Re: [RE] Latencies through RE cables (better URL)
David-
The delay values from the current 802.3 standard for the components of
these items (including cable delays) can be found at
for 100BASE-TX: In Table 29-3
for 1000BASE-T: In Table 42-3
of IEEE Std 802.3 - 2002
This will give you the Dot3 values to build up towards a per-hop system
value, in turn giving you the remaining budget for a bridge (assuming you
have picked an overall budget as you propose below). It also gives you the
possible values that could be achieved if a physical layer solution were
pursued.
I hope this helps.
Geoff
At 01:52 PM 4/26/2005 -0800, David V James wrote:
>All,
>
>(The URL has been updated, after David Law
>provided a more universally accessible web page).
>
>Things seem to have been quiet for the last week.
>Perhaps I could stimulate some discussions on
>cable latencies?
>
>I believe Alexei's presentations have claimed that
>interactive latencies of 15ms are nearly audible.
>
>Since the link delays are only part of the delay
>equation, this has led some of us to believe that
>(worst case) per-hop latencies should not exceed
>0.5ms. (This number is much more than the speed
>of light, since it includes buffer and conflict
>delays.)
>
>Is there any controversy with using this as a
>working per-hop maximum delay number?
>
>For background material on this topic, please
>reference pages 15-17 of the following
>working paper:
>
> http://www.ieee802.org/3/re_study/material/index.html
> (Thanks again to David Law for his quick posting!!)
>
>I have spent the last week accumulating content
>of various slide presentations into the above
>listed working paper. Hopefully this will be helpful
>when considering this and other issues.
>
>DVJ
>David V. James
>