>>>>> "BM" == Bill Moran <[EMAIL PROTECTED]> writes:
BM> In response to Ryan Novosielski <[EMAIL PROTECTED]>: >> > - A switch (mostly 3Com switches in my experience) that run in >> > half-duplex >> > mode, which slows network traffic down by about a factor of 10. >> >> Cisco does this just as often, if not more often. A little surprising to >> find that the top 2 can't seem to compete on the same level as a D-Link >> switch from Radio Shack. ;) BM> If you read Cisco's docs, they make the claim that these problems are BM> per-spec. BM> My understanding of the argument is that if you manually set the speed BM> and duplex, you have disabled auto-negotiation. If the other end BM> tries to auto-negotiate, it will be able to detect the speed, just by BM> dumb luck of how the protocol works, but it will _consistently_ mis- BM> detect the duplex, again because of dumb luck of the protocol BM> Their argument seems to be that this behaviour is per the specs. If BM> a D-Link does it differently, then D-Link is doing it "wrong", even if BM> it's doing it more intuitively. BM> If Cisco is correct, then it would seem as if the spec were written BM> poorly. This is a bit off-topic, but anyway... The standard spec is IEEE 802.3 std 200[025], and it specifies the auto-negotiate (auto-neg) protocol (among other things). If both ends implements auto-neg as specified, everything works fine and you get the best link-settings both supports. If you turn off auto-neg, you have to set the port to the same setting in both ends. The only reason to turn off auto-neg is that one end isn't implementing auto-neg according to spec (and I'd say it is broken). In that case you have to setup the ports in both ends manually in order to guarantee that it works. If one end is set to auto-neg and the other is hard set to 100 Mbps full duplex with auto-neg turned off, the auto-neg port will end up in 100 Mbps half duplex in most cases. The reason for this is that it will not receive any answer to the auto-neg messages, and will then in most implementations resort to parallel detection. Parallel detection can sense the speed (10 or 100 Mbps) but it is fundamentally impossible to know if the other end is set in full or half duplex, without auto-neg. All bridges and stations supporting full duplex are supposed to implement the standard, and use the auto-neg protocol. A peer-partner not implementing auto-neg is assumed to only support half duplex. That's why the auto-neg end are set in half duplex. Why would you turn off auto-neg if you want automatic link-configuration??? / Anders ------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 _______________________________________________ Bacula-users mailing list Bacula-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bacula-users
