Multiplex communications – Communication techniques for information carried in plural... – Adaptive
Reexamination Certificate
1998-01-30
2001-11-06
Ton, Dang (Department: 2663)
Multiplex communications
Communication techniques for information carried in plural...
Adaptive
C370S221000, C370S229000, C370S230000, C370S231000, C370S410000, C370S466000, C370S465000, C370S522000, C370S524000
Reexamination Certificate
active
06314109
ABSTRACT:
FIELD OF THE INVENTION
The invention pertains to communication networks such as public switched telephone networks (PSTNs). The invention addresses the problem of minimizing the amount of network reconfiguration necessitated by the addition or augmentation of a device constituting a network node.
BACKGROUND OF THE INVENTION
Communication networks generally comprise nodes and linksets that connect the nodes to form the network. The basic elements of a conventional PSTN in a typical PSTN configuration are illustrated in FIG.
1
. As seen in
FIG. 1
, the network includes signal transfer points (STPs), service switching points (SSPs), and service control points (SCPs). An STP is a network hub that provides routing of messages between other network nodes. An SSP may be a network end point to which subscriber terminals are connected, or may be a tandem point that handles trunk traffic for other SSPs. An SCP is a network endpoint that provides database services to subscribers such as calling number identification, voice mail, and toll-free calling.
The STPs, SSPs and SCPs and their associated link sets are collectively referred to as the signaling side of the communication network. The primary functions of the signaling side of the network are to establish connections between SSPs and to provide data management for network services. Once a connection is established between SSPs, voice or other data originated from subscriber terminals is carried by trunks such as the trunk
10
shown in FIG.
1
.
It is typical in PSTNs to provide redundancy of STPs so that failure of an STP does not disable part of the network. STPs are typically deployed in mated pairs, such that each network node connected to an STP of a mated pair is also connected to the other STP of the mated pair. In the conventional PSTN illustrated in
FIG. 1
, it may be seen that each network node connected to STP A is also connected to STP A′, and each network node connected to STP B is also connected to STP B′.
Communications among network nodes in the signalling side of the network may be routed using point codes. A point code corresponds to a physical device that constitutes a network node. Communications between two network nodes include an originating point code (OPC) that identifies the node originating the message, and a destination point code (DPC) that identifies the node to receive the message. The ability of a node to receive a message from another node therefore requires knowledge of the node's point code at other nodes of the network. In the alternative, some messages may be routed using global title queries. A global title query specifies a logical address as the destination of the query, and a global title translation is performed on the query at an STP to determine a physical address for use as the DPC of the message.
Under some circumstances it is necessary or desirable to change or augment the device that constitutes a network node. For example, an existing device may be replaced by a new device in order to provide enhanced capabilities at that node. Similarly, a new device may be added to supplement an existing device, for example, to enable a wider range of services or to expand the number of link sets to the node. The new device may provide supplemental functions, and/or may also duplicate functions of the original device.
In accordance with conventional practice, a node is replaced by disconnecting all links to the existing device and reestablishing those links to the new device, which then assumes the point code of that node. However, this can have the undesirable effect of disabling part of the network during the replacement process. Alternatively, in accordance with conventional practice, a device may be replaced or supplemented by the addition of a new device having a new point code. However, this practice can have the undesirable effect of requiring reconfiguration of the other network nodes to recognize the new point code of the new node. Other conventional methods for adding or augmenting node devices are cumbersome and may entail disadvantages similar to those noted above.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to augment or replace node devices in a manner that is transparent to the remaining nodes of the network and that avoids disruption of network services.
This object is accomplished, in general terms, by introducing a replacement or augmentative node device as an adjunct to an existing node device. For purposes of the invention, the existing device will be referred to as a “host” device, and the replacement or augmentative device will be referred to as an “adjunct” device. For communication with other nodes of the network, the host and adjunct each maintain the point code of the host. As a result, the host-adjunct unit appears to the rest of the network to be a single node. For communication between the host and the adjunct, the adjunct maintains a unique adjunct point code.
It is a further object of the invention to provide a manner of replacing a node device that does not cause disruption of network services. In general terms, this object is achieved by providing the replacement device as an adjunct to the original device as described above. Linksets joining network nodes to the original device are then migrated to the replacement device in any order that avoids disruption of network services.
Various embodiments of the invention for accomplishing these objects are discussed in the detailed disclosure provided below.
REFERENCES:
patent: 5029165 (1991-07-01), Choi et al.
patent: 5048081 (1991-09-01), Gavaras et al.
patent: 5862129 (1999-01-01), Bell et al.
patent: 5926482 (1999-07-01), Christie et al.
patent: 5974133 (1999-10-01), Fleisher, III et al.
patent: 6079036 (2000-06-01), Moharram
Foley & Lardner
Nguyen Toan
Nortel Networks Limited
Ton Dang
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