State Synchronization Between a Controller and a Switch in a Communications Network

Patent metadata

Field	Value
Publication number	US-2018351802-A1
Application number	US-201515771974-A
Country	US
Kind code	A1
Filing date	Nov 9, 2015
Priority date	Nov 9, 2015
Publication date	Dec 6, 2018
Grant date	—

Abstract

A method of providing state synchronization between a controller and a switch in a communications network, wherein the controller provides flow data for routing flows through the switch and transmits, in flow modification messages, the flow data to the switch for storage in flow tables, the state synchronization comprising ensuring that flow data in the flow tables of the switch are consistent with the flow data provided by the controller. The method comprises, by the controller (19), providing (21) an identifier in each flow modification message. The method further comprises, upon reestablishment of communications (22) between the controller and the switch after a loss of connectivity receiving (23) a resynchronization message from the switch, wherein the resynchronization message comprises an identifier indication capable of being used to identify an identifier of a most recently received message, determining (24) if all transmitted messages have been received by the switch by comparing the identifier indication with an identifier of a most recently transmitted flow modification message, identifying (25) flow modification messages transmitted after the most recently received message as “un-received” messages and retransmitting (26) un-received messages.

First claim

1 . A controller configured to control a switch in a communications network, wherein the controller is configured to transmit to the switch a plurality of flow modification messages comprising flow data for routing flows through the switch;
wherein the controller comprises: an identifier providing unit arranged to provide an identifier in each flow modification message; a receiving unit configured to receive a resynchronization message from the switch upon reestablishment of communications between the controller and the switch after a loss of connectivity, wherein the resynchronization message comprises an identifier indication for indicating a said identifier of the flow modification message most recently received by the switch; a determining unit configured to determine which one or more of the flow modification message(s) have not been received by the switch based on the received identifier indication: and a retransmission unit configured to retransmit the one or more flow modification messages determined not to have been received by the switch.

2 . A controller as claimed in claim 1 configured for use in a network wherein network control and forwarding are decoupled through abstraction of forwarding functionalities, and/or the controller is a Software Defined Network, SDN, controller.

3 . A controller as claimed in claim 1 configured to transmit to and receive from the switch OpenFlow messages.

4 . A controller as claimed in claim 1 configured to retransmit only flow modification messages which have been determined not to have been received by the switch.

5 . An apparatus as claimed in claim 1 , further configured to determine whether the resynchronization message comprises a said identifier indication, and, if not, to resynchronize a switch state and a controller state by a complete exchange of flow table data between the switch and the controller.

6 . A controller as claimed in claim 5 , further configured to resynchronize a switch state and a controller state by a complete exchange of flow table data by sending a flow data request to the switch, receiving flow data from the switch, or, further configured to resynchronize a switch state and a controller state by a complete exchange of flow table data by sending a flow delete message to the switch and re-sending to the switch each flow modification message in the history.

7 . A switch for use in a communications network, operative to receive from a controller a plurality of flow modification messages comprising flow data for routing flows through the switch, wherein the switch comprises:
a flow modification message receiving unit for receiving from the controller a plurality of flow modification messages comprising an identifier; and a transmitting unit for, on reestablishment of communications between the controller and the switch after a loss of connectivity, transmitting to the controller a resynchronization message comprising an identifier indication capable of being used to identify an identifier of a most recently received flow modification message.

8 . A switch as claimed in claim 7 configured for use in a network wherein network control and forwarding are decoupled through abstraction of forwarding functionalities, and/or the switch is a Software Defined Network, SDN, switch.

9 . A switch as claimed in claim 7 configured to transmit to and receive from the controller OpenFlow messages.

10 . A method of providing state synchronization between a controller and a switch in a communications network, wherein the controller provides flow data for routing flows through the switch and transmits, in flow modification messages, the flow data to the switch for storage in flow tables, the method comprising the controller:
providing an identifier in each flow modification message; and upon reestablishment of communications between the controller and the switch after a loss of connectivity, the controller: receiving a resynchronization message from the switch, wherein the resynchronization message comprises an identifier indication capable of being used to identify an identifier of a most recently received flow modification message; determining if all transmitted flow modification messages have been received by the switch by comparing the identifier indication with an identifier of a most recently transmitted flow modification message; identifying, flow modification messages transmitted after the most recently received flow modification message as “un-received” messages; and retransmitting un-received messages.

11 . A method as claimed in claim 10 , wherein the communications network wherein network control and forwarding are decoupled through abstraction of forwarding functionalities.

12 . A method as claimed in claim 10 , wherein the controller and switch communicate using Openflow messages.

13 . A method as claimed in claim 10 , wherein only unreceived messages are retransmitted.

14 . A method as claimed in claim 10 , further comprising the step of determining at the controller whether the resynchronization message comprises an identifier indication, and, if not, re-synchronizing a switch state and a controller state by a complete exchange of flow table data between the switch and the controller, wherein re-synchronizing the switch state and the controller state comprises either:
the steps of: sending a flow data request to the switch; receiving flow data from the switch; and recording the flow data; or the steps of: sending a flow delete message to the switch; and re-sending to the switch each flow modification message.

15 . A method as claimed in claim 10 further comprising, at the switch:
receiving from the controller a plurality of flow modification messages comprising an identifier; and
on reestablishment of communications between the controller and the switch after a loss of connectivity:
transmitting to the controller a resynchronization message comprising an identifier indication capable of being used to identify an identifier of a most recently received flow modification message.

16 . A method of providing state synchronization between a controller and a switch in a communications network, wherein the controller provides flow data for routing flows through the switch and transmits, in flow modification messages, the flow data to the switch for storage in flow tables, the method comprising the switch:
receiving from the controller a plurality of flow modification messages comprising an identifier; and on reestablishment of communications between the controller and the switch after a loss of connectivity: transmitting to the controller a resynchronization message comprising an identifier indication capable of being used to identify an identifier of a most recently received flow modification message.

17 . A computer program, comprising instructions which, when executed on at least one processor, cause the at least one processor to carry out a method according to claim 10 .

18 . A computer program product comprising a computer program as claimed in claim 17 .

19 . An apparatus for use in a controller in a communications network wherein the controller provides flow data for routing flows through a switch and transmits, in flow modification messages, the flow data to the switch for storage in flow tables, the apparatus comprising processor circuitry, a memory containing instructions executable by the processor circuitry, a transmitter and a receiver, whereby the apparatus is operative to:
provide an identifier in each flow modi

Assignees

• Ericsson Telefon Ab L M

Inventors

• Dutti Enrico
• Bottari Giulio
• Ceccarelli Daniele
• Fondelli Francesco

Classifications

• H04L1/1671

  the supervisory signal being transmitted together with control information · CPC title

• H04L41/0816 Primary

  the condition being an adaptation, e.g. in response to network events · CPC title

• H04L41/0866

  Checking the configuration · CPC title

• H04L41/0813 Primary

  characterised by the conditions triggering a change of settings · CPC title

• H04L45/38

  Flow based routing · CPC title