CN102325082A - Nomadic application-oriented network congestion control method - Google Patents

Abstract

The invention relates to a nomadic-application-oriented network congestion control method. The network congestion adaptive method provides a congestion adaptive control algorithm based on up semi-normal distribution-DARED (distributed adaptive random early detection). According to the DARED algorithm, the corresponding congestion control is performed by improving an original data packet discarding probability function curve, namely adjusting an existing linear discarding straight line of an RED (random early detection) algorithm to a smooth curve, and dividing into different network states according to the queue length. The DARED is characterized in that a real-time dynamic parameter Pmax is introduced on the basis of the traditional RED algorithm, the stability of a queue is kept and the controllability of network congestion is increased. Correspondingly, in the aspect of a nomadic application system, when applied to the aspect of a multimedia seamless migration system, the congestion control algorithm realizes the seamless migration strategy under different architectures, namely the migration strategy under a B/S (browser/server) architecture, the migration strategy under a P2P (peer-to-peer) architecture and the migration strategy under a C/S (client/server) architecture. By adopting the nomadic application-oriented network congestion control method, the continuity, the rapidity, the smoothness and the correctness of media migration can be effectively ensured.

Description

A kind of method for controlling network congestion towards nomadic application

[technical field]:

The invention belongs to the technical field that computer network, communication and Digital Media etc. combine.

[background technology]:

Fusion along with mobile communication and mobile computing technology; The progressively maturation of mobile technology; Moving that the application of mobile technology and development bring is mutual, for online connection, communication and information exchange whenever and wherever possible provides possibility, for mobile working new opportunities and challenges is provided simultaneously.Along with the expansion of network application scale and increasing of bearer service, the increase of network load, the local appearance of network is congested, and throughput descends, and real-time Transmission audio frequency and video on the network under the nomadic environment must take to prevent the measure of network congestion.How effectively to avoid traffic congestion, improve network performance and operational efficiency, guarantee that simultaneously the different demands of user on multimedia information become the focus that many researchs are paid close attention to.

The subject matter of congestion control mechanism in communication environment is that the network of various mixing exists simultaneously; Coexistence comprising broadband networks, arrowband net, various local area network (LAN), wireless network, wired network; How to realize transmission data smooth between these networks, will become the important bottleneck of communications applications development.

The reason that network congestion control produces is: when the available resources that provide when network can not satisfy user's demand; The transmission performance of network will descend, will produce so congested since nomadic application under network be the network of isomery; The network environment more complicated; The inconsistency of the interface of various terminal equipments, diverse network and deposit, will inevitably cause the congested of network.The grouping that the i.e. appearance of subnet in a network is transmitted is too much, and the disposal ability of network is limited, that is to say that the load of network has surpassed the ability to bear of network, and promptly network has taken place congested.Congested the following aspects that mainly shows of network: propagation delay time increase end to end, the decreased performance of system, grouping of network are lost etc.Wherein the immediate cause of congested generation comprise following some:

(1) memory space inadequate: if several TCP stream sends data to a router side simultaneously, the router side storage capacity is limited, and the reception data capability of receiving terminal is limited simultaneously; At this moment, need handle these packets through setting up a formation, but owing to receive the restriction of factors such as network equipment physics; The limited length of formation; Some packet must abandon, to this situation produce congested, increase memory space and just can address this problem.

(2) bandwidth is too narrow: when several TCP flow simultaneously when a router sends data; Especially high-speed link is when low speed chain circuit transmission data; Because the ability that link is transmitted is different, low speed chain circuit is easy to form bottleneck, is easy to produce congested like this; The bottleneck that this situation forms can be resolved through increasing bottleneck bandwidth.

(3) processor processes is limited in one's ability: if the processing speed of CPU is lower than the transmission speed of high-speed link, also be easy to generate bottleneck, form congested.

Network has the existence of a large amount of destabilizing factors in data transmission procedure, simultaneously because the data of Internet have suddenly, be prone to a large amount of pending packets; And Internet of Things is as a kind of emerging, and complicated latticed form is sudden inevitable especially; Therefore; Want to solve sudden under the nomadic environment, must find a suitable algorithm, this algorithm must be able to handle a large amount of burst data bag of automatic network.

[summary of the invention]:

The smooth problem of the communication that the present invention seeks to solve the network congestion under the nomadic application model and under multimedia seamless migration system, use; To guarantee the smooth clog-free operation of network; Promote the development and the application of nomadic communication; Thereby proposed based on congested adaptive control DARED (the Distributed Adaptive RED) algorithm that rises half normal distribution, and analyzed the system feasibility of this algorithm under nomadic applied environment theoretically.

The concrete steps of the method for controlling network congestion towards nomadic application provided by the invention:

1st, when the packet arrives router, adopt the RED algorithm to calculate average queue length Q according to low pass filter _Av, i.e. the mean value of the queue length on the unit interval.Can obtain by following formula:

Q _av＝(1-w _q)×Q _av+w _q×q

Wherein, w _qBe expressed as the time coefficient of being confirmed by low pass filter, q is expressed as the length of active formation when measuring.

2nd, the average queue length Q that the 1st step was calculated _AvMax threshold threshold values Q with the drop probability curve _MaxWith minimum threshold threshold values Q _MinCompare,, current Congestion Level SPCC be divided into three kinds of states, be respectively according to comparative result:

Between, promptly average queue length is in Q _MinAnd Q _MaxBetween, i.e. formation is in stable state, and states is set between;

Above, average queue length is greater than Q _Max, the state of state is set to the above state;

Bellow, average queue length is less than Q _Min, the state of states is set to bellow;

3rd, the Congestion Level SPCC of confirming according to the 2nd step carries out dynamic self adaptation adjustment, takes corresponding data packet discarding probability, and hold queue length is avoided unnecessary shake in stable scope, and concrete operations are:

When continuous 2 time intervals are in the below state, think that then the utilance of link is low, through adjustment p _MaxValue improves the utilance of link;

When continuous 2 time intervals were in the above state, it was congested to think that then link takes place, and dynamically adjusts p _MaxValue, increase to the source end and send congested notice so that make the source end reduce transmission rate, thereby alleviate congested.

Described method for controlling network congestion is to realize that through the seamless migration fast of the medium under the different frameworks concrete grammar is following:

Migration strategy under the B/S framework: use the technology of Ajax technology as the front end data migration.Ajax is the fusion of several kinds of technology, the fusion between promptly asynchronous JavaScript and XML.Propelling movement module to service end realizes simultaneously, data propelling movement module that we have adopted the Comet art designs.

Migration strategy under the P2P framework: used the such mature technique of JMF to realize emphatically; The SessionManager interface that utilizes this technology to provide has simultaneously been realized the congested control in the Streaming Media transition process well; Studied method again on this basis based on the excavation and the migration of key frame; Promptly designed the key code of receiver module, guaranteed QoS with action migration event module;

Seamless migration strategy under the C/S framework: used the ripe like this control of ActiveMovie to construct player emphatically, and in the audio frequency and video file transfer, used location-based cutting shift function and congested control, guaranteed the efficient of migration.

Advantage of the present invention and good effect:

This paper has proposed a kind of based on the network congestion adaptive control algorithm that rises half normal distribution, carries out control corresponding through improving original data packet discarding probability function and maximum drop probability parameter value.Utilize the NS2 simulation software to carry out emulation; Experimental result shows; Can adapt to the variation of the complicated network congestion environment of Internet of Things based on the network congestion adaptive control algorithm that rises half normal distribution; The stability that has kept queue length is superior to traditional RED algorithm aspect in the variation of data packet discarding probability.

This paper has inquired into a kind of mechanism that can accurately distinguish the data-bag lost reason efficiently, and takes different measures according to different congestion states, utilizes this mechanism can effectively suppress network congestion, improves network performance.

This paper proposes and has designed the seamless migration strategy based on three kinds of different frameworks of this congestion control mechanism simultaneously; Be seamless migration strategy, the seamless migration strategy under the P2P framework and the seamless migration strategy under the C/S framework under the B/S framework; Guarantee efficiency, the qualitative and validity of seamless migration, thereby under nomadic system, have feasibility.

[description of drawings]:

Fig. 1 is the network analog topological diagram;

Fig. 2 is RED average queue length and packet loss graph of a relation and based on the probability dropping that rises half normal distribution;

Fig. 3 is three kinds of state transition graphs;

Fig. 4 is a program flow diagram;

Fig. 5 is that queue length changes when being sent as 10k/s under RED and the DRED algorithm;

Fig. 6 be RED and DRED algorithm transmission rate when being 10k/s packet loss change;

Fig. 7 is the variation of RED and DRED algorithm transmission rate queue length when being 10m/s;

Fig. 8 be RED and DRED algorithm transmission rate when being 10m/s packet loss change;

Fig. 9 is that queue length changed when speed changed suddenly under RED and the DRED algorithm;

Figure 10 is that packet loss changed when transmission rate changed suddenly under RED and the DRED algorithm;

Figure 11 is that the TCP throughput and the actual bandwidth of DRED and other several kinds of algorithms compares;

Figure 12 is the Voice & Video seamless migration design sketch under the B/S framework;

Figure 13 is the video seamless migration design sketch under the P2P framework;

Figure 14 is the video seamless migration design sketch under the C/S framework.

[embodiment]:

The concrete technical scheme of the method for controlling network congestion towards nomadic application provided by the invention is following

The 1st DRED algorithm computation is average queue length Q with existing parameter exactly _Av, max threshold threshold values Q _MaxWith minimum threshold threshold values Q _MinThe new probability formula that requires the substitution data packet discarding (1) according to fuzzy theory normal distribution membership function; Abandon curve thereby change linearity, can carry out parameter configuration according to the congestion situation of the network environment under the nomadic pattern simultaneously, reduced the sensitiveness that algorithm is provided with for parameter; Be max threshold threshold values and minimum threshold threshold values, queue length is controlled between max threshold threshold value and the minimum threshold threshold value.As shown in Figure 2, the straight line of linear change is become the luminance curve of the slyness that rises half cosine normal distribution.

The new probability formula of data packet discarding is following:

$p=\left\{\begin{array}{cc}0& 0\&le;Q_{\mathrm{av}}<Q_{\min }\\ P_{\max }\&times;\frac{Q_{\mathrm{av}}-Q_{\min }}{Q_{\max }-Q_{\min }}& Q_{\min }\&le;Q_{\mathrm{av}}<Q_{\max }\\ 1& Q_{\max }\&le;Q_{\mathrm{av}}<B\end{array}\right.---\left(1\right)$

First

Rise half normal distribution and obtain by the normal distribution conversion, the same with normal distribution, be to have two parameter μ and σ ²The continuous type random distribution, wherein μ is the average of normally distributed random variable, σ ²Be variance of a random variable, it is following to rise half normal distribution formula:

Setting μ is average queue queue Q _Avβ is minimum threshold threshold values Q _MinWith Q _AvAnd Q _MinWe obtain the data packet discarding new probability formula substitution formula (2):

$P\left(Q_{\mathrm{av}}\right)=\left\{\begin{array}{cc}0& Q_{\mathrm{av}}\&le;Q_{\min }\\ 1-e^{-\mathrm{\&alpha;}{(Q_{\mathrm{av}}-Q_{\min })}^2}& Q_{\mathrm{av}}>Q_{\min }\end{array}\right.---\left(3\right)$

For convenience of calculation, we set k is max threshold threshold values Q _MaxWith minimum threshold threshold values Q _MinPoor, following formula:

k＝Q _max-Q _min (4)

We know according to the characteristic of RED algorithm, when queue length is max threshold threshold values Q _MaxThe time, the drop probability of packet is p _Max, can obtain α and be:

$\mathrm{\&alpha;}=-\frac{\ln (1-P_{\max })}{k^2}---\left(5\right)$

We can find out from formula, and the α value is by p _MaxAnd decide.

Bring the value of parameter alpha into just can obtain grouping and abandon the distribution probability function based on rising half normal distribution:

$P\left(Q_{\mathrm{av}}\right)=\left\{\begin{array}{cc}0& Q_{\mathrm{av}}\&le;Q_{\min }\\ 1-{(1-P_{\max })}^{-{\left(\frac{Q_{\mathrm{av}}-Q_{\min }}{k}\right)}^2}& Q_{\mathrm{av}}>Q_{\min }\end{array}\right.---\left(6\right)$

Can find out from formula, based on the data packet discarding probability function that rises half normal distribution with max threshold threshold values Q _MaxWith minimum threshold threshold values Q _MinRelevant, we find out simultaneously, along with the variation of waiting for the forwarding queue average length, improve algorithm and more can adapt to the complicated hybrid network environment of Internet of Things.

Second

When the packet arrives router, setting maximum queue length is max threshold threshold values Q _MaxWith minimum queue length be minimum threshold threshold values Q _Min, by the mean value Q of formula queue length _Av=(1-w _q) * Q _Av+ w _q* q obtains average queue length Q _AvIf queue length is between max threshold threshold value and minimum threshold threshold value, then network state is in stable state, does not have occurring network congested.

As average queue length Q _AvBe not in Q _MinAnd Q _MaxBetween the time, we divide two kinds of situation to consider:

1. average queue length is less than the minimum threshold threshold value, and drop probability is less than 0.5:

If queue length is less than minimum queue length then increase transmission rate; If queue length is greater than minimum queue length then reduce to abandon speed p and keep the stable transmission rate of source end.

2. average queue length is greater than the minimum threshold threshold value, and drop probability is greater than 0.5:

If surpassing maximum queue length then increase, queue length abandons speed p; If queue length is less than maximum queue length then keep stable queue length.

As average queue length Q _AvAt Q _MinAnd Q _MaxBetween the time, we divide two kinds of situation to consider:

1. as average queue length Q _AvMore near Q _MinWhen neighbouring, promptly

The running status of network is good, and should reduce the value of drop probability p this moment, increases or keep the transmission rate of source end, increases bandwidth utilization;

2. as average queue length Q _AvMore near Q _MaxWhen neighbouring, promptly

The load of the network operation begins to increase, and should increase data packet discarding Probability p value this moment, can effectively prevent the generation of network congestion like this.

So we are divided into three kinds of states with congested control: (queue length is in Q to be respectively Between _MinAnd Q _MaxBetween), (queue length is greater than Q for Above _Max), (queue length is less than Q for Bellow _Min).As shown in Figure 3.

One, Between: queue length is in Q _MinAnd Q _MaxBetween the time, the transmit status of network is good, keeps transmission rate;

Two, Above: queue length is greater than Q _Max, the value of increase data packet discarding probability, the notification source end reduces transmission rate;

Three, Bellow: queue length is less than Q _Min, the network operation is in good condition, and bandwidth is idle in a large number, and the notification source end increases transmission rate;

The 3rd

According to above analysis, we have designed based on rising the adaptive DARED algorithm of half normal distribution, and Fig. 4 is a flow chart, and the specific algorithm analysis is following:

Meaning of parameters:

Qav: queue length;

P _Max: maximum drop probabilities value;

BufferSize: current buffer size.

2nd, through improved RED algorithm application at multimedia seamless migration system aspects:

Along with the development of Internet technology explosion type, the user needs network that a greater variety of services are provided, and guarantees the excellent communications performance.Therefore, under situation such as resource migration, network congestion or the system failure, how high quality services being provided continuously and stably, is the hot issue of current internet area research.The seamless migration technology proposes in order to overcome the above problems, for the stability and the reliability of internet communication provides good basis.The present invention proposes the seamless migration mechanism based on improved RED algorithm, and server can have different application protocols and host-host protocol before and after the migration, and communication can continue to carry out, and is unaffected.It is in order to guarantee the continuity of resource acquisition in communication process, to have solved because the communication disruption problem of bringing in the resource migration process that the control of network congestion is applied in multimedia seamless migration system.User's impression guarantees the stability and the reliability of service less than the migration that connects in the communication process.Through the test of experiment porch, show that this scheme satisfies the functional requirement of network services migrating basically.

The realization of the multimedia seamless migration strategy under the B/S framework

At the Browser end, the function of audio frequency and video control module mainly concentrates on the control to the audio player that embeds in the webpage.Control operation mainly comprises play operation, pausing operation, obtains break-point operation, migration operation.The playing module that we use is based on the MediaPlayer webpage player that embeds in the webpage.The self-defining control function relevant with this playing module has: play (), pause () and stop () function; The relevant parameter of obtaining the audio frequency and video play position, we are defined as currentPosition with it.Below just the code of the control function of correspondence is showed as follows:

Play () is used to realize the broadcast of the designated tone video media of assigned address.Modern in fact sign indicating number as follows.

For the function of the propelling movement module of accomplishing service end, we must be at Browser end definition function of the same name.The function of the same name here be update (Position, Name).The code of its realization is following.

Update () function is used to realize cooperating service end to push the realization of module.The value of giving relevant parameter is media name and breakpoint size, makes broadcast.

In order to realize function corresponding through button click, need to use < inpu/>label to create corresponding required button element, and then, further be integrated into the Browser end.Arrive this, the important modularity function of Browser end is created and finishes.What need coach is to use < div>label to realize the demonstration of position position sign.< iframe>label is to be used to show other pages.

In order to realize playing all audio frequency and video, we have specially studied the RealPlayer playing module again.RealPlayer playing module code omits.Similar with MediaPlayer webpage player.Need this player code is embedded in<body></body>In the label.Have a look its main control function code.Main function code is following.

Play () function is used to be implemented in appointed positions and plays the audio-video frequency media that is provided with.This power function code is following.

GetPosition () function is used to obtain breakpoint location, display media breakpoint location on the page.This power function code is following.

Equally, in order to send the POST request and to realize pushing function performance, definition respectively: CometTransfer () function and Update (Position, Name) function.Its function code and MediaPlayer playing module are similar, no longer provide at this.

The realization of file without seam transferring module mainly relies on<iframe></iframe>With<form></form>Two labels.Simultaneously, the building of environment that also needs jspsmartupload.jar bag and Apache Server.At first; Used < iframe>label to embed the webpage that needs; The back is carried out upload file, is sent the POST request through CometTransfer () functional based method through this interface; Finally, in the browser of Client end, created hyperlink, so that the Client end is downloaded through < Ahref>label.

Its main function code or algorithm are following.

Update (Position, Name) realize as follows by algorithm.

Create corresponding hyperlink.

CometTransfer () function is used for transfer parameter and parameter value.Modern in fact sign indicating number as follows.

Certainly, for the seamless migration of file, also can be incorporated into simultaneously uploading with download function.So only need, the function of download just can be realized uploading in the address of the webpage that migration is uploaded, and then realizes the function of seamless migration.

Under the B/S framework, Comet ^[34]Pushing module is the most difficult the realization.The implication of CometContext is a context, when environmental context changes, can acquire change and the communal space that can migration data; The implication of CometEvent is an incident, can comprise the object of CometContext, is used for response, and steering procedure is handled the generation of some incidents; The implication of CometHandler is a handle, can realize the interface of mutual CometContext.The step that realizes Comet propelling movement module is following.

The first step, the contextual establishment of Comet or registration.In an application program, create a new Comet context, perhaps register to a Comet context that has existed.The purpose of doing like this is to let the application program shared environment promptly share context.

Second step, establishment handle.Be generally each client or service end and connect Handler handle of establishment, and join this handle in the shared context, the purpose of doing like this is in order to utilize handle operation shared context data.The handle meaning that defines among handle and the VC++ is similar.

The 3rd step, client are created long the connection.Be generally each client and create one to one of shared context " the long connection ".The purpose of doing like this is to keep " the long connection ", the real-time renewal of realization data, propelling movement etc.

The interaction of the 4th step, client.When a Client end carries out updating data, just push data in the shared context environmental through long the connection, other Client end is updated thereupon.

The 5th step, context environmental change, and client data changes.When context generation Data Update, all keep the long Client end that connects that corresponding the variation all taken place.

Comet uses and pushes container function relevant in the module: doPost (), onEvent ().Its succinct implementation algorithm is distinguished as follows:

DoPost () function is mainly used in the intercepting and capturing parameter, thereby obtains parameter value, moreover is to wake onEvent () function up.Its implementation algorithm is following.

The character code mode is set;

Obtain position and resource name information;

Initialized location and resource name information;

Define a CometEngine object;

Define a CometContext object;

Define a CometSelector object.

OnEvent () function is used for data message is pushed to client.Its implementation algorithm is following.

Define a PrintWriter object;

Realize the propelling movement of object data;

Refresh the PrintWriter object.

Realization based on the Streaming Media seamless migration strategy of P2P framework

We adopt the audio frequency and video seamless migration strategy based on the JMF technology.The class that we realize has been inherited the JFrame frame clsss, and has realized monitors such as ActionListener, ControllerListener and ItemListener.Wherein, comprised the response window incident monitor, use the adapter adapter be used for to the X button of System menu response, the response that menu is advanced, use e.getActionCommand () .equals (" ") to realize the judgement of click event and respond or the like operating.The interface of the employed playing module of JMF is Player, and this object flows into audio frequency and video as data flow, subsequently, this audio/video flow is led on the corresponding audio & video equipment, here we with sound equipment, screen as for example.

Player need just can carry out the broadcast of audio frequency and video through six kinds of states in the use.We are existing to be listed below these six kinds of states, respectively is Unrealized, Realizing, Realized, Prefetching, Prefetched and Stated.Wherein, every kind of state is being represented its literal meaning as its title.After calling start () function like the Stated STA representation, this Player object just gets into the state of being ready to and can play the audio/video flow of loading at any time.

Under the P2P framework, to the realization of audio-video frequency media seamless migration, we only provide the key code of receiver module and action migration event module.Key code is following.

The receiver module key code is following.

Action migration event module key code is following.

In order to be provided with, to obtain and the transit time object, we have defined the TimeS class, are used to realize the serialization of object.

Realization based on the Streaming Media seamless migration strategy of C/S framework

Under the C/S framework, the function that we also need realize has congested control, based on the transmission and the Socket transfer function of small documents.

The transferring module implementation algorithm is following.

Realize the shift function of data;

Conversion breakpoint type of data is that breakpoint location converts the CString type into by the Float type;

Create the Socket socket;

The cutting of realization file;

Realize the fritter file migration.

The receiver module implementation algorithm is following.

Realize the reception of data message;

Character string is keyed in and to the operation of dependent variable in the exchange interface;

Be used for scheduling thread.

Thread module implementation algorithm is following.

Definition CActiveMovie3 type pointer variable;

Create socket, the zone that on behalf of designated communication, first parameter take place; Second parameter represented Socket type;

Realize the function of Socket receiving data information;

Resolve the character string that client transmits;

Carry out the control of playing module;

Played file.

This paper has proposed based on the DARED algorithm that rises half normal distribution; Through changing the tradition data packet discarding probability curve of earlier detection RED algorithm at random; Utilize existing luminance curve to replace original linear change curve; Thereby increased bandwidth utilization, alleviated the congestion condition of network, proved the requirement that to satisfy the network environment under the nomadic application based on the DARED algorithm that rises half normal distribution from point of theory.At system aspects, the medium migration strategy under the B/S framework has used congested control new method and has combined the Ajax technology to realize that the part of asynchronous request, webpage refreshes, and has made full use of Internet resources, has reduced waste of bandwidth.Realized the migration of type file that browser is supported,, realized the seamless migration of wireless wide area network, improved the performance of mobile device indirectly like text type, Doctype.Under the C/S framework, we change the consistent wrong-doing that transmits whole file from the angle of cutting file again, and especially to big file, its transmission efficiency can obtain very big improvement.On load mode, has the function of breakpoint transmission.Under the P2P pattern, use congested control new method-dynamically obtain network condition information to change buffer size, improved efficiency of transmission.At hardware aspect, we have used the mechanism of many network interface cards and have adopted hard disk texture storage technology.Finally, realized seamless migration strategy under three kinds of heterogeneous networks frameworks.

From Fig. 5, Fig. 6, Fig. 7, Fig. 8, Fig. 9 and Figure 10, we can find out: based on the DARED algorithm that rises half normal distribution when the TCP transmission rate is 10kb/s than traditional RED algorithm on the stability of hold queue length, show better; In transmission rate is under the situation of 10mb/s; The situation of network faces will be severe more; We find that improved DARED algorithm can be very fast according to change of network environment adjustment data packet discarding probability, the notification source transmitting terminal changes transmission rate timely, the various parameters of adjustment network; Can be faster, better hold queue length prevent congested generation.Thereby effectively prevented the generation of a large amount of packet loss incidents, can satisfy the network complex environment of Internet of Things, kept the good throughput of network, improved the performance of network.

Figure 12, Figure 13 and Figure 14 are system aspects Voice & Video seamless migration design sketchs, have all shown the accuracy and the uniformity of information before and after the migration.The improved network congestion control algolithm DRED that this patent adopts; Through controlling the delay inequality of relevant propagation delay time shake and the migration of adjacent data bag; Rapidity, flatness and correctness when having guaranteed the medium migration; The test test case has shown that this kind seamless migration strategy is effectively, and several kinds of corresponding designs have remedied the deficiency of legacy network mechanism effectively.The realization of this method will solve the migration of the medium of nomadic application, serves pervasive family, mobile learning, mobile working, Mobile business etc. better.

The concrete application

Can know from the application experiment result, should in the heterogeneous network environment of wireline-wireless coexistence, show more performance based on the DARED congestion control algorithm that rises half normal distribution, we can find the comparison through table 11; The throughput of this algorithm is the highest; Actual average bandwidth is the highest, and network resource utilization is high, changes steadily; The transmission speed that network is described is more stable; Network traffics to burst have been made congested in time control and treatment, have satisfied the performance requirement of nomadic application, can explain that in sum the DRED algorithm was all cashed out more performance when network was in bellow, between and three kinds of states of above.

Under the B/S framework; As use-case, for picture, text, we can describe its seamless migration process like this with mobile phone: derive network address after directly obtaining the Information Monitoring after the processing; And open this webpage; Touch transfer button, the control module in the self-organizing module just can be obtained contextual information, and picture or text are moved on the display device of another appointment.

When the client bought clothes in the market, rfid interrogator had obtained the information of these commodity, just can be specifying the video of playing relevant this kind clothes on the good browser, like video " Show ".Oneself and household are satisfied just can to use this strategy to carry out the migration of corresponding video to the client in order to let.Be similar to, the mobile phone floor is based on the migration of the scene photograph of Web page or leaf; Be similar to, based on the head portrait network legal power authentication of Web page or leaf.

Audio and video data streams under the P2P framework can be applied to following situation: the surveillant is when paying close attention to the video flowing that obtains through camera or detectaphone or audio stream; When seeing or the suspicion part of hearing just carries out video flowing other surveillants that lead are again helped improving investigation speed like this.Because receive the restriction of space size, realized so just no matter the monitor in which room all can watch or uppick suspicion part, is convenient to the breakthrough of case.Be similar to, can carry out the mutual biography of file, information simultaneously, reach the effect that the chat of mutual biography video segment limit is seen on a kind of limit.

Under the C/S framework, for the migration situation under the environment of internet of things, we have designed such migration situation: obtain video flowing through camera; Pass through Intemet; Carry out cloud computing, store in data center, after just " guiding " application end play, when needs move; Just with the audio-video document service end that leads, continue to play.

Network congestion control and system based on nomadic application model that this paper proposes have shown good flexibility and the stability under the various network degree of Congestion; Computation complexity is not high; Compare with traditional algorithm and to have less network resource consumption, do not influence efficiency of transmission.Emulation experiment has also proved the validity of this algorithm, can aspect property, all be improved to some extent than traditional method in performance and data.This congestion avoidance algorithm is applied to GSM; Has feasibility through the experiment proof; The Multimedia Task that can guarantee the user can be carried out seamless migration whenever and wherever possible pellucidly between distinct device, typical application comprises: mobile office (E-working), mobile learning (E-learning), mobile working (E-working), Mobile business (E-bussiness), mobile government affairs (E-Office), stock exchange (E-Exchanging), intelligence commander (E-commanding) etc.In office what is the need for of user can be selected the online stream medium data of visit and mutual with it with various available devices when wanting, and typical application comprises: video request program, online game, vision security monitoring.

Claims (2)

1. method for controlling network congestion towards nomadic application is characterized in that the concrete steps of this method comprise:

1st, when the packet arrives router; Adopt the RED algorithm to calculate average queue length

according to low pass filter; Be the mean value of the queue length on the unit interval

Wherein, is expressed as by the definite time coefficient of low pass filter, and

is expressed as the length of active formation when measuring;

2nd, max threshold threshold values

and the minimum threshold threshold values

of the 1st average queue length

that calculates of step with the drop probability curve compared; According to comparative result; Current Congestion Level SPCC is divided into three kinds of states, is respectively:

Between; Average queue length is between

and ; Think that formation is in stable state, states is set between;

Above; Average queue length is greater than

, and the state of state is set to the above state;

Bellow; Average queue length is less than

, and the state of states is set to the bellow state;

3rd, the Congestion Level SPCC of confirming according to the 2nd step carries out dynamic self adaptation adjustment, takes corresponding data packet discarding probability, and hold queue length is avoided unnecessary shake in stable scope, and concrete operations are:

When continuous 2 time intervals are in the below state; Think that then the utilance of link is low, improve the utilance of link through adjustment

value;

When continuous 2 time intervals are in the above state; It is congested to think that then link takes place; The value of dynamically adjusting

; Increase is sent congested notice to the source end, so that make the source end reduce transmission rate, thereby alleviates congested.

2. method according to claim 1 is characterized in that described method for controlling network congestion is to embody through the seamless migration fast of the medium under the different frameworks, and concrete grammar is following:

Migration strategy under the B/S framework: use the technology of Ajax technology as the front end data migration; Ajax is the fusion of several kinds of technology, the fusion between promptly asynchronous JavaScript and XML; Propelling movement module to service end realizes simultaneously, data propelling movement module that we have adopted the Comet art designs;

Migration strategy under the P2P framework: used the such mature technique of JMF to realize emphatically; The SessionManager interface that utilizes this technology to provide has simultaneously been realized the congested control in the Streaming Media transition process well; Studied method again on this basis based on the excavation and the migration of key frame; Promptly designed the key code of receiver module, guaranteed QoS with action migration event module;

Seamless migration strategy under the C/S framework: used the ripe like this control of ActiveMovie to construct player emphatically, and in the audio frequency and video file transfer, designed the function of location-based cutting shift function and congested control, guaranteed the efficient of migration.

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