JPH1028142A - Cell frame converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain voice communication with low delay, low abandoning rate and high quality by efficiently connecting a network using a cell relay for a trunk line system add using a frame relay for a branch line system. SOLUTION: A frame filter 2 identifies a frame inputted to a frame receiving circuit 1 and fragmented into a voice frame and the other frames. A cell assembly part 4 for an FR turns the other frames into a cell, and transmits it to a multiplexing circuit 5. A cell assembly part 3 for a voice converts a DLCI described in the header of the voice frame into ATM type VPI and VCI, turns it into a cell, and transmits it to the cell multiplexing circuit 5. The cell multiplexing circuit 5 multiplexes the cell turned into a cell by converting only the header by the cell assembly part 3 for the voice with the cell turned into a cell by the cell assembly part 4 for the FR, and transmits it from a cell transmitting circuit 6 to the direction of a trunk line.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cell frame conversion apparatus, and more particularly to a network system for connecting a trunk system constructed so as to be able to execute a cell relay service and a branch system constructed so as to be able to execute a frame relay service and performing voice communication. The cell frame conversion method.

[0002]

2. Description of the Related Art In recent years, when a network is constructed, a cell relay is often used for a trunk line system and a frame relay is used for a branch line system, and this tendency is expected to continue in the future. This is because a branch line system is generally constructed with a low-speed line, and a frame relay with little overhead is efficient and easily applicable to a branch line of a network.

[0003] Here, the cell relay refers to a cell relay service, which is a service for performing cell transfer using a high-speed digital leased line or the like. Frame relay refers to a frame relay service, which is a layer 2 frame relay service in which the network does not confirm the response, but confirms the delivery end-to-end by the user.

Normally, when voice communication is performed in the above-described network, a method of reducing fragmentation delay by performing fragmentation and priority control in a branch frame relay is used. The voice frame fragmented (divided) in the branch frame relay is converted into cells in the cell frame converter.

[0005]

In the above-described conventional cell frame conversion apparatus, the AAL [ATM (Asynchronous) is used between the branch frame relay and the trunk cell relay in the same manner as the other frames.
s Transfer Mode) Adaptati
on Layer] cell frame conversion by 3, 4, 5 etc. [ITU-T (International Tel)
communication Union-Telec
Communication Sector) Recommendation I. 3
62, I. Therefore, high quality such as low delay and low discard rate required for voice communication cannot be maintained.

That is, as shown in FIG. 5, a voice frame E fragmented in a branch line frame relay is converted into a cell in a cell frame converter 15. In this case, since the FR (frame) header E1 of the voice frame E is stored in the payload of the cell F or the size of the fragmented frame E is not aware of the size of the cells F and G, the two cells F and It may be divided into G.

That is, the FR header E1 of the voice frame E
The audio data E2 may be divided into a cell F including an ATM header F1, an FR header F2, and audio data F3, and a cell G including an ATM header G1 and audio data G2. For this reason, if a voice frame is converted into a cell frame between a branch frame relay and a trunk cell relay, the transfer efficiency deteriorates.

[0008] Further, since frame relay data is normally transferred on a best-effort basis (processing with the maximum processing efficiency within an allowable range among the resources of the apparatus),
High quality such as low delay and low discard rate required by voice communication cannot be maintained.

Therefore, an object of the present invention is to solve the above-mentioned problems, to efficiently connect a network using a cell relay for a trunk system and a frame relay for a branch system, and to provide a high quality network with low delay and low discard rate. It is an object of the present invention to provide a cell frame conversion device capable of performing various voice communications.

[0010]

A cell frame conversion apparatus according to the present invention has a network in which a trunk system is constructed so as to execute a cell relay service and a branch system connected to the trunk system is constructed so as to execute a frame relay service. The cell frame conversion device of the system, wherein the frame transmitted by the frame relay service is a voice frame whose payload portion is substantially equal in size to the payload portion of a cell transmitted by the cell relay service. Discriminating means for discriminating whether or not the frame discriminated as the voice frame by the discriminating means is converted to a cell to be transmitted to the trunk system; and a converting means for converting only a header portion of the frame to a header portion of the cell. And

Another cell frame conversion device according to the present invention is a cell frame of a network system in which a trunk system is constructed so as to be able to execute a cell relay service, and a branch system connected to the trunk system is constructed so as to be able to execute a frame relay service. A conversion device, a determination unit that determines whether a cell transmitted by the cell relay service is a voice cell, and only a header portion of the cell determined to be the voice cell by the determination unit is subjected to the frame relay service. Conversion means for converting the data into a header portion of a frame to be transmitted.

Another cell frame conversion device according to the present invention is a cell frame of a network system in which a trunk system is constructed so as to be able to execute a cell relay service and a branch line connected to the trunk system is constructed so as to be able to execute a frame relay service. A conversion apparatus for determining whether a frame transmitted by the frame relay service is a voice frame whose payload portion has a size substantially equal to the size of a payload portion of a cell transmitted by the cell relay service. First determining means, and converting only the header part of the frame into a header part of the cell when converting the frame determined as the voice frame by the first determining means into a cell to be transmitted to the trunk system. First conversion means for determining whether a cell transmitted by the cell relay service is a voice cell Second determining means, and second converting means for converting only the header part of the cell determined to be the voice cell by the second determining means into a header part of a frame transmitted by the frame relay service. It has.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the operation of the present invention will be described below.

When a frame transmitted by the frame relay service is determined by the frame filter to be an audio frame whose payload portion is substantially equal in size to the payload portion of a cell transmitted by the cell relay service, When the frame is converted into a cell to be transmitted to the trunk system by the use cell assembly unit 3, only the header part of the frame is converted into the header part of the cell.

When a cell transmitted by the cell relay service is determined to be a voice cell by the cell filter, only the header part of the cell is replaced by a voice cell disassembly unit with a header part of a frame transmitted by the frame relay service. Convert.

This makes it possible to efficiently connect a network that uses a cell relay for the trunk system and a frame relay for the branch system, and perform high-quality voice communication with low delay and low discard rate.

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a conversion unit from a branch system to a trunk system of a cell frame conversion apparatus according to an embodiment of the present invention.

In the figure, a conversion unit from a branch line system to a trunk system of a cell frame conversion apparatus includes a frame receiving circuit 1 and
A frame filter 2, an audio cell assembly unit 3,
It comprises a FR (frame relay) cell assembly unit 4, a cell multiplexing circuit 5, and a cell transmitting circuit 6.

The voice cell assembly unit 3 includes a header / payload separation circuit 31 and a DLCI (Data Link).
A connection identifier (DLC) identification circuit 32 and a DLCI / VPI (Virtual Pa
th Identifier), VCI (Virtua)
l Channel Identifier) conversion circuit 33 and DLCI / VPI, VCI conversion table 34
And a cell assembling circuit 35.

The voice frame transmitted by the branch frame relay is fragmented (divided) by a cell-conscious size "header + 48 bytes" at each terminal (not shown). When input to the circuit 1, the frame filter 2 sorts the frame into an audio frame and other frames.

The frame filter 2 sends the frame selected as a voice frame to the voice cell assembly unit 3, and the other frames selected as FR
To the cell assembly unit 4. The FR cell assembly unit 4 converts the frames selected as other frames into cells and sends the cells to the cell multiplexing circuit 5.

In the audio cell assembly section 3, the header / payload separation circuit 31 separates the header and the payload of the frame selected as the audio frame, and converts the header into a DL.
The packet is sent to the CI identification circuit 32, and the payload for frame relay is output to the cell assembling circuit 35.

The header includes a DLCI identification circuit 32 and a DLCI
Via the / VPI, VCI conversion circuit 33, for example, A
It is cellized by AL1 or the like. A table for audio is stored in the DLCI / VPI / VCI conversion table 34 in advance, and is referred to at the time of header conversion.

That is, the DLCI identification circuit 32 identifies the route of the frame (data) based on the DLCI described in the header. The DLCI / VPI / VCI conversion circuit 33 converts the data into an ATM type VPI / VCI description with reference to the DLCI / VPI / VCI conversion table 34 based on the route of the frame identified by the DLCI identification circuit 32.

DLCI / VPI, VCI conversion table 3
Reference numeral 4 denotes a DLCI described in the header as an ATM type VPI,
A routing table for converting to a VCI,
The DLCI / VPI / VCI conversion circuit 33 outputs the DLCI / V
The header value is converted according to the destination determined by the PI, VCI conversion table 34.

The cell assembling circuit 35 includes a payload (voice data not converted for cell relay) separated by the header / payload separating circuit 31, DLCI / VPI,
The header converted by the VCI conversion circuit 33 is assembled and sent to the cell multiplexing circuit 5.

The cell multiplexing circuit 5 multiplexes the cell obtained by converting only the header in the voice cell assembly unit 3 and the cell obtained by the FR cell assembly unit 4 and multiplexes the cell from the cell transmission circuit 6 to the trunk system. Send in the direction. Note that the cell multiplexing circuit 5 and the cell transmission circuit 6 perform priority control of voice cells, and perform CBR (Constant Bit Rate) transmission.

FIG. 2 is a block diagram showing a configuration of a conversion unit from a trunk system to a branch system in a cell frame converter according to an embodiment of the present invention. In the figure, the conversion unit from the trunk system to the branch system of the cell frame conversion apparatus includes a cell receiving circuit 7, a cell filter 8, a cell disassembly unit 9 for audio, a cell disassembly unit 10 for FR, and a frame multiplexing unit. It comprises a circuit 11 and a frame transmission circuit 12.

The audio cell disassembly unit 9 includes a header / payload separation circuit 91, a VPI / VCI identification circuit 92, a VPI / VCI / DLCI conversion circuit 93,
It comprises a PI, VCI / DLCI conversion table 94 and a frame assembly circuit 95.

When a cell is input to the cell receiving circuit 7, the cell filter 8 sorts the cell into a voice cell and other cells, and sends the selected cell as a voice cell to the voice cell disassembly section 9. Then, the cells selected as other cells are sent to the FR cell disassembly unit 10. The FR cell disassembly unit 10 frames the cells selected as other cells and sends them to the frame multiplexing circuit 11.

In the audio cell disassembly section 9, the header / payload separation circuit 91 separates the header and the payload of the cell selected as an audio cell, and converts the header into a VP.
The data is sent to the I / VCI identification circuit 92, and the payload for frame relay is output to the frame assembling circuit 95.

The header includes a VPI / VCI identification circuit 92 and V
The frame is formed via the PI and VCI / DLCI conversion circuit 93. The VPI, VCI / DLCI conversion table 94 stores a voice table in advance and is referred to at the time of header conversion.

That is, the VPI / VCI identifying circuit 92 identifies the cell route based on the VPI / VCI described in the header. The VPI / VCI / DLCI conversion circuit 93 outputs V
Based on the path of the cell identified by the PI and VCI identification circuit 92, the data is converted into a DLCI description by referring to a VPI / VCI / DLCI conversion table 94.

VPI, VCI / DLCI conversion table 9
Reference numeral 4 denotes a routing table for converting VPI and VCI described in the header into DLCI.
The CI / DLCI conversion circuit 93 is a VPI, VCI / DLC
The header value is converted according to the destination determined by the I conversion table 94.

The frame assembling circuit 95 includes a payload (voice data not converted for cell relay) separated by the header / payload separating circuit 91, VPI, VCI
The header converted by the / DLCI conversion circuit 93 is assembled and sent to the frame multiplexing circuit 11.

The frame multiplexing circuit 11 multiplexes the frame formed by converting only the header by the audio cell disassembly section 9 and the cell formed by the FR cell disassembly section 10, and outputs the multiplexed frame from the frame transmission circuit 12. Transmit in the branch line direction. Note that the frame multiplexing circuit 11 and the frame transmission circuit 12 perform priority control of audio frames.

FIG. 3 is a diagram for explaining cell frame conversion according to one embodiment of the present invention. In the figure, a voice frame A transmitted by a branch frame relay is fragmented in a cell-conscious size “header + 48 bytes”.

In the payloads of the voice frame A and the voice cell B, original headers A2 and B2 for determining whether or not the frame filter 2 and the cell filter 8 in the cell frame converter 13 are voices are included. I have.
Note that the cell frame converter 13 includes the converter shown in FIGS. 1 and 2 described above.

Further, the size of the original headers A2 and B2 is 1 byte, for example, "0XXX" for audio.
If "XXXXXX" is set and "1XXXXXXXXX" is set for the other, it is possible to select between audio and others.

Here, the audio frame A is composed of a header A1 composed of a DLCI, a payload (4) composed of an original header A2 and audio data A3 for frame relay.
8 bytes). Voice cell B is VP
I and VCI header B1 and original header B
2 and a payload (48 bytes) composed of audio data B3 for frame relay.

The voice frame A and the voice cell B selected by the original headers A2 and B2 are efficiently converted into cell frames by converting between DLCI and VPI and VCI.

FIG. 4 is a diagram for explaining cell frame conversion according to another embodiment of the present invention. In the figure, a voice frame C transmitted by a branch line frame relay is fragmented in a cell-conscious size "header + 48 bytes".

The DLCI and the VPI and VCI of the headers C1 and D1 of the voice frame C and the voice cell D are set within the range of voice values. Then, it is determined whether or not the cell filter 8 is a voice. Note that the cell frame converter 14 includes the converter shown in FIGS. 1 and 2 described above.

Further, as a range of values for the DLCI voice, for example, 0 to 511 are allocated to voice and 512 to 1024 are allocated to other voices, so that voice and others can be distinguished. I have to. This DLC
The setting of the value range for the voice of I may be any value as long as the value for voice and the other voice can be selected. Also, VP
As for the values of I and VCI, any value may be used as long as the value for audio and the other can be selected, similarly to the setting of the value range for audio for DLCI.

Here, the audio frame C is composed of a header C1 composed of DLCI and a payload (48 bytes) composed of audio data C2 for frame relay. Voice cell D is a header D composed of VPI and VCI
1 and a payload (48 bytes) composed of audio data D2 for frame relay.

The voice frames C and voice cells D selected according to the range of voice values of DLCI, VPI, and VCI are efficiently converted to cell frames by converting between DLCI, VPI, and VCI.

As described above, the frame transmitted by the frame relay service is determined to be a voice frame in which the size of the payload portion is substantially equal to the size of the payload portion of the cell transmitted by the cell relay service by the frame filter 2. When done, the cell assembly part 3 for voice
When the frame is converted into a cell to be transmitted to the trunk system, only the header part of the frame is converted into a header part of the cell, and when a cell transmitted by the cell relay service is determined as a voice cell by the cell filter 8, By converting only the header part of the cell into the header part of the frame transmitted by the frame relay service in the voice cell disassembly unit 9, the network using the cell relay for the trunk system and the frame relay for the branch system can be efficiently constructed. Connected, high-quality voice communication with low delay and low discard rate can be performed.

[0048]

As described above, according to the present invention, in a network system in which a trunk system is constructed so as to be able to execute a cell relay service and a branch system connected to the trunk system is constructed so as to be able to execute a frame relay service, When a frame transmitted by the frame relay service is determined to be a voice frame in which the size of the payload portion is substantially the same as the size of the payload portion of the cell transmitted by the cell relay service, the cell transmitting the frame to the trunk system. When a cell transmitted by the cell relay service is determined to be a voice cell, only the header portion of the cell is converted by the frame relay service. By converting to the header part of the cell, A network using frame relay to the branch line system and with a laser connected efficiently, there is an effect that it is possible to perform high-quality voice communications low latency and low discard rate.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a conversion unit from a branch system to a trunk system of a cell frame conversion apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a conversion unit from a trunk system to a branch system in a cell frame conversion apparatus according to an embodiment of the present invention.

FIG. 3 is a diagram illustrating cell frame conversion according to an embodiment of the present invention.

FIG. 4 is a diagram for explaining cell frame conversion according to another embodiment of the present invention.

FIG. 5 is a diagram for explaining cell frame conversion according to a conventional example.

[Explanation of symbols]

 Reference Signs List 1 frame receiving circuit 2 frame filter 3 audio cell assembly section 4 FR cell assembly section 5 cell multiplexing circuit 6 cell transmission circuit 7 cell reception circuit 8 cell filter 9 audio cell disassembly section 10 FR cell disassembly section 11 frame Multiplexing circuit 12 Frame transmission circuit 13, 14 Cell frame conversion device 31, 91 Header / payload separation circuit 32 DLCI identification circuit 33 DLCI / VPI, VCI conversion circuit 34 DLCI / VPI, VCI conversion table 35 Cell assembly circuit 92 VPI, VCI identification Circuit 93 VPI / VCI / DLCI conversion circuit 94 VPI / VCI / DLCI conversion table 95 Frame assembly circuit

Claims (9)

[Claims] 1. A cell frame conversion device for a network system, wherein a trunk system is constructed so as to execute a cell relay service and a branch system connected to the trunk system is constructed so as to execute a frame relay service, wherein the frame relay is provided. Determining means for determining whether or not the frame transmitted by the service is a voice frame whose payload portion size is substantially equal to the size of the payload portion of the cell transmitted by the cell relay service; and A conversion unit for converting only a header part of the frame into a header part of the cell when converting a frame determined as a voice frame into a cell to be transmitted to the trunk system. 2. The apparatus according to claim 1, wherein said discriminating means is configured to discriminate whether or not the frame is an audio frame in accordance with the presence or absence of audio information which is preliminarily added to a payload portion of the frame and indicates the audio frame. The cell frame conversion device according to claim 1, wherein 3. The apparatus according to claim 2, wherein said discriminating means is configured to discriminate whether or not the frame is the voice frame in accordance with a value added to a header portion of the frame in advance and indicating that the frame is the voice frame. Item 2. The cell frame conversion device according to Item 1. 4. A cell frame conversion device for a network system, wherein a trunk system is constructed so as to be able to execute a cell relay service, and a branch system connected to the trunk system is constructed so as to be able to execute a frame relay service. Discriminating means for discriminating whether or not a cell transmitted by the above is a voice cell; and converting only a header part of the cell discriminated as the voice cell by the discriminating means into a header part of a frame transmitted by the frame relay service. And a conversion unit for converting the cell frame. 5. The apparatus according to claim 1, wherein said discriminating means discriminates whether or not the cell is a voice cell in accordance with the presence or absence of voice information which is previously added to a payload portion of the cell and indicates the voice frame. The cell frame conversion device according to claim 4, wherein 6. The apparatus according to claim 1, wherein said discriminating means is configured to determine whether or not the cell is the voice cell according to a value which is added in advance to a header portion of the cell and indicates that the cell is the voice cell. Item 5. The cell frame conversion device according to Item 4. 7. A cell frame conversion device for a network system, wherein a trunk system is constructed so as to be able to execute a cell relay service, and a branch system connected to the trunk system is constructed so as to be able to execute a frame relay service. First determining means for determining whether or not the frame transmitted by the service is an audio frame in which the size of the payload portion is substantially the same as the size of the payload portion of the cell transmitted by the cell relay service; A first conversion unit that converts only a header part of the frame into a header part of the cell when converting the frame determined as the voice frame by the determination unit into a cell to be transmitted to the trunk system; Second determining means for determining whether or not a cell transmitted by the service is a voice cell; Cell frame conversion apparatus characterized by and a second converting means for converting only the header portion of the cell where it is determined that the voice cell stage in the header of the frame to be transmitted by the Frame Relay Service. 8. The apparatus according to claim 1, wherein said first discriminating means is configured to discriminate whether said frame is an audio frame in accordance with presence / absence of audio information which is previously added to a payload portion of said frame and indicates said audio frame. Wherein the second determination unit is configured to determine whether or not the cell is the voice cell in accordance with the presence or absence of voice information which is previously added to a payload portion of the cell and indicates the voice frame. The cell frame conversion device according to claim 7, wherein 9. The apparatus according to claim 1, wherein the first determination unit is configured to determine whether or not the frame is the voice frame according to a value which is added in advance to a header portion of the frame and indicates that the frame is the voice frame. 8. The apparatus according to claim 7, wherein the determining means is configured to determine whether or not the cell is the voice cell according to a value which is added in advance to a header portion of the cell and indicates the voice cell. Cell frame converter.