On Mon, 9 Dec 2013, Matthew Ford wrote:
The report of the Reducing Internet Latency workshop is now available:
http://www.internetsociety.org/blog/2013/12/speeding-internet-reducing-latency
Reading through this I generally like it. It's a good summary and
introduction.
However, this part:
"Hiding packet losses in broadband lines using interleaving can add about
20ms of delay, even though modern transports and applications are robust
to such low packet loss levels;"
Having been part of a decently sized ADSL2+ deployment ISP, I have some
experience with this and the above doesn't match them. We actually did get
customer complaints when we were running ADSL2+ in fast-mode (no
interleaving), that the customers were getting packet losses that affected
their applications.
So I would have liked the above to not say "broadband lines" but instead
said ADSL(2+) broadband lines (because the above statement only relates to
ADSL(2+) afaik), and also that the packet losses can be non-trivial for
some and that ISPs don't turn on interleaving out of ignorance. It's hard
to measure customer impact of "errored seconds" which is the only way the
ISP can see packet losses. Also, these errored seconds can be quite
severer when it comes to number of packets dropped.
We actually did talk about having a self-service portal where the customer
could choose their preferred profile, either fast (no interleaving), 4ms
or 16 ms interleaving, and also their safety margin to 6, 9 or 12 dB. Fast
or 4ms interleaving worked well with 12 dB SNR margin (which means lower
latency but also lower access speeds), whereas 6dB margin often required
16ms interleaving to work well.
--
Mikael Abrahamsson email: [email protected]
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