Error detection/correction and fault detection/recovery – Pulse or data error handling – Transmission facility testing
Reexamination Certificate
1995-02-08
2001-09-25
Chung, Phung M. (Department: 2133)
Error detection/correction and fault detection/recovery
Pulse or data error handling
Transmission facility testing
Reexamination Certificate
active
06295615
ABSTRACT:
BACKGROUND OF THE INVENTION
With modern telecommunications networks, a customer such as a business customer may select from an array of communication services aimed at providing cost-effective connections to geographically-dispersed sites maintained by the customer. The various available alternatives range, at one extreme, from ubiquitous direct dialing over the public network to, at the other extreme, specially provisioned private networks. Because of the vagaries of direct dialing, such as call blocking and connect-time cost, a customer with critical communication requirements most often selects the private network option. In particular, there has recently been a demand for large private data networks to connect, for example, numerous terminal devices such as reservation terminals to an arrangement of centrally located, fault-tolerant host computers so as to service consumer transactions. Data networks are generally implemented on private network facilities because, as exemplified above, computer applications necessitate continuous, on-line connections of terminals to centralized computers.
One common method of implementing a private line network is to interconnect various customer sites with DS
1
digital facilities wherein numerous channels are multiplexed to generate a DS
1
signal suitable for carriage over the high-rate links. A channel may have more than one DS
0
(i.e. N×DS
0
, where 1≦N≦24). Each channel embedded in the DS
1
will hereinafter be referred to as a fractional DS
1
channel. At the destination end (far end), the high-rate signals are demultiplexed to recover the fractional DS
1
channels. Oftentimes, the DS
1
facilities are provided by a common carrier over carrier-owned digital facilities on a long-term or semi-permanent basis. DS
1
facilities are provisioned by the common carrier through static cross-connect switches generally referred to as a Digital Access and Cross Connect System (DACCS). Unlike telephone-carrier switches which handle telephone call setups, a DACCS establishes routes which may be connected for years.
Efficient use of DS
1
facilities requires channel grooming. Because of channel grooming, the fractional DS
1
channels which are carried over each DS
1
link may not all be derived from the same customer site. Specifically, the fractional DS
1
channels that form an out-going DS
1
signal from a DACCS are usually composed of fractional DS
1
channels that originate from a plurality of in-coming DS
1
facilities that come from different customer sites. Typically, facility failures in private networks require restoration efforts that are correspondingly sophisticated and time-consuming. Accordingly, facility engineers have sought techniques to provide for efficient and automated restoration of facilities when deleterious service conditions are detected.
Recently, a service has been introduced by one inter-exchange carrier which provides switched digital data service at fractional DS
1
speeds. In using the service, a customer is able to establish a back up dial-up link to restore a failed private line fractional DS
1
channel. However, such a service has the disadvantage of blocking, that is, a link between the end points is not always available. Moreover, it takes at least a few seconds to establish a connection over such a link each time a dial-up is attempted. In the period of a few seconds, a significant loss of data can occur.
A need exists in the art for a relatively simple technique for efficiently and automatically restoring telecommunications service over a fractional DS
1
channel while providing essentially uninterrupted communications in the event that a DS
1
facility, which carries that channel in a private line network, fails.
SUMMARY OF THE INVENTION
These deficiencies as well as other shortcomings and limitations are obviated, in accordance with the present invention, by a device that couples to pairs of redundant digital networks and switches individual channels, e.g., bi-directional fractional DS
1
channels, to the alternative network whenever errors, such as failures of a DS
1
facility, are detected in the active network.
Broadly speaking, with respect to the circuitry aspect of the present invention, a pair of devices are situated at near and far ends of a digital link such as a fractional DS
1
channel. Each of these devices includes: detection circuitry to detect the presence of a fault indication signal, such as a digital access cross-connect system (DACCS)-generated trouble code, in any of the fractional DS
1
channels arriving over the network pair; and switching circuitry to transfer the corresponding fractional DS
1
channels having the trouble code from the active network to fractional DS
1
channels in the alternate network. The use of paired devices spanning both ends of the fractional DS
1
channel ensures that both directions of propagation are protected from fault conditions that could arise within either network and adversely affect transmission in either direction over either one of the links. In addition, each device also includes transmitter circuitry to transmit two identical versions of data generated by terminal equipment which then are transmitted to the far-end over primary and secondary networks.
In a particular embodiment, each device relies on detecting a so-called DACCS “trouble code” which is inserted by a digital access cross-connect system on all outgoing DSOs at the occurrence of a DS
1
facility failure and then, based upon the presence of this code, automatically switching a fractional DS
1
channel from an active route to a corresponding fractional DS
1
channel in the other DS
1
provided by the alternate network in order to restore service. It has been known for several years that a DACCS will automatically insert a pre-defined trouble code in each outgoing DSO which is affected by a facility failure. However, the art appears to be devoid of any teachings showing that these codes have ever been commercially used in switching between primary and alternate routes for two redundant facilities, each of which is carried through a separate network, in order to restore telecommunications service in the event the active route fails.
The invention further comprises a digital device for interconnecting a terminal link to both first and second communication networks. Both the terminal link, and the first and second communication networks are arranged to propagate a plurality of corresponding channels, wherein each of the communication networks is arranged to generate and then to transmit a fault indication signal over any of its corresponding channels upon detection of a fault condition affecting any of the corresponding channels in the first or second networks. The first network is initially the active network and the second network is initially the alternate network. The device comprises a means, responsive to the terminal link, for transmitting the channels carried by the terminal link simultaneously over both the first network and the second network. The device has a means, responsive to both the first network and the second network and coupled to the terminal link, for monitoring each channel in the active network to determine the presence of the fault indication signal. Upon detection of the fault indication signal, the responsive device replaces each channel from the active network having the fault indication signal with the corresponding channel from the alternate network so as to thereby supply the terminal link with high availability channels.
The invention further comprises a digital network having a plurality of channels for interconnecting a near end and far end customer transceivers, wherein one end of the channel is the near end and the other end is the far end. The transceivers transmit fractional DS
1
communication channels to and receive fractional DS
1
communication channels from the digital network. The digital network comprises autonomous primary and secondary digital communication networks each composed of DS
1
links arranged to propagate a plurality o
Ball Harley R.
Chung Phung M.
Funk Steven J.
Sprint Communications Company L. P.
LandOfFree
Automatic restoration of communication channels does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Automatic restoration of communication channels, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Automatic restoration of communication channels will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2453731