CN102355464A - Construction method of survivable Overlay network - Google Patents

Abstract

The invention relates to a construction method of a survivable Overlay network, which selects a plurality of paths meeting business needs for each node pair with path selection algorithm based on an overlapped punished thought, and classifies the paths into working paths and protective paths. Nodes and links in the working paths and the protective paths establish survivable Overlay level virtual topology for each node pair. Because the overlapped punishment thought is adopted, the working paths and the protective paths have great difference, so that the difference of paths in the Overlay network can be ensured, and the replacement success rate of the protective paths can be ensured after the network fails to work. Consequently, good mapping relationship is realized in networks on a business level and a bottom level with higher requirement on the reliability through the Overlay network, and the different paths provided in the Overlay network can ensure that when the network fails to work, the business can be quickly reversed into the transmission path meeting the quality of service (QoS) of the business, so that the survivability of the network is improved.

Description

Overlay network establishing method with survivability

Technical field

The present invention mainly is in order to improve the survivability of IP network, makes up a kind of Overlay network that can provide survivability to guarantee through the routing algorithm that uses overlapping punishment thought, thus the survivability of enhanced IP network.

Background technology

Along with the development of communication network technology, various novel business continue to bring out, and the demand of Network Transmission has been proposed great challenge.Traditional IP network of doing one's best can't guarantee the needed service of new type of service, thereby causes professional QoS to be met, and the problem that rate can not be collected according to business occurs.And after in network, breaking down, the survivability strategy of differentiated service can't be provided.Existing network is when guaranteeing the QoS of survice demand, to reduce network survivability as cost.

Present networks itself does not have the survivability ability, and the service of service-oriented can not be provided, and the survivability mechanism of service-oriented more can not be provided, and the physical structure in the IP network and physical topology can not at will be changed.In order to change this defective of IP network, need on IP network infrastructure, make up Overlay network with different survival abilities, make this Overlay network can strengthen the survivability of bottom-layer network, satisfy the request of different business.

Summary of the invention

Given this; Main purpose of the present invention is to provide a kind of Overlay network establishing method with survivability of service-oriented; Through QoS of survice come for each source-purpose between calculate many different transmission paths at the IP layer; Constitute virtual topology; So just can on IP network infrastructure, make up Overlay network, satisfy the demand of different business with different survival abilities.Can be in this Overlay network with the path (primary path) of best performance as professional main transmission path, other paths are as the protection path.If primary path goes wrong, system can start global protecting mechanism, switches the business to smoothly in the protection path of satisfying business demand to transmit, thereby can strengthen the survivability of network.

Overlay network establishing method with survivability of the present invention; Comprised the steps: before the virtual link of structure Overlay layer; At first in the topological structure of IP layer, utilize Dijkstra shortest path first calculation sources-purpose between optimal path, its mapping is become a virtual link; Then; Link for appearing on the optimal path is punished; Utilize dijkstra's algorithm to remove to continue to calculate sub-optimal path after accomplishing again; If the path that new-found path and front are found is all inequality; Then continue the constructing virtual link and the link that occurs is punished; If certain paths that finds with the front is identical, then only link is punished, and can not put it in the diverse path group; Then seek the protection path that satisfies condition at last, up to having found the protection path that specifies number, perhaps the penalty value in path is greater than certain value of making an appointment.So far, through above process can calculate this source-purpose between mulitpath, then can constitute an Overlay network by link in these paths and node, this Overlay network just can provide this source-purpose between communication guarantee.According to this thought just can all source-purposes between set up the Overlay network, guarantee the survivability of whole Network transmission.If the link multiplicity of selected protection path and original optimal path is when higher; When original optimal path goes wrong; The probability that the replacement path goes wrong also will improve greatly; Thereby be unfavorable for professional switching, " detouring " path selection mechanism based on overlapping punishment algorithm of being mentioned among the present invention can well be avoided this problem.

Preferably; The present invention also comprises the steps: to confirm Link State, confirms the time delay cost size on each bar link, the start node and the destination node in definite path that is inquired for; Confirm penalty factor size and punishment mode, and the path number that initialization is found at present is 0.

Preferably, wherein also comprise the steps: to utilize and prolong cost path the most in short-term in the dijkstra's algorithm calculated for given topological diagram, and the record shortest path length, in order to calculate the penalty factor of link.

Preferably, when calculating path, according to different qos parameters as metric.

Preferably, operation layer is at first confirmed professional qos parameter requirement according to the type of business, correspondingly takes out virtual topological structure then.

Preferably, said qos parameter requires to be high delay requirement or low packet loss ratio requirement.

The present invention specifically also comprises:

Concentrate in the face of this Path selection down and describe:

Model description: G=(V, E), wherein V representes set of node, E representes link set.(i j) all has the time delay cost of a broad sense corresponding with it for every in network link.Article one, source-purpose between the path, constitute { (i by a series of links _s, i ₁), (i ₁, i ₂) ... (i _D-1, i _d).Time delay on this paths is exactly the algebraical sum of the time delay on all links.

Definition 1 path of rationally detouring: a non-original path; If it not only has some other attributes such as acceptable time delay; And on link, there is bigger difference, the path of reasonably detouring of the original path of then just being known as with the original path of being selected.

The s-that defines 2 paths is similar: the ratio of the number of links that the number of links that path k and original path are shared if certain bar can detour is total with it is s, just claims that this path of detouring is similar with original path s-.

The d-that defines 3 time delays is similar: the ratio of the overall delay of the overall delay of path k and original path is d if certain bar can detour, and just claims that this path of detouring is similar with original path d-.

For the reasonable path of k bar of selecting to satisfy above definition, need satisfy following constraints:

$\min \underset{(i,j\∈E)}{\mathrm{\Σ}}{d}_{\mathrm{ij}}{x}_{\mathrm{ij}}$

s.t

$\underset{(i,j\∈E)}{\mathrm{\Σ}}{d}_{\mathrm{ij}}{x}_{\mathrm{ij}}\≤d_{\max }$

$\frac{\underset{(i,j\∈E)}{\mathrm{\Σ}}{x}_{\mathrm{ij}}^k{x}_{\mathrm{ij}}^l}{N^k}\≤s,$ $\∀l,$ k∩(l≠k)；

$\frac{\underset{(i,j\∈E)}{\mathrm{\Σ}}{x}_{\mathrm{ij}}^k{d}_{\mathrm{ij}}^k}{d_s}\≤d$

$\underset{(i,j)\∈E}{\mathrm{\Σ}}{x}_{\mathrm{ij}}-\underset{(i,j)\∈E}{\mathrm{\Σ}}{x}_{\mathrm{ji}}=\left\{\begin{array}{cc}1& i=s\\ 0& \∀i\∈V-\{s,d\}\\ -1& i=d\end{array}\right.$

Wherein symbolic interpretation is following:

d _Ij: the cost (can be time delay, bandwidth, packet loss etc.) of expression from node i to link the node j;

K: the new path number that produces of expression;

L: the path number that expression has identified;

d _Max: the professional maximum cost upper limit that can bear of expression;

D: the higher limit of cost ratio between diverse path that expression is found and the shortest path;

d _s: the cost of expression shortest path;

expressed to find the first Article K dissimilar paths in the link (i, j) between the consideration for;

S: the upper limit of the ratio of total link number in link that K bar diverse path that expression is found and shortest path are shared and the shortest K paths;

N ^k: the link number that is comprised in the K bar diverse path that expression is found.

Last conditional shows in the above-mentioned constraints, for source point, Duos one from the limit number that it flows out than the limit number that flows into it, and for terminal point, just in time opposite.For the point of all the other non-source points and terminal point in the non-directed graph of having the right, it is identical flowing out with the limit number that flows into from them.

For finding the solution the Path selection problem that satisfies above-mentioned constraints, be a very loaded down with trivial details and complicated process.Adopting a kind of heuristic---overlapping punishment algorithm solves this problem.Concrete performing step is following:

Step1: program begins, and confirms Link State, confirms the time delay cost size on each bar link, and the start node and the destination node in definite path that is inquired for confirm penalty factor size and punishment mode, and the path number that initialization is found at present are 0;

Step2: utilize and prolong cost path the most in short-term in the dijkstra's algorithm calculated for given topological diagram, and the record shortest path length, for after calculate the penalty factor of link;

Step3: calculate the time delay cost of link, judge that whether it surpasses professional allowed maximum delay value delay_Value, if surpass, then forwards Step8 to, otherwise forwards Step4 to;

Step4: define punitive measures in advance for the link in the current path;

Specifically: the broad sense time delay cost of upgrading all k paths with following replicative function:

${\mathrm{Gd}}_e^{k+1}={\mathrm{Gd}}_e^{k}f(P_1,P_2,\·\·\·\·\·\·P_k)$

Use following form for overlapping penalty:

$f(P_1,P_2\·\·\·\·\·\·P_k)={(1+\frac{\mathrm{\δ}}{d_s})}^{\mathrm{\β}}$

The meaning of penalty is that the number of times that appears in the reasonable path when a link is many more, and the possibility that this link is used once more is just more little.The size of overlapping punishment parameter has determined repeating the punishment intensity of link.Wherein parameter declaration is following:

Gd: expression broad sense cost;

denotes K cycles when link e generalized costs;

P _k: the K paths that expression has been discerned;

F (P ₁, P ₂... P _k): the overlapping penalty that the expression link cost upgrades;

δ: represent overlapping punishment parameter;

d _s: the expression starting point is to the minimum cost of terminating point;

β: the current number of times that has been used of expression link e.

Step5: judge whether current path is all inequality with all paths of finding before this, if not, then get back to Step2, otherwise forward Step6 to;

Step6: the diverse path array is put in new-found path, and the path counter that will find at present adds 1;

Step7: judge that whether the path counter value that finds at present reaches the value that requires in advance, if reach, then forwards Step8 to, otherwise forwards Step2 to;

Step8: quit a program path that output is found at present and corresponding broad sense time delay cost.

The diverse path selection algorithm that the present invention uses based on overlapping punishment thought is that each node is to setting up operating path and many corresponding protection paths in the IP physical network; Avoided the multiplicity between operating path and the protection path; Constitute the Overlay network by link in these paths and node; Path switching when implementing network and break down through this Overlay network; Avoided operating path and the situation of protecting the path to lose efficacy simultaneously, thereby can improve professional survivability demand network.

Description of drawings

Fig. 1 is for using the network architecture that this method is set up;

The Overlay layer virtual topology that Fig. 2 constructs the high business of real-time for IP based network;

Fig. 3 is the multipath selection algorithm flow chart based on overlapping punishment thought;

Fig. 4 is the multipath algorithm application instance based on overlapping punishment thought;

Fig. 5 is the survivability Overlay network topology construction process of node 1 to node 7;

Fig. 6 is the virtual topology structure at the Overlay layer that finally produces 5 from node 3 to node;

Fig. 7 is an employed network topology structure sketch map in the emulation experiment.

Embodiment

For making the object of the invention, technical scheme and advantage clearer, the present invention is set forth further in detail below in conjunction with accompanying drawing and practical implementation example.

Fig. 1 is for using the network architecture that institute's extracting method is set up among the present invention; This Overlay network topology not only can provide certain survivability attribute; Also make the Overlay layer have the ability of differentiated service, having overcome traditional IP can't provide the shortcoming towards specific transactions.According to shown in Figure 1, operation layer is at first confirmed professional parameters such as QoS (time delay, packet loss etc.) demand according to the type of business; Correspondingly take out virtual topological structure then; Make the Overlay network of structure have good survivability; Every kind of Overlay has different survivability quality, like recovery rate, recovery time and resource utilization etc., to satisfy the QoS demand of different business.

The Overlay layer virtual topology that Fig. 2 constructs the high business of real-time for IP based network; Algorithm that the present invention carries is applicable to the business that file transfer etc. is had relatively high expectations to packet loss; When the routing algorithm that adopts other makes up Overlay, can support the different service request.As shown in Figure 2; In order to support to the demand of the higher business of delay requirement to survivability; Make up in the process of the Overlay with survivability ability at abstract virtual topology; With virtual topology be created as ring topology (this ring topology can regard as by source-purpose between two incoherent paths constitute); When certain the bar link in the network or node break down; Just can start wrap protection based on ring; Can switch the business to fast on the reverse ring (another paths), satisfy professional requirement time delay.

Fig. 3 is the multipath selection algorithm flow chart based on overlapping punishment thought, and its concrete handling process is following:

Step1: program begins, and confirms Link State, confirms the time delay cost size on each bar link, confirms the start node and the destination node in the path that inquires for, and confirm penalty factor size and punishment mode, and the path number that initialization is found at present is 0;

Step2: utilize and prolong cost path the most in short-term in the dijkstra's algorithm calculated for given topological diagram, and the record shortest path length, for after calculate the penalty factor of link;

Step3: calculate the time delay cost of link, judge that whether it surpasses professional allowed maximum delay value delay_Value, if surpass, then forwards step 8 to, otherwise forwards step 4 to;

Step4: define punitive measures in advance for the link in the current path;

Specifically: the broad sense time delay cost of upgrading all k paths with following replicative function:

${\mathrm{Gd}}_e^{k+1}={\mathrm{Gd}}_e^{k}f(P_1,P_2,\·\·\·\·\·\·P_k)$

Use following form for overlapping penalty:

$f(P_1,P_2\·\·\·\·\·\·P_k)={(1+\frac{\mathrm{\δ}}{d_s})}^{\mathrm{\β}}$

The meaning of penalty is that the number of times that appears in the reasonable path when a link is many more, and the possibility that this link is used once more is just more little.The size of overlapping punishment parameter has determined repeating the punishment intensity of link.

Step5: judge whether current path is all inequality with all paths of finding before this, if not, then get back to Step2, otherwise forward Step6 to;

Step6: the diverse path array is put in new-found path, and the path counter that will find at present adds 1;

Step7: judge that whether the path counter value that finds at present reaches the value that requires in advance, if reach, then forwards step 8 to, otherwise forwards Step2 to;

Step8: quit a program path that output is found at present and corresponding broad sense time delay cost.

Fig. 4 is the multipath algorithm application instance based on overlapping punishment thought, and the present invention uses this network model to verify the algorithm of being carried.Shown in the parameter list 1 during this network model initialization.

Table 1 is based on the initiation parameter table of the multipath algorithm of overlapping punishment thought

The parameter title	Symbol	Initial value
			Start node	source	1
Destination node	terminal	7
			The link number that needs selection	path_num		3
The penalty factor size	δ	2.0
			Professional maximum delay value	delay_Value	15.0

Fig. 5 is the survivability Overlay network topology construction process that node 1 arrives node 7 in the network topology shown in Figure 4.Concrete implementation procedure is: in the Overlay virtual topology configuration process that node 1 generates after node 7 routing first, at first obtain shortest path through Dijkstra shortest path routing algorithm and be < 1,2,7 >, the shortest path value is 5.0+4.0=9.0; Then the time delay of link 1-2 and 2-7 is punished that this moment, their time delay cost became 5.0 * (1+2.0/9.0) ≈ 6.1 and 4.0 * (1+2.0/9.0) ≈ 4.9 respectively.Owing to be much to seek predefined two paths, therefore continue circulation.The virtual topology structure of Overlay layer generation so far is shown in Fig. 5 (a).The shortest path that finds for the second time is < 1,4,5,7 >, and the shortest path value is 2.0+3.0+5.0=10.0, and this time delay value does not surpass professional maximum delay value 15.0.Because it does not repeat with the path of finding for the first time; So put it in the diverse path array; Afterwards for wherein link 1-4; 4-5 and 5-7 punish; Their time delay cost becomes 2.0 * (1+2.0/9.0) ≈, 2.4,3.0 * (1+2.0/9.0) ≈ 3.7 and 5.0 * (1+2.0/9.0) ≈ 6.1 respectively.This moment from node 1 to node 7 through the virtual topology structure of the Overlay layer that generates after the routings for the second time shown in Fig. 5 (b) owing to only find two paths, still do not satisfy pre-conditionedly, circulate so get into once more; The path of finding for the third time is < 1,3,6,2,7 >, and the shortest path value is 3.0+2.0+1.0+4.9=10.9, and this time delay value does not surpass professional maximum delay value 15.0; Because it does not still repeat with preceding twice path, so put it in the diverse path array, still path is wherein punished afterwards.Reached predefined requirement owing to found 3 IP layer paths this moment, therefore withdraws from circulation.Just constituted from node 1 to node 7 the virtual topology structure of the final Overlay layer that produces by above 3 paths that calculate, shown in Fig. 5 (c).As construct the virtual topology configuration process 7 from node 1 to node, can produce corresponding virtual topology to only needing to revise corresponding initial condition for other node in the network.

Fig. 6 is under identical initial condition, and in the virtual topology structure of node 3 to structure between the node 5, wherein three paths of selecting at the IP layer are respectively < 3,1,4,5 >, < 3,6,2,7,5>and < 3,6,2,4,5>based on the diverse path selection algorithm among the present invention.

Fig. 7 is in order to verify reasonability of the present invention, the topology diagram that in emulation, is adopted.This topological diagram comprises 10 nodes, and its initial condition is as shown in table 2:

Initial parameter in the table 2 emulation experiment topology diagram

The parameter title	Symbol	Initial value
			Start node	source	1
Destination node	terminal	10
			The link number that needs selection	path_num	10
The penalty factor size	δ	2.0
			Professional maximum delay value	delay_Value	200
The largest random value in the path delay of time	ran_max	20

In simulation process, mainly follow following thinking: 1) IP layer physical link state carried out initialization, confirm the path initial point and end of asking, the path number of destination node and required searching; 2) chain-circuit time delay is carried out randomization, it is obeyed at random evenly distribute; 3) routing algorithm is found the solution qualified diverse path in according to the present invention; 4) for the query time of the diverse path calculating path similarity that is found with the replacement path; 5) according to path similarity and path query time, in identical topological structure, the performance of algorithm and K shortest path first among comparative analysis the present invention.

For carry out being mentioned among the present invention based on the path selection mechanism of overlapping punishment algorithm and the comparison of K shortest path algorithm, defined these two notions of path similarity and path searching time.

(1) path similarity

Definition: the path similarity is meant the diverse path that satisfies condition for all, the link number summation that they repeat each other.

The initial path similarity is 0; Each bar link begins from optimal path, it and each bar link in the path found is thereafter compared, if identical then similarity adds 1; Otherwise continue relatively, up to each bar link in all paths of finding is all traveled through.

(2) query time in replacement path

Definition: the path query time is meant for article one link in the optimal path, if it breaks down, begins to find the needed number of times of searching in effective replacement path from the second path.Other links in the compute optimal that uses the same method the afterwards path are averaged the number of times of searching of all links in the optimal path.

Describe according to path similarity and the definition of path query time; Can know the path similarity embodied source-purpose between the similarity degree of all diverse paths; This is worth, and the difference between the bright diverse path of novel is big more more; The duplicate paths number is few more; Thereby after optimal path breaks down; This fault is more little for the possibility that other paths exert an influence, and finds the reliability of alternative route high more; Otherwise, then find the reliability in replacement path low more.And the path query time has embodied after optimal path breaks down, and other paths substitute its validity.The more little explanation of this value finds the speed of alternative route fast and the cost that alternative route spent that find is also low more, and validity is high more; Otherwise, then find alternative route time cost long and cost high.Based on above analysis, the present invention mainly uses these two indexs to estimate routing algorithm, thereby can learn the constructed performance with survivability Overlay network.

Table 3 and table 4 are respectively among operation the present invention routing algorithm and K shortest path first respectively 10 times, and 100 times, path similarity and the comparative result of path query time in the time of 1000 times.But through routing algorithm in the test result knowledge capital invention in the superiority that has aspect the similarity of path with respect to the K shortest path first; Because after having used overlapping punishment algorithm; The weights of the feasible link that has used are punished; Therefore selected probability reduces greatly in the process of path computing next time; Therefore the path similarity is just smaller comparatively speaking, helps satisfying business demand.At path query aspect the time; With respect to the K shortest path first; Because what algorithm of the present invention was stressed is to calculate the performance path of (being that performance is in close proximity to primary path) relatively rationally; Therefore in reasonable path query process; Also embody certain superiority; Promptly in the short time, the corresponding reasonable path that just can search.Interstitial content is increased to 20 from 10 in bottom IP network topology, and link circuit condition is when complicated more, and the superiority of path similarity and query time is more obvious.

Two kinds of algorithms of table 3 operation each 10 times, 100 times, similarity comparative result in path in the time of 1000 times.

Two kinds of algorithms of table 4 operation each 10 times, 100 times, query time comparative result in path in the time of 1000 times.

Claims (6)

1. the Overlay network establishing method with survivability is characterized in that, comprises the steps:

1) in the topological structure of IP layer, utilize Dijkstra shortest path first calculation sources-purpose between optimal path, its mapping is become a virtual link;

2) punish for the link that appears on the optimal path;

3) utilize dijkstra's algorithm to remove to continue to calculate sub-optimal path; If the path that new-found path and front are found is all inequality; Then continue the constructing virtual link and the link that occurs is punished; If certain paths that finds with the front is identical; Then only link is punished, and can not put it in the diverse path group;

4) then seek the protection path that satisfies condition, up to having found the protection path that specifies number, perhaps the penalty value in path is greater than certain value of making an appointment;

5) through above process can calculate this source-purpose between mulitpath, then can constitute an Overlay network by link in these paths and node;

6) when breaking down in the network, many protection paths that the node of finding fault only need be in the Overlay that makes up finds between inquiry it and the destination node in advance are until selecting the protection path that can satisfy business demand.

2. Overlay network establishing method according to claim 1; It is characterized in that; Also comprise the steps: to confirm Link State in the said step 1); Confirm the time delay cost size on each bar link; The start node and the destination node in definite path that is inquired for; Confirm penalty factor size and punishment mode, and the path number that initialization is found at present is 0.

3. Overlay network establishing method according to claim 2 is characterized in that, utilizes to prolong cost path the most in short-term in the dijkstra's algorithm calculated for given topological diagram, and the record shortest path length, is used to calculate the penalty factor of link.

4. Overlay network establishing method according to claim 1 is characterized in that, when calculating path, according to different qos parameters as metric.

5. Overlay network establishing method according to claim 1 is characterized in that, operation layer is at first confirmed professional qos parameter requirement according to the type of business, correspondingly takes out virtual topological structure then.

6. Overlay network establishing method according to claim 5 is characterized in that, said qos parameter requires to be high delay requirement or low packet loss ratio requirement.

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