Multiplex communications – Pathfinding or routing – Combined circuit switching and packet switching
Reexamination Certificate
1998-06-05
2002-10-15
Luther, William (Department: 2664)
Multiplex communications
Pathfinding or routing
Combined circuit switching and packet switching
C379S900000
Reexamination Certificate
active
06466570
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of accessing service resource items that are intended to be used in setting up bearer channels through a switched telecommunications system.
As used herein, the term “switched telecommunication system” means a system comprising a bearer network with switches for setting up a bearer channel through the network. The term “switched telecommunication system” is to be taken to include not only the existing public and private telephone systems (whether using analogue phones or ISDN-based), but also broadband (ATM) and other switch-based bearer networks that are currently being implemented or may emerge in the future. For convenience, the term “switched telecommunication system” is sometimes shortened herein to telecommunication system.
Reference to a “call” in the context of a switched telecommunication system is to be understood as meaning a communication through a bearer channel set up across the bearer network, whilst references to call setup, maintenance and takedown are to be taken to mean the processes of setting up, maintaining and taking down a bearer channel through the bearer network. Terms such as “call processing” and “call handling” are to be similarly interpreted.
The term “communication system” when used herein should be understood as having a broader meaning than switched telecommunication system, and is intended to include datagram-based communication systems where each data packet is independently routed through a bearer network without following a predetermined bearer channel.
BACKGROUND OF THE INVENTION
Telecommunication companies running PSTNs (Public Switched Telephone Networks) and PLMNs (Public Land Mobile Networks) are in the business of providing communication services and in doing so are providing increasing built-in intelligence in the form of “IN services” such as 800 number services and call forwarding. In contrast, the World Wide Web (WWW), which has seen explosive growth in recent times, is an example of an Internet-based global network providing complex information services. These two worlds, that of the large communications utilities and that of the highly dynamic, pioneer-spirit WWW information culture, are uneasy companions and each plans to encroach on the domain previously occupied by the others; thus telephony services will be offered over the WWW and information services over the public communication infrastructure.
The present invention proposes technologies for a more synergetic relationship between these two worlds than is currently envisaged and in order to place the present invention in context, a review will first be given of each of these two worlds.
Telephone Networks with IN Services
The Basic PSTN. The basic service provided by a PSTN (Public Switched Telephone Network) is the interconnection of two telephones (that is, setting up a bearer channel between the telephones) according to a called-party telephone number input at the calling-party telephone.
FIG. 1
is a simplified representation of a PSTN providing such a service. In particular, customer premises equipment, CPE,
10
(such as standard analogue telephones, but also more recently ISDN terminals) are connected through an access network
11
to switching points, SPs
12
. The SPs
12
form nodes in an inter-exchange network
13
made up of interconnecting trunks
14
and SPs that are controlled by control entities
15
in the SPs. The control effected by the control entities
15
is determined by signalling inputs received from the CPEs and other SPs, and involves call setup, maintenance and clearance to provide the desired bearer channel between calling CPE and called CPE. Conceptually, the PSTN may be thought of as a bearer network and a control (signalling) network, the function of the latter being to effect call control through the bearer network, namely the control of setup, maintenance and take down of bearer channels through the bearer network; in practice, the bearer and signalling networks may use the same physical circuits and even the same logical channels.
Thus, where the CPE is a traditional dumb telephone, control signalling between the CPE and its local SP is in-band signalling, that is, the signalling is carried on the same channel as used for voice; this signalling is interpreted and converted at the SPs
12
into signalling between SPs that uses a dedicated common-channel signalling network
16
(implemented nowadays using the SS
7
protocol suite). Where the CPE is an ISDN terminal, signalling is carried in a separate channel directly from the CPE on an end-to-end. Modern SPs use the ISUP (ISDN User Part) SS
7
protocol for inter-exchange call control signalling whether the CPE is a standard telephone or an ISDN terminal.
Telephone Numbering Plans—As certain aspects of the present invention are influenced by the structuring of telephone numbers, a brief description will now be given of the structuring of such numbers. Telephone numbers form an international, hierarchical addressing scheme based on groups of decimal digits. The top level of the hierarchy is administered by the ITU-T, which has allocated single-digit numeric codes to the major geographic zones (for example “1” for North America, “2” for Africa, “3” for Europe, “4” for Europe, “5” for South America and Cuba, etc.). Within each zone countries are assigned 2 or 3 digit codes, so that within zone 3 France is “33”, and within zone 4 the UK is “44”. Administration of the numbering plan within a country is delegated to a national body, such as the Office of Telecommunications (“Oftel”) in the UK. The following further description is based on the UK numbering plan, but the scheme described will be recognised as having widespread applicability.
In the UK all national numbers are prefixed by a code from 01 to 09 (the ‘0’ prefix is dropped in international dialling). The currently assigned codes are “01” for Geographic Area Codes, “02” for Additional Geographic Area Codes, “04” for Mobile Services, “07” for Personal Numbers, and “08” for Special Service (freephone, information). Normal wireline PSTN subscriber telephone numbers are allocated from the Geographic Area Code codes, and currently only codes prefixed by 01 are allocated. Geographic area codes are presently 3 or 4 digits (excluding the leading ‘0’) and there are currently 638 geographic areas each with its own code. A full national UK dialled number takes two forms:
0
171
634 8700
area code
local number (7 digit)
0
1447
456 987
area code
local number (6 digit)
The first case has the ‘0’ prefix, a 3 digit area code and a 7 digit local number, and the second case has the ‘0’ prefix, a 4 digit area code, and a 6 digit local number. Further interpretation of the local number will take place within the area exchange, as even a 6 digit address space is too large for a single switch, and for a typical local area several switches may be needed to host the required number of subscriber lines. This interpretation is opaque and is a matter for the area service provider.
In the current PSTN the inherently hierarchical and geographic interpretation of telephone numbers is mirrored by the physical architecture of the network. A telephone number is structured in a way that makes it easy to route a call through the network. At each step, the prefix of the number provides information about the current routing step, and the suffix (perhaps opaquely) provides information about subsequent routing steps; as long as a switch knows how to parse a prefix and carry out a routing step, it does not need to understand the content of the suffix, which is left for subsequent routing steps. For this reason the international and national switching fabric is also organised hierarchically.
Intelligent Networks. Returning now to a consideration of the current telephone network infrastruture, in addition to basic call handling, an SP may also serve to provide what are called IN (Intelligent Network) services; in this case the SP is termed a service switching point, SSP. An SSP
25
is arranged to suspend call pro
Bouthors Nicolas
Low Colin
Seaborne Andrew Franklin
Hewlett--Packard Company
Luther William
LandOfFree
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