JP3142027B2 - Frame distribution multiplexing method and switching system using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for transmitting and receiving a frame between a layer 2 terminal of a switching system and a communication device in a switching system accommodating a plurality of communication devices, and more particularly, to a method of synchronizing with a flag pattern as a layer 2 protocol. A method for distributing and multiplexing a frame by transmitting and receiving a frame having a logical link identifier using a method;
And a switching system for implementing the same.

[0002]

2. Description of the Related Art CCITT (International Telegraph and Telephone Advisory Committee)
Recommendation X. 25, the interface conditions of the packet switch are divided into three levels, level 1 (layer 1) defines electrical and physical conditions, and level 2 (layer 2 (data link layer)) The frame level protocol is specified, and the level 3 (layer 3 (network layer)) specifies the packet level protocol ("Packet switching technology and its application", August 20, 1980).
Published by The Institute of Electronics and Communication Engineers, pp.127-140). Layer 2
When implementing the protocol processing, the protocol processing is performed by firmware (that is, a microprogram) because the number of states is large and the logical depth is deep. Further, the layer 2 terminating unit of the conventional packet switch is
They are connected one-to-one with the lines of the communication device, and processing is performed at the termination unit for each line. As described above, the conventional communication devices do not always communicate, and it is necessary to always secure the line one-to-one with the communication device despite the low line usage rate. Therefore, the equipment of the layer 2 termination unit in the packet switch is also required for the line connection.
The amount of hardware was huge. On the other hand, a packet switching service using a B channel and a D channel has been added to the basic interface of the INS net 64. In packet switching, communication can be performed not only between B channels and D channels, but also between D channels and B channels. In this case, the transmission speed of the D channel is 16 Kbit / sec and the transmission speed of the B channel is 64 Kbit / sec, but communication can be performed between these different speed channels.

In a conventional switching system accommodating ISDN terminals, a circuit call control signal on a D channel, a manager
Since both the segment control signal and the packet call are communicated on the same D channel, the layer 2 terminates at one layer 2 terminating unit, and the higher-level processing unit distributes and multiplexes the packet call to form a packet call. Had been transferred to the processing unit. In this case, when the packet traffic becomes large, the load on the host processor increases, and there is a possibility that the circuit-switched call will be squeezed. On the other hand, for the B channel packet, in order to efficiently use the line to the packet call processing device, the layer 2 is temporarily terminated as in the case of the D channel packet, and after the frame is multiplexed by the upper processing device, Since the packet was transferred to the packet processing device, the load on the host processing device also increased. In order to avoid such an increase in the load, there is a method of directly connecting to the packet processing device by circuit switching. However, since this occupies a large number of lines, the line use efficiency is degraded, resulting in a bad return. Was.

[0004]

As described above, in the conventional frame transfer method between the layer 2 terminal of the switching system and the communication device, the amount of hardware at the layer 2 terminal is completely considered. Did not. That is, not all communication devices are constantly communicating, and even if a layer 2 link is established for communication, frames are not always transmitted and received. In spite of the low line utilization rate, the line between the conventional communication device and the layer 2 terminal unit and the equipment of the layer 2 terminal unit must always be secured on a one-to-one basis. There was a problem that the amount of hardware became enormous. On the other hand, when time-division multiplexing is performed to reduce the size of the device, high-speed processing of firmware is required to accommodate a large number of communication devices, and thus high multiplexing is difficult. Also, like the switching system that accommodates ISDN,
In a method in which a control signal or a packet call on the D channel is temporarily terminated at the layer 2 terminating unit, and a higher-level processing device performs distributed frame multiplexing on the packet call, all of these are transferred to the packet call processing device. There is a problem in that the load on the processing device increases, and processing of the circuit-switched call is suppressed. SUMMARY OF THE INVENTION An object of the present invention is to solve such a conventional problem, reduce the amount of hardware at a layer 2 terminal, and efficiently use a line to a layer 2 terminal.
It is another object of the present invention to provide a frame distribution multiplexing method capable of reducing the load on a host processor and a switching system using the method.

[0005]

In order to achieve the above-mentioned object, a method for multiplexing and allocating frames according to the present invention uses (a) a data link layer (layer 2) protocol using a synchronization method based on a flag pattern. In a switching system using a procedure for communicating with a frame having a logical link identifier and accommodating a plurality of communication devices, the switching system uses only the value of the logical link identifier in the frame received from the communication device, A number assigned to a line to a communication device and a logical link identifier in a frame used for communication with the communication device. The logical link identifier is converted into a unique value determined in the switching system and converted. The value is frame-multiplexed as the value of the logical link identifier in the frame, and transmitted to the corresponding line to the layer 2 termination unit in the switching system, and conversely, the layer 2 termination The value of the logical link identifier in the frame from the communication device to the communication device is converted into the value of the logical link identifier in the frame used for communication with the communication device, and is distributed to the line to the corresponding communication device. And send it out. Further, the exchange system of the present invention comprises:
Frames are transmitted and received between a plurality of communication devices, a first transmission / reception means for performing flag synchronization termination, 0 insertion / deletion, and FCS addition / inspection, and a layer 2 termination unit. And a buffer memory for temporarily storing frames received by the first and second transmission / reception means for transmitting / receiving data, performing termination of flag synchronization, 0 insertion / deletion, and FCS addition / inspection. And the number assigned to the line between the switching system and the communication device and the value of the logical link identifier in the frame used for communication between the switching system and the communication device are determined in the switching system. It is a unique value, and is converted into a number assigned to the line between the second transmitting / receiving means and the layer 2 terminator and the value of the logical link identifier in the frame, or vice versa. Hold and arbitrarily set An address translation table that can be changed and a logical link identifier used for communication with the layer 2 termination unit by referring to the address translation table and using the logical link identifier of the frame received from the communication device. , And controls the transmission to the corresponding line to the layer 2 terminal unit, and uses the logical link identifier of the frame received from the layer 2 terminal unit in communication with the communication device. Control means for converting the value into a logical link identifier value and transmitting the logical link identifier to a line to a corresponding communication device. (C) The same frame is further provided between the first frame distribution multiplexing unit including the first and second transmitting / receiving means, the buffer memory, the address conversion table and the control means, and the layer 2 terminating unit. A second frame distribution multiplexing unit having a configuration is provided, and the frame once multiplexed and transmitted from the communication device is re-frame multiplexed in the second frame distribution multiplexing unit. And the frame is sent to the above-mentioned layer 2 termination unit. Conversely, the frame from the layer 2 termination unit is distributed to the line to the first frame distribution and multiplexing unit in the second frame distribution and multiplexing unit. It is also characterized in that it is transmitted and distributed to the line to the corresponding communication device in the first frame distribution multiplexing section and transmitted. (D) When a plurality of communication devices accommodate ISDN terminals and are equipped with devices for processing service types such as line call control signals and packet calls, each service on the D channel is provided. Layer 2 of the control signal is terminated on the side of the apparatus that processes each service, and first and second transmission / reception means and buffers are provided between the plurality of ISDN terminals and the layer 2 termination unit. A frame distribution multiplexing unit comprising a memory, an address conversion table and control means is provided.
The frame distribution and multiplexing unit responds to a frame received from a plurality of ISDN terminals via the D channel by using an address field.
Each frame is sorted by the service access point identifier (SAP1) indicating the service type in the field, and the address conversion table and the control means are sent to the layer 2 termination unit on the side of the device that processes each service. And multiplexes the received frame from the layer 2 terminal to the corresponding line to the ISDN terminal by means of an address conversion table and control means. It is also a feature. Further, (e) an ISDN terminal is accommodated as a plurality of communication devices, and for a B channel packet from the ISDN terminal, the layer 2 of the packet call is configured to be processed by the device that processes the packet call. A frame distribution multiplexing unit comprising first and second transmission / reception means, a buffer memory, an address conversion table and a control means is provided between the ISDN terminal and the layer 2 terminal of the packet call, and the frame distribution is performed. The multiplexing unit multiplexes the frames received from the plurality of ISDN terminals via the B channel to the line of the corresponding packet to the layer 2 terminating unit by the address translation table and the control means, and transmits the multiplexed frames. Conversely, the frame received from the layer 2 terminal of the packet is transmitted to the corresponding ISDN terminal by the address translation table and the control means. Touch the -
It is also characterized by system multiplexing and transmission. further,
(F) A device for processing a packet call is configured to directly accommodate a general packet terminal, and a first terminal between the general packet terminal and the layer 2 termination unit in the device for processing a packet call. And a frame distribution multiplexing section comprising a second transmitting / receiving means, a buffer memory, an address conversion table and a control means, wherein the frame distribution multiplexing section addresses frames from a plurality of packet terminals. The conversion table and the control means perform frame multiplexing of the corresponding packet on the line to the layer 2 terminal and send it out.
Conversely, the frame from the layer 2 terminal of the packet is multiplexed and transmitted to the line to the corresponding packet terminal by the address translation table and the control means, and the ISDN terminal is viewed from the apparatus for processing the packet call. It is also characterized in that the B-channel packet from the general packet terminal and the packet from the general packet terminal are processed in a unified manner.

[0006]

According to the present invention, the value of the logical link identifier in the frame received from the communication device is converted, the frame is multiplexed and transmitted to the layer 2 terminal, while the frame from the layer 2 terminal is transmitted. The communication device according to the value of the logical link identifier of the communication system, and converts the value of the logical link identifier into a value to be used in the corresponding link and transmits the converted value. In order to reduce the load on the host processor, a frame distribution multiplexing unit and a processor independent of the host processor are provided in the exchange. As a result, it is possible to reduce the number of lines accommodated in the layer 2 termination unit without requiring a very high-speed line, and as a result, traffic is averaged, so that the lines can be used efficiently. Can be. In addition, it is possible to sort and multiplex frames without imposing a load on the processing device. Furthermore, since the frames are sorted and multiplexed only by the value of the logical link identifier, it can be realized in hardware without requiring any complicated processing.
Moreover, miniaturization is possible.

[0007]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing a switching system according to an embodiment of the present invention. In FIG. 1, reference numeral 1 in the circuit-switched call processor C denotes a layer 1 termination unit, 2 denotes a D-channel frame distribution / multiplexing unit, 3 denotes a B-channel frame distribution / multiplexing unit, and 4 denotes a layer 2 termination. , 5 is a communication path unit, 6 is a processing unit, 7 is an interface unit, 4 'in the packet switching call processing unit P is a layer 2 termination unit, and 6' is a processing unit. FIG. 1 contains a plurality of ISDN terminals,
A switching system comprising a circuit-switched call processor C and a packet-switched call processor P is shown. The layer 1 termination unit 1 of the circuit switching call processing device C
Is terminated, and the B channel is connected to the communication path unit 5,
The D channel is connected to the D channel frame distribution multiplexing unit 2. The layer 1 terminating unit 1 and the D-channel frame multiplexing unit 2 are connected by a time-division multiplexed highway as in the conventional method.
The layer 2 terminating unit 4 terminates the layer 2 of the line call control signal and the management control signal among the D channel signals separated by the D channel frame multiplexing unit 2. The B-channel frame distribution multiplexing unit 3 performs distribution multiplexing on B channel packets from the terminal or the packet switching call processing device P. The layer 2 terminating unit 4 'of the packet switching call processing device P terminates the layer 2 of the packet separated and multiplexed by the D channel frame sorting / multiplexing unit 2.

FIG. 2 is a diagram showing the frame distribution in FIG.
It is an internal block diagram of a multiplexing part. As shown in FIG. 2, each of the B-channel and D-channel frame distribution multiplexing units 2 and 3 in FIG. 1 transmits and receives frames to and from a buffer 24 for storing frames and terminals. Frame transmission / reception units 21a to 21n, layer 2 termination unit 4,
Frame transmitting / receiving unit 2 for transmitting / receiving a frame to / from 4 '
2a to 22m, address conversion table for writing received value
, A control unit 25 for controlling the whole, and a processing device interface unit 26. Flag synchronization, 0
Frame transmission / reception units 21a to 21n and 22a to 22m for performing insertion / deletion and FCS inspection / attachment correspond to lines between the terminal and the layer 2 termination unit 4 (or 4 '), respectively. Is provided. In this case, the number m of lines on the layer 2 terminating units 4 and 4 'is equal to the number n of lines on the terminal side.
Much smaller than (n >> m). These frame transmission / reception units 21a to 21n and 22a to 22m store the received frames in the buffer 24 and, at the same time, assign the value of the address field in the frame to the line between the terminal and the terminal. Number, the value of the address field in the frame used for communication with the terminal, and the layer 2 termination sections 4, 4 '.
And the value of the address field in the frame used in the communication with the layer 2 termination unit has a one-to-one correspondence so that the number given to the line between them and the value of the address field in the frame used in the communication with the layer 2 terminal unit do not overlap each other. The conversion is performed with reference to an address conversion table 23 holding a value (hereinafter, referred to as DLC1).

In FIG. 1, when the DLC 1 is notified from the processing unit 6 to the D-channel frame distribution multiplexing unit 2, the control unit 25 in the D-channel frame distribution multiplexing unit 2 shown in FIG. Is a processing device interface unit 26
Via the address conversion table 23.
This value is written to the corresponding position of and stored.
When a normal frame is received by any of the frame transmission / reception units 21a to 21n, the frame transmission / reception unit writes the received frame into the buffer 24, and simultaneously writes the received frame in accordance with the address field value within the frame. After distinguishing the line call control signal and the management control signal from the packet, converting the packet into the corresponding LDC 1 with reference to the address conversion table 23, the packet should be transmitted to any of the frame transmitting / receiving sections 22a to 22m. To decide. Frame transmitting / receiving sections 22a-2
The corresponding one of 2m is an address field from buffer 24.
Take out the converted frame of the
It is sent to the terminal 4, (or 4 '). As a result, frames from a plurality of lines on the side of the frame transmitting / receiving sections 21a to 21n are multiplexed and transmitted to the same line on the side of the frame transmitting / receiving sections 22a to 22m.

Conversely, when any one of the frame transmitting / receiving sections 22a to 22m receives the frame from the layer 2 termination section 4, 4 ', it writes this in the buffer 24 and at the same time simultaneously writes the address in the address conversion table. The value of the address field in the frame is converted with reference to the
a to 21 m is determined. One of the frame transmitting / receiving sections 21a to 21n is a buffer 2
Then, the converted frame of the address field is taken out from 4 and sent to the terminal. In the same way, the B channel packet multiplexing unit 3 refers to the address conversion table 23 holding the DLC 1 notified from the processing unit 6 for the B channel packet. The address field value in the frame from the layer 2 terminating unit 4 'in the packet call processor P is converted to perform frame distribution multiplexing, and the layer 2 terminating unit 4 in the corresponding packet call processor P is converted. 'Or to the line to the terminal.

FIG. 3 is a diagram showing a frame format of a D-channel signal communicated between the terminal and the layer 2 terminal shown in FIG.
It is a mat figure. For the D channel signal, the frame format between the terminal and the frame distribution multiplexing unit 2 and between the frame distribution multiplexing unit 2 and the layer 2 termination unit 4 or 4 'is shown in FIG. A, b, flag, address field, control field,
It consists of an information field, an FCS (Frame Check Sequence) and a flag.
The internal value is the frame converted according to the present embodiment.
It shows the correspondence between the address field values in the system. For example, the service access points SAP1 (C / R, EA) and TE1 (EA), which are the address field of the frame received from the terminal and indicate the service type, are:
DLC1 (SAP1, C / R, EA) (FC,
EA) After being converted to (EA), the layer 2 termination unit 4,
4 '. Also, the frame format from the layer 2 termination units 4 and 4 'is sent to the terminal after the internal value is converted.

In this embodiment, the frame multiplexing units 2 and 3 multiplex the frame only once and send it to the layer 2 termination units 4 and 4 '. It is also possible to multiplex and transmit the frames two or more times. That is, a frame distribution multiplexing unit shown in FIG. 2 is further provided between the frame distribution multiplexing units 2 and 3 and the layer 2 termination units 4 and 4 '. The frame transmitted from the communication device is once multiplexed and transmitted.
Further, the frame is multiplexed in a newly provided second frame distribution multiplexing unit, and the layer 2 termination unit 4
4 '. Conversely, the frames from the layer 2 termination units 4 and 4 'are also subjected to frame multiplexing by the newly provided frame distribution and multiplexing unit, and then to the frame distribution and multiplexing shown in FIG. The frames are multiplexed in the units 2 and 3 and distributed to the line to the communication device. Further, a general packet terminal is directly accommodated in the packet switching call processor P shown in FIG. 1, and between these packet terminals and the layer 2 termination unit 4 'in the packet switching call processor P. It is also possible to provide a frame distribution multiplexing unit shown in FIG. Thereby, when viewed from the packet switching call processing device P, the B channel packet from the ISDN terminal and the packet from the general packet terminal can be unified and processed.

As described above, in the present embodiment, the processing device performs the D conversion necessary for the conversion of the address field in the frame.
It is only necessary to notify LC1 and only by converting the address field value in the frame, the layer 2 termination units 4, 4 '
Since the frames are multiplexed and transmitted, it is possible to reduce the number of lines to the layer 2 terminating units 4 and 4 'and to operate the lines efficiently with almost no load on the processing unit. Can be. As a result, the amount of hardware of the layer 2 termination units 4, 4 'can be reduced. Also, the functions of the frame distribution / multiplexing unit can be realized in hardware, so that the size of the function unit can be reduced. Further, also in the case of accommodating ISDN terminals, frames can be sorted for each service type by referring to the address field value, so that optimal equipment can be arranged for each service. Therefore, economy can be achieved.

[0014]

As described above, according to the present invention,
By performing frame multiplexing, the number of lines to the layer 2 termination unit can be reduced, so that the lines can be effectively operated. Further, the load on the processing apparatus is hardly applied, the amount of hardware at the layer 2 termination unit can be reduced, and the size of the frame distribution / multiplexing unit can be reduced. Also, when accommodating ISDN terminals, the address field value can be converted and the frame can be sorted for each service type, so that the cost of equipment can be reduced.

[0015]

[Brief description of the drawings]

FIG. 1 is a block diagram showing a switching system accommodating a plurality of ISDN terminals according to an embodiment of the present invention.

FIG. 2 is an internal configuration diagram of a frame distribution multiplexing unit in FIG. 1;

FIG. 3 is a frame format diagram of a D channel signal communicated between the terminal and the frame distribution multiplexing unit in FIG. 1, and between the frame distribution multiplexing unit and the layer 2 terminal unit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Layer 1 termination part 2 D channel frame distribution and multiplexing part 3 B channel frame distribution and multiplexing part 4, 4 'Layer 2 termination part 5 Communication path part 6, 6' Processing unit 7 Interface part 21a-21n Terminal side frame transmission / reception section 22a-22m Layer 2 termination section side frame transmission / reception section 23 Address conversion table 24 Buffer 25 Control section in frame distribution / multiplexing section 26 Processing device interface section C Circuit switched call processor P Packet switched call processor

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-209298 (JP, A) JP-A-63-9400 (JP, A) JP-A-58-48592 (JP, A) JP-A 55-4852 161493 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04Q 11/00-11/08 H04L 12/56 H04Q 3/60

Claims (4)

(57) [Claims] 1. A data link layer (Layer 2) protocol which uses a synchronization method based on a flag pattern, uses a procedure for communicating using a frame having a logical link identifier, and uses ISDN terminals as a plurality of communication devices. /> Which accommodates the
In switching system comprising a packet-switched call processor, said circuit-switched call processor, frame received from the communication device - only the value of the logical link identifier in the beam was applied to the line between the communication device number And a logical link identifier in a frame used for communication with the communication device, which is converted into a unique value determined in the switching system.
Rewriting, the converted value frame - as the value of the logical link identifier in the beam frame - to beam multiplexing, D-channel signal
The line call control signal and the management signal are circuit switched calls.
The packet signal is transmitted to the corresponding line to the layer 2 termination unit in the processing device.
The corresponding line to the layer 2 terminating unit in the call switching equipment
And the value of the logical link identifier in the frame used for communication with the communication device is the value of the logical link identifier in the frame from any one of the layer 2 termination units to the communication device. A frame distribution multiplexing method characterized by converting the data into a data stream , rewriting the data, and transmitting the data to a communication apparatus. 2. In a switching system accommodating a plurality of communication devices, a frame is transmitted / received to / from the plurality of communication devices, and a flag synchronization termination, 0 insertion / deletion, and FCS assignment / check are performed. A second transmission / reception means for transmitting / receiving a frame between the transmission / reception means 1 and the layer 2 termination unit, and performing termination of flag synchronization, insertion / deletion of 0, and FCS addition / inspection; A buffer memory for temporarily storing the frames received by the transmitting / receiving means, a number assigned to the line between the switching system and the communication device, and a number used for communication between the switching system and the communication device. The value of the logical link identifier in the frame to be transmitted is the only value determined in the switching system, and the number and frame assigned to the line between the second transmitting / receiving means and the layer 2 termination unit. -Logical resources in the In order to convert to the value of the network identifier or vice versa, the address conversion table which is held in correspondence with each other and can be set or changed arbitrarily. The logical link identifier of the received frame is converted into the value of the logical link identifier used for communication with the layer 2 terminal unit, rewritten , and controlled so as to be transmitted to the line to the corresponding layer 2 terminal unit. Convert the logical link identifier of the frame received from the layer 2 terminal into the value of the logical link identifier used for communication with the communication device and rewrite it.
For example, a switching system, characterized by comprising a control means for controlling so as to delivered to the line to the appropriate communications device, to accommodate the ISDN terminal as the plurality of communication devices, line
Process for each service type such as call control signal and packet call
If equipped, each service on the D channel
Regarding layer 2 of the control signal, each service is processed.
And terminate at the equipment side.
Between the ISDN terminal and the layer 2 termination unit.
And second transmission / reception means, buffer memory, address translation
-Frame distribution multiplexing consisting of cables and control means
And a frame sorting / multiplexing unit , wherein the plurality of ISDN terminals
To the frame received via the D channel from the
Service access indicating the service type in the dress field
Each frame is assigned by the access point identifier (SAP1).
Separated by the address conversion table and the control means.
To the layer 2 terminal on the equipment side that processes each service.
The frame is multiplexed on the line and transmitted.
The frame received from the end is converted to the address conversion table
And to the line to the corresponding ISDN terminal by the control means
Switching system characterized by frame multiplexing and transmission
Tem . 3. The switching system according to claim 2 , wherein an ISDN terminal is accommodated as said plurality of communication devices.
For the B channel packet from the SDN terminal, the layer 2 of the packet call is configured to be processed by the device that processes the packet call, and the layer 2 of the packet call is interposed between the plurality of ISDN terminals and the layer 2 terminal of the packet call. First and second transmission / reception means, buffer memory, address conversion table
A frame distributing multiplexing unit comprising a frame and a control means. The frame distributing and multiplexing unit converts the frames received from the plurality of ISDN terminals via the B channel into the address conversion table and The frame is multiplexed and transmitted to the line to the layer 2 terminal of the corresponding packet by the control means. Conversely, the frame received from the layer 2 terminal of the packet is transmitted by the address conversion table and the control means. A switching system for transmitting a frame multiplexed signal to a line to an applicable ISDN terminal. 4. The switching system according to claim 3 , wherein the apparatus for processing the packet call is configured to directly accommodate a general packet terminal, and processes the general packet terminal and the packet call. A frame distribution multiplexing unit comprising the first and second transmission / reception means, a buffer memory, an address conversion table and a control means is provided between the apparatus and a layer 2 termination unit in the apparatus. The distribution multiplexing unit multiplexes the frames from the plurality of packet terminals to the line of the corresponding packet to the layer 2 terminating unit by the address conversion table and the control means, and transmits the multiplexed packets. The frame from the layer 2 terminating unit is multiplexed and transmitted to the line to the corresponding packet terminal by the address conversion table and control means, and the packet call is transmitted. When viewed from the management to equipment, I
A switching system wherein a B channel packet from an SDN terminal and a packet from a general packet terminal are processed in a unified manner.