Can a standard NIC be triggered to send an electrical sign..

[Guest]

Archived from groups: comp.dcom.lans.ethernet (More info?)

Hi!

Does anyone know if a standard NIC can be configured to send an electrical
signal down a cable? If yes, then can we write a program that can do that?
How? Thanks.

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[Guest]

Archived from groups: comp.dcom.lans.ethernet (More info?)

genielicious_at_yahoo_dot_com@foo.com (NANewbie) writes:

> Hi!
>
> Does anyone know if a standard NIC can be configured to send an electrical
> signal down a cable? If yes, then can we write a program that can do that?
> How? Thanks.

To my knowledge there is no standard configuration / feature for NICs
to send any single pulses to the line when commanded.

With a normal 10Base-T Ethernet card normally when nothing
is transmitted, the line is silent (only some link pulses
could sent every now and then). When you transmit a packet,
the Ethernet card sends a series of bits to the line
presenting the data of the data packet.

So with such card you just need to send a packet, and the
card sends a set of electrical signal pulses to the line...
Any packet will do.
With a TCP/IP networking send out ARP or UDP packet.

With 100 Mbit/s Ethernet (100Base-TX) things are not that simple..
When Ethernet card is transmitting data, you get bits on the line.
But even when the card is not transmitting any actual data, there
are bits traveling through the wire (a known bit pattern that
keeps the data clocks on the oppostite ends of the link syncronized).

--
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at
http://www.epanorama.net/

 

[Guest]

Archived from groups: comp.dcom.lans.ethernet (More info?)

Say I write a program that creates a packet and inject it on the line. The
packet will be sent as a set of electrical signal pulses to the line, as
you say. What happens when they encounter an open circuit in the cable,
do they get reflected due to the impedance mismatch? If the data is
reflected, would it be too corrupted that my program won't be able to
recognise it as the one it sent earlier?

-------------------------------------
Tomi Holger Engdahl wrote:

> genielicious_at_yahoo_dot_com@foo.com (NANewbie) writes:

>> Hi!
>>
>> Does anyone know if a standard NIC can be configured to send an
>> electrical
>> signal down a cable? If yes, then can we write a program that can
>> do that?
>> How? Thanks.

> To my knowledge there is no standard configuration / feature for NICs
> to send any single pulses to the line when commanded.

> With a normal 10Base-T Ethernet card normally when nothing
> is transmitted, the line is silent (only some link pulses
> could sent every now and then). When you transmit a packet,
> the Ethernet card sends a series of bits to the line
> presenting the data of the data packet.

> So with such card you just need to send a packet, and the
> card sends a set of electrical signal pulses to the line...
> Any packet will do.
> With a TCP/IP networking send out ARP or UDP packet.

> With 100 Mbit/s Ethernet (100Base-TX) things are not that simple..
> When Ethernet card is transmitting data, you get bits on the line.
> But even when the card is not transmitting any actual data, there
> are bits traveling through the wire (a known bit pattern that
> keeps the data clocks on the oppostite ends of the link syncronized).





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[Guest]

Archived from groups: comp.dcom.lans.ethernet (More info?)

genielicious_at_yahoo_dot_com@foo.com (NANewbie) writes:

> Say I write a program that creates a packet and inject it on the line. The
> packet will be sent as a set of electrical signal pulses to the line, as
> you say. What happens when they encounter an open circuit in the cable,
> do they get reflected due to the impedance mismatch?

Yes.

> If the data is
> reflected, would it be too corrupted that my program won't be able to
> recognise it as the one it sent earlier?

In 10Base-T ethernet system when the card sent out the pulse
to the wire pair used ot transmit, and it hits an impedance
mismatch, some part of the signal (or all) gets reflected back
through that pair. When the reflected back signal reaches
the card, it is coming to it though the transmit pair.
There is no receiver on transmitting pair. The card does not
know anythign about the signal being reflected on the cable.



--
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at
http://www.epanorama.net/

 

[Guest]

Archived from groups: comp.dcom.lans.ethernet (More info?)

Ohh... ok... hmm... I really have very limited knowledge about what a
standard
NIC is capable of....

Do you by any chance know any online material or books (doubt I can find
them
at the library though) where I can read up about the functionality of a
standard NIC? I need to know what it can and cannot do before I come to a
dead
end again. I tried looking for it before, but this kind of info seems hard
to
find.

Thanks for enlightening me. Really appreciate it. Cheers!


-------------------------------------
Tomi Holger Engdahl wrote:

> genielicious_at_yahoo_dot_com@foo.com (NANewbie) writes:

>> Say I write a program that creates a packet and inject it on the
>> line. The
>> packet will be sent as a set of electrical signal pulses to the
>> line, as
>> you say. What happens when they encounter an open circuit in the
>> cable,
>> do they get reflected due to the impedance mismatch?

> Yes.

>> If the data is
>> reflected, would it be too corrupted that my program won't be able
>> to
>> recognise it as the one it sent earlier?

> In 10Base-T ethernet system when the card sent out the pulse
> to the wire pair used ot transmit, and it hits an impedance
> mismatch, some part of the signal (or all) gets reflected back
> through that pair. When the reflected back signal reaches
> the card, it is coming to it though the transmit pair.
> There is no receiver on transmitting pair. The card does not
> know anythign about the signal being reflected on the cable.






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