JP2006128859A - Frame transfer device and frame transfer system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a frame transfer device and a frame transfer system which allow a frame of the high priority to be immediately transferred even during transfer of frames of low priorities. <P>SOLUTION: The frame transfer device for transferring frames having at least two priorities from a first communication line to a second communication line is provided with a frame division management part which controls an operation of dividing a frame inputted from the first communication line into packet units, and a packet of the high priority is transferred by interruption even during transfer of a packet of the low priority in the case that the frame of the high priority is inputted from the first communication line during transfer to the second communication line of the packet of the low priority, which is divided by an indication of the frame division control part. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a frame transfer apparatus and a frame transfer system that connect a communication network such as a WAN (Wide Area Network) and a user-side LAN (Local Area Network), and more particularly to a high-priority frame even during transfer of a low-priority frame. The present invention relates to a frame transfer apparatus and a frame transfer system that can transfer immediately.

  In recent years, Ethernet (registered trademark) transmission is changing from normal best-effort type to priority processing transmission accompanied with QoS (Quality of Service), and has become a trend. This QoS is used for an interface converter using an ATM (Asynchronous Transfer Mode) network that sends two or more types of traffic having different priorities onto a single network.

  In particular, in the case of an interface converter having a dedicated line on the network side (WAN side), the transmission speed on the dedicated line network side is often very slow compared to the terminal side (LAN side), so VoIP (Voice Over Internet Protocol) etc. It is necessary to preferentially transfer frames with high priority that require real-time performance to the private network side.

  Here, the TOS (Type of Service) field of the frame is used for this priority transfer. Various parameters such as delay time, throughput, and reliability are defined in the TOS field, and the user can make various settings by combining these parameters. As a prior art document of a communication system using such a priority order system, there is one such as Patent Document 1.

Japanese Patent No. 3457636

  Hereinafter, a conventional frame transfer apparatus will be described with reference to FIG. FIG. 4 is a block diagram of a conventional frame transfer apparatus. In FIG. 4, the frame transfer apparatus 1 includes a priority detection unit 2, a priority buffer 3, and a non-priority buffer 4. The priority detection unit 2 detects the priority from field information such as a TOS field of a frame input from the LAN, and transfers the priority to the priority buffer 3 if the frame is a high priority frame, and the non-priority buffer 4 if the frame is a low priority frame. Forward to. The priority buffer 3 stores the high priority frame and outputs it if the WAN line is available, the non-priority buffer 4 stores the low priority frame, and if the priority buffer 3 does not have the high priority frame, the low priority frame is output. Output to WAN.

  Next, the operation of FIG. 4 will be described with reference to FIG. FIG. 5 is an explanatory diagram of the state of frame processing in the conventional frame transfer apparatus. Frames input from the LAN to the frame transfer device 1 are detected by the priority detection unit 2 and input to the priority buffer 3 if they are high priority frames and input to the non-priority buffer 4 if they are low priority frames. Is done. At this time, even if the priority detection unit 2 detects the high priority frame during the transfer of the low priority frame, the high priority frame is not transferred until one frame of the low priority frame is transferred.

  That is, the high priority frame is input to the frame transfer apparatus at the time point “a” in FIG. 5, but the high priority frame is stored in the priority buffer 3 of the frame transfer apparatus 1 until the time point “b” when the transfer of the low priority frame is completed. It will stay. Then, the high-priority frame is transferred from the point “b” when the transfer of the low-priority frame is completed, and the operation ends when the final cell has been transferred.

  The packet transmission interval (symbol P) in FIG. 5 is determined in accordance with the ATM speed, and when using ATM, the Ethernet (registered trademark) frame is packetized into a fixed length (for example, 48 bytes). For example, AAL5 is used as a protocol for performing the encapsulation of the frame.

  As described above, the configuration shown in FIG. 4 has an advantage that a communication device compatible with QoS can be provided by a protocol (AAL5) already in practical use.

  However, in protocols that are sensitive to jitter in the transmission period such as VoIP, when the residence time in the apparatus is increased, the jitter increases, and the worst case such as voice interruption may occur.

  This occurs because the AAL5 type or the like is used for the encapsulation protocol. That is, since this protocol has only a function for identifying the information “the last packet of a frame” and sends out one frame continuously to a WAN or the like, a low-priority frame currently being sent There is a problem that a high-priority frame cannot be transmitted unless all the frames are transmitted.

  FIG. 6 shows the state of the packet at this time. 6A is an example of packet transmission in the conventional frame transfer apparatus, and FIG. 6A is a state explanatory diagram showing the state of packet combination output from the frame transfer apparatus shown in FIG. As apparent from FIG. 6A, when a frame is output to the WAN, it is packetized and output in units of frames. However, since the replacement of priority processing is in units of frames, if all packets for one frame are not output (in (A), three “low” priority packets are output in succession), even if the frame has a high priority. Even if is input, it cannot be interrupted immediately. Accordingly, in the reception operation in (a), the low priority frame (three “low” priority packets are continuously received) is received before the high priority frame.

  In addition, AAL3 / 4 exists as a protocol for identifying in units of packets that can avoid such problems. However, these protocols have a large identifier header and have only a check function in units of packets. Are small and the circuit scale is large.

In order to achieve such a problem, the invention according to claim 1 of the present invention is:
In a frame transfer apparatus for transferring a frame having at least two priorities from a first communication line to a second communication line,
A frame division management unit for controlling an operation of dividing a frame input from the first communication line into packets;
When transferring the low priority packet divided by the instruction of the frame division control unit to the second communication line, if the high priority frame is input from the first communication line, the high priority packet is transmitted even during the transfer of the low priority packet. Interrupt and transfer.

  According to a second aspect of the present invention, the frame division management unit further includes a frame check calculation unit that adds check information to the frame divided in units of packets.

According to a third aspect of the present invention, a frame having at least two priorities is input, a detection unit that detects the priority of these frames, and the frame is stored for each priority detected by the detection unit. A first communication device including a buffer unit including a plurality of buffers, and a second communication device connected to the first communication device via a communication line and receiving the frame via the communication line. In a frame transfer system comprising:
The first communication device is:
An operation for controlling the operation of dividing the frame into packets, and when a high-priority frame is input during transfer of a low-priority packet, interrupts the high-priority packet even during transfer of the low-priority packet and outputs it to the communication line A frame division management unit for controlling
A packet generator for adding position information and priority information to the packet;
The second communication device is:
A packet decomposing unit that detects position information and priority information of a packet input from the first communication device via a communication line;
A frame generation unit that combines the packets in units of frames in the order of the position information for each priority detected by the packet decomposing unit.

  According to a fourth aspect of the present invention, in the third aspect of the present invention, the packet generation unit includes a first frame check calculation unit that adds check information to the packet output from the buffer unit.

  According to a fifth aspect of the present invention, in the third aspect of the present invention, the packet disassembling unit receives a frame input via a communication line based on the check information added by the first frame check calculation unit. Is provided with a second frame check operation unit for checking whether there is any error.

The present invention has the following effects.
When transferring a low priority packet to the second communication line, if a high priority frame is input from the first communication line, the high priority packet is interrupted and transferred even during transfer of the low priority packet. It is possible to provide a frame transfer apparatus that can immediately transfer a high priority frame even during transfer.

  In addition, since the frame check operation unit for adding check information to the frame divided in packet units is provided, even if an error occurs during frame transfer, it can be easily detected.

  In addition, the first communication device controls the operation of dividing the frame into packets, and if a high priority frame is input during transfer of the low priority packet, the high priority packet is interrupted even during transfer of the low priority packet. Since the frame division management unit that controls the operation to be output to the communication line is provided, it is possible to provide a frame transfer system that can immediately transfer the high priority frame even during the transfer of the low priority frame.

  In addition, since the packet generation unit includes the first frame check calculation unit that adds check information to the packet output from the buffer unit, it can be easily detected even if an error occurs during frame transfer.

  Further, since the packet decomposition unit includes a second frame check calculation unit that checks whether there is an error in a frame input via the communication line based on the check information added by the first frame check calculation unit. Even if an error occurs during frame transfer, it can be easily detected.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a communication system of the present invention. In FIG. 1, the frame transfer system 100 includes a transmission device 200 and a reception device 300, and data output from the transmission device 200 to the WAN is input to the reception device 300 (symbol Q) via the WAN.

  The transmission apparatus 200 includes a priority detection unit 210, a priority buffer 220, a non-priority buffer 230, a packet generation unit 240, and a frame division management unit 250. A frame is input from the LAN to the priority detection unit 210. The priority buffer 220 receives and accumulates the high priority frame detected by the priority detection unit 210. The non-priority buffer 230 receives and accumulates the low priority frame detected by the priority detection unit 210.

  The packet generation unit 240 includes a packet synthesis unit 241, a frame check calculation unit 242, an attribute information addition unit 243, and a position information addition unit 244. A frame is input from the priority buffer 220 or the non-priority buffer 230 to the packet synthesis unit 241. A frame is input from the priority buffer 220 or the non-priority buffer 230 to the frame check operation unit 242, and data such as a checksum for confirming the normality at the time of frame combination in the receiving device 300 is added to the packet synthesis unit 241. Output. The frame check operation unit 242 may be omitted if normality is not confirmed.

  The attribute information adding unit 243 adds attribute information including a high priority frame and a low priority frame to the frame, and the position information adding unit 244 is a packet including the first, second, third,... Nth packets. The position information indicating the position of is added. Here, the attribute information and position information are represented as in the frame format of the present invention in FIG. In FIG. 2, a header area for identification is secured in the first two bytes of each packet, and attribute information and position information are added to this area.

  For example, in the case of ATM, since the frame length is a fixed length of 48 bytes, data to be transmitted is added to the remaining 46 bytes. Then, PAD (Padding Bit), that is, an adjustment bit is inserted for a portion that is less than the fixed length of 48 bytes, and trailer information for checking the normality of the frame for each attribute (for example, consisting of 8 bytes). Is added.

  The frame division management unit 250 controls and manages operations in the packet generation unit 240, that is, operations of the frame check calculation unit 242, the attribute information addition unit 243, and the position information addition unit 244.

  Next, the configuration of receiving apparatus 300 will be described. The receiving apparatus 300 includes a packet decomposition unit 310 and a frame generation unit 320. The packet decomposition unit 310 includes a priority detection unit 311, a position information detection unit 312, and a frame check calculation unit 313. The priority detection unit 311 detects the priority information of the packet input from the transmission device 200 via the WAN, that is, the priority added by the attribute information addition unit of the packet generation unit 240.

  The position information detection unit 312 detects the position information added by the position information addition unit 244. The frame check calculation unit 313 calculates the checksum added by the frame check calculation unit 242 and checks whether there is an error in frame transfer. If the frame check calculation unit 242 is omitted and the normality check is not performed, the frame check calculation unit 313 may be omitted.

  The frame generation unit 320 includes a priority frame combination unit 321 and a non-priority frame combination unit 322, and outputs frames combined by these to the LAN. The priority frame combining unit 321 is a buffer that accumulates the high priority frames detected by the priority detection unit 311, and combines packets composed of high priority frames based on the position information detected by the position information detection unit 312. The non-priority frame combination unit 322 is a buffer for accumulating the low priority frames detected by the priority detection unit 311, and combines packets composed of low priority frames based on the position information detected by the position information detection unit 312.

  Next, the operation of FIG. 1 will be described. The priority of the data input from the LAN to the priority detection unit 210 is detected, a high priority frame is output to the priority buffer 220, and a low priority frame is output to the non-priority buffer 230.

  A frame input from the priority buffer 220 or the non-priority buffer 230 to the packet combining unit 241 is added with attribute information and position information by the attribute information adding unit 243 and the position information adding unit 244, respectively, and is divided into packet units and sent to the WAN. Is output. Note that data such as a checksum for confirming normality at the time of frame combination is added to the frame input to the frame check calculation unit 242 and output to the packet synthesis unit 241. This operation is not performed in the configuration in which the check calculation unit 242 is not provided.

  The priority of the packet input to the receiving apparatus 300 via the WAN is detected by the priority detection unit 311, and the position information is detected by the position information detection unit 312. The packet in which such information is detected is output to the priority frame combining unit 321 if it is a high priority frame, and is output to the non-priority frame combining unit 322 if it is a low priority frame. The priority frame combining unit 321 combines high priority packets based on the position information detected by the position information detecting unit 312 and outputs the combined packets to the LAN. The non-priority frame combination unit 322 combines the low priority packets based on the position information detected by the position information detection unit 312 and outputs them to the LAN.

  Next, the operation of the transmission apparatus in FIG. 1 will be described with reference to FIG. FIG. 3 is a frame state transition diagram in transmitting apparatus 200 for supplementing the operation of FIG. First, when a low priority frame is input from the LAN, attribute information is added by the attribute information adding unit 243 and position information is added by the position information adding unit 244. Here, since the low priority frame has the attribute “2” and the high priority frame has the attribute “1”, “1” is added to the position information of the first packet, and “2” is added as the attribute information to the WAN. Is output.

  When a high priority frame is input while a low priority frame is being input (symbol c), the packet generation unit 240 interrupts the transfer of the low priority frame under the control of the frame division management unit 250 and the high priority frame Will be output. In other words, in FIG. 2, the position information “1” is added to the second packet (code d) that is output, “1” is added as attribute information, and the packet is output from the packet combining unit 241 to the WAN. .

  Similarly, since the third frame is also preferentially output, the high-priority frame, that is, the attribute information “1” and the position information “2” are output to the WAN (symbol “e”). When all the high-priority packets have been output in this way (reference f), the low-priority frame whose output has been interrupted due to the input of the high-priority frame is output to the WAN. That is, in FIG. 3, the position information “2” is output to the WAN after the final high-priority packet is output (symbol f), and the low-priority packet “2” is output as attribute information (symbol g). The low priority packet “3” is output to the WAN (symbol h).

  Thus, when transferring a low priority packet to the WAN, if a high priority frame is input from the LAN, the high priority packet is interrupted and transferred even during transfer of the low priority packet. It is possible to provide a frame transfer apparatus that can immediately transfer a priority frame.

  In addition, since the frame check operation unit 242 for adding check information to the frame divided in packet units is provided, even if an error occurs during frame transfer, it can be easily detected.

  In addition, the transmission apparatus 200 controls the operation of dividing the frame into packets, and when a high priority frame is input during the transfer of the low priority packet, the high priority packet is interrupted even during the transfer of the low priority packet to the WAN. Since the frame division management unit 250 that controls the output operation is provided, it is possible to provide the frame transfer system 100 that can immediately transfer the high priority frame even during the transfer of the low priority frame.

  Further, since the packet generation unit 240 includes the frame check calculation unit 242 that adds check information to the packet output from the buffer unit, it can be easily detected even if an error occurs during frame transfer.

  Further, the packet decomposing unit 310 includes a frame check calculating unit 313 that checks whether there is an error in a frame input via the WAN based on the check information added by the frame check calculating unit 242. Even if an error occurs, it can be easily detected.

  In the present invention, a frame having two types of priorities has been described as an example, but a frame having three or more types of priorities may be used.

It is the block diagram which showed one Example of the communication system of this invention. It is a frame format of the present invention. FIG. 3 is a state transition diagram of a frame in a transmission apparatus 200 for supplementing the operation of FIG. It is the block diagram which showed one Example of the frame transfer apparatus of a prior art. FIG. 5 is a frame state transition diagram of the frame transfer apparatus 1 supplementing the operation of FIG. 4. (A) is an example of packet transmission in the frame transfer device of the prior art, and (A) is a state explanatory diagram showing the state of packet combination output from the frame transfer device shown in (A).

Explanation of symbols

100 frame transfer system 200 transmission device 210 priority detection unit 220 priority buffer 230 non-priority buffer 240 packet generation unit 241 packet synthesis unit 242 frame check operation unit 243 attribute information addition unit 244 position information addition unit 250 frame division management unit 300 reception device 310 packet decomposition unit 311 priority detection unit 312 position information detection unit 320 frame generation unit 321 priority frame combination unit 322 non-priority frame combination unit

Claims (5)

In a frame transfer apparatus for transferring a frame having at least two priorities from a first communication line to a second communication line,
A frame division management unit for controlling an operation of dividing a frame input from the first communication line into packets;
When transferring the low priority packet divided by the instruction of the frame division control unit to the second communication line, if the high priority frame is input from the first communication line, the high priority packet is transmitted even during the transfer of the low priority packet. A frame transfer apparatus which transfers by interrupting.   2. The frame transfer apparatus according to claim 1, further comprising a frame check calculation unit that adds check information to a frame divided in packet units by the frame division management unit. A detection unit that receives frames having at least two priorities and detects the priorities of these frames; and a buffer unit that includes a plurality of buffers that accumulate the frames for each priority detected by the detection unit. In a frame transfer system comprising: a first communication device comprising: a second communication device connected to the first communication device via a communication line; and receiving the frame via the communication line.
The first communication device is:
An operation for controlling the operation of dividing the frame into packets, and when a high-priority frame is input during transfer of a low-priority packet, interrupts the high-priority packet even during transfer of the low-priority packet and outputs it to the communication line A frame division management unit for controlling
A packet generator for adding position information and priority information to the packet;
The second communication device is:
A packet decomposing unit that detects position information and priority information of a packet input from the first communication device via a communication line;
A frame transfer system comprising: a frame generation unit configured to combine the packets in units of frames in the order of the position information for each priority detected by the packet decomposition unit.   4. The frame transfer system according to claim 3, wherein the packet generation unit includes a first frame check calculation unit that adds check information to the packet output from the buffer unit. The packet decomposition unit includes a second frame check calculation unit that checks whether there is an error in a frame input via a communication line based on the check information added by the first frame check calculation unit. 4. The frame transfer system according to claim 3, wherein:

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