Communication apparatus and communication system

Details Communication apparatus and communication system Communication apparatus and communication system

2000-06-06

2004-08-31

Yao, Kwang Bin (Department: 2667)

Multiplex communications

Fault recovery

Bypass an inoperative channel

C370S244000

Reexamination Certificate

active

06785225

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a communication apparatus and a communication system.
2. Description of the Related Art
Data communication has recently become more and more important with the spreading Internet, etc. as its background. ATM networks in accordance with ITU-T 1.150 have been introduced in this field to integrate telephony and data communication. High-speed optical communication network technologies such as SONET defined by ANSI T1.105, SDH defined by ITU-T G.707, and OTN defined by ITU-T G.872 have been introduced in this field. SONET and SDH have basically the same function, and OTN, an optical network, is based on the WDM (Wavelength Division Multiplexing) technology to raise the transmission capacity in a fiber.
These networks are interconnected by prescribing upper and lower layers based on the layer hierarchy of the OSI (Open System Interconnection) reference model defined by ISO. According to the provisions of these individual networks, ATM is ranked at the top; OTN, at the bottom; SONET and SDH, at the middle. Each network is also of hierarchic structure, consisting of subnetworks. For example, an ATM network consists of a virtual path and a virtual channel, and SONET/SDH and OTN are of hierarchic structures, consisting of subnetworks, as well.
SUMMARY OF THE INVENTION
Table 1 shows the relations between such upper and lower layers as relate to switching in the above subnetworks, segments defined by repeaters excluded.
FIG. 1
shows the relation between defined segments and multiplexing in a lower and an upper layer. Numerals
100
-
102
and
110
-
112
indicate apparatuses in the upper layer;
300
and
310
, apparatuses in the lower layer;
500
-
502
, communication lines in the upper layer;
600
, a communication line in the lower layer.
In
FIG. 1
, a plurality of upper-layer apparatuses is connected to a lower-layer apparatus. The upper-layer apparatuses
100
-
102
are connected to the lower-layer apparatus
300
through the upper-layer communication lines
500
-
502
. The upper-layer apparatuses
110
-
112
are connected to the lower-layer apparatus
310
through the upper-layer communication lines
500
-
502
. The lower-layer apparatuses bundle the upper-layer communication lines by TDM (Time Division Multiplexing) of SONET of ANSI T1.105 or SDH of ITU-T G.707 or by WDM of OTN of ITU-T G.872 so as to raise the data transmission capacity per physical medium or unit time and transmit data through the lower-layer communication line.
The upper-layer apparatuses
100
and
110
process the overhead portions of SONET or SDH signals when they transmit and receive the signals through the upper-layer communication line
500
, the overhead portions containing the administration control signals of the upper-layer communication line. The upper-layer apparatuses
101
and
111
, and
102
and
112
carry out the same processing for the upper-layer communication lines
501
and
502
, respectively. The segment for processing the administration control signals of the upper-layer communication line is called upper-layer communication-line segment (hereinafter “upper-layer segment”). The upper-layer communication lines
500
-
502
may be three physically separate lines or such a physically single line comprising three separate logical lines as the bus of SONET or SDH. In the same way, the lower-layer communication line
600
is terminated by the lower-layer apparatuses
300
and
310
, and the segment between the apparatuses is called the lower-layer communication-line segment (hereinafter “lower-layer segment”).
In this way, signals of the upper layer are multiplexed to become signals of the lower layers.
Accordingly, the signals of the upper layer may become equal to but never become larger than the signals of the lower layer in terms of the signal band. The defined segments of the upper layer may be equal to but never shorter than the defined segment of the lower layer.
FIG. 2
shows a case wherein each of the upper and lower layers has protection-switching processing parts. Upper-layer communication lines
500
to
505
are terminated by upper-layer apparatuses
100
-
104
and signal processing parts
120
-
124
and
125
-
129
in the apparatuses
100
-
104
. Multiplexing/demultiplexing parts
440
and
450
in lower-layer apparatuses
300
and
310
multiplex and demultiplex the upper-layer communication lines
500
-
503
, which, going through the lower-layer segment of the lower-layer communication line
600
or
601
, connect the upper-layer apparatuses
100
-
103
with those
110
-
113
. In the same way, multiplexing/demultiplexing units
441
and
451
in lower-layer apparatuses
301
and
311
multiplex and demultiplex the upper-layer communication lines
504
-
505
, which, going through the lower-layer segment of the lower-layer communication line
602
or
603
, connect the upper-layer apparatuses
103
and
104
with those
113
and
114
.
For the sake of simplification of description, a protection switching system of the 1+1 type will be taken as an example and its description will follow. The system comprises a set of a working communication line and a protection line. While the system is operating normally, the same data are transmitted through both the working and protection lines and the receiving side chooses a line of which the transmission quality is better than that of the other. In
FIG. 2
, a lower-layer communication-line bridge/selector part
420
or
430
on the transmitting side transmits the same data through both the working and protection lower-layer communication lines
600
and
601
. In the same way, a lower-layer communication-line bridge/selector part
421
or
431
on the transmitting side transmits the same data through both the working and protection lines
602
and
603
. While all the communication lines and all the apparatuses are normal, the lower-layer communication-line bridge/selector part
430
or
420
on the receiving side chooses the working line
600
. When the working line
600
goes out of service due to some failure, the lower-layer communication-line bridge/selector part
430
or
420
on the receiving side chooses the protection line
601
to restore the communication line in the lower layer. In the same way, while all the communication lines and all the apparatuses are normal, the lower-layer communication-line bridge/selector part
431
or
421
on the receiving side chooses the working line
602
. When the working line
602
goes out of service due to some failure, the lower-layer communication-line bridge/selector part
431
or
421
on the receiving side chooses the protection line
603
to restore the communication line in the lower layer.
As in the case of the lower-layer communication lines, an upper-layer communication-line bridge/selector part
220
or
230
on the transmission side transmits the same data through both the working and protection upper-layer communication lines
503
and
504
. While all the lines and all the apparatuses are normal, the upper-layer communication-line bridge/selector part
230
or
220
on the receiving side chooses the working line
503
. When the working line
503
goes out of service, the upper-layer communication-line bridge/selector part
230
or
220
on the receiving side chooses the protection line
504
to restore the communication line.
Describe below is the switching processing in the upper and lower layers upon the occurrence of failure in the lower-layer communication line
600
as shown in FIG.
3
. The switching method was devised to describe the embodiments of the present invention.
FIG. 3
shows a portion including the protection-switching processing parts of FIG.
2
. In this method, when failure has occurred in the lower layer, an alarm indication signal (AIS) is sent to the upper-layer apparatuses.
FIG. 4
shows the concept of AIS. As shown in
FIG. 4
, upper-layer communication lines
500
-
502
are terminated by upper-layer apparatuses
100
-
102
and
110
-
112
. Lower-layer apparatus

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