Re: Diagnosing network slowness: server or network?

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Date: Sat, 25 Jun 2005 07:16:50 +0200

In comp.unix.admin Walter Roberson <roberson@ibd.nrc-cnrc.gc.ca>:
> In article <bqVue.295$Tk2.256@trnddc02>,
> sinister <sinister@nospam.invalid> wrote:
> :The curious thing is that all the cheap Suns with *really* bad problems
> :(i.e., graphics taking minutes to load, not just ftp slowness) show no
> :intervening hosts/switches/whatever when I run traceroute. Hosts that show
> :ftp slowness but graphics relatively unaffected show intermediate switches
> :according to traceroute.

> switches don't show up in traceroute -- only layer 3 hops decrement
> the TTL field so only layer 3 hops can return icmp ttl exceeded messages.

> Your v1280 server is unlikely to have more than a couple of ports,
> so you almost certainly have a layer 2 switch in the middle that is
> not showing up.

> Anyhow, your description sounds very much like duplex problems to me.

Second that.

> I would suggest that you should launch right in to forcing the
> speed and duplex on the v1280 server and the switchport it is
> connected to: instances in which forcing speed and duplex on
> both ends make things -worse- are quite uncommon (but not unknown :( )

> The test after that would be to force speed and duplex on one of
> the cheap Suns you mention (and corresponding switchport).

> There is no firm agreement about autonegotiation vs forced
> speed and duplex. The rule of thumb that seems to be most common
> is that speed and duplex should be fixed for critical infrastructure
> (switches, routers, key servers), but that autonegotiation should be
> used for desktops. (Opinions vary on this, though!!) The practical

Yep, from my experience the only OS able to handle
auto-negotiation perfectly is Linux. Most distro come with
mii-tool or/and eth-tool, allowing to check/set settings on the
system (all good NICs) on Solaris ndd can do this for you. But
mii-tool allows in addition to see what the other side of the
link is advertising:

# mii-tool -v eth2
eth2: negotiated 100baseTx-FD, link ok
  product info: vendor 00:aa:00, model 56 rev 0
  basic mode: autonegotiation enabled
  basic status: autonegotiation complete, link ok
  capabilities: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD
  advertising: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD
  link partner: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD
  ^^^^^^^^^^^^ flow-control

[..]

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• Previous message: Tim Skirvin: "Re: Managing Sun Patches - Strategy & Tools"
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