JP2004297253A - Transmission control apparatus and transmission control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmission control apparatus and transmission control method for processing frames in units of octets, which normally processes the frames even when synchronizing bits are not in the units of octets. <P>SOLUTION: The transmission control apparatus is provided with: a buffer 1; a frame transfer section 2 for applying transfer control to frames in units of octets; a flow limit processing section 3 for inserting a gap period for flow limit between the frames; an output processing section 4 for transmitting the frames; a processing section and an attachment section (not shown); and a check section including a frame length check counter 5, obtains fractions of the bit length of the synchronous bits such as a preamble with respect to the octet unit, and the attachment section attaches attachment information denoting the fractions or excess bits obtained from the fractions to the frames. The output processing section 4 transmits the frames from which the excess bits and the attachment information are deleted on the basis of the attachment information. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a transmission control device and a transmission control method having a configuration for processing a frame to which a synchronization bit is added in octets.
[0002]
[Prior art]
2. Description of the Related Art In a transmission control device having an IP (Internet Protocol) interface, a configuration is known which has a function of mapping a frame from a terminal to a SONET / SDH (Synchronous Optical Network / Synchronous Digital Hierarchy) interface and transmitting the frame. I have. In such a transmission system, means for performing flow control according to QoS (Quality of Service; quality of service) is applied.
[0003]
In the flow rate control based on QoS, a gap period GAP to be inserted between frames is obtained based on information on QoS and a frame length.
GAP = (100 × frame length) ÷ inflow limit value−frame length. Since an Ethernet frame having a length including the preamble is transmitted on the network, it is necessary to determine the frame length including the preamble in order to obtain the gap period GAP.
[0004]
Generally, before performing the flow control, various error checks and performance monitor checks of the received frames are performed. The transmission frame includes a preamble as a synchronization bit, an SFD (Start Flag Delimiter; frame start delimiter), and has a format configuration including address information of a transmission source and a transmission destination, data, check information, and the like. Various checks are performed on the subsequent frame body by SFD detection.
[0005]
Normally, the preamble is 64 bytes (8 octets) including the SFD, and the frame length excluding this preamble is 64 to 1518 bytes (64 octets to 1518 octets). When a VLAN (Virtual Local Area Network) tag or the like is added, the number of bytes of the tag or the like is added as the frame length. Since the normal frame configuration is an octet unit configuration, the frame processing unit has a circuit configuration based on the octet length.
[0006]
FIG. 4 shows a main part of a conventional transmission control device, 41 is a temporary buffer for receiving and temporarily storing an Ethernet frame from a terminal, 42 is a frame transfer unit, 43 is a flow rate restriction processing unit, and 44 is a network. , An output processing unit 45, a frame length check counter 45, an SFD detection unit 46, and an error check unit 47. It should be noted that a processing unit that performs a destination sending process of a frame at a subsequent stage of the output processing unit 44 is omitted in the drawing.
[0007]
The frame length check counter 45 counts all frame lengths including the preamble. Further, the SFD detection unit 46 detects the SFD added next to the preamble and notifies the error check unit 47. The error check unit 47 checks whether the frame length of the frame body after the SFD exceeds a specified maximum value or is shorter than a minimum value. If the check result is good, the frame transfer unit 42 applies a transfer trigger to the frame transfer unit 42, so that the frame transfer unit 42 reads out the frame temporarily stored in the temporary buffer 41 and transfers it to the flow rate restriction processing unit 43.
[0008]
The flow rate restriction processing unit 43 calculates the above-described gap period GAP based on the information on the frame length including the preamble obtained by the frame length check counter 45, and determines the period between the previously transmitted frame and the currently transmitted frame. When the calculated gap period GAP is reached, the output processing unit 44 is notified to transmit the current frame. Thus, the frame can be transmitted to the network in a desired band.
[0009]
The frame configuration includes, for example, a preamble + SFD, an address part AD, a data part, and an FCS (Frame Check Sequence), as schematically shown in FIG. 5A, and is configured in units of octets (8 bits). It has. Therefore, each unit of the transmission control device is also configured to perform processing in octet units, so that the circuit configuration can be simplified.
[0010]
Also, a 7-byte preamble, a 1-byte frame start delimiter, a 6-byte destination address, a 6-byte source address, a 2-byte frame type, 0-1500-byte data, and a 0-46-byte data There is known a method of recognizing an attribute of a data packet from a result of the CRC operation using a frame structure including data padding and a 4-byte CRC and utilizing a CRC operation function (for example, see Patent Document 1). .
[0011]
There is also known a means for setting the length of the preamble to be short when the priority is high, and long when the priority is low, and performing frame transmission corresponding to the priority (for example, Patent Document 2). reference). Also, in order to avoid the problem of being erroneously detected as a preamble again when the same bit pattern as that of the preamble is included, a header including the length information of the frame and the FCS is added to the head of the frame having the preamble next to the preamble. There is also known a means for transmitting data in addition to the above (for example, see Patent Document 3).
[0012]
[Patent Document 1]
JP 2001-7860 A [Patent Document 2]
JP-A-6-252928 [Patent Document 3]
JP 2001-212177 A
[Problems to be solved by the invention]
As described above, the head preamble (including SFD) of an Ethernet frame from the terminal side is generally 64 bits long (8 octets long). Therefore, the transmission control device is configured to process in octets. However, if there is a configuration in which the preamble is missing bits or extra bits are added due to the influence of noise or the like during transmission from the terminal side, or a preamble that is not an octet unit is added from the terminal side and transmitted, an octet unit is used. In the transmission control device, the received frame is transmitted in a state where a surplus bit, which is a fraction with respect to an octet unit, is added to the end of the received frame.
[0014]
For example, as shown in (B), when a frame having a normal preamble in octet units shown in (A) of FIG. By reading the data in units of octets from, the surplus bits of (8-a) bits are added to the end of the frame. As a result, there is a problem that a problem occurs in a processing unit that performs layer 2 processing or the like at a subsequent stage of the output processing unit 44. Further, there is a problem that the calculation of the gap period GAP in the flow rate restriction processing unit 3 becomes inaccurate.
[0015]
However, conventionally, when the preamble length changes, it is known that the preamble length is changed in accordance with the priority. However, the frame transmission processing in a system having a function of processing in octets is known. In the process, no problem has been raised when the preamble is not octet-length. A configuration for processing a frame including a preamble having a length other than the length of an octet unit is more complicated than a configuration of processing a frame in octet units, and has a problem of increasing costs.
An object of the present invention is to perform frame processing in units of octets and to perform normal processing even when the preamble is not in units of octets.
[0016]
[Means for Solving the Problems]
Referring to FIG. 1, the transmission control apparatus according to the present invention is a transmission control apparatus that receives and processes a preamble including a frame start delimiter (SFD), that is, a frame to which a synchronization bit is added. A buffer 1 for temporarily storing received frames, a frame transfer unit 2 for reading and transferring frames from the buffer 1 in octets, and determining whether a synchronization bit length is in octets. A check unit including a preamble length check counter 8 or the like for obtaining a fraction with respect to the length of the octet unit or a surplus bit by processing the octet based on the fraction, and information indicating the fraction or the surplus bit obtained by the check unit. An additional unit that adds additional information in octet length to the frame, and the additional unit adds the additional information to the frame. Based on the additional information comprises delete the extra bits and the additional information, and the output processing unit 4 for transmitting the frame, and a processing unit for transmitting processed frames from the output processing unit 4.
[0017]
Further, a flow restriction processing unit 3 is provided at a stage preceding the output processing unit 4, and the flow restriction processing unit 3 calculates a reception frame length based on information indicating a fraction or an extra bit of a synchronization bit in octet units by the check unit. And calculating a gap period to be inserted between frames.
[0018]
According to the transmission control method of the present invention, a preamble including a frame start delimiter (SFD), that is, a frame to which a synchronization bit is added is received and temporarily stored in a buffer 1, and read out and controlled in octets for transmission control. In the method, the data is read out from the buffer 1 in octets, and the length of the synchronization bit is counted to obtain a fraction with respect to the length in octets. For example, the preamble length before SFD by the SFD detection unit 6 is counted by a preamble length counter, and the count value is divided by 8 to make the remainder a fraction. Also, based on the fraction, a surplus bit is obtained by processing in octets. The additional unit in octets including the information indicating the fraction or the surplus bits is added to the frame in the adding unit, and the output processing unit deletes the surplus bits and the additional information based on the additional information and sends the frame. Is included.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is an explanatory diagram of an embodiment of the present invention. Reference numeral 1 denotes a buffer for receiving and temporarily storing an Ethernet frame from a terminal (not shown) (corresponding to a conventional temporary buffer in FIG. 4). 2 is a frame transfer unit, 3 is a flow restriction processing unit, 4 is an output processing unit that sends an Ethernet frame to a network side (not shown), 5 is a frame length check counter, 6 is an SFD detection unit, and 7 is an error The check section 8 indicates a preamble length check counter. The preamble length check counter 8 may be a check unit or a check unit including the SFD detection unit 6, or the frame length check counter 5, the SFD detection unit 6, the error check unit 7, the preamble length check counter 8, and the like. Can be included in the check section. Although a processing unit provided at a subsequent stage of the output processing unit 4 is not shown, and an adding unit for adding additional information to a frame is not shown, it can be provided in, for example, the frame transfer unit 2.
[0020]
The Ethernet frame received from the terminal is a preamble including a frame start delimiter (SFD), that is, an Ethernet frame to which a synchronization bit by an electric signal is added, and is sequentially stored in the buffer 1. Then, in the process, the frame length check counter 5 starts counting from the leading preamble and obtains the frame length. The error check unit 7 checks whether the frame length is equal to or longer than a predetermined range, that is, equal to or longer than a predetermined minimum length. If the check result indicates that the frame length is within a predetermined range, a transfer trigger is applied to the frame transfer unit 2. Accordingly, the frame transfer unit reads and transfers the frames stored in the buffer 1 in octets. The SFD detection unit 6 is configured to be able to detect the SFD of a frame even when the preamble is not in octets.
[0021]
The preamble length check counter 8 counts the preamble from the beginning, finds a preamble length based on the SFD detection signal from the SFD detection unit 6, and divides the preamble length by 8 to find a fraction (remainder). That is, it is determined whether or not the preamble has a length of an octet unit and a fraction thereof. In the case of octet length, the fraction is 0. For example, when the length of the preamble + SFD shown in FIG. 5B includes a fraction a (bits) with respect to the length of an octet, the processing at the end of the octet causes the rear end of the frame to be at the end of FIG. (B), a state in which (8-a) extra bits are added. Therefore, by obtaining the fraction, the surplus bits can be obtained from the fraction.
[0022]
The information indicating the fraction or the surplus bits is added to, for example, a rear end of the frame as additional information having a length of an octet unit. The additional unit for adding the additional information to the frame can be provided between the buffer 1 and the output processing unit 4, and can be provided, for example, in the frame transfer unit 2. The frame transfer unit 2 reads data from the buffer 1 in octets and performs a transfer process. The flow rate control unit 3 controls the transmission interval of the transferred frames. The gap period GAP is calculated as GAP = (100 × frame length) ÷ inflow limit value−frame length, and transferred to the output processing unit 4.
[0023]
In this case, the frame length is calculated as a frame length that does not include the surplus bits. For this purpose, a fraction based on the above-described additional information is identified, and (1 octet−fraction) = surplus bits is obtained from the entire frame length, or a preamble is calculated. Based on fraction information or surplus bit information from the check unit including the length check counter 8, the actual frame length is obtained by removing the surplus bits from the entire frame length, and the above-described gap period is calculated. Therefore, in a configuration in which processing is performed in units of octets, when the terminal side transmits a frame including synchronization bits that are not in units of octets, or when a synchronization bit is added or missing due to the influence of noise in the transmission process, the synchronization is not performed. Even when the bit includes a fraction with respect to an octet unit, since the flow rate limiting control can be performed based on the actual frame length, the accuracy of the bandwidth control transmitted from the transmission control device to the transmission network can be improved.
[0024]
FIG. 2 is an explanatory diagram of the internal transfer frame. When the synchronization bit of the preamble + SFD includes a fraction a bit with respect to the length of the octet, the data is read out from the buffer 1 in octets and transferred as described above. As a result, an extra bit (8-a) is added after the FCS. The check unit obtains the synchronization bit length, divides by 8, and obtains the remaining fraction a bits, and the addition unit uses the information of the fraction a bits as additional information HD having a length in octet units, or A surplus bit is obtained from the obtained fraction, and the information of this surplus bit is added as additional information HD in octet units, for example, after the surplus bit of (8-a) as shown in the figure. If the synchronization bit length is a length in octets, the fraction is 0 and the surplus bits are also 0. The information of the fraction of 0 or surplus bits is represented by additional information.
[0025]
Therefore, at least the frame transferred to the output processing unit 4 has the additional information HD added thereto, and the flow rate restriction processing unit 3 determines whether the additional information HD or the fraction information from the check unit by the preamble length check counter 8 or the like. , The gap period GAP inserted between the frames can be calculated.
[0026]
Further, the output processing unit 4 identifies the additional information HD, finds extra bits from the fractional information, deletes extra bits added to the rear end of the frame based on the information indicating the extra bits, and The additional information HD is deleted, the frame in the state received by the buffer 1 is restored, and the frame is transferred to the next processing unit (not shown). In the processing unit, the layer 2 processing, for example, the surplus bits are deleted. As a result, the frame is transmitted by performing a frame check sequence process, an output port search process based on the MAC address, and the like.
[0027]
FIG. 3 is an explanatory view of another embodiment of the present invention, in which 11 is a buffer, 12 is a frame transfer unit, 13 is a flow restriction processing unit, 14 is an output processing unit, 15 is a frame length check counter, and 16 is SFD. A detection unit, 17 is an error check unit, 18 is a preamble length check counter, and 19 is a preamble generation unit (synchronization bit generation unit).
[0028]
The buffer 11, the frame length check counter 15, the SFD detection unit 16, the error check unit 17, and the preamble length check counter 18 have the same function as the configuration of the same name shown in FIG. The + SFD synchronization bit calculates a fraction with respect to the length of the octet unit, and the additional information HD (see FIG. 2) of the octet unit length of the information indicating the fraction or the surplus bits calculated from the fraction is added to the addition unit (not shown). ), The flow rate restriction processing unit 13 determines the actual frame length based on the information of the fraction based on the additional information HD or the information indicating the fraction or the surplus bits from the check unit such as the preamble length check counter 18. Then, the gap period GAP between the frames is obtained, and the output processing unit 14 is provided with the gap period GAP after the gap period GAP. To transfer the beam.
[0029]
The output processing unit 14 outputs a preamble generation unit 19 at the beginning of the frame body in which the extra information, the surplus bits based on the extra bit information, the extra information, and the first synchronization bit are deleted. A synchronization bit of the generated preamble + SFD is added. The synchronization bit is set to a predetermined length, for example, a length of an octet unit, and is added to the head of the frame body, so that the frame is transferred to the next-stage processing unit as a frame configuration having a length of an octet unit.
[0030]
Therefore, from the transmission control device of this embodiment, even if the synchronization bits of the frame received from the terminal are not octet-length, the synchronization control bits of octet-length are added and transmitted. On the receiving side, a frame receiving process can be performed by a configuration in which processing is performed in octets. It should be noted that the preamble generation unit 19 may be configured to generate a synchronization bit having a preset length other than the octet length in accordance with the processing configuration on the receiving side.
[0031]
(Supplementary Note 1) In a transmission control device for receiving and processing a frame with a synchronization bit added thereto, a buffer for temporarily storing the received frame, and reading and transferring the frame from the buffer in octet units A frame transfer unit to be processed, a check unit for determining whether or not the length of the synchronization bit is a length in octet units and a fraction for the length of the octet unit or a surplus bit based on the fraction, and a check unit An addition unit for adding the additional information of the length in octets including information indicating the fraction or the surplus bits obtained by the addition unit to the frame, and the extra bits based on the additional information added to the frame by the addition unit. An output processing unit that deletes the additional information and sends a frame; and a processing unit that sends a frame from the output processing unit. Transmission control apparatus according to claim and.
[0032]
(Supplementary Note 2) A flow restriction processing unit is provided at a stage preceding the output processing unit, and the flow restriction processing unit is a unit for calculating the fraction of the synchronization bit in octets by the check unit or information of surplus bits obtained based on the fraction. 2. The transmission control device according to claim 1, further comprising: obtaining a length of a received frame based on the above formula, and calculating a gap period to be inserted between the frames.
(Supplementary Note 3) The output processing unit may generate a predetermined length of a frame from which a surplus bit corresponding to a difference between the fraction and one octet and the additional information and the synchronization bit are deleted based on the additional information. 2. The transmission control device according to claim 1, further comprising a synchronization bit generation unit for generating and adding a synchronization bit.
[0033]
(Supplementary Note 4) In a transmission control method for receiving a frame to which a synchronization bit is added, temporarily storing the frame in a buffer, reading the frame in octets, and controlling the transmission, the frame is read out in octets from the buffer, and the synchronization is read. The length of the bit is counted to obtain a fraction with respect to the length of the octet unit, and additional information in octet units including the fraction or information indicating the extra bits obtained based on the fraction is added to the frame in the adding unit. A transmission control method comprising: removing, in the output processing unit, the surplus bits and the additional information based on the additional information and transmitting the information.
[0034]
(Supplementary Note 5) The length of the synchronization bit is read out from the buffer in units of octets, a fraction of the length of the octet is obtained, and information indicating the fraction or surplus bits obtained based on the fraction is obtained. The additional information in octet units is added to the frame in the adding unit, the fraction is recognized by the additional information in the flow restriction processing unit, and the gap between the frames is determined based on the frame length excluding the surplus bits. The transmission control method according to claim 4, further comprising a step of calculating a period and transferring the frame to the output processing unit after the gap period.
(Supplementary Note 6) A predetermined-length synchronization bit generated by a synchronization bit generation unit is added to the beginning of the frame body in which the synchronization bit is deleted together with the surplus bits and additional information in the output processing unit and transmitted. 6. The transmission control method according to claim 4 or 5, further comprising the step of:
[0035]
【The invention's effect】
As described above, the present invention includes the buffer 1, the frame transfer unit 2, and the output processing unit 4 configured to perform processing in octets, and includes the flow rate restriction processing unit 3 and temporarily stores the data in the buffer 1. A fraction with respect to the length of the octet unit of the synchronization bit of the preamble at the beginning of the frame + the SFD is obtained, and additional information including this fraction or information indicating surplus bits obtained based on this fraction is added to the frame. Is for transferring a frame in which (8−fraction) = the surplus bits of the surplus bits and the additional information are deleted to the processing unit based on the additional information. If the synchronization bit is not octet-length, However, correct processing can be performed with a configuration in units of octets, and the frame can be transmitted as a frame from which excess bits have been deleted.
[0036]
In addition, it is possible to generate and add a synchronization bit identical to the synchronization bit of the received frame or a new octet-length synchronization bit in accordance with the configuration of the receiving side. Also, the flow rate restriction processing in the flow rate restriction processing unit 3 can be performed based on the actual frame length based on the fraction information, and therefore, there is an advantage that accurate flow rate control can be performed.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of one embodiment of the present invention.
FIG. 2 is an explanatory diagram of an internal transfer frame.
FIG. 3 is an explanatory diagram of another embodiment of the present invention.
FIG. 4 is an explanatory diagram of a conventional transmission control device.
FIG. 5 is an explanatory diagram of a frame configuration.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Buffer 2 Frame transfer part 3 Flow rate restriction part 4 Output processing part 5 Frame length check counter 6 SFD detection part 7 Error check part 8 Preamble length check counter

Claims (3)

In a transmission control device for receiving and processing a frame to which a synchronization bit has been added, and transmitting the frame,
A buffer for temporarily storing the received frame;
A frame transfer unit that reads the frame from the buffer in octet units and performs transfer processing;
A checking unit for determining whether or not the length of the synchronization bit is the length of an octet unit and a fraction for the length of the octet unit or a surplus bit based on the fraction;
An adding unit that adds, to the frame, additional information having a length in octets including information indicating the fraction or surplus bits obtained by the check unit;
An output processing unit that deletes the surplus bits and the additional information based on the additional information added to the frame by the adding unit, and transmits a frame;
A transmission unit for transmitting a frame from the output processing unit. A flow restriction processing unit is provided at a stage preceding the output processing unit, and the flow restriction processing unit is based on information of a fraction or an excess bit obtained based on the fraction for the octet unit of the synchronization bit by the check unit. 2. The transmission control device according to claim 1, wherein the transmission control device has a configuration in which a length of a received frame is obtained and a gap period to be inserted between the frames is calculated. In a transmission control method of receiving a frame with a synchronization bit added, temporarily storing the frame in a buffer, and reading and controlling transmission by octet unit,
The length of the synchronization bit is read out from the buffer in units of octets, and the length of the synchronization bit is counted to obtain a fraction with respect to the length of the octet, and the octet unit including information indicating the fraction or the surplus bits obtained based on the fraction is obtained. A transmission control step of adding the additional information to the frame in an adding unit, and deleting and transmitting the surplus bits and the additional information based on the additional information in an output processing unit. Method.

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