Re: "Network Neutrality" or "Open Internet"

[Sean Donelan <sean () donelan com>]

On Sat, 15 Apr 2006, Dude VanWinkle wrote:
> I am having a hard time wrapping my brain around this one,
>
> If you buy a T1 from AT&T, arent they supposed to provide 1.5 mbps to
> you? If google buys an OC48 or a few thousand Dedicated Lambdas, arent
> they supposed to get the bandwidth as well?

If you buy a point-to-point, dedicated T1 you will receive exactly a T1
worth of capacity between those two points.  However, people buying packet
swtiched or Internet connections are not buying point-to-point, dedicated
circuits beyond the first network switch/router.

With a phone switch you get 1 voice grade circuit connection or you
get a busy signal.  The PSTN is not engineered so everyone making a phone
call at the same time. A phone switch may have 100 POTS lines and for 10
upstream trunk lines. If more than 10% or so people try to make phone
calls at the same time, the phone switch will probably give a "fast busy
signal" or all circuits are busy.  A circuit switched network tends to be
all or nothing.

With a router you may have 100 downstream T1 (1.544Mbps) circuits and 1
DS3 (45Mbps) upstream circuit.  Unlike the PSTN, the Internet doesn't
have an explicit "all circuits are busy signal."  Instead our theoritical
router with 45Mbps upstream won't give each of the 100 downstream users a
full T1's worth of capacity, they will only get a portion of the 45Mbps
of upstream capacity.  This process repeats at every network router, e.g.
the next router may have 100 DS3 downsream circuits and 2 OC3 upstream
circuits. In a packet switched network, your end to end bandwidth is
determined by the most congested network point in the path, not
necessarily your access link.

ATM and frame-relay networks are sometimes sold with a "Committed
Information Rate (CIR)" which may be a bandwidth number between 0Mbps
and the speed of your access link.  Although typically the maximum
CIR will be less than 80% of the access link speed.  A CIR is part of
the contract with the service provider to guarantee you will be able to
get at least that amount of bandwidth between two points on the providers
network.  Generally service providers only offer CIR guarantees on
their own network, not across other service provider networks.

Networks with CIR's are more expensive than networks without CIR's, so
fewer people pay for them.  Most Internet connections, and essentially
all residential Internet connections, are sold as "best-effort" which
means they have a "0 Mbps" Committed Information Rate.

Or to put it another way suppose a carrier sold Internet service like
this

   0Mbps CIR (10Mbps Peak Information Rate): $50/month "Best Effort"
   1Mbps CIR (10Mbps PIR): $100/month
   10Mbps CIR (10Mbps PIR): $500/month

Which means on the theoritical router with a 45Mbps upstream connection
it forward packets in the following order

First, subscribers paying for 10Mbps service, up to 10Mbps.
Second, subscribers paying for 1Mbps service, up to 10Mbps.
Third, subscribers paying for 0Mbps service, up to 10Mbps.

The peak information rate is the same in all three cases, 10Mbps. B
But when there is congestion on the router's upstream circuit the 10mbps
CIR subscribers always get 10Mbps, the 1Mbps CIR subscribers always get at
least 1Mbps, and the "Best Effort" 0Mbps CIR subscribers get the remaining
capacity.  The Best Effort CIR subscribers may get 10Mbps a lot of the
time, but are the first ones bumped when the router is congested.

Best Effort is much cheaper than CIR, but like buying a "standby" ticket
on an airplane flight you are also accepting the risk that there might
not be capacity on a particular flight.  If you want a committed
information rate, all the carriers are more than happy to sell you a
different product (dedicated circuits, ATM, frame-relay, or the proposed
"premium" Internet) with that guarantee.

> Wouldnt adding/removing QoS to the packets violate the ToS? Are they
> still getting the B/W they paid for?

You can buy a dedicated T1 (1.544Mbps) circuit between two points for
$2,000/month; you can buy a 8Mbps cable modem connections for $50/month.
What are you actually buying?

"Best Effort" means on a space available basis.  If you read the "*" in
the terms of service, it doesn't promise any particular amount of capacity
on an end-to-end basis.

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