routers vs WAN vs T1 vs dialup

[ewhorne at mindspring.com (Bill Horne)]

Glenn Burkhardt wrote:

> Can I have some help with nomenclature?  I'm looking into getting a T1 line
> into the office to replace our local telephone lines and dialup ISP connection.
> The T1 line Internet connection is "V.35", which looks to be a high speed
> HDLC serial connection (??).

V.35 is the standard physical connector spec for T1 lines connecting to Channel
Service Units (CSUs) at DS1 rates. Although you may choose to send HDLC packets
over a DS1 line, you don't have to: the T1 line is a 1,544,000 bps pipe that
doesn't require (subject to a ones-density restriction) any specific Link Layer
protocol.

> We currently have a single dial up line with a static IP address assignment
> on a Linux box that performs IP masquerading for all the other computers
> in the office, and works as a mail server.
>
> The guy at Net2000 said that I needed a Cisco 1720 router for the
> Internet connection.  But isn't a router just a Unix box with a communications
> interface that's connected to the Internet?  So isn't my existing firewall
> a "router", even though it uses PPP demand dialing to connect?

You need not only a router, but also a CSU/DSU (to connect to the T1 line). The
1720 also include one 10/100 Ethernet port, management software, and other nice
features: other Cisco products have a hub or switch built in.

The Cisco 1720 info is at http://www.cisco.com/univercd/cc/td/doc/pcat/1720.htm#ov.

> [snip] Is it really this simple?  What have I missed?

Nothing; it's a question of convenience and maintainability.  The Cisco's are
reliable, well known, widely available on the secondary market (~$600 on ebay)  and
easily repaired, so I recommned one for a "first time" buyer.

That said, I'll also recommend against a T1 line:  they're too fast for most small
offices, and put all your eggs in one basket.  You'd do much better to pay for two
** DIVERSE ** SDSL circuits, even if it means having a new cable run into your
building from a different street.  Sooner or later, someone's going to run a
DitchWitch through your T1 circuit, and you'll be dead in the water.

HTH.  YMMV.

Bill Horne
(These are my personal opinions only.  I do not speak for my employer.)

-
Subcription/unsubscription/info requests: send e-mail with
"subscribe", "unsubscribe", or "info" on the first line of the
message body to discuss-request at blu.org (Subject line is ignored).