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Date:      Tue, 01 Jun 1999 12:58:05 +0200
From:      Len Conrad <lconrad@Go2France.com>
To:        freebsd-questions@freebsd.org
Subject:   "transmit interrupt"
Message-ID:  <4.2.0.56.19990601121829.00a35e70@go2france.com>

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Hi,

I'm having trouble getting low and non-variable ping times on 64 kbit 
leased line.  cisco-cisco ping give 24 ms with 64-byte packet, with +/- 1 
or 2 ms variations.  our HDLC-WAN-board-to-cisco ping gives anywhere 
between 300 ms and 40 ms best case.

The WAN board did ping 300 megabytes in 4096-byte packets over several 
hours without any errors using its "Cisco-HDLC" protocol and a 3620 on the 
far end.  We don't have any interrupt or i/o port or memory base (it's an 
8-bit ISA card) or dma conflicts, afaics.

Here is a curious ping  behaviour with 64 byte packets, ping times:

300 ms, 290, 280, 270, ...... 60,40,30 and then repeats
300 ms, 290, ....

Looks like some kind of beating behaviour, or weird buffering interaction 
between software layers.

The board mfr (with his FreeBSD board driver) asks "in Unix, do you have 
transmit interrupts enabled?".  I've looked in rc, rc.config, rc.serial, in 
the Lehey book, in the Handbook, and in LINT.  Nothing that looked relevant.

Any ideas?

tia,
Len





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