Multiplex communications – Communication techniques for information carried in plural... – Adaptive
Reexamination Certificate
1998-12-04
2001-11-27
Kizou, Hassan (Department: 2662)
Multiplex communications
Communication techniques for information carried in plural...
Adaptive
C370S469000, C370S524000
Reexamination Certificate
active
06324183
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to telecommunications systems and methods and more particularly to systems and methods for communicating in a Signaling System 7 network.
BACKGROUND OF THE INVENTION
Modern telecommunications networks generally include two separate communication pathways or subnetworks. The first is a voice network that handles the transmission of voice or other information between users. The second is a signaling network that facilitates the dynamic linking of a plurality of voice network circuits, such that a voice-type connection is established between a calling party and a called party. These functions are generically referred to as call setup and call teardown. Additionally, the signaling network provides a framework through which non-voice related information may be transported in a manner that is transparent to the user. This signaling technique is often referred to as “out of band” signaling, where the term “band” implies voice band. Common examples of such out of band data transport are the access of 800 number database services, calling card verification services and caller ID services.
In order to provide consistent and reliable communication across the signaling network infrastructure, a common or standard digital signaling protocol known as Signaling System 7 (SS7) has been developed. SS7 is an out of band common channel signaling system that uses labeled messages to transport circuit related signaling information, non-circuit related signaling information, network resident database service information and other information that may be used for the establishment of communication services.
From a hardware perspective, an SS7 network includes a plurality of SS7 nodes, generically referred to as Signaling Points (SP), that are interconnected using signaling links, also referred to as SS7 links At least three types of SPs are provided in an SS7 network: Service Switching Points (SSP), Signal Transfer Points (STP) and Service Control Points (SCP).
An SSP is normally installed in tandem or Class 5 offices. The SSP is capable of handling both in-band signaling and SS7 signaling. An SSP can be a customer switch, an end-office, an access tandem and/or a tandem. An STP transfers signaling messages from one signaling link to another. STPs are packet switches and are generally installed as mated pairs. Finally, SCPs control access to databases such as 800 number translation, 800 number carrier identification, credit card verification, etc.
Signaling datalinks are transmission facilities used to connect SPs together. They are dedicated bidirectional facilities operating at 56 kbps in the U.S. and Canada and at 64 kbps when clear channel capability is deployed. Normally, every link has a mate for redundancy and enhanced network integrity.
Signaling datalinks include access links or “A” links that connect SSPs to STPs and that connect SCPs to STPs, as shown in FIG.
1
. Bridge links or “B” links are used to connect mated STPs to other mated STPs that are at the same hierarchical level, as shown in FIG.
2
. Cross links or “C” links connect mated STPs together, as shown in FIG.
3
. They are used for passing messages between STPs when signaling network failures are encountered.
Diagonal links or “D” links connect STPs of different hierarchical levels, as shown in FIG.
4
. Extended links or “E” links connect SSPs to STPs that are not within their associated local STP area, as shown in FIG.
5
. Finally, fully associated links or “F” links connect SSPs directly together without STPs, as shown in FIG.
6
.
FIG. 7
is a block diagram of a two-level SS7 network including a summary of possible link deployment.
SS7 also includes a network protocol. As a protocol, SS7 defines a hierarchy or structure of the information contained in a message or data packet that is transmitted between SPs of an SS7 network over signaling links. This internal data structure is often referred to as an SS7 protocol stack which includes the following four SS7 levels:
Level 1: The Physical Level
Level 2: The Datalink (or Link) Level
Level 3: The Network Level
Level 4: The User Level
The physical level, also referred to as the Message Transfer Part (MTP) level 1, is the lowest or most fundamental level and is the first level that is used to interpret and process an incoming message. This level determines and/or provides the electrical characteristics to transmit the digital data over the interface being used. Following interpretation/processing, the incoming message is passed up the stack to the datalink level.
The datalink level, also referred to as MTP level 2, resides adjacent and above the physical level and is responsible for providing the SS7 link with error detection/correction and properly sequenced delivery of SS7 message packets. Following interpretation/processing, the incoming message is passed up the stack to the network level.
The network level, also referred to as MTP level 3, resides adjacent and above the datalink level and is responsible for message packet routing, message packet discrimination, and message packet distribution. Functionally, message discrimination determines to whom the message packet is addressed. If the message contains the local address of the receiving SP, then the message is passed on to message distribution. If the message is not addressed to the local SP, then it is passed on to the message router. Following interpretation/processing, the incoming message is passed up the stack to the user part level.
The user part level resides adjacent and above the network level. The user part level may include many distinct parts including a Transaction Capability Application Part (TCAP), an ISDN User Part (ISUP), and a Signaling Connection Control Part (SCCP).
The above description has assumed that an incoming message is being processed. An outgoing message is passed through the protocol stack in the opposite direction, entering at the user part level and exiting from the physical level.
FIG. 8
illustrates SS7 protocol architecture relative to SS7 levels and relative to standard Open System Integration (OSI) layers. The hardware elements and protocols of an SS7 network are well known to those having skill in the art, and need not be described further herein.
A high performance STP is marketed by the assignee of the present application as the Eagle® STP. A block diagram of an Eagle® STP is shown in
FIG. 9. A
detailed description of the Eagle® STP may be found in the
Eagle® Feature Guide
PN/9110-1225-01, Rev. B, January 1998, published by Tekelec, the disclosure of which is hereby incorporated herein by reference. As described in this publication, an Eagle® STP
900
includes the following subsystems: a Maintenance and Administration Subsystem (MAS)
910
, a communication subsystem
920
and an application subsystem
930
. The MAS
910
provides maintenance communications, initial program load, peripheral services, alarm processing and system disks. The communication subsystem
920
includes an Interprocessor Message Transport (IMT) bus that is the main communication bus among all subsystems in the Eagle® STP
900
. This high speed communications system functions as two 125 Mbps counter-rotating serial buses.
The application subsystem
930
includes application cards that are capable of communicating with the other cards through the IMT buses. Three types of application cards are presently included: a Link Interface Module (LIM)
950
that provides SS7 links and X.25 links, an Application Communication Module (ACM) that provides a TCP/IP interface over Ethernet, and an Application Service Module (ASM)
940
that provides global title translation, gateway screening and other services. A Translation Service Module (TSM) may also be provided for local number portability.
The LIM provides level 1 and some level 2 functions on SS7 signaling links. The ACM provides access to a remote host for an STP LAN feature, described below. The ACM provides unidirectional access from the STP to a remote host for the STP LAN feature. Unidirectional connection from
Brendes Dan Alan
Miller Paul Andrew
Ravishankar Venkataramaiah
Sprague David Michael
Jenkins & Wilson, P.A.
Kizou Hassan
Tekelec
Tsegaye Saba
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