Method and system for providing an alternative common channel signaling path

A method and system for providing an alternate common channel signaling system path. The alternative signaling path that does not rely on the same hardware or software that is used for a primary signaling path. The alternative signal path allows network devices on a local area network to be signaled when a primary signaling path to the local area network has failed. The alternative signaling paths may provide better fault tolerance for connecting local area networks to other external networks.

FIELD OF INVENTION
 This invention relates to computer networks. More specifically, it relates
 to a method and system for providing an alternative common channel
 signaling pathway via dialed-up access.
 BACKGROUND OF THE INVENTION
 Common Channel Signaling System Number-7 ("CCS7" or "SS7") is a method of
 signaling that uses an out-of-band or separate channel signaling for
 conveying signaling information for a number of telecommunications
 channels. Common channel signaling is used in the Public Switched
 Telephone Network ("PSTN"), with Integrated Services Digital Network
 ("ISDN"), circuit switched networks and data networks. Common channel
 signaling is also being used for cellular and mobile telephony and network
 management.
 The common channel carrying signaling information is called a signaling
 link. Signaling information is exchanged between signaling points over a
 signaling link using signaling data packets. Common channel signaling
 system number-7 includes a structured protocol partitioned into four
 levels including from lowest to highest a physical, data link, network and
 user part level. The physical, data link and network levels transfer
 signaling messages between signaling points reliably and accurately. They
 also provide network management functions. The physical, data link and
 network levels are collectively referred to as the Message Transfer Part
 ("MTP").
 The user part level includes signaling applications to provide desired
 functionality. The user part level includes a Telephone User Part ("TUP"),
 ISDN User Part ("ISUP"), Transaction Capability Application Part ("TCAP")
 and others. The ISDN User Part includes both analog and digital telephony.
 A common channel signaling gateway host is often used on Local Area
 Networks("LAN") to interface with the public switched telephone network.
 One of the functions of the common channel signaling gateway host is to
 convert a common channel signaling user part message (e.g., ISDN user part
 messages) into a local protocol that is known by network devices on the
 local area network. The local protocol messages arc forwarded over a local
 area network connection to network devices to set up a telecommunications
 connection.
 For example, a common channel signaling host may convert a common channel
 signaling ISDN user part message into a local protocol message and send
 the local protocol message over a local area connection to a modem device
 to set up a telephone call or a data connection. The modem device will
 respond to the common channel signaling host in the local protocol. The
 common channel signaling host will then convert the local protocol
 response back to the common channel signaling protocol and send the
 response to the public switched telephone network to complete set up of
 the telephone call or data connection.
 Using a common channel signaling gateway on a local area network is subject
 to several problems. If the local area connection between the common
 channel signaling gateway and the network devices (e.g., modem devices)
 fails, communications with the public switched telephone network may be
 lost unless there is a backup signaling path.
 One solution is to provide a backup signaling path using an alternative
 connection to the local area network from the common channel signaling
 gateway. However, a hardware or software problem may exist that will also
 affect the alternative connection to the local area network. For example,
 if one or two ports on an Ethernet card are used to connect a local area
 network to a common channel signaling host, and the connection fails, an
 attempt may be made to use the second port on the Ethernet card as an
 alternative connection. However, the hardware or software on the Ethernet
 card may be defective and the alternative signaling connection may be
 lost. Another Ethernet card may also be used for the alternative
 connection. However, the Ethernet cards may have a common hardware or
 software problem so the alternative signaling connection may be lost
 again.
 Thus, it is desirable to provide an alternative connection between a local
 area network and a common channel signaling gateway host. The alternative
 connection should not use the same network device to connect the local
 area network and the common channel signaling gateway host as is used for
 the primary connection to prevent a common hardware or software problem
 from affecting both the primary and alternative connection.
 SUMMARY OF THE INVENTION
 In accordance with preferred embodiments of the present invention, some of
 the problems associated with providing an alternative signaling path are
 overcome. A method and system for providing an alternative signaling path
 is provided. One aspect of the present invention includes a method for
 providing an alternate signaling connection. The method includes receiving
 a first signaling message in a first protocol on a first signaling device
 on a first network from a second network to create a connection between a
 first network device on the first network and the second network. The
 first signaling message is converted into a second signaling message in a
 second protocol on the first signaling device. The first signaling device
 determines that a signaling first connection between the first signaling
 device and the first network has failed. The second signaling message is
 sent from a second network device associated with the first signaling
 device to a third network device on the second network over a second
 connection. The second signaling message is sent from the third network
 device on the second network to a fourth network device on the first
 network over a third connection. The second signaling message is sent from
 the fourth network device to the first network device on the first network
 over a fourth connection thereby providing an alternate signaling
 connection to the first network device on the first network from the first
 signaling device.
 For example, in one exemplary embodiment of the present invention, a common
 channel signaling gateway receives a common channel signaling message from
 the public switched telephone network for a first network device (e.g., a
 modem) on a local area network. The common channel signaling gateway
 converts the common channel signaling message into a second signaling
 message in a second protocol. The common channel signaling gateway
 determines that a signaling connection to the local area network has
 failed and uses a second network device (e.g., a modem) to contact a
 public switched telephone network. The public switched telephone network
 sends the second signaling message to a network access server associated
 with the local area network. The network access server receives the second
 signaling message and sends it to the first network device using an
 internal connection thereby providing an alternate signaling connection.
 However, the present invention is not limited to the network devices
 described in this exemplary embodiment and other embodiments with other
 network devices may also be used.
 Preferred embodiments of the present invention provide an alternative
 signaling path that does not rely on the same hardware or software that is
 used for a primary signaling path. The alternative signal path allows
 network devices on a local area network to be signaled when a primary
 signaling path to the local area network has failed. The alternative
 signaling path may provide better fault tolerance for connecting local
 area networks to other external networks.
 The foregoing and other features and advantages of a preferred embodiment
 of the present invention will be more readily apparent from the following
 detailed description, which proceeds with references to the accompanying
 drawings.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
 Exemplary Network System
 FIG. 1 is a block diagram illustrating an exemplary network system 10 with
 common channel signaling. Network system 10 includes a first signaling
 device 12 connected with a signaling first connection 14 to a first
 network 16 with a first network device 18. The first signaling device 12
 is connected to a second network 20 with a second signaling connection 22.
 The first signaling device 12 is also connected 24 to the second network
 20 via a second network device 26.
 The second network 20 is connected to a third network device 28. The third
 network device 28 is connected 30 to a fourth network device 32. The
 fourth network device 32 is also connected 34 to the first network 16.
 However, the present invention is not limited to the signaling devices,
 network devices, networks or connections illustrated in FIG. 1, and other
 signaling devices network devices, networks or connections may also be
 used.
 An operating environment for network devices and signaling devices of the
 present invention include a processing system with at least one high speed
 Central Processing Unit ("CPU") and a memory. In accordance with the
 practices of persons skilled in the art of computer programming, the
 present invention is described below with reference to acts and symbolic
 representations of operations that are performed by the processing system,
 unless indicated otherwise. Such acts and operations are referred to as
 being "computer-executed" or "CPU executed".
 It will be appreciated that acts and symbolically represented operations
 include the manipulation of electrical signals by the CPU. The electrical
 system represents data bits which cause a resulting transformation or
 reduction of the electrical signal representation, and the maintenance of
 data bits at memory locations in a memory system to thereby reconfigure or
 otherwise alter the CPU's operation, as well as other processing of
 signals. The memory locations where data bits are maintained are physical
 locations that have particular electrical, magnetic, optical, or organic
 properties corresponding to the data bits.
 The data bits may also be maintained on a computer readable medium
 including magnetic disks, optical disks, organic disks and any other
 volatile (e.g., Random Access Memory ("RAM")) or non-volatile (e.g.,
 Read-Only Memory ("ROM")) mass storage system readable by the CPU. The
 computer readable medium includes cooperating or interconnected computer
 readable medium, which exist exclusively on the processing system or be
 distributed among multiple interconnected processing systems that may be
 local or remote to the processing system.
 Alternative Signaling Path
 FIG. 2 is a flow diagram illustrating a Method 40 for providing an
 alternative signaling path. At Step 42, first signaling message in a first
 protocol is received on a first signaling device 12 on a first network 16
 to create a connection between a first network device 18 on the first
 network 16 and the second network 20. At Step 44, the first signaling
 message is converted into a second signaling message in a second protocol
 on the first signaling device 12. At Step 46, the first signaling device
 12 determines that a signaling first connection 14 between the first
 signaling device 12 and the first network 16 has failed.
 At step 48, the second signaling message is sent from a second network
 device 26 associated with first signaling device 12 to a third network
 device 28 on the second network 20 over a second connection 24. At Step
 50, the second signaling message is sent from the third network device 28
 on the second network 20 to a fourth network device 32 on the first
 network 16 over a third connection 30. At Step 52, the second signaling
 message is sent from the fourth network device 32 to the first network
 device 18 on the first network 16 over a fourth connection 34, thereby
 providing an alternate signaling connection 36 to the first network device
 18 on the first network 16 from the first signaling device 12.
 In one preferred embodiment of the present invention, the alternate
 signaling connection 36 is a virtual connection between the first
 signaling device 12 and the fourth network device 32 via the second
 network. The alternate signaling connection 36 includes wireless
 connections, satellite connections or other telephony connections.
 In one exemplary preferred embodiment of the present invention, Method 40
 is used to provide an alternative (a common channel Signaling System
 number-7"SS7") signaling path. For more information on common channel
 Signaling System number-7 see "Specifications of Signaling System No. 7",
 CCITT Blue Book, VI.7-VI.9, recommendations Q.701-Q.795, International
 Telecommunications Union, 1989, incorporated herein by reference. At Step
 42, a first SS7 signaling message is received on a SS7 gateway 12 on LAN
 16 from a Public Switched Telephone Network ("PSTN") to create a
 connection between a first network device 18 on the LAN 16 and a telephony
 switch 28 on the PSTN 20. The PSTN is any of those provided by AT&T,
 Regional Bell Operating Companies (e.g., Ameritech, U.S. West, Bell
 Atlantic, Southern Bell Communications, Bell South, NYNEX, and Pacific
 Telesis Group), GTE, and others.
 At Step 44, the SS7 signaling message is converted into a second signaling
 message in a second protocol on the SS7 gateway 12. In one exemplary
 preferred embodiment of the present invention, the second protocol is a
 Signaling LAN Application Protocol ("SLAP"). The SLAP protocol is used to
 transport SS7 and other protocols used on a Wide Area Network ("WAN") on a
 LAN. However, other protocols could also be used for the second protocol
 including Internet Protocol Device Control ("IPDC") by Level 3
 Communications of Omaha, Nebr., and others.
 At Step 46, the SS7 gateway 12 determines that a signaling connection
 (e.g., Transmission Control Protocol ("TCP") over Internet Protocol ("IP")
 connection) 14 between the SS7 gateway 12 and LAN 16 has failed. As is
 known in the art, TCP provides a connection-oriented, end-to-end reliable
 protocol designed to fit into a layered hierarchy of protocols which
 support multi-network applications. TCP provides for reliable
 inter-process communication between pairs of processes in network devices
 attached to distinct but interconnected networks. For more information on
 TCP see Internet Engineering Task Force ("IETF") Request For Comments
 ("RFC") RFC-793, incorporated herein by reference. As is known in the art,
 IP is an addressing protocol designed to route traffic within a network or
 between networks. IP is described in RFC-791, incorporated herein by
 reference.
 At step 48, the second signaling message is sent from a telephone network
 device 26 (e.g., a modem) associated with SS7 gateway 12 to telephony
 switch 28 on the PSTN 20 over a second connection 24. The telephony switch
 is any of those provided by Siemens AG, of Munich Germany, Lucent
 Technologies, of Murray Hill, N.J., Nortel, of Brampton, Ontario, Canada
 and others.
 At Step 50, the second signaling message is sent from the telephony switch
 28 on the PSTN 20 to a remote access server 32 on the LAN 16 over a third
 connection 30. In one preferred embodiment of the present invention, the
 remote access server 32 is a Total Control Telephony Hub by 3Com
 Corporation of Santa Clara, Calif. A Total Control Telephony Hub is
 described in U.S. Pat. No. 5,528,595, granted to Dale M.Walsh et al.,
 incorporated herein by reference. However, other remote access servers
 could also be used including those by Lucent Technologies (including those
 by the former Livingston Enterprises, Inc. of Pleasanton, Calif.), Ascend
 Communications of Alameda, Calif. and others.
 At Step 52, the second signaling message is sent from remote access server
 32 to the first network device 18 on the LAN 16 over a fourth connection
 34. An alternate signaling connection 36 is thereby provided to the first
 network device 18 on the LAN 18 from the 557 gateway 12.
 However, the present invention is not limited to the exemplary signaling
 devices, network devices, networks or connections described, and other
 signaling devices network devices, networks or connections may also be
 used.
 Preferred embodiments of the present invention provide an alternative
 signaling path that does not rely on the same hardware or software that is
 used for a primary signaling path. The alternative signal paths allow
 network devices on a local area network to be signaled when a primary
 signaling path to the local area network has failed. The alternative
 signaling paths may provide better fault tolerance for connecting local
 area networks to other external networks.
 It should be understood that the programs, processes, methods and system
 described herein are not related or limited to any particular type of
 computer or network system (hardware or software), unless indicated
 otherwise. Various types of general purpose or specialized computer
 systems may be used with or perform operations in accordance with the
 teachings described herein.
 In view of the wide variety of embodiments to which the principles of the
 present invention can be applied, it should be understood that the
 illustrated embodiments are exemplary only, and should not be taken as
 limiting the scope of the present invention. For example, the Steps of the
 flow diagrams may be taken in sequences other than those described, and
 more or fewer elements may be used in the block diagrams.
 The claims should not be read as limited to the described order or elements
 unless stated to that effect. Therefore, all embodiments that come within
 the scope and spirit of the following claims and equivalents thereto are
 claimed as the invention.