JP2002232509A - Communication unit and deadlock preventing method in re-transmission type communication - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a deadlock from being caused by an overflow of a buffer of a communication unit, in re-transmission type communication. SOLUTION: The communication unit 100 with a re-transmission type communication protocol function adopts a configuration of employing a control PDU(Protocol Data Unit) transmission reception buffer memory 102 and a data PDU transmission reception buffer memory 103 respectively. Thus, even on the occurrence of a buffer overflow of the data PDU transmission reception buffer memory 103, the transmission reception of the control PDU can be attained so as to continue the re-transmission type communication.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication apparatus for performing data communication with a partner communication apparatus using a retransmission type communication protocol, and a deadlock prevention method in the retransmission type communication.

[0002]

2. Description of the Related Art Conventionally, in a retransmission type communication protocol performed between two communication apparatuses, a data PDU (protocol data unit) used by a transmitting side to transmit information to be transmitted, and whether a receiving side has received the data PDU. And a control PDU such as a status PDU used for notifying the transmitting side of this.

In retransmission-type communication, the transmitting side creates one or a plurality of data PUDs for transmitting an SDU (service data unit) received from an upper layer, and stores them in a buffer memory in preparation for retransmission. To send to the receiving side.

On the receiving side, when a data PDU is received and stored in a buffer memory,
When an error or loss of U is found, or when the transmitting side requests retransmission using a control PDU, a status PDU is created and returned to notify the transmitting side of the reception status.

[0005] The transmitting side receives the status PDU sent from the receiving side, stores it in the buffer memory, and confirms the delivery of the data PDU to the receiving side, and releases the stored data PDU. If the transmission to the receiving side cannot be confirmed, the stored data PDU is retransmitted.

[0006] The data PDU retransmission control method includes a GO-B that retransmits all data PDUs that cannot be transmitted after the data PDU.
There are an ACK-N system, a selective repeat system that retransmits only data PDUs that could not be transmitted, and the like. Is stored in the buffer memory.

In such retransmission-type communication, a control PD such as a status PDU is used due to delay, error, congestion, etc. in a network between two communicating devices.
There is a case where U reaches the other party with a delay or does not reach. The delay or non-arrival of the status PDU may delay the release of the data PDU stored in the buffer memory on the transmission side and cause a buffer overflow. When a buffer overflow occurs, not only can a new data PDU not be transmitted because there is no free space in the buffer memory, but also the data PDU and the control PDU that reach the communication device are discarded without being received. .

If the control PDU including the status PDU cannot be received, the data PDU in the buffer memory cannot be released, so that the communication apparatus falls into a deadlock. To solve this problem, parameters such as credit and window size are conventionally introduced (for example, S
A method of preventing buffer overflow by performing flow control based on SCOP Q.2110) has been proposed.

[0009]

However, in such a method using flow control, the processing amount of the entire communication increases by the processing amount for performing flow control, such as processing of new parameters and prediction of data flow. There is a problem.

[0010] Further, since control PDUs such as status PDUs are assumed to be transmitted and received, if a control PDU cannot be received due to a buffer overflow, there is a problem that flow control cannot be performed and deadlock occurs. That is, at present, there is no fundamental solution.

The present invention has been made in view of the above points, and provides a communication apparatus in which deadlock due to a buffer overflow does not occur even if flow control is not performed in retransmission-type communication, and a deadlock prevention method in retransmission-type communication. With the goal.

[0012]

A communication device according to the present invention is a communication device for performing data communication with a partner communication device by using a retransmission type communication protocol, and stores a data PDU used for transmitting and receiving information. 1 and a second storage means for holding at least a status PDU used by the other communication device to notify whether or not the data PDU has been received.

The communication device of the present invention is a communication device for performing data communication with a communication device of the other party by using a retransmission-type communication protocol, and includes a data PDU used for transmitting and receiving information.
First storage means for storing the status PDU used by the other communication device to notify whether or not the data PDU has been received, and transmitting the data PDU to the other communication device. Along with
In preparation for retransmission, the status PDU is stored in the first storage unit, and when the status PDU is transmitted from the partner communication device after the transmission of the data PDU, the status PDU is stored in the second storage unit and then analyzed. If the analysis result confirms the delivery of the data PDU to the partner communication device, the data PDU stored in the first storage unit is released, and the delivery of the data PDU cannot be confirmed. Control means for retransmitting the data PDU stored in the first storage means.

According to the present invention, since the storage means for storing the data PDU and the storage means for storing the control PDU are separately provided, a buffer overflow occurs in the first storage means for storing the data PDU. However, the status PDU that arrives after this is stored in the second storage means without being discarded. As a result, it is possible to continue the retransmission-type communication protocol processing without deadlock.

A deadlock preventing method in retransmission-type communication according to the present invention is a method for preventing deadlock in retransmission-type communication used for a communication device that performs data communication with a partner communication device using a retransmission-type communication protocol. The storage of the data PDU used for transmission and reception and the holding of the status PDU used by at least the other communication device to notify the presence or absence of the reception of the data PDU are separately performed, and the storage of the data PDU to the other communication device is performed. When the status PDU is sent from the partner communication device after transmission, the status PDU is stored separately from the data PDU.

According to the present invention, the control PDU can be received even if an overflow occurs in the storage of the data PDU, so that the retransmission type communication protocol processing can be continued without deadlock. .

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The main point of the present invention is that the storage of data PDU and the storage of control PDU are performed by dedicated storage means, respectively, so that the storage means for storing data PDU has a buffer overflow. Control P
This is to make it possible to receive a DU.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of a communication device according to an embodiment of the present invention. In this figure,
The communication device 100 according to the present embodiment includes a control PDU transmission / reception buffer memory (second storage unit) 102 used for transmission / reception of control PDUs, and a data PDU transmission / reception buffer memory (first storage device) used for data PDU transmission / reception. Storage means) 103 and control PDU transmission / reception buffer memory 10
2 and a retransmission type communication protocol function unit (control means) 104 for controlling the data PDU transmission / reception buffer memory 103. The communication device 100 is connected to a communication device (not shown) of a communication partner via a transmission line 101.

Control PDU transmission / reception buffer memory 102
Is the status PDU sent from the partner communication device.
Is used to store control PDUs such as status PDUs to the partner communication device. Data PDU transmission / reception buffer memory 103
Is used for storing the data PDU transmitted from the partner communication device, and the data PDU is transmitted to the partner communication device.
Used for sending. Retransmission type communication protocol function unit 10
4 has a retransmission type communication protocol function, and controls the control PDU transmission / reception buffer memory 102 and the data PDU transmission / reception buffer memory 103 according to this function.

Next, the operation of the communication apparatus 100 having the above configuration will be described. In order to avoid confusion in the description of the operation, the communication device 100 that first transmitted the data PDU is referred to as a first communication device, and the data PD from the first communication device is referred to as a first communication device.
The communication device 100 that has received U is referred to as a second communication device. When the retransmission-type communication protocol function unit 104 of the first communication device creates one or a plurality of data PDUs from the data to be transmitted, the retransmission-type communication protocol function unit 104 stores the data PDU in the data PDU transmission / reception buffer memory 103 for retransmission.
The data is transmitted to the second communication device via the transmission path 101.

Upon receiving the data PDU transmitted from the first communication device, the second communication device returns a status PDU. Status PD returned from the second communication device
U is received and stored in the control PDU transmission / reception buffer memory 102 of the first communication device. Note that status P
The DU is returned even when the loss of the data PDU is found or when a status PDU return request is received from the first communication device.

The retransmission type communication protocol function unit 104 of the first communication device analyzes the received status PDU, and confirms from the analysis result that the previously transmitted data PDU has been correctly delivered to the second communication device. , Data PDU
The data PDU stored in the transmission / reception buffer memory 103 for retransmission is released. On the other hand, when it is determined from the analysis result of the status PDU that the previously transmitted data PDU was not correctly delivered to the second communication device,
The data PDU stored in the data PDU transmission / reception buffer memory 103 is retransmitted. Also, the status PDU stored in the control PDU transmission / reception buffer memory 102
Control PDUs are released after analysis.

As described above, the communication apparatus 10 of the present embodiment
0, the data PDU is transmitted to the communication device that performs data communication with the opposite communication device using the retransmission-type communication protocol.
Control P such as status PDU regardless of occurrence of buffer overflow of transmission / reception buffer memory 103
The DU is configured to be stored in the control PDU transmission / reception buffer memory 102.

Therefore, even if a buffer overflow occurs in the data PDU transmission / reception buffer memory 103, retransmission-type communication can be continued without falling into a deadlock.

[0026]

As described above, according to the present invention,
It is possible to provide a communication device that does not fall into a deadlock even if a buffer overflow occurs in storing data PDU.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a communication device according to an embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 communication apparatus 101 transmission line 102 control PDU transmission / reception buffer memory 103 data PDU transmission / reception buffer memory 104 retransmission type communication protocol function unit

Claims (3)

[Claims] 1. A communication device for performing data communication with a partner communication device using a retransmission type communication protocol, wherein a first data PDU used for transmitting and receiving information is stored.
And a second storage means for holding at least a status PDU used by the other communication apparatus to notify whether or not the data PDU has been received. 2. A communication device for performing data communication with a partner communication device using a retransmission type communication protocol, wherein a first data PDU used for transmitting and receiving information is stored.
Storage means for holding at least a status PDU used by the other communication device to notify whether or not the data PDU has been received; and transmitting the data PDU to the other communication device and retransmitting the data PDU. And when the status PDU is transmitted from the partner communication device after the transmission of the data PDU, the status PDU is stored in the second storage unit and then analyzed. When the delivery of the data PDU to the partner communication device can be confirmed from the analysis result, the data PDU stored in the first storage unit is released, and the delivery of the data PDU cannot be confirmed. Control means for retransmitting the data PDU stored in the first storage means. 3. A method for preventing deadlock in retransmission-type communication used for a communication device that performs data communication with a partner communication device using a retransmission-type communication protocol, comprising: storing a data PDU used for transmitting and receiving information; At least the status PDU used for notifying the presence / absence of reception of the data PDU by the partner communication device is separately performed, and the status PD is transmitted from the partner communication device after the data PDU is transmitted to the partner communication device.
A method for preventing deadlock in retransmission-type communication, wherein when a U is sent, its status PDU is stored separately from the data PDU.