[ovs-discuss] In flow entries should 'action' be set to normal for BFD control packets

[Alex Wang]

On Mon, Feb 9, 2015 at 6:26 AM, Padma Jayasankar <padmajs80 at gmail.com>
wrote:

> Hi,
>  I want to monitor the links that form a path between two hosts. when any
> of the link fails the source switch has to be intimated so that it can
> reroute the traffic through the next alive bucket. for this bfd session has
> to be established between the the source switch and destination
> switch(which are connected to the respective hosts).
>  Now i am able to enable bfd for those to switches using ovs-vsctl
> commands. i also added flow entries for BFD packets, in the switches that
> lie in the path.when a link fails in the path, bfd state of these switches
> is changes to 'down' and when the link is up again , it again changes to
> 'up'. So i thought it supports multi-hop. Is it not so? I am using OVS
> 2.1.1. Please clarify.
>


No, it does not support multi-hop.  If the intermediate switches just
forward
using flows and do not decrement the ttl, then, it could work but it is not
really
multi-hop.  When you have intermediate vendor routers, the ttl of the udp
packets will change.  In ovs bfd implementation, the received udp packet
must have TTL=255.

Thanks,
Alex Wang,


> Thanks and Regards,
> Padma V
>
> On Tue, Feb 3, 2015 at 11:26 PM, Alex Wang <alexw at nicira.com> wrote:
>
>>
>>
>> On Sun, Feb 1, 2015 at 8:43 PM, Padma Jayasankar <padmajs80 at gmail.com>
>> wrote:
>>
>>> Hi,
>>>   I have to use BFD for failure detection and when i went through some
>>> examples the action field for the flow entries were set to 'Normal". Can't
>>> we use 'output' action. In that case i have to add two entries (one for
>>> each direction). Please claridy
>>>
>>
>>
>> The BFD implementation in OVS is mainly used for tunnel link failure
>> detection.  You need to have a tunnel port first and then can you enable
>> bfd on the tunnel port.  The BFD state machine in OVS will compose/send
>> control packets through the tunnel... No OpenFlow rules are involved...
>>
>> We currently do not support multi-hop bfd.
>>
>> However, at this time, it is still unclear what kind of link
>> (tunnel/point-to-point physical link) you want you monitor... maybe you
>> should clarify first,
>>
>> Thanks,
>> Alex Wang,
>>
>>
>>> Thanks and Regards,
>>> Padma V
>>>
>>> _______________________________________________
>>> discuss mailing list
>>> discuss at openvswitch.org
>>> http://openvswitch.org/mailman/listinfo/discuss
>>>
>>>
>>
>
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