CN104410730B - SDN active and standby controller seamless handover methods based on NAT technologies - Google Patents

Abstract

The invention provides a method for seamless switching of SDN active and standby controllers based on NAT technology. The data format of the control channel between the SDN active and standby controllers includes an active message, an election message and a synchronization message; the active report of the SDN controller The election message and the election message adopt the same message format; the synchronization of the SDN controller is divided into real-time synchronization and periodical synchronization; the router must be configured with a NAT table to establish a one-to-many mapping relationship between the virtual address and the actual IP address of the controller, and the SDN switch and the virtual Address to establish a TCP connection; define the processing behavior of the backup controller for Openflow messages. The NAT technology-based SDN active/standby controller seamless switching method of the present invention adopts a technology similar to NAT TCP load balancing to realize a unique cluster virtual address, even if the active/standby controller switches, the unique cluster virtual address will not change. The switch does not need to sense the switching of the active and standby controllers, so as to realize the seamless and fast switching of the active and standby controllers.

Description

SDN active and standby controller seamless switching method based on NAT technology

technical field

The present invention relates to the technical field of network communication, in particular to a method for seamlessly switching active and standby controllers of SDN (Software Defined Network, Software Defined Network) based on NAT (Network Address Translation, Network Address Translation) technology.

Background technique

At present, the competition among major manufacturers in the SDN market is more about the competition for the right to define and control the controller. The controller is the core of the SDN network. In a large-scale IDC (Internet Data Center, Internet Data Center) network, there is a high requirement for the reliability of the controller.

In the prior art, the east-west interface of the SDN controller is not standardized, and each vendor has its own proprietary extension. Some manufacturers adopt the technology of single SDN controller. Logically centralized controllers are not immune to single points of failure. Once the controller fails and there is no backup controller to replace it, the entire SDN network will be in an unmanageable and controllable state. This is fatal to operators and users.

In addition, many manufacturers adopt the technology of active and standby controllers. However, the IP addresses of the active and standby controllers are different, so smooth and seamless switchover cannot be achieved. Once the main controller fails, the SDN switch needs to re-establish a TCP connection with the backup controller, which will result in loss of control data and affect basic services, resulting in poor user experience. .

Therefore, it is very important and necessary to quickly realize the switchover of the active and standby controllers.

Contents of the invention

In view of the above-mentioned shortcoming of prior art, the object of the present invention is to provide a kind of SDN active-standby controller seamless switching method based on NAT technology, adopt the technology similar to NAT TCP load balancing to realize unique cluster virtual address, even master-standby When the controller is switched, the unique virtual address of the cluster will not change. Since the switch establishes a TCP connection with the controller cluster through the unique virtual address of the cluster, the switch does not need to perceive the switching of the active and standby controllers, so as to realize the active and standby controllers Seamless and fast switching.

In order to achieve the above purpose and other related purposes, the present invention provides a method for seamless switching of SDN active and standby controllers based on NAT technology. The data format of the control channel between the SDN active and standby controllers includes active messages, election messages and synchronization message; the active message of the SDN controller and the election message adopt the same message format; the synchronization of the SDN controller is divided into real-time synchronization and periodic synchronization; the real-time synchronization is incremental synchronization, and the periodic synchronization is the whole database Synchronization; the router must configure the NAT table, establish a one-to-many mapping relationship between the virtual address and the actual IP address of the controller, and the SDN switch establishes a TCP connection with the virtual address; define the processing behavior of the backup controller for Openflow messages.

According to the above-mentioned SDN active/standby controller seamless switching method based on NAT technology, wherein: the active message is bidirectional, used to confirm the connection and measurement connection delay with the other party; the election message is bidirectional, It is used to carry the IP address information of the sender; the synchronization message is sent from the master controller to the backup controller, and is used to update the database content of the backup controller when the database of the master controller changes.

According to the above-mentioned method for seamless switching of SDN active and standby controllers based on NAT technology, wherein: the formats of the activation message and the election message of the SDN controller include two fields of serial number and IP address, with a total of 32 bits.

Further, according to the above-mentioned method for seamless switching of SDN active/standby controllers based on NAT technology, wherein: the serial number is 16bits, and the initial value is 1, and if the value of the serial number exceeds 65535, it will restart from 1 Start calculation; the IP address field records the node IP of the controller, which is used for the election of the master controller.

According to the above-mentioned method for seamless switching of SDN active and standby controllers based on NAT technology, wherein: the flow of SDN controller activity and election includes the following steps:

Step S21, the active packet timer expires;

Step S22, judging whether a response is received; if yes, proceed to step S23; if not, proceed to step S27;

Step S23, adding 1 to the serial number of the response message, sending it to the opposite end, and comparing the opposite end IP address and the local IP address;

Step S24, judging whether the peer IP address is smaller than the local IP address, if so, proceed to step S25; if not, proceed to step S26;

Step S25, judging whether the local controller is the master controller, if so, the local working mode is changed to the backup controller, and the process ends; if not, no operation is performed, and the process ends;

Step S26, judging whether the local controller is a backup controller, if so, the local working mode is changed to the master controller, and the process ends; if not, no operation is performed, and the process ends;

Step S27. Determine whether the number of retransmissions is greater than the threshold of retransmissions. If yes, the local working mode is set to the master controller, and the process ends;

According to the above NAT technology-based SDN active/standby controller seamless switching method, wherein: the factors generated by the real-time synchronization include statistical information changes, orchestrator changes, northbound application changes and OF message changes.

According to the above-mentioned method for seamless switching of SDN active and standby controllers based on NAT technology, wherein: in the SDN controller synchronization message processing flow, after the main controller database receives the real-time synchronization and periodic synchronization requests, it sends a synchronization request to the backup controller database. message so that the two are consistent.

According to the above-mentioned method for seamless switching of SDN active and standby controllers based on NAT technology, wherein: when the router forwards the OF message of the switch to all controllers, it replaces the virtual destination IP address with the actual controller IP address; When forwarding the OF message of the controller to the switch, replace the actual controller IP with the virtual source IP address.

According to the above-mentioned method for seamless switching of SDN active and standby controllers based on NAT technology, only the active controller will send out OF messages.

As mentioned above, the NAT technology-based SDN active/standby controller seamless switching method of the present invention has the following beneficial effects:

(1) Combined with NAT technology, the mechanism of real-time and regular synchronization of the active and standby controller databases is adopted. When the active controller fails, such as power failure, system abnormality, etc., the active The seamless switching of the standby controller greatly improves the robustness of the controller;

(2) Since the backup controller can synchronize the data of the master controller in real time, there is no need to export data to the backup controller when the master controller fails;

(3) Use a technology similar to NAT TCP load balancing to realize the unique cluster virtual address. Even if the main controller is switched, the unique cluster virtual address will not change, because the switch is established through the unique cluster virtual address and the controller cluster. TCP connection, so the switch does not need to sense the switching of the active and standby controllers.

Description of drawings

Fig. 1 is shown as the active message of SDN controller of the present invention and the schematic format diagram of election message;

Fig. 2 is shown as the flowchart of SDN controller activity and election of the present invention;

Fig. 3 is shown as the flowchart of SDN controller synchronous message processing of the present invention;

Fig. 4 is shown as the flow chart of SDN controller OF message receiving process of the present invention;

Fig. 5 is shown as the flow chart of SDN controller OF message sending process of the present invention;

FIG. 6 is a schematic diagram of a simulation test environment for SDN active/standby controller switchover based on NAT technology in the present invention.

Detailed ways

Embodiments of the present invention are described below through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation modes, and various modifications or changes can be made to the details in this specification based on different viewpoints and applications without departing from the spirit of the present invention.

It should be noted that the diagrams provided in this embodiment are only schematically illustrating the basic idea of the present invention, and only the components related to the present invention are shown in the diagrams rather than the number, shape and shape of the components in actual implementation. Dimensional drawing, the type, quantity and proportion of each component can be changed arbitrarily during actual implementation, and the component layout type may also be more complicated.

The SDN active/standby controller seamless switching method based on NAT technology of the present invention comprises the following contents:

(1) The data format of the control channel between the SDN active and standby controllers includes active messages, election messages and synchronization messages. Among them, the active message confirms that there is no problem with the connection with the other party by sending an echo (echo) and getting a response (reply), and can also be used to measure the connection delay. The election message carries the IP address information of the sender.

The definitions of various data formats are shown in Table 1 below.

Table 1. Data format definition table of the control channel between the SDN active and standby controllers

(2) The activation message and the election message of the SDN controller adopt the same message format. The format of the activity message and election message of the SDN controller is shown in Figure 1, including two fields of serial number and IP address, with a total of 32 bits. Among them, the serial number is 16bits, and the starting value is 1. If the value exceeds 65535, it will be calculated from 1 again. The IP address field records the node IP of the controller, which is used for the election of the master controller.

The liveness detection of the SDN controller supports the timeout retransmission mechanism. The default value of the number of retransmissions is 3, and the default value of the timeout is 1 second. Users can modify the number of retransmissions and timeout according to the actual situation. In the SDN control cluster, the active controller with the smallest IP address will become the master controller.

As shown in Figure 2, the flow process of SDN controller activity and election of the present invention comprises the following steps:

Step S21, active message timer overtime (timeout default value is 1s);

Step S22, judging whether a response is received; if yes, proceed to step S23; if not, proceed to step S27;

Step S23, adding 1 to the sequence number of the response (echo) message, sending it to the opposite end, comparing the opposite end IP address and the local IP address;

Step S24, judging whether the peer IP address is smaller than the local IP address, if so, proceed to step S25; if not, proceed to step S26;

Step S25, judging whether the local controller is the master controller, if so, the local working mode is changed to the backup controller, and the process ends; if not, no operation is performed, and the process ends;

Step S26, judging whether the local controller is a backup controller, if so, the local working mode is changed to the master controller, and the process ends; if not, no operation is performed, and the process ends;

Step S27, determine whether the number of retransmissions is greater than the threshold of retransmissions (such as the default value 3), if so, the local operating mode is set to the master controller, and the process ends; if not, the serial number of the echo message remains unchanged, and the sending peer, The process ends.

(3) The synchronization of the SDN controller is divided into real-time synchronization and periodic synchronization. Real-time synchronization is incremental synchronization, and periodic synchronization is the synchronization of the entire database.

Among them, the following four factors cause real-time synchronization: changes in statistical information, changes in the orchestrator, changes in northbound applications, and changes in OF messages. Referring to FIG. 3 , in the SDN controller synchronization message processing flow, after receiving the real-time synchronization and periodic synchronization requests, the main controller database sends a synchronization message to the backup controller database to make the two consistent.

(4) The router must be configured with a NAT table to establish a one-to-many mapping relationship between the virtual address and the actual IP address of the controller. The SDN switch establishes a TCP connection with the virtual address without knowing the actual IP address of the controller.

Wherein, the format and sample of the NAT table are shown in Table 3 below.

Table 3, NAT table

In order to ensure the consistency of the database, both the active and standby controllers need to process the OF message sent by the switch. It should be noted that the router needs to forward the OF message of the switch to all controllers, and replace the virtual destination IP address with the actual controller IP address. Similarly, the router also needs to forward the controller's OF message to the switch, and replace the actual controller IP with the virtual source IP address.

With reference to Fig. 4, the flow process of SDN controller OF message receiving process of the present invention comprises the following steps:

Step S41 , the router must configure a NAT table, and establish a one-to-many mapping relationship between the virtual address and the actual IP address of the controller.

Step S42, the switch establishes a TCP connection with the unique cluster virtual address.

Step S43, the router receives the OF message from the switch, and uses the destination IP to query the NAT table.

Step S44, determine whether the controller IP matches the destination IP; if so, replace the virtual IP with the matched controller IP to send the OF message to the corresponding controller, and the controller processes the OF message and proceeds to step S45; if not, proceeds to step S45 Enter step S45.

Step S45, judging whether the matching of the destination IP is finished, if yes, the process ends; if not, go to step S43.

With reference to Fig. 5, the flow process of SDN controller OF message sending process of the present invention comprises the following steps:

Step S51 , the router must configure a NAT table, and establish a one-to-many mapping relationship between the virtual address and the actual IP address of the controller.

Step S52, the switch establishes a TCP connection with the unique cluster virtual address.

Step S53, the router receives the OF message from the controller, and uses the source IP to query the NAT table.

Step S54, determine whether the source IP matches the virtual IP, if so, replace the source IP with the matching virtual IP and send the OF message to the corresponding switch, the switch processes the OF message and generates a flow table, and then proceeds to step S55; if not, proceeds to Enter step S55.

Step S55, judging whether the matching of the source IP is finished, if yes, the process ends; if not, go to step S53.

It should be noted that only the master controller will send OF messages to the outside world.

(5) Define the processing behavior of the backup controller for Openflow messages, as shown in Table 2 below.

Table 2. Backup controller OF message processing table

As shown in Figure 6, when carrying out SDN active/standby controller switching test in the SDN active/standby controller switching simulation test environment based on NAT technology of the present invention, comprise the following steps:

A. Build the simulation test environment as shown in Figure 6;

B. The controller 1 is powered off;

C. Ensure that the SDN forwarding plane works normally;

D. The user manages the SDN network through the controller 2, such as modifying and deleting the previous flow table data through the controller 2.

Through the above tests, the technical effect of seamless and rapid switching of the active and standby controllers can be achieved without the switch being aware of the switching of the active and standby controllers.

In summary, the NAT technology-based SDN master-standby controller seamless switching method of the present invention combines NAT technology, and adopts a mechanism of real-time and regular synchronization of the master-standby controller database. When the master controller fails, for example, the Power, system abnormalities, etc., can achieve seamless switching between the active and standby controllers without the switch being aware, which greatly improves the robustness of the controller; because the backup controller can synchronize the data of the main controller in real time, When the main controller fails, there is no need to export data to the backup controller; the unique virtual address of the cluster is realized by using a technology similar to NAT TCP load balancing. Even if the main controller is switched, the unique virtual address of the cluster will not change, because The switch establishes a TCP connection with the controller cluster through the unique cluster virtual address, so the switch does not need to be aware of the active/standby switchover of the controller. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial application value.

The above-mentioned embodiments only illustrate the principles and effects of the present invention, but are not intended to limit the present invention. Anyone skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical ideas disclosed in the present invention should still be covered by the claims of the present invention.

Claims (8)

1. A kind of 1. SDN active and standby controller seamless handover methods based on NAT technologies, it is characterised in that：Including herein below：

   The data format of control passage includes active message, EB packet and sync message between SDN active and standby controllers；

   The active message and EB packet of SDN controllers use same message format；

   SDN controllers are synchronously divided into real-time synchronization and cycle synchronisation；The real-time synchronization is increment synchronization, the cycle synchronisation It is the synchronization of full database；

   Router must configure NAT table, establish virtual address and exchanged to the one-to-many mapping relations of controller real ip address, SDN Machine is established TCP with virtual address and connected；

   When the OF message of interchanger is forwarded to all controllers by router, replaced virtually with the controller IP address of reality Purpose IP address；When the OF message of controller is forwarded to interchanger by router, actual control is replaced with virtual source IP address Device IP processed；

   Define processing behavior of the backup controller to Openflow message；

   Processing behavior of the backup controller to Openflow message is defined according to following table：
2. 2. the SDN active and standby controller seamless handover methods according to claim 1 based on NAT technologies, it is characterised in that：Institute Active message is stated to be two-way, for confirming connection and measurement connection delay with other side；The EB packet is two-way, is used In the IP address information for carrying sender；The sync message is sent to backup controller by master controller, when master controller When database changes, for updating the data-base content of backup controller.
3. 3. the SDN active and standby controller seamless handover methods according to claim 1 based on NAT technologies, it is characterised in that：Institute Stating the form of the active message and EB packet of SDN controllers includes two fields of sequence number and IP address, common 32bits.
4. 4. the SDN active and standby controller seamless handover methods according to claim 3 based on NAT technologies, it is characterised in that：Institute State Serial No. 16bits, initial value 1, when the value of the sequence number is if it exceeds 65535, will be calculated again since 1；Institute The node IP of IP address field recording controller is stated, the election for master controller.
5. 5. the SDN active and standby controller seamless handover methods according to claim 1 based on NAT technologies, it is characterised in that： SDN controllers activity and the flow of election comprise the following steps：

   Step S21, active message timer expiry；

   Step S22, judge whether to receive response；If so, it is transferred to step S23；If it is not, it is transferred to step S27；

   Step S23, by the sequence number of response message cumulative 1, opposite end is sent, compares peer IP address and local ip address；

   Step S24, judge whether peer IP address is less than local ip address, if so, being transferred to step S25；If it is not, it is transferred to step S26；

   Step S25, judge whether local controller is master controller, if so, local mode of operation is changed to backup controller, flow Terminate；If it is not, not performing any operation, flow terminates；

   Step S26, judge whether local controller is backup controller, if so, local mode of operation is changed to master controller, flow Terminate；If it is not, not performing any operation, flow terminates；

   Step S27, judge whether number of retransmissions is more than number of retransmissions threshold value, if so, local mode of operation is set to master controller, stream Journey terminates；If it is not, the sequence number of response message is constant, opposite end is sent, flow terminates.
6. 6. the SDN active and standby controller seamless handover methods according to claim 1 based on NAT technologies, it is characterised in that：Institute Stating factor caused by real-time synchronization includes statistical information change, composer change, north orientation application change and the change of OF message.
7. 7. the SDN active and standby controller seamless handover methods according to claim 1 based on NAT technologies, it is characterised in that： In SDN controller sync message handling processes, after master controller database receives real-time synchronization and cycle synchronisation request, Xiang Bei Part controller database sends sync message, to cause the two to be consistent.
8. 8. the SDN active and standby controller seamless handover methods according to claim 1 based on NAT technologies, it is characterised in that：Only There is master controller just can be to outgoing OF message.