Summary of the invention
It is an object of the invention to provide a kind of side realizing three layers of on-demand routing of multicast based on PIM-SSM
Method and equipment, to improve the motility that the forward-path of multicast traffic stream is disposed, strengthen turning of multicast traffic stream
The manageability sent out.To this end, the present invention adopts the following technical scheme that
A kind of method realizing three layers of on-demand routing of multicast based on PIM-SSM, including:
Join message when equipment receives multicast, and determine that receiving the interface that this multicast joins message is configured with
Corresponding on-demand routing information, or this multicast join message in when carrying on-demand routing information, it is judged that self
Whether it is the first equipment jumping correspondence in this on-demand routing information link;Wherein, in described on-demand routing information
Each equipment of the corresponding multicast traffic stream process the most on demand that joins message including this multicast being pre-configured with
Unique identification information;
If being judged as YES, then add flow process according to conventional multicast, set up multicast routing table item, and upstream turn
Send out and do not carry the multicast of on-demand routing information and join message;
If being judged as NO, then set up multicast routing table item according to described on-demand routing information, and to described on-demand
The device forwards that in routing information link, upper hop is corresponding is carried the multicast of on-demand routing information and is joined message.
Wherein, the described equipment device forwards that upper hop is corresponding in described on-demand routing information link carry by
The multicast needing routing information joins message, particularly as follows:
Described equipment deletes identification information corresponding with self in described on-demand routing information, and to described on-demand
The device forwards that in routing information link, upper hop is corresponding carries this deletion identification information corresponding with self
The multicast of on-demand routing information joins message.
Wherein, described equipment sets up multicast routing table item according to described on-demand routing information, particularly as follows:
When described equipment determines the equipment that final jump is corresponding in as described on-demand routing information link,
Multicast routing table item is set up according to described on-demand routing information.
Wherein, described equipment sets up multicast routing table item according to described on-demand routing information, particularly as follows:
Self is connected the interface of the equipment that upper hop is corresponding in this on-demand routing information link and makees by described equipment
For the incoming interface of multicast routing table item, receive interface that described multicast joins message as multicast routing table item
Outgoing interface, set up multicast routing table item.
Wherein, described equipment judge self be not in this on-demand routing information link first jump corresponding equipment it
After, the method also includes:
Self it not the equipment that in described on-demand routing information link, final jump is corresponding when described equipment determines
Time, abandon this multicast and join message.
A kind of network equipment, including:
Receiver module, is used for receiving multicast and joins message;
When described equipment, judge module, for determining that the interface that the multicast received joins message is configured with correspondence
On-demand routing information, or this multicast join message in when carrying on-demand routing information, it is judged that whether self
Corresponding equipment is jumped in this on-demand routing information link first;Wherein, in described on-demand routing information link
Each equipment of the corresponding multicast traffic stream process the most on demand that joins message including this multicast being pre-configured with
Unique identification information;
Processing module, for when described judge module is judged as YES, adds flow process according to conventional multicast, builds
Vertical multicast routing table item, and forwarded upstream do not carries the multicast of on-demand routing information and joins message;When described
When judge module is judged as NO, sets up multicast routing table item according to described on-demand routing information, and press to described
The multicast needing the device forwards that in routing information link, upper hop is corresponding to carry on-demand routing information joins message.
Wherein, described processing module specifically for, be accomplished by described on-demand routing information chain
The device forwards that in road, upper hop is corresponding is carried the multicast of on-demand routing information and is joined message:
Delete identification information corresponding with self in described on-demand routing information, and to described on-demand routing information
The device forwards that in link, upper hop is corresponding carries the on-demand path of this deletion identification information corresponding with self
The multicast of information joins message.
Wherein, described processing module specifically for, be accomplished by according to described on-demand routing information
Set up multicast routing table item:
When described equipment determines the equipment that final jump is corresponding in as described on-demand routing information link,
Multicast routing table item is set up according to described on-demand routing information.
Wherein, described processing module specifically for, be accomplished by according to described on-demand routing information
Set up multicast routing table item:
Self is connected in this on-demand routing information link the interface of the equipment that upper hop is corresponding as multicast path
By the incoming interface of list item, receive interface that described multicast joins message and go out to connect as multicast routing table item
Mouthful, set up multicast routing table item.
Wherein, described processing module is additionally operable to, and judges it self is not this on-demand routing information chain when described equipment
In road first jump corresponding equipment after, and determine self be not in described on-demand routing information link last
When jumping corresponding equipment, abandon this multicast and join message.
In the above embodiment of the present invention, join message when receiving multicast, and determine that receiving this multicast adds
The interface of message be configured with correspondence on-demand routing information, or this multicast join message in carry on-demand path
During information, it is judged that whether self is the first equipment jumping correspondence in on-demand routing information link;If being judged as YES,
Then add flow process according to conventional multicast, set up multicast routing table item, and forwarded upstream does not carry on-demand path
The multicast of information joins message;Otherwise, set up multicast routing table item according to this on-demand routing information, and to this
The device forwards that in on-demand routing information link, upper hop is corresponding is carried the multicast of on-demand routing information and is added report
Literary composition, improve multicast traffic stream forward-path dispose motility, enhance multicast traffic stream forward can
Managerial.
Detailed description of the invention
For above-mentioned problems of the prior art, embodiments provide a kind of based on PIM-SSM
The technical scheme realizing three layers of on-demand routing of multicast.In this technical scheme, add report when receiving multicast
Literary composition, and determine that receiving the interface that this multicast joins message is configured with the on-demand routing information of correspondence, maybe this group
Broadcast when carrying on-demand routing information in joining message, it is judged that self be whether in on-demand routing information link
One jumps corresponding equipment;If being judged as YES, then add flow process according to conventional multicast, set up multicast routing table item,
And forwarded upstream do not carries the multicast of on-demand routing information and joins message;Otherwise, believe according to this on-demand path
Breath sets up multicast routing table item, and the device forwards that upper hop is corresponding in this on-demand routing information link is carried
The multicast of on-demand routing information joins message, and improves the motility that the forward-path of multicast traffic stream is disposed,
Enhance the manageability that multicast traffic stream forwards.
Wherein, above-mentioned add flow process according to conventional multicast and set up multicast routing table item, be i.e. according to existing RPF
Mechanism determines multicast Upstream Interface (hereinafter referred to as Upstream Interface), and using this Upstream Interface as Multicast Routing
The incoming interface of list item, meanwhile, goes out to connect as multicast routing table item using receiving interface that multicast joins message
Mouthful, set up multicast routing table item.Correspondingly, forwarded upstream does not carry the multicast addition of on-demand routing information
Message, is the Upstream Interface determined by this, forwards the multicast not carrying on-demand routing information to join message.
Wherein, the application scenarios predominantly client of the technical scheme that the embodiment of the present invention provides knows multicast source
Address, and without being concerned about BSR(Boot Strap Router, BootStrap Router) and RP(Rendezvous
Point, convergent point) information, and there is no multi-access(multiple access) scene in, its typical case should
It is to run PIM-SSM(PIM-Source Specific Multicast, Protocol Independent Multicast-appointment source by scene
Multicast) system (i.e. PIM-SSM scene) of agreement.
For ease of describing, the most all the embodiment of the present invention is provided with PIM-SSM scene for application scenarios
Technical scheme is described.
Below in conjunction with accompanying drawing, the technical scheme in embodiments of the invention is carried out clear, complete description,
Obviously, the embodiments described below are only a part of embodiment of the present invention rather than whole embodiments.
Based on the embodiment in the present invention, those of ordinary skill in the art are institute under not paying creative work premise
The every other embodiment obtained, broadly falls into the scope of embodiments of the invention protection.
As it is shown on figure 3, realize three layers of multicast for a kind of based on PIM-SSM of embodiment of the present invention offer
The schematic flow sheet of the method for on-demand routing, may comprise steps of:
Step 301, reception multicast join message.
Step 302, judge to receive whether the interface that this multicast joins message is configured with the on-demand path of correspondence
Information.If being judged as YES, then go to step 304;Otherwise, step 303 is gone to;
Step 303, judge that this multicast joins message and whether carry on-demand routing information.If being judged as YES,
Then go to step 304;Otherwise, carry out conventional multicast and add flow processing.
Step 304, judge self to be whether that on-demand routing information link first jumps corresponding equipment, if sentencing
It is yes for breaking, then go to step 306;Otherwise, step 305 is gone to;
Step 305, set up multicast routing table item according to on-demand routing information, and to on-demand routing information link
Device forwards corresponding to middle upper hop is carried the multicast of on-demand routing information and is joined message.
Step 306, add flow process according to conventional multicast, set up multicast routing table item, and forwarded upstream is not
The multicast carrying on-demand routing information joins message.
Concrete, in embodiments of the present invention, can be the on-demand path of the interface configuration correspondence of equipment in advance
Information, this on-demand routing information is for indicating the multicast traffic stream forwarded through this interface to pass through the most on demand
The unique identification information (such as the IP address of equipment) of each equipment.Wherein, this equipment can be routing device.
Wherein, for the corresponding interface of each equipment that this on-demand routing information includes, need to enable on-demand road
Footpath function, to ensure that the corresponding interface of this each equipment is capable of identify that on-demand routing information.
As a example by the scene shown in Fig. 2, for connecting the interface of Client_9A on Router_9, can be pre-
First configure the IP address of following on-demand routing information: IP1(Router_1, lower same)
-> IP4-> IP7-> IP8-> IP9, i.e. connects the multicast number that the interface of Client_9A forwards on Router_9
According to the multicast traffic stream of stream (being i.e. sent to Clinet_9A), in data forwarding process, need warp successively
Cross Router_1, Router_4, Router_7, Router_8 and Router_9.
When equipment receives after multicast joins message, can first judge to receive the interface that this multicast joins message
Whether it is configured with the on-demand routing information of correspondence, if do not configure (, think it self is not certain multicast traffic stream pair
The equipment that final jump in the on-demand routing information link answered is corresponding, or, self it not certain multicast traffic stream
The equipment of the arbitrary jumping correspondence in corresponding on-demand routing information link), then can determine whether this multicast
On-demand routing information whether is carried in joining message, if do not carry (, think it self is not certain multicast packet
The equipment that arbitrary jumping in the on-demand routing information link that stream is corresponding is corresponding), then carry out conventional multicast and add and become a mandarin
Journey processes (i.e. carry out multicast according to existing PIM-SSM agreement and add flow processing).
If equipment determines that receiving the interface that this multicast joins message is configured with the on-demand routing information of correspondence,
Or, this multicast carries on-demand routing information in joining message, then this equipment also needs to determine whether self
Whether it is the first equipment jumping correspondence in this on-demand routing information link, and when being judged as NO, press according to this
Routing information is needed to set up multicast routing table item, and the equipment that upper hop is corresponding in this on-demand routing information link
The multicast carrying on-demand routing information is forwarded to join message.If it self is on-demand routing information link that equipment determines
In first jump corresponding equipment, then add flow process according to conventional multicast, set up multicast routing table item, and upwards
Trip forwards the multicast not carrying on-demand routing information to join message.
Still as a example by scene shown in Fig. 2, when Router_9 receives the multicast addition report that Clinet_9A sends
Wen Hou, determines that the interface connecting Clinet_9A on Router_9 is configured with corresponding on-demand routing information
(IP1-> IP4-> IP7-> IP8-> IP9), and determine it self is not the first jumping in this on-demand routing information link
(IP1) corresponding equipment, then Router_9 is setting up multicast routing table item and is forwarding this multicast to add report
Wen Shi, is no longer the incoming interface determining in multicast routing table item according to RFP mechanism, and forwards this multicast to add
Enter the outgoing interface of message, but need to determine corresponding interface, i.e. Router_9 according to this on-demand routing information
Generate to should be to should the multicast of interface of Router_9 upper connection Clinet_9A in multicast routing table item
The incoming interface of data stream is the interface connecting Router_8, and correspondingly, Router_9 adds report at forwarding multicasting
Wen Shi, is joined message multicast by this interface and is transmitted to Router_8.Wherein, Router_9 is transmitted to
The multicast of Router_8 carries corresponding on-demand routing information in joining message.
Router_8 receive Router_9 forward multicast join message after, in determining that this multicast joins message
Carry on-demand routing information, and determine it self is not the first corresponding setting of jumping in this on-demand routing information link
Standby (in this on-demand routing information link, the first equipment jumping correspondence is Router_1), then according to this on-demand road
Footpath information sets up multicast routing table item, and the equipment that upper hop is corresponding in this on-demand routing information link
(Router_7) multicast carrying on-demand routing information is forwarded to join message.
It should be noted that in embodiments of the present invention, when equipment determines that receive that multicast joins message connects
Mouth is configured with the on-demand routing information of correspondence, or, determine that the multicast received carries in joining message on-demand
During routing information, the equipment device forwards multicast that upper hop is corresponding in on-demand routing information link joins message
Time, the on-demand routing information that this multicast carries in joining message can be after deleting self identification information by
Need routing information.
Such as, the corresponding on-demand routing information of the interface configuration of Router_9 upper connection Client_9A is
IP1-> IP4-> IP7-> IP8-> IP9, and Router_9 is transmitted to carry during the multicast of Router_8 joins message
On-demand routing information can be IP1-> IP4-> IP7-> IP8(i.e. Router_9 delete self mark letter
Breath), correspondingly, Router_8 is transmitted to during the multicast of Router_7 joins message the on-demand path letter carried
Breath can be IP1-> IP4-> IP7.
Additionally, in embodiments of the present invention, equipment receives multicast and joins message, and determines that this multicast adds
When message carries on-demand routing information, it is also possible to determine in this on-demand routing information whether include self
Identification information (or, if the equipment device forwards multicast that upper hop is corresponding in on-demand routing information link adds
During message, the on-demand routing information that this multicast carries in joining message be after deleting self identification information by
Need routing information, then equipment is it needs to be determined that whether self is the final jump pair in this on-demand routing information link
The equipment answered), and when determining that this on-demand routing information link includes that the identification information of self (determines self
For the equipment that final jump in on-demand routing information link is corresponding) time, it is believed that oneself it is that this multicast joins message
Corresponding multicast traffic stream needs the equipment of process, and when self not being the first jumping in on-demand routing information link
During corresponding equipment, set up multicast routing table item according to this on-demand routing information, and this multicast is joined message
The device forwards that upper hop is corresponding in this on-demand routing information link.When this on-demand routing information does not includes
Self identification information (or, if the equipment device forwards group that upper hop is corresponding in on-demand routing information link
Broadcasting when joining message, the on-demand routing information that this multicast carries in joining message is the identification information deleting self
After on-demand routing information, determine it self is not corresponding the setting of final jump in this on-demand routing information link
Standby) time, abandon this multicast and join message, and terminate current process.
Wherein, equipment is when setting up multicast routing table item according to on-demand routing information, it is also possible to compare according to by
Need incoming interface (or Upstream Interface) that routing information determines and determined by RPF mechanism incoming interface (or
Upstream Interface) the most identical, and when differing, corresponding labelling can be added in multicast routing table item,
Such as " on-demand ", to show that this multicast routing table item is set up according to on-demand routing information.
Still as a example by scene shown in Fig. 2, it is assumed that the interface multicast of Router_9 upper connection Client_9A
After joining message, according to the incoming interface in the multicast routing table item that RPF mechanism determines, (i.e. this multicast adds report
The outgoing interface that literary composition forwards) be the interface connecting Router_6 on Router_9, then generate on Router_9
Corresponding route table items can include following information:
Router_9:
IP0(multicast packet source IP)
Labelling: on-demand
The interface of incoming interface: Router_9 upper connection Router_8
The interface [IP1-> IP4-> IP7-> IP8] of outgoing interface: Router_9 upper connection Clinet_9A
According to above-mentioned multicast routing table item, when Router_9 connects the interface of Router_8 from Router_9
When receiving the multicast traffic stream that the multicast packet source that IP address is IP0 sends, need this multicast traffic stream
The interface connecting Clinet_9A from Router_9 forwards.
In order to make those skilled in the art be more fully understood that the technical scheme that the embodiment of the present invention provides, below knot
The technical scheme that closing concrete application scenarios provides the embodiment of the present invention is further described in more detail.
As shown in Figure 4, the configuration diagram of a kind of concrete application scenarios provided for the embodiment of the present invention, its
In: Router_A connects multicast packet source 100.1.1.1225.1.1.1, Router_A respectively by interface A0
The interface connected on Router_B corresponding to Router_B(by interface A1 with A2 is B1) and Router_C
(the corresponding interface on Router_C is C2), Router_B connects Router_C(pair by interface B3
The interface on Router_C answered is C3), Router_C connects Client_1 by interface C0 and C1 respectively
And Client_2;The IP address of Router_A, Router_B and Router_C is respectively 1.1.1.1,2.2.2.2
And 3.3.3.3.
In this embodiment, the interface C0 of Router_C upper connection Client_1 does not configures on-demand routing information;
The corresponding on-demand routing information of the interface C1 configuration of Router_C upper connection Client_2 is:
1.1.1.1->2.2.2.2->3.3.3.3;Interface C1, B3 and A1 enable on-demand path function, and assume
Router_C receive multicast data message after by RPF mechanism calculated Upstream Interface be C2.
Based on the application scenarios shown in Fig. 4, when Client_1 wants receiving multicast data source 100.1.1.1
During the multicast traffic stream 225.1.1.1 sent, Client_1 can send request to Router_C and add this multicast
The multicast of the multicast group that data source is corresponding joins message;In like manner, receiving multicast data source is wanted as Client_2
During the multicast traffic stream 100.1.1.1225.1.1.1 sent, Client_2 can also send request to Router_C
The multicast adding multicast group corresponding to this multicast packet source joins message.
When RouterC receives after the multicast that Client_1 sends joins message, add according to conventional multicast and become a mandarin
Journey processes, during the transmission of multicast traffic stream, for Client_1, multicast packet source 100.1.1.1
225.1.1.1 the multicast traffic stream sent, by 1.1.1.1-> path of 3.3.3.3 is sent to Client_1, its
Implement and do not repeat them here.
When Router_C receive Client_2 send multicast join message after, determine corresponding interface (C1)
It is configured with the on-demand routing information of correspondence, i.e. 1.1.1.1-> 2.2.2.2-> 3.3.3.3, and self is not this on-demand road
In the information link of footpath, first jumps the equipment that (1.1.1.1) is corresponding, then build according to the on-demand routing information inquired
Vertical multicast routing table item:
Router_C:
100.1.1.1225.1.1.1
Labelling: on-demand
Upstream Interface: C3
Downstream interface: C1 [1.1.1.1-> 2.2.2.2]
Wherein, according to the information in above-mentioned multicast routing table item, when Router_C receives from interface C3
To multicast packet source 100.1.1.1225.1.1.1 send multicast traffic stream time, need to circulate this multicast packet
Cross interface C1 to forward.
After Router_C has set up multicast routing table item, Router_C by this multicast message according to this on-demand path
Information, the equipment (Router_B) that upper hop (2.2.2.2) is corresponding in this on-demand routing information link turns
Sending out this multicast to join message, wherein, this multicast carries Router_C and deletes self identification letter in joining message
On-demand routing information 1.1.1.1-> 2.2.2.2 after breath (i.e. 3.3.3.3).
Router_B receives after this multicast joins message, and determines that this multicast carries on-demand road in joining message
Footpath information, and determine from corresponding the setting as the final jump (2.2.2.2) in this on-demand routing information link
Standby, and self be not the first equipment jumping that (1.1.1.1) is corresponding, then basis in this on-demand routing information link
This on-demand routing information sets up multicast routing table item:
Router_B:
100.1.1.1225.1.1.1
Upstream Interface (i.e. incoming interface): B1
Downstream interface (i.e. outgoing interface): B3 [1.1.1.1]
Wherein, according to the information in above-mentioned multicast routing table item, when Router_B receives from interface B1
To multicast packet source 100.1.1.1225.1.1.1 send multicast traffic stream time, need to circulate this multicast packet
Cross interface B3 to forward.
After Router_B has set up multicast routing table item, Router_B by this multicast message according to this on-demand path
Information, the equipment (Router_A) that upper hop (1.1.1.1) is corresponding in this on-demand routing information link turns
Sending out this multicast to join message, wherein, this multicast carries Router_B and deletes self identification letter in joining message
On-demand routing information 1.1.1.1 after breath (i.e. 2.2.2.2).
Router_A receives after this multicast joins message, and determines that this multicast carries on-demand road in joining message
Footpath information, and determine from corresponding the setting as the final jump (1.1.1.1) in this on-demand routing information link
Standby, and determine from the equipment jumping (1.1.1.1) correspondence as in this on-demand routing information link first, then root
Add flow process according to conventional multicast, set up multicast routing table item, and forwarded upstream does not carry on-demand routing information
Multicast join message, it is assumed that the Upstream Interface determined by RPF mechanism is A0, then set up following multicast
Route table items:
Router_A:
100.1.1.1225.1.1.1
Upstream Interface (i.e. incoming interface): A0
Downstream interface (i.e. outgoing interface): A1
Wherein, according to the information in above-mentioned multicast routing table item, when Router_A receives from interface A0
To multicast packet source 100.1.1.1225.1.1.1 send multicast traffic stream time, need to circulate this multicast packet
Cross interface A1 to forward.
By with upper type, the multicast traffic stream that multicast packet source 100.1.1.1225.1.1.1 sends, passing through
1.1.1.1-> path of 3.3.3.3 is sent to Client_1, by 1.1.1.1-> path of 2.2.2.2-> 3.3.3.3 sends out
Deliver to Client_2, it is achieved that the different user on same equipment is disposed different multicast forwarding paths, carries
The motility that the forward-path of high multicast traffic stream is disposed, enhances the managing of forwarding of multicast traffic stream
Property.
Inventive concept based on said method embodiment system, the embodiment of the present invention additionally provides a kind of network and sets
Standby, can apply to said method embodiment.
As it is shown in figure 5, the structural representation of a kind of network equipment provided for the embodiment of the present invention, can wrap
Include:
Receiver module 51, is used for receiving multicast and joins message;
Judge module 52, for when described equipment, to determine that the interface that the multicast received joins message is configured with right
The on-demand routing information answered, or this multicast join message in when carrying on-demand routing information, it is judged that self be
The no equipment jumping correspondence in this on-demand routing information link first;Wherein, described on-demand routing information wraps
Include this multicast being pre-configured with to join message each equipment of multicast traffic stream process the most on demand of correspondence
Unique identification information;
Processing module 53, for when described judge module 52 is judged as YES, adds according to conventional multicast and becomes a mandarin
Journey, sets up multicast routing table item, and forwarded upstream is not carried the multicast of on-demand routing information and joined message;
When described judge module 52 is judged as NO, set up multicast routing table item according to described on-demand routing information,
And the device forwards that upper hop is corresponding in described on-demand routing information link carries the group of on-demand routing information
Broadcast and join message.
Wherein, described processing module 53 specifically for, be accomplished by described on-demand path believe
The device forwards that in breath link, upper hop is corresponding is carried the multicast of on-demand routing information and is joined message:
Delete identification information corresponding with self in described on-demand routing information, and to described on-demand routing information
The device forwards that in link, upper hop is corresponding carries the on-demand path of this deletion identification information corresponding with self
The multicast of information joins message.
Wherein, described processing module 53 specifically for, be accomplished by according to described on-demand path
Information sets up multicast routing table item:
When described equipment determines the equipment that final jump is corresponding in as described on-demand routing information link,
Multicast routing table item is set up according to described on-demand routing information.
Wherein, described processing module 53 specifically for, be accomplished by according to described on-demand path
Information sets up multicast routing table item:
Self is connected in this on-demand routing information link the interface of the equipment that upper hop is corresponding as multicast path
By the incoming interface of list item, receive interface that described multicast joins message and go out to connect as multicast routing table item
Mouthful, set up multicast routing table item.
Wherein, described processing module 53 is additionally operable to, and judges it self is not this on-demand path letter when described equipment
In breath link first jump corresponding equipment after, and determine self be not in described on-demand routing information link
During the equipment that rear one jumps correspondence, abandon this multicast and join message.
Wherein it is preferred to, this network equipment can be routing device.
It will be appreciated by those skilled in the art that the module in the device in embodiment can describe according to embodiment
Carry out being distributed in the device of embodiment, it is also possible to carry out respective change and be disposed other than one of the present embodiment
Or in multiple device.The module of above-described embodiment can merge into a module, it is also possible to is further split into
Multiple submodules.
Through the above description of the embodiments, those skilled in the art is it can be understood that arrive the present invention
The mode of required general hardware platform can be added by software to realize, naturally it is also possible to by hardware, but very
In the case of Duo, the former is more preferably embodiment.Based on such understanding, technical scheme is substantially
The part contributed prior art in other words can embody with the form of software product, this computer
Software product is stored in a storage medium, including some instructions with so that a station terminal equipment is (permissible
It is mobile phone, personal computer, server, or the network equipment etc.) perform described in each embodiment of the present invention
Method.
The above is only the preferred embodiment of the present invention, it is noted that common for the art
For technical staff, under the premise without departing from the principles of the invention, it is also possible to make some improvements and modifications,
These improvements and modifications also should regard protection scope of the present invention.