Alternatives to Comcast

[Ben Scott]

On Wed, May 21, 2008 at 4:34 PM, Thomas Charron <twaffle at gmail.com> wrote:
>  Right off the bat, communications overhead, simply due to the
> encapsulation.

  Covered in my message to Tom Buskey.  It's always there.

> Additionally, you're generally PPPoE into a machine,
> handling beelions of other PPPoE connections.

  Ummm... what the heck do think is at the other end of the DSL line
but "a machine"?  The Internet isn't an actual "cloud", despite what
network diagrams show.  There really is some equipment involved.  Some
carriers terminate DSL into something like a router immediately, but I
believe Verizon's stuff generally goes into an ATM network first.  So
your frames float around in that before getting to something that
speaks IP.

  If what you see from your "modem" is PPPoE, then what happens is:
Your PC builds an IP connection over PPP.  It puts the PPP frames into
Ethernet frames and sends them to the modem.  The modem takes the PPP
frames off Ethernet and puts them in ATM frames and beams them over
the wire.  At the DSLAM, the ATM frames go into whatever equipment
Verizon has until they get to the IP provider.  The IP provider takes
the PPP frames out of the ATM frames and does IP routing with them.

  If what you see from your "modem" is IP-over-Ethernet (RFC-894),
then the "modem" is either doing PPP termination locally and acting as
a router, or it's encapsulating IP datagrams in ATM frames.  (Some
implementations are worse, and encapsulate the entire Ethernet frame
in the ATM frames.)  If the former, from the modem onward it's the
same as for the PPPoE drill above.  For the later, the encapsulated
frames get to the IP provider, are dencapsulated, and then handled
appropriately.

  Vitts Networks was one of the providers doing the "worse"
Ethernet-over-ATM scenario I describe.  Their DSL "modem" was
basically just an Ethernet bridge.  In the CO, they had boxes which
basically took DSL on one side and spit Ethernet out the other.  Then
they'd patch each Ethernet port into a managed switch.  So now instead
of running PPP over the serial DSL, you're running an emulation of
broadcast-based Ethernet, which actually had *higher* overhead than
PPP would have.

> This means that your packets are going thru a peice of software, and not being
> routed by hardware, and least between you and your ISP.

  Um, yah.  There's no such thing as hardware without software, or
software without hardware.  That's a bogus argument put forward by
people trying to sell routers.  IOS is software.  Linux is software.
My PC is hardware.  A Cisco 2600 is hardware.  Where and how it's done
doesn't matter, so long as adequate capacity exists and the
implementation is stable.  (That's a big "if", of course.  Especially
when Verizon is involved.)

> Additionally, your PPPoE connection will occasionally need to be dropped and
> reconnected for one reason or another, causing occasional 'blips'.

  My cable modem needs that, too.  That's because most CPE is cheap
and isn't designed with self-healing capabilities, not because of the
protocols involved.

-- Ben