1. A switching device comprising: first wireless line terminating means for transmitting and receiving frames via a first wireless line; second wireless line terminating means for transmitting and receiving frames via a second wireless line; first line terminating means for exchanging frames with the first wireless line terminating means; second line terminating means for exchanging frames with the second wireless line terminating means; radio monitoring means for monitoring a state of the first and second wireless lines, the radio monitoring means instructing the first and second wireless line terminating means to exchange copy frames with other wireless line terminating means and to abandon the received frames, in accordance with a redundancy mode of the first and second wireless lines; communication path control means for setting the first and second line terminating means to each be an active system or a standby system in accordance with a monitoring result obtained by the radio monitoring means as to the state of the wireless lines; and a switch core that passes frames to be transmitted to the line terminating means operating as the active system, wherein the first and second wireless lines are subjected to a link aggregation so as to be treated as one virtual line.

2. The switching device according to Claim 1, wherein in setting a first redundancy mode in which the first line terminating means operates as the active system and the second line terminating means operates as the standby system, the switch core passes transmission frames to the first line terminating means, the radio monitoring means instructs the first wireless line terminating means to pass copy frames of the transmission frames received from the first line terminating means to the second wireless line terminating means, the radio - monitoring means instructing the second wireless line terminating means to abandon the received frames, and the second wireless line terminating means transmits the copy frames and abandons the received frame. 5

3. The switching device according to Claim 2, wherein when the radio monitoring means senses an abnormality in the first wireless line while operating in the first redundancy mode, the radio monitoring means instructs the second wireless line terminating means to stop abandoning the 10 received frames and to pass copy frames of the received frames to the first wireless line terminating means.

4. The switching device according to one of Claims 1 to 3, wherein in setting a second redundancy mode in which the first and second line 15 terminating means each operate as the active system, the switch core passes transmission frames substantially equally to the first line terminating means and the second wireless line terminating means.

5. The switching device according to Claim 4, wherein 20 when the wireless line terminating means senses an abnormality in the first or second wireless line while operating in the second redundancy mode, the wireless line terminating means notifies the communication path control means about the line with the abnormality, and the communication path control means sets the wireless line terminating 25 means connected to the line with the abnormality and the line terminating means exchanging frames with such wireless line terminating means to each be the standby system.

6. The switching device according to Claim 5, wherein 30 the line terminating means and the wireless line terminating means each changed to be the standby system by the communication path control means only perform, as an operation of the standby system, reception of frames.

7. The switching device according to Claim 1, wherein in stopping a function of the first wireless line terminating means while operating in a first redundancy mode in which the first line terminating means operates as the active system and the second line terminating means operates as the standby system, the radio monitoring means notifies the communication path control means about an abnormality in the first wireless line attributed to the first wireless line terminating means being stopped, the radio monitoring means instructing the second wireless line terminating means to transmit frames passed from the second line terminating means, and in accordance with the notification, the communication path control means sets the first line terminating means to be the standby system and sets the second line terminating means to be the active system.

8. The switching device according to any one of Claims 1 to 7, wherein the wireless line terminating means is structured by a card-shaped removable device.

9. The switching device according to any one of Claims 1 to 8, wherein the switching device is a layer 2 switch. 10, A method for controlling frame transmission and reception, wherein a switching device includes first wireless line terminating means for transmitting and receiving frames via a first wireless line, second wireless line terminating means for transmitting and receiving frames via a second wireless line, first line terminating means for exchanging frames with the first wireless line terminating means, and second line terminating means exchanging frames with the second wireless line terminating means, the switching device performs a link aggregation with which the first and second wireless lines are treated as one virtual line, the switching device monitoring a state of the first and second wireless lines and instructing the first and second wireless line terminating means, in accordance with a redundancy mode of the first and second wireless lines, to exchange copy frames with other wireless line terminating means and to abandon received frames, the switching device sets, in accordance with a monitoring result of the wireless lines, the first and second line terminating means to each be an active fi 3 4 r l j 7 * - w~L a % -. (&,; --rd 26 system or a standby system, and the switching device passes frames to be transmitted to the line terminating means operating as the active system. n 5 Dated this 2oth day of December 2013 Agent for the Applicant

DESCRIPTION
SWITCHING DEVICE AND METHOD FOR CONTROLLING FRAME
TRANSMISSION AND RECEPTION
Technical Field
[OOOl]
The present invention relates to a switching device and a method for
controlling frame transmission and reception.
Background Art
[0002]
With a wireless device including a layer 2 switch, the wireless section may
be configured to be redundant. Redundancy with the wireless device including
the layer 2 switch is generally made by IEEE 802.3ad (a link aggregation). Such
a redundant configuration is made in order to achieve load distribution (load
balancing) or to improve fault tolerance.
[0003]
With such a wireless device, switchover of a wireless port (a card-shaped
device that carries out wireless communication) may take place in order to address
an occurrence of a fault in the wireless port, replacement of the wireless port, a
change in the wireless environment and the like. With the wireless device, when
switchover of the wireless port takes place with the wireless section being
configured to be redundant, a flush process (a clear process) of an FDB (Forward
DataBase) learned by the layer 2 switch occurs. This flush process of the FDB
causes flooding of frames. That is, unnecessary frame transfer is performed to
disadvantageously increase the traffic. Further, missing (losses) of frames will
be invited until communication is started with the wireless port newly switched to.
[0004]
When the link aggregation is realized with the wireless device including
the layer 2 switch, a wireless line termination unit (a card-shaped device that
carries out wireless communication) that communicates via a wireless line exerts
buffer control such as a transmission allocation and a transmission duplexing
process. Further, the wireless line termination unit performs the ACT (active
system) / SBY (standby system) management by software. For realizing these
functions, it takes time for the wireless line termination unit to carry out the
switchover process of the wireless port.
[0005]
In the following, a description will be given of the technique relating to the
aforementioned problem.
[0006]
Patent Literature 1 discloses a data transfer method according to which all
the main lines in a redundancy configuration can be switched. Patent Literature 1
discloses a redundant configuration in which a virtual path is generated by a
plurality of main lines and one or more protection lines. Using the virtual path,
transmission and reception of frames are performed.
[0007]
Patent Literature 2 discloses a transfer system in which a link aggregation
scheme is applied to a plurality of lines. With this system, a special frame
referred to as the MRL (Multi-Radio-Linc) frame is used for realizing the link
aggregation.
[0008]
Patent Literature 3 discloses a technique for performing the line switching
between two lines while maintaining the traffic using layer 2 switches. Note that
Patent Literature 3 is silent about the configuration in which redundancy is made
in order to achieve the load distribution in the wireless section (an N+O
configuration).
Citation List
Patent Literatures
[0009]
Patent Literature 1 : Japanese Unexamined Patent Application Publication
NO. 2008-54058
Patent Literature 2: Japanese Unexamined Patent Application Publication
NO. 201 0-258606
Patent Literature 3: Japanese Unexamined Patent Application Publication
NO. 2011-4124
Summary of Invention
Technical Problem
[OO lo]
With the techniques disclosed in Patent Literatures 1 and 2, since special
frames are used for realizing the link aggregation, an increase in frames being
transmitted and received on the network is invited, whereby the band in use
increases. Further, Patent Literature 3 does not suggest or teach the case where
switchover of the wireless port or a failure of the wireless port takes place in a
so-called N+O configuration.
[OOll]
As described above, switchover of the wireless port takes place in order to
address a failure of the wireless port, replacement of the wireless port, a change in
the wireless environment and the like. As described above, switchover of the
wireless port puts a great load on the wireless line termination unit, and requires
time for processing. Further, the techniques of Patent Literatures 1 to 3 still do
not fully cope with an increase in the band in use nor do they fully achieve the load
distribution. That is, there exists a problem that efficient and full port switchover
cannot be realized.
[OO 121
The present invention has been made in consideration of the problem noted
above, and the main object thereof is to provide a switching device and a method
for controlling a communication device with which efficient and full port
switchover can be realized.
Solution to Problem
[00 131
An aspect of a switching device according to the present invention is a
switching device comprising: first wireless line terminating means for transmitting
and receiving frames via a first wireless line; second wireless line terminating
means for transmitting and receiving frames via a second wireless line; first line
terminating means for exchanging frames with the first wireless line terminating
means; second line terminating means for exchanging frames with the second
wireless line terminating means; radio monitoring means for monitoring a state of
the first and second wireless lines, the radio monitoring means instructing the first
and second wireless line terminating means to exchange copy frames with other
wireless line terminating means and to abandon the received frames, in accordance
with a redundancy mode of the first and second wireless lines; communication path
control means for setting the first and second line terminating means to each be an
active system or a standby system in accordance with a monitoring result obtained
by the radio monitoring means as to the state of the wireless lines; and a switch
core that passes frames to be transmitted to the line terminating means operating as
the active system, wherein the first and second wireless lines are subjected to a
link aggregation so as to be treated as one virtual line.
[00 141
An aspect of a method for controlling frame transmission and reception
according to the present invention is wherein a switching device includes first
wireless line terminating means for transmitting and receiving frames via a first
wireless line, second wireless line terminating means for transmitting and
receiving frames via a second wireless line, first line terminating means for
exchanging frames with the first wireless line terminating means, and second line
terminating means exchanging frames with the second wireless line terminating
means, the switching device performs a link aggregation with which the first and
second wireless lines are treated as one virtual line, the switching device
monitoring a state of the first and second wireless lines and instructing the first
and second wireless line terminating means, in accordance with a redundancy
mode of the first and second wireless lines, to exchange copy frames with other
wireless line terminating means and to abandon received frames, the switching
device sets, in accordance with a monitoring result of the wireless lines, the first
and second line terminating means to each be an active system or a standby system,
and the switching device passes frames to be transmitted to the line terminating
means operating as the active system.
Advantageous Effects of Invention
[00 151
The present invention can provide a switching device and a method for
controlling a communication device with which efficient and full port switchover
can be realized.
Brief Description of Drawings
6
[00 161
Fig. 1 is a block diagram showing the configuration of a system including a
switching device according to a first embodiment;
Fig. 2 shows the operations of the system according to the first embodiment
(when a 1+1 mode is set);
Fig. 3 shows the operations of the system according to the first embodiment
(when the 1+1 mode is set);
Fig. 4 shows the operations of the system according to the first embodiment
(when a 2+0 mode is set);
Fig. 5 shows the operations of the system according to the first embodiment
(when the 2+0 mode is set);
Fig. 6 shows the operations of the system according to the first embodiment
(when a wireless line termination unit is replaced);
Fig. 7 shows the operations of the system according to the first embodiment
(when the band of the wireless line changes);
Fig. 8 is a flowchart showing the operations of the radio monitoring unit
according to the first embodiment;
Fig. 9 is a flowchart showing the operations of a communication path
control unitaccording to the first embodiment;
Fig. 10 is a flowchart showing the operations of the communication path
control unit according to the first embodiment;
Fig. 11 shows the operations of the system according to the first
embodiment (when the band is optimized in the 2+0 configuration); and
Fig. 12 is a flowchart showing the operations of a layer 2 switch according
to the first embodiment.
Description of Embodiments
[OO 1 7]
In the following, with reference to the drawings, a description will be given
of an embodiment of the present invention. Fig. 1 is a block diagram showing the
configuration of a communication system according to the present embodiment.
The system includes a device 1, a layer 2 switch 2, a layer 2 switch 3, and a device
4. The layer 2 switch 2 and the layer 2 switch 3 are connected to each other via a
line 51 and a line 52. The line 51 and the line 52 are wireless lines. The device
1 and the layer 2 switch 2 are connected to each other via a line 53. The device 4
and the layer 2 switch 3 are connected to each other via a line 54. Note that, as
shown in the drawing, the layer 2 switch 2 and the layer 2 switch 3 may be
connected to each other via a line 55 being a wired line. The device 1 and the
device 4 are each a device that transmits and receives frames.
[OO 1 81
The layer 2 switch 2 includes a wireless line termination unit 21, a wireless
line termination unit 22, a line termination unit 23, a line termination unit 24, a
line termination unit 25, a line termination unit 26, and a switch unit 27. The
switch unit 27 includes a switch core 271, a radio monitoring unit 272, and a
communication path control unit 273.
[00 191
The wireless line
termination unit 21 and the wireless line termination unit 22 are each a processing
unit that transmits and receives frames via the wireless line. The line termination
unit 23 and the line termination unit 24 are each a processing unit that transmits
and receives frames to and from any element connected via the wire. The
wireless line termination unit 21 and the wireless line termination unit 22 are each
a card-shaped device in general. The line termination unit 25 and the line
termination unit 26 are each a processing unit that exchange frames with the
wireless line termination unit 21 and the wireless line termination unit 22,
respectively.
[0020]
In the following, a description will be given of the switch unit 27. The
switch core 271 is a processing unit that includes therein an FDB (Forward
DataBase, not shown) and that controls frame transmission. The switch core 271
passes transmission frames to a line termination unit set to be an active system.
[002 11
The radio monitoring unit 272 has the following functions. Note that,
each of the functions will be described in detail later with reference to Figs. 2 to
12.
(1) To determine whether or not a wireless line is made redundant; when it
is, detect the mode thereof.
(2) To monitor the state of a wireless line section.
(3) To instruct the wireless line termination unit 21 or 22 to copy
transmission frames.
(4) To instruct the wireless line termination unit 21 or 22 to select the
received frames.
(5) To detect that the received frames are abandoned.
(6) To calculate the wireless line section band.
(7) To provide a variety of notification to the communication path control
unit 273.
[0022]
Note that, (6) Calculation of the wireless line section band by the radio
monitoring unit 272 is performed by subtracting the band used by the STM
(Synchronous Transfer Mode) and the like from the total radio band. (6)
Calculation of the wireless line section band is performed upon a change in the
radio band caused by the AMR (Adaptive Modulation Radio), for example.
[0023]
The communication path control unit 273 has the following functions.
Note that, each of the functions will be described in detail later with reference to
Figs. 2 to 12.
(1) To receive notification from the radio monitoring unit 272.
(2) To control the operation of the active system (ACT) and the standby
system (SBY) for the line termination units and the wireless line termination units
for each redundant configuration mode (a control link aggregation).
[0024]
Note that, since the layer 2 switch 3 is structured substantially identically
to the layer 2 switch 2 and its constituents perform similar operations, the detailed
description is not repeated.
COO251
Subsequently, with reference to Fig. 2, a description will be given of the
operation of the system in an N+l mode (N being a natural number of 1 or more) as
a redundant configuration mode. In the following description, the N+l mode is
the mode in which at least one communication path (one of the line 51 and the line
52 in Fig. 1) operates as the standby system. The description will be given based
on the assumption that N = 1.
[0026]
Fig. 2 shows the operation of the system operating in the 1+1 mode (in
which the line 51 is the main line and the line 52 is the protection line). The
wireless line termination unit 21, the line termination unit 25, the wireless line
termination unit 31, and the line termination unit 35 perform operations that are
suitable for the active system (ACT). The wireless line termination unit 22, the
line termination unit 26, the wireless line termination unit 32, and the line
termination unit 36 perform operations that are suitable for the standby system
(SBY). The line 51 and the line 52 are subjected to the link aggregation (i.e.,
treated as one virtual line). Note that, any known scheme should be employed to
achieve a variety of setting for the link aggregation.
[0027]
Here, the 1+1 mode is the mode in which identical frames are exchanged
via the line 51 and the line 52, and when normally performed, the frames
exchanged via the line 52 are abandoned.
[0028]
When it is determined to operate in the operation in the 1+1 mode (when
the mode is set), the line termination units and the wireless line termination units
start performing operations corresponding to the 1+1 mode. The radio monitoring
unit 272 detects that the wireless lines are made redundant, and that the
redundancy is made in the 1+1 mode. Then, the radio monitoring unit 272
notifies the detection result to the communication path control unit 273.
[0029]
The radio monitoring unit 272 calculates the wireless section band, and
notifies the calculation result to the communication path control unit 273. The
radio monitoring unit 272 instructs the wireless line termination unit 21 operating
as the active system (ACT) to copy the frames to be transmitted. Further, the
radio monitoring unit 272 instructs the wireless line termination unit 22 operating
as the standby system (SBY) to abandon the received frames.
[003 01
The communication path control unit 273 sets an LAG (link aggregation) to
the line termination units 25 and 26 in response to the setting of redundancy in the
1+1 mode. Specifically, the communication path control unit 273 sets the line
termination unit 25 to be the active system (ACT), and sets the line termination
unit 26 to be the standby system (SBY).
10
[003 11
Note that the operations described above are performed also as to the layer
2 switch 3.
[0032]
Next, a description will be given of the operations when frames are
transmitted from the device 1 to the device 4. Note that, in the following
description, it is understood that an appropriate value is previously set in the FDB
in the switch core 271. Since the destination of frames output from the device 1
is the device 4, the switch core 271 refers to the FDB and transmits the frames in
the direction of the line 51 (that is, to the line termination unit 25 operating as the
active system). Since the line termination unit 25 operates as the active system
(ACT), the line termination unit 25 transmits the received frames to the wireless
line termination unit 2 1.
[0033]
The wireless line termination unit 21 operates as the active system (ACT).
The wireless line termination unit 21 copies the received frames, and transmits the
copied frames to the wireless line termination unit 22. Further, the wireless line
termination unit 21 transmits transmission frames to the wireless line termination
unit 3 1 via the line 5 1. The wireless line termination unit 22 transmits the frames
received from the wireless line termination unit 21 to the wireless line termination
unit 32 via the line 52. Thus, the identical frames are transmitted to the line 51
and the line 52.
[0034]
The wireless line termination units 31 and 32 receive the frames. Here,
the radio monitoring unit 372 instructs the wireless line termination unit 32
operating as the standby system (SBY) to abandon the frames. In response
thereto, the wireless line termination unit 32 abandons the received frames. The
wireless line termination unit 31 transmits the received frames to the line
termination unit 35. The frames arrive at the device 4 via the switch core 371.
[003 51
Note that, in the foregoing, the description has been given of the case
where the device 1 transmits frames to the device 4. However, substantially
identical operations are performed also in the case where the device 4 transmits
frames to the device 1.
Next, with reference to Fig. 3, a description will be given of the operations
of the system in the case where the line 51 encounters any defective conditions in
the configuration shown in Fig. 2 (the 1 (N) +1 mode). As described above, the
5 radio monitoring unit 272 monitors the status of the line 51 and the line 52. The
radio monitoring unit 272 notifies the communication path control unit 273 about
an occurrence of an abnormality in the line 51. Since the system is operating in
the 1+1 mode, the communication path control unit 273 allows the operations to
continue with the line termination unit 25 being kept operating as the active system
10 (ACT) and the line termination unit 26 being kept operating as the standby system
(SBY) (i.e., no setting change is performed).
[0037]
Thus, the wireless line termination unit 21 copies the frames and transmits
the copy to the wireless line termination unit 22. The wireless line termination
15 unit 22 transmits the frames received from the wireless line termination unit 21 to
the wireless line termination unit 32 via the line 52.
[003 81
Here, the link aggregation (i.e., the line 51 and the line 52 being treated as
one virtual line) is set to the line termination units 25 and 26. Further, the frames
20 output from the line termination unit 25 are copied and transmitted from the
wireless line termination unit 22. Accordingly, even when a failure occurs in the
line 51, the frames are treated as being normally transmitted. Therefore, no
necessity of changing the setting of the FDB in the switch core 271 arises, and the
FDB flush (clearing the FDB) is not executed.
I 25 [0039]
Subsequently, a description will be given of frame transmission from the
device 1 to the device 4 upon an abnormality in the line 51. As has been
described with reference to Fig. 2, the wireless line termination units 21 and 22
transmit frames via the lines 51 and 52. However, since the line 5 1 is suffering
30 from an abnormality, only the frames via the line 52 are normally transmitted.
Here, since no failure is occurring in the line 52 and the link aggregation has been
performed, there is no abnormality in the frame transmission from the layer 2
switch 2 to the layer 2 switch 3. Since there is no abnormality, the setting of the
FDB in the switch core 271 is not changed (i.e., no FDB flush occurs).
Next, a description will be given of the operations of the layer 2 switch 3
on the reception side. The radio monitoring unit 372 senses that an abnormality
is occurring in the line 51. The radio monitoring unit 372 instructs the wireless
5 line termination unit 32 to transmit the received frames to the wireless line
termination unit 3 1. The wireless line termination unit 32 transmits frames being
the copy of the received frames to the wireless line termination unit 31. The
wireless line termination unit 31 transmits the frames received from the wireless
line termination unit 32 to the line termination unit 35. The frames arrive at the
10 device 4 via the switch core 371. Here, since no failure is occurring in the line 52
and the link aggregation has been performed, the radio monitoring unit 372
determines that there is no abnormality in frame transmission from the layer 2
switch 2 to the layer 2 switch 3. Since there is no abnormality, the setting of the
FDB in the switch core 371 is not changed (i.e., no FDB flush occurs).
15 [0041]
Note that, though the description above has been given of the case where
the device 1 transmits frames to the device 4, substantially identical operations are
performed also in the case where the device 4 transmits frames to the device 1.
[0042]
20 Subsequently, with reference to Fig. 4, a description will be given of the
operations of the system in the N+O mode (N being a natural number of 2 or more)
as the redundant configuration mode. In the following description, the N+O mode
is the mode in which two (or more) communication paths (the line 51 and the line
52 in Fig. 4) both operate as the main lines. In the following, the description will
25 be given based on the assumption that N = 2.
[0043]
In the 2+0 mode, the frames passing through the line 51 and the frames
passing through the line 52 do not overlap, and only different frames are
exchanged. That is, the 2+0 mode is the mode that realizes distribution of the
30 line load, i.e., the load balance. The line 51 and the line 52 are subjected to the
link aggregation (i.e., treated as one virtual line).
[0044]
Fig. 4 shows the operation of the system in the 2+0 mode (in which the line
51 and the line 52 are the main lines).
13
[0045]
When it is determined to operate in the 2+0 mode (when the mode is set),
the line termination units and the wireless line termination units start performing
operations corresponding to the 2+0 mode. The radio monitoring unit 272 detects
that the wireless lines are made redundant, and that the redundancy is made in the
2+0 mode. Then, the radio monitoring unit 272 notifies the detection result to the
communication path control unit 273.
[0046]
The radio monitoring unit 272 calculates the wireless section band, and
notifies the calculation result to the communication path control unit 273. The
communication path control unit 273 sets the LAG (link aggregation) to the line
termination units 25 and 26 in response to setting of redundancy in the 2+0 mode.
Specifically, the communication path control unit 273 sets the line termination unit
25 and the line termination unit 26 to each be the active system (ACT). By
providing the line termination units being two active systems, frames are
transmitted and received as being distributed between the line 51 and the line 52.
[0047]
Note that the operation described above is performed also as to the layer 2
switch 3.
[0048]
Next, a description will be given of the operations when frames are
transmitted from the device 1 to the device 4. Note that, in the following
description, it is understood that an appropriate value is previously set in the FDB
in the switch core 27 1.
[0049]
The switch core 271 receives frames transmitted from the device 1. Since
the destination of the received frames is the device 4, the switch core 271 transmits
the frames to one of the line termination unit 25 and the line termination unit 26,
such that the frames are transmitted to the layer 2 switch 3. Here, since the line
load is distributed, the switch core 271 allocates the frames to the line termination
unit 25 and the line termination unit 26 substantially evenly. The line termination
unit 25 transmits the frames to the wireless line termination unit 21. Similarly,
the line termination unit 26 transmits the frames to the wireless line termination
unit 22. The wireless line termination unit 21 transmits the received frames to
the wireless line termination unit 31. The wireless line termination unit 22
transmits the received frames to the wireless line termination unit 32.
[0050]
The wireless line termination unit 31 and the wireless line termination unit
32 respectively receive the frames. The wireless line termination unit 31
transmits the received frames to the line termination unit 35. Similarly, the
wireless line termination unit 32 transmits the received frames to the line
termination unit 36. The line termination unit 35 and the line termination unit 36
transmit the received frames to the switch core 371.
[005 11
Since the line termination unit 35 and the line termination unit 36 have
been subjected to the link aggregation, the switch core 371 treats the frames as
being supplied from one line. The switch core 371 transmits the frames being
input from the line termination unit 35 and the line termination unit 36 to the
device 4.
[0052]
Note that, though the description above has been given of the case where
the device 1 transmits frames to the device 4, substantially identical operations are
performed also in the case where the device 4 transmits frames to the device 1.
[0053]
Next, with reference to Fig. 5, a description will be given of the operations
of the system in the case where the line 51 encounters any defective conditions in
the configuration shown in Fig. 4 (the 2 (N) +O mode). As described above, the
radio monitoring unit 272 monitors the status of the line 51 and the line 52. The
radio monitoring unit 272 notifies the communication path control unit 273 about
an occurrence of an abnormality in the line 5 1. Since the system is operating in
the 2+0 mode and an abnormality is occurring in the line 51, the communication
path control unit 273 changes the line termination unit 25 to be the standby system
(SBY). Here, the line 51 and the line 52 are treated as one virtual line (i.e.,
subjected to the link aggregation). Therefore, it is treated as no abnormality
occurring as the entire line, and hence no FDB flush occurs.
[0054]
Subsequently, a description will be given of frame transmission from the
device 1 to the device 4 when an abnormality is occurring in the line 51. As
15
described above, under the control of the communication path control unit 273, the
line termination unit 25 serves as the standby system (SBY). Accordingly, the
switch core 271 transmits frames to the line termination unit 26 operating as the
active system (ACT). The line termination unit 26 successively transmits the
frames to the line termination unit 36. Here, since the line 51 and the line 52 are
treated as one virtual line by the link aggregation, it is not treated as an
abnormality occurring in this line. Accordingly, in the switch core 271, no FDB
flush occurs.
[OOS 51
Next, a description will be given of the operation of the layer 2 switch 3 on
the reception side. The wireless line termination unit 32 receives frames via the
line 52. Note that, similarly to the layer 2 switch 2, the line termination unit 35
is changed to be the standby system (SBY) addressing the abnormality in the line
51. The wireless line termination unit 32 transmits the received frames to the line
termination unit 36. The line termination unit 36 supplies the received frames to
the switch core 371. The switch core 371 transmits the supplied frames to the
device 4. At this time, since the line 51 and the line 52 are treated as one virtual
line by the link aggregation, it is not treated as an abnormality occurring in this
line. Accordingly, no FDB flush occurs in the switch core 371 also.
[0056]
Note that, though the description above has been given of the case where
the device 1 transmits frames to the device 4, substantially identical operations are
performed also in the case where the device 4 transmits frames to the device 1.
[0057]
Note that, the line termination unit and the wireless line termination unit
that each serve as the standby system (SBY) upon the occurrence of an abnormality
in the 2+0 mode are set to the transmission-enabledlreception-disabled
(standby-admit) state. Thus, even in the case where an abnormality is highly
possibly occurring in a line, the frames normally received via that line can be
provided to the destination device as they are, and hence losses of frames are
reduced.
COO5 81
Subsequently, with reference to Fig. 6, a description will be given of the
operation of the system when the wireless line termination unit is replaced. Fig.
16
6 shows the operation of the system when the work of replacing the wireless line
termination unit 21 is performed in the 1+1 mode redundancy configuration. In
the initial state, the wireless line termination unit 21 and the line termination unit
25 each operate as the active system (ACT), and the wireless line termination unit
22 and the line termination unit 26 each operate as the standby system (SBY).
[0059]
As described above, the wireless line termination unit 21 is a card-shaped
device in general. When the wireless line termination unit 21 is removed from
the-layer 2 switch 2, the radio monitoring unit 272 detects the removal of the
wireless line termination unit 21, i.e., the abnormal state. When the radio
monitoring unit 272 detects the removal, the radio monitoring unit 272 instructs
the wireless line termination unit 22 operating as the standby system (SBY) to
operate as the active system (ACT). Further, the radio monitoring unit 272
notifies the communication path control unit 273 about the abnormal state of the
wireless line termination unit 21 (i.e., the card removal).
[0060]
The communication path control unit 273 having received the notification
changes the operations of the line termination unit 25 and the line termination unit
26. Specifically, the communication path control unit 273 changes the setting of
the line termination unit 25 from the active system (ACT) to the standby system
(SBY), and changes the setting of the line termination unit 26 from the standby
system (SBY) to the active system (ACT).
[0061]
Here, since the line 51 and the line 52 are subjected to the link aggregation
and the line 52 is usable, it is treated as no abnormality occurring as the entire
virtual line. Accordingly, the FDB flush in the switch core 271 is not performed.
Note that, in the opposite layer 2 switch 3, the abnormality in the line 51 is
detected by the radio monitoring unit 372. The operation in this case is similar to
that having been described with reference to Fig. 3.
[0062]
Subsequently, a description will be given of frame transmission from the
device 1 to the device 4 when a replacing work of the wireless line termination unit
21 takes place. The switch core 271 receives frames whose destination is the
device 4 from the device 1. The switch core 271 transmits the received frames to
17
the line termination unit 26 set to be the active system (ACT). The line
termination unit 26 transmits the frames to the layer 2 switch 3 via the wireless
line termination unit 22 via the line 52. The operation of the layer 2 switch 3
becomes similar to that having been described with reference to Fig. 3.
[0063]
Subsequently, a description will be given of frame transmission from the
device 4 to the device 1 when a replacing work of the wireless line termination unit
21 takes place. The switch core 371 receives frames whose destination is the
device 1 from the device 4. The switch core 371 transmits the received frames to
the line termination unit 35 set to be the active system (ACT). The line
termination unit 35 transmits the received frames to the wireless line termination
unit 3 1. The wireless line termination unit 31 transmits frames being the copy of
the received frames to the wireless line termination unit 32. The wireless line
termination unit 32 transmits the copy frames to the wireless line termination unit
32. The wireless line termination unit 22 passes the received frames to the switch
core 271 via the line termination unit 26. The switch core 271 transmits the
frames to its destination, i.e., the device 1.
[0064]
Since the line 51 and the line 52 are subjected to the link aggregation and
the line 52 is usable, it is treated as no abnormality occurring as the entire virtual
line. Accordingly, the FDB flush in the switch core 271 and the switch core 371
is not performed.
[0065]
As has been described above, no FDB flush is performed upon a failure in
any wireless line section and upon replacement of any wireless line termination
unit when the wireless line is made redundant (1 (N) +1 mode, 2 (N) +O mode).
By the FDB flush not being performed, frame flooding is not invited. That is, it
becomes possible to suppress an increase in the traffic.
[0 0 6 61
Next, with reference to Figs. 7 to 10, a description will be given of the
operations of the system when the radio band has changed. Fig. 7 is a block
diagram showing the operations of the layer 2 switch 2 when the radio band has
changed while the wireless line section is made redundant in the 1+1 mode.
[0067]
18
Firstly, with reference to Figs. 7 and 8, a description will be given of the
operations of the radio monitoring unit 272. Fig. 8 is a flowchart showing the
operations of the radio monitoring unit 272 when the radio band has changed.
Firstly, the radio monitoring unit 272 detects a change in the band of wireless lines
in use (Sl). When a change in the band of a certain wireless line is detected (Sl),
the radio monitoring unit 272 calculates the band that can be used by the line, and
examines whether or not there is no band that can be assigned (S2). When there
is no band that can be assigned, that is, when the band of a certain wireless line is
0 (S2: Yes), the radio monitoring unit 272 notifies the communication path control
unit 273 about the same (S3).
[0068]
Next, with reference to Figs. 7 and 9, a description will be given of the
operations of the communication path control unit 273 notified that the band is 0
by the radio monitoring unit 272. Fig. 9 is a flowchart showing the operations of
the communication path control unit 273 notified that the band is 0 by the radio
monitoring unit 272.
[0069]
The communication path control unit 273 checks whether or not the band of
the notified wireless line is 0 (S4). The communication path control unit 273
determines whether or not the switchover of active system (ACT)/standby system
(SBY) is required, based on the state of the band and the usage state of the current
active system (ACT)/standby system (SBY) (S5). For example, when the band
becoming 0 has been used as the active system (ACT), the communication path
control unit 273 determines that a switchover of the active system (ACT)/standby
system (SBY) is required (S5: Yes).
[0070]
When the switchover of the active system (ACT)/standby system (SBY) is
required (S5: Yes), the communication path control unit 273 changes the setting
(S6). For example, when the wireless line termination unit 21 and the line
termination unit 25 are each used as the active system (ACT), the communication
path control unit 273 changes the setting such that the wireless line termination
unit 21 and the line termination unit 25 each become the standby system (SBY),
and that the wireless line termination unit 22 and the line termination unit 26 each
become the active system (ACT).
19
[0071]
Next, with reference to Fig. 10, a description will be given of the detailed
operations of the communication path control unit 273 (i.e., the detail of the
aforementioned S4 to S6). Fig. 10 is a flowchart showing the detail of the
operations of the communication path control unit 273 when the band has changed.
COO721
The communication path control unit 273 receives a notification as to the
radio band from the radio monitoring unit 272 (S11). The communication path
control unit 273 checks whether or not the wireless redundancy mode is 1 (N)+1
(S 12).
[0073]
When the wireless redundancy mode is 1+1 (S12: Yes), the communication
path control unit 273 determines whether or not the wireless line termination unit
and the line termination unit are each operating as the active system (ACT)
connected to the line whose band has become 0 (S13).
COO741
When the wireless line termination unit and the line termination unit
connected to the line whose band has become 0 are each operating as the active
system (ACT) (S13: Yes), and the wireless line termination unit and the line
termination unit each being the standby system (SBY) are capable of normally
operating (S14: Yes), the communication path control unit 273 changes the setting
(S15). Specifically, the communication path control unit 273 sets the wireless
line termination unit and the line termination unit each having been operating as
the active system (ACT) to each be the standby system (SBY), and sets the
wireless line termination unit and the line termination unit each having been
operating as the standby system (SBY) to each be the active system (ACT).
[0075]
When the wireless redundancy mode is 2+0 (S12: No), the communication
path control unit 273 sets the wireless line termination unit and the line
termination unit connected to the line whose band has become 0 to each be the
standby system (SBY) (S 16).
[0076]
As has been described with reference to Figs. 7 to 10, even when the band
state in the wireless lines has changed, the change can be detected to quickly
20
change the setting. Thus, the frame losses can be minimized.
[0077]
Subsequently, a description will be given of resetting of the line
termination units and the wireless line termination units when the N+O redundancy
mode is set. Fig. 11 is a block diagram showing the resetting. Fig. 12 is a
flowchart showing the operation of the resetting of the layer 2 switch 2.
[0078]
The layer 2 switch 2 newly includes a communication rate monitoring unit
274 in the switch unit 27. The communication rate monitoring unit 274 is a
processing unit detecting the transmission rate of each of the line termination units
in the wireless section. The communication rate monitoring unit 274 notifies the
detected transmission rate of each of the line termination units to the
communication path control unit 274.
[0079]
Subsequently, a description will be given of the operation with reference to
Fig. 12. Firstly, the radio monitoring unit 272 monitors a change in the band of
each line in the wireless section. Then, at a prescribed timing (e.g., when the
AMR (Adaptive Modulation Radio) is set), the radio monitoring unit 272 notifies a
change in the state of the band of a certain line to the communication path control
unit 273 (S21).
[0080]
When the band of the line being notified to the communication path control
unit 273 has been reduced from the previous band (S22: Yes), the communication
path control unit 273 recognizes other lines in operation (S23), and performs the
shaping setting (S24), i.e., changes the band setting such that the frame allocation
becomes optimum.
[008 11
Next, the communication rate monitoring unit 274 acquires the
transmission rate of the line termination units (25 and 26), and checks whether or
not the setting value of the band changed in S24 is exceeded (S25). Thereafter,
the communication path control unit 273 again sets the band such that allocation of
frames is optimized (S26).
[0082]
On the other hand, when the band of the line being notified to the
.
2 1
communication path control unit 273 has been reduced from the previous band
(S22: No), the communication path control unit 273 waits to be notified about any
change in the band of other line, and thereafter performs the shaping setting (S26),
i.e., changes the setting of the band of each line such that the frame allocation is
5 optimized.
[0083]
Subsequently, a description will be given of the effect of the present
invention. As has been described above, since no FDB flush occurs with the layer
2 switch (switching device) according to the present embodiment upon any failure
10 of any wireless line or in replacing any wireless line termination unit, the frame
flooding will not occur. That is, it becomes possible to prevent unnecessary
transmission of frames.
[0084]
Further, as has been described with reference to Figs. 7 to 10, even when
15 the state of the band of any wireless line has changed, the layer 2 switch
(switching device) according to the present embodiment can detect the change and
can quickly change the setting. Thus, losses of frames can be minimized.
[0085]
Still further, as has been described with reference to Figs. 11 and 12, the
20 layer 2 switch (switching device) according to the present embodiment can
effectively use the radio band when the N+O redundancy mode is set.
[0086]
Note that the present invention is not limited to the embodiment described
above, and can be modified as appropriate within a range not departing from the
25 gist of the present invention. While the foregoing description has been given of
the layer 2 switch, the present invention is not necessarily limited thereto. The
frame transmission-reception scheme is applicable to a bridge device, a layer 3
switch, a router device, a gateway device, an optical relay device and the like.
[0087]
30 This application is based upon and claims the benefit of priority from
Japanese patent application No. 201 1 - 129789, filed on June 10, 20 11, the
disclosure of which is incorporated herein in its entirety by reference.
Industrial Applicability
3
[OOSS]
The present invention is applicable to a layer 2 switch, a bridge device, a
layer 3 switch, a router device, a gateway device, an optical relay device and the
like, each of which performs transmission and reception of frames.
Reference Signs List
[0089]
1 device
2 layer 2 switch
2 1, 22 wireless line termination unit
23 to 26 line termination unit
27 switch unit
271 switch core
272 radio monitoring unit
273 communication path control unit
274 communication rate monitoring unit
3 layer 2 switch
3 1, 32 wireless line termination unit
33 to 36 line termination unit
37 switch unit
371 switch core
372 radio monitoring unit
373 communication path control unit
4 device

WE CLAIM:
1. A switching device comprising:
first wireless line terminating means for transmitting and receiving frames
via a first wireless line;
second wireless line terminating means for transmitting and receiving
frames via a second wireless line;
first line terminating means for exchanging frames with the first wireless
line terminating means;
second line terminating means for exchanging frames with the second
wireless line terminating means;
radio monitoring means for monitoring a state of the first and second
wireless lines, the radio monitoring means instructing the first and second wireless
line terminating means to exchange copy frames with other wireless line
terminating means and to abandon the received frames, in accordance with a
redundancy mode of the first and second wireless lines;
communication path control means for setting the first and second line
terminating means to each be an active system or a standby system in accordance
with a monitoring result obtained by the radio monitoring means as to the state of
the wireless lines; and
a switch core that passes frames to be transmitted to the line terminating
means operating as the active system,
wherein the first and second wireless lines are subjected to a link
aggregation so as to be treated as one virtual line.
2. The switching device according to Claim 1, wherein
in setting a first redundancy mode in which the first line terminating means
operates as the active system and the second line terminating means operates as the
standby system,
the switch core passes transmission frames to the first line terminating
means,
the radio monitoring means instructs the first wireless line terminating
means to pass copy frames of the transmission frames received from the first line
terminating means to the second wireless line terminating means, the radio
-
monitoring means instructing the second wireless line terminating means to
abandon the received frames, and
the second wireless line terminating means transmits the copy frames and
abandons the received frame.
5
3. The switching device according to Claim 2, wherein
when the radio monitoring means senses an abnormality in the first
wireless line while operating in the first redundancy mode, the radio monitoring
means instructs the second wireless line terminating means to stop abandoning the
10 received frames and to pass copy frames of the received frames to the first wireless
line terminating means.
4. The switching device according to one of Claims 1 to 3, wherein
in setting a second redundancy mode in which the first and second line
15 terminating means each operate as the active system,
the switch core passes transmission frames substantially equally to the first
line terminating means and the second wireless line terminating means.
5. The switching device according to Claim 4, wherein
20 when the wireless line terminating means senses an abnormality in the first
or second wireless line while operating in the second redundancy mode, the
wireless line terminating means notifies the communication path control means
about the line with the abnormality, and
the communication path control means sets the wireless line terminating
25 means connected to the line with the abnormality and the line terminating means
exchanging frames with such wireless line terminating means to each be the
standby system.
6. The switching device according to Claim 5, wherein
30 the line terminating means and the wireless line terminating means each
changed to be the standby system by the communication path control means only
perform, as an operation of the standby system, reception of frames.
7. The switching device according to Claim 1, wherein
in stopping a function of the first wireless line terminating means while
operating in a first redundancy mode in which the first line terminating means
operates as the active system and the second line terminating means operates as the
standby system,
the radio monitoring means notifies the communication path control means
about an abnormality in the first wireless line attributed to the first wireless line
terminating means being stopped, the radio monitoring means instructing the
second wireless line terminating means to transmit frames passed from the second
line terminating means, and
in accordance with the notification, the communication path control means
sets the first line terminating means to be the standby system and sets the second
line terminating means to be the active system.
8. The switching device according to any one of Claims 1 to 7, wherein the
wireless line terminating means is structured by a card-shaped removable device.
9. The switching device according to any one of Claims 1 to 8, wherein the
switching device is a layer 2 switch.
10, A method for controlling frame transmission and reception, wherein
a switching device includes first wireless line terminating means for
transmitting and receiving frames via a first wireless line, second wireless line
terminating means for transmitting and receiving frames via a second wireless line,
first line terminating means for exchanging frames with the first wireless line
terminating means, and second line terminating means exchanging frames with the
second wireless line terminating means,
the switching device performs a link aggregation with which the first and
second wireless lines are treated as one virtual line, the switching device
monitoring a state of the first and second wireless lines and instructing the first
and second wireless line terminating means, in accordance with a redundancy
mode of the first and second wireless lines, to exchange copy frames with other
wireless line terminating means and to abandon received frames,
the switching device sets, in accordance with a monitoring result of the
wireless lines, the first and second line terminating means to each be an active
fi 3 4 r l j 7 * - w~L a %
-. (&,; --rd
26
system or a standby system, and
the switching device passes frames to be transmitted to the line terminating
means operating as the active system. n
5 Dated this 2oth day of December 2013
Agent for the Applicant