Failure tolerant high density dial router

Details Failure tolerant high density dial router Failure tolerant high density dial router

1998-06-18

2001-12-11

Kizou, Hassan (Department: 2662)

Multiplex communications

Fault recovery

Bypass an inoperative switch or inoperative element of a...

C370S219000, C370S221000, C370S225000

Reexamination Certificate

active

06330221

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates a high density dial router and more particularly to a Fault Tolerant Dial Router (FTDR) that can be automatically reconfigured around faults while other independently operating subsystems in the dial router continue to process calls.
A dial router processes telephone calls from a Public Service Telephone Network (PSTN). The dial router formats received telephone calls into IP packets and routs the packets over a packet-based Local Area Network (LAN) or Wide Area Network (WAN). The PSTN serially multiplexes multiple telephone calls together into either PRI, channelized T
1
(CT
1
), or channelized T
3
(CT
3
) data streams or the European equivalent of CT
1
, which are referred to as CE
1
. The dial router accordingly includes PR
1
, CT
1
, CE
1
and/or CT
3
feature boards that separate out the individual calls from the data streams. Modems extract digital data from the individual telephone line channels. The router then encapsulates the digital data into packets that are routed onto the packet-based network, such as a fast-Ethernet LAN.
Some dial router architectures break the dial router system into many very small subsystems cards. Each subsystem has a complete set of line interface units. When a failure occurs, the whole subsystem card is decommissioned and manually swapped by an operator with a standby subsystem card at a later time. Even if a line interface unit is partially operational, it is fully decommissioned if a failure is detected. Another problem is that the number of boards in the dial router are substantially increased since one redundant card is provided for each subsystem card. This redundant architecture results in large and bulky dial routers.
Current dial routers provide little or no fault tolerance against failures that occur in the field. Upon encountering a failure, field service engineers typically swap out the entire dial router box. For example, when a single modem module in the dial router fails, the entire dial router box is turned off and the modem card replaced. When the dial router is shut down, all calls coming into the dial router are disrupted. Because the dial router handles a large number of calls at the same time, any failure, no matter how small, disrupts all the information (data, voice, etc.).
Accordingly, a need remains for a simple dial router architecture that reduces the disruption of calls caused by failures.
SUMMARY OF THE INVENTION
A fault tolerant dial router (FTDR) includes redundant subsystem resources that operate independently of telephone line interface connections, such as PRI, CT
1
, CE
1
and CT
3
interfaces. The redundant subsystem resources are switched active when a failure is detected in a currently activated dial router subsystem. Subsystem failures are automatically switched out under software control, providing uninterrupted service to users with limited performance loss.
The FTDR selectively detaches the PRI, CT
1
or CT
3
line interfaces from the “pool” of other subsystem resources inside the dial router box. The subsystem “pool” includes line framers, controllers and modem modules. The “pool” of resources typically include some redundancy so that one extra subsystem can be standing by for a given number of active subsystems.
Failures often occur in the line interface units, especially the CT
3
line interface that can handle up to 672 calls. The FTDR switches out a failed line interface unit and automatically switches in a redundant line interface unit.
The FTDR detaches the line interfaces from the “pool” of subsystem resources by using a DS
1
cross-connect switch (DCCS). The PRI, CT
1
, CE
1
or CT
3
line interface units converts modem, telephone, facsimiles or other types of calls to discrete DS
1
data streams. The DCCS is pre-programmed to route individual DS
1
data streams to subsystems and backup subsystems in the same feature card or to subsystems in other feature cards in the FTDR. DS
1
I/O lines connects together all the DCCS switches in the FTDR.
When a failure is detected anywhere in the system, the DCCS is automatically reconfigured to route the DS
1
data stream around the failed subsystem to another subsystem located elsewhere in the FTDR. If more failures are detected, the DCCS connects the DS
1
data stream around the new fault to another available subsystem resource. The DCCS reduces call disruptions in the dial router due to failures and requires substantially less standby hardware than other dial routers. The invention is targeted, but not limited to, dial routers. For example, the FTDR is ideal for use by Internet Service Providers (ISPs) to increase call reliability and reduce system down time.
The foregoing and other objects, features and advantages of the invention will become more readily apparent from the following detailed description of a preferred embodiment of the invention, which proceeds with reference to the accompanying drawings.


REFERENCES:
patent: 5301184 (1994-04-01), Uriu et al.
patent: 5436886 (1995-07-01), McGill
patent: 5488606 (1996-01-01), Kakuma et al.
patent: 5712854 (1998-01-01), Dieudonne et al.
patent: 5896370 (1999-04-01), Eckhoff et al.

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