CN1756255A - Method for judging repeat SRP command frame - Google Patents
Method for judging repeat SRP command frame Download PDFInfo
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- CN1756255A CN1756255A CN 200410080364 CN200410080364A CN1756255A CN 1756255 A CN1756255 A CN 1756255A CN 200410080364 CN200410080364 CN 200410080364 CN 200410080364 A CN200410080364 A CN 200410080364A CN 1756255 A CN1756255 A CN 1756255A
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Abstract
The invention discloses a method for judging the retransmitted SPR command frame in the H.324 protocol comprising: arranging a sequence bit table, while each bit of said table is relative to one sequence number; when receiving the SPR command frame, fixing the condition of the bit relative to the sequence number of said SPR command frame; according to the condition of said bit, judging that if said SPR command frame is retransmitted; if not, changing the condition of the bit of said sequence table relative to the sequence number of said SPR command frame. The invention can overcome the problems of lower efficiency and space waste of present technology and confirm the correct deleting of the record of received SPR command sequence number which is over time-effect.
Description
Invention field
The present invention relates to a kind of method of differentiating simple retransmission protocol (SRP) command frame of re-transmission, particularly relate to a kind of method of in agreement H.324, judging the SRP command frame that retransmits.
Background technology
H.324 agreement is a low rate multimedia communication terminal agreement, H.324 terminal according to agreement H.223 with audio frequency, video, data and chain of command signal multiplex together, be sent to the opposite end, and, isolate audio frequency, video, data and chain of command signaling by the opposite end demultiplexing.The chain of command signaling is the content that H.245 defines in the agreement, and requirement must provide reliable link layer to transmit.
In agreement H.324, having defined simple retransmission protocol is SRP, guarantees the H.245 reliable transmission of signaling.Under the SRP agreement, SRP command frame of every transmission, sequence number are that mould adds up with 256.If in the time of appointment, do not receive the SRP response frame, need to retransmit the SRP command frame.The SRP command frame that retransmits must be consistent with the sequence number of former SRP command frame, and sequence number can not add up.Which because the SRP response frame does not have sequence number, can't determine and SRP command frame coupling.Therefore under the SRP agreement, before next SRP command frame was sent out, current SRP command frame must obtain the response of SRP response frame.So just cause the SRP command frame must receive that response frame could transmit H.245 signaling of the next one afterwards, influenced the H.245 efficient of signaling negotiation.The agreement later release has increased a new numbering SRP response frame (NSRP), and it has sequence number.So just can correctly mate the SRP command frame, a plurality of H.245 message of parallel transmission are accelerated H.245 negotiation speed.Present 3G H.324 terminal supports NSRP.
If H.324 stipulated the SRP command frame that receives in the agreement sequence number identical with the command frame of before having received arranged, it will not be passed to H.245 layer, because it is a re-transmission of processed commands.This just requires to judge the SRP command frame of re-transmission, and when using the response of NSRP frame, as shown in Figure 1, a plurality of SRP command frames send simultaneously.In the case, judge simply, efficiently whether the SRP command frame is that the frame that retransmits has extremely important.
A kind of method at present relatively more commonly used is: all sequences of the SRP command frame that receives in nearest a period of time number is kept in the sequence number bit table, and according to the sequence arrangement of time.As shown in Figure 2, when receiving a SRP command frame, from the sequence number bit table of preserving, search and judge whether the sequence number of this command frame is in the sequence number bit table, if in tabulation, it then is the SRP command frame that retransmits, if not in tabulation, then be new SRP command frame, its sequence number is saved in the tabulation.
In this method, estimate treatable SRP order each second frame number according to the disposal ability of terminal, for example be 20, the largest interval that the SRP command frame is retransmitted for example is 5S, it is passable so only needing to preserve 100 sequence numbers receiving recently.If the current SRP command frame sequence number of receiving is all different with 100 of fronts, then representative is new SRP command frame, otherwise is exactly the command frame that retransmits.
The advantage of this method is accurately to judge the SRP command frame of re-transmission, searches the sequence number bit table but all need travel through at every turn, when system's heavy-duty service, has had a strong impact on running efficiency of system.Preserving each sequence number (sequence number range is 0-255) in the calling all needs 1 byte, and preserving 100 sequence numbers just needs 100 bytes.When call number in the system is very big, require very big memory space.
Summary of the invention
In order to solve inefficiency in the above-mentioned art methods and to expend the problem of memory space, the purpose of this invention is to provide simply a kind of and judge the method for the SRP command frame that retransmits efficiently.
To achieve these goals, the method for the SRP command frame that judgement of the present invention retransmits comprises: 1) a sequence number bit table is set, and each position in the described sequence number bit table is corresponding to a described sequence number; 2) when receiving the SRP command frame, determine the state of position corresponding in the described sequence number bit table with the sequence number of described SRP command frame; 3), judge whether described SRP command frame is the SRP command frame of retransmitting according to the state of described corresponding position; 4) when judging that described SRP command frame is not the SRP command frame of retransmitting, change the state of the corresponding position of sequence number in described sequence number bit table of described SRP command frame.
In said method of the present invention, determine the corresponding position of sequence number in described sequence number bit table of the SRP command frame received in the following way: the offset word joint number of sequence number in described bit table of determining the SRP command frame; With definite described sequence number skew figure place with respect to described skew byte in described bit table.Wherein, described offset word joint number is rounded divided by 8 by the sequence number of the described SRP command frame that receives and obtains, and described skew figure place is got remainder by the sequence number of the described SRP command frame that receives divided by 8 and obtained.
In embodiments of the invention, can further comprise with in the described sequence number bit table with the step of the state zero clearing of the corresponding position of the sequence number that early receives.
The present invention adopts 256 bitmap modes to shine upon the SRP command frame sequence number of reception, has replaced search procedure with the method for direct location, and the traversal of having avoided expending system resource is most searched algorithm, has greatly improved running efficiency of system.Only need take 32 bytes just can realize retransmitting the differentiation of SRP command frame in each calling of the present invention, thereby has saved memory space.
In addition, the method according to this invention can guarantee that also the SRP command frame sequence number record of having received can correctly be removed in its timeliness later, thereby has guaranteed the backrush of sequence number.
Description of drawings
Fig. 1 is the schematic diagram when a plurality of SRP command frames transmit simultaneously in the prior art;
Fig. 2 is a tabulation schematic diagram of preserving the sequence number of SRP command frame in the prior art;
Fig. 3 is the serial number bit hoist pennants of the embodiment of the invention;
Fig. 4 is the serial number bit list structure schematic diagram of SRP command frame shown in Figure 3;
Fig. 5 is the sequence number zero clearing schematic diagram of the embodiment of the invention;
Fig. 6 is respectively the sequence number zero clearing schematic diagram of N＜=128 and N＜=64 o'clock.
Embodiment
Followingly embodiments of the invention are described in detail with reference to Fig. 3 to Fig. 6.
In an embodiment of the present invention, set up sequence number bit table as shown in Figure 3.As shown in Figure 4, this tabulation takies 32 bytes, 8 positions of each byte, totally 256 positions.Correspond respectively to 256 sequence numbers of SRP command frame with these 256 positions.For example, represent sequence number 1 (SN1) with position 0, sequence number 2 (SN2) is represented in position 1 ..., sequence number 256 (SN256) is represented in position 255.In this example, establish with 0 expression and do not receive that the SRP command frame of corresponding sequence number, 1 expression received the SRP command frame of corresponding sequence number.When beginning, the value of all is cleared.
When receiving terminal receives a SRP command frame from sending terminal, take out sequence number wherein.In the sequence number bit table, directly find the position corresponding, judge this state with this sequence number.If reading this value is 0 o'clock, expression had not before received the SRP command frame of this sequence number, and this value is changed to 1, and receiving terminal is handled accordingly to this frame then.If this value is 1 o'clock, the SRP command frame that before received this sequence number is described, this SRP command frame is the SRP command frame of retransmitting, receiving terminal does not deal with this command frame.
In this example, the method for concrete location can adopt following computing formula in the sequence number bit table:
nBytes＝SNrecv/8 (1)
nBits＝SNrecv％8 (2)
Wherein, nBytes represents the offset word joint number of sequence number in tabulation of SRP command frame, and SNrecv represents the sequence number of the SRP command frame that receiving terminal receives.The sequence number that nBits represents the SRP command frame that receiving terminal receives in tabulation the position with respect to the skew figure place of corresponding byte.
After using the sequence number of the SRP command frame that receives to round divided by 8, formula (1) expression obtains the offset word joint number of this sequence number position in tabulation.
Formula (2) expression is got the value that remainder obtains nBits with the sequence number that receives divided by 8.
Fig. 4 is the sequence number location schematic diagram of SRP command frame of the present invention.As shown in the figure, the sequence number that receiving terminal receives the SRP command frame is 14, the sequence number that receives the SRP command frame with receiving terminal can directly calculate the offset word joint number of position in this sequence number place tabulation and this sequence number skew figure place with respect to corresponding byte, promptly
nBytes＝14/8＝1
nBits＝14％8＝6
Promptly this sequence number is positioned in the 6th bit place of the 1st byte, if the value of this position is zero, does not receive this SRP command frame before illustrating, if the value of this position is 1, explanation is the SRP command frame that retransmits.
The foregoing description is under the situation of 0-255 for the scope of the sequence number of the SRP command frame in the session, and the position in its sequence number bit table can be corresponding one by one with the sequence number of SRP command frame.But, surpassing 256 for the number of the SRP command frame in the conversation procedure, the sequence number branch timing of will starting from scratch again just can't have been differentiated.
Fig. 5 has shown according to a method of improving embodiment of the present invention.
In the present embodiment, adopted progressively with in the sequence number bit table with early before the method for the corresponding position zero clearing of sequence number that receives.As shown in Figure 5, T1, T2, T3, the time between the T4 is the maximum SRP retransmit interval between receiving terminal and the transmission terminal.So-called retransmit interval just is meant to send a SRP command frame that the opposite end is response not, sends this SRP command frame again, and the time between these two command frames is exactly retransmit interval.Can dispose this blanking time, is exactly maximum SRP retransmit interval when getting the configuration maximum.General blanking time is between a few tens of milliseconds arrives several seconds.When T3 arrives constantly, keep T2 to the corresponding position of sequence number that T3 receives constantly, the bit clear of the sequence number correspondence that T2 is received constantly before.When T4 arrives constantly, keep the position of the sequence number correspondence that T3 receives constantly to T4, the bit clear of the sequence number correspondence that T3 is received constantly before.
Routine processes can be converted to chronomere with the number of SRP command frame and represent for convenience.For this reason, at first estimate the number of the SRP command frames that maximum retransmit was handled at most in blanking time between receiving terminal and transmission terminal.This evaluation method can be generally maximum retransmit is made as S second at interval, and common H245 calling to have M message.Suppose not burst, approximately have M SRP command frame, so generally have N=S*M SRP command frame in blanking time in maximum retransmit.General S was less than 1 second, and M is less than 30.If burst, then the corresponding M value can increase, but the computational methods of N are constant.Suppose in a retransmit interval, to receive at most N SRP command frame,, only need the Status Flag of the position of the sequence number correspondence between the reservation N-2N to get final product, the position zero clearing of other sequence number so when receiving 2N SRP command frame.When receiving 3N SRP command frame, the sequence number that only needs to keep between the 2N-3N gets final product, the Status Flag zero clearing of the position of other sequence number correspondences, and the rest may be inferred.
Certainly, when removing the position of the sequence number correspondence of receiving a long time ago, need not remove 256-N, as long as guarantee that the sequence number that is kept is just passable more than or equal to N.In other words, the sequence number number of removing should be smaller or equal to 256-N.
Present embodiment is when specific implementation, be the processing of simplifying procedures, sequence number bit table (the agreement regulation is totally 256 sequence numbers) segmentation, each segmentation of only removing the sequence number correspondence that receives the earliest, suppose that M represents the number of segmentation, each sequence number number of removing a segmentation is 256/M, therefore as long as guarantee to satisfy following mathematical relationship, promptly
256-256/M＞＝N
N represents in SRP command frame maximum retransmit is at interval the SRP command frame number that multipotency is received, therefore, as long as the sequence number that keeps is just passable more than or equal to N.If N＜=192 then can be divided into four sections (M＞=4) at least, if N＜=128 then can be divided into two sections (M＞=2) at least, the rest may be inferred.For ease of handling, preferably the number of segmentation be 2 index doubly.
Fig. 6 is respectively the sequence number bit table zero clearing schematic diagram of N＜=128 and N＜=64 o'clock.When N＜=128, the sequence number bit table is divided into two sections, when the sequence number of receiving the SRP command frame is 127, with the corresponding position zero clearing of the sequence number between the 128-255, when the sequence number of receiving the SRP command frame is 255, with the corresponding position zero clearing of the sequence number between the 0-127.When N＜=64, sequence table is divided into four sections, when the sequence number of receiving the SRP command frame is 63, with the corresponding position zero clearing of the sequence number between the 64-127, when the sequence number of receiving the SRP command frame is 127, with the corresponding position zero clearing of the sequence number between the 128-191, when the sequence number of receiving the SRP command frame is 191, with the corresponding position zero clearing of the sequence number between the 192-255, when the sequence number of receiving the SRP command frame is 255, with the corresponding position zero clearing of the sequence number between the 0-63.Obviously, the sequence number section of above-mentioned zero clearing can be carried out different settings as required with the zero clearing order, and the mode of being mentioned above being not limited to.
According to the H245 agreement, H245 message has 34 at most, therefore, can not surpass 20 H245 message in the general session, and maximum retransmission generally can not surpass 5 seconds at interval, and the N value is 100 to the maximum, therefore preferably the sequence number bit table is divided into two sections.When the sequence number of receiving the SRP command frame is 127, with the position section zero clearing of the sequence number correspondence between the 128-255; When the sequence number of receiving the SRP command frame is 255, with the position section zero clearing of the sequence number correspondence between the 0-127.
Though below described the present invention in conjunction with specific embodiments, these specify not is limitation of the present invention.Those skilled in the art can make various modifications and conversion to the present invention under the situation that does not break away from the spirit and scope of the present invention.They are all in the protection range of appended claim.
Claims (10)
1. method of judging the simple retransmission protocol SRP command frame of re-transmission comprises:
1) a sequence number bit table is set, each position in the described sequence number bit table is corresponding to a described sequence number;
2) when receiving the SRP command frame, determine the state of position corresponding in the described sequence number bit table with the sequence number of described SRP command frame;
3), judge whether described SRP command frame is the SRP command frame of retransmitting according to the state of described corresponding position; With
4) when judging that described SRP command frame is not the SRP command frame of retransmitting, change the state of the corresponding position of sequence number in described sequence number bit table of described SRP command frame.
2. method according to claim 1 is characterized in that, in the following way the corresponding position of the sequence number of definite SRP command frame that is received in described sequence number bit table:
Determine the offset word joint number of sequence number in described bit table of SRP command frame; With
Determine described sequence number skew figure place with respect to described skew byte in described bit table.
3. method according to claim 2, it is characterized in that described offset word joint number is partly obtained divided by 8 back round numbers by the sequence number of the described SRP command frame that receives, described skew figure place is obtained divided by getting remainder after 8 by the sequence number of the described SRP command frame that receives.
4. according to claim 1,2 or 3 described methods, it is characterized in that further comprising: will with the corresponding position zero clearing of the sequence number that formerly receives.
5. method according to claim 4 is characterized in that, the number of the corresponding position of the sequence number of removing is smaller or equal to 256-N, and wherein N is the number of the SRP command frame received at most in a SRP retransmit interval.
6. method according to claim 5 is characterized in that described sequence number is changed to zero step to be comprised:
The number N of the SRP command frame of determining the maximum SRP retransmit interval between transmitting terminal and the receiving terminal and in this interval, receiving at most; With
When receiving terminal receives that SRP command frame number is the integral multiple of N, in the sequence number bit table, keep the position of N nearest sequence number correspondence, with the corresponding position zero clearing of all the other sequence numbers.
7. method according to claim 6 is characterized in that, determines the number N of the SRP command frame received at most in maximum SRP retransmit interval in the following manner:
If described maximum SRP retransmit interval is made as S second, each H245 calls out M message, then
N＝S*M。
8. method according to claim 4 is characterized in that, described will comprising with the step of the corresponding position zero clearing of the sequence number that formerly receives:
Determine the maximum SRP retransmit interval of transmitting terminal and receiving terminal; With
In described sequence number bit table, keep apart from current time be maximum SRP retransmit interval during in the corresponding position of sequence number, with the corresponding zero clearing of other sequence number.
9. method according to claim 4 is characterized in that described sequence number is changed to zero step to be comprised:
Described serial number bit table segmenting;
Determine the maximum SRP retransmit interval between transmitting terminal and the receiving terminal; With
Remove the tract that receives the earliest in the sequence number bit table, the number of sequence number that makes reservation is more than or equal to maximum numbers of the SRP command frame of receiving in the described retransmit interval.
10. method according to claim 9 is characterized in that the segmentation of described sequence number bit table will be satisfied following relationship:
256-256/M＞＝N
Wherein, N represents in SRP command frame maximum retransmit at interval the SRP command frame number that multipotency is received.
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| Application Number | Priority Date | Filing Date | Title |
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| CNB2004100803641A CN100502393C (en) | 2004-09-29 | 2004-09-29 | Method for judging repeat SRP command frame |
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| CNB2004100803641A CN100502393C (en) | 2004-09-29 | 2004-09-29 | Method for judging repeat SRP command frame |
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| CN1756255A true CN1756255A (en) | 2006-04-05 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101197959B (en) * | 2007-12-29 | 2010-12-08 | 北京创毅视讯科技有限公司 | Terminal control method, system and equipment |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| DE3069762D1 (en) * | 1980-08-26 | 1985-01-17 | Ibm | System for the retransmission of incorrectly received numbered frames in a data transmission system |
| CA1220830A (en) * | 1984-12-28 | 1987-04-21 | David S. Drynan | Transmitting sequence numbers of information in a packet data transmission system |
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Cited By (1)
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| CN101197959B (en) * | 2007-12-29 | 2010-12-08 | 北京创毅视讯科技有限公司 | Terminal control method, system and equipment |
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Granted publication date: 20090617 Termination date: 20120929 |