[e2e] two questions about the Internet

[Ping Pan]

Sally Floyd wrote:
> 
> PERIODS OF EXTREME CONGESTION AT A ROUTER?
> For those routers in the network that do occationally experience
> congestion, how can we characterize their rare periods of *extreme*
> congestion (defining extreme congestion, say, as packet drop rates
> above 5%)?  How frequently to these periods of extreme congestion
> occur, and how long do they last?  What fraction can be attributed
> to flash crowds? to Denial of Service attacks? to fiber cuts or
> other routing changes?
> 

Almost forgot, please take a look at http://www.nordu.net/stats/. This
is one of the better places where you can monitor the link traffic for
both average and peak rates, and draw your own conclusion on link
congestion and duration.

In the past several years, most of US providers stop showing their
networks, and only provide the average bw utilization, which is low
anyway. It is believed that the peak/average ratio is around 3-4 or
higher, but I have not seen solid evidence on this since NSFNET.

I don't think there are too many fiber cuts in the network (well... on
the other hand, China-US undersea cable was cut many days ago, and the
link was still down.) But in some networks, providers do shift traffic
between links quite often.

- Ping