CN100442758C

CN100442758C - Multicast transfer route setting method, and multicast label switching method for implementing former method

Info

Publication number: CN100442758C
Application number: CNB200480000740XA
Authority: CN
Inventors: 安川正祥; 杉园幸司; 宇贺雅则
Original assignee: Nippon Telegraph and Telephone Corp
Current assignee: Nippon Telegraph and Telephone Corp
Priority date: 2003-02-07
Filing date: 2004-02-06
Publication date: 2008-12-10
Anticipated expiration: 2024-02-06
Also published as: CN101262434A; CN101262434B; CN1701571A

Abstract

A multicast transfer route setting method wherein the shortest route in terms of delay time out of the routes from a starting point to end points is determined by calculation, the delays from a give node on the shortest route to the end points and the maximum delay are calculated, the maximum cost route is excluded from the shortest route according to a selection criterion effective in reducing the cost of the overall tree if the maximum delay meets the delay condition, the multicast transfer route is divided into two route trees, another route determined by calculation is set as a supplement route for the excluded route to interconnect the tow route trees. When a multicast label switching route is set, a shared multicast label switching route is set through a first layer label of the hierarchical labels and partial multicast label switching routes addressed to a sub-group in a lower layer. A relay node judges hierarchical labels to carry out label switching of all the hierarchical labels.

Description

The multicast label switching method of multicast transfer path establishing method and this method of realization

Technical field

The present invention relates to multicast transfer path establishing method, multicast transfer path calculation element, multicast transfer path calculation procedure and the storage medium of having stored multicast transfer path calculation procedure, be specifically related in the multicast network that constitutes by a plurality of nodes that are provided with the multicast conveyer separately, use multicast transfer path calculation element that the multicast transfer path that given starting point and a plurality of terminal points are connected is separately calculated, the multicast transfer path establishing method that uses multicast transfer path setting device that the multicast transfer path that is calculated is set, multicast transfer path calculation element, multicast transfer path calculation procedure and the storage medium of having stored multicast transfer path calculation procedure.

And, the present invention relates to the multicast label switching method, be specifically related in multicast communication network, make that the issue of multicast efficiently (transmission) from the multicast source node to multicast leaf node group in the above-mentioned cast communication path setting technology becomes possible multicast label switching method.

And, the present invention relates to the multicast label switching method that a multicast label switching method is applied to VPN (Virtual Private Network) service, be specifically related to using MPLS (multiprotocol label switching: in VPN MultiProtocol Label Switching), between PE (provider edge) router, the condition of the VPN website of accommodating according to each pe router is set the multicast label switched communication method of best multicast label switching path efficiently in provider's network.

Background technology

On computer network, the cast communication that dynamic image and sound is distributed to specific a plurality of users receives much concern.In this communication mode, in the part that the starting point in path and path in the path that selected terminal point more than or equal to 1 is connected are branched, Copy Info, and information is published to each terminal point.Under the situation of using specific a plurality of terminal points and 1 pair 1 unicast communication that communicates of starting point to release news, starting point must be according to the number ready message of terminal point.Therefore, by using cast communication, the amount of information in the network reduces.In cast communication, use the management unit that is called as multicast group that specific a plurality of terminal points are managed, set 1 transfer path at multicast group.This transfer path is configured to make starting point to be connected with all terminal points that belong to multicast group.And, want to obtain the user of the information that is transmitted to certain multicast group, obtain information by participating in multicast group.Therefore, transfer path changes according to user's participation situation.

As the application of using cast communication, can list the dynamic image issue of video conference, game on line, film and TV etc.Wherein, for video conference, data transfer delay is important performance item.As everybody knows, for the session of carrying out usually, if sound arrives the other side's delay before smaller or equal to 100ms, the session of the sense of can not lacking of proper care.Therefore, when using these application that service is provided,, realize that the delay smaller or equal to certain steady state value is important for the service of Customer Satisfaction is provided.As this service method is provided, exist a kind of method to be, when the data transfer path of selecting from origin-to-destination, select to satisfy the path of using desired delay condition.

And, alleviate viewpoint with the path usage charges of path user payment from the operation of network manager, in the path computing in cast communication, require to reduce the whole cost in path.Therefore, when the service that realizes video conference etc., need a kind of algorithm, the purpose of this algorithm is when satisfying the delay condition, reduces the whole cost in path.This routing algorithm is called delay restriction multicast algorithm (Delay constrained multicast algorithm).In recent years, in order to provide this to postponing strict application, the implementation method that postpones the restriction multicast algorithm receive publicity (for example, with reference to following document 1 and document 2).

In the mode of current proposition, have a kind of by calculating the little path of the cost that satisfies the delay condition from cutting down the more outstanding mode of viewpoint of the whole cost in path.This mode is carried out following steps.

1. calculate the shortest path of connection source and each terminal point.

2. select and delete between 2 of the same race in the connection source that in the path of being calculated, exists, terminal point, the path branches point or between 2 not of the same race, do not comprise in the path of starting point, terminal point, path branches point the path of cost maximum between 2 as the path intermediate point.

3. Shan Chu result generates and has made 2 path tree T1 and the T2 of cutting apart.Herein, T1 is the part path tree that comprises starting point, and T2 is a part path tree in addition.

4. with the arbitrfary point that belongs to 2 path trees as end points, calculate as the additional path in deletion path in the path of the condition that the deferred gratification that takes place between starting point and terminal point is proposed in advance, and the path of cost minimum wherein is appended to path tree.

5. follow, the retrieval cost is the path that 2. next big item is described.

6. repeat 2.～5. step up to the additional path of having retrieved all paths.

Adopt this technology in realizing by service, can calculate (for example, reference literature 2) smaller or equal to the transfer path of the propagation delay of certain higher limit realizing in video conference etc.

This background technology is described in following document.

(document 1)

V.Kompella etc., " Multicast routing for multimediacommunication, " IEEE/ACM Transactions on Networking, Volume:1Issue:3, pp.286-292, June 1993

(document 2)

Q.Zhu, etc., " A source-based algorithm for delay-constrainedminimum-cost multicasting, " proc in IEEE INFOCOM ' 95, vol.1, pp.377-385,1995

Yet, come in the technology of the whole cost cutting of realizing route the problem below existing in the little path of cost of satisfying above-mentioned delay condition by calculating.It is reported, in this technology, calculate required chronic.

And this technology is that calculating is carried out in identical supposition according to the delay of the uplink and downlink of link.Usually, the delay that takes place of the link in network is according to direction and difference.For being expanded, conventional art, needs following action so that can tackle this situation.

(1) replenishes the path when appending, carrying out recomputating of path from the terminal point (being present in the partial tree T2) that replenishes the path to the terminal point that is present in T2.

(2) at recomputating the result, calculate the length of delay that between starting point-terminal point, takes place, confirm whether to satisfy the delay condition.Under situation about not satisfying condition, alternative costs are little path secondly, carries out the processing of (1).

And along with the enforcement of recomputating, imagination is on path before changing, and often the satisfied example of condition after changing of terminal point of delay condition is not satisfied in generation.Owing to problems such as recomputating of the path that takes place to be caused by this state of affairs, thereby imagination computing time can be longer.

For providing of realizing serving fast, require path setting to carry out at short notice.Yet, adopting under the situation of above-mentioned mode in the past because a lot of times of path computing consumption, thereby the service time started postpone.

On the other hand, as the technology of setting the multicast transfer path according to the path setting that adopts above-mentioned cast communication path setting technology to be calculated, can use MPLS (multiprotocol label switching).For example, to using a bit setting of MPLS, carry out the label exchange and transmit (for example, reference literature 3) to the label switched path of multiple spot (point-to-multipoint).

And,, have technology shown in Figure 23 as can in the VPN that uses MPLS, carrying out the technology that multicast transmits.In the example shown in this figure, (ProtocolIndependent Multicast: the agreement independent multicast) the PIM example in example and the provider's network differentiates the PIM in the VPN website.Have the VRF table in pe router, this VRF indicator is handled the PIM example to each VPN website of accommodating.And, have the shared PIM example of provider's network (for example, reference literature 4) at provider's network side.

This background technology is described in following document.

(document 3)

http://www.ietf.org/internet-draft/draft-yasukawa-mpls-rsvp-multicast-01.txt

(Extended?RSVP-TE?for?Multicast?LSP?Tunnels)IETF

(document 4)

http://www.ietf.org/internet-draft/draft-rosen-vpn-mcast-04.txt

(Multicast?in?MPLS/BGP?VPNs)IETF

Yet, although set the technology of multicast issuing path with MPLS in the past, can use the setting of a bit arriving the label switched path of multiple spot of MPLS, carrying out the label exchange transmits, but because the label switched path that sets is some label switched path to multiple spot of single layering, thereby the incoming traffic (traffic) of using this label switched path to carry out the label exchange all is sent to same destination.That is, be sent to all leaf nodes that constitute label switched path by label.Figure 24 illustrates the problem of this technology.In the example of this figure, set from the edge router PE#1 of provider to the edge router PE#2 of provider, multicast LSP (the Label SwitchedPath: label switched path) of 3,4 first layering.Therefore, Customer Edge router CE#A1, the B1 that the edge router PE#1 of provider accommodates, the traffic of C1 transmit according to same topology, and be irrelevant with each audiovisual state of organizing of the edge router PE#2 of provider, 3,4 subordinates.Consider from the viewpoint of network transmission efficiency,, thereby do not expect to occur owing to this is equivalent to the cast communication amount is sent to unwanted point.For example, there is not the recipient of C1 group the edge router PE#2 subordinate of provider, yet, causes the surplus utilization of Internet resources by the traffic that issue C1 organizes.

Like this, use the label exchange of this technology to realize transmitting with any label to the identical transmission topology of multiple spot.Therefore, when share set a bit to label exchange LSP of multiple spot, when promptly the son group was carried out the multicast issue to the part set of the leaf node group that constitutes label exchange LSP, the problem of generation was, also multicast label is sent to beyond the leaf node that constitutes the son group, and the part multicast transmits and can not carry out.

And, on the VPN of MPLS, realize in the technology of multicast transmission, require in provider's network, to install PIM-SM multicast routing protocol.In the VPN multicasting technology shown in Figure 23, PIM example in the VPN website and the PIM example in provider's network are differentiated.In pe router, have each VPN website of being accommodated is handled the VRF table that the PIM example is handled.

And, have the shared PIM example of provider's network at provider's network side.At this moment, between the pe router of provider's network, use the meeting point to form the multicast issuing path at each VPN website.In the example of Figure 23, the multicast path of VPN#A and VPN#B is set.As everyone knows, PIM-SM (Protocol Independent Multicast Sparse Mode: agreement independent multicast sparse mode) be IP multicast routing protocol, owing under the situation that realizes the multicast issue, need the meeting point, thereby thereby the meeting point becomes single barrier point shortage reliability, and because PIM-SM is an IP multicast routing protocol, though in provider's network, set the multicast issuing path, yet can't carry out to guarantee QoS (Quality of Service: path setting service quality), and with the corresponding path setting of the traffic, thereby the problem that produces is can not realize that in the network terminal/terminal tight QoS guarantees and traffic engineering.

And, handle multicast state ((S owing to require the P router (provider's router) in provider's network, G), (*, G)) PIM-SM changes multicast state continually according to the audiovisual state of cast communication amount on the path of multicast, owing to require the high frequency of the high speed P router ground of provider's core to carry out this frequent state variation, thereby the problem of existence is, do not have a practicality as network integral body.

And, because for each VPN sets multicast path, thereby the problem that exists is, multicast linking number in provider's network increases, and, connect interior traffic release model owing to can not control multicast, thereby the problem that exists is, in the VPN website, exist under the situation of a plurality of cast communication amounts, the unwanted traffic also is published to the VPN website that does not have the recipient.

Summary of the invention

The present invention proposes in view of above-mentioned aspect, the purpose of this invention is to provide the raising of the computational speed that can realize the multicast transfer path, and can be implemented in multicast transfer path establishing method, multicast transfer path calculation element, the multicast transfer path calculation procedure of reduction of cost of the path integral body when generating the limits value occur in the length of delay between starting point and the terminal point and the storage medium of having stored multicast transfer path calculation procedure.

And, the purpose of this invention is to provide and can carry out the multicast label switching method that multicast is issued at each cotyledon group of the different piece set that constitutes the leaf node in the multicast label switching path.

Another object of the present invention provides to set between provider's edge router in Virtual Private Network to be shared in the multicast path, broadcasts the multicast label switching method of cloth according to the realization of the traffic pattern in Virtual Private Network best group.

In order to achieve the above object at least one, multicast transfer path establishing method according to an embodiment of the invention, in the multicast network that constitutes by a plurality of nodes that are provided with the multicast conveyer separately, the multicast transfer path that uses multicast transfer path calculation element to connect given starting point and a plurality of terminal points respectively calculates, use multicast transfer path setting device that the multicast transfer path that is calculated is set, in this multicast transfer path establishing method

The multicast conveyer:

To each link in the multicast network, and each flow direction when data are flowed through this link, measure traffic state, by measurement result being sent to multicast transfer path calculation element, multicast transfer path setting device carries out the computation requests of multicast transfer path;

Multicast transfer path calculation element:

According to as the obtained measurement result of computation requests, calculate connection source and a plurality of terminal points with postpone relevant shortest path, calculate delay simultaneously from the arbitrary node on the shortest path to each terminal point, the value record that is calculated in storage medium;

Calculate the maximum delay when on the shortest path of data flow through being calculated;

Maximum delay and delay condition given in advance are compared, under the situation that does not meet this delay condition, reset this delay condition, under the situation that finds the condition that meets shortest path, in this shortest path that is calculated, from with starting point, these 3 kinds different types of any 2 nodes of the breakout in terminal point and path, 2 nodes perhaps of the same race are end points, and on the way do not comprise among the path group of part arbitrarily of these 3 kinds of nodes, the path of 2 internodal cost maximums at retrieval two ends, this path that retrieves is deleted from this shortest path, the multicast transfer path is divided into 2 path trees, the path setting that calculates is separately become to be used for the additional path that becomes the path of deleting object that these 2 path trees are connected;

The result of calculation of being calculated is notified to multicast transfer path setting device;

Multicast transfer path setting device:

According to the result of calculation of collecting, set the multicast transfer path.

According to another embodiment of the present invention, the multicast transfer path calculation element in the multicast network has:

The measurement result receiving element, the measurement result of the traffic state in the receiving group network;

The metrical information memory cell, the measurement result that storage is received;

The metrical information memory cell stores measurement result in the metrical information memory cell into; And

Path-calculating element reads measurement result from the metrical information memory cell, carry out path computing according to this measurement result;

Path-calculating element has:

The shortest path delay calculation unit, calculate connection source and a plurality of terminal points with postpone relevant shortest path, calculate delay simultaneously from the arbitrary node on the path to each terminal point, the value record that is calculated in storage medium;

The maximum delay computing unit calculates the maximum delay when on the shortest path of data flow through being calculated;

Maximum cost route search unit, maximum delay and delay condition given in advance are compared, under the situation that does not meet this delay condition, reset this delay condition, under the situation that finds the condition that meets shortest path, in this shortest path that the shortest path computing unit is calculated, from put these 3 kinds different types of any 2 nodes or 2 nodes of the same race with starting point, terminal point and path branches is end points, and do not comprise in the arbitrary portion group of paths of these 3 kinds of nodes the path of 2 internodal cost maximums at retrieval two ends on the way;

The path tree cutting unit is deleted the path of being retrieved from this shortest path, the multicast transfer path is divided into 2 path trees; And

Replenish path-calculating element, the path setting that calculates is separately become to be used to connect additional path these 2 path trees, that become the path of deletion object.

Multicast transfer path calculation procedure according to another embodiment of the present invention, carry out on computers, its measurement result according to the traffic that takes place on the link in the multicast network that is received is calculated the multicast transfer path, it is characterized in that, comprises following steps:

The shortest path delay calculation step, calculate connection source and a plurality of terminal points with postpone relevant shortest path, calculate delay simultaneously from the arbitrary node on the path to each terminal point, the value record that is calculated in storage medium;

The maximum delay calculation procedure is calculated the maximum delay when on the shortest path of data flow through being calculated; And

Replenish the path computing step, maximum delay and delay condition given in advance are compared, under the situation that does not meet this delay condition, reset this delay condition, under the situation that finds the condition that meets shortest path, in this shortest path that the shortest path computing unit is calculated, from with starting point, these 3 kinds different types of any 2 nodes of the breakout in terminal point and path, 2 nodes perhaps of the same race are end points, and on the way do not comprise among the path group of part arbitrarily of these 3 kinds of nodes, the path of 2 internodal cost maximums at retrieval two ends, this path that retrieves is deleted from this shortest path, the multicast transfer path is divided into 2 path trees, the path setting that calculates is separately become to be used for the additional path that becomes the path of deleting object that these 2 path trees are connected.

As mentioned above, in the present invention,, can not change in the partial tree of shortest path the shape of the terminal point in the path of deletion object, and generate the multicast transfer path as the partial tree of root by the terminal point in additional path being fixed as the terminal point in path of deletion object.

And, in the present invention, by according to the cost effective choice benchmark of cutting down whole tree being selected to replenish the path, compare as the multicast transfer path calculation element of transfer path with the shortest path between terminal point with widely used employing starting point in the past, be effective to cutting down path cost.And, in the present invention, only, can easily carry out the calculating of transfer path by utilizing the collecting function of the network measure information of representing the traffic state in the existing network.And the advantage that has is, multicast transfer path calculation element is obtained network measure information and is easy to, and there is no need to develop New Deal and is used to collect transfer path and calculates needed network measure information.

According to the multicast label switching method of another embodiment of the present invention, in multicast communication network, set the label switched path that is used for the multicast issue of group node from the multicast source node to the multicast leaf, in this multicast label switching method,

Set any label switched path to the upper layering of multiple spot from source node to all leaf nodes;

For a bit extracting a plurality of son groups behind the leaf node of any destination to the leaf node group of the label switched path of multiple spot out, each label that should the child group uses second layering is set the label switched path of a plurality of second layerings of the partial tree of the label switched path that constitutes first layering from what set;

Make the label switched path that has been used as stratified first layering and the label switched path of second layering, carry out label when exchange, the tag edge router of input side have with the destination leaf group corresponding with the label of second layering be the destination destination-address traffic distribution and give to corresponding stratification label;

The relaying LSR is right according to the label of first layering and second layering, and the label exchange is carried out in grouping to data;

Be designated as a bit at via node under the situation of branch node of multipoint label switch paths, to being replaced as the corresponding output label with a plurality of output branches, to duplicate input label right for each exports branch input label;

The output label edge router carries out label and removes in the judgement of carrying out the layered label group, simultaneously the stratified label data of being imported is packet-switching to output line;

Use any any LSP to multiple spot to second layering of the partial tree of first layering of interior a plurality of second layerings of formation of the LSP of multiple spot, in the label switched path of sharing first layering, each son group at second layering is carried out the label exchange with the traffic, and the partial tree of first layering of wherein a plurality of second layerings constitutes the different purpose background group in the leaf group node of first layering.

As mentioned above, the invention is characterized in: when setting the multicast label switching path, using the stratification label, utilize first layered label to set and share the multicast label switched path, is a plurality of part multicast label switching paths of destination with the child group at the next setting at different levels; Simultaneously, via node is judged the stratification label, uses stratification label integral body to carry out the label exchange.In the prior art, a great difference is arranged in the following areas, that is: when multicast transmits,, also be sent to all leaves according to same topological multicast even possess the technology of stratification label; And under the situation with stratification label, only first layering is used as the label exchange message and utilizes, and the following label of second layering is replicated and does not change label value at breakout.

And, the present invention, about the VPN multicast, principal character is: the same with the RFC2547bis structure, the label of sharing the label switched path that a bit arrives multiple spot that first layered label is used for connecting between pe router exchanges; The label of second layering is used for the label exchange that VPN website that pe router accommodates is used; And the 3rd layered label used in other label of the traffic class exchange that is used for distinguishing in the VPN website.Be with the difference of conventional art: share the multicast label switched path by using, in provider's network, set the multicast issuing path efficiently; And by setting the multicast issuing path, can with the VPN website in the best issuing path that adapts of traffic condition on carry out multicast and transmit, thereby the unwanted multicast replication traffic can not take place in provider's network, can carry out network application efficiently.

Like this, in the present invention, can set best shared multicast communication path according to the destination group and the qos requirement condition of each cast communication amount.And, because network integral body can effectively be utilized frequency band, thereby can construct high performance multicast delivery network and VPN network.

Other purposes of the present invention, feature and advantage are read following detailed description the in detail by the reference accompanying drawing and be will be appreciated that.

Description of drawings

Fig. 1 is used for figure that principle of the present invention is described.

Fig. 2 is a principle assumption diagram of the present invention.

Fig. 3 is used for the figure that the summary to one embodiment of the present invention describes.

Fig. 4 is the pie graph of the multicast transfer path calculation element in the one embodiment of the present invention.

Fig. 5 is the pie graph of the multicast transfer path setting device in the one embodiment of the present invention.

Fig. 6 is the flow chart of the transfer path computational algorithm in the one embodiment of the present invention.

Fig. 7 is an example of the object network of one embodiment of the invention.

Fig. 8 is the figure that delay minimal path in starting point that data are transmitted of one embodiment of the invention and the path that each terminal point is connected is shown.

Fig. 9 is the figure that the deletion object path calculating of one embodiment of the invention is shown.

Figure 10 is the figure that the part path that is generated behind deletion cost maximum path of one embodiment of the invention is shown.

Figure 11 is the topology that the additional path computing of one embodiment of the invention is used.

Figure 12 is the figure that the additional path computing result of one embodiment of the invention is shown.

Figure 13 is the figure that the path computing result of one embodiment of the invention is shown.

Figure 14 be in the 1st execution mode of the present invention consideration the best group between the pe router behind the connection VPN website (CE) broadcast the cloth pattern.

Figure 15 be in the 1st execution mode of the present invention consideration the best multicast signaling between the pe router behind the connection VPN website (CE).

Figure 16 is that the best stratification tree that the multicast issue connects between pe router after connection VPN website (CE) has been considered in the realization in the 1st execution mode of the present invention is specified signaling.

Figure 17 is the multicast issuing path example in the 1st execution mode of the present invention.

Figure 18 is the subtree of the VPN#A in the 1st execution mode of the present invention.

Figure 19 is that the best stratification by realizing multicast issue connection between pe router in the 1st execution mode of the present invention is set the specified MPLS label swap table of specification signal.

Figure 20 is consideration in the 1st execution mode of the present invention the has been shown figure that broadcasts cloth path setting method of the best group behind the release model of the multicast source in the website.

Figure 21 is used for figure that the multicast issuing path exchanging mechanism between the PE of the 1st execution mode of the present invention is described.

Figure 22 has adopted VPN model of the present invention.

Figure 23 is the VPN model (Rosen) in the conventional art.

Figure 24 is connection of the multicast between pe router in the past and the multicast transfer mode of giving CE in the VPN website.

Embodiment

Fig. 1 is used for figure that principle of the present invention is described.

The present invention is a kind of multicast transfer path establishing method, in the multicast network that constitutes by a plurality of nodes that are provided with the multicast conveyer separately, use multicast transfer path calculation element that the multicast transfer path that given starting point and a plurality of terminal points are connected is respectively calculated, use multicast transfer path setting device that the multicast transfer path that is calculated is set.With reference to Fig. 1, each step is described.

The multicast conveyer is to each link in the multicast network, and each flow direction when data are flowed through this link is measured traffic state (step 1).Then, by measurement result being sent to multicast transfer path calculation element, carry out the computation requests (step 2) of multicast transfer path to multicast transfer path calculation element.

Multicast transfer path calculation element is according to the measurement result as computation requests that obtains from the multicast conveyer, calculating is connected starting point with a plurality of terminal points shortest path (step 3), (step 4) is the value record that is calculated (step 5) in storage medium in the delay of calculating from the arbitrary node on the shortest path to each terminal point.Afterwards, multicast transfer path calculation element calculates maximum delay when on the shortest path of data flow through being calculated (step 6) compares (step 7) to maximum delay that is calculated and delay condition given in advance.Under the situation that does not meet delay condition given in advance, reset this delay condition.Under the situation that finds the condition that meets shortest path, in the shortest path that is calculated, from these 3 kinds different types of any 2 nodes of breakout or 2 nodes of the same race with starting point, terminal point and path is end points, and on the way do not comprise among the path group of part arbitrarily of these 3 kinds of nodes, path (the step 8) of 2 internodal cost maximums at retrieval two ends, this path that retrieves is deleted from this shortest path (step 9) is divided into 2 path tree (step 10) to the multicast transfer path.Then, (step 11) is notified to multicast transfer path setting device (step 12) to result of calculation the path setting that calculates separately to be become to be used for the additional path in the path that becomes the deletion object that these 2 path trees are connected.

Multicast transfer path setting device is set multicast transfer path (step 13) according to the result of calculation that receives.

Fig. 2 is a principle assumption diagram of the present invention.Have with lower unit according to the multicast transfer path calculation element in of the present invention, the multicast network: measurement result receiving element 130, the measurement result of the traffic state in the receiving group network; Metrical information memory cell 112, the measurement result that storage is received; Measurement result memory cell 111 stores measurement result in the metrical information memory cell 112 into; And path-calculating element 120, from metrical information memory cell 112, read measurement result, carry out path computing according to this measurement result.

Path-calculating element 120 also has with lower unit: shortest path delay calculation unit 1211, calculating is connected starting point with a plurality of terminal points shortest path, calculate delay simultaneously from the arbitrary node on the path to each terminal point, the value record that is calculated in storage medium 122; Maximum delay computing unit 1212 calculates the maximum delay when on the shortest path of data flow through being calculated; Maximum cost route search unit 1213, maximum delay and delay condition given in advance are compared, under the situation that does not meet this delay condition, reset this delay condition, under the situation that finds the condition that meets this shortest path, in this shortest path that calculates by shortest path computing unit 1211, from with starting point, these 3 kinds different types of any 2 nodes of the breakout in terminal point and path, 2 nodes perhaps of the same race are end points, and do not comprise among the path group of part arbitrarily of these 3 kinds of nodes the path of 2 internodal cost maximums at retrieval two ends on the way; Path tree cutting unit 1214 is deleted the path of being retrieved from this shortest path, the multicast transfer path is divided into 2 path trees; And additional path-calculating element 1215, the path setting that calculates separately become to be used for the additional path in the path that becomes the deletion object that these 2 path trees are connected.

Below, with reference to accompanying drawing embodiments of the present invention are described.

Fig. 3 is used for the figure that the summary to one embodiment of the present invention describes.In addition, numbering in () among this figure and the numbering correspondence of the following description.

The present invention is a kind of multicast transfer path establishing method in there is multicast network under the situation of higher limit in the length of delay that takes place when origin-to-destination transmits.And this multicast network is made of a plurality of nodes that are provided with multicast conveyer 300, and one of them node of each node is provided with multicast transfer path calculation element 100 or multicast transfer path setting device 200.

And, each direction that 300 pairs of data of multicast conveyer in the network flow is collected the network measure information (1) that is illustrated in the data transfer delay that takes place on each link etc., then, multicast conveyer 300 is notified to (2) such as multicast transfer path calculation element 100 and multicast transfer path setting devices 200 to network measure information.Then, when the certainty of the setting of the transfer path of the data that taken place to transmit by multicast, multicast transfer path setting device 200 and multicast transfer path calculation element 100 are carried out the setting of data transfer path according to the described processing in back.

In the present invention, multicast conveyer 300 has the function of the network measure information that is collected in the data that transmit between node, multicast transfer path calculation element 100 has the function of calculating transfer path, and multicast transfer path setting device 200 has the function of setting transfer path.And 1 node has the function of a plurality of said apparatus sometimes.

Herein, be under the situation of different device at multicast transfer path setting device 200 and multicast transfer path calculation element 100, multicast transfer path setting device 200 carries out transfer path to 100 requests of multicast transfer path calculation element and calculates (3).Multicast transfer path calculation element 100 is to the path calculation module indication path computing (4) of self.And be under the situation of same apparatus at multicast transfer path setting device 200 and multicast transfer path calculation element 100, multicast transfer path setting device 200 is to the path calculation module indication path computing (4) of self.Then, the path calculation module of multicast transfer path setting device 200 or multicast transfer path calculation element 100 is according to collected information calculations transfer path (5).Then, result of calculation is notified to the path setting module (6) of multicast transfer path setting device 200, receives the multicast transfer path of multicast transfer path setting device 200 setting datas of this result of calculation.In addition, in the function of collecting above-mentioned network measure information, by to the OSPF-TE that proposed (Open Shortest Path First-TrafficEngineering: Open Shortest Path First-traffic engineering), (IntermediateSystem-Intermediate System-Traffic Engineering: intermediate system-intermediate system-traffic engineering) the collection network metrical information is used in etc. the expansion with path computation protocols of the function of switching network metrical information between adjacent node to IS-IS-TE.

And multicast transfer path calculation element 100 has: the function that receives network measure information from multicast conveyer 300; And send the packet transmitting function of the result of calculation of transfer path; The program that preservation realizes the algorithm that uses in path computing, network measure information, path calculation program and path computing result's storage medium; And the path computation function of execution route calculating.

And the path calculation program that uses among the present invention has following function: calculate the function from the starting point of transfer path to the shortest path of each terminal point; The function of short delay that calculating will be calculated in the execution in step of the path of shortest path from the point on the path to each terminal point; From the path that constitutes shortest path is end points with any point in starting point, terminal point, the path branches point, does not comprise in the intermediate point in path in the continuous path of starting point, terminal point, path branches point, and retrieval has the function in the path of maximum cost; And deletion becomes the path of result for retrieval, the path in the path of being deleted as a supplement, the terminal point in path is the terminal point in the path of being deleted, and the starting point in path comprises the function of the node of alternative costs minimum the arbitrary node of partial tree of shortest path of starting point in the path of being deleted from formation.

According to above-mentioned functions, in the present invention, by the terminal point in additional path being fixed as the terminal point in path of deletion object, can generate the multicast transfer path, and the terminal point that need not change in the partial tree of shortest path with the path of deletion object is the shape of the partial tree of root.

And, in the present invention, by according to selecting to replenish the path to cutting down the whole cost effective choice benchmark of tree, compare as the multicast transfer path calculation element of transfer path with the shortest path between terminal point with widely used employing starting point in the past, be effective to cutting down path cost.And, in the present invention, only, just can easily carry out the calculating of transfer path by utilizing the collecting function of the network measure information of representing the traffic state in the existing network.And the advantage that has is that multicast transfer path calculation element 100 can easily be obtained network measure information, there is no need to develop New Deal for the collection transfer path calculates needed network measure information.

Below, to for realizing that multicast transfer path setting means of the present invention needed multicast transfer path calculation element 100 and multicast transfer path setting device 200 describe.

Fig. 4 illustrates the structure of the multicast transfer path calculation element 100 in the one embodiment of the present invention.Multicast transfer path calculation element 100 shown in this figure comprises: on the Information Management Department 110, management and node in network, make the relevant network measure information of delay, cost that takes place on the link of each node connection; Transfer path calculates in path computing portion 120; And packet handling part 130, the grouping that processing will be received and dispatched.And the packet handling part 130 of multicast transfer path calculation element 100 receives by the reception of the network measure information of Information Management Department 110 management, path computing request, the result of calculation of the transfer path of path computing portion 120 calculating is sent to multicast transfer path setting device 200.

Information Management Department 110 has: the routing protocol module 111 of processing protocol; And metrical information storage part 112, the network measure information of the network topology that obtained by this agreement, delay, cost etc. is managed.

And path computing portion 120 has: the path calculation module 121 that calculates transfer path; And storage computation result's result of calculation storage part 122.

And packet handling part 130 has: packet processing module 131, judge the packet kind that arrives, and transmit this packet, perhaps send to Information Management Department 110; Packet transmits table storage part 132, and recorded data packets transmits the destination; And one or more network interfaces 133.

Fig. 5 illustrates the structure of the multicast transfer path setting device in the one embodiment of the present invention.

In the figure, multicast transfer path setting device 200 comprises: on the Information Management Department 210, management and node in network, the delay information relevant with cost that takes place on the link; Determination part 220 is measured handled the delay taken place and cost etc. by self; Path setting carries out path setting with protocol processes portion 230 when new data flow takes place; And packet handling part 240, the packet that arrives is handled.

And the basic comprising of Information Management Department 210 is identical with the Information Management Department 110 of multicast transfer path calculation element 100, has routing protocol module 211 and metrical information storage part 212.

And determination part 220 has the mensuration module, and the information of processing delay of the state of the network interface 243 (aftermentioned) that this mensuration module has data packet transaction portion 240, each node on the network etc. is measured.

Packet handling part 240 has: packet processing module 241, and the kind of the packet that judgement arrives is carried out packet and is transmitted, and new path setting decision is judged; Packet transmits table storage part 242, the transmission destination of recorded data packets; And network interface 243.

And multicast transfer path setting device 200 has path computing portion 250, and path computing portion 250 has: computing module 251, calculate transfer path; And result of calculation storage part 252, storage computation result.In addition, under the situation of the calculating of being carried out transfer path by multicast transfer path setting device 200, this path computing portion 250 carries out the processing identical with multicast transfer path calculation element 100.

Path setting is set request with protocol processes portion 230 from packet handling part 240 RX path, carries out this path setting request is sent to the processing of multicast transfer path calculation element 100.And path setting has the function of setting the transfer path that is used for the data transmission according to the result of calculation of the transfer path that receives from multicast transfer path calculation element 100 with protocol processes portion 230.

In addition, at multicast transfer path calculation element 100 and multicast transfer path setting device 200 is under the situation of same node, this node has each handling part of multicast transfer path calculation element 100 and multicast transfer path setting device 200, and carries out above-mentioned each processing.And under the situation of the function that has multicast conveyer 300 on the same node, path setting carries out path computing request with 230 pairs of adjacent nodes of protocol processes portion.

Below, the action of above-mentioned multicast transfer path calculation element 100, multicast transfer path setting device 200 and multicast conveyer 300 is described.

The node of the function with multicast conveyer 300 in the network is the network measure information of exchange expression network topology, delay, cost between adjacent node always.And each node is preserved handling the network measure information that obtains by this exchange.

The network measure information of node switching not only comprises the measured network measure information of next node, but also comprises the network measure information of other node measurements that this node preserves.By these switching motions, each node has been preserved the network measure information of link information in the whole nodes in the network and delay etc.And the node of function with multicast transfer path setting device 200 of new settings transfer path carries out path computing request to the node of the function with multicast transfer path calculation element 100.At this moment, the node of function with multicast transfer path calculation element 100 calculates transfer path according to network measure information relevant with the traffic such as the topological sum delay in the network of being managed by Information Management Department 110 and the endpoint information of sending from the node that has carried out path computing request.

At first, multicast transfer path calculation element 100 is collected path computing request from the node of the function that possesses multicast transfer path setting device 200.At this moment, multicast transfer path calculation element 100 is also collected the information of the terminal point of data transmission from multicast transfer path setting device 20.Like this, path computing portion 120 reading and recording of multicast transfer path calculation element 100 in the metrical information storage part 112 (database) of Information Management Department 110 the expression network topology and the network measure information (step 101) of traffic state.

Then, path calculation module 121 uses network measure information, and calculating is from the delay minimal path (step 102) of the delay minimum of the origin-to-destination of data transmission.At this moment, path calculation module 121 calculates from the delay minimal path of the node of the terminal point that transmits as starting point, to data with the node that sent path computing request.In addition, in the calculating that postpones minimal path, use dijkstra algorithm.Like this, calculated the delay minimal path that the node that sends path computing request arrives each terminal point.

Then, 121 pairs of the path calculation modules of multicast transfer path calculation element 100 constitute that step 102 obtains from the node of the delay minimal path of origin-to-destination, with in starting point, each terminal point, the path branches point any one, and (step 103) retrieved in the part path that does not comprise described 3 kinds of nodes on the way.

Then, in the part path of being calculated, delete this path in the path of the cost maximum of the link in selection component part path from described delay minimal path.At this moment, the endpoint information in the path that becomes the deletion object is recorded in the result of calculation storage part 122 (step 104).At this moment, described delay minimal path is divided into 2 part paths.Then, the path calculation module 121 of multicast transfer path calculation element 100 is appended in the network topology that is write down in the metrical information storage part 112 of Information Management Department 110 pseudo-starting point and the link of all nodes that comprised in the part path that comprises the starting point that postpones minimal path connecting from pseudo-starting point to the described part path of cutting apart.Afterwards, in described divided part path, do not comprise the link that the part path of starting point passed through and node and all links of being connected with this node are deleted from described topology.Yet, become the deletion object described part path starting point node and connect this node and the link of the node in non-component part path not as the object (step 105) from network topology, deleted.

Then, retrieve the path of the starting point in the part path that connects pseudo-starting point and do not comprise the starting point that postpones minimal path.At this moment, for searching route, adopt the algorithm that is called as " k shortest path first (k-thshortest path algorithm) ", this algorithm computation begins the path that number is realized k little delay from the path of realizing the minimum delay.This algorithm carries out the retrieval in the little path of k after the little path of retrieval k-1.Therefore, set the higher limit of the delay of allowing, can carry out this algorithm and all be found up to the path that is lower than higher limit.The path of being retrieved becomes the potential path (step 106) in additional path of deleting like this.

Then, in the paths that the path calculation module of multicast transfer path calculation element 100 121 calculates by the retrieval of k shortest path first, constitute the summation of the path integral body of the cost that the link in path keeps, the path of alternative costs minimum.Selected path is selected as being used to replenish the new route (step 107) in the path of being deleted.

At last, the path calculation module 121 of multicast transfer path calculation element 100 judges by the action from above-mentioned steps 103 to step 107 whether the path and the selected additional path of deletion object is same path.Under the situation that is same path, the retrieval cost is next big path, and in all searching routes, repeating above-mentioned steps is same path (step 108) up to additional path and searching route.

Result calculated turns back to the node (step 109) that has sent path computing request by path calculation module 121 by packet handling part 130 like this.

In addition, in the present embodiment, when multicast conveyer 300 is collected the network measure information that postpones etc., use OSPF-TE.OSPF-TE stores the traffic information in the network that postpones etc. in the topology information exchange message of OSPF communication protocol, and OSPF is the routing protocol of clean culture (unicast).

And, in the present embodiment, as the agreement that setting data transmits, use (Resource Reservation Protocol-TrafficEngineering: multicasting MPLS (the MultiProtocol Label Switching: multiprotocol label switching) agreement after expanding RSVP-traffic engineering) to the RSVP-TE that implements to express the path appointment.Compare with the RSVP-TE that in common MPLS, uses, multicasting MPLS is to generate LSP (Label Switched Path: append the information element that can store tree topology in message label switched path), according to this topology information, establish the technology that a bit arrives multiple spot (Point-to-Multipoint) LSP.

Below, with reference to accompanying drawing embodiments of the invention are described.

Fig. 7 illustrates the multicast network of one embodiment of the invention.

In the figure, 1.～3. the starting point of 200 expression data transfer paths represents the terminal point that data transmit.And A～I is the intermediate node between starting point and the terminal point, has the function of multicast conveyer 300.In addition, multicast transfer path setting device 200, node A～I and terminal point each node 1.～3. is by telecommunication cable (link) the formation multicast network that is connected.And each link has delay and these 2 characteristics of cost.It is generally acknowledged that the lag characteristic and the cost behavior of link are that the approach axis when entering link according to data has different lag characteristics and cost behavior.In the case, exist as link D-E, when data when right (from D to E) is mobile, lag characteristic is 1, cost behavior is 10, and when when opposite direction (from E to D) is mobile, lag characteristic is 1, cost behavior is 1 link.Then, multicast transfer path setting device 200 is according to multicast transfer path calculation element 100 result calculated, with from as starting point data be sent to terminal point 1.～terminal point 3..

In addition, each node uses above-mentioned OSPF-TE to collect the network measure information that is illustrated in the delay that takes place on each internodal link.Then, this network measure information is prenoticed to multicast transfer path calculation element 100.

Multicast transfer path setting device 200 computing relay higher limits be shown be the example in 7 path.

Fig. 8 illustrates the delay minimal path in the path of starting point that the linking number of one embodiment of the invention reportedly send and each terminal point.

From the multicast transfer path setting device 200 that becomes starting point to each terminal point 1. multicast transfer path calculation element 100 at first calculates～terminal point delay minimal path 3. when the path computing request that receives from multicast transfer path setting device 200.At this moment, multicast transfer path calculation element 100 uses dijkstra algorithm as the computational algorithm that postpones minimal path.Dijkstra algorithm often is used as the algorithm of computing relay minimal path.In addition, multicast transfer path calculation element 100 calculate from starting point 200 to terminal point 1., 2., the minimal path that respectively postpones 3. is:

Multicast transfer path setting device 200 → Node B → terminal point 1.,

Multicast transfer path setting device 200 → Node B → node D → node E → node G → terminal point 2.,

Multicast transfer path setting device 200 → Node B → node D → node E → node G → node H → terminal point 3..

At this moment, be the delay that on connection source 200 and terminal point path 3., takes place in the delay maximum that takes place between starting point → terminal point, because this value is 6, thereby satisfy and the relevant condition of delay higher limit.

Then, are arbitrary nodes in starting point, terminal point, the path branches point to postponing two ends in the part path after minimal path is cut apart, and the path that does not comprise starting point, terminal point, path branches point in the intermediate node in path is retrieved.This path is:

Starting point 200 → Node B (part path 31)

Node B → terminal point is (part path 32) 1.

Node B → node D → node E → node G (part path 33)

Node G → terminal point is (part path 34) 2.

Node G → node H → terminal point is (part path 35) 3.

Select the path of summation maximum of the cost behavior that link had in the formation path in this path.Because the cost of starting point 200 → Node B (part path 31) is 1, Node B → terminal point 1. the cost in (part path 32) is 1, the cost of Node B → node G (part path 33) is 12, node G → terminal point 2. the cost in (part path 34) is 1, node G → terminal point 3. the cost in (part path 35) is 2, thereby selecteed path is Node B → node G (part path 33).Fig. 9 illustrates the result for retrieval in path, and selecteed part path is deleted from the path that is selected as postponing minimal path.As a result, postpone minimal path and be divided into 2.Herein, be the part path representation that comprises starting point 40, be the path representation that does not comprise starting point 50.This situation illustrates at Figure 10.

Then, retrieval connects the additional path in 2 part paths 40,50.At this moment, replenish the following path of Path selection, that is: the arbitrfary point that is comprised in part path 40 is as starting point, the terminal point in deletion path, promptly the starting point in part path 50 is as the path of summation minimum of cost behavior that does not intersect, constitutes the link preservation in path on the way with the point that belongs to part path 50 in the path of terminal point.This computing method illustrates following.

The network topology of using in the calculating is used the additional network topology to calculating object of following such correction.At first, prepare pseudo-starting point 70, all nodes that belong to from pseudo-starting point 70 to part path 40 are appended link.Then, remove the link and the node except the starting point G in part path 50 and all links that are connected with this node in component part path 50.As a result, finish topology shown in Figure 11.

At this topology, use the k shortest path first to calculate the path of the starting point G that connects pseudo-starting point 70 and part path 50.The k shortest path first is that the algorithm of retrieving this path is suggested at the algorithm of retrieval from postponing to use when minimal path begins the short path of several k.When adopting the k shortest path first, consider that a delay and cost are as calculating employed characteristic value.

Is being under the situation about postponing for the characteristic value that calculate to use, the delay that takes place between starting point and each terminal point be lower than given higher limit during, recursion is used k shortest path first.That is, after calculating the short path of k-1, use result of calculation to retrieve the short path of k.In these paths, the cost behavior that link kept in formation path is additional path to the Path selection of the summation minimum of each link.

Be under the condition of cost for calculating the characteristic value that uses, when the path of the little cost of being found of maintenance k is lower than the higher limit of the delay that takes place for the first time between starting point and each terminal point, finish to calculate, the Path selection of calculating constantly at this of removing pseudo-starting point is additional path.Figure 12 illustrates the result of calculation in the present embodiment.Because connect in pseudo-starting point 70 and the path as the node G of the starting point in part path 50, the path of cost minimum is

Pseudo-starting point 70 → Node B → node D → node F → node E → node G,

Thereby removing pseudo-starting point 70

Node B → node D → node F → node E → node G

Be chosen as additional path.

In the higher limit that estimate to postpone, use the length of delay that is taken place till each terminal point that exists from the node G that starting point G write down in part path 50 to downstream at node G.In mode in the past, because the topology in part path 50 changes, thereby after part path 50 is recomputated, must calculate delay when replenishing path computing from the starting point in new part path 50 to each terminal point.In the present invention, by saving this road operation, shortened computing time.After having estimated the delay maximum, become the delay 7 that takes place on connection source 200 and the terminal point path 3. at the maximum delay that replenishes between starting point → terminal point of being realized when the path connects.Because the path has and allows that maximum delay is 7 condition, thereby in the case, satisfies the delay condition.Path as a supplement, the path of satisfying above-mentioned condition, adopt as the path in path, coupling part 40 and part path 50.

Herein, the termination condition to algorithm describes.Replenishing under the situation identical with the path of being deleted of path, perhaps replenishing under the big situation in path that the retardation ratio in path deletes, the path of being deleted becomes additional path, the end algorithm.Under different situations, enclose mark for additional path, from two ends the arbitrary nodes starting point, terminal point, the path branches point, and the intermediate node in the path does not comprise in the path of starting point, terminal point, path branches point, the path of the path cost maximum in addition of mark is enclosed in selection, after its deletion, just find additional path.Repeat this action up to all enclosing mark for all paths.Calculate result of calculation shown in Figure 13 like this.

In addition, above-mentioned multicast transfer path calculation element and multicast transfer path setting device within it portion have computer system.And above-mentioned processing procedure is stored in the storage medium of embodied on computer readable with the form of program, reads and carry out this program by computer, thereby carries out above-mentioned processing.Herein, the storage medium of embodied on computer readable is meant disk, photomagneto disk, CD-ROM, DVD-ROM, semiconductor memory etc.And, can be distributed to computer to this computer program by communication line, the computer that receives this issue is carried out this program.And, also can be in advance constructed procedure stores to the movable storage medium of the hard disk that computer was connected that moves as multicast transfer path calculation element, floppy disk, CD-ROM etc. in, be installed in the CPU when of the present invention implementing.

As mentioned above, according to the present invention, have the system of the path computing of the path computation algorithm that has been equipped with the higher limit of having considered the delay that takes place between starting point and terminal point by use with node, when there is the application of the upper limit in the delay that takes place between starting point and each terminal point in cast communication is provided, can be when satisfying the delay condition, the cost cutting of realizing route integral body.

And, by with mode reduced in comparison path computing time in the past, can shorten and be used to provide the needed time of service.Like this, can offer the user to service rapidly.

As using this cast communication path setting technology to realize the device of multicast issue (transmission), has the network that utilizes the multicast label switching method.Below, describe with reference to the accompanying drawing pair embodiments of the present invention relevant with the multicast label switching method.

At first, communication path setting mode and the packet transfer mechanism to the multicast label exchange describes.

Best group between provider edge (PE) router behind Figure 14 has illustrated consideration in the one embodiment of the present invention VPN website (CE) that connects is broadcast the cloth pattern.In the example of this figure, provider's network internal storage the edge router PE#1 of provider, PE#2, PE#3, PE#4 and with they with pe router between provider (P) router that is connected.

In PE#1, contain: belong to the CE#A1 of VPN#A, belong to the CE#B1 of VPN#B, and the CE#C1 that belongs to VPN#C.And, in PE#2, contain: belong to the CE#A2 of VPN#A, and the CE#B2 that belongs to VPN#B.In addition, in PE#3, contain: belong to the CE#A3 of VPN#A, belong to the CE#B3 of VPN#B, and the CE#C3 that belongs to VPN#C.And, in PE#4, contain: belong to the CE#B4 of VPN#B, and the CE#C4 that belongs to VPN#C.

Study the best release model that sends to the cast communication amount of other pe routers in this network from PE#1.From the viewpoint of provider's network, between pe router, set a plurality of multicast label exchanges, be not supposed to from the effective utilization of label and the viewpoint of transmission resource.Therefore, from PE#1 to

PE#

2,3,4, set any LSP (LabelSwitched Path: label switched path) that shares by all traffics to multiple spot.

In this embodiment, done illustrated path corresponding to LSP with the pipe mark among this figure.At this moment, when considering the VPN site information that is housed in each pe router, just need to have considered multicast label switching path between the pe router of website annexation of each VPN according to being housed in VPN website in the pe router.For example, in the example of Figure 14, for VPN#A, because website only is housed in PE#2 and PE#3 subordinate, thereby expect that setting PE#1 is the source, setting

PE#

2,3 is the multicast subtab switching path of leaf.In the example of Figure 14, the multicast issuing path of being represented by dotted arrow is corresponding to this multicast subtab switching path.Below, dashdotted arrow is corresponding with VPN#B, and solid arrow is corresponding with VPN#C.

In this embodiment also as can be known, in order effectively to utilize the resource of provider's network, and broadcast cloth for the best group between the corresponding pe router of the VPN website realizing and will accommodate, what set 2 layerings is effective to label switched path of multiple spot a bit.And the label switched path that it should be noted that second layering is the part set of the label switched path of first layering.

Figure 15 illustrates the signaling gear of the multicast label switching path of setting Figure 14.The multicast label signaling for example (Resource Reservation Protocol-TrafficEngineering: RSVP-traffic engineering) carry out multicast and expand and set with existing RSVP-TE by mechanism.As shown in figure 15, the multicast issue circuit that set is TERO (the TreeExplicit Route Object: the tree explicit route object) stipulate by PATH.Its concrete form is corresponding with network topology, illustrates at Figure 16.

As previously mentioned, in the present invention, broadcast the cloth path, set the multicast label switching path of 2 layerings in order between pe router, to set best group.Therefore, the TERO of the set path of the multicast label switching path of indicating to set of 2 layerings of preparation.In the example of Figure 16, regulation connects the multicast label switching path from the PE#1 (A) of first layering to PE#2 (D), PE#3 (E), PE#4 (G).TERO is stipulated by { A (0), B (1), C (2), D (3), E (3), F (2), G (3) }.This prescriptive procedure is stipulated by depth-first order (Depth First Order) algorithm.Numeric representation in () that each node attaches is apart from the distance (progression) of source node PE#1 (A).

In the example of Figure 15, be the multicast issuing path of syndeton shown in Figure 17.Owing to use the depth-first sequential algorithm for the first time at the depth direction specified path, thereby the appointment of TERO is { A (0), B (1), C (2), D (3), E (3), F (2), G (3) }.And, set the multicast LSP of each VPN the subordinate of the multicast LSP of this first layering.Because the subtree of VPN#A is from PE#1 (A) to PE#2 (D) and the subtree of PE#3 (E), and is the such structure of Figure 18, thereby the TERO of the VPN#A of second layering is TERO={A (0), B (1), C (2), D (3), E (3) }, the TERO of VPN#C is TERO={A (0), B (1), C (2), E (3), F (2), G (3) }.

According to this TERO information, as shown in figure 15, PATH is passed to leaf node.When PATH is passed to leaf node, distribute the stratification label from the downstream by Resv message.

Figure 19 illustrates the stratification label of setting at each node by this action, used by label map table and link.For example, at node PE#3 (E), all arrive owing to comprise the TERO of second layering of VPN#A, B, C, thereby on the link between CE, each VPN is given the label of A (101,30), B (101,25), C (101,5).

And, at PE#2, arrive owing to only comprise the TERO of second layering of VPN#A, B, thereby do not give the label that VPN#C uses, between link CD A (1,1), B (1,25), C (1, sky).This information arrives node C, closes to tie up in the form towards the transmission of CD, CE link from the label data grouping of BC input to be set.Because the CD link of not using to VPN#C on the link of the node C of Figure 19 is given label, thereby it should be noted that a label of (101,5) of only having set the CE link.

On VPN#A, B, the label data grouping that arrives from BC is implemented necessary label exchange and is branched off into CD, CE like this, yet the labeled packet of VPN#C is not sent to CD, is only exchanged to CE by label.This operation continues step by step up to sending node A, and each VPN is formed by stratified label switched path.Like this, the packet that is imported into node A is endowed the stratification label at each VPN, uses the stratification label to be carried out the label exchange on via node, and is published to leaf node by multicast.

Yet, only use above-mentioned mechanism, can not realize best multicast path issue at the cast communication amount in the VPN.Figure 20 has imagined following situation, has multicast source M#A, M#B, M#C in PE#1 subordinate's VPN#B that is:, has different separately multicast allocation models (Figure 20 is upper left).In the case, because on the label switched path of 2 layerings, M#A, M#B, M#C are distributed to all pe routers, PE#2, PE#3, the PE#4 that contains VPN#B, thereby network efficiency is bad.For example, the PE#4 that does not receive M#A is also carried out the multicast issue.

In order to prevent this useless multicast issue, can further give the label of the 3rd layering.In this embodiment, this label is meant the same multicast source group of distributing topology that belongs in the same VPN website.

By using the stratification mechanism of this conclusion, can realize release model arbitrarily.

Below, the VPN multicast exchange that the multicast label with above-mentioned execution mode is exchanged describes.

In order to use optimum topology to issue the cast communication amount in VPN, the tag switching of 3 layerings that illustrate in the above-mentioned execution mode is effective.

At this moment, for the mechanism of using above-mentioned execution mode connects carrying out special use between the VPN website, must between pe router, exchange with the same multicast issuing path information that will be housed in each VPN of common unicast path exchange.Figure 21 illustrates this example.As shown in the drawing, can carry out the path exchange according to the MP-BGP of rfc2547bis defined.In the example of Figure 21, the example that multicast issuing path in the VPN website that other the pe router beyond the PE1 accommodates self is published to PE1 is shown.

For example, because PE#4 accommodates VPN#A, B, thereby use MP-BGP that the multicast path MG# β of the multicast path MG# α of VPN#A and VPN#B is published to PE1.In this embodiment, unidirectional path exchange example is shown, yet exchanges by the two-way whole mesh path of carrying out between pe router, each pe router can all be held the interior multicast path of VPN website that opposed pe router is accommodated.

Like this, can set the laminated devices of having considered the multicast path in the opposed PE as multicast label switching path setting person's sending node and a bit arrive multiple spot LSP.Figure 22 illustrates and adopts VPN model of the present invention.By adopting this model, the PIM-SM multicast of VPN website animation also can carry out VPN and transmit.

As mentioned above, according to multicast label switching method of the present invention and VPN multicast label switching method, can construct in the transmission cost that suppresses multicast issuing path integral body, can carry out the multicast transmission net and the VPN net of multicast issue according to the topology that is suitable for most destination reception group.

Therefore, can construct high performance efficiently multicast delivery network.

The invention is not restricted to above-mentioned execution mode, can under the situation that does not break away from technical scope of the present invention, carry out various distortion and change.

Claims

1. multicast transfer path establishing method, in the multicast network that constitutes by a plurality of nodes that are provided with the multicast conveyer separately, use multicast transfer path calculation element that the multicast transfer path that connects given starting point and a plurality of terminal points is respectively calculated, use multicast transfer path setting device that the multicast transfer path that is calculated is set, it is characterized in that

Described multicast conveyer:

To each link in the described multicast network, and each flow direction when data are flowed through this link, measure traffic state, by measurement result being sent to described multicast transfer path calculation element, carry out the computation requests of multicast transfer path;

Described multicast transfer path calculation element:

According to as the obtained described measurement result of described computation requests, calculate the shortest path relevant that connects described starting point and described a plurality of terminal points with delay, calculate delay simultaneously from the arbitrary node on this shortest path to each terminal point, the value record that is calculated in storage medium;

Calculate the maximum delay when on the described shortest path of data flow through being calculated;

Described maximum delay and delay condition given in advance are compared, under the situation that does not meet this delay condition, reset this delay condition, under the situation of the condition of finding to meet described shortest path, in this shortest path that is calculated, from with starting point, these 3 kinds different types of any 2 nodes of the breakout in terminal point and path, 2 nodes perhaps of the same race are as end points, and on the way do not comprise among the path group of part arbitrarily of these 3 kinds of nodes, the path of 2 internodal cost maximums at retrieval two ends, this path that retrieves is deleted from this shortest path, the multicast transfer path is divided into 2 path trees, the path setting that calculates is separately become to be used to connect the additional path in the path that becomes the deletion object of these 2 path trees;

The result of calculation of being calculated is notified to described multicast transfer path setting device;

Described multicast transfer path setting device:

According to the described result of calculation of collecting, set the multicast transfer path.

2. multicast transfer path establishing method according to claim 1, in described multicast transfer path calculation element, when calculating described additional path, calculate the path that the delay that takes place is lower than cost minimum in the given upper limit and this path between described starting point and described terminal point.

3. multicast transfer path establishing method according to claim 2, in described multicast transfer path calculation element, when calculating described additional path, the starting point in the path of calculating is subordinated in the arbitrary node of the path tree that comprises starting point in described divided 2 path trees and selects, and terminal point is the terminal point that becomes the path of described deletion object.

4. multicast transfer path establishing method according to claim 3, in described multicast transfer path calculation element, when calculating described additional path, for the k shortest path first that postpones to use as known algorithm, satisfy described delay condition during carry out this algorithm.

5. multicast transfer path establishing method according to claim 4, in described multicast transfer path calculation element, when calculating described additional path, use k shortest path first for cost as known algorithm, carry out this algorithm up to the path of finding to satisfy described delay condition.

6. multicast transfer path establishing method according to claim 4, in described multicast transfer path calculation element, when calculating described additional path, when checking whether result of calculation meets described delay condition, use the delay that when shortest path calculates, records the starting point in the described storage medium when calculating beginning, carried out from starting point to described additional path and from the terminal point in described additional path to delay at each terminal point of its downstream existence.

7. a multicast transfer path calculation element is the multicast transfer path calculation element in the multicast network, it is characterized in that having:

The measurement result receiving element receives the measurement result of the traffic state in the described multicast network;

The metrical information memory cell, the described measurement result that storage is received;

The measurement result memory cell stores described measurement result in the described metrical information memory cell into; And

Path-calculating element reads described measurement result from described metrical information memory cell, carry out path computing according to this measurement result;

Described path-calculating element has:

The maximum delay computing unit calculates the maximum delay when on the described shortest path of data flow through being calculated;

Maximum cost route search unit, described maximum delay and delay condition given in advance are compared, under the situation that does not meet this delay condition, reset this delay condition, under the situation that finds the condition that meets this shortest path, in this shortest path that described shortest path computing unit is calculated, from with starting point, terminal point and path branches are put these 3 kinds different types of any 2 nodes, 2 nodes perhaps of the same race are end points, and do not comprise in the arbitrary portion group of paths of these 3 kinds of nodes the path of 2 internodal cost maximums at retrieval two ends on the way;

The path tree cutting unit is deleted this path of being retrieved from this shortest path, the multicast transfer path is divided into 2 path trees; And

8. multicast transfer path calculation element according to claim 7, described additional path-calculating element comprises: calculate the unit that the delay that takes place between described starting point and described terminal point is lower than the path of cost minimum in the given upper limit and this path.

9. multicast transfer path calculation element according to claim 8, described additional path-calculating element comprises: the unit of calculating path, the starting point in the path of calculating is subordinated in the arbitrary node of the path tree that comprises starting point in 2 path trees being cut apart by described path tree cutting unit and selects, and terminal point is the terminal point that becomes the path of described deletion object.

10. multicast transfer path calculation element according to claim 9, described additional path-calculating element comprises: for the k shortest path first of postpone using as known algorithm, satisfy described delay condition during carry out the unit of this algorithm.

11. multicast transfer path calculation element according to claim 10, described additional path-calculating element comprises: for the k shortest path first of cost application as known algorithm, carry out this algorithm satisfies the path of described delay condition up to discovery unit.

12. multicast transfer path calculation element according to claim 10, described additional path-calculating element uses the delay and the delay from the terminal point in described additional path to each terminal point that exists in its downstream of the starting point from starting point to described additional path that the shortest path that carries out write down in calculating when calculating beginning when checking whether result of calculation meets described delay condition.

13. multicast transfer path calculation element according to claim 7 is characterized in that having:

The result of calculation of described path-calculating element is logged into transfer path to be set with the unit in the control messages; And

The multicast transfer path of representing along described result of calculation sends the unit of described transfer path setting with control messages.

14. multicast transfer path calculation element according to claim 7 is characterized in that having:

Unit from the computation requests of multicast transfer path setting device receiving group transfer path; And

Described result of calculation is sent to the unit of described multicast transfer path setting device.