CN110380973A - Software defined network topological detecting method - Google Patents

Software defined network topological detecting method Download PDF

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Publication number
CN110380973A
CN110380973A CN201910526644.7A CN201910526644A CN110380973A CN 110380973 A CN110380973 A CN 110380973A CN 201910526644 A CN201910526644 A CN 201910526644A CN 110380973 A CN110380973 A CN 110380973A
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interchanger
topology
port
message
packet
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CN110380973B (en
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贾咏哲
徐雷
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Nanjing University of Science and Technology
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Nanjing University of Science and Technology
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    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L41/00Arrangements for maintenance or administration or management of packet switching networks
    • H04L41/12Arrangements for maintenance or administration or management of packet switching networks network topology discovery or management
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L45/00Routing or path finding of packets in data switching networks
    • H04L45/02Topology update or discovery
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L49/00Packet switching elements
    • H04L49/25Routing or path finding through a switch fabric
    • H04L49/252Store and forward routing

Abstract

The invention discloses a kind of software defined network (SDN) topological detecting methods to obtain and store interchanger and its port information method includes the following steps: SDN controller establishes connection using OpenFlow agreement and interchanger;SDN controller is the forward rule for the interchanger pre-installation topology probe grouping each having connected;SDN controller randomly chooses an interchanger in network and creates topology probe grouping as core switch for the interchanger, and periodically sends the grouping to core switch;The interchanger for receiving topology probe grouping is forwarded topology probe grouping according to the forward rule of pre-installation, and sends the packet to SDN controller;SDN controller seeks topology information according to the grouping of the topology probe of the respective switch received.Relative to the topology discovery method in current SDN, method topology probe block length of the invention is shorter, and controller and control link load are lighter, and the required topology probe time is less.

Description

Software defined network topological detecting method
Technical field
The invention belongs to computer network field, especially a kind of software defined network topological detecting method.
Background technique
With sharply expanding for network size and enriching constantly for application type, internet is as social infrastructure to pass Important a part, structure and function is increasingly sophisticated, and control ability weakens increasingly.The function that router is carried as network core Constantly extension, such as packet filtering, Differentiated Services, multicast, service quality (QoS) and traffic engineering.What router initially defined " mute ", simple data forwarding unit, which have become too fat to move, can't bear.
Software defined network (SDN) is a kind of new network architecture, is achieved in recent years in industry and academia huge Achievement.Control logic and the thought of data forwarding logic separation are the Research foundations of SDN technology, and this data plane and control are flat The decoupling many sophisticated functions for reducing network equipment carrying in face, improve new network and new protocol realization and deployment Flexibility and operability.
In order to enable SDN controller to manage network and provide the service of such as routing etc, it needs to have about net The up-to-date information of network state, especially network topology.Therefore, reliable and efficient Topology Discovery mechanism is for software defined network It is essential.Current most of controller platform is carried out by OFDP (OpenFlow Discovery Proto-col) Topology Discovery, this method be derived from original SDN controller NOX [Gude N, Koponen T, Pe-ttit J, et al.NOX: towards an operating system for networks[J].Acm Sigcomm Com-puter Communication Review, 2008,38 (3): 105-110.], by traditional network Link Layer Discovery Protocol (LLDP, Link Layer Discovery Protocol) it improves, ability existing for it, which is noticed, to neighbor node by LLDP carries out Topology Discovery, later this method also become the standard of SDN Topology Discovery.
However, being had the following problems by the SDN topology discovery method that OFDP is realized: in secure context, OFDP can controlled A large amount of exchanger informations are transmitted on link, safeguard measure but are not taken to these information, therefore attacker tends to easily Ground utilizes these information offensive attacks;In terms of efficiency, time-consuming, controller load is heavy and control link for the discovery procedure of OFDP Expense is big.
Therefore, Pakzad F et al. proposes a kind of improved method OFDPv2, by the Pack-et- for reducing SDN controller Out message improves efficiency [Pakzad F, Portmann M, Tan W L, the et al.Efficient of Topology Discovery topology discovery in OpenFlow-based Software Defined Networks[J].Computer Co-mmunications,2016,77(C):52-61.].Although OFDPv2 improves SDN Topology Discovery to a certain extent Efficiency, but there is following both sides in this method: it on the one hand, is analyzed from data surface angles of loading, OFDPv2 is not excellent Change the format of topology probe grouping, therefore the load between interchanger on physical link can not be reduced;On the other hand, it is sent out from topology Current length and the angle analysis of controller load, OFDPv2 is limited relative to the improved efficiency of OFDP, Da na Hasan with Mohamed Othman points out that the OFD Pv2 that Pakzad F et al. is proposed does not consider Packet- in the research to OFDPv2 The situation of Out retransmitting message, therefore promotion of the OFDPv2 in control link overhead when Packet-Out message retransmits It can decrease [Dana Hasan, Mohamed Othman, Efficient Topolo gy Discovery in Software Defined Networks:Revisited[J].Procedia Computer S-cience,2017,116, 539-547.]。
Summary of the invention
The purpose of the present invention is to provide one kind can reduce control load, and simplifies the SDN of topology probe packet format Topological detecting method.
The technical solution for realizing the aim of the invention is as follows: software defined network topological detecting method, comprising the following steps:
Step 1, software defined network SDN controller and interchanger establish connection, obtain and store exchanger information, exchange Machine port information;
Step 2, SDN controller pre-install forward rule to each interchanger having connected, and wherein forward rule includes and opens up Flutter the forwarding instruction and speed limit instruction of detection grouping;
An interchanger in step 3, SDN controller random selection network is handed over as core switch, and for the core One topology probe of building of changing planes is grouped, and is later sent to the topology probe packet cycle by Packet-Out message The interchanger, so that SDN controller can constantly update full mesh topology view;
Step 4, core switch exist according to the Packet-Out message of the SDN controller received according to forwarding instruction Forwarding topology detection grouping on data surface;
The interchanger that step 5, the topology probe for receiving neighboring switch are grouped, will be received by Packet-In message To topology probe grouping be sent to SDN controller, and be forwarded, be forwarded in data surface according to the forward rule of pre-installation Neighboring switch;
Step 6, SDN controller seek topology information according to the Packet-In message of the respective switch received.
Compared with prior art, the present invention its remarkable advantage are as follows: 1) when creating topology probe grouping, eliminate The fields such as Chassis ID, Port ID and TTL shorten the length of topology probe grouping, alleviate physics chain between interchanger The load of road;2) quantity for reducing the Packet-Out message for needing SDN controller to create during Topology Discovery, mitigates Controller load;3) quantity for reducing the Packet-Out message that Quality Initiative needs to send on the road, alleviates control link On load;4) the topology probe time is shortened, SDN controller can obtain full mesh topology view within the shorter time.
Present invention is further described in detail with reference to the accompanying drawing.
Detailed description of the invention
Fig. 1 is that invention software defines network SDN topological detecting method flow chart.
Fig. 2 is the structure chart of topology probe grouping in the present invention.
Fig. 3 is the schematic diagram of monocycle Topology Discovery process of the invention.
Specific embodiment
In conjunction with Fig. 1, invention software defines network SDN topological detecting method, comprising the following steps:
Step 1, software defined network SDN controller and interchanger establish connection, obtain and store exchanger information, exchange Machine port information;
Step 2, SDN controller pre-install forward rule to each interchanger having connected, and wherein forward rule includes and opens up Flutter the forwarding instruction and speed limit instruction of detection grouping;
An interchanger in step 3, SDN controller random selection network is handed over as core switch, and for the core One topology probe of building of changing planes is grouped, and is later sent to the topology probe packet cycle by Packet-Out message The interchanger, so that SDN controller can constantly update full mesh topology view;
Step 4, core switch exist according to the Packet-Out message of the SDN controller received according to forwarding instruction Forwarding topology detection grouping on data surface;
The interchanger that step 5, the topology probe for receiving neighboring switch are grouped, will be received by Packet-In message To topology probe grouping be sent to SDN controller, and be forwarded, be forwarded in data surface according to the forward rule of pre-installation Neighboring switch;
Step 6, SDN controller seek topology information according to the Packet-In message of the respective switch received.
Further, software defined network SDN controller and interchanger establish connection in step 1, obtain and store exchange Machine information, switch port information, specifically:
The connection that SDN controller and interchanger are established using OpenFlow agreement, is specifically included:
Step 1-1, it requests to connect with director port by Transmission Control Protocol after interchanger starting, after controller starting, control The TCP request of device confirmation interchanger processed, then interchanger sends OFPT_HELLO message request and establishes OpenFlow connection, controls Device receive request after to interchanger return OFPT_HELLO message to establish connection;
Step 1-2, OFPT_FEATURES_REQUEST message is sent from controller to interchanger to obtain interchanger letter Breath;
Step 1-3, OFPMP_PORT_DESC request message is sent from controller to interchanger to obtain switch port letter Breath;
Step 1-4, interchanger returns to OFPT_FEATURES_REPLY message to controller and OFPMP_PORT_DESC is returned Multiple message is respectively used to interchanger to controller reporting exchanger information, interchanger to each end of controller reporting interchanger Message breath;
Step 1-5, the OFPT_FEATURES_REPLY message and OFPMP_PORT_ that SDN controller is returned according to interchanger DESC replies message storage exchanger information and its port information.
It is exemplary preferably, in step 1-2 exchanger information include: interchanger ID, it is buffer size, flow table quantity, auxiliary Connection mark, statistical information is helped to support situation, recombination ip fragmentation that the anti-ring of situation and port is supported to support situation;
Step 1-3 middle port information include: port numbers, MAC Address, behavior mark, current state, data channel feature, Present rate and maximum rate.
Further, SDN controller is to each interchanger pre-installation forward rule having connected in step 2, wherein forwarding Forwarding instruction of the rule comprising topology probe grouping and speed limit instruction, specifically:
Step 2-1, forward rule, including following procedure are constructed:
Step 2-1-1, building forwarding instruction is to instruct interchanger to carry out the modification and forwarding of topology probe grouping, and adds Into forward rule, comprising:
(1) matching domain of setting forwarding instruction is used to match the topology probe grouping for reaching interchanger, forwards of instruction It is provided that Ethernet protocol type is topology probe protocol number with domain, purpose physics address D st MAC is Nearest Bridge group address, receiving port number are the corresponding port numbers in each port of interchanger;
(2) action fields of setting forwarding instruction forward the action fields of instruction to be grouped packet header modification and packets forwarding Setting are as follows: the grouping is directly encapsulated into Packet-In message first and is sent to SDN switch;Later, for each Switch port, addition modification packet header movement, by topology probe grouping packet header in source physical address Src MAC Address according to The secondary MAC Address for being changed to each port of interchanger, and modified address all needs addition to send the movement of grouping each time, being used for will Topology probe grouping is sent to corresponding port;
Step 2-1-2, it is instructed according to the customized corresponding speed limit of setting of present topology detection cycle, and is added to forwarding rule In then;This is because when, there are when loop, for the loop storm problem for solving topology probe grouping, SDN controller is needed in network One group of speed limit rule is pre-installed for each interchanger carry out rate control;
Step 2-2, the forward rule of building is issued in all interchangers having connected with SDN controller, is completed pre- Installation.
It is exemplary preferably, in step 2-1-1 topology probe protocol number be 0x88cc.
Further, SDN controller selects an interchanger in network as core switch in step 3, and to be somebody's turn to do Core switch constructs a topology probe grouping, by the packet cycle is sent to this by Packet-Out message later Interchanger, specifically:
According to step 1 and step 2 as a result, SDN controller tentatively has the whole network node overview, however between interchanger Available link for SDN controller not as it can be seen that therefore SDN controller will select in a random way a controller as Core switch.
Step 3-1, in conjunction with Fig. 2, a topology probe grouping is constructed for core switch specifically: topology probe grouping Structure includes Dst MAC, Src MAC, Ethernet protocol type and End TLV, and configuration is as follows respectively: configuring Dst MAC to Nearest Bridge group address, Src MAC are configured to ' 00:00:00:00:00:00 ', and Ethernet protocol type configuration is 0x88cc, End TLV are configured to two null bytes;It is different from the structure that LLDP is grouped in OFDP, the format of topology probe grouping In eliminate the fields such as Chassis ID, Port ID and TTL, so as to shorten topology probe grouping length, alleviate simultaneously The load of physical link between interchanger;
Step 3-2, in the realization of OFDP, SDN controller into the whole network each be connected to the interchanger of SDN controller Each physical port create one comprising topology probe grouping Packet-Out message.In such a mode, network is enabled In number of switches be N, the physical link number between all interchangers is L, and the port number that each interchanger has is pi, wherein i ∈ N, the quantity that SDN controller sends Packet-Out message are denoted as POUT, then haveTo improve effect Rate, modification SDN controller send Packet-Out message mode with reduce controller and control link load, specifically: enable Interchanger only sends a Packet-Out message to data surface, and SDN controller is sent to the number of Packet-Out message with this Measure POUTIt is reduced to POUT=1;
Step 3-3, the topology probe grouping pair constructed in the content obtainment step 3-1 according to (2) in step 2-1-1 Topology probe grouping and its forwarding instruction are encapsulated in the Packet-Out message of step 3-2, later by the forwarding instruction answered Packet-Out message cycle is sent to core switch by SDN controller, so that SDN controller can be constantly updated Full mesh topology view.
Further, in step 4 core switch according to the Packet-Out message of the SDN controller received, according to Forwarding instruction forwarding topology detection grouping on data surface, specifically:
In conjunction with Fig. 3, core switch is parsed after receiving the Packet-Out message of SDN controller, is extracted wherein Topology probe grouping and its forwarding instruction, for each physical port, respectively by the Src in the packet header of topology probe grouping MAC Address is changed to the MAC Address of interchanger exit port, then successively sends corresponding physical port for topology probe grouping.
Further, the interchanger that the topology probe grouping of neighboring switch is received in step 5, passes through Packet-In The topology probe received grouping is sent to SDN controller by message, and is carried out according to the forward rule of pre-installation in data surface Forwarding, is forwarded to neighboring switch, specifically:
Step 5-1, the topology probe from neighbor switch is received in conjunction with Fig. 3, core switch and non-core interchanger After grouping, flow entry matching is carried out according to the content of (1) in step 2-1-1;
Step 5-2, be forwarded according to the content of (2) in step 2-1-2, first will setting forwarding instruction action fields with It is grouped packet header modification and packets forwarding, the action fields of instruction is forwarded to be arranged are as follows: for each physical port, addition modification The movement in packet header, the Src MAC Address in the packet header of topology probe grouping is changed to the MAC of remaining port of interchanger respectively Location, then successively addition sends the movement being grouped, for sending corresponding port for topology probe grouping;
Step 5-3, each interchanger in network in step 5-2 content carry out topology probe grouping reception, It submits SDN controller and is forwarded to neighboring switch.
Further, SDN controller is sought opening up according to the Packet-In message of the respective switch received in step 6 Information is flutterred, specifically:
Step 6-1, in conjunction with Fig. 3, SDN controller is parsed from each Packet-In message received and is opened up accordingly Flutter detection grouping;
Step 6-2, it is grouped for the topology probe of each Packet-In message:
Step 6-2-1, the interchanger ID for extracting the Src MAC information in topology probe grouping, sending Packet-In message And the interchanger receives the port numbers of topology probe grouping;
Step 6-2-2, the exchanger information and its port information stored according to step 1 searches port mac address and step The identical interchanger ID of Src MAC and respective end slogan conclude the exchange generator terminal found if finding match information in 6-2-1 Mouthful and step 5 in send Packet-In message interchanger receive the topology probe grouping port between there are physical links;
By the upper physical link, that is, topology information obtained between all interchangers.
Embodiment
Software defined network topological detecting method of the invention, including the following contents:
1, SDN controller and interchanger establish connection, are shaken hands using OpenFlow agreement: in conjunction with Fig. 3, in this example There are 1 SDN controllers, are realized using Ryu controller, and there are 3 OpenFlow interchangers, real using OVS virtual switch It is existing, it is respectively designated as s1, s2 and s3, each interchanger has 2 physical ports, between each interchanger and remaining interchanger There are physical links.Link connection mode is as follows: the port 1 of s1 connects the port 1 of s2, and the port 2 of s1 connects the port 1 of s3, The port 2 of s2 connects the port 2 of s3, i.e. s1-1 connection s2-1, s1-2 connection s3-1, s2-2 connection s3-2, wherein each of the links It is two-way link.The TCP connection port of SDN controller and 3 OpenFlow interchangers are as follows: the TCP port of SDN controller is 6633 ports, the TCP port of 3 OpenFlow interchangers are respectively 41836,41840 and 41838.Net is completed using Mininet Network topology is built, and configures OpenFlow1.3 for the version of OpenFlow agreement.After the completion of network topology is built, controller Connection with interchanger will be automatically performed by Ryu controller and OVS interchanger, and detailed process is as follows: interchanger passes through Transmission Control Protocol The connection of request and 6633 port of controller, starts controller later, and controller confirms the TCP request of interchanger, then exchanges Machine sends OFPT_HELLO message request and establishes OpenFlow connection, and controller returns to OFPT_HELLO to interchanger after receiving and disappears Breath is to establish connection;After interchanger and controller complete connection, OFPT_ is sent from controller to each interchanger To obtain exchanger information, exchanger information includes: interchanger ID (datapath_id), delays FEATURES_REQUEST message Rush Qu great little (n_buffers), flow table quantity (n_tables), auxiliary connection mark (auxiliary_id), statistical information branch Hold situation, recombination ip fragmentation supports the anti-ring of situation and port to support situation (capabilities) etc.;Controller is to each exchange Machine sends OFPMP_PORT_DESC request message to obtain its port information, and the port information of each port includes: port numbers (Port_no), port mac address (Hw_addr), behavior mark (Config), current state (State), data channel feature (Current, Advertised, Supported and Peer), present rate (Curr_speed) and maximum rate (Max_ speed);S1, s2 and s3 return to OFPT_FEATURES_REPLY message to controller and OFPMP_PORT_DESC is replied message, The OFPT_FEATURES_REPLY message and OFPMP_PORT_DESC that controller is returned according to s1, s2 and s3 reply message storage Exchanger information and its port information, to realize the purpose by port mac address search switch port.
Wherein OFPT_FEATURES_REPLY message is used for interchanger to controller reporting exchanger information, the present embodiment Middle concrete outcome is as shown in table 1 below:
1 interchanger OFPT_FEATURES_REPLY message of table
Parameter s1 s2 s3
datapath_id 0x0000000000000001 0x0000000000000002 0x0000000000000003
n_buffers 0 0 0
n_tables 254 254 254
auxiliary_id 0 0 0
capabilities 0x0000004f 0x0000004f 0x0000004f
OFPMP_PORT_DESC replies message each port information for interchanger to controller reporting interchanger, this Concrete outcome is as shown in table 2 below in embodiment:
2 interchanger OFPMP_PORT_DESC of table is replied message
2, SDN controller to s1, s2 and s3 pre-installation topology probe be grouped forward rule, wherein comprising forwarding instruction and Speed limit instruction.Firstly, building forwarding instructs the forwarding for instructing s1, s2 and s3 to carry out topology probe grouping, wherein including With domain and action fields, matching domain is used to match the topology probe grouping for reaching interchanger, and action fields are used to modify packet header simultaneously Forwarding grouping.S1 has 2 physical ports, therefore configures 2 forwarding instructions for s1, is respectively set as follows:
1) in matching domain, Ethernet protocol type is " 0x88cc ", and Dst MAC is " 01:80:c2:00:00:0e ", enters end Slogan is " 1 ";In action fields, topology probe is forwarded a packet to controller by use " OFPActionOutput " first, then will packet " the Src Mac " of head is revised as " 6e:10:41:27:51:e5 ", and " OFPActionOutput " is used to be grouped topology probe It is forwarded from port 1, " the Src Mac " in packet header is finally revised as " 0e:63:1a:d1:94:ee ", and use Topology probe is grouped from port 2 and forwards by " OFPActionOutput ".
2) in matching domain, Ethernet protocol type is " 0x88cc ", and Dst MAC is " 01:80:c2:00:00:0e ", enters end Slogan is " 2 ";In action fields, topology probe is forwarded a packet to controller by use " OFPActionOutput " first, then will packet " the Src Mac " of head is revised as " 6e:10:41:27:51:e5 ", and " OFPActionOutput " is used to be grouped topology probe It is forwarded from port 1, " the Src Mac " in packet header is finally revised as " 0e:63:1a:d1:94:ee ", and use Topology probe is grouped from port 2 and forwards by " OFPActionOutput ".
S2 has 2 physical ports, therefore configures 2 forwarding instructions for s2, is respectively set as follows:
1) in matching domain, Ethernet protocol type is " 0x88cc ", and Dst MAC is " 01:80:c2:00:00:0e ", enters end Slogan is " 1 ";In action fields, topology probe is forwarded a packet to controller by use " OFPActionOutput " first, then will packet " the Src Mac " of head is revised as " f6:6c:50:bc:26:42 ", and " OFPActionOutput " is used to be grouped topology probe It is forwarded from port 1, " the Src Mac " in packet header is finally revised as " 86:4f:cb:d5:46:5e ", and use Topology probe is grouped from port 2 and forwards by " OFPActionOutput ".
2) in matching domain, Ethernet protocol type is " 0x88cc ", and Dst MAC is " 01:80:c2:00:00:0e ", enters end Slogan is " 2 ";In action fields, topology probe is forwarded a packet to controller by use " OFPActionOutput " first, then will packet " the Src Mac " of head is revised as " f6:6c:50:bc:26:42 ", and " OFPActionOutput " is used to be grouped topology probe It is forwarded from port 1, " the Src Mac " in packet header is finally revised as " 86:4f:cb:d5:46:5e ", and use Topology probe is grouped from port 2 and forwards by " OFPActionOutput ".
S3 has 2 physical ports, therefore configures 2 forwarding instructions for s3, is respectively set as follows:
1) in matching domain, Ethernet protocol type is " 0x88cc ", and Dst MAC is " 01:80:c2:00:00:0e ", enters end Slogan is " 1 ";In action fields, topology probe is forwarded a packet to controller by use " OFPActionOutput " first, then will packet " the Src Mac " of head is revised as " 06:18:24:f0:fc:8c ", and " OFPActionOutput " is used to be grouped topology probe It is forwarded from port 1, " the Src Mac " in packet header is finally revised as " 6e:b7:08:e5:5a:d5 ", and use Topology probe is grouped from port 2 and forwards by " OFPActionOutput ".
2) in matching domain, Ethernet protocol type is " 0x88cc ", and Dst MAC is " 01:80:c2:00:00:0e ", enters end Slogan is " 2 ";In action fields, topology probe is forwarded a packet to controller by use " OFPActionOutput " first, then will packet " the Src Mac " of head is revised as " 06:18:24:f0:fc:8c ", and " OFPActionOutput " is used to be grouped topology probe It is forwarded from port 1, " the Src Mac " in packet header is finally revised as " 6e:b7:08:e5:5a:d5 ", and use Topology probe is grouped from port 2 and forwards by " OFPActionOutput ".
For the loop storm problem for solving topology probe grouping, SDN controller needs to pre-install one group of limit for s1, s2 and s3 Speed instruction carries out rate control.1s is set by the present topology discovery period, correspondingly, is used " OFPInstructionMeter " constructs speed limit instruction, and it is 1pkt/s that rate size, which is arranged, it is desirable that s1, s2 and s3 will be more than The topology probe of rate, which is grouped, to be abandoned, and the instruction is added in the forward rule of s1, s2 and s3.
Configured forward rule is issued in s1, s2 and s3 by forwarding instruction with use after the completion of speed limit instruction configuration.
3, in conjunction with Fig. 3, SDN controller selects s1 as core switch, and only s1 creates a topology probe grouping simultaneously Do not include in the grouping for by the packet cycle being sent to s1 by Packet-Out message, and sending Chassis ID, The fields such as Port ID and TTL.
Firstly, modification SDN controller sends the mode of Packet-Out message, interchanger is enabled only to send to s1 primary Packet-Out message, wherein will be grouped comprising topology probe.
Then, building topology probe grouping.Similar to the structure of LLDP grouping, in conjunction with Fig. 2, the structure of topology probe grouping It is made of tetra- Dst MAC, Src MAC, Ethernet protocol type and End parts, it is successively that this four part configurations are as follows: will Dst MAC is configured to " 01:80:c2:00:00:0e ", and Src MAC is configured to " 00:00:00:00:00:00 ", Ethernet protocol Type configuration is " 0x88cc ", and End is configured to 2 null bytes to indicate that grouping terminates.
Finally, SDN controller sends the Packet-Out message being grouped comprising topology probe built in conjunction with Fig. 3 To core switch s1, and require s1 the Src MAC of topology probe packet header is respectively modified as " 6e:10:41:27:51: E5 " and " 0e:63:1a:d1:94:ee ", then be forwarded respectively from port 1 and port 2.To realize periodic Topology Discovery Mechanism, SDN controller will be using 1s as the period, and what is constantly built to core switch s1 transmission is grouped comprising topology probe.If The quantity that SDN controller sends Packet-Out message is denoted as POUT, then P at this timeOUT=1.And in the realization of OFDP, SDN Controller each each physical port for being connected to the interchanger of SDN controller into the whole network creates one and includes LLDP The Packet-Out message of grouping, in conjunction with Fig. 3, OpenFlow interchanger shares 3, and the physical link between all interchangers is total There are 3, the port number that each interchanger has is 2, then has POUT=6.
4, it is parsed, is extracted after receiving the Packet-Out message of SDN controller in conjunction with Fig. 3, core switch s1 Wherein topology probe grouping and forwarding instruction, are forwarded according to forwarding instruction, and topology probe grouping will be forwarded to s2 and s3. Specifically, s1 first passes through Packet-In message and sends SDN controller for topology probe grouping, then topology probe is grouped and is wrapped The Src MAC of head is respectively modified as " 6e:10:41:27:51:e5 " and " 0e:63:1a:d1:94:ee ", and respectively from 1 He of port Port 2 is forwarded.
5, after s2 and s3 receives the grouping of the topology probe from s1 from port 1, first passing through Packet-In message will be topological Detection grouping is sent to SDN controller, is forwarded according still further to the forward rule of pre-installation in data surface.Specifically, s2 is from end Mouthful 1 receives topology probe grouping, the Src MAC of topology probe packet header is respectively modified as " f6:6c:50:bc:26: 42 " and " 86:4f:cb:d5:46:5e ", then be forwarded respectively from port 1 and port 2;S3 receives topology probe from port 1 Grouping, by the Src MAC of topology probe packet header be respectively modified as " 06:18:24:f0:fc:8c " and " 6e:b7:08:e5: 5a:d5 ", then be forwarded respectively from port 1 and port 2.
Then, after s1 receives the grouping of the topology probe from s2 and s3 from port 1 and port 2 respectively, pass through Packet-In Message by topology probe grouping be sent to SDN controller, when forward rule again attempt to send topology probe grouping when, due to away from Topology probe grouping duration is sent less than 1s from the last time, therefore can be abandoned the topology to be sent by speed limit rule constraint and visited Survey grouping.Similarly, s2 receives the grouping of the topology probe from s3 and s3 from port 2 and receives the topology spy from s2 from port 2 After surveying grouping, SDN controller is only all sent for topology probe grouping by Packet-In message, and without topology probe The modification and forwarding of packet header.
6, topology information is calculated after receiving the grouping of the topology probe from s1, s2 and s3 successively in SDN controller, specifically It is as follows:
After SDN controller receives the Packet-In message from s2, therefrom parses and be grouped simultaneously from the topology probe of s1 Parse s2 receive the grouping port be 1, then by topology probe be grouped in Src MAC and storage switch port MAC is compared, it can be determined that it is identical as the MAC of port 1 of s1 to go out the MAC, therefore may determine that and deposit between s1-1 to s2-1 In one way link;
After SDN controller receives the Packet-In message from s3, therefrom parses and be grouped simultaneously from the topology probe of s1 Parse s3 receive the grouping port be 1, then by topology probe be grouped in Src MAC and storage switch port MAC is compared, it can be determined that it is identical as the MAC of port 2 of s1 to go out the MAC, therefore may determine that and deposit between s1-2 to s3-1 In one way link;
After SDN controller receives the Packet-In message from s1, therefrom parses and be grouped simultaneously from the topology probe of s2 Parse s1 receive the grouping port be 1, then by topology probe be grouped in Src MAC and storage switch port MAC is compared, it can be determined that it is identical as the MAC of port 1 of s2 to go out the MAC, therefore may determine that and deposit between s2-1 to s1-1 In one way link;
After SDN controller receives the Packet-In message from s1, therefrom parses and be grouped simultaneously from the topology probe of s3 Parse s1 receive the grouping port be 2, then by topology probe be grouped in Src MAC and storage switch port MAC is compared, it can be determined that it is identical as the MAC of port 1 of s3 to go out the MAC, therefore may determine that and deposit between s3-1 to s1-2 In one way link;
After SDN controller receives the Packet-In message from s2, therefrom parses and be grouped simultaneously from the topology probe of s3 Parse s2 receive the grouping port be 2, then by topology probe be grouped in Src MAC and storage switch port MAC is compared, it can be determined that it is identical as the MAC of port 2 of s3 to go out the MAC, therefore may determine that and deposit between s3-2 to s2-2 In one way link;
After SDN controller receives the Packet-In message from s3, therefrom parses and be grouped simultaneously from the topology probe of s2 Parse s3 receive the grouping port be 2, then by topology probe be grouped in Src MAC and storage switch port MAC is compared, it can be determined that it is identical as the MAC of port 2 of s2 to go out the MAC, therefore may determine that and deposit between s2-2 to s3-2 In one way link.
So far, monocycle Topology Discovery process is completed, and the link connection mode that SDN controller obtains is as follows: s1-1 connection S2-1, s1-2 connect s3-1, and s2-2 connection s3-2, wherein each of the links are two-way link.
To sum up, relative to the topology discovery method in current SDN, method topology probe block length of the invention is shorter, Controller and control link load are lighter, and the required topology probe time is less.

Claims (7)

1. a kind of software defined network topological detecting method, which comprises the following steps:
Step 1, software defined network SDN controller and interchanger establish connection, obtain and store exchanger information, exchange generator terminal Message breath;
Step 2, SDN controller pre-install forward rule to each interchanger having connected, and wherein forward rule includes that topology is visited Survey the forwarding instruction and speed limit instruction of grouping;
An interchanger in step 3, SDN controller random selection network is the core switch as core switch A topology probe grouping is constructed, the topology probe packet cycle is sent to by Packet-Out message by the friendship later It changes planes, so that SDN controller can constantly update full mesh topology view;
Step 4, core switch are instructed according to forwarding in data according to the Packet-Out message of the SDN controller received Forwarding topology detection grouping on face;
Step 5, receive neighboring switch topology probe grouping interchanger, will be received by Packet-In message Topology probe grouping is sent to SDN controller, and is forwarded according to the forward rule of pre-installation in data surface, is forwarded to adjacent Interchanger;
Step 6, SDN controller seek topology information according to the Packet-In message of the respective switch received.
2. software defined network topological detecting method according to claim 1, which is characterized in that software described in step 1 is fixed Adopted network SDN controller and interchanger establish connection, obtain and store exchanger information, switch port information, specifically: benefit The connection that SDN controller and interchanger are established with OpenFlow agreement, specifically includes:
Step 1-1, it requests to connect with director port by Transmission Control Protocol after interchanger starting, after controller starting, controller Confirm the TCP request of interchanger, then interchanger sends OFPT_HELLO message request and establishes OpenFlow connection, and controller is received OFPT_HELLO message is returned to establish connection to interchanger after to request;
Step 1-2, OFPT_FEATURES_REQUEST message is sent to obtain exchanger information from controller to interchanger;
Step 1-3, OFPMP_PORT_DESC request message is sent to obtain switch port information from controller to interchanger;
Step 1-4, interchanger returns to OFPT_FEATURES_REPLY message to controller and OFPMP_PORT_DESC reply disappears Breath is respectively used to interchanger and believes to controller reporting exchanger information, interchanger to each port of controller reporting interchanger Breath;
Step 1-5, the OFPT_FEATURES_REPLY message and OFPMP_PORT_DESC that SDN controller is returned according to interchanger Reply message storage exchanger information and its port information.
3. software defined network topological detecting method according to claim 2, which is characterized in that exchanged described in step 1-2 Machine information includes: interchanger ID, buffer size, flow table quantity, auxiliary connection mark, statistical information support situation, recombination IP Fragment supports the anti-ring of situation and port to support situation;
Port information described in step 1-3 include: port numbers, MAC Address, behavior mark, current state, data channel feature, when Preceding rate and maximum rate.
4. software defined network topological detecting method according to claim 1, which is characterized in that the control of SDN described in step 2 Device pre-installs forward rule to each interchanger for having connected, wherein forward rule include topology probe grouping forwarding instruction and Speed limit instruction, specifically:
Step 2-1, forward rule, including following procedure are constructed:
Step 2-1-1, building forwarding instruction is to instruct interchanger to carry out the modification and forwarding of topology probe grouping, and is added to and turns In hair rule, comprising:
(1) matching domain of setting forwarding instruction is used to match the topology probe grouping for reaching interchanger, forwards the matching domain of instruction It is provided that Ethernet protocol type is topology probe protocol number, purpose physics address D st MAC is Nearest Bridge group Address, receiving port number are the corresponding port numbers in each port of interchanger;
(2) action fields of setting forwarding instruction forward the action fields of instruction to be arranged to be grouped packet header modification and packets forwarding Are as follows: the grouping is directly encapsulated into Packet-In message first and is sent to SDN switch;Later, for each exchange Generator terminal mouth, the movement in addition modification packet header, the source physical address Src MAC Address in the packet header of topology probe grouping is successively changed For the MAC Address of each port of interchanger, and modified address all needs addition to send the movement of grouping each time, for will be topological Detection grouping is sent to corresponding port;
Step 2-1-2, it is instructed according to the customized corresponding speed limit of setting of present topology detection cycle, and is added to forward rule In;
Step 2-2, the forward rule of building is issued in all interchangers having connected with SDN controller, completes pre-installation.
5. software defined network topological detecting method according to claim 4, which is characterized in that opened up described in step 2-1-1 Flutterring detection protocol number is 0x88cc.
6. software defined network topological detecting method according to claim 1 or 4, which is characterized in that SDN described in step 3 Controller selects an interchanger in network as core switch, and constructs topology probe point for the core switch Group by the packet cycle is sent to the interchanger by Packet-Out message later, specifically:
Step 3-1, a topology probe grouping is constructed for core switch, specifically: the structure of topology probe grouping includes Dst MAC, Src MAC, Ethernet protocol type and End TLV, configuration are as follows respectively: configuring Nearest for Dst MAC Bridge group address, Src MAC are configured to ' 00:00:00:00:00:00 ', and Ethernet protocol type configuration is 0x88cc, End TLV is configured to two null bytes;
Step 3-2, modification SDN controller send Packet-Out message mode with reduce controller and control link load, Specifically: it enables interchanger only send a Packet-Out message to data surface, SDN controller is sent by Packet-Out with this The quantity P of messageOUTIt is reduced to POUT=1;
Step 3-3, the topology probe grouping constructed in the content obtainment step 3-1 according to (2) in step 2-1-1 is corresponding Topology probe grouping and its forwarding instruction are encapsulated in the Packet-Out message of step 3-2, Zhi Houyou by forwarding instruction Packet-Out message cycle is sent to core switch by SDN controller, so that SDN controller can be constantly updated entirely Net topology view.
7. software defined network topological detecting method according to claim 1, which is characterized in that the control of SDN described in step 6 Device seeks topology information according to the Packet-In message of the respective switch received, specifically:
Step 6-1, SDN controller parses corresponding topology probe grouping from each Packet-In message received;
Step 6-2, it is grouped for the topology probe of each Packet-In message:
Step 6-2-1, the Src MAC information in topology probe grouping is extracted, the interchanger ID of Packet-In message is sent and is somebody's turn to do Interchanger receives the port numbers of topology probe grouping;
Step 6-2-2, the exchanger information and its port information stored according to step 1 searches port mac address and step 6-2- The identical interchanger ID of Src MAC and respective end slogan in 1, if finding match information, conclude the switch port that finds with In step 5 send Packet-In message interchanger receive the topology probe grouping port between there are physical links;
By the upper physical link, that is, topology information obtained between all interchangers.
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