CN103840917A - Multipath parallel transmission scheme based on network coding - Google Patents

Abstract

The invention provides a multipath parallel transmission scheme based on network coding. The multipath parallel transmission scheme solves that problems that when multipath parallel transmission is conducted in a wireless network, packets are lost frequently due to the unreliability of the wireless network and out-of-sequence is caused by the difference of multiple paths. According to the multipath parallel transmission scheme based on network coding, network coding is introduced, the limit that the packets are received in sequence in traditional reliable sequential transmission is broken, and the priority is given to the number of the data packets instead of the sequence of the data packets. Redundant data packets are added according to the packet loss rate, possibly-lost packets in the transmission process is actively supplemented, and retransmission is avoided. Transmission management is conducted in groups, it is guaranteed that a congestion window is increased rapidly and fully, and the tolerance of a system to time-out and packet loss is enhanced. The multipath parallel transmission scheme based on network coding is adopted to conduct wireless multimedia data transmission, the dynamics and the unreliability of a wireless heterogeneous network can be actively prevented, the scheme can be adapted to the dynamics and the unreliability of the wireless heterogeneous network, the out-of-sequence and packet loss problems are solved, retransmission is greatly reduced, the throughput capacity is greatly improved, and efficient high-quality wireless multimedia transmission services are provided.

Description

A kind of multidiameter delay transmission plan of coding Network Based

Technical field

The present invention relates to communication technique field, communication data transmission technology.Be specifically related to the realization that the multidiameter delay in conjunction with network code transmits on SCTP.

Background technology

Along with social development, people are for high-quality, high efficiency and the demand of multi-media radio transmission service is more and more higher easily.A lot of cities have been all for live video stream has been set up urban network all over the world, for example onboard wireless network.Popular along with ubiquitous broadband mobile network access technology, multidiameter delay transmission CMT(Concurrent Multipath Transfer) become one of the most desirable mode strengthening multimedia transmission.At present, the realization of CMT is mainly based on SCTP SCTP(Stream Control Transmission Protocol), research shows, SCTP can effectively realize multidiameter delay transmission.SCTP CMT has good bandwidth polymerizing power, fault-tolerance and load balance ability, and these features can provide effective data transport service for multimedia content delivery.

But CMT is having a very serious packet to reset defect.Because multipath has larger path difference (as bandwidth, time delay and packet loss), Out-of-sequence packets arrives receiving terminal, receiving terminal needs the packet having arrived on the very fast path of buffer memory, one side, wait for the packet postponing on slower path on one side, carry out packet rearrangement, ensure the orderly payment of packet.Buffer memory serious when Out-of-sequence packets and mobile terminal is subject in limited time, and the performance of CMT can be subject to the restriction that buffer memory blocks, and causes connecting entering idle condition.Have at present a lot of research work to be all devoted to slow down data rearrangement, it is mainly challenged is how under definite path evaluation, to carry out data dispatch.These researchs are all deferred to strict ordered data and are received, and its transmission performance is still subject to receiving the impact of the data rearrangement in buffer memory passively.

Another problem that need to be concerned about is that the unreliability of wireless channel causes packet loss and often retransmit occurring.In order to reach the object of reliable data transmission, sometimes carry out re-transmission more than once for same packets need.In this case, judge that packet loss reason is that congested or wireless mistake is very important.Some research work attempt to strengthen the reliability of CMT, save the expense retransmitting.The uniqueness of individual data bag is considered in these researchs, carries out the loss detection of packet.But this almost can not reduce re-transmission.

In recent years, for studies show that of network code, transport layer network coding can provide a kind of simple method to break the strong constraint relation between packet and transmission sequence number TSN.Although constraining in reliable transmission in order this is very important, and in fact the final purpose of transport layer is to carry out reliable transfer of data.Like this, receiving terminal is only concerned about the quantity that packet arrives, and is indifferent to the order that packet arrives, and does not need to reorder.Moreover in the time there is packet loss, encoded packets can substitute mutually and supplement, and does not need to retransmit specific packet.In TCP or SCTP, coding and decoding calculating bring larger delay can to the reply of confirming, causes HARQ ARQ(Automatic Repeat reQuest) and the hydraulic performance decline of congestion control.The proposition of Online ACK mechanism can address this problem, and network code can and effectively be carried out with TCP compatibility.Subsequently, network code and online ACK mechanism are applied in MPTCP, can improve the throughput of multi-path network.But, because being one, MPTCP newer SCTP CMT is transplanted to the idea on TCP, not formation standard.Moreover MPTCP does not have the complete characteristic of SCTP, for example polylith data packet format flexibly, heartbeat mechanism and select to confirm, these characteristics can with network code cooperation, optimize its performance.Existing research simultaneously does not relate to yet to be optimized congestion control and distinguishes the packet loss reason in wireless environment.

Summary of the invention---claims part

In view of this, the present invention proposes a kind of multidiameter delay transmission plan of coding Network Based, in the multidiameter delay transmitting procedure of SCTP, in conjunction with network code, break the traditional transmitting thought receiving according to the order of sequence, the uniqueness of eliminating packet, provides high performance Multimedia Data Transmission service.The present invention has defined a network code computing based on group, according to the raw data packets generating network encoded packets in a group; Adopt one to mix rapid data distribution policy, chosen the path with maximum spatial accommodation and carry out data allocations, and add as required redundancy; Propose a group transfer management mechanism, carried out the management such as congestion control, re-transmission.The present invention can avoid packet to reset effectively, and the packet of compensating missing solves because path difference is different in nature and mobile terminal stores limits the buffer memory obstruction causing, initiatively adapts to the dynamic of wireless network, for mobile subscriber provides efficient multimedia transmission.

1, a multidiameter delay transmission plan for coding Network Based, its step comprises:

A) the network code computing based on group.Utilize bandwidth and packet loss to determine group number, the packet in a group is carried out to linear combination network code;

B) mix rapid data distribution policy.Selection has the path of maximum spatial accommodation and carries out data allocations, often distributes one group of data, all adds certain redundant data packets at buffer memory end, path;

C) group transfer management mechanism.Carry out transfer management taking group as unit, comprise that congestion control, the re-transmission of necessity and the record of packet loss upgrade.

2, the network code computing based on group as claimed in claim 1, is characterized in that:

A) two-way time, RTT measured: send HEARTBEAT and obtain RRTT, and contrast SRTT, in the time that RRTT and SRTT approach, the value of selection SRTT is as the RTT in path; When RRTT and SRTT gap are when larger, select the RTT of RRTT as path;

B) bandwidth BW is estimated: obtain bandwidth sample by the traffic volume of data in measuring intervals of TIME and the ratio of Measuring Time, then carry out smoothing processing and obtain bandwidth estimation value;

C) group number upgrades: utilize RTT two-way time, bandwidth BW and packet loss pe to determine group number;

D) network code bag generates: according to group number division group, the packet in a group is carried out to linear combination coding, and in packet, insert corresponding encoded information.

3, mix as claimed in claim 1 rapid data distribution policy, it is characterized in that:

A) Path selection: select the path with maximum spatial accommodation to carry out data allocations, wherein maximum spatial accommodation refers to, at a time path allow the data volume that sends with sent but still the difference of unacknowledged data volume be multiplied by successfully again transmission rate;

B) add redundancy: the packet number and the packet loss that are fitted on certain path according to certain component carry out redundancy calculating, add redundant data packets, the data packet number that ensures can successfully to arrive on this independent pathway receiving terminal is not less than the packet number of its distribution.

4, as claimed in claim 1 group of transfer management mechanism, is characterized in that:

A) congestion control based on group: for the group GC of current sensing, if SACK confirms a new TSN in GC, carry out and start slowly or congestion avoidance algorithm; If the report of the loss of GC arrives more than three times, carry out corresponding quick retransmission algorithm according to packet loss reason; If overtime GTO, carries out the similar overtime retransmission algorithm with standard SCTP;

B) packet loss pe calculates: for the current group GP that finally completes transmission, record the packet that GP receives by the sum of transmission packet and success on each path, calculate the packet loss in each path.

The present invention has following technique effect:

1, in the present invention, carry out network code taking group as unit and mix transmission encoded packets or raw data packets.No matter data are not surrounded by and encode, can regard the encoded packets through linear combination as.Like this, each encoded packets has only represented a relation of group, and encoded packets is not independent and unique, and the encoded packets of any loss can replace by other encoded packets that belong to this group, simultaneously between the encoded packets in same group not sequentially.As long as receiving terminal is received the encoded packets of enough numbers, just can translate initial data, needn't consider Out-of-sequence packets problem, appropriate redundancy also can greatly reduce even to be avoided retransmitting.

2, in the present invention, transmit control taking group as unit.Transmitting terminal is paid close attention to the acknowledge message that belongs to a group, instead of the acknowledge message of some packets.As long as confirmed to belong to the TSN of current group in SACK, cwnd just can carry out corresponding growth; SACK is continuous while above not confirming any TSN that belongs to current group three times, just carries out fast and retransmits; GTO is overtime, carries out overtime re-transmission.Congestion control taking group as unit, has ensured the growth of telling of cwnd, simultaneously for bag and overtime tolerance are strengthened greatly.

Brief description of the drawings

Fig. 1 is entire system framework of the present invention;

Fig. 2 is multi-path network coding principle figure;

Fig. 3 is group number update algorithm flow chart;

Fig. 4 is network code handbag form schematic diagram;

Fig. 5 is rapid data distribution algorithms flow chart;

Fig. 6 is that path buffer memory takies situation schematic diagram;

Fig. 7 is group transfer management algorithm flow chart.

Embodiment

For making technological means of the present invention, creation characteristic, reach object and effect is convenient to understand, the present invention will be described in detail below in conjunction with the accompanying drawings and the specific embodiments.

1, entire system frame diagram

In order to solve in SCTP CMT, because the diversity in path causes data reordering and packet loss, finally cause the problem of transmission performance decline, the present invention proposes a kind of multidiameter delay transmission plan of coding Network Based.As shown in Figure 1, be entire system framework of the present invention, comprise transmitting terminal, the multipath on receiving terminal and wireless network.

BW & RTT estimation module computation bandwidth BW and two-way time RTT, transport management module is calculated packet loss pe.By bandwidth BW, two-way time, RTT and packet loss pe determine at every turn how many packets (representing with N) are encoded.This group is carried data block DATA chunks and the continuous packet of TSN and is called as group (Group) (in Fig. 1 shown in blue square frame).The packet that carries other pieces (for example controlling) does not divide into groups and encodes, and only sends according to usual mode.

Blended data distribution module by packet grouping and adaptively selecting paths carry out transfer of data.Network encoder selects packet to carry out network code at random, has mixed like this raw data packets (white) and encoded packets (yellow) in the buffer memory of path.For correct fast decoding, these two modules need to be added some redundant data packets.Can increase although redundancy is set the quantity that sends packet, consider that appropriate redundancy can ensure that enough packets arrive receiving terminal, thereby a large amount of minimizing retransmit, and is worth so add redundant data packets.Meanwhile, transport management module receives SACKs to obtain packet accepting state, safeguards congestion control, and judges whether to be necessary to retransmit.Its transfer management is like that taking packet as unit based on group instead of the accurate SCTP of image scale.

At receiving terminal, packet is first kept at and receives in buffer memory, is then submitted to network decoder and carries out decoding, recovers raw data packets.Then, these packets are by assembled and consign to application layer.Finally, receiving terminal is replied SACK.

2, multi-path network coding principle

The principle of multi-path network coding as shown in Figure 2.Raw data packets S1-S4 is divided into a group by transmitting terminal, represents the line linearity assembly coding of going forward side by side with G.No matter be to send raw data packets or encoded packets, they have comprised code coefficient.This make the packet that sends entrained be no longer application layer data, but represented the relation between initial data.Therefore, receiving terminal there is no need strictly to receive according to the order of sequence packet, only needs these packets of buffer memory and extracts the relation (coefficient) between them.In addition, of equal value between each packet, between these information, can exchange, the packet of any loss can be supplemented by other packet.Like this, as long as receiving terminal is collected the packet (4 in theory) of sufficient amount, just can go out raw data packets by Gaussian elimination method correct decoding, also do not need to consider packet or the re-transmission of other loss simultaneously.Generally speaking, by network code, packet is no longer by their unique decision of TSN, and receiving terminal no longer needs rearrangement, and transmitting terminal has also reduced re-transmission in a large number simultaneously.

3, the network code computing based on group

The matter of utmost importance of planned network coding is that each group of needs comprise how many packets, organizes number N.In order to reach lower buffer size but guarantee to carry out sufficient out of order compensation simultaneously, group number needs the suitably quantity higher than out-of-sequence packet.In the time occurring to retransmit, explanation group number has lagged behind the variation of multi-path environment, upgrades N according to time delay, bandwidth and packet loss.

Time delay is the RTT time that BW & RTT estimation module is measured.Because SCTP CMT allows to reply SACK on the path different from corresponding data bag, common SRTT(Smoothed RTT) metering system may be inaccurate.SCTP surveys heartbeat mechanism is provided for path, and it requires HEARTBEAT_ACK to reply on the path identical with HEARTBEAT.In the time of needs renewal group number, send two HEARTBEATs, wait for that two HEARTBEAT_ACKs successfully receive, the RTT time that so just can obtain these two HEARTBEATs also selection smaller value wherein as the RRTT(Reference RTT in path).If SRTT and RRTT approach, illustrate that the reverse-path of very possible SACK and the transmit path of packet are identical, or its forward direction and reverse path have identical time delay, now, consider that the estimation of SRTT is based on great amount of samples, its result is more accurate, and we select SRTT as path RTT; Otherwise SRTT and RRTT gap are larger, select RRTT as path RTT.For path i, we determine the RTT in path by following formula:

${\mathrm{RTT}}_i=\left\{\begin{array}{cc}{\mathrm{SRTT}}_i(\mathrm{if}{\mathrm{SRTT}}_i\∈[a*{\mathrm{RRTT}}_i,b*{\mathrm{RRTT}}_i\left]\right)& \\ {\mathrm{RRTT}}_i& \left(\mathrm{otherwise}\right)\end{array}\right.---\left(1\right)$

Wherein a<1 and b>1 are RTT boundary factor.

Bandwidth BW is measured by BW & RTT estimation module equally.The concept of bandwidth is converted into: the value of available bandwidth equals the ratio of data traffic volume and transmitting time.In the time that group number need to upgrade, collect the bandwidth sample of path i according to following formula:

${\mathrm{BWsample}}_i=\frac{{\mathrm{sendsize}}_i}{{\mathrm{Tl}}_i-{\mathrm{Te}}_i}---\left(2\right)$

Wherein sendsize _ito finish to data traffic volume this moment, Tl from last sampling _iand Te _ibe respectively last packet during this period of time and leave path i buffer memory and first packet and enter time of this buffer memory.In order to eliminate fluctuation, bandwidth sample is carried out to smoothing processing, obtain estimated result:

$\begin{array}{c}{\mathrm{BW}}_i=[1-\exp \left(\frac{-({\mathrm{Tl}}_i-{\mathrm{Te}}_i)}{T_0}\right)]*{\mathrm{BWsample}}_i\\ +\exp \left(\frac{-({\mathrm{Tl}}_i-{\mathrm{Te}}_i)}{T_0}\right)*{\mathrm{BWprevious}}_i\end{array}---\left(3\right)$

Wherein T ₀for bandwidth smoothing factor, BWprevious _ifor a upper estimated result.

Packet loss is provided by transport management module, and this will mention in subsequent content.Finally, our number of renewal group according to the following formula:

Wherein pe _jfor the packet loss of path j, MTU is MTU, and the MTU that conventionally supposes all paths is the same.

As shown in Figure 3, the algorithm flow chart upgrading for group number:

1) in the time occurring to retransmit, for every paths, repeating step 1-4.

2) send two HEARTBEATs, wait for HEARTBEAT_ACK, retransmit if overtime, until receive two HEARTBEAT_ACKs.Obtain the RTT time of two HEARTBEATs, select wherein smaller value as RRTT, to determine the RTT in path according to formula (1).

3) extract bandwidth sample according to formula (2), according to formula (3) computation bandwidth, and upgrade BWprevious.

4) obtain packet loss pe from transport management module.

5) according to formula (4) renewal group number N.

After determining group number, blended data distribution module marks has continuous sequence S ₁-S _nn packet give network encoder.In the time that network encoder will generate an encoded packets, from finite field gf (2 ⁸) in randomly draw N parameter a ₁, a ₂..., a _n, form a S ₁-S _nlinear combination encoded packets T.Due to each parameter a _i(1<i<N) can be expressed as a byte, each packet is also made up of a string byte, and generating the calculating of encoded packets actual is addition and multiplication between byte, if S ₁-S _nregard byte vector as:

T＝a ₁S ₁+a ₂S ₂+...+a _NS _N （5）

As shown in Figure 4, for all packets, no matter be raw data packets or encoded packets, we inserted a NC piece that carries coded message before DATA piece, comprising scope and the code coefficient of group.This NC piece can inform how receiving terminal processes these packets.Like this, in this group, the total load space that offers user data will reduce

4, mix rapid data distribution policy

Because network code has been avoided the packet in group and has been reordered, so do not need scheduling mechanism here.What need to do is to distribute maximum data volume to the buffer memory of path and send as quickly as possible data.A kind of simple solution is to fill up as far as possible valid window (effective window).Valid window has determined that a certain moment allows the data volume sending.Valid window on the i of path is defined as:

effwnd _i＝min{cwnd _i,arwnd} （6）

Wherein cwnd _ifor the congestion window of path i, arwnd is the receive window of notifying in up-to-date SACK.I upper maximum spatial accommodation in path is:

space _i＝(effwnd _i-outstanding _i)(1-pe _i) （7）

Wherein outstanding _ifor having sent on the i of path but also do not receive the data volume of confirmation.Finally, give the path with maximum space by allocation of packets.Repeat to find path the distribute data bag with maximum space, until distribute the data of a group.

As shown in Figure 5, the algorithm flow chart of distributing for rapid data:

1) in the time having data to transmit, calculate the maximum spatial accommodation of every active path according to formula (7), and choose the path j(with maximum spatial accommodation and in the time there is multiple maximum spatial accommodation, select the wherein path of bandwidth maximum).

2) if j is null value, wait for that certain path discharges buffer memory, and on this path distributing data.Otherwise, distributing data on the j of path.

Retransmit in order to ensure decodability and to reduce, need to add redundant data packets.After distributing N packet of a group, we have the buffer memory end, path of data allocations to add some redundant data packets at every.The generation of redundancy packet is identical with the generation of encoded packets, has also comprised the information of whole group.Redundant data packets has identical TSN with the packet before it, can in SACK, confirm by repeating TSN territory.

Suppose in a group that comprises N packet, the packet being assigned on the i of path is M _i, the redundancy on the i of path should be set to:

wherein $N=\underset{i}{\mathrm{\&Sigma;}}{M}_i---\left(8\right)$

Because the upper data success of path i acceptance rate is 1 – pe _i, arranging of this redundancy can ensure on this independent pathway i, finally there is M _iindividual packet arrives receiving terminal.Like this, on all paths, altogether can there is N packet to arrive receiving terminal.Fig. 6 has shown the situation that takies in the buffer memory of path.We can see in most of the cases on every paths, only having a redundant data packets, and this is because rapid data distribution algorithms can be distributed more packet on the lower path of packet loss, makes redundancy be stabilized in minimum.

5, group transfer management mechanism

According to above code Design, comprise that the transfer managements such as congestion control, necessary re-transmission and path packet loss record preferably can carry out with the unit of group.These management are all carried out in transport management module.The overtime GTO(Group Time-Out of definitions section) be the retransmission time out RTO(Retransmission Time-Out of this first packet of group).Define two group pointer GC and GP.

GC represents the group of successfully decoding, send the earliest in current not yet receiving end, and this group packet is kept at the wait acknowledge foremost of path buffer memory.GC has identical use with the outstanding packet in standard SCTP in congestion control.That is to say, if SACK has confirmed a new TSN in GC, carry out and start slowly algorithm or congestion avoidance algorithm; If the report of the loss of GC arrives more than three times, carry out fast and retransmit; If arrive GTO, carry out the overtime re-transmission of GC.It is pointed out that because congestion control is with a group instead of taking independent data bag as unit, so the renewal of cwnd is strengthened, packet loss and the overtime tolerance of SACK have also been strengthened greatly simultaneously.So cwnd can arrive enough values by rapid growth, retransmits and is also reduced greatly.

While occurring to retransmit fast, we select to have the maximum path p of outstanding packet that belongs to GC and carry out corresponding judgement.Relatively BW _pand cwnd _p/ RTT _pbetween size judge packet loss reason: if cwnd _p/ RTT _p< BW _p, show that path does not occur congested, judge that packet loss is caused by wireless mistake, does not revise cwnd _p; Otherwise, packet loss is ascribed to congested, reduce cwnd _p:

ssthresh _p＝max(BW _p*RTT _p,cwnd _p/2,4*MTU) （9）

${\mathrm{cwnd}}_p=\left\{\begin{array}{cc}{\mathrm{cwnd}}_p& (\mathrm{if}{\mathrm{cwnd}}_p/{\mathrm{RTT}}_p<{\mathrm{BW}}_i)\\ \min ({\mathrm{cwnd}}_p,{\mathrm{ssthresh}}_p)\left(\mathrm{otherwise}\right)& \end{array}\right.---\left(10\right)$

Wherein ssthresh _pfor path p start slowly threshold value, consider bandwidth, it need to consider many factor BW _p* RTT _p.Retransmit the encoded packets of a GC simultaneously.

While there is overtime re-transmission, equally carry out the adjustment operation of congestion window and threshold value with standard SCTP.Difference between the GC number of data packets that the group number N that the number of retransmission packet is GC simultaneously and current receiving end are confirmed.

The packet of all re-transmissions all carries out network code equally, and have with this group in last packet (S _n) identical No. TSN, this can distinguish by the TSN territory of duplicate acknowledgment in SACK equally.Finally, select BW _q(1-pe _q) maximum path, carry out as early as possible data packet retransmission.

GP before GC, the group of nearest decoding success, its packet discharges from buffer memory, but its accepting state is still retained.GP is used for carrying out the calculating of packet loss (pe).By SACK, GP can be recorded in the packet sum (having comprised redundancy packet and retransmission packet) and the successful packet receiving that on each path, send.In the time that GC completes decoding, the ratio that transport management module is collected GP unacknowledged data bag and total data bag on every paths, as a packet loss sample, utilizes confidential interval to add up the more packet loss of new route.Finally, the packet loss of every paths is fed back to blended data distribution module by transport management module.GC and GP point to respectively next group, repeating algorithm.

As shown in Figure 7, for organizing the algorithm flow chart of transfer management:

1) if receive SACK in a GTO, execution step 2-4, otherwise execution step 5.

2) value of initialization minGroup and maxGroup.

3) for each in SACK new or the TSN x that repeats, proceed as follows: find out group G under x, the group count pick up device count counting of G, the group of G is lost report counter missing_report zero setting, discharges x; Upgrade minGroup and maxGroup; If G is current group of GC, upgrade the congestion window in the path that sends x, if the group Counter Value of while GC is more than or equal to the group number of GC, discharge the packet of all GC, upgrade packet loss, upgrade GC and GP.

4) group G between minGroup and maxGroup for each, proceeds as follows: if do not belong to the confirmation of G in SACK, the group of G is lost report rolling counters forward, if the value of the counter of the group of G report is simultaneously greater than 3, retransmits fast.

5) for each path at overtime TSN place in GC, carry out overtime re-transmission.

Claims (4)

1. a multidiameter delay transmission plan for coding Network Based, its step comprises:

A) the network code computing based on group.Utilize bandwidth and packet loss to determine group number, the packet in a group is carried out to linear combination network code;

B) mix rapid data distribution policy.Selection has the path of maximum spatial accommodation and carries out data allocations, often distributes one group of data, all adds certain redundant data packets at buffer memory end, path;

C) group transfer management mechanism.Carry out transfer management taking group as unit, comprise that congestion control, the re-transmission of necessity and the record of packet loss upgrade.

2. the network code computing based on group as claimed in claim 1, is characterized in that:

A) two-way time, RTT measured: send HEARTBEAT and obtain RRTT, and contrast SRTT, in the time that RRTT and SRTT approach, the value of selection SRTT is as the RTT in path; When RRTT and SRTT gap are when larger, select the RTT of RRTT as path;

B) bandwidth BW is estimated: obtain bandwidth sample by the traffic volume of data in measuring intervals of TIME and the ratio of Measuring Time, then carry out smoothing processing and obtain bandwidth estimation value;

C) group number upgrades: utilize RTT two-way time, bandwidth BW and packet loss pe to determine group number;

D) network code bag generates: according to group number division group, the packet in a group is carried out to linear combination coding, and in packet, insert corresponding encoded information.

3. mix as claimed in claim 1 rapid data distribution policy, it is characterized in that:

A) Path selection: select the path with maximum spatial accommodation to carry out data allocations, wherein maximum spatial accommodation refers to, at a time path allows the data volume that sends and can be successfully received;

B) add redundancy: the packet number and the packet loss that are fitted on certain path according to certain component carry out redundancy calculating, add redundant data packets, the data packet number that ensures can successfully to arrive on this independent pathway receiving terminal is not less than the packet number of its distribution.

4. as claimed in claim 1 group of transfer management mechanism, is characterized in that:

A) congestion control based on group: for the group GC of current sensing, if SACK confirms a new TSN in GC, carry out and start slowly or congestion avoidance algorithm; If the report of the loss of GC arrives more than three times, carry out corresponding quick retransmission algorithm according to packet loss reason; If overtime GTO, carries out the similar overtime retransmission algorithm with standard SCTP;

B) packet loss pe calculates: for the group GP that completes recently transmission, record the packet that GP receives by the sum of transmission packet and success on each path, calculate the packet loss in each path.

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