• What is SDSL?

  SDSL provides high speed internet access over ordinary copper telephone wires. It is primarily used by small to medium businesses.

• What does SDSL do?

  Using a copper pair running from the local phone company to your business, SDSL provides internet bandwidth a lower cost than T1 (DS1) service. SDSL is used to provide internet access - it is not a replacement for communications based on protocols other than TCP/IP.

  The "S" in SDSL stands for symmetrical - SDSL is the same speed in both directions.

  The fastest speed you can get depends on the distance between the phone company's building (called the Central Office or C/O) and your building. Distance is the length of the copper pair, which is probably more than the direct "as the crow flies" distance.

  The phone company central office is usually located "Downtown" or in the business district of a community.

  SDSL is generally available in speeds from 384kb to 3Mb per second - roughly 10 to 100 times the speed of a dialup phone line.

• Can I get SDSL?

  Whether you can get SDSL depends on how long the copper line is from the local phone company to your location.

  Unlike the consumer ADSL product, SDSL runs on a dedicated copper pair - it does not share a copper pair with a voice phone circuit. Unless you have an unused pair into your building, that means you could need to have a new line installed or give up an existing phone line.

  The main reason that you might not be able to get SDSL is that you are too far away from the Central Office -or- the lines have impairments that prevent having a suitable all copper connection.

  Because SDSL has a higher monthly co$t than residential DSL, the phone company may work harder to make sure the installation is successful than they would for a residential ADSL account.

  If the circuit is too long, the phone company may consider putting in a remote central office (also called a Remote DSLAM).

  If they install a remote DSLAM, the copper distance starts from the remote CO instead of the main CO. These are usually installed where there is a high concentration of potential customers (an office park, an apartment complex, new subdivisions, etc…)

  If your location is between 17,000 and 30,000 feet, you may be able to get a related service called IDSL - DSL over ISDN. This service is only 144kb/sec in both directions.

• What equipment do I need for SDSL?

  If this is a new installation, you probably want to purchase an integrated DSL modem and router. If you already have an existing router in place, then a stand alone DSL modem will do.

  If you do not currently have networked computers, then you'll need to run CAT5 cable from the location of your modem and/or router to each of the computers.

  You may also consider installing a wireless router if cabling is a problem - but be aware that a wireless router is not very secure and is limited to perhaps 50 feet.

  Some providers may have limitations on Customer Provided Equipment (CPE) being connected to their network, and may require you to install specific types of equipment to allow the provider to properly manage and maintain their network.

• Who can sell SDSL to me?

  The most obvious choice is always your local incumbent phone company (ILEC) - the one that has been around forever, although perhaps a few name changes - SBC, Qwest, Verizon, BellSouth, Frontier/Citizens, Alltel, Sprint, etc…

  Because this company owns the copper wire that already runs into your location, they have an advantage over any other provider.

  You can also have DSL provisioned through a third party - Covad (big cities) and New Edge (Small markets) are the two main companies in this business. There are a number of other companies that market and resell Covad's services.

  The third party DSL providers rent the copper circuit from the ILEC, and then provide the path to the internet along with ISP services (Email, web space, DNS, newsgroups).

  Traditional ISPs may also sell DSL, however they tend to offer the service only in the local market they serve (or are marketing Covad access bundled with their ISP services).

• What are the alternatives to SDSL?
  • T1 circuit if your location is too far away from the central office
  • Fixed Wireless Broadband (802.11x)
  • Cable Internet - often much more bandwidth at a lower cost, and no distance limits
  • Fiber to the building - move into a building that has a direct internet connection using a high speed fiber optic connection, bypassing the local phone company. Often these are located near railroad tracks, as many fiber optic lines have been buried on railroad rights of way.
  • Frame Relay if you need to connect also to non-TCP/IP networks (IBM Mainframes with legacy SDLC controllers, for instance)
  • Coming soon - WiMax (802.16)
  • Maybe coming soon - Broadband over Power Lines (BPL) - your power company may want to get into the internet business, too... facing FCC complaints due to interference with other services

DSL itself only provides the ability for computers connected to your internal network the ability to surf the web and interact with other computers on the Internet.

To get a complete picture of what you want, and the complete costs of those services, consider if you need:

• domain hosting and DNS services
  Do you want people to be able to access your business through a domain name that you control (or will acquire) - do you want this-is-my-business.com to point traffic to your new SDSL connection?

• Email hosting
  Do you want email from your employees to have the DSL provider for their email address (john.smith@myDSLprovider.net) or do you want email to come to your company's domain (john.smith@this-is-my-business.com)?

  If your DSL provider provides the email addresses, you're locking yourself into that DSL provider - switching later means notifying all of your business partners with new email addresses.

• Web Hosting
  Do you plan to run http://www.this-is-my-business.com/ from inside your building? Or would you like it to be located on a server managed and run by the DSL provider or a web hosting service?

  If you decide to run your own web server and it is a business critical application, include the cost of installing backup power supplies and an ISDN circuit in case the SDSL goes down.

• Managed Network Services
  Would you like someone else to be responsible for making sure your computers keep running smoothly? Who knows how to stop that denial of service attack on your server?

• Network Address Translation (NAT)
  If you choose a solution which has NAT, your group of computers all appear to the internet to be a single computer that is not very interested in accepting connections from the outside world (a good thing).

  A Firewall and/or a router with NAT is an essential first step for protecting your sensitive business computers from hackers. Do NOT rely solely on Microsoft's protection built into Windows(tm).

  If you want to expose services to the world on purpose (FTP, telnet, chat servers, email, DNS), then you will either want multiple static IP addresses or use the capabilities of your router to redirect service requests to the correct computer behind the router (this is calling port forwarding)

  If your network contains any sensitive data, you should consider placing those public services outside the internal firewall, or in a DMZ.

  A DMZ is a buffer between the external world and your local network that insulates your computers from attack from the outside - however, if one of your computer users installs a trojan on a computer in the protected network, that could end up defeating all of the other security measures.

  Run Virus software, and spyware protection on all computers connected to the internet. Educate your users about never opening email attachments or downloading files from the internet from untrusted sources.

• Firewall Management
  If you want your computers to not be hiding behind NAT, then you will need a hardware firewall and a managed security service to protect and actively manage which internet traffic is allowed in and out of your company.

• Voice over IP
  With a high speed internet connection in place, you can move some or all of your voice calls onto the SDSL circuit. This eliminates the monthly line charge and per minute connection charges imposed by the local phone company. The only incremental cost for VoIP is when you place a call that returns back to the POTS (Plain Old Telephone System) for the called party.

  You may find that your internet provider or VoIP company offers you for free or very low cost the services that your local phone company loads up your bill with - callerid, three way calling, voicemail.

  As VoIP becomes more widely adopted, POTS is likely to become a relatively small part of the voice market. This has not escaped the attention of the big guys, who are also gearing up to compete with VoIP products of their own.

• Dialup backup
  If your people are on the road or the DSL goes down, you're not completely out of the water. Some DSL plans include dialup hours each month.

• VPN
  If your employees need access to their computers from the internet (home, airports, branch offices), a VPN provides a secure method to access their computers from outside of the firewall.

  If you're considering a VPN, take a look at gotomyPC, which offers a useful service without the complexity or special hardware of a typical VPN.

• Web Filtering
  Do you want to limit surfing by your users to inappropriate web sites? (or are you required to by law or on the advice of your legal staff?). A proxy server will limit the users on your network from visiting unapproved web sites - just be realistic that no solution is 100% perfect, especially if the surfer is willing to risk being caught going around your measures.