Internet Connectivity: More than you Need to Know, but reading through this may save you a few bucks, Part 2
By Roy Cohen
Wire Line and Other Internet Access Services
Last month we discussed internet connectivity, focusing on cable modem service, usually provided by Comcast in the Houston metropolitan area.
This month our focus is on services from AT&T, the incumbent local xchange carrier (telephone company jargon for the primary telephone company in this area for land-line dial tone service).
Beyond dialup service using an existing phone line, AT&T and other telephone carriers began offering ISDN service approximately twenty years ago. ISDN stands for Integrated Services Digital Network. The local telephone operating companies, particularly the Bell companies, marketed it very strongly to business. Some harried IT Directors, resenting the hard sell, jokingly referred to it as It’s Something we Don’t Need. It is a specialized dialup service, offers two 64 kbps channels that can be banded together, providing a 128 kbps channel for digital connectivity. This effectively doubled the speed available through traditional analog modems. Special termination equipment was necessary for ISDN.
ISDN is obsolescent today. It still is used in some areas where more common internet service is not provided.
In the spring of 1999, DSL (Digital Subscriber Line) service was introduced to Houston. Typical residential DSL from AT&T is ADSL for “Asynchonous” DSL. As mentioned in the article on cable modems, ADSL also provides higher downstream speed or bandwidth (incoming to you) than upstream (outgoing from you). Thus the “Asynchronous” moniker.
The convenience factor for DSL is awesome. If you have a phone line, it is highly likely that you can get DSL service. You see, DSL travels over that copper pair of wires that come from the telephone company’s central office, all the way to the telephone on your wall or desk. Normally a traditional copper telephone line has two kinds of electricity on it. The main type is reasonably low voltage direct current. The phone company calls it “battery”, and it carries voices back and forth. The circuit also can carry higher voltage, which makes the ringer ring on your phone.
The late, great Bell Labs figured out how to super-impose a radio signal on those two copper wires coming to your premises. That radio signal is a high frequency alternating current signal. It carries the digital bits of data communication, and it does it at reasonably high speeds. (Ever wonder why you have to have a DSL filter on a phone line before you plug the line into a phone jack? Without it, the DSL signal gets into your phone and makes horrendous noise.).
A major advantage of DSL is that its speed while traveling to and from your telephone company is consistent. This is because unlike cable modem service, DSL is NOT shared with other consumers, as your phone line isn’t shared. Neighborhood teenagers downloading music and video at 4:30 in the afternoon will not impact the speed of your service.
DSL poses some significant challenges to the telephone company and to users. DSL is distance sensitive. Its speed is inversely proportional to the distance from its “head end” which the telephone company calls the DSLAM. (Pronounce “Dee Slam”). That is, the farther you get from the DSLAM, the slower the speed. The maximum distance DSL may operate is approximately 18,000 feet (3.5 miles) from the DSLAM. This was problematic at the time because telephone company exchange offices (wire centers) aren’t just found on every local street corner. So what did the phone companies do? They installed DSLAM’s in small remote sites, far closer to their customers. This partially solved the distance/speed issue.
DSL also has to have a very clean, clear copper circuit path to function well. Many telephone company legacy circuits have devices in them that interfere with this direct connectivity. “Loading coils”, amplifiers, and other devices have to be removed from any copper line circuit of a line provisioned (again phone company jargon) to be used for a DSL subscriber line in order for it to work. Corrosion is another issue in older neighborhoods. Copper cable has hung on AT&T and Verizon’s phone poles often for decades, and splice points tend to corrode. It isn’t necessarily a problem for a voice call, but easily interferes with the DSL signal.
DSL requires a “DSL modem”, just as cable requires a cable modem. You usually are required to purchase the DSL modem. It generally comes with a phone line extension splitter adapter, with the male end plugging into the phone jack in the wall, and the other end offering two female jacks, one for the DSL modem, and one for a telephone. Again, that telephone MUST have a DSL filter on its line, between it, and the female jack of the splitter adapter. A phone is not required to be plugged in to the adapter.
DSL speeds have limitations. Higher speeds and synchronous DSL are possible at premium rates. Generally, cable modem service speeds in Houston tend to be faster dollar for dollar.
So that’s the DSL offering from AT&T, Verizon, and other wire line telephone company service providers.
About four years ago AT&T began rolling out its “U-verse” combined video, voice, and internet service. U-verse service is delivered to a neighborhood area via fiber optics. Fiber optics is capable of fantastic speed/bandwidth, and is not subject to electromagnetic interference. Fiber optics is simply laser light transmitted through a clear glass fiber. Once the signal reaches a neighborhood serviced by AT&T, the signal is routed over the existing telephone line, to the customer premises via DSL. Yep. That’s right. DSL! Only in this case at a far higher speed than consumer ADSL. It’s called HDSL.
So when a tv in a U-verse customer home tunes in a certain program channel, ONLY that channel is fed down the phone line via HDSL from the fiber optics. This is different from cable tv, where all channels are on that cable in your house, all at the same time. Your cable box simply picks the one you call for. There is a limit to the number of tv’s you may have on the U-verse service, as too many demands for programming over the HDSL will bog it down. However, U-verse equipment will allow you to record 4 different concurrent video programs, while Comcast’s service allows for only two on a DVR.
U-verse offers speeds comparable to cable modem service. Like cable service, it may be used to carry voice, video, and data and is offered as a bundle. U-vrse terminating equipment includes a central terminal, a “2 Wire” brand router, and associated video boxes for each tv. It also includes a stand-by battery because there is no “battery current” associated with the telephone voice service. The phone calls use internet protocol data packets similar to internet data you utilize when you surf the web.
The Achilles heal of U-Verse is its reliance on DSL technology for “last mile” to your house. Many of the same issues that plague plain vanilla DSL also can plague U-verse. However, the physical portion of the service that is DSL is far less than standard ADSL.
Verizon, which does NOT serve much, if any of the greater Houston area, offers a service called FIOS (pronounced “FEE Awes”). FIOS is far superior because Verizon has chosen to eliminate copper circuits from its service. Verizon is bringing fiber optics all the way to the customer premises, eliminating altogether, any DSL segment (with its accompanying drawbacks) from the architecture.
That’s it for wired internet service access in the greater Houston Metropolitan area. However, internet may be accessed via “hotspots” provided by cellular service. Hotspot devices are available from your carrier, and some “smart phones” may be equipped to generate wi-fi hotspots.
That’s it for our series of articles on internet service connectivity!
U-verse is a registered trade mark of AT&T. FIOS is a registered trademark of Verizon, Inc.