bce packet loss

[Chuck Swiger]

On Jul 6, 2011, at 12:27 PM, Kevin Oberman wrote:
> 1 in 10**6? That is totally excessive.

It's high for a switched LAN, but I'd imagine you remember collision rates on hubs, which might well exceed 1% of the packets when the network is under load.

> The Ethernet spec requires no worse than 10**13 and that is far worse than should ever be seen in the real world. At one in a million, any remotely high volume transfer will crawl, especially over a long path.

10 Gigabit ethernet wants cabling spec'ed to a BER of 10e-13; standard gigabit ethernet cabling (Cat 5e) supposedly is rated for 10e-10.  However, the BER of the cabling doesn't translate directly into octet error count per the NIC statistics, since a bad bit anywhere in a packet causes the entire packet to be dropped with a failed checksum.

> If dropped packets ate being reported, the most common cause is fan-in. If two input ports are both trying to talk a line rate to a single output port, the buffer will fill an packets will be dropped. Most switches do tail drop, so queue management is terrible, compounding the effects.

Yes, I agree with this as a likely cause.

Regards,
-- 
-Chuck