Traffic shaping/aggregating

[Ben Scott]

On 12/26/06, Bruce Dawson <jbd at codemeta.com> wrote:
> Although it would make sense that she would use one modem, and I the
> other; it stops making sense when you consider the various (shared)
> printers, file servers and other servers on our LAN that we need access
> to in our daily tasks.

  The simplest way to solve your problem is to put one cable modem on
one LinkSys box, the other modem on a different LinkSys box, configure
the LAN sides of each box with their own IP address, and manually
configure each workstation to use a particular LinkSys box as the
Internet gateway.  It's a kludge, but it works.

  More complicated and somewhat less kludgey would be to use a router
with at least three interfaces: One for the LAN and one for each
modem.  Assign static IP addresses to the nodes you want using a
particular modem.  Configure policy routing and NAT such that those IP
address get routed via a particular interface and address.

  The Linux Advanced Routing & Traffic Control HOWTO at
http://lartc.org/ explains the details.

  One word of warning, last I tried it (on kernel 2.4 a few years
ago), port forwarding via iptables was unaware of policy routing.  As
I recall, port forwarding always ended up using the default tables, or
something along those lines.

> Does anyone know of good reference material regarding "aggregating", or
> otherwise combining the two cable modem's throughput into a single
> network segment ...

  "Aggregation" usually means turning multiple feeds into one, in
particular, such that a single node on your LAN would get twice the
bandwidth, even for a single TCP connection.

  There's no real way to aggregate two consumer cable modem feeds like
that.  The ISP's routing plan doesn't include multiple routes to a
single customer site.  Two cable modems are effectively two different
sites.  They also don't support anything like layer two bonding.

  You can get a form of load balancing on a per-connection basis.
That is, one TCP connection would use one modem, the next would use
the other, and so on.  This has all the same problems as NAT.  It also
does the wrong thing if two existing connections pinned to one modem
start sucking bandwidth.  Prolly not what you want.

-- Ben