DSL Comes to Munisingby Jonathan Gennick
The DSL industry may be in a state of meltdown, but here in Munising, Michigan, population 2,539, DSL is alive and well. Last month, a Hiawatha Telephone Company technician came to my door and personally asked me if I would be customer #1 for their new DSL service.
I couldn't resist his offer. Last fall I networked my house and installed cable Internet service. Now I had the chance to lay in DSL service too, see what it was all about, and compare it with cable. The really cool part about all this is that I was able to arrange a tour of the phone company's central office to see how DSL works on their end.
Read Jonathan's earlier series of articles, Installing a Home Network.
Getting the Line
I've heard a lot of horror stories about confusion and delays in getting DSL installed, but I don't have one to offer. I talked to the phone company on a Wednesday, and on Thursday morning a phone company person was at my door to do the install. The first thing he did was to install a new network interface device (NID) on the side of my house where the phone line comes in from the pole. That NID contains modules to split the voice and data portions of my incoming line (Figure 1).
This wall unit cost the phone company about $45.00, and from the
technician's perspective, it is the easiest way to handle the problem of
splitting the ADSL and voice signals. Figure 2 shows some other
multiplexing solutions. If you go with one of the solutions shown in
Next, the technician ran Category 3 twisted pair cable from the ADSL
During the testing phase, the technician at my house was on the phone (using my non-DSL line) with another technician back at the telephone company office. One of these test units was placed at each end of the line that they were testing for DSL. My line tested out at 1,536 kbps downstream from the central office to my house, and 512 kbps upstream. These represented the advertised maximum speeds. Once everything looked good, they connected the end of the line in my house to my DSL modem and connected the other end to the DSL equipment in the back office.
Connecting My LAN
With the DSL line itself in place, my next task was to connect it to my personal LAN. This is where the patch panel and router, which I installed last fall, really came in handy. I have several computers in the house, and I wanted to keep at least one computer running on my cable Internet connection so that I could compare the performance and reliability of cable versus DSL. The patch panel allowed me to do that easily. I choose to keep my wife's computer on cable to insulate her from any potential glitches that might occur with the new, and as yet untested, DSL service. To accomplish that, I unplugged the cable modem from my router, and plugged it into the patch panel jack that led to my wife's computer. Then I plugged the DSL modem into my router.
Figure 4 shows the DSL modem and the rest of my equipment. To protect my wife's computer while it was connected directly to the cable modem (no router/firewall anymore), I downloaded and installed a copy of Sygate Personal Firewall.
One aspect of DSL I found to be different from cable is the mechanism for establishing an actual connection to the Internet. With cable, I power up my router, and it uses DHCP to get an Internet address from the cable company. At that point, I'm connected and can pull email, download Web pages, and so forth. DHCP is standard stuff, and it's what I'm used to using in any typical business setting. For reasons I have yet to understand, DSL connections are made by simulating a dial-up connection over the DSL line.
Typical dial-up connections are established using a protocol known as Point-to-Point Protocol, or PPP. When made over an Ethernet link rather than a dial-up line, the protocol used is Point-to-Point Protocol over Ethernet, or PPPoE. Normally, the phone company installs software on a customer's computer in order to make such a connection. Fortunately, my router, a UGate-3200, supports PPPoE directly. So rather than install PPPoE software on each of my computers (something I really didn't want to do), all I had to do was specify the PPPoE connection settings on my router's configuration screen (Figure 5).
The Connect button allows me to initiate the PPPoE connection manually, but the router will also initiate one automatically, on demand, whenever one of my computers attempts an outbound connection to a Web server, email server, or other Internet service. When I had these settings correct, and the connection established from my router, I simply rebooted my computers so that they would pick up the proper DNS server settings from my router, which acts as a DHCP server to my LAN. I have one server with a static IP address (on my side of the router), and for that machine I needed to manually change the DNS server addresses.
Another aspect of DSL that differs from cable Internet service is that with DSL you deal with an Internet Service Provider (ISP) that is separate from the phone company. With cable Internet, the cable company provides the physical connection and also serves as the ISP, so you tend to perceive only a single entity. That's not the case with DSL. My DSL line (the physical connection) is provided by Hiawatha Telephone Company, but my actual Internet service is from an ISP, Jamadots.
The Back End of All ThisHow does all this work on the back end? I was very interested in finding out, and the phone company was kind enough to arrange a little tour for me. To begin with, Internet service comes into the phone company's central office over two T1 lines (two for redundancy). These lines are provided by Ameritech and AT&T, and they connect to an ISP in Atlanta, Georgia. The two T1 lines plug into the back of a Cisco 3600 router (Figure 6).
The next piece of equipment on the connectivity path is a Redback Networks Subscriber Management System (SMS) 500 (Figure 7).
During the tour, I failed to get a clear explanation of just what this unit did. So, being a curious soul, I went to Redback's Web site. There I learned that the SMS 500 "grooms the [network] traffic for a service provider's backbone routers", "provides customer touch functionality", and "bridges the operational gap between high speed access equipment in the telco central office and service provider backbone routers." All these explanations were very unsatisfying--I don't know what it means to "groom" network traffic--and I wonder why Redback can't clearly explain in a couple of paragraphs just what this unit is all about.
I was able to figure out that the SMS interfaces with an authentication server to authenticate DSL subscribers when they connect to the system, hands out IP addresses, and manages the services the phone company chooses to deploy over the DSL lines. The Redback SMS is connected to the router via ethernet.
The next stop on my little tour was a DSL MultiService Access Platform, model DMAX 1120, made by Advanced Fiber Communications (AFC), Inc. This is the device to which I am more or less directly connected, and it's connected to the Redback SMS via a T1 line. The DMAX 1120 (Figure 8) combines my plain old telephone system (POTS) service with my Internet service, and it sends them both out over the same physical wire to my house.
The DMAX 1120 consists mostly of a series of cards mounted vertically in its frame. Most of cards work in pairs, and each can handle up to six physical lines. Six POTS lines are connected to the leftmost card in this photo. Six DSL lines are connected to the adjacent card. The phone company can specify via software which POTS line gets multiplexed out on which DSL line. The two cards that are somewhat isolated in the middle of the unit manage the connection to the Redback SMS 500. The Internet service comes in on those two cards and is multiplexed out on the DSL lines along with the POTS service.
If you're familiar with DSL terminology, you may have heard the term DSLAM, which is an acronym for Digital Subscriber Line Access Multiplexer. The DMAX 1120 incorporates the functionality of a traditional DSLAM, and also incorporates additional functionality designed to make it easier to deploy DSL to subscribers beyond the reach of the central office. At least, that's what the manufacturer says on their Web site.
My DSL line comes out of the DMAX 1120, and it connects to a terminal block on one side of a Main Distribution Frame (MDF). The terminal block (Figure 9) is nothing more than a gray box with terminals for attaching wires.
You could think of the MDF as one giant patch panel. It's used to make the physical connection between the line leading to my house and the line coming off the phone company's DSL equipment. Figure 10 shows the other side of the MDF.
A small patch cable running between the two sides of the MDF connects the line leading to my house to the appropriate line coming off the DMAX 1120.
Static IP Addresses
I know many people are interested in getting a static IP address when they get broadband to the home. I am too because I like the idea of running a low-volume Web server from my home. I'd learn a lot, and I'd be able to experiment with different types of back-end software ( Oracle9iAS Portal, for example). During my tour, I took the opportunity to ask about getting a static IP address. The short answer was "No", but the long answer turned out to be rather interesting. I need to refer you back to the Redback SMS 500 unit and specifically to the four ports that I've zoomed in on in Figure 11.
The SMS 500 is responsible for handing out IP addresses to DSL subscribers when they connect to the system. It can be configured to hand out either dynamic or static IP addresses, but that configuration is done on a port-by-port basis. The port you see used in this photo handles all DSL subscribers within the Munising city limits. The other three ports are reserved for remote sites in the nearby cities of Wetmore and Christmas and in the 16 Mile Lake area.
In order for the phone company to provide an option (even an extra-cost option) to have a static IP address, they would need to buy another card with four slots, configure those slots to hand out static IP addresses, and connect those customers willing to pay extra for a static IP address to that card. The market in Munising for static IP addresses probably consists of only one or two customers. I'm not sure what these SMS 500 cards cost, but it's probably not cost-effective for the phone company to buy one just to serve one or two people. In any case, it's interesting to understand the phone company's perspective on the issue.
DSL Versus Cable
Bottom line, how does DSL compare to cable? Which of the two services am I going to keep once this trial period ends? For configuring my home network, the biggest difference between DSL and cable is that DSL uses PPPoE while cable uses DHCP. Usually this means that PPPoE software must be installed on each PC, but fortunately I was able to configure PPPoE in my router and avoid having to reconfigure all the PCs on my LAN.
Speed: Which is faster, DSL or cable? I ran a few speed tests using the speed test tool at the DSL Reports site. The download speeds for both cable and DSL were all over the map. I got different results at different times of the day, and sometimes I got different results from two tests run within minutes of each other.
Such erratic results are typical, because what I was really testing was the speed at which I could transfer data from some site on the Internet all the way on the other side of the country. The results probably depend as much on the vagaries of Internet traffic in general as on the speed of my own connection. In any case, I didn't see that either service had any clear advantage in terms of download speed, and subjectively, I can't tell the difference between the two.
Upload speed is where I do notice a clear and consistent difference between the two services. Upload speed on my cable service was always in the low 200 kbps (kilobits per second) range. DSL doubled that, consistently yielding upload speeds in excess of 400 kbps.
Service: I have to give the phone company the nod here. Once I get a person out to my house, I get excellent service from both providers, but dealing with the companies via phone is a different story. Navigating the cable company's automated switchboard system has always been a trial for me. With the phone company, however, I've had no trouble getting through to knowledgeable people.
Coverage: The phone company has the edge here, as well. I live in town, so coverage isn't an issue for me, but I have plenty of friends in outlying areas where there are no plans to run cable. The phone company currently runs fiber to within 12,000 feet of most subscribers, and it will be able to offer DSL to those subscribers as soon as they can get the equipment in place. Figure 12 shows a simplified view of the phone company's network topology.
All this gets me back to the question of which service I'm going to choose in the long run. I'm going to duck that question because I haven't decided yet. I'll keep DSL for another month and see how I feel about it then.