CN108494683A - Expansible controlling of path thereof based on graph coloring in a kind of software defined network - Google Patents

Abstract

The present invention proposes the expansible controlling of path thereof based on graph coloring in a kind of software defined network, the mode that this method is route based on source, and it is inspired by XPath methods, using the path clustering strategy based on path ID, but it polymerize the path ID for sharing same link using asterisk wildcard when polymerizeing flow table item, path ID assignment problems are decomposed into link ID assignment problem, and it is based on figure Vertex Coloring Model, under the premise of ensureing the scalability of SDN using less flow table item, the efficient assignment problem of path ID in software defined network is solved.

Description

Expansible controlling of path thereof based on graph coloring in a kind of software defined network

Technical field

The present invention relates to network communication technology fields, more particularly to flow table limited space and path are dynamic in software defined network Delay problem is arranged in state.

Background technology

In the traditional network based on TCP/IP, switching equipment is integrated with logic control and the data forwarding capability of network, Switching equipment by distributed routing protocol (such as RIP, BGP and OSPF) come learning network information, safeguard forwarding logic strategy. The management and upgrading of traditional network need to carry out software configuration or firmware upgrade, network management pole to all devices in network It is complicated, realizes that network upgrade or transmission via net are extremely difficult.Development with mobile Internet and various network services It is abundant, traditional network, which has become network, further to be developed and the obstruction of upgrading, and network ossifys getting worse.

In this background, control plane and the uncoupled thought of Forwarding plane, software defined network (Software are based on Defined Networking, SDN) concept be proposed out.In SDN, the network equipment is stateless, is only responsible for simple Data packet forwarding capability.Network-based control function is realized by the network controller concentrated, and is referred to as SDN controllers.Typically SDN network framework is divided into three application layer, control layer and infrastructure layer levels, as shown in Figure 1.Wherein, infrastructure layer master To be made of network forwarding equipment, network forwarding equipment be it is stateless, only according to the flow table item of itself to data packet at Reason and forwarding, while network forwarding equipment is responsible for reporting the command adapted thereto of equipment state event and response control layer to control layer (such as the instructions such as addition flow table item, forwarding data packet)；Control layer downwards with infrastructure layer by southbound interface agreement (such as OpenFlow agreements) communication, the behavior of network forwarding equipment is controlled, provides and connects for application layer upwardly through northbound interface agreement Mouthful；Application layer can realize different network applications by control layer, for example flow scheduling is applied and Internet resources distribution application Deng.In SDN, controller can obtain global network information, and control strategy, which is issued to network, by the form of flow table item sets In standby, the network equipment is handled data packet according to flow table rule.By the flexible programming to controller, network manager can It realizes that the management to network controls to dispose multiple programs, such as routing management algorithm and data flow dispatching algorithm etc., also may be used Third party tenant's opening API interface is thought so that it can customized privatization application.SDN allows network to be truly realized and can match Set it is programmable, its flexibility can simplify network management, accelerate transmission via net.

In the SDN based on OpenFlow, data flow is identified by source address and destination address, and controller needs are All interchangers in the transmission path of each stream install forward rule, and this fine-grained forwarding strategy may be implemented actively Path clustering, be conducive to load balancing, bandwidth safeguard and fast failure recovery etc., but there is also autgmentability and stability Both of these problems：

(1) autgmentability.Based on the interchanger of SDN in order to line-speed processing data packet on hardware, using in tri-state Key storage medium of the content addressed memory (TCAM) as storage flow table.The memory space of TCAM is deposited than common arbitrary access Expensive 400 times of reservoir (RAM) or more, power consumption are 100 times of common RAM or more.Due to TCAM storage mediums cost and power consumption all Very high, which has limited the sizes in flow table space in SDN switch.With the continuous expansion of network size and upper layer application demand Be continuously increased, required flow table quantity also increased dramatically in network, and huge challenge is brought for the deployment of SDN.

(2) stability.Mono- great advantage of SDN is exactly its flexible network managing mode, but flexibility may also can shadow Ring the stability of network.Since SDN controllers can obtain the global network view of data center, it can be according to physical network Use state and fault condition, dynamically carry out that bandwidth is flexible and Path Migration to link.When migrating transmission path, SDN Controller needs to delete in original route corresponding flow table item in every interchanger, is then issued to new flow table item along new route In every interchanger therein, this will produce certain time delay.Time delay may result in TCP flow Retransmission timeout and be even switched off, shadow Ring the stability of upper layer application.How while introducing SDN flexibilities ensure upper layer application stability be also a major challenge.

Due to conflicting for the fine-grained network-controls of SDN and the limited flow table item of SDN hardware forwarding devices, SDN is caused to apply There are scaling concerns in large scale network.Many researchers have been directed to this problem and have expanded research work, substantially can be with It is divided into flow table item caching, asterisk wildcard merges flow table item and source route three classes method.

(1) flow table item caching method：Part flow table item is cached to SDN controllers or is stored not using software switch Common flow table item, sufficient memory headroom make the limitation of flow table item number no longer become problem.With reference to：Document [1] Feng T,Bi J,Wang K.Joint allocation and scheduling of network resource for multiple control applications in SDN[C]//Network Operations and Management Symposium(NOMS),2014IEEE.IEEE,2014:1-7；Document [2] Katta N, Alipourfard O, Rexford J,et al.Infinite cacheflow in software-defined networks[C]//Proceedings of the third workshop on Hot topics in software defined networking.ACM,2014:175- 180。

(2) asterisk wildcard merges the method for flow table item：Source address based on data flow and destination address, for an interchanger Middle output port identical data flow merges the source address or destination address in their flow table items with asterisk wildcard, and as one The minimum flow table item of priority.With reference to：Document [3] Meiners C R, Liu AX, Torng E.Bit weaving:A non-prefix approach to compressing packet classifiers in TCAMs[J].IEEE/ACM Transactions on Networking(ToN),2012,20(2):488-500；Document [4] Rifai M, Huin N, Caillouet C,et al.Too many SDN rulesCompress them with MINNIE[C]//Global Communications Conference(GLOBECOM),2015IEEE.IEEE,2015:1-7。

(3) source routing refers to that the coding letter in identification transmission path is added in the sender of data flow in all data packets Breath, network forwarding equipment are forwarded according to routing information.The concept of source routing is not derived from SDN, in computer network It has it long ago in history.SDN technologies can reinforce the use of source routing, it is made to have more flexible realization method.By SDN skills Flow table item can be issued in interchanger by art, controller in advance, virtual in the edge switch or server in network Interchanger can be that each data packet is inserted into routing information, and data packet is forwarded according to routing information in a network.Controller is logical Cross the path clustering of the behavior realization active of control edge switch or virtual switch.

Simplest source routing implementation mode be by being inserted into multiple labels in the packet, each tag representation from which A port forwards data packet.Switching equipment in network needs to do two pieces thing：1) outermost layer label is popped up；2) according to pop-up Label forwarding data packet.With reference to：Document [5] Ramos R M, Martinello M, Rothenberg C E.Slickflow: Resilient source routing in data center networks unlocked by openflow[C]// Local Computer Networks(LCN),2013IEEE 38th Conference on.IEEE,2013:606-613；Text Offer [6] Jin X, Farrington N, Rexford J.Your data center switch is trying too hard [C]//Proceedings of the Symposium on SDN Research.ACM,2016:12。

The another kind of source routing, which is achieved in that, is encoded to routing information in one or several data fields, such as CONGA and XPath schemes.

CONGA is a kind of path clustering strategy of two layers of trunk formula architecture design：When being forwarded from leaf node to backbone node, Forward-path is identified using one VXLAN；When being forwarded from backbone node to leaf node, using traditional based on destination address The mode of coding.With reference to：Document [7] Alizadeh M, Edsall T, Dharmapurikar S, et al.CONGA: Distributed congestion-aware load balancing for datacenters[C]//ACM SIGCOMM Computer Communication Review.ACM,2014,44(4):503-514。

For each, one path ID of path allocation comes realizing route control, passage path ID prefixes to XPath end to end The mode of polymerization reduces the quantity of flow table item in interchanger.XPath realizes the compression of flow table item by two steps：First by all roads Diameter is divided into different set of paths, then distributes ID for each set of paths.With reference to:Document [8] Hu S, Chen K, Wu H, et al.Explicit path control in commodity data centers:Design and applications [J].IEEE/ACM Transactions on Networking,2016,24(5):2768-2781。

But in above-mentioned solution, all it there are problems that：The mode of flow table item caching in SDN controllers or Additional processing delay can be introduced when caching flow table item in software, the flow effect of delay sensitive is particularly acute.Wildcard meets And the method for flow table item improves the programming difficulty in controller, also can introduce time delay in the scheduling of data flow, in addition, compression Effect depend on the design of nodes address, and be not usually fine.The most simple realization mode of source routing is most Big advantage is that flow table item number needed for interchanger is considerably less, generally equivalent to the port number of interchanger, but due to needing in number Routing information is indicated according to multiple labels are inserted into packet, introduces additional transport overhead, and label is in transmission of data packets Insertion with pop-up again bring processing delay expense, reduce data stream transmitting efficiency.CONGA schemes are dependent on specific topology Form, it is difficult to be applied in multitiered network and complex network.The mode that XPath polymerize only by prefix, the flow table item of reduction It is very limited, and for the network of asymmetric topology, the computation complexity of XPath is especially high.

Invention content

In order to solve the limitation defect of the prior art, the present invention proposes in a kind of software defined network and is based on graph coloring Expansible controlling of path thereof, the mode that this method is route based on source, and being inspired by XPath methods, using based on road The path clustering strategy of diameter ID, but it polymerize the path ID for sharing same link using asterisk wildcard when polymerizeing flow table item, by path ID assignment problems are decomposed into link ID assignment problem, and are based on figure Vertex Coloring Model, are ensureing SDN's using less flow table item Under the premise of scalability, the efficient assignment problem of path ID in software defined network is solved.

Technical solution proposed by the present invention is based primarily upon following two aspects：

(1) present invention is in software defined network, by the way of the path encapsulation of source routing, proposes a kind of based on figure The expansible path clustering scheme of coloring, ensure that the stability of upper layer application, while in order to reduce in interchanger to greatest extent The use of flow table item polymerize the path ID for sharing same link when adding flow table item using asterisk wildcard.

(2) for the complexity that path ID is distributed in reduction scheme, it is based on the thought of " dividing and ruling ", the present invention is by path ID points It is link ID assignment problem with PROBLEM DECOMPOSITION, and the use of graph coloring model is that link carries out ID distribution.The present invention is to use for the first time Graph coloring model solves the assignment problem of network path ID.

Expansible controlling of path thereof based on graph coloring in a kind of software defined network provided by the invention, including it is as follows Step：

Step (1) distributes ID using figure vertex coloring algorithm for all links in network；

The ID for the link that all paths include is combined sequentially into order as path ID by step (2)；

The corresponding flow table item in all paths is pre-installed in the interchanger in network by step (3), is made in flow table item It polymerize the path ID for sharing same link with asterisk wildcard；

In step (4), network in edge switch or server virtual switch to each number that will enter network According to being inserted into routing information, including path ID and hop count information in packet header；

Interchanger in step (5), network will forward data packet according to the routing information of data packet head, and to jump therein Number information carries out plus an operation；

Step (6), when need change current data stream transmission path when, SDN controllers only need change network in side The routing information insert action of virtual switch in edge interchanger or server, controls it and new routing information is inserted into number According in packet header, you can so that the data packet newly to arrive is transmitted according to new path, without changing in intermediary switch Flow table item ensures the stability of upper layer application to reduce processing delay.Intermediary switch refers in network in addition to edge exchanges Other interchangers except machine.

Further, the step (1) is distributed ID for all links in network using figure vertex coloring algorithm and is specifically walked Suddenly include：

Step (11), using all links in network as vertex, will by being connected between the link of the same interchanger, Constitute figure to be colored；

Step (12) distributes ID for the vertex in figure, the maximum vertex of current saturation degree is selected every time, if there are multiple tools There is the vertex of maximum saturation, then therefrom select on the uncolored maximum vertex of figure moderate, if there are multiple maximum tops of degree again Point is then therefrom selected according to lexicographic order；When distributing ID, minimum available ID is selected；

Step (13) converts the ID that all vertex are distributed to binary system, as final link ID allocation result.

To sum up, the present invention has the following technical effects：

(1) path ID assignment problems are decomposed into link ID assignment problem by the present invention, and link ID is combined as path ID, Interchanger can be made to polymerize the path ID of shared same link by way of asterisk wildcard, compare the prefix polymerization methods of XPath, Flow table item number needed for interchanger can be greatly reduced, be with good expansibility.

(2) what the present invention finally considered is to distribute ID for link, simplifies the complexity directly for path allocation ID, is calculated Process is relatively easy, is suitable for a plurality of types of networks such as data center and ISP, compared to XPath asymmetric topology network The upper disadvantage for calculating time complexity height and effect difference, the present invention have good universality.

Description of the drawings

Fig. 1 is SDN network Organization Chart；

Fig. 2 is the exemplary plot using asterisk wildcard polymerization route ID；

Fig. 3 is using hop count information as the exemplary plot of auxiliary matched information；

Fig. 4 is link ID allocation example figure.

Specific implementation mode

Path clustering mode based on source routing, it is necessary first to for path allocation one end to end of each in network A ID, and relevant flow table item is installed in interchanger in advance.Before data packet enters network, edge switch is in data The information for indicating path ID is inserted into the packet header of packet, and data packet will be forwarded according to respective path.Work as when controller needs to change When the transmission path of preceding data flow, it is only necessary to the ID that edge switch is inserted into new route is controlled, it need not be as conventional method Flow table is issued to each jump interchanger in path like that, to reduce time delay, ensures the stability of upper layer application.And in order to ensure The autgmentability of SDN, needing to find a kind of ID distribution methods keeps the flow table item item number needed for interchanger minimum, and therefore, the present invention carries Go out a kind of path ID distribution methods based on graph coloring, and the path clustering for according to allocation result route based on source.

One, path ID distribution methods

The item number of required flow table item in the method reduction interchanger of XPath passage path ID prefixes polymerization, but this side Method effect is limited, in order to be further reduced the number of required flow table item, it is intended that using asterisk wildcard to multiple positions of path ID It sets and (is not limited to prefix) and polymerize.As shown in Fig. 2, in switch A, path 2 and path 3 are all by port 2, therefore, It can be by the way that forward rule be arranged：As path ID=01*0, it is forwarded to port 2, to which 2 flow table items are polymerized to 1, In, asterisk wildcard " * " indicates 0 or 1.And if using XPath prefix polymerization methods, cannot be by the flow table in path 2 and path 3 Item is polymerize.

However, the global path enormous amount in network, and each path may all pass through multiple and different interchangers, It is very to keep flow table item number that it uses in all interchangers as small as possible for the suitable ID of a large amount of path allocation Complicated.By the example of polymerization ID above it is found that it is mainly shared by polymerization to reduce flow table item occupancy in interchanger The path ID of same link and realize.In order to reduce the complexity of algorithm, it is based on the thought of " dividing and ruling ", the present invention is not directly Global path distributes ID, and is that all links distribute ID first, link ID is then combined as global path ID, in this way same In interchanger, the path ID for sharing identical output link can be gathered with corresponding output link part in passage path ID It closes, when matching only matches the link ID of corresponding position, to greatly reduce flow table item item number needed for interchanger, and compared to the overall situation The data volume and complexity in path, the quantity of link is relatively small, and it is relatively simple to distribute ID for link.

Since the space of data packet head is limited, so the length of path ID in reduction source routing as far as possible is needed, and road Diameter ID is made of link ID, and the link number for forming path is determined by network topology and routing decision, it would therefore be desirable to find A kind of allocation plan so that the length of link ID is minimum, i.e., in the case where not producing ambiguity, duplicate allocation link ID number, such as Shown in Fig. 3, link AB and DE can distribute identical ID number 0001, and link BC and EG can also distribute identical ID number 0010. But result of which may cause confusion when matching ID using asterisk wildcard, for example, in order to meet the routing in path 2 Demand needs to add flow table rule in interchanger E：When the 4th~7 (from left to right) of ID is 0010, forward it to hold Mouth 2.But the data packet being route according to path 1 can be also sent to port 2 by the rule, to cause mistake.In order in matching The specific location of matching ID is limited, hop count information hop is added in we, and is initialized with 1, often passes through an interchanger and adds certainly 1.For example, for path 1, when data packet reaches switch A, hop count information 1 matches the first hop-information, that is, matches Then hop count information is added 1, and is sent to corresponding port by the 0th~3 information for representing link ID in the ID of path certainly, with this Analogize, when data packet reaches interchanger E, the 12nd~15 information (0100) in hop=4, coupling path ID, according to flow table In corresponding action, hop from plus 1, and forward it to port 1.Hop count information can be stored in some existing domain of data packet head In, or in one MPLS of deposit or VLAN tag.

To sum up, path ID distribution can be decomposed into two steps：

(1) it is that each link distributes an ID, and keeps ID length used as small as possible.

(2) ID for all links that each path includes is combined in order, forms path ID.

Two, link ID distribution method

Link ID distribution can be equivalent to graph vertex coloring problem, and graph vertex coloring problem refers to as all tops in figure Point is coloured, it is desirable that adjacent vertex color is different, finally makes color category number used minimum.In link ID assignment problem In, if both links pass through the same interchanger, this both links cannot distribute identical ID, we claim this both links it Between there are conflict relationships.Using all links as vertex, it will be connected between the link with conflict relationship, then constitute to be colored Figure, institute color indicated by ID, it is therefore an objective to minimize the number of ID.

Graph vertex coloring problem is a NP-hard problem, has attracted a large amount of concern in the past few decades.It is most simple Solution be greedy sequential algorithm, also referred to as SEQ algorithms, bibliography [9] Malaguti E, Toth P.A survey on vertex coloring problems[J].International transactions in operational research,2010,17(1):1-34, algorithm are followed successively by the vertex in figure and choose the minimum available face of number Color is coloured until all vertex are all coloured in figure, and the result of algorithm depends on the sequence on vertex, different vertex suitable Sequence will produce different heuritic approaches.The greedy version of DSATUR algorithms is ranked up based on saturation degree opposite vertexes, vertex Saturation degree is equal to the number of different colours used in all colored neighbours vertex on the vertex, in each coloring, selection The current maximum vertex of saturation degree is coloured, if there are the maximum vertex of multiple saturation degrees, is therefrom selected in uncolored figure If the maximum vertex of moderate therefrom selects there are multiple maximum vertex of degree according to lexicographic order.

Greedy version using DSATUR algorithms is that link distribution ID is as follows：

Step (11) will be connected using all links in network as vertex between the link for passing through the same interchanger, Constitute figure to be colored；

Step (12) is that ID is distributed on the vertex in figure, the maximum vertex of current saturation degree is selected every time, if there are multiple tools There is the vertex of maximum saturation, then therefrom select on the uncolored maximum vertex of figure moderate, if there are multiple maximum tops of degree again Point is then therefrom selected according to lexicographic order；When distributing ID, minimum available ID is selected；

Step (13) converts the ID that all vertex are distributed to binary system, as final link ID allocation result.

For example, it is assumed that shown in network topology such as Fig. 4 (a), it, will be by the chain of same interchanger using link A~F as vertex It is connected between road, figure to be colored is constituted, as shown in Fig. 4 (b).Next ID is distributed for the vertex in figure, first selection saturation Maximum vertex is spent, since the saturation degree on current all vertex is 0, so the current uncolored maximum vertex of figure moderate of selection D distributes ID number 0 for it；Then saturation degree maximum vertex is selected from remaining vertex, the saturation degree of vertex B, C, E and F are 1, and the degree of B and C is maximum, according to lexicographic order, selects vertex B, and since ID number 0 is unavailable, ID number 1 is distributed for it；With such It pushes away, distribute ID for remaining vertex needs 4 ID in total shown in final result such as Fig. 4 (c).Convert ID to binary representation, Shown in corresponding link ID allocation result such as Fig. 4 (d), each link ID occupies 2 bits.It should be noted that the present invention uses The thought of figure vertex coloring algorithm is that link distributes ID, does not limit the selection of specific figure vertex coloring algorithm.

Three, the expansible controlling of path thereof based on graph coloring

Based on above-mentioned path ID distribution methods, in a kind of software defined network proposed by the present invention based on graph coloring can The implementation steps of extensions path control method are as follows：

Step (1) uses all links distribution ID that figure vertex coloring algorithm is in network；

The ID for the link that all paths include is combined sequentially into order as path ID by step (2)；

The corresponding flow table item in all paths is pre-installed in the interchanger in network by step (3), is made in flow table item It polymerize the path ID for sharing same link with asterisk wildcard；

In step (4) network in edge switch or server virtual switch to each data that will enter network Routing information, including path ID and hop count information are inserted into packet header；

Interchanger in step (5) network will forward data packet according to the routing information of data packet head, and to jump therein Number information carries out plus an operation；

When needing to change the transmission path of current data stream, SDN controllers only need to change edge in network step (6) The routing information insert action of virtual switch in interchanger or server, controls it and new routing information is inserted into data In packet header, you can so that the data packet newly to arrive is transmitted according to new path, without changing the stream in intermediary switch List item ensures the stability of upper layer application to reduce processing delay.Intermediary switch refers in network in addition to edge switch Except other interchangers.

Finally it should be noted that：The above embodiments are merely illustrative of the technical solutions of the present invention, rather than its limitations；Although Present invention has been described in detail with reference to the aforementioned embodiments, it will be understood by those of ordinary skill in the art that：It still may be used With technical scheme described in the above embodiments is modified or equivalent replacement of some of the technical features； And these modifications or replacements, various embodiments of the present invention technical solution that it does not separate the essence of the corresponding technical solution spirit and Range.

Claims (2)

1. the expansible controlling of path thereof based on graph coloring in a kind of software defined network, which is characterized in that including walking as follows Suddenly：

Step (1) distributes ID using figure vertex coloring algorithm for all links in network；

The ID for the link that all paths include is combined sequentially into order as path ID by step (2)；

The corresponding flow table item in all paths is pre-installed in the interchanger in network by step (3), using logical in flow table item It polymerize the path ID for sharing same link with symbol；

In step (4), network in edge switch or server virtual switch to each data packet that will enter network It is inserted into routing information, including path ID and hop count information in head；

Interchanger in step (5), network will forward data packet according to the routing information of data packet head, and believe hop count therein Breath carries out plus an operation；

Step (6), when need change current data stream transmission path when, SDN controllers only need change network in edge hand over Change planes or server in virtual switch routing information insert action, control it and new routing information be inserted into data packet In head, you can so that the data packet newly to arrive is transmitted according to new path, without changing the flow table in intermediary switch .

2. the expansible controlling of path thereof based on graph coloring, feature in software defined network according to claim 1 It is, the step (1) distributes ID specific steps for all links in network using figure vertex coloring algorithm and includes：

Step (11) is constituted using all links in network as vertex by by being connected between the link of the same interchanger Figure to be colored；

Step (12) distributes ID for the vertex in figure, selects the maximum vertex of current saturation degree every time, if having most there are multiple The vertex of big saturation degree, then therefrom select on the uncolored maximum vertex of figure moderate, if there are multiple maximum vertex of degree again, It is therefrom selected according to lexicographic order；When distributing ID, minimum available ID is selected；

Step (13) converts the ID that all vertex are distributed to binary system, as final link ID allocation result.