Newsletter

These articles written by Andrew will be presented on a rotating basis.

DSL - Myths and Facts - "Can you get there from here?"

In a familiar irony, one of the newest technologies in telecommunications is based on one of the oldest. Digital Subscriber Line (DSL, or ADSL, or SDSL, or XDSL, take your pick) can provide fast, inexpensive data communications. DSL lines are what old time telephony jocks call 'dry pairs', telephone lines without any telephone service (no dial tone). Dry pairs have been around since the beginning days of telephones, back when Timmy's mother used to turn the crank to ring the operator. They were used almost exclusively for alarm circuits and cost almost nothing to install and used month to month.

Well, it's now 1999 and Timmy is now a database programmer in Santa Monica, and some clever engineers have found a new use for dry pairs. By installing some very expensive equipment in the telephone company's local switch facilities and selling you a special type of modem, you can have a connection to the Internet five, ten, as much as twenty times as fast as a normal modem.

Variations of DSL

There are several variations of DSL. ADSL is asymmetric, as with cable modems your download speed is ten times faster than your upload speed. This is fine for most users as most of us spend far more time retrieving email and viewing web sites than we spend uploading information from our computers to others out on the Internet. The major exception to this rule of thumb is if you are running a web server of your own. SDSL is symmetric, the speed at which you download is the same at which you upload.

The cost?

The cost is a few hundred dollars for the line installation and modem and anywhere from $80 to $400 a month, depending on how fast you line is.

What's the catch?

There are two things to watch out for. The first is that DSL is not yet available in many places, contrary to what the salesperson is telling you. It costs money to put those expensive boxes into each local Pacific Bell office and the DSL companies are very selective as to where they place them first. San Francisco has DSL coverage, as does Oakland and most of San Jose. Most of the peninsula is covered at least on the bay side, as is Santa Clara. After that things get spotty. Many cities are listed as Real Soon Now, as they have been for close to a year. When a DSL salesperson tells you that it is available for your town, ask for the name and telephone number of at least one customer in the same physical area you can contact as a reference.

Problems

The other problem with DSL is that the speed you can expect is dependant on the distance between you and the local Pacific Bell office. While the telephone company measures distance for tariffs and local call coverage 'as the crow flies', for the purpose of DSL it is measured in actual feet of copper wire ('copper in the ground'). If there is less than six thousand feet of copper wire between your location and the local telephone facility, you can get fantastic speeds, rivaling the much heralded cable modems. If there is between six and twelve thousand feet you speed will range between 56kb and 384kb per second. Beyond twelve thousand feet, DSL may not work for you. The exception to this is IDSL where the maximum rate you can get for upload and download is 144kb but the copper in the ground can run as far as 36,000 feet.

Is DSL appropriate for you?

First find out if it is available at your location. Again, don't depend on the glossy brochures or the salesperson to tell you. Talk to a real user down the street from you. Second, find out what speed your access can be. DSl is a remarkable combination of old and new technology and for some users it can be the best solution for connecting to the internet.

Combating Electronic Junk Mail - "Help, we've been spammed!"

The thrill of receiving electronic mail diminishes in direct proportion to the amount of junk email we receive. "Spam*" mail, as it is known, has grown to mammoth proportions, causing annoyance to email users and major headaches for system administrators. "Sorry, we do not relay" has become a common error message as email servers are fortified against spam mail floods. Spam merchants, rouge Internet companies that cater to the junk mailer, seek out unsuspecting and unfortified email servers and when one is found, exploit their weaknesses. It is not uncommon for a spam merchant to forward half a million spam mail messages through a third party email server in one night. This much traffic will bring many servers to their electronic knees and cause enormous complaints as the spam is received.

A Brief History of Spam

Part of the problem is caused by the way the Internet was developed. Electronic mail was the first application of what became the Internet, people have been sending email since 1969. Until recently, email servers, large computers with lots of disk space and lots of horsepower, have been open and friendly to all. If an email server received a message addressed to someone not associated with that organization it would forward the message on to an email server further down the Internet to see if they could handle it. The sending and delivery of electronic mail was seen as a cooperative venture where everyone helped one another.

The sudden explosion in Internet commerce changed all that. The first true spam came a few years back when a lawyer sent email to tens of thousands of Internet newsgroups (similar to bulletin boards) offering help in obtaining immigration green cards. The many readers of scientific news groups where discussion of esoteric topics such as the human genome project take place where less than thrilled to have the sanctity of their domain violated. The readers of newsgroups pertaining to countries other than the United States were no less thrilled, solicitations for assistance in obtaining a U.S. green card was meaningless. But Pandora's box had been opened and soon after countless others began sending unsolicited email by the thousands.

Today, there are a dozen or more software packages available that advertise the ability to send email to literally millions of unsuspecting users.

As the problem of spam mail became a plague, the system administrators of email servers scrambled to find ways to combat it. Many began refusing to accept any email at all from companies know to be the worse offenders, the most notorious of these was cyberpromo.com. Unfortunately, because email servers were designed to relay messages automatically, the spam merchants learned to disguise the origin of their message by passing them through an innocent third party email server. The addresses of email servers willing to relay are routinely distributed amongst the spam merchant community.

Combating Spam

The way to combat spam is to lock down your email server so that unauthorized email cannot be relayed through it. This is an unfortunate change in the way the Internet works, but spam has made it necessary. Depending on the email server software, this can be as simple as clicking a button or it can be extremely complex. Once the server has been locked down, problems start popping up. Typical are the users who send and receive their email through the server, yet use a different domain name that that of the server's. These users will receive the 'Sorry, this server does not relay' error message. When that happens, they either have to find a more appropriate server through which their messages should be sent, or the system administrator has to loosen the security on the current email server just enough to let their messages through.

Is your email server vulnerable to the spam merchants? Give us a call at (510) 656-1773 and we can take a look.