WO2015027716A1

WO2015027716A1 - Status management of a port of a switch in a software-defined network

Info

Publication number: WO2015027716A1
Application number: PCT/CN2014/076427
Authority: WO
Inventors: Fang Wang; Wei Wang
Original assignee: Hangzhou H3C Technologies Co., Ltd.
Priority date: 2013-08-27
Filing date: 2014-04-29
Publication date: 2015-03-05
Also published as: CN104426693A; CN104426693B

Abstract

The present disclosure describes an example method for managing status of a port of a switch in a Software Defined Network (SDN).The SDN comprises a controller and a switch having a port. With this method,an indicator of a count of changes to the status of the port of the switch is determined.A status reporting message is, based on the indicator, selectively sent to the controller indicating the status of the port of the switch.

Description

Status management of a port of a switch in a Software-Defined Network

Background

[1] In a communication network having a Software-Defined Network (SDN) architecture, a control plane is separated from a forwarding plane. The forwarding plane does not have control functions and the control plane is implemented by an operating system independent from the forwarding plane. Characteristics of the control plane are customized based on the operating system.

[2] In the present disclosure, although in certain examples SDN is implemented based on the Openflow specification, other SDN communication specifications may be used instead of Openflow without departing from the scope of the present disclosure.

Brief Description of the Drawings

[3] Features of the present disclosure are illustrated by way of non-limiting examples, and like numerals indicate like elements, in which:

[4] Fig. 1 is a schematic diagram of an example communication network having a Software-Defined Network (SDN) architecture;

[5] Fig. 2a is a schematic diagram of an example flow table for a switch in the SDN;

[6] Figs. 2b shows schematic diagrams of example flow table items for use in the SDN;

[7] Figs. 3a and 3b are schematic diagrams of example processes for managing status of a port of the switch;

[8] Figs. 4a and 4b are schematic diagrams of example processes for updating a mode value for use in managing the status of the port; [9] Fig. 5 is a schematic diagram of an example process for managing the status of the port of the switch;

[10] Fig. 6 is a schematic diagram of an example switch in the SDN; and [11] Fig 7 is a schematic diagram of an example controller in the SDN. Detailed Description of the Invention

[12] The forwarding plane of a Software-Defined Network (SDN) comprises a switch having a port and a flow table. The switch forwards flows in the SDN according to contents of the flow table.

[13] The status of the port of the switch can be either UP or DOWN. UP means that the port operates normally to receive and send messages, while DOWN means that the port does not operate normally. Reasons why a report does not operate normally include electrical or mechanical failures, overload, etc., which may cause message loss that may reduce reliability of the SDN.

[14] The control plane of the SDN includes a controller. The controller

communicates control messages with the switch via a channel, which may be a secure channel. For example, the controller may send, via the channel, a flow table item to the switch. The flow table item is an entry for the flow table of the switch which determines how the switch forwards flows in the SDN for example by forwarding a received flow having specified characteristics through a particular port of the switch. The flow table item may be sent proactively by the controller in accordance with a policy being pushed out to some or all switches over the SDN, or sent reactively in response to a message from the switch. For example the flow table item may be sent in response to a request from the switch if the switch encounters a flow which it does not know how to forward, or the flow table item may be sent in response to the controller receiving information relating to the status of the switch or a port of the switch. For example if the port of a switch is down, then the controller may send a new flow table item to update the flow table of the switch so that messages are not forwarded out of the port which is down.

[15] The present disclosure describes an example method for managing the status of the port of the switch, in which an indicator of a count of changes to the status of the port of the switch is determined. A status reporting message is, based on the indicator, selectively sent to the controller indicating the status of the port of the switch.

Therefore, the number of the status reporting messages and flow table items communicated in the SDN may be reduced and network resources such as bandwidth, processing capacities of the switch and the controller may be saved. The example method may further prevent the flow table of the switch from being updated continuously.

[16] In the example shown in Fig. 1, the network 100 is an SDN and may for example be implemented based on the Openflow specification. The SDN 100 includes a controller 110 and switches 120, 130, 140, 150, and security channels between the controller 110 and the switches 120, 130, 140, 150.

[17] The controller 110 serves as a control centre of the SDN 100, generating flow table items and sending the flow table items to the switches 120, 130, 140, 150.

Depending on the user's configuration or protocols that operate in the SDN 100, the flow table items may be generated by a program or set statically.

[18] The switches 120, 130, 140, 150 receive the flow table items generated by the controller 110 for their respective flow tables and send messages as directed by the flow tables. An example flow table 200 for the switch 120 is shown in Fig. 2a. Each flow table item in the flow table 200 has two fields, a Medium Access Control (MAC) address field 210 and a Port field 220. The MAC address field 210 contains a destination MAC address of a message, and the Port field 220 contains a port number via which the message is sent. For example, the switch 120 receives a message that needs to be sent and the destination MAC address of the message is 00-B0-D0-86-BB- F3, which is the MAC address of the switch 130. The switch 120 searches the flow table 200 for an flow table item containing this destination MAC address 00-B0-D0-86- BB-F3 and determines the port associated with the destination MAC, which is the port 1201 in this example. The switch 120 then sends the message to the switch 130 via the port 1201.

[19] As shown in Fig. 1, each of the switches 120, 130, 140, 150 includes ports via which the switches 120, 130, 140, 150 are connected. Take the switch 120 as an example, the switch 120 include ports 1201, 1202, 1203. The switch 120 is connected with the switch 130 via the port 1201, with the switch 140 via the port 1202, and with the switch 150 via the port 1203. It should be noted that although the ports of the switches 120, 130, 140, 150 are shown as separated physical ports in Fig. 1, the ports may be logical ports that share the same hardware.

[20] In the SDN 100 shown in Fig. 1, there are security channels between the controller 110 and the switches 120, 130, 140, 150 for the controller 110 and the switches 120, 130, 140, 150 to communicate control messages. The control messages may represent a flow table item, status of a port of the switches 120, 130, 140, 150, or a mode of a port of the switches 120, 130, 140, 150.

[21] In the present disclosure, a port of a switch may be in one of two modes: a non-suppress mode and a suppress mode.

[22] In the non-suppress mode, each time there is a change to the status of the port of the switch, for example from UP to DOWN or from DOWN to UP, a status reporting message is sent, via the security channel, from the switch to the controller 110 reporting the status of the port. Upon receipt of the status reporting message, the controller 110 takes corresponding actions. For example, the controller 110 may generate a flow table item for the port and then sends to the switch the flow table item. If the status of the port changes to DOWN, the flow table item may disable the port. On the other hand, if the status of the port changes to UP, the flow table item may enable the disabled port. In other examples, the controller 110 may simply ignore the status reporting message. In the context of this disclosure "disable the port" means to not forward flows through the port; for example this may be achieved by updating a flow table of the switch so that a flow is not forwarded through the port. In the context of this disclose "enable the port" means to enable the port to forward flows, for example this may be achieved by updating a flow table of the switch so that a flow is forwarded through the port.

[23] In the suppress-mode, the switch suppresses sending the status reporting message to the controller 110. As a result, the number of the status reporting messages and flow table items communicated in the SDN 100 may be reduced and network resources such as bandwidth, processing capacities of the switch and the controller 110 may be saved. Further, the suppress-mode may prevent the flow table of the switch being updated continuously when the status of the port constantly changes between UP and DOWN.

[24] The switch side

[25] Figs. 3a and 3b show example processes 300, 301 for managing the status of a port of a switch. It should be noted that although the examples are described with reference to the switch 120, the examples are also applicable to other switches 130, 140, 150 in the SDN 100 without departing from the scope of the present disclosure. In the context used herein the term "switch" includes layer 2 switches, layer 3 switches and routers etc.

[26] The switch 120 monitors changes to the status of a port, for example the port 1202. A status change in this example includes a change to the status of the port from UP to DOWN or a change from DOWN to UP. In other examples, the status change may only include a change from UP to DOWN.

[27] In Fig. 3a, with the monitoring of status changes, the switch 120 determines 310 an indicator of a count of changes to the status of the port 1202. In this example, the indicator is a mode value based on the number of the changes to the status of the port 1202 indicating the mode of the port 1202. [28] When there is a change to the status of the port 1202, the switch 120 then selectively sends 320, based on the indicator, to the controller a status reporting message indicating the status of the port 1202. Particularly, if the indicator indicates that the port 1202 is in the non-suppress mode, the switch 120 sends the status reporting message to the controller 110. Otherwise, if the port 1202 is in supress mode the switch 120 suppresses sending the status reporting message to the controller 110. This way the switch 120 does not always send the status reporting message to the controller 110 if the status of the port 1202 changes frequently.

[29] In Fig. 3b, to determine the indicator, particularly, the mode value for the port 1202, the switch 120 counts 330 the number of changes to the status of port 1202 as the mode value at this point in time. Counting may be a straight forward increasing the mode value by one for each individual change, or any other suitable calculation can be used provided it adjusts the mode value to take account of each change.

[30] Where there is a change to the status of the port 1202, the switch 120 checks 340 if the mode value has reached a threshold suppress limit. If the mode value is less than the suppress limit 350, it is determined 350 that the port 1202 is in the non- suppress mode and the status reporting message is sent 360 to the controller 110. On the other hand, if the mode value is equal to or greater than the suppress limit, it is determined 370 that the port 1202 is in the suppress mode and the sending of the status reporting message to the controller 110 is suppressed 380.

[31] The threshold suppress limit in this example is predetermined and static. In other examples the suppress limit may be dynamic such that it adjusts based on conditions on the network 100. In this example, comparison to a threshold is simple number comparison to see if it the mode value is larger or smaller than the suppress limit. In other examples, the comparison may include further calculations in comparing the mode value to the threshold, such as taking into account the recent history of the mode value. [32] Fig. 4a shows an example process 400 for updating the mode value for the port 1202 when the port 1202 is in the non-suppress mode.

[33] In Fig. 4a, where there is a change to the status of the port 1202, as the port 1202 is currently in the non-suppress mode, the switch 120 sends 410 the status reporting message to the controller 110 indicating the status of the port 120 to the controller 110. Further, the mode value for the port 1202 is increased 420 by one. If the mode value is greater than the suppress limit, meaning the change to the status of the port 1202 causes a change to the mode of the port 1202 from the non-suppress mode to the suppress mode, the switch 120 sends 430 to the controller 110 a first mode reporting message indicating that the mode of the port 1202 changes from the non- suppress mode to the suppress mode and the switch 120 no longer sends the status reporting message for the port 1202 to the controller 110 when there are further changes to the status of the port 1202.

[34] Fig. 4b shows an example process 401 for updating the mode value for the port 1202 when the port 1202 is currently in the suppress mode.

[35] In Fig. 4b, once the change to the status of the port 1202 causes the change to the mode of the port 1202, particularly, the mode of the port 1202 changes from the non-suppress mode to the suppress mode, the switch 120 suppresses 440 sending the status reporting message to the controller 110. Then the switch 120 reduces 450 the mode value over a predetermined time referred to here as the maximum suppress time using an attenuation algorithm. If the mode value is reduced to a level less than a reuse limit within the maximum suppress time, the mode of the port 1202 changes from the suppress mode to the non-suppress mode. In this case, the switch 120 sends 460 a second mode reporting message to the controller 120 indicating that the port 1202 changes from the suppress mode to the non-suppress mode. As a result, the status of the port 1202 is managed in accordance with the process described with reference to Fig. 4a. Simultaneously, during the maximum suppress time, where there is a change to the status of the port 1202, the mode value is increased by one. [36] An example attenuation algorithm is described below.

[37] In the attenuation algorithm, the mode value is reduced by half periodically. Specifically, after each attenuation period, the mode value is reduced to its half. The attenuation algorithm can be expressed by the equation below:

wherein Ns is the mode value after one second, T is the attenuation period, Nq is the mode value 1 second ago.

[38] If the status of the port 1202 changes so frequently during the maximum suppress time that the increasing of the mode value exceeds the reducing of the mode value by the attenuation algorithm, the mode value constantly increases during the maximum suppress time. In such case, if the mode value reaches a maximum mode value, then the mode value is set to the maximum mode value without being further increased.

[39] If the attenuation algorithm fails to reduce the mode value for the port 1202 to the level less than the reuse limit after the maximum suppress time, in other words, the port 1202 stays in the suppress mode for a period of time longer than the maximum suppress time, the attention algorithm continues to apply to the mode value until the mode value is less than the reuse limit in order for the port 1202 to change from the suppress mode to the non-suppress mode. Nevertheless in this case, the mode value is not increased even if there is a change to the status of the port 1202 to make sure that the mode value is eventually less than the reuse limit.

[40] In another example, in order to ensure the mode value reaches the reuse limit within the maximum suppress time, the maximum mode value, the maximum suppress time, the attenuation period and the reuse limit are set to satisfy the following equation:

(2) wherein C is the maximum mode value, T is the maximum suppress time, D is the attenuation period and R is the reuse limit.

[41] It should be noted that whether the mode value becomes less than the reuse limit during or after the maximum suppress time, which leads to the change to the mode of the port 1202 from the suppress mode to the non-suppress mode, the switch 120 sends the second mode reporting message to the controller 110. In this example, the switch 120 further sends a status reporting message to the controller 110 indicating the status of the port 1202. In another example, the switch 120 first checks the status of the port 1202. If the status of the port 1202 is UP, the switch 120 sends the status reporting message to the controller 110; if the status of the port 1202 is DOWN, the switch 120 does not send the status reporting message until the status of the port 1202 changes to UP and the port 1202 is still in the non-suppress mode.

[42] The controller side

[43] Fig. 5 shows an example process 500 for managing the status of a port of a switch in the SDN 100.

[44] As described above with reference to Fig. 4a, the switch 120 sends the first mode reporting message to the controller 110 indicating that the mode of the port 1202 changes from the non-suppress mode to the suppress mode.

[45] Upon receipt 510 of the first mode reporting message at the controller 110, the controller 110 is aware of the fact that the port 1202 of the switch 120 changes from the non-suppress mode to the suppress mode and the switch 120 no longer sends a status reporting message to indicate a further change to the status of the port 1202. In this case, the controller 110 generates a first flow table item 201 for the switch 120, as shown in Fig. 2b, and sends 520 the first flow table item 201 to the switch 120.

[46] The first flow table item 201 for the switch 120 associates a backup port, which is the port 1203 of the switch 120 in this example, with the MAC address (i.e., 00-B0-D0-86-BB-F4) of the switch 140, enabling the backup port 1203 to send messages that are destined to the switch 140 and disabling the port 1202 of the switch 120. Specifically, upon receipt of the first flow table item 201 at the switch 120, the switch 120 updates the flow table 200 shown in Fig. 2a with the first table item 201 sent from the controller 110 and deletes the flow table item associating the MAC address with the port 1202 from the flow table, which is the second item for the flow table 200.

[47] As can be seen from the first flow table item 201, the messages to the switch 140 are no longer sent to the switch 140 via the port 1202; instead, the messages are sent via the backup port 1203 to a backup switch, which is the switch 150 in this example. It should be noted that the switch 150 is not the destination of the messages to the switch 140. In order to send the messages to the switch 140, the controller 110 further sends a second flow table item 202 to the switch 150 as shown in Fig. 2b. The second flow table item 202 indicates that the messages that are destined to the switch 140 are sent via the port 1502 to the switch 140. This way the messages to the switch 140 at the switch 120 are first sent from the switch 120 to the switch 150 via the backup port 1203, and then are sent from the backup switch 150 to the switch 140 via the port 1502. As a result, message loss may be prevented and the reliability of the SDN 100 may be improved in the event that the port 1202 of the switch 120 is in the suppress mode.

[48] On the other hand, as described above with reference to Fig. 4b, the switch 120 sends the second mode reporting message to the controller 110 indicating that the mode of the port 1202 changes from the suppress mode to the non-suppress mode.

[49] Upon receipt 530 of the second mode reporting message at the controller 110, the controller 110 is aware of the fact that the port 1202 of the switch 120 changes from the suppress mode to the non-suppress mode and the switch 120 will send a status reporting message to indicate a further change to the status of the port 1202. In this case, the controller 110 generates a third flow table item 203 for the switch 120, as shown in Fig. 2b, and sends 540 the third flow table item 203 to the switch 120. [50] As can be seen from Fig. 2b, the third flow table item 203 for the switch 120 disables the backup port 1203 and enables the port 1202 to send messages that are destined to the switch 140 having the MAC address of 00-B0-D0-86-BB-F4.

Specifically, upon receipt of the third flow table item 203 at the switch 120, the switch 120 updates the flow table 200 with the third flow table item 203 sent from the controller 110 and deletes the first flow table item 201 associating the MAC address with the port 1203 from the flow table 200. This way the port 1202 of the switch 120 is reused to send messages to the switch 140.

[51] In another example, upon receipt of the second mode reporting message, the controller 110 checks the status of the port 1202 by for example receiving a status reporting sent from the switch 120. If the status of the port 1202 is UP, the controller 110 sends the third flow table item 203 to the switch 120. If the status of the port 1202 is DOWN, the controller 110 does not send the third flow table item 203 to the switch 120 so as to keep the current flow table.

[52] The controller 110 further sends an instruction to the switch 150 to delete the second flow table item 202 from the flow table for the switch 150. In another example, the controller 110 may not send the instruction to the switch 150 to delete the second flow table item 202 as the second flow table item 202 for the switch 150 may expires and be deleted automatically.

[53] The above examples can be implemented by hardware, software or firmware or a combination thereof.

[54] Example switch 600

[55] Referring to Fig. 6, an example switch 600 includes a processor 610, a memory 620 and a network interface device 640 that communicate with each other via a bus 630, fabric or other medium. The switch 600 also includes a port 650 through which the switch 600 forwards flows in the SDN. The status of the port 650 includes UP and DOWN. The memory 620 stores instructions and data for the processes described with reference to Figs. 3a to 4b, and the processor 610 performs the instructions from the memory 620 to implement the processes.

[56] The processor 610 performs the instructions from the memory 620 unit to count the number of changes to the status of the port 650 to determine an indicator; and determine, based on indicator, whether to send to the controller 110 a status reporting message indicating the status of the port 650.

[57] In the above example, the memory 620 may further store data, for example the flow table 200 shown in Fig. 2a, the suppress limit, the reuse limit, the maximum mode value, the maximum suppress time, the attenuation period, etc.

[58] Example controller 700

[59] Referring to Fig. 7, an example controller 700 includes a processor 710, a memory 720 and a network interface device 740 that communicate with each other via a bus 730. The memory 720 stores instructions and data for the processes described with reference to Fig. 5, and the processor 710 performs the instructions from the memory 720 to implement the processes.

[60] In one example, the controller device 700 is capable of acting as the controller 110, a part of the controller 110 or a network entity that is separate from the controller 110 to manage the status of the port 1202 of the switch 120. In this case, the processor 710 perform the instructions from the memory 720 unit to receive a mode reporting message indicating the mode of the port 1202 of the switch 120, the mode of the port 1202 being indicative of the sending of the status reporting message to the controller 110 being suppressed; and send a first flow table item 201 to the switch 120 to disable the port 1202 of the switch 120 and enable a different port 1203 of the switch 120.

[61] The switch 600 and controller 700 may also be implemented as a device comprising function units (not shown in Fig. 6 for simplicity).

[62] In one example, the switch 600 comprises a detecting unit, a determining unit, a transceiving unit and a processing unit.

[63] The detecting unit detects whether the status of the port 1202 has changed.

[64] The determining unit determines the mode of the port 1202 when the detecting unit detects a change to the status of the port 1202.

[65] The transceiving unit sends to the controller 110 a status reporting message indicating the status of the port 1202 if the determining unit determines that the mode of the port 1202 is the non-suppress mode. The transceiving unit further suppresses sending to the controller 110 the status reporting message indicating the status of the port 1202 if it is determined that the mode of the port 1202 changes from the non- suppress mode to the suppress mode.

[66] The status of the port 1202 includes UP and DOWN. The mode of the port 1202 includes the non-suppress mode and the suppress mode. The mode of the port 1202 is determined based on the number of changes to the status of the port 1202.

[67] The transceiving unit further sends to the controller 110 a first mode reporting message indicating that the mode of the port 1202 changes from the non-suppress mode to the suppress mode when the determining unit determines that the mode of the port 1202 changes from the non-suppress mode to the suppress mode.

[68] The transceiving unit also receives a first flow table item 201 sent from the controller 110, as described with reference to Fig. 2b. The first flow table item 201 is sent from the controller 110 when the first mode reporting message indicates to the controller 110 that the mode of the port 1202 changes from the non- suppress mode to the suppress mode.

[69] The processing unit, upon receipt of the first flow table item 201 by the transceiving unit, deletes the original flow table item associated with the port 1202 and updates the flow table 200 with the first flow table item 201. This way the messages of the port 1202 can be sent to a backup switch 150 via a backup port 1203, as described above.

[70] The backup switch 150 further receives a second flow table item 202 sent from the controller 110, as described with reference to Fig. 2b, which enables the backup device 150 to send the messages sent from the backup port 1203 of the switch 120 to the destination switch 140 of the messages according to the second flow table item 202. As described above, the second flow table item 202 for the backup switch 150 is sent from the controller 110 when the first mode reporting message indicates to the controller 110 that the mode of the port 1202 changes from the non- suppress mode to the suppress mode.

[71] In one example, the controller 700 comprises a receiving unit and a processing unit.

[72] The receiving unit receives the first mode reporting message.

[73] The processing unit, upon receipt of the first mode reporting message by receiving unit, sends the first flow table item 201 to the switch 120. The first mode reporting message indicates to the controller 110 that the mode of the port 1202 changes from the non-suppress mode to the suppress mode. The first flow table item 201, as described with reference to Fig. 2b, enables the switch 120 to delete the original flow table item associated with the port 1202 and to send the messages of the port 1202 to the backup switch 150 via the backup port 1203. The controller 110 further sends the second flow table item 202 to the backup switch 150 to enable the backup switch 150 to send the messages sent from the switch via the backup port 1203 to the destination switch 140 of the messages, as described with reference to Fig. 2b.

[74] As described above, the status of the port 1202 includes UP and DOWN, and the mode of the port 1202 includes the non-suppress mode and the suppress mode. The mode of the port 1202 is determined based on the number of changes to the status of the port.

[75] Further, the processes, methods and functional units described in this disclosure may be implemented by hardware or by software. For example a plurality of machine readable instructions stored on a non-transitory storage medium and executable by a processor to implement the methods and functional units recited in the examples of the present disclosure. There may be a single processor and non-transitory storage medium or plural processors and/or storage mediums in which case the methods and functional units may be distributed between them.

[76] The figures are only illustrations of an example, wherein the units or procedure shown in the figures are not necessarily essential for implementing the present disclosure. The units in the devices in the examples can be arranged as described, or can be located in one or more devices differently than shown in the examples. For example, the units in the examples described can be combined into one module or further divided into a plurality of sub-units.

[77] Although the flow charts described show a specific order of execution, the order of execution may differ from that which is depicted. For example, the order of execution of two or more blocks may be changed relative to the order shown. Also, two or more blocks shown in succession may be executed concurrently or with partial concurrence. All such variations are within the scope of the present disclosure.

Claims

1. A method for managing status of a port of a switch in a Software-Defined Network (SDN) having a controller, comprising: determining an indicator of a count of changes to the status of the port of the switch; and selectively sending, based on the indicator, to the controller a first message indicating the status of the port of the switch.

2. The method according to claim 1, wherein the indicator is a value based on the number of the changes to the status of the port of the switch, and the indicator indicates a mode of the port of the switch, the mode indicates whether the first message is sent to the controller or not.

3. The method according to claim 2, wherein selectively sending the first message comprises sending the first message to the controller if the mode of the port of the switch is indicative of the first message being sent to the controller, and suppressing sending the first message to the controller if the mode is indicative of the first message not being sent to the controller.

4. The method according to claim 2, wherein the mode is indicative of the first message being sent to the controller if the value is less than a first threshold, and the mode is indicative of the first message not being sent to the controller if the value is greater than the first threshold.

5. The method according to claim 2, further comprising: selectively sending, based on the value, to the controller a second message indicating the mode of the port of the switch.

6. The method according to claim 5, further comprising: receiving, at the controller, the second message indicating the mode is indicative of the first message not being sent to the controller; and sending a third message to the switch to disable the port of the switch and enable a different port of the switch.

7. The method according to claim 6, further comprising: sending a fourth message to the switch to enable the port of the switch and disable the different port of the switch.

8. A switch for use in a software defined network (SDN) having a controller, comprising: a port having a status; a memory unit to store instructions; and a processor to perform the instructions from the memory unit to count the number of changes to the status of the port to determine an indicator; and determine, based on indicator, whether to send to the controller a first message indicating the status of the port.

9. The switch according to claim 8, wherein the indicator is a value that indicates a mode of the port, the mode indicates whether the first message is sent to the controller or not.

10. The switch according to claim 9, the processor further performs the instructions from the memory unit to send the first message to the controller if the mode of the port is indicative of the first message being sent to the controller, and to suppress sending the first message to the controller if the mode is indicative of the first message not being sent to the controller.

11. The switch according to claim 9, wherein the mode is indicative of the first message being sent to the controller if the value is less than a first threshold, and the mode is indicative of the first message not being sent to the controller if the value is greater than the first threshold.

12. The switch according to claim 8, the processor further performs the instructions from the memory unit to selectively send, based on the value, to the controller a second message indicating the mode of the port.

13. A controller for managing status of a port of a switch in a software defined network (SDN), comprising: a memory unit to store instructions; and a processor to perform the instructions from the memory unit to receive a first message indicating a mode of the port of the switch, the mode being indicative of the status of the port of the switch not being sent to the controller; and send a second message to the switch to disable the port of the switch and enable a different port of the switch.

14. The controller according to claim 13, the processor further performs the instructions from the memory unit to send a third message to the switch to enable the port of the switch and disable the different port of the switch.