[e2e] Re: a problem...

[Zartash Afzal Uzmi]

If the simple way on copper is to detect a DC "transmitted" by N2, then
an equivalent simple way on wireless is to detect a sine wave at f GHz
transmitted by N2. 

Constant magnitude constant frequency Sine wave is as much
information-less as the DC itself!

I think you should specify the "layer" when you say that "do not wish to
send a reverse ack". For example, consider a voltage source connected
through a long transmission line to a resistor. In this case, resistor
is my N2 and its open-circuit/in-circuit condition will tell me whether
N2 is alive or not. Clearly, N2 is not going to be able to send any ACK
but the input impedance seen by N1 (my voltage source) will be able to
indicate whether N2 is alive or not.

In above example, are we sending a signal from N2 to N1? Well, the
conductor pair is sort of acting as a reverse channel at the physical
layer but clearly no ack is sent at network layer.

You can think of replacing the resistor by the input impedance of a live
node...

Now here might be something interesting. As with a voltage source,
copper conductors, and resistors, I can detect the state of N2 (open or
close). i.e., no network layer ack but phy layer ack is implicitly
there. Can we do a similar thing over wireless and/or fiber? I am not
sure and haven't looked at passive RFIDs but aren't they supposed to be
detected in a similar way as the voltage source, conductor and resistor?
Someone familiar with passive RFIDs should speak up. If these two cases
are similar, do we have something to act similarly over a fiber?

zartash

-----Original Message-----
From: end2end-interest-bounces at postel.org
[mailto:end2end-interest-bounces at postel.org] On Behalf Of Puddinhead
Wilson
Sent: Friday, January 14, 2005 8:36 AM
To: end2end-interest at postel.org
Subject: [e2e] Re: a problem...

perhaps I should modify as someone asked for
clarification,

Channel between N1 and N2 has bandpass X, centred at f
(ofcourse copper behaves like copper)

do not wish to send a reverse "ack" for link detection
etc.

What are the simplest ways to do this,
for example the case of copper would be to simply
apply a DC voltage from the receiver side so that
txmtr can look at presence/absence of DC line voltage
to know link status.

What do i do for other cases like fiber or wireless?

 --- Puddinhead Wilson 
<puddinghead_wilson007 at yahoo.co.uk> wrote: 
> Hi there!
> 
> I have 
> N1----->N2
> 
> link from N1 to N2 is physical wire/unidirectional
> wave guide.
> 
> 
> No reverse connection possible
> 
> 1. if the media is copper, how does N1 detect that
> link N1-N2 is down so it should not transmit? (i
> think
> i can solve this one)
> 2. if the media is fiber/wireless how will i solve
> this? (i dont know how to this one :( )
> 
> any takers?
> 
> 
> 
> 	
> 	
> 		
>
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