Volume 18, Number 8
YOUR COMPUTER NETWORK
What's best for your firm?
By Christopher Heitman
I recently met with two well-dressed lawyers in a beautiful, wood-paneled library filled with all the reference material that a law office requires. The two lawyers were the co-managing partners of a 25-lawyer firm.
The first words out of one gentleman's mouth were, "Can you really get us broadband service?" After I confirmed my claim, he proceeded to gesture to the beautiful bookcase. "You see these books?" I nodded. "They are for show. We get almost all of our case law and research from the Internet, and we are damn tired of waiting for our information to download!"
In discussing the best broadband service solution for your firm, first you need to understand the products and delivery technologies available. Figure 1 gives some examples of speed and applications.
- kbps. Speed in thousand bits per second. Modems and DSL lines are sold by their raw kbps speed.
- Green indicates various popular speeds in use on the Internet, for comparison.
- Grey (after green bar) indicates transmission overhead (assumption 13 percent for DSL lines; other broadband may have different overhead).
There is no doubt that speed is the future of the web, the Internet, and private intranets, and the primary competitive systems in these markets are cable service modems and DSL.
Fiber optics offers among the fastest speeds available but requires significant infrastructure investment. It's also hard to deliver because of right-of-way issues, construction, and limited return on investment. It is, however, a preferred method of broadband delivery in new construction and for so-called backbone loops. The FCC predicts that by the end of 2001, more than 15 million users will connect to the Internet with DSL-type speeds.
DSL offered by telephone companies and their ISP resale distribution channels. The cost ranges from $39.95 plus line charges per month for ADSL to $150 to $600 per month for SDSL at speeds of 144 kbps to 1.5 mbps, respectively. ADSL (Assymetric DSL) means that one way is faster than the other. SDSL (Symmetric DSL) means that both ways, up and down, are equally fast. Running on the existing in-building copper network is an efficient, low-cost way to provide high-speed access, but it's limited to subscribers who reside 15,000 to 18,000 feet or less from the telephone company's Central Office (CO). DSL prices have fallen as a result of the Incumbent Local Exchange Carrier's (ILEC) powerful entrance into the market in 2000, and have stabilized at about $95 per month for business service. (Examples of ILECs include PacBell, Verizon, and other regional Bell companies.) Most experts agree that DSL will surpass cable modem service by 2002.
Cable modems are fast but subject to oversubscription slowdown because the bandwidth cannot be controlled. As more users go online, the bandwidth available is proportionately reduced. Business rates are generally $1,400 per month plus a $150 setup fee. While cable has a large residential installed base to work from, delivery to businesses is almost nonexistent. Cable modem service is now available to some 32 million North American households, or about one-third of all cable subscribers. More than 1 million households in North America have cable modem service.
High Earth Orbit Satellite (HEOS) offers an opportunity in underserved markets similar to fixed wireless broadband (FWBB), but it has limitations. The largest HEOS is HughesGM-owned DirecTV, which offers the service at a maximum of 400 kbps burst speeds. The technology has a 500-millisecond latency problem that cannot be overcome and the service currently requires a wired upload, increasing costs and limiting the upload to 56 kbps. There is a promise for upload capability without wire connection in the near future but at what speed is uncertain. This technology, though promising, still lacks the flexibility and bandwidth requirements to meet many customers' expectations.
The latency issue is a problem that physically cannot be overcome because transfer rates are limited by the speed of light carrying the data to the high earth orbit of the satellite, which takes 500 milliseconds. Voice traffic, considered the next "killer application" on the Web, can tolerate a latency of no more than 150 milliseconds. As a result, callers using HEOS transmissions will "step on" one another's conversations. Consequently, HEOS systems are out of the race for convergent systems.
Fixed wireless broadband is point-to- multipoint radio frequency. This option offers fast deployment, stability, and reliability of service with bandwidth allocation control not available to DSL and cable subscribers. Averaging 144 kbps (five times faster than dial-up), the cost starts at $39.95 per month for the residential user and $109.95 per month for the business user. The average charge is $133.95. The service is supported by the local ISP and can deliver speeds of up to 100 mbps for backbone at 5.8 MHz and 2 mbps at 2.4 MHz. Table 1 highlights the various costs and characteristics of these technologies.Table 1 Service Speed Install Availability Performance Cost Monthly Fixed Wireless Broadband 64 kbps to 1 mbps 3-5 days 70% of target market Dedicated or shared access with bandwidth allocation $139.99 plus equipment to $459.99 ISDN Residential or Business To 128 kbps 30-60 days or more 6 miles from CO Dial-up access $125 including line charges T1,T3,DS1,DS3 Business To 1.5 for T1 and DS1 to 45 mbps for DS-3 and T-3 30-60 days or more Universal Dedicated access $1200-$2500 for T-1; $21,000-$28,000 for T3 and DS-3 SDSL Business 64 kbps to 1 mbps 30-60 days or more 18,000 feet from CO Dedicated access $200-$800 Cable Modem Busines 10 kbps to 10 mbps 10-45 days or more Very limited areas Shared access with no bandwidth allocation $129-$150 Source: www.DSLReports.com, 1-09-01; CO = telephone company central office
We all know that in all businesses, the bottom line is the bottom line. In the law profession, as in most other professions and businesses, time is money. Table 2 shows how various connections translate into time. As you can see, the speed of the connection significantly affects the time it takes to accomplish a task. DSL and cable modems are fast, much faster than dial-up modems. If you haven't played with a DSL line before, then they are faster than you've imagined them to be.but are they as fast as the ISP or telephone company is telling you they are?Table 2 Technology Classification Symmetrical Speed(s) Time to Download Two-Minute Video Clip 14.4K analog modem Narrowband Yes 14.4 kbps 5 hours 56K analog modem Narrowband Yes 56K kbps 1.25 hours ISDN Narrowband Yes 128 kbps 30 minutes ADSL Broadband No 128 kbps - 384 kbps 20 minutes Satellite Broadband No 384 kbps 10 minutes SDSL Broadband Yes 384 kbps - 8 mbps 30 seconds Cable Modem Broadband Yes 128kbps - 1.5 mbps 30 seconds Fixed Wireless Broadband Yes 128kbps - 1.5 mbps 30 seconds Source: www.DSLReports.com, 1-09-01; CO = telephone company central office
How are high-speed lines sold? High-speed lines, in the tradition of modems, are sold in kilobits per second. Two speed quantities are named: download speed and upload speed. The ISP will put more emphasis on download speed, sometimes not even mentioning upload speed at all, as if that side of the twisted pair is inconsequential to you. In fact, upload speed can be a critical part of the performance puzzle. The typical speed quote comes as a three- or sometimes four-digit number, often with the same or a smaller number alongside it. This is a kilobit-per-second speed rating.
How do kilobits per second translate to speed? Browsers and other file transfer agents tend to show speed in terms of kilobytes per second, usually with one or two decimal places. Thus, you may see your browser report a transfer rate as "XX KB/Sec" (along with the flying paper graphic). Audio- and video-playing applications tend to report the data rates needed or used in terms of kilobits.
So...bytes and bits? I just divide by eight then? Not so fast! Communications equipment vendors like to think in terms of low-level ATM data rates without regard to the structure or content of the data. ATM is a protocol for transferring data between two points. The Internet uses IP as the protocol for communicating. In particular, TCP/IP is the protocol of the Internet. So your data is going over your DSL line via TCP/IP over ATM (see table 3).Table 3 Speed Maximum Visible Transfer Rate 256K ~28 KB/sec 384K ~42 KB/sec 640K ~69 KB/sec 768K ~83 KB/sec
TCP has an overhead in transmission that can be as low as 3 percent, but ATM overhead is more like 10 percent. So you can expect to lose about 13 percent of your purchased speed when counting application data transfer rate. Making up a rule of thumb here: Given a line speed, divide by 8 and take off 13 percent to calculate a reasonable estimate of the maximum data download speeds you will get. Beyond the concept of bandwidth speed, other factors can affect the performance of your connection. We call them "enemies to speed."
Enemies to Speed
Enemy 1: Badly configured PCs. The single most common cause of poor performance is a Windows PC that is in poor shape for broadband. Problems include:
- Insufficient memory (64 MB is really the lower limit now for any Windows install).
- Underpowered processor (less than 133 MHz is a potential problem).
- An aging and unstable Windows installation (accumulation of shareware and applications in various state of disrepair) that can only really be cleaned by a format/reinstall.
- An overclocked motherboard that causes unusual problems with internal DSL modems and/or ethernet cards.
The list is endless, really. If you experience frequent application crashes or blue-screens, the disk churns like crazy as you switch between applications, or Windows reports warnings about virtual memory becoming low, then you don't have a stable system for experiencing top speed, especially from the point of view of the browser!
Enemy 2: Packet loss. As alluded to above, data transfer between you and another Internet computer is mostly done using TCP. TCP is designed around the assumption that some packets may not get through. For the sake of example, let us imagine you are downloading data from cnet.com, and one of the many packets streaming down to you disappears en route. Maybe a random neutrino knocks out a chip on a router for a microsecond, and the packet is dropped. TCP notices the missing packet in the stream of sequence numbers, and so does not acknowledge its reception.
If there is a continuous packet loss between you and your favorite site, it doesn't matter what you do, your TCP-based data (web pages or file transfers) are going to slow down to a crawl. In this case TCP is not working in your favor. Your data is getting lost at the same rate, no matter what speed you are running at, and yet TCP is slowing down. The result is that you get stuck with a poor speed because of gridlock beyond your control.
Enemy 3: Overloaded ISP gateway. ISPs don't purchase as much upstream bandwidth as the sum total of all of their downstream users. This is not in itself a crime-why should they pay for large pipes that are only used when you choose to get online? The trouble comes when they oversell to the extent that peak bandwidth aggregated demand from their users gets near to the maximum capacity they have purchased.
We are the end of a food chain here. Many of us connect to one ISP, and many ISPs connect to a tier 2 backbone, and many tier 2 backbones connect to a tier 1 backbone. At any of these points of aggregation, there may be congestion due to oversold bandwidth. Note that the overselling may not be just bandwidth. ISPs may oversell router CPU or memory capacity also. Putting too many users on one router can cause maximum CPU usage at peak hours and therefore slowdowns, despite bandwidth being available.
Enemy 4: You are not home free when your data gets to a backbone. The Internet can be imagined as a tree, with the root system the servers, and leaves the users. The trunk sap lines are the backbones. All "leaves" must currently get nutrients directly and on demand from the "roots"-the trunk does not store anything. Assuming you can get to an Internet backbone easily, you have (in reverse) the same potential problems reaching the server. The larger and more popular the server. The larger and more popular the server, however, the more likely it will be located close to a backbone, so there is more of a chance that you are home free and your requests are serviced at full speed. But there still could be packet loss problems, or oversold bandwidth between the server and its connected backbones, even between different backbones!
Enemy 5: Many servers cannot currently offer high speed. Table 4 includes some results of a speed test to several reasonably well-connected servers at 3 a.m. (off peak). In this example, Microsoft and flashcom did not provide the "high-speed experience" to users who purchased speeds of 768 kbps or more. Many servers offer speeds far slower than this, because they are busy or you are sharing a T1 or a T3 with dozens of other people.Table 4 Server File Speed ftp.netscape.com 1.6 MB 310 kbps ftp.aol.com 2.0 MB 280 kbps ftp.microsoft.com 5.0 MB 67 kbps ftp.flashcom.com 5.0 MB 66 kbps
Enemy 6: Peak versus off-peak hours. U.S. Internet rush hour seems to start on weekday mornings on the East Coast, with higher intensity bursts at lunch on the East server, however, the more likely it will be located close to a backbone, so there is more of a chance that you are home free and your requests are serviced at full speed. But there still could be packet loss problems, or oversold bandwidth between the server and its connected backbones, even between different backbones!
Enemy 5: Many servers cannot currently offer high speed. Table 4 includes some results of a speed test to several reasonably well-connected servers at 3 a.m. (off peak). In this example, Microsoft and flashcom did not provide the "high-speed experience" to users who purchased speeds of 768 kbps or more. Many servers offer speeds far slower than this, because they are busy or you are sharing a T1 or a T3 with dozens of other people.
Enemy 6: Peak versus off-peak hours. U.S. Internet rush hour seems to start on weekday mornings on the East Coast, with higher intensity bursts at lunch on the East and West coasts, and drops at dinner time. Then there is a final evening push that tails off around 1:00 a.m. East Coast time. During peak hours, problems with packet loss, oversold bandwidth, and oversold servers are emphasized and magnified. If your ISP is not managing its demand correctly, you are most likely to discover it during Internet peak hours.
Enemy 7: Hop count, latency. Hop count is the number of routers your packets must navigate before they reach the destination. With a small ISP, things are, thankfully, simple: Your data goes to the ISP via your provider network, then it goes to the Internet, at or very near the ISP network operations center. Knowing where your ISP gateways to the Internet will tell you whether there will be many hops between you and the data you need.
The more hops between you and your destination, the more latency (traveling time), and the more potentially overloaded or troublesome Internet hops you may have to cross. Latency is also a function of link speed. Comparing link A and link B, if it takes half the time to transmit a data packet over B, then latency is likely to be roughly half on B of what it is on A. The replacement of slow modems with high-speed lines has contributed to huge drops in latency, from 150-200 milliseconds (ms) down to 20 ms for small packets, and from 200-400 ms down to 50 ms for large packets.
Low latency is very important for interactive applications, VPNs, telnet sessions, and multiplayer games; high latency can make the Web feel more sluggish. A 200 ms latency can add 200 ms to the total download time for the page for every eight or so objects on that page! Some complex pages contain dozens and dozens of components to download, making a high latency connection feel very slow.
Enemy 8: Routing problems. Routing problems can cause weird drops in speed. Ninety-nine percent of the time, your data packets travel along the same path upstream as back down, but it isn't necessarily so. Sometimes there are router problems, and packets can start taking alternate routes. The worst case is that alternate packets can take alternate routes in the same TCP conversation. This plays merry hell with the TCP transmit speed calculations, and performance drops quickly.
Enemy 9: Poor upload speed. Back to upload speed. What is it good for? A download is not just a download of data. The protocol involved in downloading data requires a back channel to communicate messages to the sender. As in conversation, it is very hard for speakers to know they are being understood if they don't get a fairly continuous stream of affirmations by the listener.
Your maximum upload speed is something you need to include as a possible factor in reductions in download speeds. Let's take Bell Atlantic's 90/640 ADSL product as an example. For every packet received on the download channel, a 40-byte packet must come back (a zero data length TCP packet). If the link was running at full speed, 640 kbps, you would need a back channel capacity of more than 640 x 6 percent overhead = 40. So your return channel is half used for just a download! For Bell Atlantic 90/1600 ADSL, things are even more dire, and you may have trouble seeing 1600 kbps! If you wish to transmit data on your upload channel (say, sending an e-mail with a large attachment, or having someone use your FTP server, or taking an MP3 from your Napster cache), then download speed will be severely impacted.
If They Build It, Will You Come?
Business requires a much higher level of service than does residential-services such as uptime, customer service, security, and redundancy. Providers are scrambling to serve the residential markets in the expectation that the masses will bring fortune. In the meantime, the business sector, where the real demand is, has been neglected. As companies attempted to serve both market segments, they did not differentiate between the business and residential accounts. A business cable or DSL user goes through the same customer service channels as the residential users.
Simultaneously, the "build it and they will come" mentality developed when hyper-funding accompanied the stock market frenzy of a few years ago, resulting in the rash of failures and bankruptcies that we are currently seeing. The aftermath of this destruction will be the same few faceless providers such as PacBell, Verizon, Sprint, Cox, and Time-Warner. There will also be a few "niche" companies who will "build it only if you come."
Christopher Heitman is vice president of sales at eBuilding Solutions, which offers a low-cost, high-speed Internet access solution for small and medium-sized businesses. eBuilding installs its high-speed wired and wireless networks in multi-tenant buildings and is a full-service Internet provider, offering website and e-mail hosting. He can be reached via e-mail at firstname.lastname@example.org.