JPH0964908A - Bypass method in frame relay network - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain bypass processing without reducing the number of PVCs able to be set in the bypass method in a frame relay network in which a frame is transferred through bypassing on the occurrence of a fault. SOLUTION: In the frame relay network of a TDM transmission by a time slot system, PVC routing information is registered on a routing table 6 and a time slot corresponding to the PVC routing information is allocated and a time slot of a bypass route is reserved and their time slots are registered in a TS registration section 8. When a monitor section 10 detects occurrence of a fault between nodes 11 and 13 , a time slot switch section 9 is controlled to select a time slot of a bypass route registered in a TS registration section 8 and the frame is bypassed and transferred by a time slot of the bypass route.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a detour method in a frame relay network for detouring and transferring a frame when a failure occurs. Frame Relay Network (Frame Relay Netwo
rk) transfers data in units of variable length frames, enables high-speed communication by a simple protocol, and can set a plurality of data links on a physical line by a logical multiplexing function. In such a frame relay network, when a line or node fails, all frames passing through the failed part are discarded, so that communication is continued even when a failure occurs. It is requested to support the bypass function.

[0002]

2. Description of the Related Art FIG. 6 shows a frame format of a frame relay, in which an address part having a flag F added before and after, a user data part, a frame check sequence FC
It is composed of S and S. Further, the address part is a data link connection identifier DLCI (Data Link Connect
ion Identifier), an address field extension bit EA (Extended Address Dress Field Bit), and a forward explicit congestion notification bit FECN (Forward Explicit).
Congestion Notification) and a backward explicit congestion notification bit BECN (Backward Explicit Congestion).
Notification) and discardable indication bit DE (Disca)
rd Eligibility Indicator).
The user data section has a length of 1 to 4096 octets, for example.

In addition, fixed connection (PVC; Permanent V)
In the irtual Circuit) service, the frame is transmitted to the other user by transmitting the frame with the specific data link connection identifier DLCI without performing the call setup procedure. When a failure occurs in this frame relay network, the frame relay network sends a CLLM (Consolidated Link L) to the user.
ayer Management) message. This causes the user to stop sending frames.

Even if a failure occurs in a certain node of the frame relay network or a line between the nodes, if the communication between the users needs to be continued, the PVC of the detour route is set. Then, when the occurrence of a failure is detected, the detour processing is performed based on the PVC of the set detour route, the frame discarding at the failure location can be avoided, and the frame transfer can be continued.

FIG. 7 is an explanatory diagram of a conventional detouring process.
The processing in layer 2 is shown. At the start of communication, PVC routing information is registered in the routing table of the node of the frame relay network (a), and the bypass PVC is registered in the routing table (b). Then, line monitoring is performed by polling or the like (c), it is determined whether a line fault or node fault is detected (d), and if a fault is detected, PVC switching processing is performed at the fault detection node. (e)
. That is, the routing information is rewritten, and for all PVCs affected by the detected failure, the PVC switching information is notified to all nodes through which the PVCs pass.

[0006] Thereby, the frame is transferred by the bypass PVC, and the frame transfer between the users is continued.
Then, it is judged whether or not the failure recovery is detected (f), and when the failure is recovered, the PVC switching processing is performed in the node which detects the recovery (g). That is, the routing information is rewritten, and the PVC switching information is notified to all the nodes through which the restored PVC passes.

[0007]

As described above, in the conventional example, it is necessary to set the normal PVC and the detouring PVC in duplicate in order to transfer the frame by detouring when a failure occurs. There is. Therefore, PV that can be set between certain nodes
If the number of C is 1024, for example, P
The number of VCs is 512, which is half that number. That is, there is a problem that the utilization efficiency of the frame relay network is reduced. Further, it is necessary to add a processing function for switching to the bypass PVC to each node, which causes a problem that the frame transfer processing in each node is affected. An object of the present invention is to perform detour processing without reducing settable PVC.

[0008]

A detour method in a frame relay network according to the present invention is a time slot type TD.
In a frame relay network based on M (Time Division Multiplexer) transmission, the permanent fixed connection (PVC) routing information is registered in the routing table, and the time slot corresponding to the permanent fixed connection (PVC) routing information is allocated and detoured. A time slot for detour in the route is reserved, and when a failure occurs, the time slot for detour is switched to transfer the frame by detour.

In the reservation of the detour time slot, the time slot for the control signal and the time slot for the data transfer can be reserved.

Further, monitoring of the nodes is performed by looping back the supervisory signal by the control signal time slot, and the normality of the detour route is confirmed by the supervisory signal by the reserved control signal time slot for detour by detecting the failure occurrence. After that, the frame can be detoured by switching to the reserved time slot for data transfer for detouring.

[0011]

[Operation] At the start of communication, PVC is added to the routing table.
The routing information is registered, a time slot is assigned corresponding to the PVC routing information, and the frame is transferred by the time slot. Further, a detour time slot is reserved, and if a failure occurs, the reserved time slot is switched to continue the frame transfer. That is, the bypass transfer can be performed by switching the time slot without being aware of the bypass route by the PVC of the layer 2.

A time slot for a control signal for transferring a supervisory signal and a time slot for data transfer for transferring data between users are reserved as detour time slots.

Further, a supervisory signal is transferred by a time slot for a control signal, and the supervisory signal is looped back to monitor whether there is a fault in a node or a fault in a line between nodes. When the occurrence of a failure is detected, the supervisory signal is transferred by the control signal time slot for detour to confirm the normality of the detour route.
When the detour route is normal, the reserved time slot for data transfer is switched to continue frame transfer.

[0014]

DETAILED DESCRIPTION FIG. 1 is a schematic view of another preferred embodiment of the present invention, 1 ₁
1 to ₃ are nodes constituting the frame relay network, 2 ₁ and 2
₂ the user of the terminal device, 3 ₁ to 3 ₈ ports, 4 PV
C routing unit, 5 a time slot processing unit, 6 a routing table, 7 a logical path switch unit (PSW) for performing a routing process, 8 a TS registration unit for registering a detour destination time slot, and 9 an input time slot. To an output time slot, a time slot switch unit (TSW), 10 is a monitoring unit for detecting a fault, and 11 _{1 to} 11 ₃ are lines between nodes.

The nodes 1 ₂ and 1 ₃ have the same configuration as the node 1 ₁ although the PVC routing unit 4 and the time slot processing unit 5 are omitted. When the PVC routing information of the terminal devices 2 ₁ and 2 ₂ is registered in the routing table 6, the time slot corresponding to the PVC routing information and the detour time slot are registered in the TS registration unit 8. For example, a time slot for transmission from the port 3 ₂ to the line 11 ₁ is assigned as a normal time slot, and a time slot for transmission from the port 3 ₃ to the line 11 ₂ is reserved as a detour time slot.

[0016] Thus, during normal, the time slot switch unit 9 is controlled according to the time slot which is registered in the TS registering unit 8, the data from the terminal device 2 _1, time slot to be transmitted to that timeslot (line 11 ₁ ), It is transferred to the node 1 ₂ and then transferred from the node 1 ₂ to the terminal device 2 ₂ .

When the monitoring unit 10 detects that a failure has occurred in the line 11 ₁ , the time slot switch unit 9 is controlled to switch to the detour time slot registered in the TS registration unit 8. As a result, the time slot sent to the line 11 ₁ is switched to the time slot sent to the line 11 ₂ . This time slot switching information is notified from the node 1 ₁ to the node 1 ₃ by a time slot for a control signal. Therefore, the data from the terminal device 2 _{1 is transferred} from the node 1 ₁ to the node 1 ₂ via the node 1 ₃ and then transferred from the node 1 ₂ to the terminal device 2 ₂ .

2A and 2B are explanatory views of the detouring operation of the embodiment of the present invention. FIG. 2A is a normal state, FIG. 2B is a processing by the time slot switch unit after the detouring processing, and in FIG. , The time slot switch unit TSW is a channel ch.
Time slots TS0 → TS1 for 1 and ch2
1, TS1 → TS12 and TS2 → TS22 are switched. Further, L1 and L1 'represent control signals. Further, the case where the channel ch2 is selected as a detour for the channel ch1 and the time slots TS21 and TS23 thereof are reserved for the control signal and the data transfer is shown.

The monitoring unit 10 (see FIG. 1) detects the presence / absence of a failure based on the monitoring signal. When the failure is detected, the time slot switch unit TSW causes the TS registration unit 8
Switch to the detour time slot registered in (see FIG. 1). That is, time slots TS0 → TS21, TS
Switching from 1 → TS23 and TS2 → TS22 is performed, and data in the time slot TS12 of the channel ch1 is transferred in the time slot TS23 of the channel ch2. The control signal L1 ′ of the channel ch1
Indicates the case of sending for failure recovery detection.

FIG. 3 is an explanatory diagram of the detouring process according to the embodiment of the present invention. For example, when communication is performed between the terminal devices 2 ₁ and 2 _{2 in} FIG. Register with (A1). Along with the registration of the routing information, the time slot (TS) is allocated to each channel (B1), the monitoring time slot (TS) is allocated to each physical line (B2), and the detour time is also allocated. Assign slot (TS) (B
3). That is, each time slot (TS) is registered in the TS registration unit 8. Time slot switch section (TS
W) 9 switches the time slot according to the registration content of the TS registration unit 8.

Further, the line is monitored by detecting the error of the monitor signal transmitted by the monitoring time slot and the return collation (B4), and it is judged whether or not the line failure or the node failure has occurred (B5), and the failure is detected. By this, the time slot (TS) switching process is performed at the failure detection node (B
6). That is, the time slot (TS) for detour is switched. Therefore, the data transferred in the normal time slot is switched to the detour time slot due to the occurrence of a failure and transferred.

Then, it is judged whether or not the failure recovery is detected (B7). For example, the fault signal channel ch1 is generated by the monitoring signal L1 ′ transmitted to the channel ch1 of FIG.
It is possible to monitor whether or not the failure recovery of. Then, in the event of failure recovery, the time slot (TS) at the recovery detection node
Switching processing is performed (B8). That is, the detour time slot is switched to the regular time slot (TS).

FIG. 4 is a diagram for explaining the detour procedure according to the embodiment of the present invention. As shown in FIG. 4A, the time slot TS12 of the line 11 ₁ between the nodes 1 ₁ and 1 ₂ is indicated by a solid arrow. data is transferred, the transfer monitoring signal by a time slot TS11 is as indicated by the dotted line arrow, to determine the presence or absence of an error by receiving the monitoring signal node 1 _2, the node 1 ₁ by folding it if no error Send out.
The node 1 ₁ collates the returned monitoring signal with the transmitted monitoring signal to monitor whether or not the nodes 1 ₁ and 1 ₂ are normal.

[0024] Although performs transmission and reception of similar monitoring signal even in a node 1 _2, when detecting an error in the monitoring signal from the node 1 _1, the error detection information to the monitoring signal folded to node 1 ₁ Add and send. In this case, node 1 ₁
In this case, it can be determined that the device or the line in the direction from the node 1 ₁ to the node 1 ₂ has failed. The detection of a failure occurrence by such a monitoring signal is performed in FIG.
The monitoring unit 10 of FIG.

Between the nodes 1 ₁ and 1 _{3 and} between the nodes 1 ₃ and 1
Also in between _2, as well as between nodes 1 _1, 1 _2, and sends a monitor signal by a time slot for the control signal, by folding from the opposite node, and performs monitoring between nodes.

A data link connection identifier DLCI from a terminal device (not shown) accommodated in the node 1 ₁
It is possible to set a logical path, for example, a 16, a data link connection identifier DLCI, for example 17 for node 1 _2. Nodes 1 ₁ and 1 _{2 in} normal state
For the time slot TS12 for data transfer between
A time slot TS23 for data transfer between the detour nodes 1 ₁ and 1 ₃ is reserved. In that case, a time slot for transferring the control signal to the detour route is also reserved. Such detour control signal time slots and data transfer time slots are registered in the TS registration unit 8.

FIG. 4B shows the case where a failure occurs in the line 11 ₁ , and as described above, when the failure occurrence is detected by the error detection of the supervisory signal by the time slot TS11 in the node 1 ₁ , The control signal time slot reserved for detour confirms the normality of the line 11 ₂ , node 1 ₃ , and line 11 ₃ of the detour route indicated by the dotted arrow. That is, when a failure occurrence is detected in the monitoring unit 10 in FIG. 1, the time slot switch unit 9 is controlled so as to switch to the bypass control signal time slot registered in the TS registration unit 8, and the control signal after notifying the switching of the time slots to node 1 ₃ by use time slots, it transmits the monitor signal to the control signal time slots to confirm the normality of the bypass route.

When the monitoring section 10 confirms the normality, it controls the time slot switch section 9 so as to switch from the time slot TS12 to the data transfer time slot TS23 registered in the TS registration section 8. As a result, as shown in FIG. 4C, by switching the time slot from TS12 to TS23, the node 1 is routed through the line 11 ₂ , the node 1 ₃ , and the line 11 ₃ that bypass the line 11 _{1 in} which the failure has occurred. ₂ , the data can be transferred as indicated by the solid arrow.

FIG. 5 is an explanatory diagram of a logical path and a physical path, and the layer 1 has time slots TS ₀ , TS ₁ and TS.
₂ , ..., as shown in (A), the time slot T
The data is transferred from S ₀ to the time slot TS ₁ as indicated by the solid line arrow, and at the layer 2 at that time, the PVC arriving at DLCI = 16 is DLCI =
17 shows the case of sending as indicated by the dotted arrow.

Assuming that the time slot TS ₂ is a time slot reserved for detour, failure (B)
As shown in, the time slot TS ₁ is switched to the time slot TS ₂ . In that case, the data link connection identifier DLCI remains the same and the logical path recognized by the layer 2 is not changed, so that the process in the node is simplified.

[0031]

As described above, the present invention registers PVC routing information in the routing table 6 in a TDM transmission-based frame relay network based on the time slot system, and sets the time slot corresponding to this PVC routing information. It is allocated and registered in the TS registration unit 8, and a time slot for detour on the detour route is reserved and registered in the TS registration unit 8. When a failure occurrence is detected in the monitoring unit 10, the time slot switch unit 9 is controlled so as to switch to the detour time slot registered in the TS registration unit 8, and the frame is detoured and transferred. Since it is not necessary to set two logical paths, that is, a normal logical path and a bypass logical path, there is an advantage that a PVC that can be set between nodes can be effectively used.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a bypass operation according to the embodiment of this invention.

FIG. 3 is an explanatory diagram of a bypass process according to the embodiment of this invention.

FIG. 4 is an explanatory diagram of a detouring procedure according to the embodiment of this invention.

FIG. 5 is an explanatory diagram of a logical path and a physical path.

FIG. 6 is a frame relay frame format.

FIG. 7 is an explanatory diagram of a bypass process of a conventional example.

[Explanation of symbols]

1 ₁ to 1 ₃ nodes 2 ₁ and 2 ₂ terminal device 4 PVC routing unit 5 time slot processing unit 6 routing table 7 logical path switch unit (PSW) 8 TS registration unit 9 time slot switch unit (TSW) 10 monitoring unit

Claims (3)

[Claims] 1. In a TDM transmission-based frame relay network based on a time slot method, permanent virtual connection (PVC) routing information is registered in a routing table and the permanent virtual connection (PVC) is registered.
A frame relay characterized by allocating a time slot corresponding to routing information, reserving a detour time slot in a detour route, and switching to the detour time slot to transfer a frame by detour when a failure occurs Detour method in the net. 2. The time slot for control signal and the time slot for data transfer are reserved in the reservation of the detour time slot.
Detour method in the described frame relay network. 3. Normality of a detour route is performed by monitoring between nodes by looping back a supervisory signal by a control signal time slot, and by detecting a fault occurrence, a supervisory signal by the reserved control signal time slot for detour. 3. The detouring method in the frame relay network according to claim 1, wherein after confirming that the detouring is performed, the frame is detoured by switching to the reserved time slot for data transfer for detouring.