[Techtalk] Re: Networking things

[Raven, corporate courtesan]

Heya --

	Doh.  Note to self: read rest of mailbox before writing IP
dissertation.  [grin]  What Kath said.

Quoth Kath (Thu, Oct 11, 2001 at 07:51:47PM -0400):
> A hub works on simple electricity.  Stuff in, stuff out.  It is also called
> a 'repeater'.  It is dumb.

	A hub is a type of repeater, but there are others.  Telco
repeaters to strengthen the electrical signal of T1's every so many
feet.  Optical amplifiers to do the same for fiber circuits.  That's why
you can run a T1 for miles and miles -- every so many feet, you have a
repeater to boost the signal if it starts to attenuate.
 
> This can be used to effectively control network traffic to an extent.  It is
> also more secure than a hub, as a hub repeats all information in on one port
> out to all other ports.  It however will not stop multicasts, because
> multicasts are IP broadcasts and MAC addresses don't matter.  However, newer
> switches can control them.

	Also, layer 2 broadcasts that go to all stations will be
propagated by a switch.  This is why you have to be careful about
connecting switches by more than one port -- they can end up endlessly
propagating broadcasts to each other, eating up all the bandwidth on
your pretty network.  (There are workarounds, though, with Spanning Tree
Protocol.)
 
> I have a feeling switches will totally replace hubs in a few years (This has
> happened on the cable/DSL router level) and for routers and switches to
> merge into one device, which will probably also include a stateful firewall
> inside.

	I could see it.  And you know, you can do all that (and cheaply,
too) under Linux.  Now that Linux is supporting more of the really high
speed hardware, solutions like this are becoming more attractive to
ISPs.  You can make a heavy-duty router/switch/firewall under Linux for
about $1,000 in hardware.  About the cheapest commercial product you can
get with the same functionality is easily three times that.  Now, if the
routing protocol software for Linux improves, we may see it on the
Internet backbone someday soon.  (I don't know of any ISPs that have
Linux routers at their core yet, but it's definitely viable at the
edge.)
 
Cheers,
Raven

"Bless me with your word of savage honor,
 We love more by Fate than by design,
 So give me your hand, and I'll gladly give you my life,
 A flower that sways in the breeze."
  -- the Mission, "Love Me To Death"