Re: Network stack/ethernet driver issues
Re: Network stack/ethernet driver issues
- Subject: Re: Network stack/ethernet driver issues
- From: William Kucharski <email@hidden>
- Date: Fri, 11 Apr 2008 07:25:50 -0600
Michael Cashwell wrote:
I'd just run across the "UDP == throw-away" mindset in William's post in
other contexts (mainly sysadmins configuring routers) and wanted to
point out that it's not really correct in all cases.
Well, there's a grey area here between what is "correct" and what is allowed.
If a particular router or system wanted to pass (being silly here) one UDP
packet per hour, it could and wouldn't be violating any of the rules of IP
networking. That doesn't mean it's a bad idea to drop those packets, but it's
not technically incorrect behavior to do so.
In this particular case, the fact that ring buffer overflow messages are being
generated seems indicative that the behavior is not what was intended by the
driver authors. The fact that Linux does not display a similar error when run
on the same hardware seems to back up this point, but at the same time we don't
know what Mac OS X's priorities are when it comes to maintaining isochronous
system events. It may have perfectly good reasons it believes it's OK to let
the ring buffer overflow.
Nevertheless, the fact that so much CPU is being consumed to process the UDP
packets is pretty much evidence to me that something isn't working the way it
was designed, or putting a Mac OS X box on any busy network segment would be
enough to bring it to its knees.
(Stupid trivia fact: Did you know that dealing with network interrupts is an
OLD Mac problem? Back in 1988, putting a Mac II (68020 + PMMU) running A/UX 1.0
or 1.1 on a busy Ethernet network would cause the Mac to first choke then shut
off its Ethernet card entirely as it just couldn't handle the traffic properly.)
William Kucharski
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