JPH0457149B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a packet switch, and more particularly, to a switching method in which initial settings after switching are instructed from the packet switch to the line when switching lines in the packet switch. It is something. especially,
This paper relates to a switching method suitable for switching lines in accordance with the X.25 Recommendation since 1980.

[Background of the invention]

With the recent development of LSI technology, communication LSIs such as microprocessors and large-scale memory devices have appeared.

In the case of a packet switch, a central control processing unit (CPU) performs all the control and processing related to the packet switch, rather than a conventional packet switch.
"CCITT Recommendation/X.25 Level 2" now to the line support department
Packet switching equipment has appeared that can reduce the processing time.

In the latter type of packet switching equipment, if it becomes necessary to switch the line handling section, it is naturally necessary to accommodate the line accommodated in the line handling section in another line handling section. At the time of this replacement, take into consideration the case where the line accommodated in the line support unit to be replaced is in use, and the line support unit to be replaced will have X.25 level 2.
It is necessary to take over the control information related to

However, this transfer requires a transfer method such as memory copying, which makes the hardware expensive, so a method is usually adopted that involves waiting until the line accommodated in the line handling unit has finished communicating before replacing it. Often.

However, in packet exchanges that do not carry out call hold billing, there are generally many lines that are in an intermittent state during communication, so the waiting time until communication ends is naturally often long.

Also, in order to shorten this waiting time, there is a method of executing the exchange regardless of whether or not communication is in progress, but as mentioned above, the control information of "X.25 level 2" is not carried over. communication disconnection occurs.

Therefore, the above-mentioned replacement method has the disadvantage that the maintenance function and serviceability of the packet switch are significantly reduced.

[Purpose of the invention]

The purpose of the present invention is to immediately switch over a line accommodated in the current line support unit (especially a line that complies with the X.25 recommendation since 1980) to a backup line support unit without disconnecting communication. The objective is to provide a line switching method that makes it possible.

[Summary of the invention]

The line switching method of the present invention uses a constant response from the packet switch that means "busy" according to "CCITT Recommendation/X.25 Level 2" when switching the line accommodated in the active line handling unit to the backup line handling unit. The communication is transmitted at intervals, the line is switched while the packet switch and the terminal line are in a transmission suppressed state, and after switching, the initial settings are made by the operation mode setting command from the packet switch and communication is resumed. Features.

[Embodiments of the Invention] The present invention will be described in detail below with reference to the accompanying drawings. 1st
The figure is an overall system diagram for explaining the line switching system of the present invention, and FIG. 2 is a flowchart for explaining it. In the figure, 1 is the central control processing unit (CPU) in the packet switch, 2a is the active line support unit, 2b is the backup line support unit, 3 is the line accommodated in the active line support unit, and 4 is the line 3. a switching instruction signal for instructing switching from the working line corresponding section 2a to the backup line corresponding section 2b; 5 is a signal for instructing the backup line corresponding section 2b to transmit an operation mode resetting command to the line 3; 6; is a command that initializes the "X.25 level 2" data link state with line 3 and requests operation mode setting (asynchronous balanced mode/SABM), 7
is a response (non-number acknowledgment/UA) that indicates that the command 6 has been received, 8 is a data transmission ready report signal that indicates that communication can be started, and 10 is a rotation support part that should be operated by CPU 1. a parameter specification signal that signals a state parameter;
11 is a switching preparation completion report signal indicating that both the working line handling unit 2a and the backup line handling unit 2b are ready for switching, and 12 is a switchover preparation completion report signal indicating that the current line handling unit 2a and the backup line handling unit 2b are ready for switching, and 12 is a signal indicating that the line 3 is accommodated from the working line handling unit 2a to the backup line handling unit. 13 is a switching completion report signal indicating that the switching operation has been completed and communication has resumed; 14 is a switching signal that indicates that the local station is busy and notifies line 3 that reception is temporarily unavailable. Busy command 15 is a frame (reception refusal/RNR) that notifies that line 3 is temporarily unreceivable.

Although not shown, the current line support section 2
a and the spare line support section 2b are connected to the CPU 1.
This means that each command sent from CPU 1 to each line corresponding unit has been accepted and execution has started.
An ACK signal is sent back.

An example of a switching sequence will be described below with reference to FIGS. 1 and 2.

First, when the CPU 1 receives the switching instruction signal 4,
The local station busy command 14 is received in order to start an operation for switching to the current line corresponding section 2a. When the current line support unit 2a receives the local station busy command 14, it sends a frame (RNR) signal 1 to the line 3.
Send 5.

Naturally, a packet terminal is connected to the end of the line 3, and the following explanation will be continued on the assumption that transmission and reception will be performed between the packet terminal and the packet terminal. When the line 3 receives the frame (RNR) signal 15, it determines that the current line support section 2a is temporarily in a receivable state, and stops transmitting to the current line support section 2a.

At this point, line 3 and current line corresponding section 2a
Since there are no frames sent and received between the two, this state is used to perform switching.

However, in order to carry out the switching, the local station busy command 14 is repeatedly sent out at regular intervals so as to continue this state intermittently.

The local station busy command is used during the period until the switching operation described later is completed (switching work is completed), that is, the switching is completed, which means that communication between the spare line corresponding section 2a and the line 3 is ready to resume. Report signal 1
3 is sent intermittently from CPU1. Incidentally, upon receiving the local station busy command 14, the currently used line corresponding section 2a sends an ACK signal back to the CPU 1.

Next, the operation for switching to the backup line support section 2b will be explained. First, the CPU 1 is sent a parameter designation signal 10 to the standby line correspondence section 2b so that it can operate as a working circuit. When the ACK signal indicating that the parameter designation signal 10 has been received is returned from the backup line support unit 2b, the backup line support unit 2b sends the command signal 6 to the line 3 when connected to the line 3. The operation mode resetting command 5 is sent to. This command is sent after the connection switching between the backup line support unit 2b and the line 3 is completed, and the response signal 7 sent from the line 3 in response to the SABM command 6, which means setting the operation mode, is sent to the backup line support unit 2b. The signal is interrupted until the section 2b receives the signal. Upon receiving the operation mode resetting command 5, the spare line support unit 2b sends back an ACK signal to the CPU 1 indicating that it has received the command 5, and attempts to send the SABA command 6 to the line 3, but In this case, since the line 3 and the backup line corresponding section 2b are not physically connected in the state before switching, the SABM command 6 is sent to the line 3.
will not be reached.

Here, a switching preparation completion report 11 indicating that preparations for switching of the backup line support section 2b are completed is sent.
Report from CPU1. After transmitting the switching preparation completion report 11, the CPU 1 sends the spare line support unit 2b
Waits for a data transmission report signal 8 indicating that communication with line 3 can now be started.

From the active line support unit 2a to the backup line support unit 2
The switching to b is carried out by the switching signal 12. As a result of this switching, the line 3 transmits a response signal (UA) 7 in response to the SABM command 6 from the standby line corresponding section 2b. When the spare line support section 2b receives the response signal 7, it sends a data transmission possible report signal 8 to the CPU 1.

The CPU 1 learns from the spare line handling section 2b that communication with the line 3 can be resumed, and sends out a switching completion report signal 13.

As mentioned above, in the "X.25 level 2" of the packet switch, switching is completed while the reception is temporarily disabled, and by issuing the SABM command, the temporary reception disabled state is resolved and the initial settings are performed. Implement.

After that, it becomes possible for line 3 and CPU 1 to communicate again. In addition, CPU1 switching instruction 4, CPU1
The recipients of the switching preparation completion report signal 11 and the switching completion report signal 13 are not included in the scope of the present invention and will not be described here, but they are, for example, a maintenance typewriter included in a packet switch.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, when switching from a working line handling unit to a backup line handling unit in a packet switch, the “X.25 Switching is performed after temporarily suppressing transmitted and received frames in the data link conforming to "Level 2", and after switching,
Since communication can be started after the data link is initialized, it is possible to perform switching almost immediately and avoid disconnection of communication. This is particularly effective in terminals where the operation mode of the data link can be set by a command from a packet switch.

[Brief explanation of the drawing]

FIG. 1 is a line switching system diagram for explaining the present invention, and FIG. 2 is a switching sequence diagram. DESCRIPTION OF SYMBOLS 1... Central control processing unit, 2a... Current line support unit, 2b... Backup line support unit, 3... Line, 4... Switching instruction signal, 5... Operation mode resetting command, 6... command (SABM) signal,
7...Response (UA) signal, 8...Data transmission possible report signal, 10...Parameter designation signal, 1
1...Switching preparation completion report signal, 12...Switching signal, 13...Switching completion report signal, 14... Own station busy command signal, 15...Frame (RAR)
signal.

Claims (1)

[Claims] 1 CCITT Recommendation: In a line switching system in a packet switch where processing up to X.25 level 2 is performed in the line handling unit, when switching any line accommodated in the active line handling unit to the backup line handling unit,
A frame indicating that the current station is busy is sent from the working line handling unit to an arbitrary line, and the connection between the working line handling unit and the line is switched to the connection between the backup line handling unit and the line at regular intervals. The packet switch instructs the working line handling unit to intermittent transmission until the completion of the process, and at the same time, the arbitrary line is switched from the working line handling unit to the backup line handling unit. After that, a frame indicating operation mode setting is sent from the spare line corresponding section to the arbitrary line, and a response signal transmitted from the arbitrary line in response to the frame indicating operation mode setting is sent to the spare line. The packet switch instructs the backup line support unit to continue transmitting until the support unit receives it, and after switching the line, the CCITT Recommendation X.25 is transmitted between the line and the backup line support unit. A line switching method characterized by restarting communication from an initial setting state using level 2 control.