Multiplex communications – Communication techniques for information carried in plural... – Adaptive
Reexamination Certificate
1999-12-17
2004-03-30
Olms, Douglas (Department: 2661)
Multiplex communications
Communication techniques for information carried in plural...
Adaptive
C370S522000, C370S465000
Reexamination Certificate
active
06714560
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to providing SS7 signalling transport over a high speed network and, more particularly, over an asynchronous transfer mode (ATM) network.
BACKGROUND TO THE INVENTION
The following acronyms will be used throughout this document:
ATM Asynchronous Transfer Mode
AESA ATM End System Address
CCS Common Channel Signalling
CCSAN Common Channel Signalling ATM Network
DPC Destination Point Code
DS0 Digital Signal, Level 0 (64 kb/s)
DS# Digital Signal, Level×(Note: In practice “DS#” is used synonymously with “T#”, e.g. DS1 and T1)
E1 The European counterpart to T1 (32 channels, 64 kbps per channel, 2.048 Mbps total throughput)
HSLs High Speed Links
ITU International Telecommunication Union
LNP Local Number Portability
Mb/s Megabit-per-second
MSU Message Signalling Unit
MTP Message Transfer Part
MUX Multiplexor/De-Multiplexor
PSTN Public Switched Telephone Network
PVC Permanent Virtual Channel
QoS Quality of Service
SAAL Signalling ATM Adaption Layer protocols
SCPs Service Control Points
SPVC Soft Permanent Virtual Circuit
SSCOP Service Specific Connection Oriented Protocol
SS7 Common Channel Signalling System 7
SSPs Service Switching Points
STPs Signalling Transfer Points
SVC Switched Virtual Circuit
T1 Also known as DS1; 24 DS0 channels at 64 kb/s, and one 8 kb/s synchronisation channel. Total transmission rate is therefore 64 kb/s×24+8 kb/s×1=1.544 Mb/s.
VCI Virtual Channel Identifier
VCC Virtual Channel Connections
VPI Virtual Path Identifier
A Public Switched Telephone Network (PSTN) is, conventionally, comprised of two networks a voice/data network and a signalling network. The signalling network carries address information for call set-up and tear down. A global standard for telecommunications defined by the International Telecommunication Union (ITU), Telecommnunication Standardisation Sector (ITU-T) for common channel signalling is the Common Channel Signalling System 7 (SS
7
), a North America version of which has been defined by the American National Standards Institute in T1, the contents of which are hereby incorporated herein; and a corresponding European version of the standard has also been defined by the European Telecommunications Standards Institute.
An SS7 signalling network is made up of different nodes (also referred to as network elements). The nodes include Signalling Transfer Points (STPs), Service Control Points (SCPs) and Service Switching Points (SSPs). These nodes are interconnected by a network of signalling links and together provide a variety of telephony services. For instance, the SS7 network, and its associated protocol, enables, for example: basic call set-up, management and tear down; wireless services; local number portability (LNP); toll-free (800, 888, 877) service; toll (900) service; call forwarding; call display; and three-way calling.
SSPs are switches that originate, terminate or tandem calls. An SSP sends signalling messages to other SSPs to set-up, manage and release voice circuits required to complete a call. An SCP, which provides central database services, may be queried by an SSP to determine how to route a particular call such as, for instance, a toll-free call. An SCP provides to the SSP a response, such as the routing number associated with the toll-free number dialled. This query and response occur over SS7 links. STPs, which also form part of the SS7 network, act as routers to incoming signals received from either an SSP or an SCP. These incoming signals are then routed to the appropriate node based on routing information contained within an SS7 message. Acting as a network hub, an STP improves the operation of the SS7 network by reducing the need for direct links between SSPs.
Currently, most of these SS7 links between nodes are running at speeds of 56 Kb/s or 64 Kb/s. High speed links (based on standards such as GR-2878) are emerging to allow greater bandwidth between the various nodes. However, this bandwidth is often not utilised effectively. Moreover, a fault in the hard-wired connection between nodes results in degradation of the service provided, requires a large amount of manual intervention to rectify, and increases the risk of network failure.
Accordingly, it is desired to provide a system which addresses some of these shortcomings.
SUMMARY OF THE INVENTION
The invention provides for multiple virtual channels to be provisioned over a single High Speed Link (HSL) connecting an SS7 node to an Asynchronous Transfer Mode (ATM) network. Each virtual channel on the HSL is dedicated to the transmission of SS7 signalling data between this SS7 node connected to the HSL and another node in communication with the ATM network. A logical connection, which may be, for example, a Permanent Virtual Channel (PVC) or Switched Virtual Circuit (SVC), is provisioned on the ATM network between the SS7 node and the other SS7 node. The invention may provide for direct communication between an SSP and SCP, without the need for an STP intermediary. Further, the invention may provide for a fully associated SS7 network with a reduction in the amount of physical links that would be required in a fully associated conventional SS7 network. The invention may also provide, should a logical connection be configured as an SVC, and relying upon the inherent benefits of an ATM network, for re-routing of SS7 data in the event of a failure of the logical connection.
According to another aspect of the invention, there is provided a method for transmitting SS7 signaling data between a node and an Asynchronous Transfer Mode (“ATM”) network, the SS7 signaling data destined for a plurality of physical links in communication with the ATM network, the method comprising: for each of the plurality of physical links, establishing a virtual channel over a multiplexing physical link connecting the node and the ATM network; providing an identifier unique to each of the established virtual channels; encapsulating the SS7 signaling data into ATM cells incorporating the identifier corresponding to a destined one of the plurality of physical links; transmitting encapsulated data from the node to the ATM network over the multiplexing physical link on the virtual channel corresponding to the identifier in the encapsulated data.
According to another aspect of the invention, there is provided a method for transmitting SS7 signalling data between a first, a second and a third node over an Asynchronous Transfer Mode (“ATM”) network, the method comprising: establishing a first physical link between the first node and ATM network; establishing a second physical link between the second node and the ATM network; establishing a third physical link between the third node and the ATM network; provisioning a logical connection on the ATM network between each of the first, the second and the third physical links with the ATM network; provisioning a first virtual channel on the first physical link for the second node; provisioning a second virtual channel on the first physical link for the third node; provisioning a first virtual channel on the second physical link for the first node; provisioning a second virtual channel on the second physical link for the third node; provisioning a first virtual channel on the third physical link for the first node; provisioning a second virtual channel on the third physical link for the second node; transmitting SS7 signalling data from the first node to the second node over the first virtual channel of the first physical link, the logical connection interconnecting the first virtual channel on the first physical link and the first virtual channel on the second physical link over the ATM network; transmitting SS7 signalling data from the first node to the third node over the second virtual channel of the first physical link, the logical connection interconnecting the second virtual channel on the first physical link and the first virtual channel on the third physical link over the ATM network; and transmitting SS7 signalling data from the second node to the third node ove
Daoud Naile S.
Drover Calvin E.
Mousseau Guy G.
Nortel Networks Limited
Olms Douglas
Pizzaro Ricardo M.
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