Switching system reliability

Claim 2

In an arrangement comprising means for selectively providing paths among a plurality of call switching means, a method of processing calls comprising selecting, for each call between first and second ones of said call switching means, an available path of said providing means between said first and second call switching means, and establishing said selected path through said providing means when said selected path is not already established, said selecting comprising in a first call processing mode, selecting said available path without reference to whether said available path is presently established through said providing means, in a second call processing mode, selecting said available path from only established paths of said providing means between said first and second call switching means.

Claim 3

A method in accordance with claim 1 further comprising assigning said selected path for said each call.

Claim 4

A method in accordance with claim 2 further comprising in response to said assigning, marking said assigned path unavailable, and in response to the end of said each call, marking said assigned path again available.

Claim 5

A method in accordance with claim 1 further comprising removing an established path of said providing means only as necessary to establish a selected path through said providing means.

Claim 6

A method in accordance with claim 1 further comprising changing from said first to said second call processing mode in response to detection of an inability to perform said selecting in said first mode.

Claim 7

A method in accordance with claim 1 further comprising changing from said first to said second call processing mode in response to detection of an inability to perform said establishing.

Claim 8

A method in accordance with claim 1 further comprising in response to detection of an inability to perform said selecting in said first mode, establishing a predetermined plurality of paths through said providing means between said first and said second call switching means, and after establishing said predetermined plurality of paths, performing said selecting in said second mode.

Claim 9

A method in accordance with claim 7 wherein each of said predetermined plurality of paths is established in response to a call between said first and second call switching means and remains established for use for future calls.

Claim 10

A method in accordance with claim 7 wherein said predetermined plurality of paths are established after said detection but not in response to individual calls.

Claim 11

A method in accordance with claim 1 further comprising in response to detection of an inability to perform said selecting in said first mode, determining the established paths between said first and said second call switching means, and after said determining, performing said selecting in said second mode.

Claim 12

A method in accordance with claim 10 wherein said determining comprises said first call switching means transmitting a path destination request on each established path from said first call switching means through said providing means, and said first call switching means determining said established paths between said first and second call switching means based on path destination responses defining said second call switching means transmitted from said second call switching means in response to path destination request transmitted by said first call switching means.

Claim 13

A method in accordance with claim 1 further comprising in response to detection of an inability to perform said establishing, determining the established paths between said first and said second call switching means, and after said determining, performing said selecting in said second mode.

Claim 14

A method in accordance with claim 12 wherein said determining comprises said first call switching means transmitting a path destination request on each established path from said first call switching means through said providing means, and said first call switching means determining said established paths between said first and second call switching means based on path destination responses defining said second call switching means transmitted from said second call switching means in response to path destination requests transmitted by said first call switching means.

Claim 15

A method in accordance with claim 1 further comprising maintaining stored data defining the presently established paths through said providing means between said first and said second call switching means and the availability status of said presently established paths, and performing said selecting in said second mode with reference to said stored data.

Claim 16

A method in accordance with claim 1 further comprising maintaining in each of said call switching means stored data defining the presently established paths through said providing means from said each call switching means to the other ones of said call switching means and the availability of the presently established paths, and performing said selecting in said second mode based on the stored data maintained in said first and second call switching means.

Claim 17

A method in accordance with claim 15 wherein said performing said selecting in said second mode comprises for a given call between said first and second call switching means, said first call switching means performing said selecting in said second mode with respect to the stored data maintained in said first call switching means but subject to a rejection of said selecting in said second mode by said second call switching means.

Claim 18

A method in accordance with claim 1 wherein said providing means comprises first means for selectively providing paths among said plurality of call switching means and second means also for selectively providing paths among said plurality of call switching means, wherein said available path selected in said first mode is selected from paths of said first means,and wherein said available path selected in said second mode is selected from paths of said second means.

Claim 19

A method in accordance with claim 1 wherein said providing means comprises first means for selectively providing paths among said plurality of call switching means and second means also for selectively providing paths among said plurality of call switching means, wherein said available path selected in said first mode is selected from paths of said first and second means, and wherein said available path selected in said second mode is selected from paths of said second means.

Claim 20

In an arrangement comprising a plurality of call switching means each for communicating in an associated plurality of channels and switch means for providing switched connections among said call switching means such that each of said channels associated with any given one of said call switching means is connectable with a corresponding one of said channels associated with any other one of said call switching means, a method of processing each call between first and second ones of said call switching means comprising in a first call processing mode, selecting a channel associated with said first call switching means that is marked idle and that has a corresponding channel associated with said second call switching means that is also marked idle, assigning for said call, marking as busy, and said switch means connecting, if not already connected, the selected channel associated with said first call switching means and the corresponding channel associated with said second call switching means, and marking again as idle the selected channel associated with said first call switching means and the corresponding channel associated with said second call switching means after the end of said each call, and in a second call processing mode, selecting a channel associated with said first call switching means that is marked idle and that is connected by said switch means to a corresponding channel associated with said second call switching means that is also marked idle, assigning for said call and marking as busy the selected channel associated with said first call switching means and the corresponding channel associated with said second call switching means, and marking again as idle the selected channel associated with said first call switching means and the corresponding channel associated with second call switching means after the end of said each call.

Claim 21

In an arrangement comprising a plurality of call switching means each for communicating in an associated plurality of channels and switch means for providing switched connections among said call switching means such that each of said channels associated with any given one of said call switching means is connectable with a corresponding one of said channels associated with any other one of said call switching means, a method of processing each call between first and second ones of said call switching means comprising in a first call processing mode, selecting a channel associated with said first call switching means that is marked idle and that has a corresponding channel associated with said second call switching means that is also marked idle, assigning for said call, marking as busy, and said switch means connecting, if not already connected, the selected channel associated with said first call switching means and the corresponding channel associated with said second call switching means, and marking again as idle the selected channel associated with said first call switching means and the corresponding channel associated with said second call switching means after the end of said each call, and in a second call processing mode, selecting a channel associated with said first call switching means that is marked idle and that is connected by said switch means to a corresponding channel associated with said second call switching means that is also marked idle, assigning for said call and marking as busy the selected channel associated with said first call switching means and the corresponding channel associated with said second call switching means, and marking again as idle the selected channel associated with said first call switching means and the corresponding channel associated with second call switching means after the end of said each call.

Claim 22

A method in accordance with claim 19 further comprising in said first call processing mode, said switch means removing the connection between the selected channel associated with said first call switching means and the corresponding channel associated with said second call switching means only as necessary to effect connection of selected channels by said switch means.

Claim 23

A method in accordance with claim 19 further comprising in said second call processing mode, retaining, for future calls between said first and second call switching means, the connection by said switch means of the selected channel associated with first call switching means and the corresponding channel associated with said second call.

Claim 24

An arrangement comprising a plurality of call switching means each for communicating during calls, means for providing paths among said plurality of call switching means, means for storing connection and availability status information for paths of said providing means, means for selecting, for each call between first and second ones of said call switching means, based on said stored connection and availability status information, an available path of said providing means between said first and second call switching means, and means for establishing said selected path through said providing means when the selected path is not already established, said selecting means being operative in a first call processing mode for selecting said available path without reference to whether said available path is presently established through said providing means, and said selecting means being operative in a second call processing mode for selecting said available path from only established paths of said providing means between said first and second call switching means.

Claim 25

An arrangement comprising a plurality of call switching means each for communicating during calls, means for providing paths among said plurality of call switching means, means for storing connection and availability status information for paths of said providing means, means for selecting, for each call between first and second ones of said call switching means, based on said stored connection and availability status information, an available path of said providing means between said first and second call switching means, and means for establishing said selected path through said providing means when the selected path is not already established, said selecting means being operative in a first call processing mode for selecting said available path without reference to whether said available path is presently established through said providing means, and said selecting means being operative in a second call processing mode for selecting said available path from only established paths of said providing means between said first and second call switching means.

Claim 26

An arrangement in accordance with claim 22 wherein each of of said plurality of call switching means comprises a different one of a plurality of distributed switch means of a switching system, and said providing means comprises a central switch means of said switching system, said central switch means for providing paths among said distributed switch means.

Claim 27

An arrangement in accordance with claim 22 wherein each of said plurality of call switching means comprises a different one of a plurality of distributed switch means of a switching system, and said providing means comprises a central switch means of said switching system, said central switch means for providing paths among said distributed switch means that are switchable on a per call basis, said providing means further comprising interconnect means for providing semi-permanent paths among said distributed switch means that are not switchable on a per call basis, said selecting means being operative in said first mode for selecting said available path from paths of said central switch means, and being operative in said second mode for selecting said available path from paths of said interconnect means.

Claim 28

An arrangement in accordance with claim 22 wherein each of said plurality of call switching means comprises a different one of a plurality of distributed switch means of a switching system, and said providing means comprises a central switch means of said switching system, said central switch means for providing paths among said distributed switch means that are switchable on a per call basis, said providing means further comprising interconnect means for providing semi-permanent paths among said distributed switch means that are not switchable on a per call basis, said selecting means being operative in said first mode for selecting said available path from paths of said central switch means and paths of said interconnect means, and being operative in said second mode for selecting said available path from paths of said interconnect means.