<H1>statistical multiplexer, stat mux, dsu, remote access </H1>

Small Business Series: Connecting your LAN to the Internet

Connecting your LAN to the Internet was truly a huge project a couple of years ago. But, times change, equipment is now cheaper, and software is much easier to use. It no longer takes a team of experts to connect your local area network (LAN) to the Internet. As a small business, you have probably tested the Internet waters with a single PC connection, perhaps using America On Line or Compuserve, and are now ready to give that access to your other employees. May be you want to establish your presence as a World Wide Web site. In this paper, we discuss connecting your LAN to the Internet so some (or all) of your workstations and PC's can have access to all Internet functions such as the WEB, Electronic Mail, Netnews, Archie, Gopher, FTP, Telnet, etc. Providing a presence as a WEB site is covered in another session.

Step one is to fully document your goals and requirements along with your current LAN configuration.

In this example, we will assume that you have a local area network (LAN) with somewhere between five and fifty PC's running Windows 95, with either Novell or Microsoft network servers, and are using the most common network type of 10BaseT ethernet as shown in figure one. The concepts apply to almost all mid-sized LAN networks and the details apply to most similar LAN situations.

Picture of a typical office LAN

To add Internet access to your existing LAN, you only need to add several pieces to your current computer system. We'll take them one at a time...

An Internet Service Provider (ISP) is the provider of the connection between your network and the Internet. These range from the largest nationwide providers such as AT&T, Sprint, MCI, UUNET, and PSI to the small shops that serve only one town. You should shop around for the best price at your location. We'll discuss the cost of this service later.

A local connection to that ISP. In its simplist form, this is a telephone line. It is usually a digital data service (DDS) line, a frame relay leased line or an ISDN line. (See our "Small Business Series: Communications Technology" paper for more information on these.) In some more remote sites where it isn't economical to put in a full time connection, lower performance dial up telephone lines are used. More on this later also.

A device to terminate the ISP data line and make it compatible with local network equipment. This changes the WAN (Wide Area Network) electrical signals to more readily used local standards such as V.35 or RS-232. Depending on the type of telephone line you purchase, this may be called a telephone line modem, digital leased line or frame relay DSU/CSU (Data Service Unit/Customer Service Unit), or ISDN TA (Terminal Adapter).

A router. This is a device that "routes" information (packets) between your LAN and the ISP. It serves several purposes such as providing filtering, a security function that keeps others out of your LAN; electrical conversion, converting the ethernet LAN signals to electrical signals that can transverse slower media conforming to V.35 or RS-232 standards; and routing, deciding which packets should stay local and which ones should be transmitted to the Internet connection.

This all is connected together in figure two.

Picture of a typical office LAN with Internet connection

Now, we'll discuss each of these devices and services in detail along with typical pricing.

The first decision to be made is more policy than technical. You must decide what you want to accomplish with the Internet connection. This is your Internet Use Policy. Most commonly, it goes something like this...

"We want our employees to perform on-line research of the marketplace, our competitors, and suppliers. We want to provide communications between all networked employees and our suppliers, customers, and peers using email. We want customers to be able to send email to us at an address such as sales@mycompany.com or info@mycompany.com . We do not want to provide a WEB site at this time. We do not want anyone on the Internet to have access to our local computer LAN."

That policy statement and the LAN description provide the basis for the technical decisions that follow.

The LAN description should be a complete documentation package for your existing LAN system. Don't skimp here (as you've probably done in the past). Get it all down on paper including brand names, model numbers, versions, etc. Some common information is...

How many PC's or workstations? Describe them. Intel PC's, Unix workstations ?

What networking and operating software? (Novell, Windows 95, Windows NT, OS-2)

What network media are you using? 10BaseT, 10Base2, 10Base5, 100BaseTx, etc.?

What protocols are you using? (Novel usually uses IPX/SPX, Windows may use several possibilities)

First, we need to decide what access speed and technology is best. For trouble-free, "live" Internet access, you'll need a 24 hour per day, 7-day per week connection. That means a leased line using DDS, Frame Relay or Centrex. Most companies this size will opt for either a 56kbps frame relay connection or an ISDN connection at 64 or 128kbps. Higher speeds are much more expensive and aren't required for the kind of usage we anticipate here. At this point, we decide between two methods with simple economics. Call up your prospective ISP's and get pricing. They will probably be encouraging one of these two methods. Be sure to ask about per-minute charges for ISDN and Committed Information Rate (CIR) charges on frame relay. Explain that you want realistic quotes based on a full-time connection. There is a data line required from their location to yours. This is normally leased from your local telephone company. The ISP handles the phone company for you. They contact the phone company and get quotes for the line between their point of presence (POP) and your location. They will get the monthly phone line bill and simply pass the cost through to you. Economics for this "local loop" vary greatly between locations and telephone companies, so there are no rules of thumb that apply everywhere. In California, US West is pushing Frame Relay. It's quite cost effective there. In central Illinois, Ameritech may encourage the use of ISDN and price it below frame relay. Some areas have ISDN with a $1.50 per minute charge, others don't meter usage at all. In short, get the quotes from several ISP's. They also cut deals with different telcos that get them favorable rates. A typical price for full time ISP access at 56Kbps is around $500 per month including the local access line. But, some rural areas are hit with up to $1,000 per month due to higher access line charges. If you choose to use a dial-up line and modem or ISDN line (without centrex), you'll have to estimate the number of hours per day the line will be in use. Calculate the cost of those hours and compare to the cost of a dedicated line.

Once you decide on the line type and speed, price the line termination equipment. The ISP will attempt to sell you their termination equipment (ISDN TA or Frame Relay DSU/CSU). Check their prices against other equipment providers. They are selling the same equipment that other data communications providers offer, and often at a markup. All of this equipment meets industry standards and most of it will interoperate. Don't let them tell you that you must use their equipment. Common costs of DSU/CSU's are around $500.00 to $700.00 for a basic unit and TA's go for $300 to $700 (this week) depending upon features. You need the proper one for your data line with the connections that match your router.

Next in the chain is a router. This device accepts the signals from the DSU/CSU or TA and ties it to the LAN ethernet. When connecting to the Internet, you will be using only the TCP/IP protocol. A multi-protocol router is not needed since the router only has to deal with IP protocols. For security, it does need to filter packets based upon addressing and ports. Most routers sold as "Internet Router", "Firewall Router", or "Filtering Router" provide this feature. The router should have the proper connector for your line termination equipment (this means it should be V.35 or RS-232 for most equipment), and it should match the LAN media. Most routers match any LAN media by having 10BaseT, 10Base2, and AUI connectors. Routers vary in price from $995 to over $10,000. The bottom end is more than enough for this situation. You probably don't need the features of anything that sells for more than $2,000.

Let's not forget software. You can use the networking features of your present operating system software or purchase add-ons. Windows 95 and Windows NT offer pretty good basic networking features. You just load the network protocol TCP/IP and its client. Then, you can get Microsoft Internet Explorer or NCSA Mosaic at no cost. As an alternative, you may choose to go with a commercial add-on product such as the Internet Explorer, Netscape, or Internet-in-a-Box type products. These come with better support, but at a price of $30 to $125 per workstation. You may want to add an email server package to one of your workstations at several hundred dollars. If you are using a local email system, check with your email software provider to integrate Internet email with your existing system.

The Internet connection will require some ongoing support and administration. We suggest building your own in-house expertise to cover the day-to-day administration, and cultivate a support relationship for the less common problems that crop up. Setting up the system will take some time... especially if you are learning as you go. Each machine has to be configured with TCP/IP software and an IP address. You need to add the applications (email, Mosaic, etc.) to each machine or install them on your file server.

Support for your Internet connection can come from several sources. The first is the ISP. They will usually help you set up the connection and routers, email server, and make sure at least one of your workstations works on the Internet. Most ISP's also have consulants available. The second source is the equipment providers. Some suppliers of data communications equipment have excellent service reputations. Most equipment manufacturers don't. You may want to contact a networking consultant for more specialized assistance. Your ISP or equipment supplier can usually point you to one. Lastly, remember that you will be building up your own expertise, so read the Windows manual and get some books covering the subject. Most book stores now seem to sell nothing but computer books. There are lots of resources available on the Internet in the form of mail lists and netnews groups. Take advantage of them.

Pay attention to security. Your ISP will recommend filtering rules for configuring your router. Use them. Make sure the rules follow your Internet Use Policy (remember that).

The Internet connection can be a productive addition to your business toolkit. It can also drain away a large amount of time and money if you don't implement it correctly. Plan ahead and use the facts, not the hype.


Data Comm for Business, Inc. is a manufacturer and distributor of a diverse line of data communications and networking products. Their experts can help you connect to the Internet with phone (1-800-4-dcbnet), email (info@dcbnet.com), or personal (807 Pioneer, Champaign, Il. 61820) assistance. Check out their Web page at http://www.dcbnet.com .



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