Multiplex communications – Pathfinding or routing – Through a circuit switch
Reexamination Certificate
1998-04-20
2001-12-04
Olms, Douglas (Department: 2661)
Multiplex communications
Pathfinding or routing
Through a circuit switch
C370S217000, C370S225000, C370S401000, C370S410000, C370S467000, C379S229000
Reexamination Certificate
active
06327260
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to telecommunications networks which transmit signaling information to network elements, and more particularly, to telecommunications packet switched networks employing Signaling System 7 message transfer part protocol to transmit signaling information between a Signal Transfer Point and a telephonic switch of the network.
Telecommunications systems utilize networks of computer controlled devices, more commonly known as network elements, to facilitate signaling between the telecommunications service provider's central office and the end user. Signaling relates to the transmission of messages between network elements over a control data signaling network which is separate from the voice communication circuits. Examples of telecommunication message signaling include data to provide call set-up, common channel signaling and other control signaling between network switching elements over a signaling channel separate from the voice network. Certain communications standards or protocol are required for signaling in telecommunications networks.
Recently, the Signaling System No. 7 protocol has been mandated for out-of-band signaling communication involving telecommunication network elements and has been implemented worldwide. See Travis Russell, “Signaling System 7”, ISBN 0-07-054991-5, McGraw-Hill, Inc. 1995. Signaling System No. 7 (SS7) network elements are each uniquely identified by a Message Transfer Part (MTP) Signaling Point Code (PC). Network administrators set up routes through a SS7 network so that the network elements can send Message Signal Units (MSUs) from any network element to any other network element in the network.
Two types of network elements are telephonic switches and Signal Transfer Points (STPs). Telephonic switches control the telephone and service traffic that is provided by the telecommunications operating company. A key to a telecommunication service provider's success is for their public switched telephone network (PSTN) switches to provide continuous service. It is critical that the service provider's customers have the ability to communicate through the telecommunications network via the telephonic switch associated with the particular customer. Moreover, there are federal (United States) and world International Telecommunications Union Telecommunications (ITU-T) reporting requirements for SS7 failures (“outages”) above a certain threshold. The Signaling Transfer Points (STPs) act as signaling hubs for concentrating signaling links so the telephonic switches do not need to be fully interconnected, thereby reducing network costs while also acting as access points to network services and gateways to other networks.
Network elements, such as STPs and telephonic switches, are interconnected by link sets, or a group of signaling links that all terminate on the same set of Signaling Point Codes (elements associated with the point code, PC). Each signaling link is identified by three parameters, the two Point Codes (PCs) at each end of the link and a Signaling Link Selection (SLS) code. Referring now to
FIG. 1
, a conventional deployment of a single link set
20
interconnecting an STP
22
and the single signaling interface
24
associated with the telephonic switch
26
is shown. Each network element (STP
22
or switch
26
) is identified by its signaling point code assignment. Referring to
FIG. 2
, an SS7 network diagram illustrating link set deployment with a switch
26
and a pair of mate STPs
22
A,
22
B is shown. Each STP
22
A,
22
B has only one link set
20
A,
20
B, respectively, interconnecting the single signaling interface
24
at the telephonic switch. Because STPs
22
fully interconnect telephonic switches
26
, it is important to the telecommunications service provider, and invariably to its customers, that the STPs must not fail. Due to network redundancy in that STPs are generally provided in mated pairs,
FIG. 2
, one STP
22
A can take over for its failed mate
22
B.
Disadvantageously, however, the telephonic switch is dependent on its lone single signaling interface
24
for its total SS7 network communication capabilities. If a hardware or software failure exists, or a generic software update is required, it is almost certain that a signaling outage will occur at the telephonic switch. Once this happens the switch becomes isolated and telephonic communication is lost at all telephonic units associated with the switch during the isolation period. Signaling communication at a switch following SS7 protocol is dependent and thus, is limited by its lone signaling interface which unfortunately leads to potential switch isolation upon operational failures, upgrades to the system or upon field events. Therefore, there is a need in the art to prevent disruption of telecommunication signaling and to increase the signaling availability and reliability at the network telephonic switch.
SUMMARY OF THE INVENTION
The problems noted above are solved in accordance with the invention and a technical advance is achieved in the art, by providing a plurality of message signaling interfaces with the same point code at a single public telephonic network switch. Signaling information is transmitted from various network elements to one message signaling interface at the switch during normal operation and under certain preselected conditions the signaling information is sent from the network element to another message signaling interface at the same public telephonic network switch. The inventive apparatus and method significantly reduces the possibility of the network switch becoming isolated by maintaining continuous telecommunication signaling at the network switch thereby increasing its availability and reliability.
In particular, signaling information is communicated from a single signal transfer point within the telecommunication network across one link set to a message signaling interface at the telephonic network switch under normal operation. In response to certain preselected conditions occurring within the network, the signaling information transmitted from the single signal transfer point is re-routed across another link set to another message signaling interface employed as a secondary signaling interface at the same telephonic network switch.
In some cases, the signaling information is transmitted from the signal transfer point across the other link set to the other/secondary message signaling interface upon a failure or initialization at the primary message signaling interface. Additionally, upon a return to normal operation, the signaling information may selectively be transmitted back across the one link set to the primary message signaling interface.
REFERENCES:
patent: 4154983 (1979-05-01), Pedersen
patent: 4885738 (1989-12-01), Bowers et al.
patent: 5592466 (1997-01-01), Buczny et al.
patent: 5694463 (1997-12-01), Christie et al.
patent: 5864563 (1999-01-01), Ratcliffe
patent: 6061432 (2000-05-01), Wallace et al.
patent: 6104803 (2000-08-01), Weser et al.
patent: 6181710 (2001-01-01), Cooper et al.
AT&T Network Systems Common Channel Signaling 7 Information Guide, #256-002-100, Dated Apr. 1990.
Hom Shick
Lucent Technologies - Inc.
Olms Douglas
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