simplex or duplex?

[Vin Patel_1]

Hi sorry if this is a naive question, but why does ipconfig report the mode 'SIMPLEX' when hwmgr reports full duplex.

for instance (I copied this from a previous post, but our server reports the same thing) why does ipconfig -a show this:



when hwmgr shows this:
full_duplex = 1

For the same interface (i.e tu0 in our case on our ethernet network).

What am I missing? Isn't simplex=half duplex?This is bugging me a bit.

NB: We are using tru64 v5.1b

Thanks
Vin

[Michael Schulte zur Sur]

Hi,

man ifconfig reveals:
SIMPLEX The interface cannot hear its own transmissions. This is a read-only option that is set by the driver.

so no reference to duplex.

greetings,

Michael
http://forums1.itrc.hp.com/service/forums/helptips.do?#28

[Vin Patel_1]

Hi thanks for the response.

Sorry, I should have read furthur in the man ipconfig ;)

However, that just defines what they mean by Simplex but it doesn't explain that ipconfig -a shows the simplex flag when the interface is infact full duplex (via hwmgr)?.

I mean as a flag, I would expect the output of ipconfig -a to either show the flag 'Simplex' indicating same; or if the interface isn't in simplex mode to just conveniently omit the flag.

But no, it shows 'Simplex' big as life? and meanwhile hwmgr continues to report full duplex=1

Also it is irrelevant that the setting is read-only. Presumably the driver should know if it's running its hardware in Simplex, half duplex or duplex etc. Therefore it would write to that flag accordingly (I guess).

I wonder if this flag isn't being updated after auto-negotiation has set the final transmission mode (he says trying to sound like he knows what he's talking about ;))

Anyway, I kinda think the interface can't be simplex because there is a two way communication across it (it supports telnet sessions after all which are two way? We know this because cut telnet users off when we brought the network card down with ifconfig)?

I did a bit of reading (which I prob should have done first ;)) and found simplex is transmission in one direction like a radio and the broadcast station as distinct from half duplex that is is two way communcation (albeit only in one direction at a time).

So I'm still left with my original conundrum.

Ah well, maybe I'll just call it a bug and get on with my life ;)

Thanks again for the response
Vin

[Vin Patel_1]

ahem, errata: of course by ipconfig in the above I mean ifconfig (red face, oops, sorry ... )

[Michael Schulte zur Sur]

Vin,

ipconfig is for windows! ;-)

It seems that I have not made myself clear last time.
Simplex has nothing to do with full or half duplex. It means that what the nic is sending it does not hear itself. That would not make much sense anyway since this would only cost computing time and it is clear what was sent.

hth,

Michael

[Vin Patel_1]

Hi again Micheal and thank you for your patience! (you gotta make it simple for a simple mind y'know ;).

Hmm, I think the light is beginning to dawn.
So the Nic doesn't hear what it is sending - like me talking and not listening to what I am saying (Yep, guess I can relate to that ;) - and thats why the driver sets the Simplex flag. But thats all the driver has to know for the nic hardware to support full duplex functionality in terms of actual packets travelling across the interface.

Ok, maybe that's not it, and it could be a subtle point that I need to sleep on, but I'm quite satisfied now that I'm going in the right direction now, and I don't like to waste any more of your time!

But Thanks again, I do appreciate your help.

Vin

PS: not sure about the scoring system. It kinda assumes that if you give the correct answer to the question, that the person who actually asked the question will understand the answer (and understands the question they asked in the first place!). Hope you don't think my score is too mean!

[Hein van den Heuvel]

An other tool you may want to be aware of in this space is lan_config. Check out it's manpage. It reads:

" You can use the hwmgr utility to verify the parameters that you change with
the lan_config and ifconfig commands. The following command displays
hardware information, low-level configuration settings, and statistics
counters for all of the physical network adapters installed on your system:
:

:"

So hwmgr give the definitive answer.

btw... some folks (Myth :-) would argue that "TCP/IP Services doesn't know or care what speed/simplex your Ethernet card might be using. That's data link stuff."

fwiw,
Hein,

[Vin Patel_1]

Hi Hein, and thanks for the tip and the 'inside info'.

I guess theres a lot of reading I got to do yet about tcp/ip and networking (feel free to recommend any links or texts!) ;)

But I am beginning to realise that all these tools exist to provide a flexible and multi-configurable network interface, with their overlapping and reduntant features not there to confuse newbies but to guide them into an appreciation of the options on offer and what is out there in network-land, and perhaps into a deeper insight into how it all works.

So I feel a bit like a child in a candy store at the moment - delicious! ;)

[Ross Minkov]

You said that you have tu type of network interface. The model of the network card is DE500 (10/100Mbs).
SRM Console Name is ewa0, ewb0, ... ( for tu0, tu1, ...)

To set ewa0 to FastFD at SRM:

>>> set ewa0_mode FastFD

To see all available options try:

>>> set ewa0_mode ?

It will error out and display all valid options.

================================

Always match the port setting and the setting on the network card.
Do NOT set just one of them for auto on. They will talk to each
other but there will be a lot of errors and the network performance
will be terrible.

==============================

The lan_config command allows you to modify the type of medium, speed, and
mode of operation (half- or full-duplex).
You can also use the lan_config command to enable or disable autonegotiation,
if the underlying device has this capability.

Modifications made with the lan_config command do not persist across
reboots of the operating system. To configure the interface or modify the
parameters automatically each time the system is booted, edit the
/etc/inet.local file and add the lan_config command entries to it.

Here is something from the man page for lan_config:

For DE5xx devices (tu), the characteristics managed with the lan_config
command are ordinarily set from the console level via the EWx0_MODE
environment variable. The lan_config command allows you to override this
default and configure the interface as needed after the system is up and
running. For all other devices, you must use the lan_config command to

RESTRICTIONS

You can configure only tu interfaces (DE5xx) by setting the appropriate
console environment variables.

You can also use the ifconfig command to set the speed and mode (half- or
full-duplex) either from the command line or in the inet.local file. If
you specify the command in the inet.local file, the command is executed
each time the system is booted.

============================

The /etc/inet.local file is a file that is called by /sbin/init.d/inet after all
the network interfaces are up and running, but before any other network
services are started.

============================

To verify what an interface is currently set to use hwmgr:

# hwmgr -get attr -cat network | grep -E 'name|speed|duplex|auto|link'

============================

The following commands peek into kernel memory.

- Speed
##
# (ifnet.if_next if the lan target is tu1, ifnet.if_next.if_netxt for tu2, ...)
dbx -k /vmunix
dbx > p ifnet
if_baudrate = speed

- Type
##
# X is the number of the target (tu1,tu2, etc...)
dbx -k /vmunix
dbx> p tu_softc[X].tu_flags
fast_speed = 1 ---> 1-> 100
0-> 10
full_duplex = 1 ---> 1-> Full duplex
0-> Half duplexmy

========================


HTH,
Ross

[Vin Patel_1]

Hi Ross, thanks for the most comprehensive reply!

This is excellent, you guys are great!

A lot of powerful stuff in your comments, need to be very careful with it but load of tips to check our network config. Peering into kernel, wow! Load of stuff to look up there ;)

Looks like I'll be chatting to our network guy about switch port settings ;). The advice about autonegotiation makes sense, anything that avoids error messages must be a good thing ;). Amazing that you know the actual sequence of events.

Like most bad administrators, I kinda skip over a lot of stuff in man to get to the bit that will get your gear working (bad habit I know), but this is great background and I'm getting a great overall picture of it now, rather than just a few disconnected commands (pardon the pun ;).

In short our interface is working but won't do any harm to make sure it is configured properly and reconfigured properly after rebooting.

Loads to digest, so should keep me happily busy. Thanks again for all the advice and instruction! This stuff is better than a lot of dry manuals, although its shown me I don't know a 1/10 of what I need to know so need to study!

The only reason I am keeping this thread open is a selfish one - I get good responses to it, but if I were being honest, I should probably close it now as I guess I am well armed with pointers and ought to go find out stuff for myself instead of relying on you guys, so I will close it... in a few days ;)

[Vin Patel_1]

Thead closed ;)

[Vin Patel_1]

the question has been thouroughly answered!