JP3446920B2 - Method of checking PVC status of frame relay - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frame relay PVC (Permanent Virtual Circuit) state confirmation method, and in particular, restarts communication after confirming that the link state has recovered from an abnormal state to a normal state. This is to shorten the time to do.

[0002]

2. Description of the Related Art A frame relay is a LAN (local
This is a high-speed packet switching system that was introduced to increase the speed of communication between areas and networks. The 25-packet exchange method (transmission speed 64 Kbps) is simplified to enable high-speed data transfer (1.5 to 2 Mbps). Since the error rate of the recent transmission line is extremely small, this may be done.

Frame relays include conventional X.264. Similar to the 25 system, there is a PVC (fixed party connection) in which the other party is registered in advance in the network and is used as a dedicated line. The PVC in the frame relay does not need to set up a call in advance, and if the frame is transmitted with a specific DLCI (data link connection identifier), the frame is transmitted to a fixed partner.

However, if the link state becomes abnormal due to some reason and communication with the other user becomes impossible, there is no call control itself, and the cause must be estimated by the user. As a procedure therefor, a PVC status confirmation procedure is specified.

This PVC state confirmation procedure has a function of confirming the normality of the link state between the user and the frame relay network and a function of confirming the PVC state between the users. With these functions, the user can grasp the normality of the PVC between the users. In addition, since the link state between the user and the network can be grasped by the network, quick failure recovery can be performed.

[0006] Specifically, the link integrity confirmation procedure defined in the TTC (Telecommunication Technology Committee) standard JT-Q933 is performed. That is, T between the user and the network
The transmission of the first status inquiry (STATUS ENQ) message and the reception of the first status display (STATUS) message in response to this are repeated every 391 seconds (10 seconds) to confirm the transmission number of the status display message. By doing so, the normality of the link state between the user and the network is confirmed.

A second status inquiry message requesting a full status display to the network is transmitted at every N391 (6 times) transmission intervals of the status inquiry message, and a second status inquiry message for the second status inquiry message is transmitted.
Receive the status display message of. This second status display message includes confirmation of the link status and confirmation of the PVC status, and it is possible to confirm all the PVC statuses that have been set.

That is, it is possible to confirm whether the state of the PVC is active (communication is possible) or inactive (communication is not possible) by the active bit (A bit) of the frame format of the status display message. When the user receives the inactive, the user determines that the PVC link of the corresponding DCLI cannot communicate until the inactive is received.

If N392 times (3 times) or more out of the responses to the latest N393 times (4 times) transmission of the status inquiry message are errors, the abnormality of the link state is confirmed and the data communication is stopped. . To confirm that the link status has recovered from the abnormal status to the normal status, continue the link integrity check procedure, and if the status display message is received without error for N392 consecutive times, the status is recovered to the normal status. Check.

Incidentally, T391, N391, N392, N
Reference numeral 393 denotes a parameter of the PVC status confirmation procedure, and T391 is a link integrity confirmation timer, which represents a time interval at which the user transmits a status inquiry message, and is usually 1
Set to 0 seconds. If the status display message is not received from the network within T391 seconds after transmitting the status inquiry message, it is determined as an error.

N391 is a full state display counter, which sets the transmission interval of the second state inquiry message for requesting the full state display once every N391 times the user transmits the first state inquiry message. To do. Normally set to 6 times.

N392 is a fixed failure determination threshold, which is the latest N
When N392 times of errors are detected in 393 times of events, it is determined that the link status is abnormal, and N39
If there is no error twice consecutively, it is determined that the link status has recovered to the normal status. Usually set to 3 times.

N393 is a monitor event counter, which counts the number of monitor events for detecting an abnormal state of the link state. An event is defined as the sending of a status inquiry message. Usually set to 4 times.

[0014]

DISCLOSURE OF THE INVENTION The conventional PVC described above
In the status confirmation procedure, in order to restart the data communication after confirming that the link status has recovered from the abnormal status to the normal status, the N392 (third) consecutive normal response happens to be N times.
If the response is the 391th (sixth) full state display, D
Since active / inactive for each CLI can be immediately determined, data communication can be immediately performed to the other user in the active state. However, the N392 continuous normal response does not always match the N391 full-state display response, which is a problem of probability.

Also, T391, N391, N392, N
Since 393 is a fixed value, a minimum waiting time of “T391 × N393 + α (link integrity confirmation full status display response waiting time)” seconds is required to detect an abnormal condition. α is the processing time of the device (less than 1 ms).

To detect the recovery, "T391 ×
N392 + β (link integrity confirmation response reception time) ”in addition to the minimum time of“ second ”and a response of the link integrity confirmation full status display (second status display message)“ T391 × N3 ”
A combined maximum latency of 91 "seconds is usually required.
β is the processing time of the device (less than 1 ms).

Further, by using the protocol constants after the recovery and before the communication is restarted, the difference between the actual recovery and the user's recovery confirmation is at least "T391 × N392 +".
It becomes "α" seconds and the maximum is "T391 x N392 + β + T3.
It becomes 91 × N391 ″ seconds, and there is a variable time before communication restart. For this reason, there arises a disadvantage that an originally communicable state is changed to an incommunicable state.

The present invention has been made to solve such a problem, and shortens the time from the confirmation of the recovery of the link state from the abnormal state to the normal state to the resumption of communication between the user and the network. The purpose is to do.

[0019]

SUMMARY OF THE INVENTION The method of checking the PVC status of a frame relay according to the present invention sends a first or second status inquiry message to a network at predetermined time intervals, and the first or second status inquiry message is sent to the network.
The first status display message for the status inquiry message is received from the network to check the link status, and the second status display message for the second status inquiry message is received from the network to check the link status and the PVC status. ,
The predetermined time interval is switched depending on whether the link status is normal or abnormal, and the transmission interval of the second status inquiry message is switched depending on whether the link status is normal or abnormal. When the link status is abnormal, the second status inquiry message is sent. Is transmitted to the network at a time interval and a transmission interval at the time of abnormality, and a second status display message corresponding thereto is received from the network.

In this case, the PV of the frame relay of the present invention
In the C state confirmation method, when the link state is abnormal, the transmission interval of the second state inquiry message is once and the second state display message is received from the network every time.

Further, the PVC state confirmation method of the frame relay of the present invention is such that the abnormality of the link state is confirmed at the time when a C LLM (Integrated Link Layer Management) message is received from the network.

According to the present invention, the time interval for transmitting the first or second status inquiry message and the transmission interval for transmitting the second status inquiry message are automatically switched between normal time and abnormal time. Since the monitoring interval is set to be shorter than that in the normal state when an abnormality occurs, the time from confirming that the link state has recovered from the abnormal state to the normal state and then confirming the PVC state can be significantly shortened. it can.

In particular, if the transmission interval for transmitting the second status inquiry message for requesting the full status display is set to be 1 when there is an abnormality, the second status display message will be received every time. The confirmation that the state has recovered from the abnormal state to the normal state and the confirmation of the PVC state can be performed at the same time, and the data communication can be restarted in the minimum time.

Further, by confirming the abnormality of the link state by the CLLM message, the abnormality of the link state can be confirmed in a short time.

[0025]

1 is a block diagram of a frame relay communication device to which a method for confirming a PVC state of a frame relay according to the present invention is applied. The communication device 1 includes a CPU 2 having a microcomputer configuration for controlling the entire device to promote confirmation of a network abnormality recovery of a frame relay, a RAM 3 as a memory for storing logical variables, and an EEP as a memory for storing.
A ROM 4, a frame relay network, and an LED 5 and a clock 6 indicating the link status of 10BASE-T are provided.

Further, a WAN (wide area network) controller 7 for controlling data to be transmitted or received to the frame relay network, a LAN controller 8 for controlling data to be received or transmitted from a LAN, a WAN controller 7 and a LAN controller 8 The RAM 9 is a memory that stores data transmitted and received by the.

Further, a controller 10 for physically controlling the frame relay, a controller 11 for physically controlling 10BASE-T, and a controller 12 for physically controlling the RS-232C are provided.

FIG. 2 shows the P of a frame relay according to the present invention.
It is a sequence diagram which shows Embodiment 1 of the VC state confirmation method.

First, the link status between the user and the network is normal, and the user makes a first status inquiry (STAT) to the network.
US ENQ) Send message SE (step T
10). This message SE is a link integrity confirmation message. The network receives this message SE and responds with the first status display (STATUS) message S (step T11). The user receives this message S and confirms the normality of the link state.

Next, when the link status becomes abnormal and the user sends a status inquiry message SE to the network (step T12), the response of the status display message S indicates that the reception sequence number is abnormal, for example. Then, the user recognizes the first abnormality (step T13).
When this transmission and reception are repeated three times (step T12
Up to T17), the latest N393 (4 times) transmission of the status inquiry message SE (T10, T12, T14, T1)
In 6), N392 times (three times) result in an error, and the user confirms the abnormality of the link state and stops the data communication.

Next, the set value of the timer T391 is changed from Ta seconds (10 seconds) at the time of normal determination to Tb seconds (5 seconds at the time of abnormal determination).
Second), and the set value of the counter N391 is changed from Na times (6 times) at the time of normal determination to Nb times (1 time) at the time of abnormal determination. Then, the second status inquiry message SE-F of the full status display request is transmitted from the user to the network at the newly set Tb second interval (step T18).

The user sends a second status inquiry message every Tb seconds, and a second status inquiry message from the network for this message is sent.
If the response of the status display message SF of No. 3 is normal for three consecutive times (steps T18 to T23), the user sets N39.
It is confirmed that the status display message has been received without error twice (three times) and the link status is restored to the normal status.

Since the user confirms this recovery by receiving the second status display message S-F (step T23), the user is active (communicable) for each other user (that is, DLCI) from this message S-F. )
Alternatively, the inactive (communication impossible) state can be confirmed, and the data communication is immediately resumed to the partner user who has received the active state. In this way, data communication can be restarted in the minimum time.

When the link status returns to the normal status, the timer T
The value of 391 is returned to Ta seconds at the time of normality determination, the value of N391 is returned to Na times at the time of normality determination, and the first status inquiry message SE is transmitted (step T24) and The status display message S of No. 1 is received (step T25). Further, the second state inquiry message SE-F is transmitted and the second state display message S-F is received every Na times.

FIG. 3 shows the P of a frame relay according to the present invention.
It is a sequence diagram which shows Embodiment 2 of a VC state confirmation method. The second embodiment is the same as the above-described first embodiment except that the abnormality of the link state is confirmed by receiving a CLLM (Integrated Link Layer Management) message.

First, the link state between the user and the network is in a normal state, and in this state, the user transmits the first state inquiry message SE to the network (step T30). This message SE is a link integrity confirmation message.
The network receives this message SE and displays the first status (ST
(ATUS) Respond to message S (step T3)
1). The user receives this message S and confirms the normality of the link state.

Next, when the link status becomes abnormal and the first status inquiry message SE is transmitted from the user to the network (step T32), the response of the first status display message S becomes, for example, the reception sequence number. If an abnormality has occurred, the user recognizes the abnormality (step T3).
3).

Then, the network notifies the user of a CLLM (Integrated Link Layer Management) message (step T34). This message is a frame in which the network autonomously generates a frame and notifies the user of the network state, and has a notification function such as a light congestion notification, a heavy congestion notification, a device failure notification, and an all frame discard notification.

Upon receiving the device failure notification message, the user immediately confirms that the device is in an abnormal state and stops the data communication. Even after the notification of the CLLM message, even if the link status is restored to the normal status, a message to that effect is not autonomously notified from the network. Therefore, the user sets the setting value of the timer T391 to Ta seconds ( Change from 10 seconds) to Tb seconds (5 seconds) at the time of abnormality determination, counter N3
The set value of 91 is changed from Na times (6 times) at the time of normal determination to Nb times (1 time) at the time of abnormal determination. Then, the user transmits a status inquiry message SE-F requesting a full status display to the network at a newly set Tb second interval (step T).
35).

That is, when the abnormal state is notified by the CLLM message, the user transmits the second state inquiry message SE-F which is a request for the full state display every Tb seconds. If the response of the second status display message S-F to this message SE-F is normal for three consecutive times (steps T35 to T40), the user displays the status display message N392 times (three times) in succession without any error. Since it has been received, it is determined that the normal state has been restored.

At the same time as the user confirms that the link status has been restored to the normal status, the user can activate (communicate) or communicate with each other user (ie, DLCI) by the second status inquiry message SE-F (step T40). Since the inactive (communication impossible) state can be confirmed, the data communication is immediately resumed to the partner user who has received the inactivity. In this way, data communication can always be resumed in the minimum time.

When the link status returns to the normal status, the timer T
The value of 391 is returned to Ta seconds at the time of normal determination, the value of N391 is returned to Na times at the time of normal determination, and the first status inquiry message SE is transmitted (step T41) at the monitoring interval that has little influence on normal communication and The status display message S of No. 1 is received (step T42). Further, the second state inquiry message SE-F is transmitted and the second state display message S-F is received every Na times.

FIG. 4 shows the P of a frame relay according to the present invention.
FIG. 11 is a sequence diagram showing the third embodiment of the VC state confirmation method, showing a sequence diagram when the user side has already confirmed the abnormal state of the link state at the start-up.

First, the timer T391 is set to Ta when the normality is determined.
Seconds to Tb seconds at the time of abnormality determination
The setting of 91 is changed from Na times at the time of normality determination to Nb times at the time of abnormality determination. Then, a second status inquiry message SE-F requesting a full status display from the user to the network at Tb second intervals.
Is transmitted (step T50).

If the response of the second status display message S-F to this message SE-F is normal for three consecutive times (steps T50 to T55), N392 times (three times).
Since the status display message has been received without any continuous error, the user confirms that the link status has been restored to the normal status.

At the same time as this confirmation, the user is informed of the active (communication possible) or inactive (communication impossible) status for each partner user (that is, for each DLCI) by the second status display message SF (step T55). Since it can be confirmed, the data communication can be immediately resumed to the partner user who receives the fact that the user is active. In this way, data communication can always be resumed in the minimum time.

When the link status returns to the normal status, the timer T
The value of 391 is returned to Ta seconds at the time of normality determination, the value of N391 is returned to Na times at the time of normality determination, and the first status inquiry message SE is transmitted (step T56) and The status display message S of No. 1 is received (step T57). Further, the second state inquiry message SE-F is transmitted and the second state display message S-F is received every Na times.

When the determination threshold value N392 is changed from 3 times to 1 time and the second status display message SF is normal even once, it is determined that the link status is restored to the normal status. It is possible to resume data communication faster.

[0049]

According to the present invention, the time interval T391 for transmitting the first or second status inquiry message and the transmission interval N391 for transmitting the second status inquiry message for making a full status display request are set in the link status. Automatically switches between normal and abnormal conditions, when normal, sends and receives full status display request messages at monitoring intervals that have little impact on communication, and when abnormal, full status display request messages at shorter monitoring intervals I am trying to send and receive.

As a result, it is possible to shorten the time from confirming that the link state has recovered from the abnormal state to the normal state until confirming the active / inactive state of the other user, so that data communication can be resumed in a short time. be able to.

In particular, by setting the transmission interval N391N for transmitting the status inquiry message for making a full status display request to once in the case of an abnormality, it is confirmed that the link status has recovered from the abnormal status to the normal status, and the other user Since the active / inactive confirmation of can be performed at the same time, the data communication can be restarted in the minimum time.

[Brief description of drawings]

FIG. 1 is a block diagram of a frame relay communication device to which the present invention is applied.

FIG. 2 is a sequence diagram showing a PVC state confirmation method for a frame relay according to the first embodiment of the present invention.

FIG. 3 is a sequence diagram showing a method for confirming a PVC state of a frame relay according to the second embodiment of the present invention.

FIG. 4 is a sequence diagram showing a PVC state confirmation method for a frame relay according to a third embodiment of the present invention.

[Explanation of symbols]

SE First status inquiry message S First status display message SE-F Second status inquiry message S-F Second status display message T391 Link integrity confirmation timer (predetermined time interval set) N391 Full status display Counter (set a predetermined transmission interval) N392 Fixed failure determination threshold N393 Monitoring event counter

Claims (3)

(57) [Claims] 1. A link status is confirmed by transmitting a first or second status inquiry message to the network at predetermined time intervals and receiving a first status display message for the first status inquiry message from the network. Then, the second status display message for the second status inquiry message is received from the network to obtain the link status and PVC.
Check the status, switch the time interval between normal and abnormal link status, switch the transmission interval of the second status inquiry message between normal and abnormal link status, and when abnormal link status A frame relay PV for transmitting the second status inquiry message to the network at the abnormal time interval and transmission interval and receiving the second status display message for the second status inquiry message from the network.
C state confirmation method. 2. When the link status is abnormal, the second
2. The PVC status confirmation method for a frame relay according to claim 1, wherein the second status display message is received from the network every time the transmission interval of the status inquiry message is 1. 3. The frame relay PVC state confirmation method according to claim 1, wherein the abnormality of the link state is confirmed at the time when the C LLM message is received from the network.