JP4074992B2 - Transmission control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a transmission control apparatus having a configuration for processing a frame synchronization bit is added in octets.
[0002]
[Prior art]
It is known that a transmission control apparatus having an IP (Internet Protocol) interface has a function of mapping and transmitting a frame from a terminal side to a SONET / SDH (Synchronous Optical Network / Synchronous Digital Hierarchy) interface. Yes. In such a transmission system, means for performing flow rate control according to QoS (Quality of Service) is applied.
[0003]
In this flow rate control by QoS, a gap period GAP to be inserted between frames is obtained based on information of QoS and frame length. The gap period GAP is, for example,
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 determine the gap period GAP.
[0004]
Generally, before performing flow control, various error checks and performance monitor checks of received frames are performed. Further, the transmission frame includes a preamble as a synchronization bit, an SFD (Start Flag Delimiter), and has a format configuration including address information, data, check information, and the like of the transmission source and the transmission destination. Various checks are performed on the subsequent frame body by SFD detection.
[0005]
Normally, the preamble includes 64 bytes (8 octets) including the SFD, and the frame length excluding the 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 such as the tag is added as the frame length. Since the normal frame configuration is a configuration in units of octets, 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 apparatus, 41 is a temporary buffer for receiving and temporarily storing an Ethernet frame from the terminal side, 42 is a frame transfer unit, 43 is a flow rate limiting processing unit, and 44 is a network. An output processing unit to be sent to the side, 45 is a frame length check counter, 46 is an SFD detection unit, and 47 is an error check unit. Note that a processing unit that performs destination transmission processing of a frame subsequent to the output processing unit 44 is not shown.
[0007]
The frame length check counter 45 counts all frame lengths including the preamble. The SFD detection unit 46 detects the SFD added next to the preamble and notifies the error check unit 47 of it. 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 the minimum value. If the check result is satisfactory, a transfer trigger is added to the frame transfer unit 42 so that the frame transfer unit 42 reads the frames temporarily stored in the temporary buffer 41 and transfers them to the flow rate restriction processing unit 43.
[0008]
The flow restriction processing unit 43 calculates the gap period GAP described above based on the frame length information including the preamble obtained by the frame length check counter 45, and the period between the previously sent frame and the currently sent frame is calculated. When the calculated gap period GAP is reached, the output processing unit 44 is notified to transmit the current frame. Thereby, the frame can be transmitted to the network side in a desired band.
[0009]
The frame configuration includes, for example, a preamble + SFD, an address portion AD, a data portion, and an FCS (Frame Check Sequence), as schematically shown in FIG. 5A, and is configured in units of octets (8 bits). It is what has. Therefore, each part of the transmission control device is configured to process in units of octets, and 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 to 1500 bytes of data, and 0 to 46 bytes of data There is known a method of recognizing an attribute of a data packet from a CRC calculation result by using a CRC calculation function by using a data padding and a 4-byte CRC frame structure (see, for example, Patent Document 1). .
[0011]
There is also known a means for transmitting a frame corresponding to a priority by setting the length of the preamble to be short when the priority is high and long when the priority is low (for example, Patent Document 2). reference). If the same bit pattern as the preamble is included, the header including the length information of the frame and the FCS is added to the beginning of the frame having the preamble in order to avoid the problem of erroneous detection as a preamble again. There is also known a means for transmitting in addition (see, for example, Patent Document 3).
[0012]
[Patent Document 1]
JP 2001-7860 A [Patent Document 2]
Japanese Patent Application Laid-Open No. 6-252928 [Patent Document 3]
Japanese Patent Laid-Open No. 2001-211177
[Problems to be solved by the invention]
The preamble (including SFD) at the beginning of the Ethernet frame from the terminal side is generally 64 bits long (8 octets long) as described above. Therefore, the transmission control apparatus is configured to process in units of octets. However, if there is a configuration in which preamble bits are missing 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 in octet units is added from the terminal side, transmission is performed in octet units. In the transmission control apparatus that processes the above, a surplus bit that is a fraction with respect to the octet unit is added to the end of the received frame and sent out.
[0014]
For example, when a normal octet preamble shown in (A) of FIG. 5 has a fraction a bit with respect to the octet length as shown in (B), the temporary buffer 41 Is read out in octets, so that (8-a) bits of extra bits are added to the rear end of the frame. As a result, there is a problem that inconvenience occurs in a processing unit that performs layer 2 processing and the like subsequent to 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]
Conventionally, however, it is known that the preamble length changes in accordance with the priority when the preamble length changes, but frame transmission processing in a system having a function of processing in units of octets. There are no issues raised in the process when the preamble is not octets long. Such a configuration for processing a frame including a preamble that is not in octet length is more complicated than the configuration in which processing is performed in octet units, and there is a problem that costs are increased.
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]
The transmission control apparatus of the present invention will be described with reference to FIG. 1. In the transmission control apparatus for receiving and processing a preamble including a frame start delimiter (SFD), that is, a frame to which a synchronization bit is added, A buffer 1 that temporarily stores the received frames, a frame transfer unit 2 that reads and processes the received frame from the buffer 1 in octets, and a synchronization bit length of the received frame is a length in octets And a check unit including a preamble length counter 8 that obtains a fraction to the length of the octet unit or a surplus bit for the octet unit based on the fraction, and information indicating the fraction or the surplus bit obtained by the check unit and adding unit for adding length information octets added to the received frame including the check A flow rate restriction processing unit 3 for calculating the gap period to be inserted between frames by determining the received frame length based on the fraction of the octet unit length obtained by the unit or the information of the surplus bits obtained based on this fraction; An output processing unit 4 for performing a transfer process on the frame in which the additional information added to the received frame transferred through the flow rate restriction processing unit 3 and the surplus bits are deleted, with a gap period obtained by the flow rate restriction processing unit 3 ; And a processing unit that sends out a frame from the output processing unit 4 to the transmission network .
[0017]
Also, a flow rate limiting processing unit 3 is provided in front of the output processing unit 4, and this flow rate limiting processing unit 3 obtains the received frame length based on the information indicating the fraction of the synchronization bit by the check unit or the surplus bit. Thus, the gap period to be inserted between frames is calculated.
[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, temporarily stored in the buffer 1, and read and controlled in units of octets. In the method, data is read from the buffer 1 in octets, the length of the synchronization bits is counted, and a fraction with respect to the length in octets is obtained. For example, the preamble length before SFD by the SFD detector 6 is counted by a preamble length counter, and the count value is divided by 8 to make the remainder a fraction. Based on this fraction, surplus bits are obtained by processing in units of octets. A process of adding additional information in units of octets including information indicating this fraction or surplus bits to the frame in the adding section, and the output processing section deleting the surplus bits and the additional information based on this additional information and transmitting it Is included.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is an explanatory diagram of an embodiment of the present invention. 1 is a buffer for receiving and temporarily storing an Ethernet frame from a terminal (not shown) (corresponding to the conventional temporary buffer in FIG. 4). 2 is a frame transfer unit, 3 is a flow rate restriction processing unit, 4 is an output processing unit that sends an Ethernet frame to the network side (not shown), 5 is a frame length check counter, 6 is an SFD detection unit, and 7 is an error. A check unit 8 indicates a preamble length check counter. The preamble length check counter 8 may be a check unit including the check unit or 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, Can be used as a check section. Further, the processing unit provided at the subsequent stage of the output processing unit 4 is not shown, and the adding unit for adding additional information to the frame is omitted, but can be provided in the frame transfer unit 2, for example.
[0020]
The Ether frame received from the terminal side is sequentially stored in the buffer 1 as a preamble including a frame start delimiter (SFD), that is, an Ether frame to which a synchronization bit by an electric signal is added. In this process, the frame length check counter 5 starts counting from the first preamble and obtains the frame length. The error check unit 7 checks whether the frame length is a predetermined range, that is, whether it is longer than a specified minimum length or shorter than a maximum length. If the frame length is within the predetermined range as a result of the check, a transfer trigger is added to the frame transfer unit 2. Thereby, the frame transfer unit reads and transfers the frames accumulated in the buffer 1 in units of octets. The SFD detection unit 6 is configured to be able to detect the SFD of the frame even when the preamble is not in octets.
[0021]
The preamble length check counter 8 counts the preamble from the beginning, obtains the preamble length based on the SFD detection signal from the SFD detector 6, and divides the preamble length by 8 to obtain a fraction (remainder). That is, whether or not the preamble is octet length and its fraction are obtained. If the length is in octets, 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 in octets, the rear end of this frame is displayed in FIG. (B) of (8-a) bits are added as shown in (B) of FIG. Therefore, by obtaining the fraction, surplus bits can be obtained from this fraction.
[0022]
Information indicating this fraction or surplus bits is added to, for example, the rear end of the frame as additional information having a length in octets. The adding 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 in the frame transfer unit 2, for example. The frame transfer unit 2 reads data from the buffer 1 in units of octets and performs transfer processing. The flow rate restriction processing 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, it is calculated as a frame length that does not include surplus bits. For this purpose, the fraction by the above-mentioned additional information is identified, and (1 octet-fraction) = surplus bits from the total frame length, or the preamble. Based on the fraction information or surplus bit information from the check unit including the length check counter 8, the actual frame length is obtained by excluding this surplus bit from the total frame length, and the above-described gap period is calculated. Therefore, in the configuration in which processing is performed in units of octets, when the terminal side sends a frame including synchronization bits that are not in octets, or because of synchronization bit addition or omission due to the influence of noise in the transmission process, etc. Even when the bit includes a fraction with respect to the octet unit, the flow rate restriction control can be performed based on the actual frame length, so that it is possible to improve the accuracy of the band control transmitted from the transmission control device to the transmission network.
[0024]
FIG. 2 is an explanatory diagram of an internal transfer frame. When the synchronization bit of the preamble + SFD includes a fractional bit a with respect to the length of the octet, it is read out from the buffer 1 and transferred in units of octets as described above. Thus, (8-a) surplus bits are added after the FCS. The check unit obtains the synchronization bit length and divides by 8 to obtain a remainder a bit. In the addition unit, the fraction a bit information is used as additional information HD having a length in octets, or A surplus bit is obtained from the obtained fraction, and the information on the surplus bit is added as additional information HD in octets, for example, after the surplus bit of (8-a) as shown in the figure. Note that when the synchronization bit length is in octets, the fraction is 0 and the surplus bits are also 0. This fraction of 0 or surplus bit information is represented by additional information.
[0025]
Therefore, the additional information HD is added to at least the frame transferred to the output processing unit 4, and the flow rate limiting processing unit 3 uses this additional information HD or information on the fraction from the check unit by the preamble length check counter 8 or the like. Based on the above, the gap period GAP inserted between frames can be calculated.
[0026]
The output processing unit 4 identifies the additional information HD, obtains a surplus bit from the fractional information, deletes the surplus bit in a state added to the rear end of the frame based on the information indicating the surplus bit, and The additional information HD is deleted, the frame received by the buffer 1 is restored and transferred to the processing unit (not shown) in the next stage, and the layer 2 processing, for example, surplus bits are deleted in the processing unit. Therefore, the frame is transmitted by performing a frame check sequence process, an output port search process using a MAC address, and the like.
[0027]
FIG. 3 is an explanatory diagram of another embodiment of the present invention, in which 11 is a buffer, 12 is a frame transfer unit, 13 is a flow rate limiting processing unit, 14 is an output processing unit, 15 is a frame length check counter, and 16 is an 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 functions as the components having the same names shown in FIG. The fraction of the + SFD synchronization bit with respect to the length in octets is obtained, and additional information HD (see FIG. 2) of the length in octets of the information indicating the surplus bits obtained from this fraction or the fraction is added (not shown). ) And the flow rate restriction processing unit 13 determines the actual frame length based on the fraction information by the additional information HD or the information indicating the fraction or surplus bits from the check unit such as the preamble length check counter 18. The gap period GAP between the frames is obtained, and the output processing unit 14 sets the gap period GAP and sets the frame period GAP. To transfer the beam.
[0029]
The output processing unit 14 uses the preamble generation unit 19 at the head of the frame body from which the surplus bits by the additional information HD or the surplus bits by the surplus bit information, the additional information, and the head synchronization bit are deleted. The generated preamble + SFD synchronization bit is added. The synchronization bit is set to a predetermined length, for example, an octet unit length, and is added to the head of the frame body to transfer the frame configuration to the next stage as a frame configuration having an octet unit length.
[0030]
Therefore, from the transmission control device of this embodiment, even if the synchronization bit of the frame received from the terminal is not in octet length, the synchronization bit of octet length is added and transmitted, On the receiving side, frame reception processing can be performed by a configuration in which processing is performed in units of octets. The preamble generation unit 19 can also be configured to generate a synchronization bit having a preset length that is not a length in octets, corresponding to the processing configuration on the reception side.
[0031]
(Supplementary note 1) In a transmission control apparatus for receiving and transmitting a frame with a synchronization bit added, a buffer for temporarily storing the received frame, and reading and transferring the frame from the buffer in units of octets A frame transfer unit to be processed, a check unit for determining whether the length of the synchronization bit is in octets and a fraction with respect to the length in octets or a surplus bit based on the fraction, and the check unit An additional unit that adds additional information of octet length including information indicating the fraction or surplus bit obtained by the step, and the surplus bits and the extra bits based on the additional information added to the frame by the additional unit An output processing unit that deletes the additional information and sends out a frame; and a processing unit that sends out a frame from the output processing unit Transmission control apparatus according to claim and.
[0032]
(Supplementary Note 2) A flow rate limiting processing unit is provided in front of the output processing unit, and the flow rate limiting processing unit is a fraction of the synchronization bit by the check unit with respect to an octet unit, or information on surplus bits obtained based on the fraction. The transmission control apparatus according to appendix 1, wherein a transmission frame length is calculated based on the received frame length and a gap period inserted between the frames is calculated.
(Supplementary Note 3) The output processing unit has a predetermined length for a frame in which the surplus bits corresponding to the difference between the fraction and 1 octet, the additional information, and the synchronization bit are deleted based on the additional information. The transmission control apparatus according to appendix 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 with a synchronization bit added, temporarily storing it in a buffer, reading it in octets, and controlling transmission, reading from the buffer in octets, and The bit length is counted to obtain a fraction relative to the length in octets, and additional information in octets including information indicating the surplus bits obtained based on the fraction or the fraction is added to the frame in the addition unit. And a transmission control method comprising: a step of deleting and transmitting the surplus bits and the additional information based on the additional information in the output processing unit.
[0034]
(Supplementary Note 5) Reading from the buffer in octets, counting the length of the synchronization bit to obtain a fraction with respect to the length in octets, and indicating the fraction or the surplus bit obtained based on the fraction Including additional information in units of octets to be added to the frame in the adding unit, the flow rate limiting processing unit recognizing the fraction by the additional information, and based on the frame length excluding the surplus bits, the gap between the frames The transmission control method according to supplementary note 4, including a step of calculating a period and transferring a frame to the output processing unit with the gap period.
(Supplementary note 6) A synchronization bit having a predetermined length generated by the synchronization bit generation unit is added to the head of the frame body from 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 appendix 4 or 5, characterized by including a process of
[0035]
【The invention's effect】
As described above, the present invention includes the buffer 1 configured to process in units of octets, the frame transfer unit 2, and the output processing unit 4, and also includes the flow rate limiting processing unit 3, and is temporarily stored in the buffer 1. A fraction with respect to the length of the first preamble of the frame + the synchronization bit of the SFD in units of octets is obtained, additional information including information indicating this fraction or the surplus bit obtained based on this fraction is added to the frame, and the output processing unit 4 Is based on this additional information, (8-fraction) = a frame in which the surplus bits of the surplus bits and the additional information are deleted is transferred to the processing unit, and the synchronization bit is not in octet length However, correct processing is possible with a configuration in units of octets, and the surplus bits in that case can be sent out as a deleted frame.
[0036]
Corresponding to the configuration on the receiving side, a synchronization bit identical to the synchronization bit of the received frame or a synchronization bit having a new octet length can be generated and added. Further, the flow rate limiting process in the flow rate limiting 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 is possible.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of an 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 apparatus.
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 | limiting part 4 Output processing part 5 Frame length check counter 6 SFD detection part 7 Error check part 8 Preamble length check counter

Claims (1)

In a transmission control device for receiving and processing a frame with a synchronization bit added to the transmission network ,
A buffer for temporarily storing the received frame;
A frame transfer unit that reads out the frame from the buffer in units of octets and performs transfer processing;
A check unit that determines whether or not the length of the synchronization bit is a length in octets and a fraction with respect to the length in octets or a surplus bit based on the fraction;
And adding unit for transferring treated with length in octets of the additional information of the length of the fractional or octets including information indicating the surplus bit is added to the frame determined by said checking unit,
A flow rate limiting processing unit for calculating a gap period to be inserted between frames by obtaining the received frame length based on the additional information added to the frame by the adding unit;
Output processing unit for transferring a frame to delete the excess bits and the additional information obtained on the basis of the additional information added to the frame by the adding unit, at the gap period calculated by the flow rate limit processing unit When,
A transmission control device comprising: a processing unit that transmits a frame from the output processing unit to a transmission network .

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