CN113993010B - Efficient Xepon olt downlink transmission control method - Google Patents

Abstract

The invention relates to the technical field of data transmission, in particular to a high-efficiency Xeponol downlink transmission control method, wherein a speed control module is used for maintaining a data variable V, judging a V value, inserting an IDLE N1 at a high speed when V is less than or equal to a threshold M1, and updating the variable V; and continuously judging the V value, entering a waiting state when V is larger than the threshold value M1 and is larger than or equal to the threshold value M2, inputting data continuously under the waiting state, outputting data continuously, continuously reducing V, judging whether data PAYLOAD to be sent exist or not when the threshold value M1 is smaller than or equal to the threshold value M2, reading the data PAYLOAD to be sent by the front-stage module, and inserting the IPG after the end of the PAYLOAD is read. And meanwhile, the special interface descriptor is set to ensure that the IPG between the downlink data packets can reach the minimum value. The invention has the advantages of stable control of the output data rate, less IDLE as much as possible, and full increase of the resource utilization rate while not needing too much resources.

Description

Efficient Xepon olt downlink transmission control method

Technical Field

The invention relates to the technical field of data transmission, in particular to a high-efficiency Xepon olt downlink transmission control method.

Background

The Xepon olt (optical line terminal ) refers to epon olt supporting a rate of 10g, and the Xepon olt downlink transmits data to all onu (Optical Network Unit ) in a broadcast form, and needs to ensure continuous transmission of downlink data, and in the case of no data payoad (referring to a normal ethernet packet, which is a valid data portion, from dmac to crc check code end, and no preamble is included), continuous transmission of downlink data needs to be ensured by transmitting IDLE (IDLE indicates invalid data filled when no packet is transmitted, IDLE data).

olt the simple basic principle is that eth data is obtained from the previous stage, and after encapsulation according to the frame format specified by the protocol is completed, the data is sent to onu, onu, and the eth data packet is also analyzed according to the protocol, and then the ethernet layer processing is performed. olt and onu are connected by passive optical fibers. A plurality of simplified olt data sending side schematic diagrams of onu may be hung under olt, as shown in fig. 2, where the data reading module is mainly responsible for reading data from the preceding module, generating descriptors or sending the data to the data processing module, where the processing in the data processing module is complex, including performing processes such as encoding and scrambling of a data format according to the 802.3 protocol, where the data processing module includes a part of buffering for buffering data to absorb delays existing during data processing, and the final data sending module performs egress rate conversion according to the 802.3 protocol, where the part still includes a part of buffering.

The downlink of the Xepon olt system needs continuous data transmission, so that the interruption cannot be ensured, and often, in order to ensure the internal data processing efficiency, the data input rate at the interface entrance is larger than the data transmission rate of the outlet, so that the situation that the flow rate is too high when data is to be transmitted is caused, and under different data flows, if the excessive burst flows are absorbed by means of buffering, the system needs to consume larger resources. If the control is performed by the back pressure of the buffer, too many IDLE are needed to be inserted in the case of no data transmission, so that the interruption is prevented, and the channel is basically in a back pressure congestion state, thereby influencing the downlink data transmission efficiency.

On the other hand, according to the 802.3 protocol, the olt internal interface is in the form of xgmii, and the minimum IPG between two packets can reach 5 bytes. The primary and packet lengths are related, and most systems tend to handle more than this value for the IPG between two packets, which does not maximize downstream traffic utilization. Reducing the data transmission efficiency.

Disclosure of Invention

The invention provides a high-efficiency Xepon olt downlink transmission control method, which ensures that the IPG between downlink data packets can reach the minimum value, and simultaneously controls the output data rate to be stable without too much resources, and inserts fewer IDLE as much as possible.

In order to achieve the purpose of the invention, an efficient Xepon olt downlink transmission control method comprises the following steps:

1) The speed control module is used for maintaining a data variable V, judging a V value, inserting an IDLE N1 at a high speed when the V value is less than or equal to a threshold value M1, and updating the variable V;

2) Continuously judging the V value, when V is larger than the threshold value M1 and V is larger than or equal to the threshold value M2, entering a waiting state, inputting data continuously under the waiting state, outputting data continuously, continuously reducing V, judging whether data PAYLOAD to be sent exist or not when the threshold value M1 is smaller than or equal to the threshold value M2, if yes, jumping to the step 3), and if not, jumping to the step 4);

3) Reading data PAYLOAD to be sent by a front-stage module, updating V, and when V is judged to be more than or equal to a threshold M2, entering a waiting state, and updating V; otherwise, continuing to read the PAYLOAD, updating V, and inserting the IPG after the end of the data PAYLOAD is read;

4) And the IDLE N2 is inserted at a low speed, so that continuous data input is ensured, and V is updated.

As an optimization scheme of the invention, the IPG is inserted according to the length of the data packet by a minimum principle, and the minimum IPG calculation method comprises the following steps: the packet length is divided by 4 to obtain a remainder t, and 8-t represents the inserted IPG length.

As an optimization scheme of the invention, the data variable V of the speed control module is the data quantity C in the link from the data input to the last exit transmission under the fixed system processing clock frequency, the data quantity C is equal to the data quantity to be transmitted minus the data quantity transmitted by the exit, wherein the data to be transmitted includes: IDLE N1, IDLE N2, data payoad to be transmitted and the overhead of the preamble, IPG and fec.

As an optimization scheme of the invention, data interface marks IDLE_FLAG, DB and PB are set, the IDLE_FLAG is used for indicating whether the current data is IDLE, and complete data description information is expressed by combining a data byte variable DB and a PAYLOAD byte variable PB.

The invention has the positive effects that: 1) The invention can provide complete data information under the condition of ensuring the minimum IPG insertion through the specific interface descriptor, and can ensure the normal encoding of spliced data by the subsequent modules. After the interface descriptor is defined in advance, the PAYLOAD length PB is used for special processing of PAYLOAD in a subsequent data processing module, DB is convenient for calculation of the rate module, when the input data quantity is calculated, only the data length DB is needed to be considered, the DB is needed to be considered for subsequent data splicing conversion, and 4-byte integer multiple splicing calculation is more convenient.

2) The rate control ensures that the whole system is not cut off, and meanwhile, excessive data is not needed to be cached by too much resources, so that the whole channel data volume is ensured to be maintained at a relatively stable level.

3) The threshold M1 ensures the data volume in the data path and prevents delay in the data processing process from causing the outlet to break. Threshold M2 may prevent the ingress rate from being too high, resulting in a full cache for the subsequent processing module. Together, M1 and M2 ensure that data in subsequent data links remains within a stable range.

4) N1 and N2 ensure that IDLE is inserted when there is no data input, wherein low speed insertion of IDLE N2 ensures that IDLE in the entire data link is less, substantially maintained at M1, when there is no payoad transmission. Thus, when the data arrives, the data PAYLOAD can be sent as soon as possible, and the insertion of IDLE is fully reduced. N1 ensures that when IDLE is inserted at low speed, when C is lower than M1, data can be quickly supplemented to prevent current interruption.

5) Interface description and rate control flow, while adapting to different interface rates, ensure as few inserted IDLE as possible, fully increase data transmission efficiency, and ensure stability of exit rate.

Drawings

The invention will be described in further detail with reference to the drawings and the detailed description.

FIG. 1 is a control flow diagram of the present invention;

fig. 2 is a simplified data transmission schematic.

Detailed Description

The implementation of the invention is described in further detail below with reference to the accompanying drawings:

as shown in fig. 1, in an efficient Xepon old downlink transmission control method, a transmission enable judgment indicates whether a downlink transmission side starts transmission, and a separate independent switch is used to control overall on/off. First, it is determined whether or not the transmission enable is on, and the C value is kept at 0 in the off state. And then remains in this state until the transmit enable is turned on.

The transmission enable is turned on, and the following steps are performed:

1) olt the downstream data reading and front-stage module increases the speed control module, maintains the data variable V, judges the V value, inserts IDLE N1 at high speed when V is less than or equal to the threshold M1, and updates the variable V;

2) Continuously judging the V value, entering a waiting state when V is larger than a threshold M2, inputting no data in the waiting state, continuously outputting data, continuously reducing V, judging whether data PAYLOAD to be transmitted exist or not when V is smaller than the threshold M2, if yes, jumping to the step 3), and if no, jumping to the step 4);

3) Reading data PAYLOAD to be sent by a front-stage module, updating V, and when V is judged to be greater than a threshold M2, entering a waiting state and updating V; otherwise, continuing to read the PAYLOAD, updating V, and inserting the IPG after the end of the data PAYLOAD is read;

4) And the IDLE N2 is inserted at a low speed, so that continuous data input is ensured, and V is updated. The rate control is smoother while preventing flow break.

The IPG is inserted according to the data packet length by a minimum principle, so that the maximum efficiency is ensured, and the minimum IPG calculation method comprises the following steps: the packet length is divided by 4 to obtain a remainder t, and 8-t represents the inserted IPG length. The insertion of the smallest IPG (IPG is actually also IDLE, but may be an integer multiple of non-4 bytes), which may be inserted in a minimum of 5 bytes according to the protocol.

For the above flowchart, the high-speed insertion IDLE (4 byte integer multiple) data amount is set to N1, that is: IDLE N1. The low-speed insertion IDLE data amount is N2, namely: IDLE N2. The too small rate threshold is M1 and the too large rate threshold is M2. The four parameters are all configurable parameters.

The data variable V of the speed control module is the data quantity C in the link transmitted from the data input to the last outlet at a fixed system processing clock frequency, and the calculation method of the data quantity C is to subtract the data quantity transmitted by the outlet from the data to be transmitted. The data to be transmitted includes IDLE N1, IDLE N2, data payoad length read from the preceding module (note that each packet needs to be added with 8 bytes of preamble), and the granularity overhead of the inserted IPG, fec (granularity of 32 bytes of granularity is automatically added per 216 bytes of data transmitted). The amount of data that needs to be subtracted is then the amount of data that is sent by the egress. Olt is sent downstream at a steady rate, so the amount of data subtracted is a constant at a fixed clock frequency. The waiting time is the minimum time unit, one clk, so that the judgment is more timely, and the rate control is finer. Too small a rate of C is less than M1 and too large a rate of C is greater than M2.

In order to facilitate data processing and improve data processing efficiency, the following data interface descriptor idle_flag is set, and interfaces such as sop, eop and data of the data are not described.

And setting an IDLE_FLAG mark, wherein the IDLE_FLAG mark is used for indicating whether the current data is IDLE, and if the IDLE_FLAG mark is 1, the IDLE_FLAG mark is used for indicating that the current data is IDLE. A 0 indicates that the current data must contain data.

The payoad length PB is set in bytes. When the current data idle_flag is 0, PB is used to represent the data length contained in the current data, and the possible value is from 1 to the maximum value of the current data, and the current implementation is 1-16 bytes. When IDLE_FLAG is 1, no consideration is given.

The length of the data is set as DB, the unit byte and the IDLE_FLAG are 0, the data to be transmitted (including IDLE and data) contained in the current data is represented, the value is an integer multiple of 4, and the maximum value is the maximum value of the beat data, so that the subsequent module can conveniently perform the format conversion of the interface, and the value range of the current implementation scheme is 8, 12 and 16. And not 4, because there is typically only a preamble and a tail of the packet with a non-IDLE condition other than 16, and DB is at least 8, including the length of the IPG inserted. When the IDLE_FLAG is 1, the length of the IDLE is represented, and the unit is 4 bytes.

When the idle_flag is 1, pure IDLE data is represented, and the IDLE length is DB in 4 bytes. When the IDLE_FLAG is 0, the current data must contain PAYLOAD, if DB is equal to PB, the current data are all PAYLOAD, if DB is greater than PB, the value obtained by subtracting PB from DB is the number of inserted IDLE, and the unit is single byte. Whether IDLE, data packet or tail IPG, the method is described in a unified mode, which is convenient for calculating the V value and for subsequent data processing. Setting special interface descriptors ensures that the IPG between downstream data packets can reach a minimum.

Examples:

the example is applied to the Xepon olt downlink path and is used for controlling downlink data transmission.

The front module data clock 125M is 16 bytes wide and the interface rate is 16g. The Xepon downstream olt egress rate is fixed at 10g (here, the 64/66B encoded data overhead need not be considered, and the subsequent data processing modules automatically process it), at a clock frequency of 125M, olt outputs 10 bytes of data per clk. The amount of data output is fixed to 10 per clk, and the amount of data input is different according to different states of the system.

In the system, the threshold M1 takes a value of 300 units of bytes. The threshold M2 takes a value of 350, unit bytes. The high-speed insertion IDLE N1 takes a value of 5, 4 bytes in unit. The low-speed insertion IDLE N2 takes a value of 2, and is 4 bytes in unit. Other information such as sop, eop and data in the interface is not described in detail.

The IDLE N1 is inserted at high speed, the IDLE_FLAG is 1, the DB value is 4, and PB is not considered. Data C is calculated as c=c+n1 x 4-10.

When IDLE is inserted at low speed, the interface descriptor IDLE_FLAG is 1, DB takes a value of 2, PB is not considered. Data C is calculated as c=c+n2×4-10.

When data is transmitted, the interface descriptor IDLE_FLAG is 0, the DB value is 16, and the PB value is 16. The data C is calculated in a way of C=C+16-10; the descriptor is IDLE_FLAG 0, DB 8 and PB 8 when the preamble of the data packet. There are 3 cases when the end of the packet is not 16 bytes: tail bytes (expressed by pbw) are 1-11 bytes, the descriptor is IDLE_FLAG 0, the DB value is obtained by dividing pbw by 4, the quotient is rounded and added with 2, and finally multiplied by 4, the data C is calculated in a way of C=C+DB-10, and the PB value is obtained by pbw; in the 12-16 bytes of the tail byte, the descriptor is IDLE_FLGA 0, DB value is 16, PB value is pbw, the calculation mode of the data C is C=C+16-10, at the moment, the next descriptor IDLE_FLAG is 1, DB value is 1 (tail byte 12-15), or 2 (tail byte just 16), PB value is not considered, and the calculation method of the data C is C=C+DB 4-10.

When the amount of data transmitted reaches an integer multiple of 216 bytes or is larger than an integer multiple of 216 bytes for the first time (the amount of input data in the above case), the amount of data c=c+32-10 of the parity of the fec needs to be supplemented.

And data is not transmitted in the waiting period, and the data C is calculated in a way of C=C-10.

Based on the calculated data amount C and other conditions, the system is judged to enter different states (see fig. 1 for specific flow) to read the data payoad or send the IDLE, or wait, and the data amount in the system is kept between the thresholds M1 and M2.

The foregoing examples merely illustrate embodiments of the invention and are described in more detail and are not to be construed as limiting the scope of the invention. It should be noted that several variations and modifications can be made without departing from the inventive concept, which fall within the scope of the present invention.

Claims (2)

1. An efficient Xepon olt downlink transmission control method is characterized in that: the method comprises the following steps:

1) The speed control module is used for maintaining a data variable V, judging a V value, inserting an IDLE N1 at a high speed when the V value is less than or equal to a threshold value M1, and updating the variable V;

2) Continuously judging the V value, when V is larger than the threshold value M1 and larger than or equal to the threshold value M2, entering a waiting state, inputting no data under the waiting state, continuously outputting data, continuously reducing V, and judging whether the data PAYLOAD to be sent exists or not when the threshold value M1 is smaller than the threshold value M2, if yes, jumping to the step 3), and if no, jumping to the step 4);

3) Reading data PAYLOAD to be sent by a front-stage module, updating V, and when V is judged to be more than or equal to a threshold M2, entering a waiting state, and updating V; otherwise, continuing to read the PAYLOAD, updating V, and inserting the IPG after the end of the data PAYLOAD is read;

4) The IDLE N2 is inserted at a low speed, so that continuous data input is ensured, and V is updated;

the data variable V of the speed control module is the data volume C in the link from the data input to the last exit at a fixed system processing clock frequency, the data volume C is equal to the data volume to be transmitted minus the data volume transmitted by the exit, wherein the data to be transmitted includes: IDLE N1, IDLE N2, data payoad to be transmitted, preamble, IPG and the parity overhead of the fec;

setting a data interface mark IDLE_FLAG, DB and PB, wherein the IDLE_FLAG is used for indicating whether the current data is IDLE, and expressing complete data description information by combining a data byte variable DB and a PAYLOAD byte variable PB;

the IDLE_FLAG is 1, which means that the current data is a pure IDLE, the IDLE data length is DB, and the unit is 4 bytes;

an IDLE_FLAG of 0 indicates that the current data contains PAYLOAD, PAYLOAD with length PB, unit of single byte, data length DB, unit of single byte, and integer multiple of 4; if DB is equal to PB, the current data are all PAYLOAD, and if DB is greater than PB, the value obtained by subtracting PB from DB is the number of inserted IDLE.

2. The efficient Xepon olt downlink transmission control method according to claim 1, wherein: the IPG is inserted according to the data packet length by a minimum principle, and the minimum IPG calculation method comprises the following steps: the packet length is divided by 4 to obtain a remainder t, and 8-t represents the inserted IPG length.