Home media servers, AUPs, and upstream bandwidth utilization.

Steve Gibbard scg at gibbard.org
Wed Dec 27 21:09:28 UTC 2006

On Sun, 24 Dec 2006, Roland Dobbins wrote:

> In the U.S. and Canada, the expectation has been set to an assumption of 
> 'unlimited' bandwidth consumption for a fixed price in the consumer market. 
> AT&T WorldNet helped popularize that model early-on (you can thank or curse 
> Tom Evslin for that, according to your inclinations, heh), and it has become 
> de rigeur for most U.S./Canadian broadband SPs to follow suit.
> Which raises a related question of whether North American operators believe 
> that offering value-added services such as placeshifting (which is a familiar 
> enough concept that a significant population of the userbase seem to grasp 
> the idea without a lot of explanation) might prove amenable to metered 
> billing?

IANAE (I am not an economist), but:

At the Peering BOF in Saint Louis, somebody commented on how when you put 
a group of network engineers into a room, pretty soon they stop talking 
about engineering and start talking about economics.  There are a whole 
bunch of factors that go into what it costs to provide a service, which 
differentiate the costs of upstream versus downstream traffic:

In theory, downstream traffic uses more resources.  Given hot potato 
routing, traffic gets handed off from the sending to the receiving network 
close to the source, and the receiving network pays the cost of hauling 
the traffic over a long distance.  If we could measure the cost of traffic 
purely in bits per mile, upstream traffic would be cheap, and downstream 
traffic would be expensive.

A lot of networks have ratio requirements in their peering policies.  If 
they're receiving more from a peer than they're sending, they threaten to 
depeer.  On the surface, this makes sense.  They're receiving traffic and 
having to pay to carry it, while the other network isn't paying as much to 
hand off traffic locally.  But it leaves content heavy could-be 
competitors desperate for inbound traffic.

Exchange point ports and private peering cross connects tend to be 
symmetric.  If we ignore the longer distances that inbound traffic has to 
be hauled, and the resulting increases in required capacity of inter-city 
backbone links, we can say that the cost of handling inbound traffic has 
already been covered in the course of handling outbound traffic.  There 
may be one too many "if we ignores" in the previous sentence, but there's 
enough fiber in the ground between major US cities (as well as to Western 
Europe and East Asia) that it's pretty affordable.

What's a network desperate for inbound traffic to do?  They either risk 
losing their peering, or they find customers with lots of traffic flowing 
inbound.  When there are lots of networks with this problem, they start 
competing for the inbound-heavy customers.  It's been a couple years since 
I last shopped for inbound-only bandwidth, but at the time the cost for 
inbound-only bandwidth in large quantities in major US cities was rapidly 
approaching zero.  This was putting downward pressure on what those who 
already had balanced ratios could charge, as well.

Inbound bandwidth, while theoretically more resource intensive, was cheap 
or free.  To the extent that the costs weren't just resulting in more debt 
for the transit providers, the outbound-heavy customers were subsidizing 
this.  This meant big price differentials between outbound and inbound 

Then we've got the issues of what gets charged to the users:

In the US, downstream bandwidth doesn't cost much.  End user customers are 
expected to use small amounts of downstream bandwidth.  Billing the end 
users for the bandwidth consumption would cost more than covering the cost 
of the occasional excessive user.  In other words, it is "too cheap to 
meter."  Hosting is a different story.  Hosting customers often use enough 
bandwidth to affect their providers' transit bills, or even to require 
infrastructure upgrades, and the traffic is almost all upstream, the 
expensive direction.  Hosting is almost always billed by usage.

In some other parts of the world, where the ISPs bear the cost of bringing 
their inbound and outbound traffic over expensive connections from far 
away places, the cost model can be quite different.  As the costs of 
transport and transit go up, the costs of dealing with excessive use 
surpass the cost of metering.  There are lots of places where it's common 
to have separate rates for local and long-distance Internet, with the long 
distance connectivity being billed per bit.

We keep being able to push more data through the same fiber, and more data 
through equivalently priced hardware, than previously possible.  But I 
suspect that if traffic patterns were to change and cause the costs of 
dealing with excessive use by US broadband customers to go up 
considerably, we'd see the billing systems change to reflect that.


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