ISDN, I Hardly Knew Ye

Zorin's ISDN Connection: 2000 - 2004 -- R.I.P.


Circuit tag rescued from NID

Cisco 804 - One hell of a nice ISDN router

Westell 2200 DSL Router - Fast, but less blinky-lights!

You probably think it's rather silly to have a web page commemorating a mere ISDN connection. Well, it is! And I had some extra time so I figured I'd do it anyway, since it's so geeky and I'm such a geek.

I was connected via ISDN to the Internet through work from March 2000 until June 2004. You're probably thinking, "Well, they had DSL in 2000, why did you settle for a lousy 128/128?" This would make sense, of course, if not for the fact that my residence is an incredible 22,000 feet from the telco central office. This made installing DSL about as practical as putting a big spool of fiber in the back of my car, tying one end to my mailbox post, and driving to work to plug it into a switch there. Wasn't going to happen!

So when I found out we had a couple of spare un-metered ISDN lines sitting around doing nothing at work, I asked my boss if I could use one for Internet access from home. And he said yes! So I ordered the line from Bellsouth and got things going.

Let me tell you something: ISDN may seem slow, but compared to dialup, it's lightning fast. Most of the reason is due to latency; a dialup connection has between 150ms (if you're lucky) and 350ms of latency on an idle connection. ISDN peaks at around 45ms, slightly longer if it's an inter-LATA call.

Originally my side of the connection featured a work-supplied Cisco 766 router. This router says "Cisco" on it, but doesn't run real IOS. I got tired of it, so I purchased my own Cisco 804 from eBay. This was one hell of a sweet router for ISDN. Not only did it have real IOS, but it also had a feature incredibly important for slow connections: Weighted Fair Queueing. This gives each connected session its own queue so that the connection does not lag during transfers. It made ISDN bearable in a DSL world.

Just a few months ago, the Cisco 804 was thoroughly fried by lightning. This forced me to go back to the Cisco 766, which was a very painful experience. I lost the nice Cisco packet filter, WFQ, syslog, and so on. I then got a little E-mail from Bellsouth saying that "Your line now qualifies for BellSouth FastAccess DSL XTreme service".

Turns out that for about the same amount of money I was paying for my end of the ISDN line, I could get a regular phone line + DSL with 3 MEGABITS of downstream bandwidth, and 384Kbps of upstream bandwidth. This was a "no brainer" to the highest degree. I ordered the DSL, and now have an incredibly fast Internet connection plus a real analog phone line. Viva Bandwidth!

So why the sudden ability to get DSL when I'm 22,000 feet away from the CO? Well, it seems that a couple of years ago, BellSouth installed a SLC about two blocks up the road from my residence. SLC stands for Subscriber Line Concentrator; it's essentially a box where a few pairs of fiber come in, and a few hundred analog phone lines go out. This allows telcos to deploy phone service in dense residential areas more easily, since they don't have to run a copper pair all the way back to the CO for every single subscriber.

However, just because you're on a SLC doesn't mean you can get DSL. A Remote Terminal DSLAM has to be installed at the SLC first. In my case, that RT-DSLAM was installed a couple of months ago, and that's why my location suddenly qualified for DSL.

This is a lesson to some of you out there who may have been told in the past that you can't get DSL; ask again. Call your phone company and find out if you can get DSL; they may not be nice enough to let you know like they did with me. My DSLAM is so close to me that I've only gotten eight CRC errors on my 3000/384 line since I last rebooted the DSL modem nearly two weeks ago. That's pretty impressive for someone who was once 22,000 feet away!

Advantages of each connection type:

ISDN BRI
DSL
  • It's faster than analog dialup.
  • You get two phone lines out of the deal. They can be used for voice or data in any combination.
  • Not many people have it, so it has some "cool factor".
  • It's an educational experience, and fun to play with. You can learn things about the telephone network, like the concept of inter-LATA vs. intra-LATA, D-channels, x.25, and so on. It's like having a digital connection jacked right into the telco switch.
  • Being able to configure your router to make your phone ring busy if the caller ID information matches a specific string. This is very handy when someone is repeatedly annoying you. }:)
  • Caller ID is included standard, and can be logged by the router via syslog.
  • (in my case) Being your own ISP can be cool. I had enable on the routers on both ends, and a /29 subnet. I miss that somewhat on the DSL.
  • It's about 26 times faster than ISDN. (this pretty much overrules everything else)
  • The analog phone line is a true regulated analog phone line, which means it's a lot more reliable than an ISDN provided line.
  • Choice of providers: Now that I have a conditioned pair, I can switch to any DSL provider I want if BellSouth ends up sucking the big one. Hopefully I won't have to, though.
  • Lower latency: DSL first-hop latency is around 9ms. ISDN first-hop latency is 45ms. This means that in general, you will have lower latency to most sites with DSL. This makes Quake III Arena a lot more fun. };)
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