Method and apparatus for carrying telephony network traffic over an ATM network

A method that sends ATM source identification and an ATM-TDM correlation tag from an ATM source gateway to a telephony signaling control network; and then receives at an ATM destination gateway the ATM source identification and the ATM-TDM correlation tag as sent from the telephony signaling control network; and then sends the ATM-TDM correlation tag from the ATM destination gateway to the ATM source gateway to establish a connection between the ATM destination gateway and the ATM source gateway.

FIELD OF THE INVENTION

The field of invention relates to networking, generally; and more specifically, to carrying telephony traffic over an ATM network.

BACKGROUND

FIG. 1shows an example of a traditional approach for carrying telephony traffic. Telephony traffic is traditionally carried over a telephony network103. As is known in the art, a telephony network103employs: 1) circuit switching to set up a connection; and 2) time division multiplexing (TDM) to transport information over the connection. Some examples of a telephony network include a Public Switched Telephone Network (PSTN) or an Integrated Services Data Network (ISDN).

Telephony traffic is traffic traditionally carried by a telephony network such as voice traffic and facsimile (FAX) traffic. In the example ofFIG. 1, telephony traffic is carried by the telephony network103from a source device101(e.g., a telephone mouthpiece or transmitting FAX modulator) to a destination device102(e.g., a telephone earpiece or receiving FAX demodulator).

Note that, as an example, both the source device101and the destination device102are coupled to a corresponding local exchange or end office180,181(LE/EO). A local exchange typically handles traffic from a smaller geographic region while a central exchange typically handles traffic from a larger geographic region. Because either may apply to the exemplary depiction ofFIG. 1, the notation LE/EO180,181has been used.

The source device101is coupled to LE/EO180(which may also be referred to as the source LE/EO180) and the destination device102is coupled to LE/EO181(which may also be referred to as the destination LE/EO181). An LE/EO, such as source LE/EO180, provides for the efficient collection of information from different source devices. That is, traffic entering the telephony network103(e.g., from a plurality of different telephone mouthpieces and/or transmitting FAX modulators) may be combined at a LE/EO180and transported further upstream (i.e., deeper into the telephony network103) over a single trunk line113(e.g., a T1 line).

Similarly, a LE/EO such as destination LE/EO181also provides efficient distribution of information to different destination devices. That is, traffic leaving the telephony network103(e.g., toward a plurality of different telephone earpieces and/or receiving FAX demodulators) may be collectively received at a LE/EO from a single trunk line118(that is coupled to deeper regions of the telephony network103) and then distributed from the LE/EO to the appropriate destination devices.

For any connection carried by the telephony network103, the connection's establishment (e.g., call setup and teardown procedures) and routing path are controlled by a telephony signaling control network104. An example of a telephony signaling control network104is a Signaling System 7 (SS7) network. SS7 networks, which include local and national variants, are implemented world-wide.

As an example, when an individual at the source device101attempts to call an individual at the destination device102, the information indicative of the source and destination devices (e.g., an Initial Address Message (IAM) message) is typically forwarded from the source LE/EO180to a signaling transfer point (STP)105within the telephony signaling control network104. The STP105(which may also be referred to as the “source” STP105) helps arrange notification of the call to STP106(which may also be referred to as the “destination” STP106) responsible for the destination LE/OE181.

Upon such notification, the destination STP106will forward the IAM message to the destination LE/EO181. The destination LE/OE will then notify the destination device102of the call (e.g., via a “RING” signal). The destination LE/EO181is also informed, from the telephony signaling control network104, which TDM time slot on trunk line118that the information from the call is to be sent along. Generally, when multiple switches (i.e., more than two) are used to carry a call, a switch communicates the TDM time slot and trunk line (through the telephony signaling control network104) to the next switch used to carry the call.

A problem with telephony networks is their inherent emphasis on the transportation of telephony traffic. With the growth of the Internet, service demand for the transportation of data traffic (e.g., traffic between computing devices such as e-mails, HTML files, etc. exchanged between computers) has sharply risen. Unfortunately, the TDM approach employed by a telephony network is a networking architecture that is particularly tailored for the carrying of voice conversations. As a result, a telephony network does not efficiently handle the transportation of both voice and data traffic.

SUMMARY OF INVENTION

A method is described that sends ATM source identification and an ATM-TDM correlation tag from an ATM source gateway to a telephony signaling control network. At an ATM destination gateway, the ATM source identification and the ATM-TDM correlation tag are received after being sent from the telephony signaling control network. The ATM-TDM correlation tag is then sent from the ATM destination gateway to the ATM source gateway to establish a connection between the ATM destination gateway and the ATM source gateway.

DETAILED DESCRIPTION

A method is described that sends ATM source identification and an ATM-TDM correlation tag from an ATM source gateway to a telephony signaling control network. At an ATM destination gateway, the ATM source identification and the ATM-TDM correlation tag are received after being sent from the telephony signaling control network. The ATM-TDM correlation tag is then sent from the ATM destination gateway to the ATM source gateway to establish a connection between the ATM destination gateway and the ATM source gateway.

FIG. 2shows a solution to the problem described in the background. In the approach ofFIG. 2, an ATM network207is used as a “backbone” to carry (e.g., over long distances) telephony traffic between two telephony networks203a,203b. Because ATM employs cell switching technology, ATM efficiently transports both voice traffic and data traffic. As such, a service provider may be inclined to deploy ATM technology.

However, uses of a traditional telephony network may still be desirable. For example, to extend the original investment made in their own TDM equipment, customers of a service provider may decide to communicate to the service provider through a traditional telephony network203a,203b. In other cases, traditional telephony networks may be suitable because the transportation of data traffic to a particular region or customer is insignificant. Note that, in any of these cases, traditional telephony networks203a,203bmay correspond to networks operated by the service provider or a customer of the service provider or a combination of both.

In an embodiment, the ATM network207may approximately correspond to a wide area network (WAN) that carries traffic over longer distances while telephony networks203a, bmay approximately correspond to local networks that carry traffic over shorter distances (e.g., such as local exchange (LE) network or customer premise network). The network architecture200ofFIG. 2indicates that traffic between a first and second telephony network203a,203bis carried by an ATM network207.

That is, for example, if a call is made from a source device201to a destination device202(where the source device201is communicatively coupled to a first telephony network203aand the destination device202is communicatively coupled to a second telephony network203b), the call is routed from the first telephony network203athrough the ATM network207and then from the ATM network207to the second telephony network203b. In this manner, the transportation of the call is transparently carried as ATM traffic even though the source and destination devices201,202employ traditional telephony network transportation techniques.

In a basic case, telephony network203amay correspond to a source LE/EO (such as source LE/EO180ofFIG. 1) and telephony network203bmay correspond to a destination LE/EO (such as destination LE/EO181ofFIG. 1). In this case, trunk lines213,218may respectively correspond to trunk lines113,118(e.g., T1 lines) in the sense that they carry the call from the source and destination LE/EOs180,181to deeper regions of the network. It is important to note, however, that telephony networks203a,203bmay be comprised of any equipment used to implement a telephony network. As such, trunk lines113,118are not necessarily tied to an LE or OE.

The approach associated withFIG. 2integrates the connection establishment capabilities of both the ATM network207and the telephony signaling control network204so that an end-to-end connection from the source device201to the destination device202may be realized. In order to realize such a connection, as described in more detail below, information is exchanged between the ATM network207and the telephony signaling control network204.

Recall from the discussion in the background concerningFIG. 1that if a source device101attempts to call a destination device102, information indicative of the source and destination devices is typically forwarded to source STP105. Referring toFIG. 2, a similar procedure may be applied.

That is, communication interface214may correspond to communication interface114. As such, when the source device201initiates a call to the destination device202, information indicative of the source and destination devices (e.g., an IAM message, an ISDN setup message, an MGCP notification message) is forwarded over communication interface214from the first telephony network203ato a telephony signaling control network204.

Note that the communication interface214may be one of many different means used for communicating telephony signaling information between a telephony network203aand a telephony signaling control network204. Such means may include (but are not limited to including): SS7 Integrated Services digital network User Part (ISUP) signaling, the Media Gateway Control Protocol (MGCP), the ITU h.248 protocol, MEGACO, and an SCTP or RUDP based backhaul of ISDN signaling, etc.

After the telephony signaling control network204receives information that is indicative of the source201and destination202devices for the particular call, the telephony signaling control network204helps establish the call path through the telephony network203athat is coupled to the source device201by reserving appropriate resources and providing appropriate signaling. The telephony signaling control network204also decides that the call will be directed over a particular trunk line213that couples the telephony network203ato the ATM network207.

This decision may be based on trunk availability between telephony network203and ATM network207by routing algorithms that are executed in the telephony signaling control network. Each trunk line213,218may also be implemented as a “trunk group” or a “multiplexed line” and, as such, may also be referred to as a “trunk group/multiplexed line”.

When the telephony signaling control network204receives the source and destination information from the telephony network203a, notification of the call (i.e., call notice) is sent from the telephony signaling control network204to a source gateway208within the ATM network207. The call notification may include a description of the particular TDM time slot on trunk line213that will be used for the call. In cases where more than one trunk line213could apply, the call notice may also describe which particular trunk line will be used for the call.

An ATM source gateway208provides access to the ATM network207(via trunk line213) for the telephony network203athat is coupled to the source device201. The interface215between the telephony signaling control network204and the ATM source gateway208may take various forms such as a gateway control protocol, a signaling backhaul protocol or a combination of the two. Examples of a gateway control protocol include (but are not necessarily limited to) MGCP, MEGACO and the ITU h.248 protocol. Examples of a signaling backhaul protocol include (but are not necessarily limited to) Stream Control Transmission Protocol (SCTP) and Reliable User Datagram Protocol (RUDP).

After the ATM source gateway208receives the call notice, it responds to the telephony signaling control network (e.g., in the form of an acknowledgement) with: 1) an ATM source id (e.g., information that reflects the position of the ATM source gateway208within the ATM network207such as the ATM address of the ATM source gateway208); and 2) an ATM-TDM correlation tag (i.e., information that associates the ATM connection that will be used to transport the call with TDM parameters (e.g., trunk line and TDM time slot) that will be used to transport the call). Note that the ATM-TDM correlation tag may be a randomly generated number.

After the ATM source id and ATM-TDM correlation tag are received by the telephony signaling control network207(e.g., by call agent205), both are sent from the telephony signaling control network204to an ATM destination gateway209. The telephony signaling control network204also helps establish the remainder of the call path by reserving appropriate resources and providing appropriate signaling within telephony network203bthat is coupled to the destination device202. Thus, information that is indicative as to which particular TDM time slot on trunk line218that is being reserved for the call is also sent along with the ATM source id and the ATM-TDM correlation tag from the telephony signaling control network204to the ATM destination gateway209. An ATM destination gateway provides access to ATM network207for telephony network203b.

A call agent, such as call agent205and call agent206, are devices capable of communicating with multiple protocols that may be used to communicate with a telephony signaling control network204. For example, typically, a call agent not only communicates according to traditional SS7 based signaling but also other communication protocols that may be used to interface with a telephony signaling control network (e.g., MGCP, ITUh.248, MEGACO etc.). Thus, for example, if interface215corresponds to an MGCP interface and if interface214corresponds to an SS7 based interface, a call agent may be used to understand the signaling associated with both interfaces.

An ATM destination gateway209provides access to the ATM network207(via trunk line218) for the telephony network203bthat is coupled to the destination device202. In an embodiment, as seen inFIG. 2, the ATM source id and ATM-TDM correlation tag are forwarded from a source call agent205to a destination call agent206within the telephony signaling control network204. In a further embodiment, the ATM source id and ATM-TDM correlation tag are sent through the telephony signaling control network204within an IAM message.

The destination call agent206then forwards the ATM-TDM correlation tag and ATM source id to an ATM destination gateway209over communication interface216. The destination call agent206also helps establish, over communication interface217, the call in the telephony network203bthat is coupled to the destination device202. As such, the destination call agent206also informs the ATM destination gateway209as to which TDM time slot on trunk line218is being reserved for the call. If more than one trunk line exists the telephony signaling control network204may also inform the ATM destination gateway209as to the proper trunk line to be used for the call.

Again, communication interface216may take various forms such as a gateway control protocol, a signaling backhaul protocol or a combination of the two. Examples of a gateway control protocol include (but are not necessarily limited to) MGCP, MEGACO and the ITU h.248 protocol. Examples of a signaling backhaul protocol include (but are not necessarily limited to) Stream Control Transmission Protocol (SCTP) and Reliable User Datagram Protocol (RUDP).

Also, communications interface217may be one of many different means used for communicating telephony signaling information between a telephony network203band a telephony signaling control network204. Such means may include (but are not limited to including): SS7 Integrated Services digital network User Part (ISUP) signaling, the Media Gateway Control Protocol (MGCP), MEGACO, the ITU h.248 protocol, an SCTP or RUDP based backhaul of ISDN signaling, etc.

Upon receipt of the ATM-TDM correlation tag and ATM source id, the ATM destination gateway209initiates a switched virtual circuit (SVC) connection establishment sequence in which the ATM-TDM correlation tag is sent along with traditional switched virtual circuit (SVC) connection signaling from the ATM destination gateway209to the ATM source gateway208.

An SVC connection may be established by sending a SETUP message from a connection destination within an ATM network (e.g., ATM destination gateway209) to a connection source within an ATM network (e.g., ATM source gateway208). The SETUP message typically propagates through the ATM network207by hopping at each node that will be used to carry the connection.

For example, referring toFIG. 2, if the connection is to be carried over nodes212,211, and210, (which may be determined as a result of the execution of a routing algorithm) the SETUP message traverses each of these nodes. As a result of the SETUP message being sent, VPI/VCI information associated with the connection is updated into the mapping tables of each node used to support the connection.

In an embodiment, each SETUP message includes the aforementioned ATM-TDM correlation tag that was sent to the ATM destination gateway209by the telephony signaling control network204. SETUP messages without an ATM-TDM correlation tag are known in the art. A SETUP message is partitioned into various fields (which are referred to as Information Elements (IEs), similar to the manner in which a packet header is organized. In one embodiment, the ATM-TDM correlation tag is placed within the Called Party Sub-Address IE of a SETUP message (e.g., anywhere in the later19octets of this field). In another embodiment the ATM-TDM correlation tag is placed within the Generic Identifier Transport (GIT) IE. In another embodiment the ATM-TDM correlation tag is placed within the Generic Application Transport (GAT) IE. In another embodiment, the ATM-TDM correlation tag is placed within the User to User IE. In another embodiment, the ATM-TDM correlation tag is placed within the Network Call Correlation Identifier (NCCI) IE. In another embodiment, the ATM-TDM correlation tag is placed within the Calling Party Sub Address IE. In another embodiment, the ATM-TDM correlation tag is placed within the Served User Generated Reference IE (SUGR). Alternate embodiments may place the ATM-TDM correlation tag in other regions of the SETUP message not listed above where such placement is consistent with applicable industry standards.

Eventually, a SETUP message will reach the ATM source gateway208. The SETUP message received by the ATM source gateway208will include the ATM-TDM correlation tag. Thus, in a sense, after the ATM-TDM correlation tag was created by the ATM source gateway208it was “looped” through the telephony signaling network204and the ATM network207. Recall that the telephony signaling control network204(as part of the call notice previously provided through communication interface215) has already notified the ATM source gateway208as to which TDM time slot on trunk line213that the call will be carried over.

The ATM-TDM correlation tag is used by the ATM source gateway208to correlate the SETUP message with the particular TDM time slot on trunk line213that the call will be carried over. That is, recalling that the ATM source gateway208originally generated the ATM-TDM correlation tag in light of notification of the call, upon receipt of the ATM-TDM correlation tag within the SETUP message the ATM source gateway208can update its mapping tables (or similar information) so that the payload of cells sent from/to node212(having the appropriate VPI/VCI information for the connection) are transported to/from the trunk213and TDM time slot that was specified by the telephony signaling control network204.

Associated with this update, consistent with ATM SVC call establishment sequencing, ATM source gateway208sends a CONNECT message to the ATM destination gateway209through the nodes used to transport the call (e.g., nodes212,211,210as seen inFIG. 2). After the CONNECT message has been received by the ATM destination gateway209, an end to end connection between the source device201and the destination device202has been established.

FIG. 3shows a methodology that reviews, at a high level, the “looping” of the ATM-TDM correlation tag described above. Consistent with the description above, an ATM connection and ATM source id are sent301from an ATM source gateway to a telephony signaling control network. Then, the ATM-TDM correlation tag and ATM source id are sent302from the telephony signaling control network to an ATM destination gateway. Then, the ATM-TDM correlation tag is sent303within the ATM network, via a SETUP message, from the ATM destination gateway to the ATM source gateway.

It is important to point out that the techniques described above may be employed by any ATM network. Thus, these techniques may be employed not only by a purely cell switched ATM network but also by an ATM Adaptation Layer Type 2 (AAL2) packet network. In this case, an Establish Request (ERQ) message is used instead of a SETUP message and an Establish Confirm (ECF) message is used instead of a CONNECT message. Furthermore, rather than using VCI information, VCI/CID information is employed. ATM networks that comprise a combination of AAL2 packet and purely cell switched architectures may also use these techniques if appropriate translation of the SETUP/ERQ and CONNECT/ERF messages are provided as well as any needed bearer network conversions (e.g., from multiplexed to non-multiplexed cells).

It is also important to point out that the methodologies may be implemented at least partially with software. Thus it is to be understood that embodiments of this invention may be used as or to support software programs executed upon some form of processing core (such as a the CPU of a computer or an embedded microprocessor) or otherwise implemented or realized upon or within a machine readable medium. A machine readable medium includes any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computer). For example, a machine readable medium includes read only memory (ROM); random access memory (RAM); magnetic disk storage media; optical storage media; flash memory devices; electrical, optical, acoustical or other form of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.); etc.