Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1998-12-21
2002-09-24
Cangialosi, Salvatore (Department: 2732)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S410000
Reexamination Certificate
active
06456626
ABSTRACT:
FIELD OF THE INVENTION
This invention pertains to connections on communication networks, and, more particularly, to the transparent reconnection of interrupted connections on communication networks.
BACKGROUND OF THE INVENTION
Communication systems usable for voice and data are known in the art, including POTS (“plain old telephone service”) systems which make hard point-to-point connection. In recent years, network-based systems with dynamic routing capabilities have been introduced, in which data is divided into “packers” or “frames”. Each packet or frame of data contain an indication of its destination, wherein the network forwards each frame or packet according to its embedded destination.
A high-level view of a typical network is shown in
FIG. 1. A
network
10
interconnects a plurality of network interfaces
20
which may be at different geographical locations. A plurality of customer premises equipment (CPE)
30
are connected, and located proximate to each network interface
20
. CPE
30
may include such end-user devices as data terminals or voice telephone handsets. A CPE
30
at a particular location (the “source”) may initiate communication with a CPE
30
at another location (the “destination”) through the source network interface
20
, the network
10
, and the destination network interface
20
.
In computer-based switching networks employing frame relay, packet switching, and the like, the communication links are not based on POTS-style hard connections. In such networks, the communication links are often referred to as “virtual circuits”.
FIG. 2
depicts a portion of a communication network environment that will be taken as exemplary in discussing the present invention. Only two of a possible plurality of subscriber locations or sites are shown. Designated as LOCAL and REMOTE, the subscriber locations or sites may be interconnected by network
10
. Each subscriber site, LOCAL and REMOTE, has a network interface (l
40
and
180
respectively) associated therewith. The LOCAL and REMOTE sites each have at lean one CPE
130
and
170
respectively. The LOCAL and REMOTE sites also each have at least one type of end-user equipment, such as data terminals
110
,
112
etc, and data terminals
160
,
162
etc. Those skilled in the art appreciate that CPEs
130
and
170
typically include computer chips or similar intelligence for interfacing end-user equipment to network interfaces
140
and
180
and the methodology for such interfacing is known in the art.
An embodiment of the present invention has been implemented in a system that functions according to ITU Q.933 protocol or other conventional signalling protocol specification, such as Q.2931.
FIG. 3
depicts a scenario known to those skilled in the art in which it is assumed, by way of example, that terminal
112
at the LOCAL site requests to communicate with terminal
162
at the REMOTE site. CPE
130
receives the request (including address information for terminal
162
) from terminal
112
, and issues a Q.933 (or other conventional signalling specification SETUP message to network interface
140
. By means known to those in the art, network
10
routes the SETUP message to network interface
180
, since that is the network interface associated with terminal
162
. Network interface
180
passes the SETUP message to CPE
170
, which establishes data connection (over a preexisting physical connection) with terminal
162
. CPE
170
originates a Q.933 CONNECT message, which is returned via network interface
180
, network
10
, and network interface
140
to CPE
130
. A “call” is then in session between the two terminals.
FIG. 4
depicts another scenario known to those skilled in the art and relevant to the present invention, in which terminal
162
at the REMOTE location requests communication with terminal
112
at the LOCAL location. Message flow is the reverse of that shown in
FIG. 3
, but likewise results in a call being is session between the two terminals.
In communication system, calls are sometimes interrupted because of equipment failure, interruption of the transmission paths comprising network
10
, tampering (whether inadvertent or deliberate), and so forth. Means are known is the art for re-establishing dropped connections. For example, many types of communication channels monitor the primary link of a call and, upon detecting that the primary link has gone down, can perform a switchover to a backup link. Such communication channels can further detect when the primary link recovers, and can switch back to the primary link, taking the backup link down again. However, is the process of making these switchovers, existing call sessions are dropped and must be reinitiated by the end user.
Thus, there is a need for a communication system that can reconfigure itself to restore a connection without dropping existing call sessions. There is a further need for a communication system that can reconfigure itself to restore a connection without losing a significant portion of a call.
Then and other objects of the invention will become apparent to those skilled in the art from the description which follows.
SUMMARY OF THE INVENTION
In one embodiment, the present invention provides for a method of reestablishing virtual circuits after the interruption thereof. Specifically, in a communication system comprising a network with a plurality of interconnectable interface ports; a plurality of customer premises equipment (CPE), each selectively connectable to at least one of said interlace ports; a plurality of terminals connected to each of said CPEs and being selectively operable as a source terminal to issue a setup request through its associated CPE for requesting connection to a terminal connected to a different CPE and operable as a destination terminal; wherein each of the interface ports an responsive to a setup request from a source terminal to connect itself via the network to a second interface port and to direct the second interface port to connect to a CPE associated with a requested destination terminal thus forming a virtual circuit between the source terminal and the requested destination terminal; and wherein each CPE is able to determine whether a virtual circuit is interrupted, the invention provides for the following steps to reestablish the virtual circuit after interruption thereof; (i) upon formation of a virtual circuit between a source terminal and a destination terminal, providing information descriptive of the virtual circuit to the source CPE; (ii) storing that virtual circuit information in the source CPE; (iii) upon determining that the virtual circuit is interrupted, establishing a connection between the source CPE and a third interface port; (iv) sending a setup request from the source CPE to the third interface port, which setup request includes the stored virtual circuit information; and (v) establishing a connection in response to the stored virtual circuit information via the network between the third interface port and the second interface port, thereby reestablishing the virtual circuit between the source terminal and the destination terminal.
In a preferred embodiment, when the virtual circuit is interrupted, the second interface port places the virtual circuit in a wait-for-backup mode. Upon expiration of a predetermined time, preferably a time longer than the time anticipated to reestablish the virtual circuit, if the virtual circuit is still in wait-for-backup mode, the second interface port drops the virtual circuit. Likewise, if the virtual circuit is reestablished, the second interface port removes the virtual circuit from the wait for backup mode.
In another embodiment, the invention provides a method for establishing a “tunnel” virtual circuit and storing information about the tunnel virtual circuit at the CPE associated with the source terminal, and that establishing “encapsulated” virtual circuits within the tunnel virtual circuit, also storing information about the encapsulated virtual circuits at the CPE associated with the source terminal. After failure of the t
Mayer Richard K.
Sultan Nevein
Whiting David
Wilbur Greg
Cangialosi Salvatore
Gibbons Del Deo Dolan Griffinger & Vecchione
Nortel Networks Limited
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