SlashDot: "Comcast Gunning for NAT Users"

Daniel Senie dts at
Thu Jan 31 18:24:17 UTC 2002

At 12:15 PM 1/31/02, Daniel Golding wrote:

>Hmm. I doubt Comcast is actually doing this - they are far too busy actually
>trying to build a network, out of the ashes of the @home debacle. However,
>even if they were, there isn't really anything wrong with it. We scratch our
>heads, collectively, when a large broadband provider goes chapter 11, but
>then oppose a pricing model that might be profitable. Now, if a provider was
>refusing to provide extra IPs, then I could see the problem. However, if a
>provider is willing to provide extra IPs for something reasonable like
>$5/month, more power to them. There are several good reasons why they might
>want to ban NAT:
>1 - When you come to the stadium, you can't bring in your own hot-dogs. It's
>the same sort of thing - the hot dogs are subsidizing the ticket price. In
>this case, extra fees for things like IP addresses and extra email boxes,
>are the concession items.
>2 - Support issues - supporting a largely clue-challenged user base, is hard
>enough without people slapping linksys routers in, then expecting the ISP
>to, defacto, provide support. Anyone remember when the only supported router
>for UUNet ISDN lines was the Pipeline 50? This was to (in theory) enable

Especially considering the clue-challened support departments at Cable 
ISPs, this is a legitimate problem.

Newer Linksys and similar routers can spoof the MAC address of the PC 
that's behind them as a way to avoid having to tell the cable company about 
the new "computer." Connected backwards, the Linksys routers appear to 
merrily spoof the default gateway off the segment (i.e. most likely the 
first MAC address the box hears) and create lots of support headaches.

>3 - NAT is wonderful, but we aren't running out of IP addresses that
>quickly, and NAT will break some applications. Large scale NAT is probably
>not the solution to future IP address exhaustion problems. Providers who do
>this are not being bad guys, because extra IP addresses cost less than the
>costs of supporting NAT boxes. If folks don't like this, they can become
>involved with ARIN and propose some bizarre price-support scheme for IP
>addresses, to encourage NAT, I suppose.

Well, NAT saves the cable company from having to route subnets. ATT 
Broadband in Massachusetts is now offering "business" service. Reading the 
fine print, they provide a NAT router, and say you can have up to 253 users 
behind it. Of course any apps that wouldn't work with NAT will not work.

As such, clearly they DO support and/or allow such use of routers. 
Actually, they've been doing this for a long time. They supply cable 
service to many schools in the area, and those are all supported using NAT 

>4 - This is, of course, an unenforceable policy (which is why I suspect it
>does not exist). However, it is very reasonable for a provider to refuse to
>support a customer with a NAT box, if the customer is buying a single user

Support is one thing. Trying to detect the presence is another entirely. 
Wasting time, effort and money trying to track down users who're using 
"cable routers" is looney.

Daniel Senie                                        dts at
Amaranth Networks Inc.          

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