Telephonic communications – Plural exchange network or interconnection – Interexchange signalling
Reexamination Certificate
2002-03-08
2004-09-14
Hong, Harry S. (Department: 2642)
Telephonic communications
Plural exchange network or interconnection
Interexchange signalling
C370S353000, C370S524000, C379S221100, C379S221140
Reexamination Certificate
active
06792100
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to telecommunications and, more particularly, to circuit-based switching convergence with packet-based-switching involving retention and sharing of an existing Signaling Point Code.
2. Background Description
Communications infrastructure throughout the world has undergone constant evolution. Much of the world's infrastructure in the public switching domain is comprised of several different technologies. Public switched telephone networks (PSTN) are heavily entrenched with circuit-based-switches and one technology of preference to support PSTN operations is common channel signaling system No. 7 known also as SS7. SS7 is a global standard for telecommunications defined by the International Telecommunications Union (ITU) Telecommunications Standardization Sector (ITU-T).
The standard defines the protocols and procedures used by network elements in the PSTN to exchange information over a digital signaling network to enable establishment, routing, and control of calls. The ITU definition of SS7 allows for national variants such as European Telecommunications Standards Institute (ETSI) standards that are used in Europe and, for North America, the Bell Communications Research and American National Standards Institute (ANSI) versions are used. SS7 calls are of various natures including wireless (cellular), wireline, data, and a plethora of telephone and data customer features such as credit card validation, voicemail access, paging, banking access, voice conferencing, data connectivity, Internet access, etc.
SS7 networks and protocols are typically used for basic call setup, management, and release, local number portability, toll free and toll wireline services. It also supports enhanced call features such as call forwarding, calling party name
umber display, three way calling, wireless services such as personal communications services (PCS), cellular roaming, and mobile subscriber identification.
SS7 messages are exchanged between network elements over 56 or 64 kilobit per second bi-directional channels called signaling links. The three kinds of network elements in a SS7 network include a Service Switching Point (SSP), a Signal Transfer Point (STP), and a Service Control Point (SCP).
SSPs are switches that originate, terminate and release circuits to manage calls. SSPs can query an associated SCP to determine routing information on a given call. SCPs contain centralized databases.
Network traffic between signaling points can be routed by an STP packet switch. An STP routes incoming messages to an outgoing signaling link based on routing information contained in an SS7 message. To properly address and transport a signaling message, signaling points are uniquely identified by a Signaling Point Code (SPC). SPCs are contained in the routing label of the signaling message. An SPC is a 24-bit address that is partitioned in three fields: network identifier, network cluster and the network cluster member. The value in the network identifier field directly identifies the network to which a point code belongs.
A cluster is defined as a group of SPs that directly home on a mated STP pair. There can be a maximum of 255 SPs per cluster. This limit can be easily exhausted. Therefore, introduction of a new SP with a new SPC can be very problematic. According to ANSI standard T1.111.4, all SS7 messages received by network provider interconnecting STP must have an MTP L3 Network Indicator field encoded to National Networks (meaning message is formatted for national networks).
Only one primary SPC can be associated with an MTP L3 Network. The Multiple MTP Internal Networks capability of this invention allows to have up to 32 MTP internal networks, but more could be established, each associated with one primary SPC and some secondary SPCs. The SPC in each of 32 networks is used to create it's own linkset and routeset data. All information defined per each network is independent of each other and may represent specific configuration. For Shared Point Code mapping, a logical mapping mechanism is implemented to associate one network to another so that routing is or is not permitted from one network to another. In the past, migrating from one switch to another required extensive use of physical links and substantial database configuration changes.
For redundancy needs, SCPs and STPs are usually deployed in mated pairs. Links between signaling points are also typically provisioned in pairs. An SSP typically has links to two separate STPs. SS7 links are of different logical functions. These links are known as A-links, B-links, C-links, D-links, E-links, and F-links each having a particular function. For example, A-links connect a signaling end point (e.g. STP or SSP) to an STP. An F-link typically connects two signaling end points (i.e., SSPs and SCP) and not usually used in networks with STPs, however F-links can be employed to provide testing capabilities.
PSTN circuit-based-switches commonly employ time-division-multiplexing (TDM) techniques to facilitate call connections throughout the network and employ SS7 to facilitate the signaling. TDM is a circuit-oriented transmission mechanism and reaches capacity constraints and throughput limitations quickly relative to packet-based transmission mechanisms. Historically, TDM has been a dominant technology and has broad deployment penetrations worldwide. Substantial financial and technological investment currently exists in TDM switches.
The advancement of technologies has propelled packet-based switching transmission systems to levels of service that make it possible to aggregate communications for voice and data together in a packet switch. In general, packet-based switching networks have greater overall bandwidth potential compared to circuit-switched networks. Further, packet-based switching is finding strong acceptance in such services as the Internet, banking, video services, general business commerce and the like.
The advent of soft-switches, those which typically utilizes Internet Protocol (IP) and/or Automatic Transfer Mode (ATM) technology to unify data and voice switching at very high bandwidth levels provides new telecommunication and data capabilities and thus provides a very attractive alternative to the more ubiquitous, circuit-based-switches. Soft-switches typically employ digital signal processors (DSPS), high-powered microprocessors, or even custom silicon to process the packet message traffic for both voice and data.
Soft-switches are becoming reasonable and desirable choices for PSTNs throughout the world and even for private networks. The overall costs for soft-switches are typically lower than those of comparable circuit-based switches. Further, greater development potential exists for software-driven applications to be combined or offered as options in soft-switching architectures as compared to their traditional circuit-based-switch counterparts. Soft-switches, as the name implies, rely extensively on embedded and layered software instead of traditional hardware-based solutions to create logical associations, easily maintainable and extendible features, and to provide unique applications and solutions in general. PSTN operating companies, as well as private corporations, have begun to invest heavily in soft-switch technologies to achieve these advantages over circuit-based switches.
Major obstacles to the conversion of switching network infrastructures exist, including the investment in circuit-based and the technical difficulties involving the actual physical conversion of a circuit-based switch to packet-based switch, while it is in operation and processing subscriber calls, and without significant disruption in services. Telecommunications service disruption is extremely undesirable to customers, even for relatively short periods of time. Additionally, adding new switches in a network, for capacity or technology reasons, can cause substantial support and database configuration update burdens on operating companies. Adding new equip
Chaney Charles
Nekrasovskaia Sofia
Hong Harry S.
Siemens Information and Communication Networks Inc.
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