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What happens when a disconnected switch reconnects to the controller?

asked 2015-09-05 01:31:04 -0800

Sania gravatar image

Hi,

If a switch connects to the controller and then disconnects, is all data related to this switch removed as well or not? If not then if the same switch connects again, does the controller know the hosts connected to it or not? Also is any of switch information is stored in openflowplugin or is all switch info/data (if any after disconnect) there in the data stores in MD-SAL? In short I want to know what happens when a disconnected switch reconnects to the controller?

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answered 2015-09-12 04:50:11 -0800

Muthukumaran gravatar image

updated 2015-09-12 05:03:11 -0800

If a switch disconnects and reconnects - assuming controller provisioned flows/groups/meters during its earlier session, following happens

Flows, groups and meters for this switch which are in config DS are pushed again to the switch (assuming the DPID of the switch does NOT change of course across disconnect and reconnect)

There are few points to be noted though (planned to be addressed as enhancement bugs of varying quantum of changes required to address the same)

  • When some flows/groups/meters are deleted when switch is in disconnected state, these flows get removed from Config DS and therefore cannot be deleted on switch. This can be an issue for specific usage scenarios
  • When flows/groups/meters are provisioned by applications via direct OFPlugin RPC calls, then, they do NOT get re-provisioned upon reconnect
  • Groups which depend on other groups are not provisioned in order. Its more like bulk-read from DS and pushing to switch. A patch is being worked out for this
  • Some switches would not allow groups referring ports in their action, to be provisioned until the ports become available. This is also being tracked as separate bug

Please follow Openflowplugin dev mailing list with search as "reconciliation" (this is what existing reconnect sync-functionality is called as).

Hope this helps

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Great answer! Thanks.

Sania ( 2015-09-12 21:01:57 -0800 )edit

One more related question; when a disconnected switch reconnects, does it use the previously created channel processing pipeline (created by OF protocol library) or is a new pipeline ceated for each reconnecting switch?

Sania ( 2015-09-29 22:58:20 -0800 )edit
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answered 2015-09-29 21:02:08 -0800

Ashwini_Mhatre gravatar image

Hi , Actully persistent characteristics of config data store is depend on release of opendaylight. if you are using lithium/stable then only config data store is persistence otherwise i think previous release of opendaylight not offering persistence feature for config data store.

Regards, Ashwini mhatre.

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When a disconnected switch reconnects, does it use the previously created channel processing pipeline (created by OF protocol library) or is a new pipeline ceated for each reconnecting switch?

Sania ( 2015-09-30 00:23:04 -0800 )edit

Hi Sania, could you please elaborate on what you mean by "channel processing pipeline" ? I assume that you do NOT refer to Netty Channel processing pipeline - since you mention OF protocol library, right ?

Muthukumaran ( 2015-10-02 01:12:53 -0800 )edit

I see how 'channel processing pipeline' can be confusing. I wasn't referring to netty, what I actually meant was the ingress queues that contain openflow messages from switches. These queues get harvested and items are processed (translated and published to MD-SAL). 1/2

Sania ( 2015-10-02 02:37:54 -0800 )edit

By channel processing pipeline I (wrongly) meant these queues which are created against each switch. So I want to know when a switch reconnects, do incomming messages use the old queues or another one is created upon reconnection of the same switch? I hope it makes sense now. 2/2

Sania ( 2015-10-02 02:39:09 -0800 )edit
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Asked: 2015-09-05 01:31:04 -0800

Seen: 233 times

Last updated: Sep 29 '15