Thanks Raymond and Venkatesan. That is exactly the kind of information I wanted. I incorporated all of your references into the commit message and applied this to master and branch-2.9.
On Tue, Jan 23, 2018 at 05:35:11AM +0000, Venkatesan Pradeep wrote: > Hi Raymond, > > Thanks for providing the references. > > @Ben - we had previously discussed the proposed change on the ovs-dev mailing > list: > https://mail.openvswitch.org/pipermail/ovs-dev/2017-October/339784.html > https://mail.openvswitch.org/pipermail/ovs-dev/2017-October/339785.html > > Thanks, > > Pradeep > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Raymond Burkholder > Sent: Tuesday, January 23, 2018 7:53 AM > To: [email protected] > Subject: Re: [ovs-dev] [PATCH] bfd: Send BFD packets with DSCP CS6 > > On 01/22/2018 03:36 PM, Ben Pfaff wrote: > > Can you provide a reference to something that helps me understand why > > the new value is the "correct" one? This is not my area of expertise > > and all I learn from the commit message is an assertion that the new > > value is better. > > here is a short declaration: > > http://www.ciscopress.com/articles/article.asp?p=357102&seqNum=4 > > A long dissertation: > > https://www.cisco.com/c/en/us/td/docs/solutions/Enterprise/WAN_and_MAN/QoS_SRND/QoS-SRND-Book/QoSIntro.html > > But in a nutshell: > > Network engineers create various queue/drop policies based upon precedence. > Routing protocols are considered high priority/high precedence. During link > saturation events, packets will get dropped. > By creating an egress policy where packets marked by CS6 are allowed > front-of-the-queue status, one can be sure that hello's from the various > protocols arrive when they need to, without delay and without loss. On the > other hand, if the hellos are dropped as part of normal traffic operations, > then traffic routing will flap, leading to further congestion and drops. > > CS6 is a 'well known' marker to network engineers. In many vendor's gear, it > is automatically assigned to routing protocol packets. > > Since OVS does not perform queuing, and leaves that to the kernel edge > operations, the queue policies can be used to ensure timely egress of the BFD > packets during high utilization events. > > > > > > Thanks, > > > > Ben. > > > > On Mon, Dec 25, 2017 at 04:59:22PM +0000, Venkatesan Pradeep wrote: > >> Send BFD packets with TOS value equivalent to DSCP CS6 so that the > >> network can apply the right QoS for those packets. This can help > >> avoid BFD flaps due to network congestion. > >> > >> Signed-off-by: Venkatesan Pradeep <[email protected]> > >> --- > >> lib/bfd.c | 2 +- > >> 1 file changed, 1 insertion(+), 1 deletion(-) > >> > >> diff --git a/lib/bfd.c b/lib/bfd.c > >> index 40cd0be..8d291bb 100644 > >> --- a/lib/bfd.c > >> +++ b/lib/bfd.c > >> @@ -612,7 +612,7 @@ bfd_put_packet(struct bfd *bfd, struct dp_packet *p, > >> ip->ip_ihl_ver = IP_IHL_VER(5, 4); > >> ip->ip_tot_len = htons(sizeof *ip + sizeof *udp + sizeof *msg); > >> ip->ip_ttl = MAXTTL; > >> - ip->ip_tos = IPTOS_LOWDELAY | IPTOS_THROUGHPUT; > >> + ip->ip_tos = IPTOS_PREC_INTERNETCONTROL; > >> ip->ip_proto = IPPROTO_UDP; > >> put_16aligned_be32(&ip->ip_src, bfd->ip_src); > >> put_16aligned_be32(&ip->ip_dst, bfd->ip_dst); > >> _______________________________________________ > >> dev mailing list > >> [email protected] > >> https://mail.openvswitch.org/mailman/listinfo/ovs-dev > > _______________________________________________ > > dev mailing list > > [email protected] > > https://mail.openvswitch.org/mailman/listinfo/ovs-dev > > > > -- > Raymond Burkholder > [email protected] > https://blog.raymond.burkholder.net > > -- > This message has been scanned for viruses and dangerous content by > MailScanner, and is believed to be clean. > > _______________________________________________ > dev mailing list > [email protected] > https://mail.openvswitch.org/mailman/listinfo/ovs-dev > _______________________________________________ > dev mailing list > [email protected] > https://mail.openvswitch.org/mailman/listinfo/ovs-dev _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
