CN104580371A - Methods of fragmentation, transmission and copy control for file fixed size and changeable size in opportunistic network - Google Patents
Methods of fragmentation, transmission and copy control for file fixed size and changeable size in opportunistic network Download PDFInfo
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- CN104580371A CN104580371A CN201410759132.2A CN201410759132A CN104580371A CN 104580371 A CN104580371 A CN 104580371A CN 201410759132 A CN201410759132 A CN 201410759132A CN 104580371 A CN104580371 A CN 104580371A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L67/00—Network arrangements or protocols for supporting network services or applications
- H04L67/01—Protocols
- H04L67/06—Protocols specially adapted for file transfer, e.g. file transfer protocol [FTP]
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
- H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
- H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
- H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
- H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
- H04L1/1867—Arrangements specially adapted for the transmitter end
- H04L1/188—Time-out mechanisms
Abstract
The invention discloses methods of fragmentation, transmission and copy control for a file fixed size and a file changeable size in an opportunistic network. In the invention, a large file is divided into fragmentations of the fixed size or the changeable size according to data transmission rate and connection duration of the opportunistic network; the transmission method is provided aiming at the fixed size fragmentation; fragmentation is performed through the fragmentation method provided by the invention and transmission is achieved independently; on the premise of guaranteeing transmission success rate, current network connection can be best utilized, so that transmission cost brought by fragmented control information is reduced, and besides transmission delay is lowered. The method of copy control provided by the invention has the advantages that rationalization of the copy control is realized by performing a priority ranking to transmission times, the situation that copies in one part of the fragmentation are too many while the copies in the other part of the fragmentation are few during copy transmission is avoided, the success rate of file transmission is improved and the transmission delay is lowered.
Description
Technical field
The present invention relates to file transfer technology field, more specifically relate to a kind of opportunistic network file and fix and variable-size burst, transmission, copy control methods.
Background technology
Opportunistic network, as the means of carrying out information communication under non-full-mesh network environment, derives from delay-tolerant network.Opportunistic network does not need to safeguard full link end to end, can lay the communications infrastructure in advance, and the link utilizing node mobility to set up interruption tolerance carries out efficient communication.The typical apply scene of opportunistic network is mainly the environment cannot setting up full-mesh network, as planetary networks communication, Internet Transmission from far-off regions, wild animal tracking, portable equipment networking, vehicle-carrying communication net, military self-organizing network etc.Meanwhile, along with the extensive rise of Internet of Things, need under some scene non-fully connected network can provide cost lower, dispose communication service efficiently.Therefore, the communication pattern of opportunistic network is a kind of efficiently feasible network configuration in a lot of scene.
The usual moving range of node of this type network is comparatively large, and network is in most of the cases in the state that can not be communicated with, and the route pattern which results in traditional mobile ad hoc network can not effectively be applied.The mobility that the application of network mainly relies on node carrys out assitance data multi-hop transmission with chance of meeting, and the route that mobile node and other nodes communicate with one another is Dynamic Establishing completely, while node do not understand whole network topological information.
Transfer of data in opportunistic network has himself feature, mainly by " store-carry-forward " mechanism, utilizes internodal chance of meeting to realize the transfer of data under non-fully UNICOM.On the one hand, because in network, mobile node distribution is sparse, translational speed is fast, and internodal connection opportunistic ground occurs always there is the interruption interconnection network of end-to-end path between source node and destination node.So when large files transmits in opportunistic network; the uncertainty of meeting due to node and the uncertainty of data transmission period after meeting; large files often can be caused not transmit complete and cause bust this; destination node and source node is made to need to wait for communication next time; again All Files is transmitted all again; so not only reduce the success rate of file transfer, too increase the time delay of network simultaneously.
Existing opportunistic network research does not propose effective slicing scheme for large files transmission, and the following several characteristic due to opportunistic network: link is intermittently connected, communication delay is high, Internet resources are limited, the isomerism of opportunistic network, causes several problems that the transmission of large files often occurs below:
(1) transmitting procedure is interrupted
A kind of scene that this situation large files the most easily runs into when transmitting in opportunistic network, opportunistic network inherently leans on node motion, meets, connects.It is uncontrollable that this just causes connecting the duration between node, as in vehicle-mounted net, two vehicles travelled, meeting and being separated in very of short duration time completes, probably can not more than 1 minute, the data volume can transmitted in the so of short duration time is very limited, in transmitting procedure, interruption is produced, after interruption, when reencountering to a little bigger file, still need the transmission that starts anew, the restriction connecting the duration causes transmission success rate very low.
(2) there is mistake in transmitting procedure
Opportunistic network mainly relies on wireless communication module to carry out transmitting, and as bluetooth, wifi etc., and be probably carry out when there being certain translational speed communicating, signal itself is likely more weak; In addition because frequency range used is public frequency band, and transmission environment is more complicated, is therefore probably subject to the interference of other communication equipments.Above 2 cause there will be packet loss and mistake in data transmission procedure on very large probability, and find to occur mistake after transfer of data is complete, then need whole file to resend, this can bring the waste of resource, lowers transmission success rate.
(3) spatial cache is inadequate
The transmission mechanism of opportunistic network is " carrying-Store and forword ", and therefore each node is except storing the data of oneself, also will serve as the effect of relaying, the data required for other nodes of buffer memory.This mechanism is easy to cause nodal cache pressure, if need the data of relaying comparatively large, there will be the situation that buffer memory is inadequate, can only find other nodes and carry out relaying, and this can cause propagation delay time to become large.
Summary of the invention
(1) technical problem that will solve
The technical problem to be solved in the present invention how to improve the success rate that large files transmits in opportunistic network, reduces propagation delay time simultaneously.
(2) technical scheme
In order to solve the problems of the technologies described above, the invention provides a kind of opportunistic network file fixed size sharding method, comprising the following steps:
S11, file are divided into the burst of two or more fixed size;
S12, be that each described burst generates data object, wherein said data object comprises corresponding control information and data message.
Preferably, in described step S11, the computing formula of burst size is
len
frag＝v*T
Wherein, len
fragfor described burst size, v is the message transmission rate of equipment, and T is for connecting the duration.
Preferably, described control information comprises destination address, source file numbering, source file size, source file title, source file title authorization information, data integrity degree authorization information, retrieval match information, digital signature and burst numbering;
Wherein, described source file title authorization information is for verifying the correctness of source file title;
Described data integrity degree authorization information is for verifying the integrality of the data message of corresponding burst;
Described retrieval match information is used for retrieval and the coupling of described burst;
Described burst numbering is for characterizing the position of described burst in source file;
Described digital signature is for characterizing the Data Source of described burst.
A copy control method for fixed size burst, comprising:
Sorted from less to more according to the number of transmissions by the described burst of same source file, wherein the priority of the described burst that the number of transmissions is few is high, and the priority of the described burst that the number of transmissions is many is low;
When meeting with new via node, according to burst described in priority sequence delivery from high to low, and when transmitting described burst, whether before first judging to be greater than from new via node to the probability of described destination address, via node is to the maximum probability of described destination address, if be greater than, then described burst is delivered to new via node, otherwise does not transmit.
A kind of opportunistic network file variable-size sharding method, comprises the following steps:
S31, file are divided into the index level burst of two or more fixed size;
S32, be each described index level burst generating indexes DBMS object, wherein said index level data object comprises corresponding index level control information and index level data message;
S33, each described index level burst is divided into two or more output stage burst;
S34, be that each described output stage burst generates output stage data object, wherein said output stage data object comprises output stage control information and output stage data message.
Preferably, in described step S33, the computing formula of output stage burst size is
len
trans＝T
ava*V
ava*λ
Wherein, len
transfor the size of described output stage burst, T
avafor on average connecting the duration, V
avafor average transmission rate, λ is the inverse transmitting the number of described output stage burst within the connection duration of prediction.
Preferably, the computing formula of described average connection duration is:
T
ava＝T
old*α*γ
k+T
current*(1-α*γ
k)
Wherein, T
oldfor history on average connects the duration, T
currentfor the current connection duration, α ∈ [0,1], characterize described history on average to connect the duration and connect average the proportion accounted in the duration, γ ∈ [0,1) be time decay factor, k is the number that described source file arrives described destination address elapsed time unit.
Preferably, the computing formula of described average transmission rate is:
V
ava＝V
old*α*γ
k+V
current*(1-α*γ
k)
Wherein, V
oldfor history average transmission rate, V
currentfor current transmission rate, α ∈ [0,1], characterizes the proportion that described history average transmission rate accounts in average transmission rate, and γ ∈ [0,1) be time decay factor, k is the number that described source file arrives described destination address elapsed time unit.
A transmission method for variable-size burst, comprises the following steps:
S41, by described index level burst with mate with the node that it meets, if the match is successful, then described index level burst is divided into two or more output stage burst, and is that output stage burst described in each generates output stage data object;
S42, described node judge the data object whether having had described output stage burst, if have, then return the information of rejection, otherwise, whether the Data Source of described output stage burst is judged safely, if safety, then returns reception information, otherwise, return rejection information;
S43, described output stage burst send data message to described node;
After S44, described node receive described data message, the integrity degree of the data message received is judged, if the data message received is complete, then described data message is deposited into database; Otherwise, abandon the described data message of reception;
If S45 described output stage burst is the initial burst of described source file, then set up interruptible price data object, the data message of described output stage burst is read in the file of described destination address sensing;
S46, described node at the end position of described index level burst according to the original position of described output stage burst in described index level burst and described output stage burst, carry out the restructuring of output stage fragment data information, obtain described index level burst;
The data message of index level burst is recombinated by S47, described node, obtains source file.
Preferably, in described step S45, in the process of transfer of data, run into interruption, then the interrupt flag bit of described interruptible price data object is set; When described node runs into other nodes, described interruptible price data object is passed to the new node met; Described new node searches the data object corresponding with described index level burst, if find, then resumes from the end byte of described reception.
(3) beneficial effect
The invention provides a kind of opportunistic network file to fix and variable-size burst, transmission, copy control methods, wherein opportunistic network file fixed size sharding method, and between the opportunistic network node of present communications, state is irrelevant also has nothing to do with whole opportunistic network interior joint collision probability, there is stronger robustness, adapt to the scene that reliability is poor, and because burst size is identical, controllability is comparatively strong, is applicable to very much copy and controls.Opportunistic network file variable-size sharding method is that basis determines burst size when the network condition between the first two communication node is connected the duration with history, because in close relations with current network conditions, is therefore suitable for network environment situation relatively reliably; The present invention, by large files is carried out burst, under the prerequisite ensureing transmission success rate, can utilize current network to connect to greatest extent, decrease the transport overhead that burst control information brings, reduce propagation delay time simultaneously;
Copy control method of the present invention, realize the rationalization that copy controls, avoid the copy occurring certain a part of burst in transfer copies too much, and the situation that the copy of other part bursts is very few, be conducive to the success rate improving large files transmission, and reduce propagation delay time.
Accompanying drawing explanation
In order to be illustrated more clearly in the embodiment of the present invention or technical scheme of the prior art, be briefly described to the accompanying drawing used required in embodiment or description of the prior art below, apparently, accompanying drawing in the following describes is only some embodiments of the present invention, for those of ordinary skill in the art, under the prerequisite not paying creative work, other accompanying drawing can also be obtained according to these accompanying drawings.
Figure 1A is the flow chart of opportunistic network file fixed size sharding method of the present invention;
Figure 1B is the flow chart of the opportunistic network file fixed size sharding method of a preferred embodiment of the present invention;
Fig. 2 is the transmission method flow chart of opportunistic network file fixed size burst in the present invention;
Fig. 3 is the transmission method flow chart of opportunistic network file variable-size burst of the present invention.
Embodiment
Below in conjunction with drawings and Examples, the present invention is described in further detail.Following examples for illustration of the present invention, but can not be used for limiting the scope of the invention.
Figure 1A is the flow chart of opportunistic network file fixed size sharding method of the present invention; Described opportunistic network file fixed size sharding method, comprises the following steps:
S11, file are divided into the burst of two or more fixed size;
S12, be that each described burst generates data object, wherein said data object comprises corresponding control information and data message.
Figure 1B is the flow chart of the opportunistic network file fixed size sharding method of a preferred embodiment of the present invention.Preferably, in described step S11, the computing formula of burst size is
len
frag＝v*T
Wherein, len
fragfor described burst size, v is the message transmission rate of equipment, and T is for connecting the duration.
In described step S11, first exceed setting threshold with file size before carrying out file fragmentation and judge for condition, if so, then described file is carried out burst, otherwise, do not carry out burst, directly transmit.
Described control information comprises destination address, source file numbering, source file size, source file title, source file title authorization information, data integrity degree authorization information, retrieval match information, digital signature and burst numbering; Wherein, described source file title authorization information is for verifying the correctness of source file title; Described data integrity degree authorization information is for verifying the integrality of the data message of corresponding burst; Described retrieval match information is used for retrieval and the coupling of burst; Described burst numbering is for characterizing the position of described burst in source file; Described digital signature is for characterizing the Data Source of described burst.
Opportunistic network file fixed size sharding method is fixed due to the size of burst, and institute thinks fixed size sharding method.Opportunistic network has open and transmitting procedure uncontrollability, therefore relative to other reliable network, ensure the correct transmission of data, need to transmit more multi-control information while transfer of data, by these control informations, receiving terminal judges that whether the data message received is safe, complete.These control informations are organized with xml form, integrates and transmit, as follows:
Above, described control information with all with <Haggle/> for root node, node <Haggle/> has an attribute persistent, when this property value is yes, described data object will be stored in database, during for no, then do not enter database.Data object be divide into two classes by the setting of this attribute: a class is associated with database, while storing data information, this data object is put into database, sets up the index of data, retrieves so that follow-up; Another kind of is have nothing to do with database, just plays the function that data object transmits.
Node <Attr/> is the description to data, opportunistic network is when content-based transmission, the content of this node is the keyword of retrieval, for mating with destination node (node that described destination address is corresponding), is retrieval match information.This attribute is a key-value pair, is made up of name and value, and name is as the attribute of this node, and value is then as the value of this node.This part is added according to data characteristics by user, and a data object can have multiple <Attr/>.
Node <Data/> has 4 partial contents to form: the data_len 1, characterizing source file size, this value is as the attribute of <Data/> node.2, path FilePath deposited by the file characterizing destination address.3, the FileName of source file title is characterized.4, in order to verify the source file title authorization information FileHash that source file title is added.The length taking data object deposit position and data message accurately can be facilitated by the content of <Data/>.
Last part is node <Signature/> is digital signature, this part is the value of sha-1, is used for characterization data source, for determining Information Security.
Except xml above, control information also has two very important information: DataHash and Sourceid.DataHash is the sha-1 value calculated according to source file content, can verification of data integrity by this value.Sourcid is the sha-1 calculated by described <Attr/> key-value pair, source filename, creation-time, source file size and DataHash, this computational process ensure that the uniqueness of this value, therefore can as the mark of source file.
From above describe, indispensable during the transmission that in control information, each field is correct for data, reliable, complete, when carrying out burst, in order to ensure the reliability of burst, above those fields still cannot lack.In addition, in order to characterize the characteristic of burst, other fields can be added on original field basis, thus control information is increased further.In order to characterize the position of burst at source file, define a new field, FragmentId, i.e. burst numbering, the value of this field is taken as which burst that this burst is source file, and this information controls to have critical significance for burst merging and based on the copy of burst.
When network reliability is poor, in order to reduce the dependence of burst to network environment, burst size is determined to be set as haveing nothing to do with current network by we, and burst size can ensure to complete transmission in more severe network environment as far as possible simultaneously.Fixed size sharding method has another one advantage, and namely each burst is the determination of independently equality, this make we can using each burst as one independently individuality treat, in the copy based on burst controls there is very large meaning.
The factor affecting burst size is poor medium transmission rate and the worst average connect hours, in common once connection, namely at least ensure that a burst can transmission success.
The rating blocks speed of wifi, bluetooth is all higher, does not reach nominal rated speed in the actual environment, and the facility information speed of different model is also different.In the test of opportunistic network experiment porch, find that the average speed that wifi can realize is 300KB/s, the speed that bluetooth can reach is at 100KB/s.By studying related data, reliable test result.
Application of formula
len
frag＝v*T
In view of the duration generally once connected is greater than 10s, value 10s here.Thus can to obtain burst size be 1000KB.
Control information expense after burst cost and burst, if make to carry out burst to comparatively small documents, effect is deteriorated on the contrary, therefore, as far as possible can on the basis of transmitting at guarantee large files, in order to not affect the transmission of small documents in opportunistic network as far as possible, set in this slicing scheme a burst and setting threshold len
thr, be do not carry out burst when file size is less than this value, directly transmit, this threshold value is set as 10MB.
After burst is carried out to file, each burst just can as one independently individuality transmit, in order to reduce burst and merge the expense brought, do not merge at the node as relaying, only just can merge burst in destination node, the data object generated after merging is identical with source file.
Fig. 2 is the transmission method flow chart of opportunistic network file fixed size burst in the present invention, and described fixed size burst is the burst utilizing above-mentioned opportunistic network file fixed size sharding method to obtain, and comprises the following steps:
S21, to mate by described burst with the node that it meets, if the information matches success of the retrieval match information of described burst and described node, then the control information of described burst is passed to described node, otherwise the node that described burst and other meet is mated;
S22, described node judge the data object whether having had described burst according to the source file of described burst numbering and burst numbering, if for, then return the information of rejection, otherwise, whether the digital signature according to described burst judges safely the Data Source of described burst, if safety, then returns reception information, otherwise, return rejection information;
S23, described burst send data message to described node;
After S24, described node receive described data message, the integrity degree of data integrity degree authorization information to the data message received according to described burst judges, if the data message received is complete, then deposits into database by described data message; Otherwise, abandon the described data message of reception;
The all bursts obtained are numbered according to described burst by S25, described node, carry out the restructuring of data message.
Transmit described control information or transmit in the process of described data message, if there is mistake in transmitting procedure, then the burst information producing mistake being retransferred; If run into interruption in transmitting procedure, then the information transmitted is stored in the buffer memory of described node, when by the time reconnecting, continues transmission.
The copy control method of the burst obtained according to above-mentioned fixed size sharding method is specially:
Deposit a table in each node, the content in table is the transmission situation of all bursts, as shown in table 2 below:
Table 2
Sorted from less to more according to the number of transmissions by the burst of same source file, wherein the priority of the described burst that the number of transmissions is few is high, and the priority of the described burst that the number of transmissions is many is low; When meeting with new via node, according to burst described in priority sequence delivery from high to low, as above in table, belong to 1,2,3 bursts in 6 bursts of source file 2 together and be passed through twice, in order to make 4,5,6 copy amounts existed in a network as far as possible identical with 1,2,3 burst quantity in current network, therefore preferentially transmit 4,5,6, if transmitted 4,5,6, connected and still continue just to consider transmission 1,2,3.
If a file is larger, and it is shorter to connect the duration, first time produces interruption after transmitting burst 1,2,3, if do not do above-mentioned strategy, when meeting afterwards at every turn, always from the 1st burst, then the smaller burst of a large amount of id may be there is in network, and the larger burst of id and cannot being transferred in network, therefore cause large files cannot transmit successfully.After adopting above-mentioned strategy, the problems referred to above can be evaded preferably, realize the validity of sliced transmission.Said method is mainly for fixed size sharding method.
When transmitting described burst, before whether the probability first judging from described new via node to described destination address is greater than, via node is to the maximum probability of described destination address (table 2, via node is to the probability of destination node), if be greater than, then described burst is delivered to described new via node, and via node described in updating form 2 is to the probable value of destination node, otherwise do not transmit.
Fixed size sharding method can improve the transmission success rate of large files, but this strategy does not take into full account the concrete condition of communication node, and in order to ensure transfer of data, it is little that the burst size of setting is also tried one's best, cause so the redundancy that control information is introduced not being dropped to minimum; In order to reduce the redundancy that control information brings as far as possible, propose the sharding method of burst variable size, this burst size takes full advantage of historical data transmission of information, makes burst as far as possible large according to historical information, reduce burst quantity with this, thus reduce control information total amount.
Opportunistic network file variable-size sharding method of the present invention, comprises the following steps:
S31, file are divided into the index level burst of two or more fixed size;
S32, be each described index level burst generating indexes DBMS object, wherein said index level data object comprises corresponding index level control information and index level data message;
S33, each described index level burst is divided into two or more output stage burst;
S34, be that each described output stage burst generates output stage data object, wherein said output stage data object comprises output stage control information and output stage data message.
In order under the redundancy prerequisite reducing control information introducing as far as possible, facilitate retrieval and the merging of burst in opportunistic network, first large files is divided into the burst of suitable fixed size herein, the base unit that such burst is retrieval and merges, claims such burst to be index level burst.Then index level burst is carried out to the burst of variable-size again, decide burst size according to the situation of communication node, make burst as far as possible large, reduce burst quantity with this, thus reduce control information total amount, claim such burst to be output stage burst.
The effect of index level burst is mainly used to retrieve, and the size of such burst determines primarily of two aspects: facilitate burst to retrieve and can not increase the redundancy that control information brings.Only have complete index level burst to be retrieved, if index level burst is excessive, then may occur that via node have received certain data, but because there is no complete index level burst, so cannot carry out relaying, can increase propagation delay time like this, therefore index level burst is unsuitable excessive.If index level burst is too small, can transmit multiple index level burst in a normal chance connects, then index level burst will increase the redundancy that control information is introduced, and cannot play the advantage of this sharding method.Therefore index level burst is unsuitable too small.
Based on above-mentioned analysis, index level burst size will be determined according to the characteristic of opportunistic network.Here can use for reference the defining method of fixed size burst, connect the duration according to chance networking, and the size of the transmission rate determination index level burst of equipment, namely the computing formula of index level burst size is
len
frag＝v*T
Wherein, len
fragfor described index level burst size, v is the message transmission rate of equipment, and T is for connecting the duration.
If complete index burst can be transmitted within the duration, then directly transmit index level burst, do not need to carry out transmitting stage burst again, therefore in described step S31, first exceed index level fragmentation threshold with file size before carrying out burst to judge for condition, if so, then carry out burst, otherwise, do not carry out burst.Each file will carry out index level burst, if file itself is less than index level burst size, then only produces an index level burst.
In described step S33, before carrying out burst, first exceed output stage fragmentation threshold with index level burst and judge for condition, if so, then carry out burst, otherwise do not carry out burst, directly transmit.
Described index level control information comprises destination address, source file numbering, source file size, source file title, source file title authorization information, data integrity degree authorization information, retrieval match information, digital signature and burst numbering; Wherein, described source file title authorization information is for verifying the correctness of source file title; Described data integrity degree authorization information is for verifying the integrality of the data message of manipulative indexing level burst; Described retrieval match information is used for retrieval and the coupling of index level burst; Described burst numbering is for characterizing the described position of index level burst in source file; Described digital signature is for characterizing the Data Source of described index level burst.
In described step S33, the computing formula of output stage burst size is
len
trans＝T
ava*V
ava*λ
Wherein, len
transfor the size of described transmitting stage burst, T
avafor on average connecting the duration, V
avafor average transmission rate, λ is the inverse transmitting the number of described output stage burst within the connection duration of prediction, our value 1/2.2, namely 2.2 bursts can be transmitted within the connection duration of prediction, this value, can ensure can transmit one or two bursts within the connection duration, neither affect sliced transmission success rate, control information can be reduced to minimum again.
In order to obtain the historical information of node collision probability and transfer of data, propose a kind of Prophet routing algorithm TV_Prophet of improvement herein, T represents this routing algorithm and comprises the historical information connecting the duration, and V represents the historical information that this routing algorithm comprises internodal data transmission rate.
Routing iinformation is stored in a chained list by TV_Prophet algorithm, and list structure is as follows:
The storage organization of table 1 TV_Prophet
Collision probability value corresponding to two nodes can be found by Sourceid with Destid two values, be on average connected duration and average transmission rate.The value of P is collision probability, and its computational methods are the same with Prophet method, do not repeat here.
Wherein, the computing formula of described average connection duration is:
T
ava＝T
old*α*γ
k+T
current*(1-α*γ
k)
Wherein, T
oldfor history on average connects the duration, T
currentfor the current connection duration, α ∈ [0,1], characterize described history on average to connect the duration and connect average the proportion accounted in the duration, γ ∈ [0,1) be time decay factor, k is the number that described source file arrives described destination address elapsed time unit.
The computing formula of described average transmission rate is:
V
ava＝V
old*α*γ
k+V
current*(1-α*γ
k)
Wherein, V
oldfor history average transmission rate, V
currentfor current transmission rate, α ∈ [0,1], characterizes the proportion that described history average transmission rate accounts in average transmission rate, and γ ∈ [0,1) be time decay factor, k is the number that described source file arrives described destination address elapsed time unit.
Described output stage control information comprises described destination address, source file numbering, source file size, source file title, source file title authorization information, data integrity degree authorization information, digital signature, burst numbering, the original position of described output stage burst in described index level burst and the described output stage burst end position at described index level burst; Wherein, described source file title authorization information is for verifying the correctness of source file title; Described data integrity degree authorization information is for verifying the integrality of the data message of corresponding output stage burst; Described burst numbering is for characterizing the described position of index level burst in source file; Described digital signature is for characterizing the Data Source of described index level burst.
Fig. 3 is the transmission method flow chart of opportunistic network file variable-size burst of the present invention, and described variable-size burst is the burst utilizing above-mentioned opportunistic network file variable-size sharding method to obtain; Said method comprising the steps of:
S41, by described index level burst with mate with the node that it meets, if the information matches success of the retrieval match information of described index level burst and described node, then described index level burst is divided into two or more output stage burst, and is output stage burst generation output stage data object described in each; Otherwise the node that described index level burst and other and its meet is mated;
S42, described node is numbered according to the source file of described output stage burst, burst is numbered, the original position of described output stage burst in described index level burst and described output stage burst judge the data object whether having had described output stage burst at the end position of described index level burst, if have, then return the information of rejection, otherwise, whether the Data Source of digital signature to described output stage burst according to index level burst corresponding to described output stage burst judges safely, if safety, then return reception information, otherwise, return rejection information,
S43, described output stage burst send data message to described node;
After S44, described node receive described data message, the integrity degree of data integrity degree authorization information to the data message received according to described output stage burst judges, if the data message received is complete, then deposits into database by described data message; Otherwise, abandon the described data message of reception;
If S45 described output stage burst is the initial burst of described source file, then set up interruptible price data object, the data message of described output stage burst is read in the file of described destination address sensing; Otherwise, judge whether to there is interruptible price data object, if exist, directly the data message of described output stage burst is read in the file of described destination address sensing, otherwise, by the information of output stage burst stored in buffer memory, until set up interruptible price data object, then burst is write in interruptible price data object specified file;
S46, the follow-up data object received write data in the file of interruptible price data object sensing in order successively, if whole file receives smoothly, described node is according to the original position of described output stage burst in described index level burst and the described output stage burst end position at described index level burst, carry out the restructuring of output stage fragment data information, obtain described index level burst, delete interruptible price data object;
S47, described node are numbered according to described burst, are recombinated by the data message of index level burst.
Described interruptible price data object comprises interrupt flag bit, the end byte of reception, the total bytes of described source file, described burst numbering and described destination address.
In described step S45, run into interruption in the process of transfer of data, then the interrupt flag bit arranging described interruptible price data object is 1, and is inserted in interruptible price data-object index table and waits for and resuming; When described node runs into other nodes, described interruptible price data object is passed to the new node met; Described new node searches the data object corresponding with described index level burst, if find, is then set to 0 by interrupt flag bit, resumes from the end byte of described reception, otherwise, retransfer from the original position of described output stage burst.
The copy control method of above-mentioned index level burst, deposits a table in each node, the content in table is the transmission situation of all bursts, as shown in table 3 below:
Table 3
Sorted from less to more according to the number of transmissions by the index level burst of same source file, wherein the priority of the described index level burst that the number of transmissions is few is high, and the priority of the described index level burst that the number of transmissions is many is low; When meeting with new via node, according to index level burst described in priority sequence delivery from high to low, as above in table, belong to 1,2,3 bursts in 6 bursts of source file 2 together and be passed through twice, in order to make 4,5,6 copy amounts existed in a network as far as possible identical with 1,2,3 burst quantity in current network, therefore preferentially transmit 4,5,6, if transmitted 4,5,6, connected and still continue just to consider transmission 1,2,3.
If a file is larger, and it is shorter to connect the duration, first time produces interruption after transmitting burst 1,2,3, if do not do above-mentioned strategy, when meeting afterwards at every turn, always from the 1st burst, then the smaller burst of a large amount of id may be there is in network, and the larger burst of id and cannot being transferred in network, therefore cause large files cannot transmit successfully.After adopting above-mentioned strategy, the problems referred to above can be evaded preferably, realize the validity of sliced transmission.
When transmitting described index level burst, before whether the probability first judging from described new via node to described destination address is greater than, via node is to the maximum probability (table 3, the via node of record is to the probability of destination node) of described destination address, if be greater than, then described index level burst is delivered to described new via node, and via node described in updating form 3 is to the probable value of destination node, otherwise do not transmit.
Large files can be divided into independently little burst to transmit by the sharding method of the application layer that the present invention proposes, when interrupting producing, a point sector-meeting buffer memory for transmission success gets off, when connection is set up again, continue to transmit the burst also do not received, thus the scrappy connect hours can be utilized to realize the transmission of large files, namely realize the breakpoint transmission function of application layer.When in transmitting procedure, if run into mistake, then only need the burst producing mistake to carry out retransmitting, greatly reduce the waste of resource.After burst, if run into the inadequate situation of spatial cache, can transmit as far as possible many bursts, sliced transmission method in cooperation, greatly can improve transmission success rate and congestion control ability in this case.
The sharding method of the application layer that the present invention proposes is all carry out burst in application layer, each fragment packets is containing control information and data object, eachly can independently to transmit by burst, this burst in application layer can be useful in different host-host protocols as UDP, TCP, and in different transmission mechanisms, as wifi, bluetooth, Ethernet etc.
Connect duration, communication quality etc. between the randomness that opportunistic network node meets, node very unreliable, these characteristics bring a lot of problem to large files transmission.In order to improve large files transmission success rate in opportunistic network, the present invention is transmitted after large files is carried out burst, can realize the function such as breakpoint transmission, error detection re-transmission.Opportunistic network isomerism, namely communication equipment may be the distinct device such as bluetooth, wifi, if burst carries out in physical layer or data link layer, needs to consider different transmission equipments, needs the different agreement of definition and field for different equipment.In order to avoid this situation, the sharding method proposed in invention realizes in application layer, and this sharding method can be concerned about what agreement data link layer and physical layer adopt, and has very strong transplantability.
Above execution mode is only for illustration of the present invention, but not limitation of the present invention.Although with reference to embodiment to invention has been detailed description, those of ordinary skill in the art is to be understood that, various combination, amendment or equivalent replacement are carried out to technical scheme of the present invention, do not depart from the spirit and scope of technical solution of the present invention, all should be encompassed in the middle of right of the present invention.
Claims (10)
1. an opportunistic network file fixed size sharding method, is characterized in that, comprise the following steps:
S11, file are divided into the burst of two or more fixed size;
S12, be that each described burst generates data object, wherein said data object comprises corresponding control information and data message.
2. method according to claim 1, is characterized in that, in described step S11, the computing formula of burst size is
len
frag＝v*T
Wherein, len
fragfor described burst size, v is the message transmission rate of equipment, and T is for connecting the duration.
3. method according to claim 1 and 2, it is characterized in that, described control information comprises destination address, source file numbering, source file size, source file title, source file title authorization information, data integrity degree authorization information, retrieval match information, digital signature and burst numbering;
Wherein, described source file title authorization information is for verifying the correctness of source file title;
Described data integrity degree authorization information is for verifying the integrality of the data message of corresponding burst;
Described retrieval match information is used for retrieval and the coupling of described burst;
Described burst numbering is for characterizing the position of described burst in source file;
Described digital signature is for characterizing the Data Source of described burst.
4. a copy control method for fixed size burst, is characterized in that, comprising:
Sorted from less to more according to the number of transmissions by the described burst of same source file, wherein the priority of the described burst that the number of transmissions is few is high, and the priority of the described burst that the number of transmissions is many is low;
When meeting with new via node, according to burst described in priority sequence delivery from high to low, and when transmitting described burst, whether before first judging to be greater than from new via node to the probability of described destination address, via node is to the maximum probability of described destination address, if be greater than, then described burst is delivered to new via node, otherwise does not transmit.
5. an opportunistic network file variable-size sharding method, is characterized in that, comprise the following steps:
S31, file are divided into the index level burst of two or more fixed size;
S32, be each described index level burst generating indexes DBMS object, wherein said index level data object comprises corresponding index level control information and index level data message;
S33, each described index level burst is divided into two or more output stage burst;
S34, be that each described output stage burst generates output stage data object, wherein said output stage data object comprises output stage control information and output stage data message.
6. method according to claim 5, is characterized in that, in described step S33, the computing formula of output stage burst size is
len
trans＝T
ava*V
ava*λ
Wherein, len
transfor the size of described output stage burst, T
avafor on average connecting the duration, V
avafor average transmission rate, λ is the inverse transmitting the number of described output stage burst within the connection duration of prediction.
7. method according to claim 6, is characterized in that, the computing formula of described average connection duration is:
T
ava＝T
old*α*γ
k+T
current*(1-α*γ
k)
Wherein, T
oldfor history on average connects the duration, T
currentfor the current connection duration, α ∈ [0,1], characterize described history on average to connect the duration and connect average the proportion accounted in the duration, γ ∈ [0,1) be time decay factor, k is the number that described source file arrives described destination address elapsed time unit.
8. the method according to claim 6 or 7, is characterized in that, the computing formula of described average transmission rate is:
V
ava＝V
old*α*γ
k+V
current*(1-α*γ
k)
Wherein, V
oldfor history average transmission rate, V
currentfor current transmission rate, α ∈ [0,1], characterizes the proportion that described history average transmission rate accounts in average transmission rate, and γ ∈ [0,1) be time decay factor, k is the number that described source file arrives described destination address elapsed time unit.
9. a transmission method for variable-size burst, is characterized in that, comprises the following steps:
S41, by described index level burst with mate with the node that it meets, if the match is successful, then described index level burst is divided into two or more output stage burst, and is that output stage burst described in each generates output stage data object;
S42, described node judge the data object whether having had described output stage burst, if have, then return the information of rejection, otherwise, whether the Data Source of described output stage burst is judged safely, if safety, then returns reception information, otherwise, return rejection information;
S43, described output stage burst send data message to described node;
After S44, described node receive described data message, the integrity degree of the data message received is judged, if the data message received is complete, then described data message is deposited into database; Otherwise, abandon the described data message of reception;
If S45 described output stage burst is the initial burst of described source file, then set up interruptible price data object, the data message of described output stage burst is read in the file of described destination address sensing;
S46, described node at the end position of described index level burst according to the original position of described output stage burst in described index level burst and described output stage burst, carry out the restructuring of output stage fragment data information, obtain described index level burst;
The data message of index level burst is recombinated by S47, described node, obtains source file.
10. method according to claim 9, is characterized in that, in described step S45, runs into interruption in the process of transfer of data, then arrange the interrupt flag bit of described interruptible price data object; When described node runs into other nodes, described interruptible price data object is passed to the new node met; Described new node searches the data object corresponding with described index level burst, if find, then resumes from the end byte of described reception.
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