JPS649784B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a packet assembly and disassembly apparatus for connecting non-packet terminals to a packet switching network.

One recent data notification method is to divide data into units called packets and transmit them. That is, data to be sent (hereinafter referred to as text) is divided into pieces of a certain length, and a packet header containing an address indicating the receiving device is added to each piece of data, resulting in a packet. Terminals developed for packet-switched networks have the ability to create packets from the data they want to send. Such terminals are called packet terminals. On the other hand, terminals that have been developed in the past are called non-packet terminals because they do not have the function of creating packets. Such terminals are connected to the packet switching network via packet assembly and disassembly equipment. This packet assembling and disassembling device divides a message input from a non-packet terminal into 256 bytes, adds a packet header to each, assembles a packet, sends this packet to a switching network, and also processes a packet received from a packet switching network. Of these,
The packet header is removed, the message is changed to a normal message for non-packet terminals, and this is sent to the packet terminal.

Messages sent from non-packet terminals include text, synchronization establishment code, transparent mode code, transmission control code, block check sequence code, and
A PAD character code (hereinafter referred to as a non-packet message control code) is added. When transmitted to a destination terminal through a packet-switched network, the synchronization establishment code, block check sequence code, and PAD character code are absorbed in the network, but the transparent mode code and transmission control code are transmitted along with the text to the packet establishment/disassembly device. adds a packet header to the packet and sends it to the other party's terminal.
The maximum permissible packet message length within the network (not including the packet header) is 256 bytes, so if the text length is very close to 256 bytes, the packet message length will be reduced to 256 bytes due to the addition of the transparent mode code and transmission control code. As described above, the message is divided into two packet messages and transmitted. This leads to an increase in the number of packet messages, which is a problem in a public packet switching network that charges by the number of packet messages, resulting in an increase in usage fees.

It is an object of the present invention to eliminate the above-mentioned conventional problems, and to provide a packet assembly/disassembly device necessary for connecting a non-packet terminal to a packet switching network with transparent mode codes and transmission control. Deletion or insertion of codes, and the contents of the transparent mode code to be deleted or inserted (identification that all or part of the text is transparent) and the contents of the transmission control code (identification of the start and end codes of the text) A function is provided to insert or delete a message length control header that covers data in a compressed form, and has the effect of preventing an increase in the number of packet messages.

In FIG. 1, the packet assembly and disassembly device 1 is
It is connected to a non-packet terminal and a packet switching network (none of which are shown) via interfaces 3A and 3B, respectively. Interface 3A
Non-packet messages imported from buffer 5
The data is stored in the register 7, taken out one byte at a time, and stored in the register 7. At this time, the interface 3A notifies the control section 30 of the reception of the non-packet message. The 1-byte data in register 7 is sent to BCS decoder 9 and control code decoder 11.
When the decoding result is 1, it is stored in flip-flops 13 and 15. When one byte in register 7 is text, the decoding result is stored in register 16 and gate 17
are opened and sequentially stored in predetermined areas of the buffer 21. When one message is decoded as described above, the message length control header generation circuit 19 creates message length control headers H1 and H2 of 1 byte each according to the contents of the registers 13 and 15 at that time, and sends them to the buffer. 21 in the first and second byte positions. In the buffer 21, out of the non-packet messages stored in the buffer 5, non-packet message control codes are compressed into headers H1 and H2, and a message with text added thereto is stored. This compressed message is from Line Tough Ace 3B.
, where a packet header is added,
Sent to the packet switching network.

The operation will be explained in more detail below with reference to FIG.

The procedure when the packet assembly/disassembly device transmits to a non-packet terminal is a basic procedure.

Now, consider the case where the message is shown at 20 in Figure 2a. This telegram 20 is PAD character code PAD
1 (1 byte), synchronization establishment code SYN (3 bytes),
Code indicating the start of text STX (1 byte), text, code ETX (1 byte) indicating the end of text, block check sequence code BCS1,
BCS2 (total 2 bytes), PAD character code
Consists of PAD2. This telegram is taken out one byte at a time in register 7 and decoded by decoders 9 and 11. When the PAD character code PAD1 and the synchronization establishment code SYN are stored in the register 7, the decoders 9 and 11 output 0, and the gate 17 remains closed, and these codes are transferred from the register 7 to the buffer 21. It will stop being deleted without being deleted. When the code STX is stored in the register 7 and decoded by the control code decoder 11, the STX decoding section in this decoder 11
It outputs 1 and sets flip-flop 15A. Next, when one byte of the text is stored in the register 7, the text decoding section of the control code decoder 11 outputs 1 and stores 1 in the corresponding register 16. One output from the register 16 turns on the gate 17 and is stored in a predetermined position in the buffer 21 under the control of the control section 30. Thereafter, all text portions are transferred from the buffer 5 to the buffer 21 in the same manner. Thereafter, when the code ETX indicating the end of the text is stored in the register 7, the ETX decoding section of the decoder 11 sets the flip-flop 15C. Then the next block check sequence code BCS
When 1 is stored in register 7, BCS decoder 9 takes it in. Next, when code BCS2 is input to register 7, the BCS decoder 9 stores it in register 7.
1 and the newly fetched BCS2, it is determined whether these codes BCS1 and BCS are normal or not, and if they are normal, the flip-flop 13 is set. next
When the PAD character code PAD2 is stored in register 7, this code is simply deleted. As a result, only the text part of the message in buffer 5 is stored in buffer 21, and flip-flop 1 is stored.
Of the flip-flops 3 and 15, flip-flops 15A and 15C are set, and flip-flops 15B and 15D remain reset. The header generation circuit is a flip-flop 15A
In response to output 1 of , the first bit of header H1 is set to 1 to indicate that there is text in this telegram, and the first bit of header H1 is set to 1 to indicate that this STX code is present. 5.6th
Set bit to “00”. Also, flip-flop 1
In response to the 1 output of 3, the second bit of header H1 is set to 1 to indicate that this text is normal. Furthermore, since the flip-flop 15B is 0, the third and fourth bits of the header H1 are set to "00" to indicate that this message is not in the transparent mode. Furthermore, flip-flop 15C
1 output of header H2 to indicate that this telegram has an ETX code.
Set the bit to “00”. In this way, the circuit 19
Headers H1 and H2 are created and stored in the first and second byte positions of the buffer 21. As a result, although the original message 20 had a 9-byte non-packet message transmission control code in addition to the text, the buffer 21 compresses this 9-byte control code into 2-byte information.

Next, consider the case of the message 21 shown in FIG. 2b. This telegram 21 is similar to the telegram 20 in Figure 2a.
This message differs from the message shown in FIG. 2a in that it has a code ETB indicating the end of the transmission block instead of the ETX code.
Therefore, when this telegram 21 is decoded, the flip-flop 15C is not set, but the ETB code decoding section of the decoder 11 outputs 1 when the ETB code is stored in the register 7, and the flip-flop 15D is set. Set. As a result, flip-flops 15A and 15D of the flip-flops 15 are set. The header generation circuit 19 includes flip-flops 15A, 15
In response to B, 13, as in Fig. 2a,
The 1st to 6th bits of header H1 are determined, and in response to the 1 output of flip-flop 15D, the 1st and 2nd bits of header H2 are set to "01" to indicate that this telegram has an ETB code. .

Next, consider the case of the message 22 in FIG. 2c. This telegram 22 has the symbol STX of the telegram 21 in FIG.
A symbol in front of ETB indicating that it is in transparent mode
It differs from the message 21 in FIG. 2b in that it has a DLE.
Therefore, when this first DLE code is stored in register 7, decoder 11 stores the DLE code in register 7.
The code decoder section outputs 1 and flip-flop 15B is set. Therefore, when this telegram 22 is decoded, the flip-flop 15
Among them, flip-flops 15A, 15B, 15D
is set. The header generation circuit responds to the outputs of the flip-flops 15A, 15D, and 13 to generate the first and second outputs of the header H1, as in the case of FIG. 2b.
The first and second bits of the header H2 are determined, and in response to the output of the flip-flop 15B, the fifth and sixth bits of the header H1 are set to "10", and this message has the transparent mode code DLE. Show that. Furthermore, to indicate that the message is in transparent mode, "01" is set in the third and fourth bits of header H1.

As described above, the header generation circuit 19 can form the message length control headers H1 and H2 in response to the outputs of the decoders 9 and 11. This allows the original non-packet message control code to be compressed.

On the other hand, a packet message having such compressed headers H1 and H2 is sent from a packet switching network.
When the packet assembly/disassembly device 1 receives the message from the interface 3B, the packet header is removed at the interface 3B, and the remaining message, that is, the message consisting of message length control headers H1, H2 and text, is stored in the buffer 21. Furthermore, this notifies the control unit 30 that the packet message has been received. Of the compressed packet messages in this buffer 21, headers H1 and H
2 is input to the control code generation circuit 23 and decoded. The circuit 23 decodes these headers H1 and H2 and determines what kind of code is required.
It determines by looking at each bit position of 1 and H2, generates its code, and also generates the PAD character code PAD.
1, PAD2, generate synchronization establishment code SYN.
At the same time, the decoding results of the headers H1 and H2 are transmitted to the control section 30. Control section 3
0 determines the order of the codes to be transmitted and the position in the buffer 5 where they are to be stored based on the decoding result inputted by the generation circuit 23.
3 to sequentially send the codes to the buffer 5. That is, a 1-byte PAD character code PAD1 and a 3-byte synchronization establishment code SYN are sent, and then, as illustrated in Fig. 2 a to e,
Send STX code or DLE code and STX code.
After that, the text changes from buffer 21 to register 25.
Each byte is read out under the control of the control unit 30 and sent to the buffer 5. The text is simultaneously sent from the register 25 to the BCS generation circuit 29, which generates 2-byte block check sequence codes BCS1 and BCS2 using a known method. If the text length is shorter than the buffer length, it is necessary to determine where the end of the text is, and the decoder 27 is used to make this determination. After the text is stored in the buffer 5, under the control of the control unit 30,
The ETX code, ETB code, DLE code and ETB code are sent from the circuit 23 to the buffer 5. after that,
After the BCS1 and BCS2 codes are sent from the BCS generation circuit 29 to the buffer 5, the PAD2 is sent from the circuit 23.
A code is sent out. As a result, the messages 20 to 22 are reproduced from the headers H1 and H2 and the text shown in FIGS. 2a to 2c, respectively. thus,
In the buffer 5, in addition to the PAD1, PAD2, and SYN codes, a non-packet message is obtained using the normal basic procedure in which codes obtained by decoding H1 and H2 are added to the text. This message is sent to the corresponding non-packet terminal via the interface 3A.

As described above, according to the present invention, a packet message can be created by using a message length control header formed by compressing the transmission control code in a non-packet message and deleting a fixed code. It is possible to do this.

In addition, in the above embodiment, only three types of non-packet messages were explained, but the present invention
It is used to compress many types of messages, and only the parts necessary for understanding the present invention are shown here.

[Brief explanation of drawings]

FIGS. 1 and 2 are explanatory diagrams of embodiments of the present invention.

Claims (1)

[Claims] 1 means for identifying a predetermined transmission control code in a non-packet message received from a non-packet terminal;
In response to the identification result, means for generating a non-packet message length control header for compressing and displaying the identified transmission control code, the non-packet message length control header, and the text in the received non-packet message. means for synthesizing the data, adding a packet header thereto, and transmitting it to a packet switching network; means for generating a transmission control code corresponding to the non-packet message length control header of the packet message received from the packet switching network; A packet assembling and disassembling device comprising means for synthesizing the generated transmission control code and the text in the received packet message and transmitting the synthesized signal to a non-packet terminal.