JPH0614056A - Plural path type data transfer system - Google Patents

Abstract

PURPOSE:To obtain the data transfer method with high reliability without interruption of communication in which bypass processing is not required even on the occurrence of a fault. CONSTITUTION:A caller exchange node 3a manages plural paths 6a-6d to a called exchange node 3d and selects paths. Plural available paths 6a, 6b are selected and allocated among plural fixed paths decided in advance at setup, data 8a, 8b received from a subscriber are stored in a frame with a path identifier and sent to all the allocated paths simultaneously. The called node 3d uses the data 8a having no error arrived at first among same data received from each path as valid data 7b and aborts the same data 8b reached succeedingly as invalid data. Thus, the network is built up in which communication is not interrupted even on the occurrence of a fault, the load for re- transmission processing is much reduced and the high reliability is always maintained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data transfer system from a source switching node to a destination switching node in a packet switching communication network for storing data in a frame for transfer.

[0002]

2. Description of the Related Art Conventionally, as a data transfer method in a packet type communication network, for example, JP-A-3-429 is used.
As shown in Japanese Patent Laid-Open No. 40, there is a method of transferring data using a plurality of routes, and the configuration thereof is shown in FIG. In this figure, 10a is an originating subscriber, 10b is an incoming subscriber,
12a to 12d are switching nodes, of which 12a is a source switching node and 12d is a destination switching node. Also, 1
Reference numerals 5a and 15b denote fixed routes from the originating switching node to the destination switching node, which are set at the time of call setup, and 17a and 17b are data copied from the calling subscriber and sent to the respective fixed routes.

Next, the operation will be described. First, a plurality of routes from the originating switching node to the destination switching node are set during call setup (15a, 15b). The source switching node copies the transmission data, adds a sequence number of independent data for each call and an identifier of a logical channel corresponding to each route, and sends the data to each route (17a, 17b).
In order to identify the same data received from different routes, the destination switching node refers to the sequence number given to the data and removes the duplicated data. In order to detect the duplicated data, the sequence number of the received data and the sequence number expected to be received next by the destination switching node (2 in FIG. 5).
0), the difference is calculated, and this difference is the predetermined loss detection area 1
If it is greater than or equal to 8 (range 19 in FIG. 5), it is regarded as overlapping, and if it is smaller (range 18 in FIG. 5), it is regarded as new data. Also, when changing the route during communication,
After setting a new route, send data to that route,
When the destination switching node confirms the duplication of data, the destination switching node notifies the originating switching node to release the route that has been used so far.

[0004]

As described above, the conventional data transfer method does not consider the state of the route when setting a plurality of routes at the time of call setup, and includes the route in which congestion occurs. There was a risk of setting it in. This not only promotes congestion, but because the data passing through the congested route has a larger delay than the data passing through the normal route, there is a high possibility that it will be discarded as duplicate data at the destination switching node. There was a problem that unnecessary traffic existed in the network. In addition, it is premised that order control is performed in the detection of duplicate data in the destination node, and even if the sequence number is lost due to data loss, etc., if it is data included in the loss detection area, it is regarded as new data and expected. There is a problem that the number of buffers required becomes very large because the destination switching node holds the data until the data of the sequence number is received. Furthermore, when the route used during communication becomes congested, it is necessary to promptly regulate the data transmission to the congestion route, but in the conventional route change method, the originating switching node stops the data transmission to the congestion route. Since the destination switching node notifies the originating switching node that it has detected the duplication of data, it takes time to regulate the data inflow to the congestion route, and the risk of congestion spreading to the network. It was very good.

The present invention was conceived in order to solve the above problems, and in order to send the same data to a plurality of normal paths at the same time while considering the status of the sending path in the originating switching node, It is highly possible that data with little delay and error-free will reach the destination node.
The destination switching node can minimize the number of held buffers by reducing the number of data to be held as much as possible, and when a failure or congestion occurs on the route in use, immediately add a normal route and at the same time fail. And a data transfer method capable of stopping data transmission to a route where congestion has occurred.

[0006]

In the data transfer method according to the first aspect of the present invention, a source switching node sets a plurality of routes to a destination switching node in a route table in advance and manages the route states of the plurality of routes. When selecting an available route, instead of assigning only one route to be selected by the originating switching node during call setup, a normal route with no fault or congestion in the route set in the route table Is selected and assigned in an arbitrary number, and the data received from the subscriber is simultaneously transmitted to each selected route, and has the following elements. (A) a plurality of routes from the source switching node to the destination switching node and a route table that stores the route status of each route; and (b) a plurality of routes from the routes stored in the route table, based on the route status. Sending means for selecting a route and sending the same data to the selected route; (c) Validating the arrival of any one of a plurality of the same data sent by the sending means and invalidating the other. Incoming means.

In the data transfer method according to the second aspect of the present invention, each relay node detects a data error, but discards this as invalid data without performing retransmission control for erroneous data. The error-free data that arrives first among the same data received from the device is valid data, and the same data that arrives thereafter are discarded as invalid data and have the following elements. (A) Sending means for selecting a plurality of routes from the source switching node to the destination switching node and sending the same data to the plurality of routes, (b) When the data sent by the sending means is normally received. Relay means for transferring data and invalidating the data if not normally received, (c) receiving the data relayed by the relay means, requesting a retransmission when the next expected data does not arrive, and Incoming means to invalidate the data of.

[0008]

According to the first aspect of the invention, the sending means transfers one data received from the subscriber to a different route preset in the route table, so that even if one route becomes a failure, it is transmitted from another route. Since the data can arrive at the destination switching node, there is no need to hold the data or switch the route when there is a momentary disconnection or failure of the line, and there is no interruption of communication. This is particularly effective for a routing method in which the route to the destination switching node is managed as a fixed route at the originating switching node and the data of one call passes through the same route. Also,
Since there is no need to retransmit data even if data is erroneous or lost through one route, waste of retransmission is eliminated. Further, the sending means can prevent congestion by referring to the route status in the route table and selecting a normal route at the time of call setup.

In the second aspect of the invention, since the relay means in each relay node discards invalid data having an error, network resources can be effectively used without the trouble of retransmission. Further, in order to identify that the sending means is the same data, in the originating switching node, for example, a cyclic sequence number is added to the data as an independent number for each call, and the receiving means is the sequence number in the destination switching node. Refer to. Further, in the destination node, by referring to the sequence number, if it is determined that valid data without error expected to arrive next does not arrive,
That is, if a missing sequence number or a time-out occurs, a request for retransmission is immediately sent to the originating switching node, and subsequent data is discarded until the data expected to arrive is received. In this way, until the receiving means receives the data of the sequence number expected by the terminating switching node, even if the data of the subsequent sequence number arrives first, it is discarded so that the buffer of the buffer held by the receiving switching node is discarded. The amount is small.

[0010]

EXAMPLES Example 1. FIG. 1 is an example of a packet switching network to which the present invention is applied. In the routing system in this network, a route to a destination switching node is managed by a plurality of predetermined fixed routes as a route to a destination switching node to manage its failure and congestion state. However, it is a routing method in which a route to the destination switching node is assigned at the time of call setup. A description will be given below according to this figure. In the figure, 3a to 3d are switching nodes A to D, respectively, of which 3a is a source switching node and 3d is a destination switching node. 4a to 4e are trunk lines, and the numbers attached to both ends of each trunk line are the trunk line numbers viewed from the switching node terminating the trunk line. The originating / switching node A manages information on each fixed route to the destination switching node as a fixed route table together with a route identifier and a route state as shown in FIG. 2, and sets a call from a plurality of predetermined fixed routes. At any time, an arbitrary number of, for example, the upper two fixed routes P and Q that can be used (without a fault) when the routes in the fixed route table are arranged in the priority order are assigned. 1 sent from calling subscriber 1a
One packet 7a is stored in the frame together with the route identifier at the originating switching node A, and is simultaneously sent to each fixed route assigned (8b, 8c).

Each switching node 3b, 3 for relaying a frame
In c, it is checked whether the received frames 8b and 8c have an error. This error detection is performed by FCS (frame check sequence) as used in the HDLC procedure, for example.
by. If an error is detected here, the erroneous frame is discarded.

At the destination switching node 3d, the first error-free frame (received from the fixed route P in FIG. 2) of the frames storing the same packet received through each fixed route is set as a valid frame, and thereafter The arriving frame storing the same packet (received from the fixed route Q) is discarded as an invalid frame. Here, in order to identify that the packets in the frame are the same, a cyclic sequence number used in the originating switching node, for example, in the HDLC procedure is added to the frame as an independent number for each call. If the destination node determines that a valid valid frame with no error expected to arrive next due to missing sequence numbers does not arrive by referring to the sequence numbers, the sequence numbers are missed due to, for example, frame loss. When occurs, a request for retransmission is made to the originating switching node, and subsequent received frames are discarded until a frame expected to arrive is received.

This situation is shown in the sequence diagram of FIG. In this example, the destination switching node determines that a valid frame expected to arrive next does not arrive when a sequence number that is 2 larger than the sequence number expected to arrive is received. That is, when the sequence number expected to arrive is 1, the retransmission request is sent to the originating switching node because the frame with the sequence number 3 is received. This resend request stores a sequence number to be resent, such as the method used in HDLC,
The originating switching node that receives this retransmits the sequence number again. As described above, the packets in the valid frame received by the destination switching node 3d are sequentially transmitted to the destination subscriber 1b, whereby data is transferred from the source subscriber to the destination subscriber.

When a failure occurs in a certain route, for example, when the fixed path Q becomes unusable due to a failure in the trunk line 4d, a usable fixed path that is not assigned at the time of call setup is set. If it exists in a plurality of predetermined fixed routes to the destination switching node (in the above example, FIG.
S), the fixed route is added to the corresponding call and assigned,
The frame transmission is stopped for the route (Q in FIG. 2) that cannot be used. The route state of each route is written corresponding to each route as shown in FIG. In this case, 0 can be used and 1 cannot be used as the route state. The number of fixed routes that can be additionally allocated is, for example, in the fixed route table in which each route is arranged in the priority order,
Allocate as many fixed routes as possible due to a failure.

As described above, when there is a usable route that is not assigned at the time of call setup, if there is a disabled route among the already assigned routes, the usable route for the corresponding call is set. It is possible to additionally allocate and stop sending the data to the route that cannot be used.

As described above, according to this embodiment, in the communication network in which each switching node in the network stores the data from the subscriber in a frame and transfers the data from the source switching node to the destination switching node, Manages the state of the route to the destination switching node as a plurality of predetermined fixed routes, and at the time of call setup, an arbitrary number of usable routes without failure or congestion among the plurality of fixed routes to the destination switching node The same data is sent to all the assigned routes at the time of data transfer, and only the first error-free data of the same data that has arrived at the destination switching node is validated, and it arrives after that. It is characterized in that the same data is invalidated for communication.

When an error or loss occurs in the data being transferred between the switching nodes, the corresponding data is invalidated and is not retransmitted, and the data expected to arrive next at the destination switching node does not arrive. If it is determined that the data is to be retransmitted, a request for resending is made to the originating switching node, and subsequent data is invalidated until data expected to arrive arrives.

Further, if there is a usable route which is not assigned at the time of call setup among the fixed routes predetermined by the originating / switching node, the unassigned route is added to the corresponding call and assigned. It is characterized by being able to do it.

As described above, when there is a normal route that has not been assigned at the time of call setup, the route can be added and assigned, so that a fault or congestion occurs in the route in use and Even if a route becomes unusable, another route can be added and a route with a failure or congestion can be deleted to perform highly reliable data transfer using multiple normal routes as at the time of call setup. . In other words, if there is a failure in the route you are using, add another available route,
At the same time, by deleting the failed route, it is possible to maintain the same highly reliable network as at the time of call setup.

Particularly, this embodiment is different from Japanese Patent Application Laid-Open No. 3-42940 described in the prior art in the following points. (A) Conventionally, a logical path (fixed route) to the destination switching node
While this is set at the time of call setup, in the present embodiment, this is set in advance and assigned from among them at the time of call setup. (B) The present embodiment is adapted to the mid-transmission system in which the state of a fixed route is managed by the originating / switching node, and the route state is taken into consideration during allocation. (C) Addition and deletion of the route can be performed at the same time when the route is changed by the above (a) and (b). (D) In this embodiment, the destination switching node does not hold data for order control, but performs ordering by discarding and retransmitting.

Example 2. Although a plurality of routes are assigned to each call in the first embodiment, a plurality of routes may be assigned to each connection in the case of a multi-connection call in which one call includes a plurality of connections.

[0022]

As described above, according to the first aspect of the present invention, in order to send one data from the calling subscriber simultaneously to a plurality of normal different routes in the calling switching node, the relay line is provided. Even if a momentary power interruption or failure occurs, data can be expected to arrive at the destination node from another route, so there is no need to hold the data or make a detour to another route and interrupt the communication. It is possible to build a highly reliable network.

According to the second aspect of the invention, the switching node for relaying data does not need to be retransmitted for data error or loss, and invalid data is removed from the network. The load of can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing a packet switching network in an embodiment of the present invention.

FIG. 2 is a diagram showing a fixed route table in a source switching node according to an embodiment of the present invention.

FIG. 3 is a diagram illustrating a method of determining valid data in a destination exchange node according to an embodiment of the present invention.

FIG. 4 is a diagram showing a packet switching network according to a conventional data transfer method.

FIG. 5 is a diagram illustrating data duplication detecting means in a conventional data transfer method.

[Explanation of symbols]

1a, 1b Subscribers 3a-3d Switching nodes 6a-6d Predetermined fixed routes to destination switching nodes 6a, 6b Routes 7a, 7b assigned at call setup Packets from subscribers 8a, 8b Route identifiers are attached Frame

Claims (2)

[Claims] 1. A multi-route data transfer system having the following elements: (a) a route table storing a plurality of routes from a source switching node to a destination switching node and a route state of each route; (b) the route table Sending means for selecting a plurality of paths from the stored paths based on the path status and sending the same data to the selected paths, (c) Of the plurality of the same data sent by the sending means, Incoming means that validates the arrival of any one data and invalidates the other. 2. A multi-path data transfer system having the following elements: (a) sending means for selecting a plurality of paths from a source switching node to a destination switching node and sending the same data to the plurality of paths; ) A relay means for transferring the data sent by the sending means when the data is normally received, and invalidating the data when the data is not normally received, (c) receiving the data relayed by the relay means,
When the next expected data does not arrive, a receiving means for making a retransmission request and invalidating other data.