Can you please share the output of: show class-of-service shared-buffer
on your QFX5100 ? Cheers James Il giorno ven 19 nov 2021 alle ore 11:58 Thomas Bellman <bell...@nsc.liu.se> ha scritto: > On 2021-11-19 09:49, james list via juniper-nsp wrote: > > > I try to rephrase the question you do not understand: if I enable cut > > through or change buffer is it traffic affecting ? > > On the QFX 5xxx series and (at least) EX 46xx series, the forwarding > ASIC needs to reset in order to change between store-and-forward and > cut-through, and traffic will be lost until the reprogramming has been > completed. Likewise, changing buffer config will need to reset the > ASIC. When I have tested it, this has taken at most one second, though, > so for many people it will be a non-event. > > One thing to remember when using cut-through forwarding, is that packets > that have suffered bit errors or truncation, so the CRC checksum is > incorrect, will still be forwarded, and not be discarded by the switch. > This is usually not a problem in itself, but if you are not aware of it, > it is easy to get confused when troubleshooting bit errors (you see > ingress errors on one switch, and think it is the link to the switch > that has problems, but in reality it might just be that the switch on > the other end that is forwarding broken packets *it* received). > > > > Regarding the drops here the outputs (15h after clear statistics): > [...abbreviated...] > > Queue: 0, Forwarding classes: best-effort > > Transmitted: > > Packets : 6929684309 190446 pps > > Bytes : 4259968408584 761960360 bps > > Total-dropped packets: 1592 0 pps > > Total-dropped bytes : 2244862 0 bps > [...]> Queue: 7, Forwarding classes: network-control > > Transmitted: > > Packets : 59234 0 pps > > Bytes : 4532824 504 bps > > Total-dropped packets: 0 0 pps > > Total-dropped bytes : 0 0 bps > > Queue: 8, Forwarding classes: mcast > > Transmitted: > > Packets : 6553704 88 pps > > Bytes : 5102847425 663112 bps > > Total-dropped packets: 279 0 pps > > Total-dropped bytes : 423522 0 bps > > These drop figures don't immediately strike me as excessive. We > certainly have much higher drop percentages, and don't see much > practical performance problems. But it will very much depend on > your application. The one thing I note is that you have much > more multicast than we do, and you see drops in that forwarding > class. > > I didn't quite understand if you see actual application or > performance problems. > > > > show class-of-service shared-buffer > > Ingress: > > Total Buffer : 12480.00 KB > > Dedicated Buffer : 2912.81 KB > > Shared Buffer : 9567.19 KB > > Lossless : 861.05 KB > > Lossless Headroom : 4305.23 KB > > Lossy : 4400.91 KB > > This looks like a QFX5100 or EX4600, with the 12 Mbyte buffer in the > Broadcom Trident 2 chip. You probably want to read this page, to > understand how to configure buffer allocation for your needs: > > > https://www.juniper.net/documentation/us/en/software/junos/traffic-mgmt-qfx/topics/concept/cos-qfx-series-buffer-configuration-understanding.html > > In my network, we only have best-effort traffic, and very little > multi- or broadcast traffic (basically just ARP/Neighbour discovery, > DHCP, and OSPF), so we use these settings on our QFX5100 and EX4600 > switches: > > forwarding-options { > cut-through; > } > class-of-service { > /* Max buffers to best-effort traffic, minimum for lossless > ethernet */ > shared-buffer { > ingress { > percent 100; > buffer-partition lossless { percent 5; } > buffer-partition lossless-headroom { percent 0; } > buffer-partition lossy { percent 95; } > } > egress { > percent 100; > buffer-partition lossless { percent 5; } > buffer-partition lossy { percent 75; } > buffer-partition multicast { percent 20; } > } > } > } > > (On our QFX5120 switches, I have moved even more buffer space to > the "lossy" classes.) But you need to tune to *your* needs; the > above is for our needs. > > > /Bellman > > _______________________________________________ juniper-nsp mailing list juniper-nsp@puck.nether.net https://puck.nether.net/mailman/listinfo/juniper-nsp