Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04Q—SELECTING
  • H04Q3/00—Selecting arrangements
  • H04Q3/0016—Arrangements providing connection between exchanges
  • H04Q3/0025—Provisions for signalling

Definitions

• the present invention relates to signalling in a telecommunications system and more particularly to the transmission of signalling data over a packet switched network .
• H.323 the International Telecommunications Union
• H.323 Version 2 A fundamental and essential component of H.323 is the provision for the transmission of digitised and compressed voice data.
• H.323 also makes optional provision for the transmission of video and other data forms .
• H.323 makes mandatory the use of the ITU standard Q.931 for the negotiation of a call set-up between two H.323 terminals, to establish a channel therebetween over which the terminals may send user and signalling data.
• Q.931 is mandatory for certain call maintenance and termination functions.
• ISDN International Standard Digital Network
• DSS1 Digital Subscriber Signalling System No.l
• ISUP ISDN User Part
• PSTN Public Switched Telephone Network
• the inventors of the present invention have discovered that the existing Q.931 based signalling protocol employed by H.323 is not able to accommodate certain messages generated within an ISUP based ..network. More particularly, it has been discovered that the existing Q.931 based signalling protocol is unable to accommodate the Network Discard Indicator message which may be generated at a switch of a telecommunication network in the event that the switch does not support User-to-User signalling information contained in a received Q.931 message.
• This deficiency in the Q.931 based signalling protocol means that there is no way in which the switch, from which the User-to-User signalling information originated, can be informed for example that the receiving switch has discarded the signalling information. In certain circumstances this may lead to overcharging of the calling party.
• a method of communicating signalling data between a pair of telecommunication switches employing ISUP signalling, via a packet switched data network comprising using H.323 protocol to communicate over the data network where signalling data is carried by a Q.931 based protocol extended to provide for the transmission of the ISUP Network Discard Indicator message.
• the extended Q.931 protocol employed by the present invention is arranged to be applied within an H.323 protocol stack. More preferably, said connection or part of a connection formed ..between the subscriber parties is provided over a TCP/IP based network.
• This network may be a LAN, an internetwork, the Internet, or a combination of two or more of these.
• the H.323 protocol stack is provided over a TCP/IP protocol stack.
• apparatus for communicating signalling data between a pair of telecommunication network switches employing ISUP signalling, via a packet switched data network comprising means for using H.323 protocol to communicate over the data network where signalling data is carried by a Q.931 based protocol extended to provide for the transmission of Network Discard Indicator messages.
• Figure 1 illustrates schematically a telecommunications network in which user and signalling data is carried between exchanges of the network via an IP network
• Figure 2 is a flow diagram illustrating the transmission of Network Discard Indicator messages in the network of Figure 1.
• a first telephone exchange 1 is coupled to a subscriber terminal 2 via an ISDN access network (i.e. which uses the DSS1 signalling protocol)
• a second exchange 3 is coupled to a subscriber terminal 4 via a PSTN access network.
• Interexchange signalling within the network is carried using ISUP protocol messages requiring the provision at the PSTN exchange 3 of a PSTN/ISUP interface 5.
• the terminal 2 from which the call is established is referred to as the "calling party " whilst the other terminal 4 is referred to as the "called party' * .
• the terminals 2,4 may be connected to respective access exchanges 1,2 via intermediate routing nodes (e.g. multiplexers/demultiplexers) .
• the following description builds upon the disclosures of the ITU H.323 standard which makes mandatory the use of a Q.931 based standard for establishing and maintaining a call connection between two H.323 enabled terminals.
• the two exchanges 1,3 of the telecommunications network communicate via respective H.323 enabled terminals 6,7 which in turn communicate with each other over an IP based network 8.
• the H.323 protocol stacks lie on top of TCP/IP protocol layers such that the H.323 data may be conveyed between the exchanges over the IP network 8.
• a protocol stack consisting of ISUP over Q.931 over TCP/IP.
• the calling party 2 wishes to send certain User-to-User signalling information to the called party 4 during the call set-up procedure and which is facilitated by the ISDN access network available to the calling party 2.
• This information may include, for example, call forwarding information, call waiting information, or the like.
• the information is encapsulated at the access exchange 1,6 in an appropriate Q.931 message and is sent over the H.323 network 8 to the terminating exchange 3,5,7.
• the terminating exchange 3 is incapable of making use of the received User-to-User signalling information.
• the terminating exchange 3 must generate a Network Discard Indicator message, encapsulate it within a Q.931 message, and transmit the resulting Q.931 message back to the originating exchange over the IP network
• the Notification Indicator element is defined in the existing Q.931 standard as having three meaningful values or states . These are : Bits
• Figure 2 is a flow chart illustrating the steps involved in relaying a Network Discard Indicator message from the PSTN exchange 3 to the ISDN exchange 1.
• the exchanges (or switches) between which the Network Discard Indicator message is sent may be coupled via one or more intermediate switches, with the IP network extending only over an intermediate portion of the signalling connection, e.g. between two intermediate exchanges.
• the Network Discard Indicator message may be generated either at the terminating or originating exchange, or at one of the intermediate exchanges .
• the Network Discard Indicator message may be placed directly onto the IP network by the exchange at which the message is generated, or it may first be transmitted to an intermediate exchange over, for example, a Signalling System No.7 (SS7) signalling network.
• SS7 Signalling System No.7

Landscapes

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

Applications Claiming Priority (3)

Publications (1)

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• 1998
  • 1998-11-16 FI FI982472A patent/FI106595B/fi not_active IP Right Cessation
• 1999
  • 1999-11-15 WO PCT/EP1999/008783 patent/WO2000030370A1/en not_active Application Discontinuation
  • 1999-11-15 AU AU19660/00A patent/AU1966000A/en not_active Abandoned
  • 1999-11-15 CN CN 99813418 patent/CN1326643A/zh active Pending
  • 1999-11-15 EP EP99963302A patent/EP1131957A1/en not_active Withdrawn
  • 1999-11-15 JP JP2000583265A patent/JP2002530952A/ja not_active Withdrawn

Non-Patent Citations (1)

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