CN102739508B - A kind of method and system of express network data transmission - Google Patents

Abstract

The invention discloses a method for high-speed network data transmission. The method includes: when the server determines that the congestion window of the current flow exceeds a threshold value, obtains an additive increase factor according to the average value of RTT obtained by a router, and increases the factor according to the obtained additive value. Factor to adjust the congestion window. The present invention also discloses a system for high-speed network data transmission. By adopting the method and system described in the present invention, the bandwidth resources of streams with relatively small delays are reduced, and the bandwidth resources of streams with relatively large delays are increased, thereby increasing the The fairness of bandwidth occupancy between concurrently delayed flows improves the service quality of high-speed bandwidth networks.

Description

Method and system for high-speed network data transmission

technical field

The invention relates to the field of network data transmission, in particular to a method and system for high-speed network data transmission.

Background technique

With the continuous development of network technology, more and more high-speed networks with bandwidth greater than 1Gbps appear. Such networks usually have the characteristics of high bandwidth delay product (BDP, Bandwidth Delay Product), which will bring a very large congestion window. , the traditional transmission control protocol (TCP) is no longer suitable for the requirements of network development. Wherein, the congestion window refers to the maximum number of data packets sent within one round-trip time delay (RTT).

Currently, the standard TCP protocol uses the Additive Increase Multiplicative Descent (AIMD) algorithm to adjust the size of the congestion window w:

In the congestion avoidance phase, there is no congestion yet, and the congestion window size can be adjusted by formula (1),

In the congestion phase, due to congestion, the number of data packets sent needs to be reduced, and the congestion window size is adjusted by formula (3), w←w-bw(2).

In the slow start phase, it is necessary to quickly increase the bandwidth rate, and the congestion window size can be adjusted through the slow start parameter and formula (2), w←w+c(3);

Wherein, according to the provisions in the TCP protocol, the additive increase (AI) factor a=1, the multiplicative decrease (MD) factor b=0.5, the slow start parameter c=1, and the unit of a, b, and c is the maximum segment length (MSS).

However, there will be a problem in adjusting the congestion window process according to the above method, assuming that the congestion window is reduced to w=1 due to packet loss, the sending end enters the congestion avoidance stage, and the server in the network increases the congestion window linearly by formula (1); If the congestion window is to reach X, each time the congestion window increases by 1, it takes X-1 round trip times. In this case, if you want to achieve a speed of 10Gbps, assuming that the round-trip time is 100ms, and the window value corresponding to 10Gbps is 83333, then 83332 round-trip times are required, and it takes 8333 seconds to reach the above-mentioned speed, which is unacceptable in practical applications.

Aiming at the problems of slow response and slow window expansion of the AIMD algorithm in the TCP protocol in a high-bandwidth-delay product network environment, Floyd proposed an AIMD window adjustment algorithm based on packet loss, namely the High Speed TCP (HSTCP) algorithm. The main idea of the HSTCP algorithm is: set a congestion window threshold value w _low , when the congestion window value w exceeds w _low , according to formula (1) and formula (3), set the additive increase factor and the multiplicative decrease factor is a function of w, namely a(w) and b(w). In this way, the additive increase factor a(w) increases with the increase of w, the multiplicative decrease factor b(w) decreases with the increase of w, and a(w) and b(w) change linearly . In this way, the slow linear growth of the congestion window in a high-speed network environment is avoided; and, when congestion occurs, a large reduction in the slow start threshold is avoided.

However, there is a problem with the HSTCP algorithm: the flow of different RTTs has the problem of unfair bandwidth utilization during the transmission process, and the congestion window of the flow with small delay increases rapidly, which will seize bandwidth resources.

According to the analysis, the throughput relationship when HSTCP flows with different RTTs compete with each other is:

$\frac{\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; W</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; RTT</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; W</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; RTT</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; =</span>{<span\; class="notranslate">\; [</span>\frac{{\mathrm{<span\; class="notranslate">\; RTT</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; RTT</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; ]</span>}^{\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; d</span>}}}$

Wherein, according to the HSTCP algorithm, d is 0.82, assuming that there are 2 streams, and RTT1:RTT2=1:2, then the throughput ratio of the two streams is T1:T2=1:47.

It can be seen that in the HSTCP algorithm, there is obvious unfairness in the competition between data streams with different delays, which has a great impact on the service quality of users with relatively large delays, and cannot enjoy the advantages of high-speed bandwidth.

Contents of the invention

In view of this, the main purpose of the present invention is to provide a method and system for high-speed network data transmission, which can reduce the bandwidth resources of streams with relatively small delays and increase the bandwidth resources of streams with large delays, thereby increasing the The fairness of bandwidth occupancy between delayed flows improves the service quality of high-speed bandwidth networks.

In order to achieve the above object, technical solution of the present invention is achieved in that way:

The invention provides a method for high-speed network data transmission, the method comprising:

When the server determines that the congestion window of the current flow exceeds the threshold value, it obtains an additive increase factor according to the average round-trip delay RTT obtained by the router, and adjusts the congestion window according to the obtained additive increase factor.

In the above solution, before obtaining the additive increase factor according to the average RTT obtained by the router, the method further includes: the router records the RTT of the received flow, determines that there is an RTT update of the flow, and obtains the average RTT.

In the above scheme, the determination of the RTT update of the flow and obtaining the RTT average value include: the router obtains the RTT of the flow received by itself in real time, and when the RTT of the flow changes, it is determined that the RTT update of the flow is updated, and the router delay statistics table is updated. The RTT of the flow, and according to the RTT average calculation formula and the RTT in the router delay statistics table, obtain the RTT average value.

In the above solution, before the server determines that the congestion window of the current flow exceeds the threshold value, the method further includes: the server sends the flow to the router, records and updates the RTT of the flow sent by itself in the server delay statistics unit.

In the above scheme, the acquisition of the additive increase factor based on the RTT average value includes: obtaining the fairness factor corresponding to the flow according to the RTT, the RTT average value, and the fairness factor calculation formula of the flow in the server delay statistics unit, and combining the fairness factor with the high-speed Multiply the additive increase factors in the transmission control protocol HSTCP to obtain a new additive increase factor.

The present invention also provides a high-speed network data transmission system, which includes: a window adjustment module and a parameter acquisition module;

The parameter acquisition module is used to obtain the RTT average value and send it to the window adjustment module;

The window adjustment module is configured to obtain an additive increase factor according to the RTT average value and adjust the congestion window according to the acquired additive increase factor when it is determined that the congestion window of the current flow exceeds a threshold value.

In the above scheme, the window adjustment module includes: a server delay update unit, an additive increase factor acquisition unit; a server delay update unit, which records the RTT of the flow sent by itself, stores it in the server delay statistics unit, and updates the server delay The RTT in the statistical unit; the additive increase factor acquisition unit is used to obtain the RTT, RTT average value and fair factor calculation formula of the flow in the server delay statistical unit when determining that the congestion window of the current flow exceeds the threshold value. The fairness factor corresponding to the flow. Multiply the fairness factor with the additive increase factor in the HSTCP protocol to obtain a new additive increase factor.

In the above scheme, the parameter acquisition module includes: router delay update unit, average value acquisition unit; router delay update unit, used to record the RTT of the received flow, save it in the router delay statistics table, and determine the RTT of the flow Update, notify the average value acquisition unit.

In the above scheme, the router delay update unit is specifically used to obtain the RTT of the flow received by itself in real time, and when the RTT of the flow changes, it is determined that the RTT of the flow is updated, and the RTT of the flow described in the router delay statistics table is updated. ; The average value obtaining unit is used to obtain the RTT average value according to the RTT and the RTT average value calculation formula in the router delay statistics table.

It can be seen that, using the method and system of the present invention, the additive increase factor is adjusted through the average value of time delay, so that the window growth of the flow with relatively small time delay is small, and the window of the flow with relatively large time delay The window increases greatly, reducing the bandwidth resources of flows with relatively small delays and increasing the bandwidth resources of flows with large delays, thereby increasing the fairness of bandwidth occupancy among flows with different delays, and improving the efficiency of high-speed bandwidth networks. service quality.

Description of drawings

Fig. 1 is a schematic diagram of an embodiment of a method for realizing high-speed network data transmission in the present invention;

Figure 2 is a schematic diagram of a data transmission application scenario;

Fig. 3 is the schematic diagram of the embodiment of the method that realizes that router obtains RTT average value in the present invention;

FIG. 4 is a schematic diagram of an embodiment of a system for realizing high-speed network data transmission according to the present invention.

detailed description

The basic idea of the present invention is: when the server determines that the congestion window of the current flow exceeds the threshold value, it obtains the additive increase factor according to the RTT average value obtained by the router, and adjusts the congestion window according to the acquired additive increase factor.

The present invention will be described in detail below through specific embodiments and accompanying drawings. The present invention provides a method for high-speed network data transmission, as shown in Figure 1, and the specific steps are as follows:

Step 101, the server judges whether the congestion window of the current flow exceeds the threshold w _low , if so, executes step 102; otherwise, executes step 104;

Here, the threshold w _low is a value specified by the HSTCP protocol;

In the embodiment of the present invention, a schematic diagram of network data transmission application scenarios is shown in Figure 2. The server sends one or more streams to the router, and the router sends them to the user. Multiple servers form a server cluster, and the router receives multiple streams sent by the server cluster at the same time. flow.

Usually, the server sends streams to the router, records and updates the RTT of the streams sent by itself in the server delay statistics unit, and judges whether the congestion window of the current stream exceeds the threshold value. The server delay statistics unit saves the streams sent by the server and the corresponding A kind of software storage form of the corresponding relationship of the RTT; The RTT of the self-sending flow in the recording server delay statistics unit includes: the server reads the RTT of the flow sent by itself in real time according to the TCP protocol, and saves it in the server delay statistics unit , if a new stream is sent, then use the new server delay statistics unit to save the new stream and the corresponding RTT; the RTT of the self-sent stream in the update server delay statistics unit includes: the server reads the stream sent by itself If the RTT of the flow changes, the RTT value corresponding to the flow in the server delay statistics unit corresponding to the flow is updated to the changed value.

Specifically, the judging whether the congestion window of the current flow exceeds the threshold value w _low includes: the server reads the number of windows of the flow sent by itself, that is: the size of the congestion window, and compares it with the threshold value w _low specified by the HSTCP protocol , if the congestion window size of the flow sent by itself exceeds the threshold value, it means that the current link bandwidth is high, and the congestion window needs to be adjusted, and step 102 is performed; otherwise, the transmission is still carried out according to the standard TCP protocol.

Step 102, according to the RTT average value obtained by the router, obtain the additive increase factor;

The server receives the RTT average value β of all flows sent by the router, and obtains the fair factor η according to β and the fair factor calculation formula, i.e. formula (4), and the fair factor calculation formula is:

$\mathrm{<span\; class="notranslate">\; \&eta;</span>}<span\; class="notranslate">\; =</span>{<span\; class="notranslate">\; [</span>\frac{{\mathrm{<span\; class="notranslate">\; RTT</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}<span\; class="notranslate">\; ]</span>}^{\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; d</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

Among them, RTT _i is the RTT corresponding to the flow in the server delay statistics unit;

Then, the fairness factor is multiplied with the additive increase factor in the HSTCP protocol to obtain a new additive increase factor, namely: a(w)=a(w)*η

Wherein, the process of the router obtaining the RTT average value is shown in Figure 3, including the following steps:

Step 102a, the router records the RTT of the received flow;

Specifically, the record includes: the router receives the flow sent by the server cluster, obtains the RTT of the flow and saves it in the local router delay statistics table, if the received flow is newly added, obtains the RTT of the newly added flow, and Add the RTT of the flow to the router delay statistics table; the RTT of the acquisition flow can adopt multiple methods: the server can carry the RTT of the flow in the flow sent, and the router directly reads the RTT of the flow in the flow The RTT of the flow; it may also be the RTT of the router reading the flow according to the provisions of the TCP protocol, which will not be listed here. Wherein, the router delay statistics table is a correspondence table of flows received by the router and corresponding RTTs.

Step 102b, the router judges whether there is an RTT update of the flow;

Specifically, the judgment includes: the router obtains the RTT of the flow received by itself in real time, if there is a change in the RTT of the flow, it indicates that the RTT has been updated, and the RTT of the flow in the router delay statistics table is updated; the update includes: In the router delay statistics table, the RTT corresponding to the flow with RTT change is changed to the updated RTT, and then step 102c is executed; otherwise, step 102a is executed;

Step 102c, calculating the average value of RTT.

Specifically, read the RTTs of all flows in the router delay statistics table, obtain the average RTT value according to the formula (5) for calculating the average RTT value, and send the obtained average RTT value to the server.

$\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; =</span>\frac{\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; RTT</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

Step 103, adjust the congestion window according to the obtained additive increase factor, and end the current processing flow;

Specifically, the server sets the additive increase factor as the additive increase factor obtained according to the average value of the RTT, that is, the new additive increase factor, and can adjust the congestion window by itself. In this way, for a flow with a small delay, its additive increase factor is also small, and compared with a flow with a large delay, the increase of its congestion window is small, thereby improving the bandwidth utilization rate of a flow with a long delay.

Step 104: still transmit the flow to the router according to the standard TCP protocol.

Based on the above method, the present invention also provides a system for high-speed network data transmission, the system includes: a window adjustment module 401, a parameter acquisition module 402; wherein, the window adjustment module 401 is located in the server, and the parameter acquisition module 402 is located in the router or Router exit;

The window adjustment module 401 is used to determine that the congestion window of the current flow exceeds the threshold value, obtains the additive increase factor according to the RTT average value obtained by the parameter acquisition module, and adjusts the congestion window according to the acquired additive increase factor;

The parameter acquisition module 402 is configured to acquire the average value of the RTT and send it to the window adjustment module 401 .

The window adjustment module 401 includes: a server delay update unit 4011, an additive increase factor acquisition unit 4012;

The server delay update unit 4011 is used to record and update the RTT of the stream sent by itself in the server delay statistics unit; the record includes: the server reads the RTT of the stream sent by itself in real time according to the TCP protocol, and saves it in the server delay statistics In the unit, if there is a new flow to send out, then use the new server delay statistics unit to save the new flow and the corresponding RTT; the update includes: the server reads the RTT of the flow sent by itself, if there is a change in the RTT of the flow, Then update the RTT value corresponding to the flow in the server delay statistics unit corresponding to the flow to the changed value;

The additive increase factor obtaining unit 4012 is used to obtain the flow rate according to the RTT average value, the flow in the server delay statistics unit and the corresponding RTT, and the fairness factor calculation formula when it is determined that the congestion window of the current flow exceeds the threshold value. Fairness factor. Multiply the fairness factor with the additive increase factor in the HSTCP protocol to obtain a new additive increase factor.

The parameter acquisition module 402 includes: a router delay update unit 4021, an average value acquisition unit 4022;

The router delay update unit 4021 is configured to record the round-trip delay RTT of the received flow, determine that there is an RTT update of the flow, and notify the average value acquisition unit 4022 .

The average value acquisition unit 4022 is configured to obtain the average value of RTT according to the RTT recorded in the router delay statistics table and the average calculation formula.

The router time delay updating unit 4021 is specifically used to obtain the RTT of the flow received by the router in real time. When the RTT of the flow changes, it is determined that the RTT of the flow is updated, and updates the RTT of the flow in the router time delay statistics table; Including: changing the RTT corresponding to the flow in the router delay statistics table to the updated RTT.

The above description is only a preferred embodiment of the present invention, and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included in the within the protection scope of the present invention.

Claims (6)

1. the method for an express network data transmission, it is characterised in that the method includes:

Server sends stream to router, records and updates self transmission stream in server delay statistics unit Round-trip delay RTT；

Server determines when the congestion window of current stream exceedes threshold value, according in server delay statistics unit The RTT meansigma methods of the RTT of stream, router acquisition and fairness index computing formulaObtain institute State the fairness index η that stream is corresponding, by fairness index with high speed processing system HSTCP agreement adds formula Increasing fac-tor, obtaining the new formula that adds increases the factor, and adjusts congested according to the formula increase factor that adds obtained Window, wherein, described d=0.82.

Method the most according to claim 1, it is characterised in that the described RTT obtained according to router Meansigma methods obtains before adding the formula increase factor, and the method farther includes:

Router records receives the RTT of stream, determines that the RTT having stream updates, and obtains RTT meansigma methods.

Method the most according to claim 2, it is characterised in that described determine that the RTT having stream updates, Obtain RTT meansigma methods to include:

Router obtains self in real time and receives the RTT of stream, when having the RTT change of stream, it is determined that have stream RTT updates, more the RTT of stream described in new router delay statistics table, and public according to RTT mean value calculation RTT in formula and router delay statistics table, obtains RTT meansigma methods.

4. the system of an express network data transmission, it is characterised in that this system includes: window adjusts mould Block, parameter acquisition module；

Parameter acquisition module, is used for obtaining RTT meansigma methods, is sent to window adjustment module；

Server time delay updating block, sends the RTT of stream for recording self, is saved in server time delay system In meter unit, update the RTT in server delay statistics unit；

Add formula and increase factor acquirement unit, during for exceeding threshold value at the congestion window determining current stream, root According to RTT, RTT meansigma methods flowed in server delay statistics unit and fairness index computing formulaObtain the fairness index η that described stream is corresponding, by fairness index and adding in HSTCP agreement Formula increases fac-tor, and obtaining the new formula that adds increases the factor, and gathers around according to the formula increase factor adjustment that adds obtained Plug window, wherein, described d=0.82.

System the most according to claim 4, it is characterised in that described parameter acquisition module includes: road By device time delay updating block, meansigma methods acquiring unit；

Router time delay updating block, for recording the RTT receiving stream, is saved in router delay statistics table In, determine that the RTT having stream updates, notify meansigma methods acquiring unit.

System the most according to claim 5, it is characterised in that

Described router time delay updating block, receives the RTT of stream specifically for obtaining self in real time, has stream During RTT change, it is determined that have the RTT of stream to update, the more RTT of stream described in new router delay statistics table；

Meansigma methods acquiring unit, based on according to RTT and the RTT meansigma methods in router delay statistics table Calculate formula, obtain RTT meansigma methods.