport paths.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • General Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Data Exchanges In Wide-Area Networks (AREA)
  • Telephonic Communication Services (AREA)

Abstract

Selon cette invention, une communication existante effectué à travers un réseau de premier type peut être communiquée avec une qualité de service élevée à travers un autre réseau lorsque la qualité de service du premier réseau se détériore. Une communication en temps réel telle qu'un appel téléphonique ou d'autres données de transmission en continu peut être automatiquement commutée entre diverses voies de communication sur la base de la qualité de service de l'une des voies, de voies commutées par circuit ou d'autres voies de communication qui prennent en charge la communication de données en temps réel.
EP00936312A 1999-05-26 2000-05-26 Procede de transition entre voies de transport base sur la qualite de service Withdrawn EP1186143A1 (fr)

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US13621399P 1999-05-26 1999-05-26
US136213P 1999-05-26
PCT/US2000/014467 WO2000072536A1 (fr) 1999-05-26 2000-05-26 Procede de transition entre voies de transport base sur la qualite de service

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AU5164200A (en) 2000-12-12

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