[LINK] America's Internet Disconnect

[Adrian Chadd]

On Fri, Nov 10, 2006, rchirgwin at ozemail.com.au wrote:

> Between a US server and here we have (roughly!):
> - lots of router hops (from Sydney to samspade.org = 10 hops).

Maybe half a mil to one millisecond a hop? Depends on a whole lot of
factors.

Heck, thats just L3 hops. You generally don't have any idea what the
underlying topology is; whether there's tunneling involved (GRE/IPIP/etc),
L2 stuff (MPLS for various values of L2, ATM/FR) and SONET-style backbones.

> - several points of "oversubscription" (ie, more bandwidth sold than is 
> provisioned). Eg: Customers to DSLAM; DSLAM to ISP; Australian ISP's 
> transit connection; and transit connection between US ISP and source 
> Website).

* Oversubscription doesn't necessarily lead to higher latency.
  Full TX queues with crappy (read: FIFO, or badly tuned weighted stuff)
  queueing. Congestion is what matters, not oversubscription.

> - Plus 40 milliseconds (approx) speed of light across the Pacific.

Gotta remember; the speed of light in fiber isn't the speed of light in a vacuum.
I think you'll find its ~ 30-35ish ms each way Per-Mel. I can't believe its
40ms each way from Syd -> West coast.

> What would I bet on causing slow speed, the combination of 
> oversubscription and many router hops, or the speed of light?

Router hops by themselves don't lead to latency. Thats been a fallacy for
quite a while. (Queue rant about howrouter hop performance is generally
not indicative of forwarding performance or congestion.)

> Oversubscription on DSLAMs ranges upwards of 20 subscribers per unit 
> bandwidth to "who knows" in the cheapie services. Oversubscription on 
> the DSLAM backhaul isn't published; nor is transit oversubscription; and 
> I don't know typical ratios in the US.

> If US users get better performance on similar links, I would put it down 
> to cheaper transit access leading to less congestion...

US users get better performance because:

* the cost of transit is cheaper;
* the cost of backhaul exchange/ISP network is (probably) cheaper;
* the cost of general network infrastructure might be cheaper, but
  again Pipe/Amcom/Bright/etc have made it more affordable to build
  city-wide networks (thanks Telstra!)
* the sites they want are in the US or Europe ; not hiding away in Australia
  at ~ 200-350ms away.


Adrian