3 ms·

While I agree it's certainly false, your implementation idea would almost certainly introduce detectable delay. All you'd need is a beam splitter. You can manuf

by enko 13y ago

While I agree it's certainly false, your implementation idea would almost certainly introduce detectable delay. All you'd need is a beam splitter. You can manufacture them to only take 1% of the beam.

Locke1689 13y ago
Sure. But "Hey guys, just to let you know, we moved our relay back a couple meters for reorganization" would also introduce detectable delay -- I doubt anyone actually cares about the delay.
simmons 13y ago
In the late 90's, I attended a presentation that described doing just such a fractional-light fiber split at major exchanges (e.g. MAE-West) to collect data for research purposes. [1] While the researchers were probably trustworthy, I remember thinking that such sniffing seemed like it could be pretty scary in the wrong hands. (The presentation was given by Evi Nemeth, who was sadly in the news recently due to being lost at sea.) [1] http://www.caida.org/workshops/isma/9808/report.html http://www.caida.org/workshops/isma/9808/report.html "The coral/ocXmon family of monitors use optical splitters to tap fiber, filtering 5-10% of the light signal to interface cards in the coral monitoring host."
brown9-2 13y ago
Would such a splitter give you 1% of the messages passed, or 1% of a message?
- cnvogel 13y ago
  These splitter work in the domain of light-pulses transmitted over a fiber. So you get 100% of the messages, but the flashes of light representing the bits will be much weaker. Probably this will mean that you have to put in much more effort to decode the signal than a usual network-device will need, and also probably means that you will have a higher number of errors in your data. On the other hand, if you'd tap only a short distance downstream of the transmitter (or an inline amplifier), that 1% might be plenty, undisturbed by the distortions introduced further on the line, so probably that's the preferable tapping location anyway. [I know that I'm oversimplifying a lot here and modern optical communication systems work much different.]
  - felixfurtak 13y ago
    It depends on the power budget of the fiber link. A 3db splitter would tap 50% of the power, but if this was planned for in advance it would be easily integrated in the long haul network.

by enko 13y ago

Locke1689 13y ago

Sure. But "Hey guys, just to let you know, we moved our relay back a couple meters for reorganization" would also introduce detectable delay -- I doubt anyone actually cares about the delay.

simmons 13y ago

In the late 90's, I attended a presentation that described doing just such a fractional-light fiber split at major exchanges (e.g. MAE-West) to collect data for research purposes. [1] While the researchers were probably trustworthy, I remember thinking that such sniffing seemed like it could be pretty scary in the wrong hands. (The presentation was given by Evi Nemeth, who was sadly in the news recently due to being lost at sea.) [1] http://www.caida.org/workshops/isma/9808/report.html http://www.caida.org/workshops/isma/9808/report.html "The coral/ocXmon family of monitors use optical splitters to tap fiber, filtering 5-10% of the light signal to interface cards in the coral monitoring host."

brown9-2 13y ago

Would such a splitter give you 1% of the messages passed, or 1% of a message?

cnvogel 13y ago
These splitter work in the domain of light-pulses transmitted over a fiber. So you get 100% of the messages, but the flashes of light representing the bits will be much weaker. Probably this will mean that you have to put in much more effort to decode the signal than a usual network-device will need, and also probably means that you will have a higher number of errors in your data. On the other hand, if you'd tap only a short distance downstream of the transmitter (or an inline amplifier), that 1% might be plenty, undisturbed by the distortions introduced further on the line, so probably that's the preferable tapping location anyway. [I know that I'm oversimplifying a lot here and modern optical communication systems work much different.]
- felixfurtak 13y ago
  It depends on the power budget of the fiber link. A 3db splitter would tap 50% of the power, but if this was planned for in advance it would be easily integrated in the long haul network.