Communication apparatus and communication system

A communication system comprising:

• first and second upper-layer apparatuses first, second, third, and fourth lower-layer apparatus, each apparatus having line switching means,
• (i) wherein the first and second upper-layer apparatuses are connected to each other through first and second upper-layer communication lines between which communication can be switched,
• (ii) the first and second lower-layer apparatuses are connected to each other through first and second lower-layer communication lines between which communication can be switched, each lower-layer communication line being multiplexed to accommodate one or more upper-layer communication lines,
• (iii) the third and fourth lower-layer apparatuses are connected to each other through third and fourth lower-layer communication line between which communication can be switched, each lower-layer communication line being multiplexed to accommodate one or more upper-layer communication lines,
• (iv) the first upper-layer communication line connects the first upper-layer apparatus with the first lower-layer apparatus and the second upper-layer apparatus with the second lower-layer apparatus, and
• (v) the second upper-layer communication line connects the first upper-layer apparatus with the third lower-layer apparatus and the second upper-layer apparatus with the fourth lower-layer apparatus,
• wherein a switching-inhibit signal is transmitted to the upper-layer apparatuses when the lower-layer apparatuses have detected a line failure, on said lower and upper layer communication lines,
• one or more faulty lines of the lower or the upper layer are identified and the site of occurrence of failure is located by using failure information on the lower and upper-layer communication lines,
• the switching-inhibit signal to the upper-layer apparatuses is cancelled when no lower-layer communication line has been found faulty but as upper-layer communication line has been found faulty,
• whether line-switching means of the lower and upper-layer apparatuses should perform switching is determined, based on failure information on the lower and upper-layer communication lines, in order to secure a largest number of normal upper-layer communication lines, or in order to restore high-priority lines rather than low-priority lines, or in order to secure a largest number of signal channels, in case that any of the lower-layer communication lines has been found faulty;
• and
• first means for causing line switching in the lower layer first and then canceling the switching-inhibit signal to the upper-layer apparatuses, when switching is to take place in both the lower and upper layers in accordance with said determination.

A communication system comprising:

• a plurality of lower-layer apparatuses;
• a plurality of upper-layer apparatuses which belong to a layer which is upper than a layer to which the lower-layer apparatuses belong,
• wherein each apparatus has line-switching means,
• wherein connected between the lower-layer apparatuses are lower-layer communication lines, each lower-layer communication line being multiplexed to accommodate one or more upper-layer communication lines, and connected between the upper-layer apparatuses are upper-layer communication lines going through the lower-layer apparatuses,
• a switching-inhibit signal is transmitted to the upper-layer apparatuses when any of the lower-layer apparatuses has detected line failure, on said lower and upper layer communication lines,
• one or more faulty lines of the lower or the upper layer are identified and the site of occurrence of failure is located based on failure information on the lower and upper-layer communication lines,
• the switching-inhibit signal to the upper-layer apparatuses is cancelled when no lower-layer communication line has been found faulty but an upper-layer communication line has been found faulty,
• whether line-switching means of the lower and upper-layer apparatuses should perform switching is determined, based on failure information on the lower and upper-layer communication lines, in order to secure a largest number of normal upper-layer communication lines, or in order to restore high-priority lines rather than low-priority lines, or in order to secure a largest number of signal channels, any of the lower-layer communication lines has been found faulty;
• and
• first means for causing line switching in the lower layer first and then canceling the switching-inhibit signal to the upper-layer apparatuses, when switching is to take place in both the lower and upper layers in accordance with said determination.

A communication system comprising:

• first and second upper-layer apparatuses;
• first, second, third, and fourth lower-layer apparatuses,
• wherein each apparatus has line-switching means,
• (i) wherein the first and second upper-layer apparatuses are connected to each other through first and second upper-layer communication line between which communication can be switched,
• (ii) the first and second lower-layer apparatuses are connected to each other through first and second lower-layer communication lines between which communication can be switched, each lower-layer communication line being multiplexed to accommodate one or more upper-layer communication lines,
• (iii) the third and fourth lower-layer apparatuses are connected to each other through third and fourth lower-layer communication lines between which communication can be switched, each lower-layer communication line being multiplexed to accommodate one or more upper-layer communication lines,
• (iv) the first upper-layer communication line connects the first upper-layer apparatus with the first lower-layer apparatus and the second upper-layer apparatus with the second lower-layer apparatus, and
• (v) the second upper-layer communication line connects the first upper-layer apparatus with the third lower-layer apparatus and the second upper-layer apparatus with the fourth lower-layer apparatus,
• wherein a switching-inhibit signal is transmitted to the upper-layer apparatuses when the lower-layer apparatuses have detected a line failure, on said lower and upper layer communication lines,
• faulty lines of the lower and upper layers are identified and the site of occurrence of failure is located based on failure information on the lower- and upper-layer communication lines, and
• the switching-inhibit signal to the upper-layer apparatuses is cancelled when no lower-layer communication line has been found faulty but upper-layer communication line has been found faulty;
• and
• first means for determining, based on failure information on the lower and upper-layer communication lines, which line-switching means of the lower and upper-layer apparatuses should perform switching in order to secure a largest number of normal upper-layer communication lines, or in order to restore high-priority lines rather than low-priority lines, or in order to secure a largest number of signal channels, in case that any-of the lower-layer communication lines has been found faulty.

A communication system comprising:

• a plurality of lower-layer apparatuses;
• a plurality of upper-layer apparatuses which to a layer which is upper than a layer to which the lower-layer apparatus belong,
• wherein each apparatus has line switching means,
• wherein connected between the lower-layer apparatuses are lower-layer communication lines, each lower-layer communication line being multiplexed to accommodate one or more upper-layer communication lines, and connected between the upper-layer apparatuses are upper-layer communication lines going through the lower-layer apparatuses,
• a switching-inhibit signal is transmitted to the upper-layer apparatuses when any of the lower-layer apparatuses has detected a line failure, on said lower and upper layer communication lines,
• one or more faulty lines of the lower or the upper layer are identified and the site of occurrence of failure is located based on failure information on the lower and upper-layer communication lines, and
• the switching-inhibit signal to the upper-layer apparatuses is cancelled when no lower-layer communication line has been found faulty but any of the upper-layer communication lines has been found faulty;
• and
• first means for determining, based on failure information on the lower and upper-layer communication lines, which line-switching means of the lower- and upper-layer apparatuses should perform switching in order to secure a largest number of normal upper-layer communication lines, or in order to restore high-priority lines rather than low-priority lines, or in order to secure a largest number of signal channels, in case that any of the lower-layer communication lines has been found faulty.