[vortex] Strange Link Behaviour of 3C90x Card with Fiber Converters

[Donald Becker]

On Mon, 22 Jul 2002, Patrik Schindler wrote:

> We use the following setup:
> 
>  +---------+   +--------+       +--------+   +--------+
>  | 3C90x   +---+ LWL-TP +-------+ LWL-TP +---+ Switch |
>  +---------+   +--------+       +--------+   +--------+
> 
> The Cards are both 3C900(B) and 3C905(B&C-TX).
> The Converters are Allied Telesyn with link-thru feature and 
> Auto-Negotiation support (MC-xxx).

What does 'mii-diag --watch' report?

> We tested some types of switches: Allied Telesyn, 3Com 3300 Series and two
> No-Name products. All show the same behaviour. The most interesting part 
> is that simple (single speed) hubs just work.

That points out the problem is the autonegotiation timing.

> After connecting the device(s) no link could be established. When I type
> an "ifconfig eth0 down" and thereafter an "ifconfig eth0 up" then I can
> see from the LEDs that the card establishes a link to the first converter.
> This device itself switches on the link of the fiber side. The other
> converter switches the link on the ethernet side on. Then the switch
> itself recognizes the signal and sends it's link-signal back. When the
> link arrives back at the card, the card (or the driver) has given up. The
> link is gone.

That means the media type converters tooks too long to establish link.
Media type converters are notorious for violating the specs, and these
appear to be no exception.

> The whole process takes only a few seconds, maybe 1 or 2.

Without knowing the the details of the devices I can't guess where the
timing problem is, but process slow enough to observe is too slow for
the autonegotiation protocol.

> I'm sure that this problem is card/driver related, since a Intel
> EtherExpress Pro doesn't show this behaviour.

Which specific card?

Again, what does 'mii-diag eth0 --watch' report?

-- 
Donald Becker				becker@scyld.com
Scyld Computing Corporation		http://www.scyld.com
410 Severn Ave. Suite 210		Second Generation Beowulf Clusters
Annapolis MD 21403			410-990-9993