This is a historical page. It was correct when posted in 1998 when we were using ISDN and K-12 Schools were first getting attached to the internet.

Today, public schools in Washington connect through the state K-20 network at speeds much higher than this. Private schools also connect through various ISPs at much higher rates.

University of Washington ISDN Info Sheet
(for NASA K12 project Live from Earth and Mars)

Since US West has altered their rates to provide an affordable ISDN flat rate charge, we have been using dedicated ISDN BRI connections to schools in the greater Seattle area in order to allow them access to the internet and our server. We have chosen to use ISDN BRI for several reasons:

• One BRI offers 128KBS throughput prior to compression while a basic FRAME RELAY (DS0) connection only offers 56K
• One BRI on each side is far cheaper than the combined cost of the 56K FRAME RELAY connection on the school side with a T1 on ours to collect them
• Simple and inexpensive ISDN routers are available.
• The Multilink PPP standard has been agreed upon for ISDN protocol negotiation which enables BONDING (inverse multiplexing over the 2 B channels).

There are three main reasons for using BRI over PRI

• We are providing 128K per school and 1 BRI is 128K. 1 PRI contains 23 B channels and 1 D, which makes 11 128K connections and wastes a B channel. The theory is you can put multiple PRI boxes together so the second one uses 24 B channels and no D channels, but we have not found anyone that has successfully done this.
• 12 BRIs are cheaper than 1 PRI and we do not have to deal with installing any T1 lines.
• The equipment to handle 12 BRIs turns out to be cheaper than the equipment to handle 1 PRI

We currently Digi International retoura ISDN router on both sides. This allows each school to dial up and establish a PPP connection through us using a predetermined line and address range (we like to know who is where). We are routing to subnetted class C's at the schools. So far the routers we have for testing are from Combinet, Ascend and Digi. The Digi comes in a single and dual BRI styles. We use the dula model at our central site with the single version at the schools.

For more information, or to add to our ISDN information please contact David Warren at warren@atmos.washington.edu or (206) 543-0945.

For more information on ISDN in general, as well as lists of vendors please see Dan Kegel's ISDN Page.