CN100426781C - Method for realizing quick retrieval positioning through virtual access connection - Google Patents
Method for realizing quick retrieval positioning through virtual access connection Download PDFInfo
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- CN100426781C CN100426781C CNB2003101213134A CN200310121313A CN100426781C CN 100426781 C CN100426781 C CN 100426781C CN B2003101213134 A CNB2003101213134 A CN B2003101213134A CN 200310121313 A CN200310121313 A CN 200310121313A CN 100426781 C CN100426781 C CN 100426781C
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Abstract
The present invention provides a method for realizing quick retrieval positioning through virtual channel connection (VCC). Based on the variable digits of the bit values of a virtual path identifier (VPI) and a virtual channel identifier (VCI), the method sets up the masks and the reference values of VPI and VCI in advance. The method also comprises the following steps: A. VPI and VCI are picked up from received ATM cells or ATM primitives; B. VPI and VCI picked up from step A. are compared with masks set up in advance so as to obtain the invariable bit values of the current VPI and VCI; if the invariable bit values of VPI and VCI are identical to respectively reference values, executing step C, otherwise, exiting the flow; C. according to the masks, the variable digits of the bit values of VPI and VCI are orderly picked up, and a virtual channel connection identifier (VCCI) is combined; D. search is carried out in a VCC table according to VCCI so as to position the corresponding VCC. The present invention has the advantages of rapid positioning without the limited value range of VPI and VCI. Therefore, the value ranges of VPI and VCI can be configured flexibly.
Description
Technical field
The present invention relates to ATM exchange field, be meant that especially a kind of virtual path of realizing connects (VCC) method of retrieval location fast.
Background technology
The letter head of ATM cell comprises VPI (VPI) and VCI (VCI), and Fig. 1 is the ATM cell structure chart, and wherein VCI is 16 bits; VPI is 12 bits in Network-Node Interface (NNI), and VPI is 8 bits in User Network Interface (UNI).When cell need transmit, ATM switch is combined into the VCC index (VCCI of 28 or 24 bits according to VPI in ATM cell or the ATM primitive and VCI, VCC Index), retrieve in the VCC of switch table according to VCCI then, search exchange set on the switch of this VCCI correspondence and processing policy, to set up the VCC connection or to carry out transfer of data, finish follow-up operation.
Below be that example describes with NNI.In setting up the VCC connection procedure, switch at first is combined into the VCI of the VPI of 12 bits and 16 bits the VCCI of 28 bits, and combined method is: VCCI=VPI * 2
16+ VCI, promptly VPI is as the higher bit position, and VCI is as low bit; Directly in the VCC of ATM switch table, search according to the VCCI that calculates then, orient this VCC, set up follow-up connection.Because when retrieving in the VCC table, grow the character string matched and searched to 28 bit VCCI, operand is very huge, has increased machine utilization, influenced VCC retrieval locating speed.On the other hand, also may cause the VCC table excessive, comprise 2
28Individual list item.
At present, accelerate that VCC searches and the method for locating has two kinds: a kind of is that external hardware content addressed storage device on ATM switch (CAM, Content Addressed Memory) is realized.CAM can carry out quick indexing and location according to content, and switch as suction parameter, directly carries out VPI and VCI according to the searching of content in CAM, rather than only according to index search.But the price of CAM is generally relatively more expensive, and product cost is increased greatly.
The method that another kind of quickening VCC searches and locatees, be according to the actual amount of capacity of VCC table on the switch, the corresponding span that limits VPI and VCI, promptly limit its bit figure place, accordingly, all adopt less bit in the time of just can and constructing VCCI when the index of design VCC table, and do not need 28, reduce operand in the retrieving with this, improve the retrieval locating speed.For example, certain ATM switch logic is supported the VCC table of 8K, and this switch has 4 ports, then can dispose 2K at most on each port, promptly 2
11Bar VCC.Therefore, the total bit figure place that is limited VPI and VCI by port capacity is 11,11 VCCI=VPI * 2
N+ VCI, wherein N is the shared figure place of VCI in 11 bits.Be combined into 11 VCCI like this, and do not adopt 28, also can satisfy the logic requirement of this ATM switch VCC table.Owing to define VPI and the total bit figure place of VCI, therefore, can use 11 the VCCI that is combined in the VCC table, to retrieve, can reduce operand, realize the quick indexing of VCC.
But because limited total bit figure place of VPI and VCI, so the span of VPI and VCI is limited, and for example goes up example, if 4 of VPI employings, then the span of VPI is defined as 0～15 (2
4); VCI adopts 7, and the span of VCI is defined as 0～127 (2
7).Because the span of VPI and VCI has to be limited, therefore can not flexible configuration become the span value in addition that protocol requirement is interior, limit, in some occasion, possibly can't satisfy the needs of configuration.
Summary of the invention
In view of this, main purpose of the present invention is to provide a kind of virtual path of realizing to connect (VCC) method of retrieval location fast, is not limiting VPI and VCI span in the location fast, can be with the span flexible configuration in protocol requirement.
Realize the present invention,, determine the number of bits of VCC table index at first according to the size of the configurable VCC table of current atm switch interface; Determine VPI VPI and the variable bit of VCI VCI value, the variable bit figure place of described value is identical with the number of bits of described VCC table index, and the variable bit bit position of described value is discontinuous; Set in advance the mask corresponding and the reference value of corresponding described mask with VPI and the whole bits of VCI, and corresponding VPI of significance bit in the described reference value and the immutable bit among the VCI be set, specify the value that immutable bit is formed among VPI and the VCI by reference value, be used to be provided with the span of VPI and VCI, this method is further comprising the steps of::
A, from the ATM cell that receives or ATM primitive, extract VPI and VCI;
B, VPI, VCI that steps A is extracted and the mask that sets in advance compare, and obtain current VPI and the VCI value of immutable bit separately, if the value of VPI, the immutable bit of VCI is with reference value is identical separately, and execution in step C then, otherwise withdraw from this flow process;
C, extract successively, be combined into virtual path and connect index VCCI according to the value of mask with VPI and VCI variable bit position;
D, in VCC table, retrieve, orient corresponding VCC according to VCCI.
Wherein, the mask of described VPI of setting in advance and VCI further comprises: as low bit, the VPI mask is combined into the mask of corresponding VPI and VCI combination as the higher bit hyte with the VCI mask.Wherein, the bit place value that the corresponding mask of the variable bit of value among VPI and the VCI is set is 1, and other bit place values of mask are 0.
Wherein, the method for the reference value of described VPI that sets in advance corresponding mask and VCI further comprises: be provided with that other bit place values except that described significance bit are 0 in the reference value.Wherein, the bit place value that the mask bit place value is set is 0 corresponding reference value is an effective value, and other bit place values of reference value are 0.
Wherein, step B is described compares the method that obtains current VPI and the immutable separately bit place value of VCI with VPI, VCI with the mask that sets in advance and is: the anti-value of VPI and VCI and mask is carried out mutually and computing, obtain the value of VPI and the immutable bit of VCI.
Wherein, described mask and VPI, VCI are compared of step B obtains the method that current VPI and VCI separately can constant bit place value and is: mask and VPI, VCI are separately converted to character string, adopting character string method relatively, is that the bit place value of VPI, the VCI of 0 correspondence extracts with the mask bit place value.
Wherein, the described method that the value of VPI and VCI variable bit position is extracted successively of step C is: VPI is carried out mutually and computing with mask with VCI, obtain the value of VPI and VCI variable bit position.
Wherein, the described method that the value of VPI and VCI variable bit position is extracted successively of step C is: mask and VPI, VCI are separately converted to character string, adopting character string method relatively, is that the bit place value of VPI, the VCI of 1 correspondence extracts with the mask bit place value.
By said method as can be seen, the invention provides the method for a kind of VCC of realization quick indexing location, by the present invention, VPI and VCI can be combined into short VCCI, make the retrieval operand less, have guaranteed VPI and VCI configuration flexibility by mask and reference value simultaneously, by revising VCC mask and reference value, VPI and VCI can get any value that agreement allows as required, and its span is not restricted.On the other hand, the present invention does not need the CAM that adopts price relatively costly, can not increase the cost of product.
Description of drawings
Fig. 1 is the ATM cell structural representation.
Fig. 2 realizes the flow chart of VCC location for the present invention.
Fig. 3 is for using the schematic diagram of mask, reference value structure VCCI.
Embodiment
With described in the background technology second kind accelerate VCC search with Positioning Principle identical because the actual capacity of VCC table is far smaller than 2 on the switch
28Size, when configuration VCC table, index can adopt less bit.The present invention can be provided with arbitrarily for the value that guarantees VPI and VCI, and VPI and VCI still adopt original whole bit figure place.But because VPI and VCI reality do not need whole bit figure places just enough to use, therefore by being set, mask masks VPI and the unnecessary in actual use bit of VCI here, it is the immutable bit of value, only extract the variable bit of value, by the variable bit of these values, be combined into the VCCI of less bit; Reference value is set simultaneously is used as the benchmark comparison value, the value of VPI and VCI can be arranged in any range.Below be that example describes with the ATM cell of NNI interface.
The VPI of NNI interface and VCI comprise 28 bits altogether.If the size of the configurable VCC table of current atm switch interface is 2
P(P＜28) then adopt P bit to be configured as the index of VCC table.The value of P bit is variable in 28 bits of corresponding setting VPI and VCI, and the value of (28-P) individual bit is for fixing immutable in addition, and the value number of combinations of VPI and VCI is 2 like this
PIndividual, satisfy the logic requirement of this VCC table.
The mask of VPI and VCI can be configured respectively, and the mask of a corresponding VPI and VCI combination also can be set.For the purpose of convenient, below the mask of corresponding VPI and VCI combination is called the VCC mask and is that example is described further with it; Accordingly, the reference value of corresponding VPI and VCI combination is called the VCC reference value here.When carrying out being provided with of VCC mask and VCC reference value, VCC mask and VCC reference value are 28 bits, the corresponding position of wherein low 16 bits (0～15) expression VCI, and 16～27 bits are represented the corresponding position of VPI.Wherein, the VCC mask is 1 bit, and the bit place value of expression VPI or VCI correspondence is variable, is that 0 bit represents that corresponding bit place value is immutable.The VCC mask is that the bit of VCC reference value of 1 bit correspondence is inoperative, and being set is 0, other bits of VCC reference value, value arbitrarily.Like this, for last example, the VCC table size is 2
PThe time, then the VCC mask has P bit to be changed to 1, specifies VPI and a VCI P wherein variable bit position, (28-P) individual immutable bit by the VCC mask; Simultaneously, the value of specifying immutable (28-P) individual bit to form by the VCC reference value.Change an angle, the VCC reference value is equivalent to a plot, and the value of a variable P bit is equivalent to skew.When switch need be set up VCC, switch took out the value of this variable P bit from the VPI of cell or primitive and VCI, was combined into the VCCI of P bit, search in the VCC table according to VCCI then, just can find the index of unique correspondence, finish follow-up operation, set up VCC and connect.
In this scheme, because 28 bits of VPI and VCI all are available,, can change the pairing span of VPI and VCI by configuration VCC reference value and VCC mask, make VPI, VCI can be configured to the interior arbitrary value of protocol requirement.
Fig. 2 is a flow chart of realizing the VCC location for the present invention, with the 2K described in the background technology (2
11) the VCC table of size is example, with reference to accompanying drawing 2, the present invention is described in more detail.
Step 201: according to the capacity of VCC table, promptly the shared bit figure place of VCC table determines that the total value of VPI and VCI is variable bit figure place, and promptly VCC mask bit position is 1 figure place.As in this example, the VCC table size is 2
11Then the total value of VPI and VCI is that variable bit figure place is 11, so the VCC mask has 11 bits to be changed to 1, the VCC mask value concrete who be changed to 1 and the VCC reference value size that will be provided with, all according to actual needs, be configured according to mentioned above.In this example, as shown in Figure 3, the VCC mask of setting is 0,000 0001011100000000 01111111B, and the VCC reference value is 0,001 0000000000000011 00000000B, and the B here represents it is binary value.
Step 202: when cell need transmit, ATM switch received ATM cell or ATM primitive, extracted VPI and VCI from cell or ATM primitive.
Step 203: check that VPI and VCI are whether in the scope of VCC reference value regulation.
At first be combined into initial VCCI, according to initial VCCI=VPI * 2
16+ VCI, promptly VPI is the higher bit position, VCI is low bit, VPI and VCI is combined into the initial VCCI of 28 bits;
Then to the negate of VCC mask, obtain that the VCC mask is counter to be worth, with initial VCCI and the anti-value of VCC mask carry out with, obtain the initial VCCI immutable bit of value separately;
Then will be separately the immutable bit of value compare with separately reference value respectively, the immutable bit of value is identical with reference value, then illustrate be VPI and VCI all within the limits prescribed, execution in step 204, otherwise withdraw from this flow process.
As shown in Figure 3, the VCC mask is that 0,000 00,010,111 00000000 01111111B, VCC reference value are 0,001 00,000,000 00000011 00000000B; Current initial VCCI is 000,100,010,101 00000011 01000111B, according to the above, with initial VCCI promptly 000,100,010,101 00000011 01000111B and VCC mask anti-value carry out with, the result is identical with the VCC reference value, illustrate that current VPI and VCI all in the VCC of logical definition table scope, then carry out next step.
Step 204: VPI, the VCI and the VCC mask that obtain according to step 202 are combined into the VCC index.
With initial VCCI and VCC mask with, obtain the bit that the VCC mask is 1 pairing initial VCCI, then these bits are extracted successively and write among the VCCI, be combined into VCCI.
As shown in Figure 3, be that the corresponding VCC mask of 0,001 00010101 0000001101000111B is that 1 bit extracts successively with the current initial VCCI that is combined into, write successively among the VCCI, the VCCI that is combined into 11 is 110 11000111B.
Step 205: retrieve in VCC table according to 11 VCCI, search this VCC index, set up corresponding passage and connect, finish follow-up operation, wherein said to finish follow-up operation the same with prior art, in full reportedly fails.
Above-mentioned steps 203 described initial VCCI methods of the immutable bit of value separately that obtain wherein, also can be that the VCC mask is separately converted to character string with initial VCCI, adopting character string method relatively, is that the bit place value of the initial VCCI of 0 correspondence extracts with VCC mask bit place value.
From as can be seen above, the present invention is combined into 11 bit VCCI and mates retrieval in the VCC table, alleviated the operand of equipment, when simultaneously VPI and VCI being configured, do not limit span, can dispose VPI any value in 12 bits of agreement regulation as required, and VCI any value in 16 bits of agreement regulation.
More than describe with the ATM cell of NNI interface, for uni interface, except the figure place difference of VPI, its principle no longer describes in detail with top described identical.
The above only is preferred embodiment of the present invention, and is in order to restriction the present invention, within the spirit and principles in the present invention not all, any modification of being done, is equal to replacement, improvement etc., all should be included within protection scope of the present invention.
Claims (9)
1. realize that virtual path connects the method that VCC retrieves the location fast for one kind, it is characterized in that,, determine the number of bits of VCC table index according to the size of the configurable VCC table of current atm switch interface; Determine VPI VPI and the variable bit of VCI VCI value, the variable bit figure place of described value is identical with the number of bits of described VCC table index, and the variable bit bit position of described value is discontinuous; Set in advance the mask corresponding and the reference value of corresponding described mask with VPI and the whole bits of VCI, and corresponding VPI of significance bit in the described reference value and the immutable bit among the VCI be set, specify the value that immutable bit is formed among VPI and the VCI by reference value, be used to be provided with the span of VPI and VCI, this method is further comprising the steps of:
A, from the ATM cell that receives or ATM primitive, extract VPI and VCI;
B, VPI, VCI that steps A is extracted and the mask that sets in advance compare, and obtain current VPI and the VCI value of immutable bit separately, if the value of VPI, the immutable bit of VCI is with reference value is identical separately, and execution in step C then, otherwise withdraw from this flow process;
C, extract successively, be combined into virtual path and connect index VCCI according to the value of mask with VPI and VCI variable bit position;
D, in VCC table, retrieve, orient corresponding VCC according to VCCI.
2. method according to claim 1 is characterized in that, the mask of described VPI of setting in advance and VCI further comprises: as low bit, the VPI mask is combined into the mask of corresponding VPI and VCI combination as the higher bit hyte with the VCI mask.
3. method according to claim 1 and 2, it is characterized in that, the method of the mask of described VPI of setting in advance and VCI further comprises: the bit place value that the corresponding mask of the variable bit of value among VPI and the VCI is set is 1, and other bit place values of mask are 0.
4. method according to claim 1 is characterized in that, the method for the reference value of described VPI that sets in advance corresponding mask and VCI further comprises: be provided with that other bit place values except that described significance bit are 0 in the reference value.
5. method according to claim 3 is characterized in that, the reference value of described VPI of setting in advance and VCI further comprises: the bit place value that the mask bit place value is set is 0 corresponding reference value is an effective value, and other bit place values of reference value are 0.
6. method according to claim 3, it is characterized in that, step B is described to be compared the method that obtains current VPI and the immutable separately bit place value of VCI with VPI, VCI with the mask that sets in advance and is: the anti-value of VPI and VCI and mask is carried out mutually and computing, obtain the value of VPI and the immutable bit of VCI.
7. method according to claim 3, it is characterized in that, described mask and VPI, VCI are compared of step B obtains the method that current VPI and VCI separately can constant bit place value and is: mask and VPI, VCI are separately converted to character string, adopting character string method relatively, is that the bit place value of VPI, the VCI of 0 correspondence extracts with the mask bit place value.
8. method according to claim 3 is characterized in that, the described method that the value of VPI and VCI variable bit position is extracted successively of step C is: VPI is carried out mutually and computing with mask with VCI, obtain the value of VPI and VCI variable bit position.
9. method according to claim 3, it is characterized in that, the described method that the value of VPI and VCI variable bit position is extracted successively of step C is: mask and VPI, VCI are separately converted to character string, adopting character string method relatively, is that the bit place value of VPI, the VCI of 1 correspondence extracts with the mask bit place value.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| WO2009034689A1 (en) * | 2007-09-14 | 2009-03-19 | S.Grants Co., Ltd. | Bit string search device, search method, and program |
| CN101471842B (en) * | 2007-12-29 | 2012-02-29 | 北京大唐高鸿数据网络技术有限公司 | Method for dynamically managing virtual connection of asynchronous transmission mode |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1272296A (en) * | 1997-07-11 | 2000-11-01 | 艾利森电话股份有限公司 | VP/VC lookup technique |
| US6411626B1 (en) * | 1997-05-21 | 2002-06-25 | Nec Corporation | Connection number translating device and its method for translating connection number obtained from input ATM cell to system-inside number |
| US6522652B1 (en) * | 1998-08-31 | 2003-02-18 | Nec Corporation | ATM exchange |
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- 2003-12-11 CN CNB2003101213134A patent/CN100426781C/en not_active Expired - Fee Related
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6411626B1 (en) * | 1997-05-21 | 2002-06-25 | Nec Corporation | Connection number translating device and its method for translating connection number obtained from input ATM cell to system-inside number |
| CN1272296A (en) * | 1997-07-11 | 2000-11-01 | 艾利森电话股份有限公司 | VP/VC lookup technique |
| US6522652B1 (en) * | 1998-08-31 | 2003-02-18 | Nec Corporation | ATM exchange |
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