Date: Mon, 16 Sep 1996 10:44:55 -0700 From: Jim Shankland <jas@flyingfox.COM> To: jab@rock.anchorage.net, kelly@fsl.noaa.gov Cc: freebsd-hardware@FreeBSD.org, hackers@FreeBSD.org Subject: Re: Very Slow Ethernet Link Message-ID: <199609161744.KAA07081@saguaro.flyingfox.com>
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OK, so several correspondents have pointed out that 0.356ms (ping RTT for 127.0.0.1 on FreeBSD) is less than 1.1 ms (ping RTT for 127.0.0.1) on Linux. On the assumption that the original mail was not a mis-timed April Fool's prank, let me make two small, additional observations: (1) Packets to 127.0.0.1 will go through the loopback interface, so Ethernet has nothing to do with it. (2) It is possible that jab@rock.anchorage.net was looking at the ttl value rather than the RTT. The ttl was 64 for Linux, 255 for FreeBSD. This has nothing to do with ping times, but rather with the maximum number of hops that a packet can make before it is discarded on the assumption that there is some routing loop. It needs to be larger than the largest number of hops that a packet could legitimately make en route from its source to its destination. 64 is probably sufficient in today's Internet; 255 works, too, and may be a better choice. If ttl is to be the measure of performance, then sysctl -W net.inet.ip.ttl=32 will cause FreeBSD to run circles around Linux :-). Jim Shankland Flying Fox Computer Systems, Inc.
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