JPH0528072A - Computer system - Google Patents

Abstract

PURPOSE:To eliminate unnecessary retransmission and delay of fault detection by setting a proper initial value of retransmission time-out in a network. CONSTITUTION:An acknowledge ACK to the packet transmitted from a packet transmission part 1 is received by a packet reception part 2, and the value obtained by a round trip time RTT measuring part 6 is registered in a retransmission time-out table 8 together with the host computer of the other party of transmission by a retransmission time-out register part 9. When retrieving a retransmission time-out retrieval part 7 at the time of transmission to detect, that the host computer name of the other party of transmission is registered, the packet transmission part 1 sets the value of this table 8 to a retransmission time as retransmission time-out regardless of the connection. Thus, proper retransmission time-out is set, and unnecesary retransmission is prevented to reduce the network load and to quickly detect error.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for management of retransmission timeout during data communication of a plurality of computers connected to each other on a network. The present invention relates to a computer system capable of reducing unnecessary retransmission and failure detection delay in data communication.

[0002]

2. Description of the Related Art Conventionally, in the case of data communication that guarantees reliability, since the information about the round trip time is not held, the retransmission timer is initialized for each connection.

[0003]

Normally, in data communication between computers, since no information about the round trip time with the partner host computer is held, any preset value is used as an initial value. Was used. When this initial value is longer than the actual round trip time, it takes a long time to detect the loss of the transmission data, and when it is smaller, useless retransmission is performed. Further, since the initial value is set for each connection, network congestion and detection time waste often occur. Therefore, it has been a problem to determine an appropriate timer value as an initial value.

The present invention solves such a problem, and it is an object of the present invention to provide a system in which an appropriate initial value of retransmission timeout in a network is set and unnecessary delays and delays in fault detection are reduced. To aim.

[0005]

According to the present invention, a plurality of computers including a host computer are connected via a network, and each of the host computers has a retransmission buffer for holding transmission data for retransmission and a timeout value. A timer for setting a packet, a packet transmission unit for transmitting a transmission packet after storing it in the retransmission buffer, and a communication unit for transmitting and receiving a packet via the network,
In a computer system including a packet receiving unit that receives an acknowledgment (ACK) from a partner host computer, a resend timeout table that stores the name of the partner host computer and a resend timeout value with the host computer is provided. And a RTT that measures a round trip time (RTT) from an acknowledgment (ACK) to the transmitted segment
Maximum round trip time (RT) between the retransmission timer setting unit that sets the retransmission timer value from the measurement unit and the value of the round trip time (RTT) or the value of the retransmission timeout table, and the current communication partner host computer.
T) a retransmission timeout registration unit that registers a value as a retransmission timeout value in the retransmission timeout table, and a retransmission timeout search unit that retrieves the retransmission timeout value from the retransmission timeout table using the communication partner host computer name as a key. Characterize.

[0006]

When the positive response (hereinafter referred to as ACK) to the packet transmitted to the partner host computer is received, the round trip time (RTT) is measured according to the ACK, and the round trip time (RTT) and the name of the partner host computer with which the communication is performed are obtained. Highest RT with that host computer
The T value and the T value are registered as a retransmission timeout in the retransmission timeout table. Next time you send a packet, search the resend timeout table from the resend timeout table using the name of the host computer you are communicating with as a key, and if the host computer you are trying to send is found to be registered, the retrieved value will determine which connection Regardless of whether or not, the retransmission timer is set as the retransmission timeout.

With this, it is possible to set an appropriate initial value of the retransmission timeout without calculating the retransmission timeout for each connection, reduce unnecessary retransmission, and reduce network addition. It is possible to reduce wasteful time on the transmitting side.

[0008]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the embodiment of the present invention.

In the embodiment of the present invention, the host computer 10 is used.
A plurality of computers including the above are connected via the network 11, and a retransmission buffer (not shown) for holding transmission data for retransmission and a timer for setting a timeout value are stored in each host computer 10, and the transmission packet is stored in the retransmission buffer. Packet transmitting unit 1 for transmitting after the transmission, and communication unit 3 for transmitting and receiving packets via the network 11.
And a packet receiving unit 2 for receiving an ACK from the partner host computer, and further, as a feature of the present invention,
A retransmission timeout table 8 for storing the name of the partner host computer and a retransmission timeout value with the host computer is provided, and a retransmission timer activation unit 4 for activating a timer for retransmission timeout at the time of packet transmission,
The RTT measurement unit 6 that measures the round trip time (RTT) from the ACK for the transmitted segment and the retransmission timer setting unit 5 that sets the retransmission timer value from the value of the round trip time (RTT) or the value of the retransmission timeout table 8. And a retransmission time-out registration unit 9 for registering the maximum round trip time (RTT) value with the current communication partner host computer as a retransmission time-out value in the retransmission time-out table 8, and a retransmission time-out value using the communication partner host computer name as a key. A retransmission timeout search unit 7 that searches the retransmission timeout table 8 is provided.

Next, the operation of the embodiment of the present invention thus constructed will be described. Here, when a computer transmits a packet to a host computer 10, it is assumed that the computer has a packet retransmission function in order to guarantee the transmission data, and when communicating with the host computer 10, the retransmission timeout in the table And an example of registering the retransmission timeout in the table based on actual measurement.

When the computer transmits a packet, the packet transmission unit 1 stores the data in a retransmission buffer (not shown),
The retransmission timeout search unit 7 is notified of the destination host computer of the packet.

The retransmission timeout search unit 7 searches the retransmission timeout table 8 using the delivered destination host computer as a key. If it is already registered, the retransmission timeout for the host computer is obtained from the information in the retransmission timeout table 8 and the retransmission timer setting unit 5 is notified of the value.

The retransmission timer setting unit 5 sets the initial value of the timer value to the value given by the retransmission timeout search unit 7 and calls the retransmission timer starting unit 4.

As a result of the search by the retransmission timeout search unit 7, if it is not registered in the retransmission timeout table, the set initial value is set by the retransmission timer setting unit 5, and the retransmission timer is activated.

The transmission packet is transmitted to the network 11 by the communication unit 3. When the packet receiving unit 2 receives the ACK for this packet, the RTT measuring unit 6 measures the RTT from the transmission of the segment to the return of the ACK for the segment.

When the partner host computer is not registered in the retransmission timeout table 8, the RTT is unconditionally set.
The RTT obtained by the measuring unit 6 is registered in the retransmission timeout table 8. If it has already been registered, the retransmission timeout registration unit 9 updates the retransmission timeout table 8 only when the value measured by the RTT measurement unit 6 is larger than the registered retransmission timeout.

FIG. 2 is a diagram showing the contents of the retransmission timeout table. This table is searched using the host computer as a key. For registration, the measured RTT value is larger than that when the RTT with a host computer not registered in this table is measured, and the measured RTT value is larger than the already registered retransmission timeout. This is a case where it is used as a new retransmission timeout.

The retransmission timeout is managed by the above method.

[0019]

As described above, according to the present invention, the retransmission timeout for each connection is not calculated,
It is possible to set an appropriate initial value of retransmission timeout, reduce unnecessary retransmission, reduce network load, and further reduce unnecessary time on the transmission side.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing the contents of a retransmission timeout table in the embodiment of the present invention.

[Explanation of symbols]

 1 packet transmission unit 2 packet reception unit 3 communication unit 4 retransmission timer activation unit 5 retransmission timer setting unit 6 RTT measurement unit 7 retransmission timeout search unit 8 retransmission timeout table 9 retransmission timeout registration unit 10 host computer 11 network

Claims (1)

Claim: What is claimed is: 1. A plurality of computers including a host computer are connected via a network, and a retransmission buffer holding transmission data for retransmission and a timeout value are set for each of the host computers. Timer, a packet transmission unit that transmits a transmission packet after storing it in the retransmission buffer, a communication unit that transmits and receives a packet via the network, and a packet reception unit that receives an acknowledgment (ACK) from the partner host computer. In a computer system equipped with, a re-transmission timer table that stores the name of the other host computer and the re-transmission timeout value with that host computer, and re-transmission timer starting unit that activates the timer for re-transmission timeout during packet transmission And sent Segume RTT measurement unit that measures the round trip time (RTT) from the positive response (ACK) to the packet and the value of the round trip time (RTT), or the retransmission timer setting unit that sets the retransmission timer value from the value of the retransmission timeout table. And the highest round with the current host computer
A retransmission time-out registration unit that registers a trip time (RTT) value as a retransmission time-out value in the retransmission time-out table, and a retransmission time-out search unit that searches for a retransmission time-out value from the retransmission time-out table using the communication destination host computer name as a key. A computer system characterized by that.