ATM transport system

United States Patent m

Christie

[54] ATM TRANSPORT SYSTEM

[76] Inventor: Joseph Michael Christie, 536 Green Ave., San Bruno, Calif. 94066

[21] Appl. No.: 562,206

[22] Filed: Nov. 22,1995

[51] Int CI.6 H04L 12/66

[52] U.S. CI 370/395; 370/410; 370/466;

370/524

[58] Field of Search 370/60, 60.1,79,

370/80, 94.2, 99, 110.1, 356, 395, 397, 399, 409, 410. 426. 466, 467, 524

[56] References Cited

U.S. PATENT DOCUMENTS

5,204,857 4/1993 Obara 370/60

5,271,010 12/1993 Miyakeetal 370/94.1

5,274,680 12/1993 Sortan et al..

5,345,445 9/1994 Hilleretal 370/60.1

5,363,433 11/1994 Isono .

5,473,677 12/1995 D'Amato et al. .

5.479.401 12/1995 Bitz et al. .

5.479.402 12/1995 Hataetal. .

5,483,527 1/1996 Doshi et al 370/60.1

5,506,844 4/1996 Rao .

NHEIIIieillllll

US005703876A [li] Patent Number: 5,703,876 [45] Date of Patent: Dec. 30, 1997

OTHER PUBLICATIONS

U.S. application No. 08/525,897, Christie, filed Sep. 8,1995. U.S. application No. 08/525,050, Christie, filed Sep. 8, 1995.

U.S. application No. 08/568,551, Christie, filed Dec. 7, 1995.

ANSI-TI. 113-1995, American National Standard for Telecommunications, "Signaling System No. 7 (SS7)—Integrated Services Digital Networkf (ISDN) User Part," New York, NY.

Primary Examiner—Douglas W. Olms
Assistant Examiner—Min Jung

Attorney, Agent, or Firm—Harley R. Ball; Michael J. Setter

[57] ABSTRACT

The invention is an ATM transport system that transports user information from a continuous signal transport system. The ATM transport system uses telecommunications signaling associated with the continuous signals to determine if the continuous signals are transporting any user information. If so, ATM cells containing user information are generated and transmitted, but if not ATM cells are not generated and transmitted. The invention includes an ATM interworking multiplexer and in some embodiments, a processor.

14 Claims, 2 Drawing Sheets

1

ATM TRANSPORT SYSTEM
BACKGROUND

At present Asynchronous Transfer Mode (ATM) technology is being used to provide high speed transport for traffic 5 carried by older transport formats such as DS1 and DSO. This ATM transport technique uses an ATM interworlring multiplexer (ATM mux) to convert telecommunications traffic from the older formats into ATM cells that can be transported over broadband connections. At the terminating 10 end of the broadband system, the ATM cells are re-converted back into the older format by another ATM mux for delivery to the older transport system.

Many older transport formats require the transmission of a continuous signal even when no user traffic is being 15 transported. For example, a DSO connection continuously transmits a 64,000 bit/second signal whether or not the DSO connection is transporting any user traffic. This causes a problem in the above-described transport scenario. The ATM mux will convert the DSO signal into ATM cells for 20 transport, and since the DSO signal is continuous, a continuous stream of ATM cells must be transported by the ATM network. This occurs even when no user traffic is being transported. The idle DSO signal is still transported in empty ATM cells. Methods to detect these idle continuous signals 25 that do not transport user information have included analyzing information samples from the continuous signals to detect idle codes. However, these idle codes may be emulated by user information such as voice or data. This causes

30

problems when trying to determine whether or not a signal carries user information.

The current situation represents a waste of resources. At present, there is a need for an ATM system that can transport continuous signal formats when they carry user traffic, but 35 not when they do not carry user traffic.

SUMMARY

The invention includes an asynchronous transfer mode (ATM) system for transporting user information in ATM ^ cells. The ATM cells contain a virtual path identification/ virtual channel identification (VPI/VCI). The user information is from a continuous-signal transport system that produces telecommunications signaling related to the continuous signal. The continuous signal is associated with 45 the VPI/VCI.

The system comprises a processor and ATM interworking multiplexer. The processor receives telecommunications signaling and detects, based on the telecommunications signaling, when the continuous signal is transporting user so information and when the continuous signal is not transporting user information. The processor associates the continuous signal with the VPI/VCL The processor also provides a control instruction to enable the VPI/VCI when the continuous signal is transporting user information, and pro- 55 vides a control instruction to disable the VPI/VCI when the continuous signal is not transporting user information.

The ATM interworking multiplexer is coupled to the processor. The ATM interworking multiplexer receives the continuous signal and associates it with the VPI/VCI. The 60 ATM interworking multiplexer receives the control instructions from the processor and generates and transmits ATM cells containing the VPI/VCI and the user information in response to the enabling control instruction. The ATM interworking multiplexer stops generating and transmitting 65 ATM cells containing the VPI/VCI in response to the disabling control instruction.

2

The invention has many variations. The telecommunications signaling protocol could be Signaling System #7. The processor might use an SS7 Initial Address Message (IAM) to detect when the continuous signal transports user information. The processor might use a Circuit Identification Code (C3C) in the SS7 IAM to identify the continuous signal and to associate the continuous signal with the VPI/VCI. The processor might use a an SS7 Release message (REL) or Release Complete message (RLC) to detect when the continuous signal no longer transports user information.

The invention might include a Signal Transfer Point (STP) that is linked to the processor and that transfers telecommunications signaling to the processor. The STP might transfer copies of Signaling System #7 (SS7) message routing labels to the processor. The STP might transfer copies of SS7 Initial Address Message (IAM), Release message (REL), or Release Complete message (RLC) routing labels to the processor. The STP might transfer copies of SS7 routing labels to the processor that have particular Originating Point Codes (OPCs) and Destination Point Codes (DPCs).

The ATM interworking multiplexer might receive a continuous DS3 signal or a continuous DS1 signal. The ATM interworking multiplexer might transmit the ATM cells over a SONET connection. In some embodiments, the ATM interworking multiplexer supports multiple signals. Individual VPI/VCIs would correspond to individual continuous signals. The ATM interworking multiplexer would include: a continuous signal interface to receive the continuous signals, an ATM Adaption Layer (AAL) to convert the continuous signals into ATM cells with corresponding VPV VCIs, an ATM interface to transmit the ATM cells, and a control interface to receive the control instructions and control the AAL to generate and transmit cells with enabled VPI/VCIs and to stop the generation and transmission of ATM cells with a disabled VPI/VCIs.

The invention provides the advantage of having the ATM system only transport cells that actually carry user information. Cells containing the continuous signal, but no user information are not transmitted. This provides for efficient allocation and use of bandwidth in the ATM system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a version of the present invention.

FIG. 2 is a block diagram of a version of the present invention.

DETAILED DESCRIPTION

For purposes of clarity, the term "connection" will be used to refer to the transmission media used to carry user traffic. The term "link" will be used to refer to the transmission media used to carry signaling. On the Figures, connections are shown by a single line and signaling links are shown by double lines.

FIG. 1 depicts a version of the present invention. Shown are switch 100, ATM interworking multiplexer (mux) 105, mapper 110, ATM system 115, and signal transfer point (STP) 120. These components are connected by connections 150-152 and linked by links 160-163 as shown. Those skilled in the art are aware that large networks have many more components than are shown, but the number of these components has been restricted for clarity. The invention is fully applicable to a large network.

Switch 100 is a conventional switch that transmits user traffic within continuous signals. Examples of continuous