time for the annual Internet Speed Quest

[Ben Scott]

On Sun, Jul 6, 2014 at 2:05 PM, David Rysdam <david at rysdam.org> wrote:
> It's sounding like the upshot is that I should try comcast.

  Of those two, I'd much rather have Comcast than FairPoint.

> What does the cable modem consist of? From a black-box POV, I assume
> it's basically identical to a DSL modem. Magic on one side, CAT5
> ethernet on the other. Plug my tomato-powered wireless router into that
> side and away I go.

  Pretty much.

  Gory details:

  Most DSL systems function like a high-speed serial line, and run
PPP.  The CPE (Customer Premises Equipment (the so-called "modem"))
may act as a router, terminating the PPP link, and providing an IP
interface on the Ethernet port.  They'll often force NAT in this mode,
since that way the ISP doesn't have to give you valuable public IP
address space.  Alternatively, the CPE will forward the PPP frames
over Ethernet (PPPoE), and it's up to the customer to to provide a
router to terminate the PPP feed.  This lets the customer have access
to the public IP at the end of the PPP link, which is nice for geeks
who want to run their own router anyway.

  Coax operates more like old-school 10BASE2 Ethernet, with a bunch of
nodes on a shared bus.  The CPE ("cable modem") functions like a
bridge.  Customer plugs into the Ethernet port, does DHCP, and gets an
IP address that way.  Rather like plugging into your home LAN, except
it's Comcast's DHCP server, instead of yours.  Most cable operators
limit the customer to one MAC address, so if you want more than one
node, you need to provide your own router, and do NAT.

-- Ben