[vortex] 3c905C: Packet losses (a more precise description)

[Giuseppe Ciaccio]

I reported wrong data about the mii-diag output in my last message, and
moreover I could not be able to reproduce some of the odd behaviours I
reported previously.

This time, I will try to be more precise and complete :)


Kernel is 2.2.16.  Driver is compiled in the kernel (no module).

NICs are 3COM 3c905C.
Three kind of networks:
	crossover cable,
	repeater hub,
	Intel Express 510T 100base-TX switch (flow control DISABLED!!!).

Boot-time probe message:
3c59x.c:v0.99H 27May00 Donald Becker http://cesdis.gsfc.nasa.gov/linux/drivers/v
ortex.html
eth1: 3Com 3c905C Tornado at 0xa000,  00:01:02:0d:a7:84, IRQ 5
  8K byte-wide RAM 5:3 Rx:Tx split, autoselect/Autonegotiate interface.
  MII transceiver found at address 24, status 782d.
  Enabling bus-master transmits and whole-frame receives.

(NOTE: no "INVALID CHECKSUM" msg)



First scenario:  N-WAY autoneg enabled in both NICs


Crossover cable:

mii-diag reports:

Basic registers of MII PHY #24:  3000 782d 0040 6176 05e1 45e1 0003 0000.
 Basic mode control register 0x3000: Auto-negotiation enabled.
 You have link beat, and everything is working OK.
 Your link partner advertised 45e1: Flow-control 100baseTx-FD 100baseTx 10baseT-
FD 10baseT, w/ 802.3X flow control.

(NOTE: these adapters are flow-ctl capable!)

ping -f reports:
617494 packets transmitted, 617492 packets received, 0% packet loss

Everything seems OK.


Repeater hub:

mii-diag reports:

Basic registers of MII PHY #24:  3000 782d 0040 6176 05e1 0081 0000 0000.
 Basic mode control register 0x3000: Auto-negotiation enabled.
 You have link beat, and everything is working OK.
 Your link partner is generating 100baseTx link beat  (no autonegotiation).

ping -f reports:
528426 packets transmitted, 528424 packets received, 0% packet loss

Everything seems OK.


Switch (N-WAY autoneg enabled):

mii-diag reports:

Basic registers of MII PHY #24:  3000 782d 0040 6176 05e1 45e1 0003 0000.
 Basic mode control register 0x3000: Auto-negotiation enabled.
 You have link beat, and everything is working OK.
 Your link partner advertised 45e1: Flow-control 100baseTx-FD 100baseTx 10baseT-
FD 10baseT, w/ 802.3X flow control.

(NOTE: the switch advertises flow-ctl although disabled!  A bug in mii-diag?
A bug in the switch firmware?)

ping -f reports:
120219 packets transmitted, 119982 packets received, 0% packet loss

237 packets lost, out of 120219 (loss rate = 2%).
The switch reports no errors.



Second scenario:  N-WAY autoneg disabled in both NICs


Switch (N-WAY autoneg enabled):

mii-diag reports:

Basic registers of MII PHY #0:  0000 0000 0000 0000 0000 0000 0000 0000.
 Basic mode control register 0x0000: Auto-negotiation disabled, with
 Speed fixed at 10 mbps, half-duplex.
 Basic mode status register 0x0000 ... 0000.
   Link status: not established.
 Link partner information information is not exchanged
when in fixed speed mode.

Autoneg does not occur (it is switched off at the NICs).
mii-diag reports "10 mbps"; however, the LEDs in the back are saying
"100 mbps".  Who is right?

ping -f reports:
236102 packets transmitted, 236025 packets received, 0% packet loss

Note the loss of as many as 77 packets out of 236102 (loss rate = 0.3%)
The switch reports no errors.


Crossover cable, and repeater hub:  mii-diag as above, no packet losses.



Apparently, it is the switch' fault.  However, if I use other NICs, like the
DEC DE500, the Intel EEPro 100 (one with 82557 and the other with 82558B),
or even the old 3COM 3c905, in place of the 3c905C, no packet losses are
observed through the very same switch.

A problem with flow ctl between my switch and the 3c905C adapters?
Is there any way for disabling flow ctl in the 3c905C?

Giuseppe



Giuseppe Ciaccio               http://www.disi.unige.it/person/CiaccioG/
DISI - Universita' di Genova   via Dodecaneso 35   16146 Genova,   Italy
phone +39 10 353 6638          fax +39 010 3536699 ciaccio@disi.unige.it
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