JPH03175759A - Packet exchange control system - Google Patents

Abstract

PURPOSE:To prevent data from being overlapped and lost even when a belonging packet exchange is changed by the movement of a moving body by adding sequence numbers independent of packet sequence numbers, delivery checking ACK request bits and ACK responses to data(DA) packets. CONSTITUTION:A communication route formed when the moving body 11 moves to a position B consists of a non-packet configuration terminal 1a, a communication control equipment 5a, a radio line 6b, a packet exchange 3b, a packet transmission line 2b, a packet exchange 3d, and a host computer 4. A packet type additional part is the information of two octets following an X, 25 data (DA) packet header. An ACK response request display (A) is information for requesting an ACK response to a communicating terminator after receiving the data(DT) packet of A='1' and one of ACK request bits. On the other hand, an ACK response display (R) is information indicating an ACK response message as a response to an ACK response request and one of ACK request bits.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is directed to data duplication when the packet switching center to which a data terminal device installed in a mobile body belongs changes as the mobile body moves. , relates to a packet switching control method designed to prevent loss.

[Conventional technology]

Figures 5 and 6 are sequence diagrams of conventional packet delivery confirmation and error control shown, for example, on pages 312 to 315 of "Packet Switching Service Interface (PT Edition)" edited by Nippon Telegraph and Telephone Corporation. It is.

That is, FIG. 5 is a diagram showing a packet delivery confirmation sequence, and FIG. 6 is a diagram showing a packet error control (retransmission) sequence. In this case, in the figure, DTE is data terminal equipment.
(Hereinafter, data terminal equipment will be simply referred to as terminal), DC
R is a data circuit termination device (Data CircuitT
Erminal Equipment) CD
It is an abbreviation.

Next, the operation will be explained.

The sequence diagrams in FIGS. 5 and 6 can be viewed as follows. However, since the logical channel number is not important in this operation description, the logical channel number will not be included in the following description.

First, in the delivery confirmation sequence of FIG. 5, as shown in the figure, the reception order number P(
R) is used to notify that up to the data (DT) packet whose transmission order number is CP(几)-1) has been correctly received. Specifically, the DTE sends 8 receivable packets per DT (0.0).
Since II is returned to the DTE, this indicates that the data packet of 1)(S)=Q has reached the destination DTE.

Next, in the error control # (retransmission) sequence in Figure 6, as shown in the figure, the DTE is supposed to monitor the timing of waiting for a response CP (几) to that packet after transmitting a data (DT) packet. , it is possible to deal with abnormalities in the other DTE or loss of packets. Concrete 1'lj, D T E
;AfDT, l, O, DT, 2,0, DT, 3.0
There is no response of 0.1 from the other party DTB to JDT.

This indicates that the other DTE has not received 3 data (DT) packets. For this reason, DTE uses data (
DT) The packet is being retransmitted.

[Problem to be solved by the invention]

Since the conventional packet switching control system is configured as described above, it is assumed that the terminal DTE is fixedly installed at a predetermined location and is not mounted on a moving object such as a train and moved. Therefore, the above terminal DT
When H moves and the packet switching center to which the terminal DTE belongs changes, the sequence number of the packet is initialized and starts from "0", so data (packets) are not transmitted between the terminal and the host computer during communication. There was a problem that duplicates and losses could not be detected.

This invention was made to solve the above-mentioned problems, and even if the packet switching center to which the terminal installed on the mobile body belongs changes due to the movement of the mobile body, the data (packet) The purpose is to obtain a packet control method that can prevent duplication and loss of packets.

[Means to solve the problem]

The packet switching control method according to the present invention includes a sequence number independent of the packet sequence number to prevent data duplication and data loss, an ACK (acknowledge) request bit for delivery confirmation, and an ACK response in a data packet. It was added.

[For production]

The packet switching control method according to the present invention prevents duplication and loss of data (packets) caused by changes in the packet switching station to which a terminal on the mobile body belongs due to the movement of the mobile body, using the sequence number of the packet in the data packet. This is prevented by an independent sequence number and an ACK request bit for delivery confirmation and an ACK response.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, 1a is a non-packet type terminal mounted on a moving object 11, which is, for example, a train equipped with a train radio;
~2C is a packet switching center, which is a packet transmission path between packet switching centers 33 to 3C consisting of packet switching machines and the packet switching center 3d, which are interconnected by an interoffice protocol to perform communication, and 4 is a packet switching center 3d. 5a is a communication control device mounted on the mobile body 11 and connected to the non-packet type terminal 1a; 6a, (3b is a host computer connected to the non-packet type terminal 1a on the mobile body 11) This is a wireless link between the packet switching stations 3a and 3b.Also, A and B indicate points A and B, which are located at different locations.

Further, FIG. 2 is an explanatory diagram of the data packet format of the ACK (acknowledge) response according to the above embodiment of the present invention, and FIG. 3 is an illustration of a sequence example of data (packet) duplication and loss prevention according to the above embodiment of the present invention. The explanatory diagram, FIG. 4, is an explanatory diagram of the format of a data packet according to the above embodiment of the present invention.

Next, the operation will be explained. When communication is performed between the non-packet type terminal 1a mounted on the mobile body 11 and the host computer 4, the communication path when the mobile body 11 is at point A is the non-packet type terminal 1a+communication control device 5a+wireless. Line 6a + Packet switching center 3a + Packet transmission line 2C
t packet switching center 3d and host computer 4.

On the other hand, when the mobile object 11 moves to point B, the communication route is: non-packet type terminal 1a + communication control device 5a + wireless line 6b, and packet switching center 3b.

This includes a packet transmission path 2b, a packet switching center 3d, and a host computer 4.

An example of the sequence for preventing duplication and loss of data (packets) when the non-packet type terminal 1a changes its affiliated packet switching station due to movement is shown in FIG. 3 mentioned above.

First, the packet format according to the above embodiment of the present invention shown in FIGS. 2 and 3 will be explained. Figure 2.

As shown in FIG. 3, the additional portion of the above embodiment of the present invention is information in the last two octets of the X, 25 data (DT) packet φ header. In the figure, GFI is a general format identifier, LCGN is a logical channel group number, LCN is a logical channel number, p (s) is a transmission sequence number, and P (R) is a reception sequence number.

The above additional portion will be explained below.

(IIAcK response request display (A) This is information that requests the communication partner to make an ACK response after receiving a data (DT) packet of A-'"1". This is one of the bits requested in 80.

(2) A CK response display (几) Information indicating that this is an ACK response message as a response to an ACK response request.9J, 1 of the ACK request bit.
It is one. In addition, the ACK response message is displayed in the sequence shown in Figure 3. - ACK response display R = "l" - Sequence number (SEQ) is the confirmed value + 11
This is the sequence number to be received next.

(3) Sequence number (SEQ) A number used to prevent data duplication and loss in the above embodiment of the present invention.
7”'2, then when it becomes 127′ it becomes 0”
This is the sequence number to return to. This sequence number C
3EQ) is independent of the packet sequence number.

Next, the above sequence example will be explained with reference to FIG.

The numbers in the figure are sequence numbers according to the above embodiment of the invention. This is an example of data communication from the host computer 4 to the communication control device 5a of the mobile unit 11 and the non-packet type terminal 1a. (1) The host computer 4 sends data 1, 2, etc.
, and an ACK response request is made with the sixth data.

(2) Upon receiving the data 6 of the A-- CK response request pair, the communication control device 5a sends the data to the non-packet type terminal 1a and returns a response message to the host computer 4 at the same time.

(3) The host computer 4 that received the A CK response message transmits data in order starting from data 7.

(4) At the ninth data, when the packet switching center changes from the packet switching center 3a to the packet switching center 3b due to the movement of the mobile unit 11, data 9 is lost.

(5) The host computer 4 transmits data 9 to data 12. An ACK response request is made using data 12.

(6) Since the communication control device 5a that received the data 12 requesting A CK has not received the data 9,
K response messages are not returned.

- Discard normally received data 7 to 12.

(7) Since the ACK response message is not returned, the host computer 4 retransmits the data 7.

In this way, data can be communicated without duplication or loss of data even if the affiliated packet switching center changes due to the movement of the mobile unit 11, using the sequence number and the ACK response request.

Note that in the above embodiment, the host computer 4 and the mobile unit 11
A communication control device 5a installed in a non-packet type terminal 1
Although data communication to a is shown, the non-packet type terminal 1a
Communication from the computer to the host computer 4 is also possible. Further, in the above embodiments, the case of train radio has been described, but the present invention can also be applied to other moving bodies such as ships and automobiles that exchange packets using mobile radio lines.

〔Effect of the invention〕

As described above, according to the present invention, an independent sequence number, an ACK request bit for delivery confirmation, and an ACK response are added to a data (DT) packet, so that This has the effect of preventing data duplication and loss even if the affiliated packet switching center changes.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a packet switching system according to an embodiment of the present invention, Fig. 2 is an explanatory diagram of the ACK response packet (message) format, and Fig. 3 is an example of a sequence for preventing duplication and loss of data (packets). FIG. 94 is an explanatory diagram of the data packet format according to the above embodiment, FIG. 5 is an explanatory diagram of the conventional packet delivery confirmation sequence, and FIG. 6 is an explanatory diagram of the conventional packet error control (retransmission) sequence. It is a diagram. 1a is a non-packet type terminal, 38 to 3d are packet switching stations, 4 is a host computer, 5a is a communication control device, 11 is a mobile unit, A and R are ACK request bits, and SBQ is a sequence number. . Agent Masuo Oiwa

Claims (1)

[Claims] In a packet switching control method of a system that performs communication using a packet switching method between a data terminal device mounted on a mobile body and a plurality of packet switching stations, the packet switching station to which the data terminal device belongs due to the movement of the mobile body A packet switching control method characterized by adding a sequence number independent of the packet sequence number for data duplication and loss prevention when data changes, an ACK request bit for delivery confirmation, and an ACK response to the data packet. .