[ovs-dev] TOS for BFD packets

Raymond Burkholder ray at oneunified.net
Tue Oct 17 10:51:15 UTC 2017


> The implementations I've worked on have used tos=0xC0 (DSCP CS6). Given
> that DSCP CS6 is recommended for network control traffic, and is used by
> OSPF, BGP etc., I think it is likely that many implementations do that for
BFD
> too. Since BFD flaps have significant impact, marking BFD packets with the
> right DSCP value will allow the network to apply the right QoS for those
> packets and prevent BFD flaps due to network congestion.

For my two cents. I would agree with the higher precedence marking for BFD,
having worked and am working in that world, and preventing routing protocol
timeouts in congested links is an important network operations practice.

> 
> Regards,
> 
> Pradeep
> 
> -----Original Message-----
> From: Ben Pfaff [mailto:blp at ovn.org]
> Sent: Monday, October 16, 2017 11:13 PM
> To: Venkatesan Pradeep <venkatesan.pradeep at ericsson.com>
> Cc: ovs-dev at openvswitch.org
> Subject: Re: [ovs-dev] TOS for BFD packets
> 
> On Mon, Oct 16, 2017 at 04:32:45PM +0000, Venkatesan Pradeep wrote:
> > BFD packets are being sent with tos = IPTOS_LOWDELAY |
> > IPTOS_THROUGHPUT which would put them in the best-effort class. It
> > would be better if we send with tos = IPTOS_PREC_INTERNETCONTROL so
> > that they can be appropriately prioritized in the network.
> 
> Is that common practice for other BFD implementations?  If so, then I
agree
> that OVS should follow it also.
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