ExOS rate-limit flood- broadcast Flood Rate Exceeded

[Alexandr_Viktor]

Hi everyone.

I have some problem with control broadcast in my network.
If i set broadcast flood rate in something like 30000, i saw that Flood Rate Exceeded counter increases, but in Rx Pkt Bcast i saw maximum 50-100 packets per second.
MCast & UnkCast rate set to no-limit
sc1 # show ports 7 rate-limit flood port-number
Port Rate-Limit Discard Monitor Sat Feb 18 15:21:43 201777
Port Link Rx Pkt Rx Byte Rx Pkt Rx Pkt Flood Rate
State Count Count Bcast Mcast Exceeded
================================================================================
7 A 10532496 1630959311 10531169 1406 10531364
Can you tel me what packet drop switch?

Also i fond this page https://extremeportal.force.com/ExtrArticleDetail?an=000083176, but i can't understand what it is the magic number: 15.625

TU for your answer? sory for my englishh=)

[Roy_Noh]

Let's divide time frames in every 15.625 microsecond.
( t0, t1 = t0+15.625, t2 = t1 + 15.625 ... tx+1 = tx + 15.625 )
If you set the limit to 64 pps(to be simple), 64 tokens will be given to the switch on every time frame.
As the article says, the switch needs 64,000 tokens to forward 1 packet.
How many cycle the switch need to have 64,000 tokens? 64,000/64 = 1,000

Let's say the switch does not have any token from beginning and when can it forward a packet?
t0 => 0 token, insufficient token, packet dropped
t1 => 64 tokens, insufficient tokens, packet dropped
...
t1000 => 64,000 tokens, use all of those to forward 1 packet
t1001 = > 64 tokens, insufficient tokens, packet dropped
....

So any packets that come to the switch from t0 to t999 will be dropped.

In ideal situation when the broadcast packets are coming in every 1,000th time frame, 64 packets will be forwarded in 1 second since 64,000 * 15,625 microsecond is approximately 1 second.

[Alexandr_Viktor]

TY for your answer, but i can't understand what exactly I set with command:
configure ports 14 rate-limit flood broadcast 60This means that first 60 packets go on and 61 packet will be dropped. Or using this command i set tokens count that generated switch, when it forvarding 1 packet?

[Roy_Noh]

To be simple, if you set rate-limit value of 64,000 it is given 64,000 tokens to a switch in every 15.625 microsecond. And since 64,000 tokens are good for 1 packet, the other packets will be dropped if those are coming into the switch within 15.625 microsecond.
So even if you see there's only 50 to 100 packets in average, there's still a possibility the switch drops packets when an interval time between two packets is very short.