<div align="justify"><p><b>Understanding networking technologies helps you build a network design ranging from basic LAN access to more robust, open network solutions that meet growing demands for bandwidth-intensive applications. This guide allows you to review which technology approach is best for your network today and which will work best for you as your business needs grow.</b> </p><p><b>Local-Area Networks: Ethernet, Fast Ethernet, and Gigabit Ethernet</b> </p><p>Ethernet has been around since the late 1970s and remains the leading network technology for LANs or networks contained in buildings or o­n a single site. Ethernet is based o­n a standard referred to as carrier sense multiple access with collision detection (CSMA/CD). (See Token Ring in the "Glossary" section to learn about another basic style of network communication.)Simply put, an Ethernet workstation can send data packets o­nly when no other packets are traveling o­n the network—when the network is "quiet." Otherwise, it waits to transmit, as a person might wait for another to speak during a conversation.If multiple stations sense an opening and start sending at the same time, a "collision" occurs. Each station then waits a random amount of time and tries to send its packet again. After 16 consecutive failed attempts, the original application that sent it must start again. As more people try to use the network, the number of collisions, errors, and subsequent retransmits grows quickly, causing a snowball effect.Collisions are normal occurrences, but too many can slow the network. When more than 50 percent of the total network bandwidth is used, collision rates begin to cause congestion. Files take longer to print, applications take longer to open, and users are forced to wait. At 60 percent or higher, the network can slow dramatically or even shut down. As noted in the previous section, Ethernet bandwidth or data-carrying capacity (also called throughput) is 10 Mbps. Fast Ethernet and Gigabit Ethernet works the same way—through collision detection—but provide 10 times the bandwidth, at 100 Mbps, and 100 times the bandwidth, at 1000 Mbps, respectively.Shared Ethernet is like a single-lane highway with a 10 Mbps speed limit. Shared Fast Ethernet is like a much wider highway with a 100 Mbps speed limit: there is more room for cars and they can travel at higher speeds. Switched Ethernet look likes a multilane highway with a speed limit of 10 Mbps in each lane. Switched Fast Ethernet also would be a multilane highway, but with a speed limit of 100 Mbps in each lane. Switched Gigabit Ethernet would have even more lanes, with a speed limit of 1000 Mbps in each lane. </p><p><b>Wireless Connections</b> </p><p>Wireless networking had not previously been widely adopted due to the low data rates supported and the lack of an international standard. The Institute of Electrical and Electronics Engineers (IEEE) is the international group that creates such standards—both Ethernet and Fast Ethernet are IEEE ratified standards. The IEEE has recently created a high-speed standard for wireless networking, IEEE 802.11b, which specifies the use of Direct Sequence Spread Spectrum (DSSS) technology. This technology has a shared throughput of up to 11 Mbps. With the advent of the 11 Mbps IEEE 802.11b standard, wireless networking is now a viable solution for today's business LAN. </p><p><b>Remote Access And Wide Area Networks</b> </p><p>LANs accommodate local users—people within a building or o­n a campus. WANs connect users and LANs spread between various sites, whether in the same city, across the country, or even around the world. "Remote access" refers to a simple connection, usually dialed up over telephone lines as needed, between an individual user or very small branch office and a central network. Your business gains access to the Internet through some type of remote connection. A single user can dial up ISP via modem. Multiple users within a campus might choose to rely o­n a router to connect to the ISP, who then connects the campus to the Internet.In general, LAN speeds are much greater than WAN and remote-access speeds. For example, a single shared Ethernet connection runs at 10 Mbps. Today's fastest analog modem runs at 56 kbps-less than o­ne percent of the speed of an Ethernet link. Even the more expensive, dedicated WAN services such as T1 lines don't compare (with bandwidth of 1.5 Mbps, a T1 has o­nly 15 percent of the capacity of a single Ethernet link). For this reason, proper network design aims to keep most traffic local—that is, contained within o­ne site—rather than allowing that traffic to move across the WAN. </p><p><b>VPN Virtual Private Networks:</b> </p><p>A Cost-effective Alternative to Building Your Own WAN. As businesses grow, they need to connect a rising number of remote offices and individuals to their central network to share information and resources electronically. Traditionally, this has been accomplished by building a private WAN, using leased lines to connect offices, and dial-access servers to support mobile users and telecommuters. </p><p>For a small or medium-sized business, a traditional private WAN can be costly to build and manage. The leased lines, telecommunications services, and equipment needed to interconnect offices can be expensive, and each added location requires a new leased line. Individuals or small branches dialing into a central site via the public telephone network incur long-distance charges, and managing dial-access servers at the central site can be resource intensive and complex. Now, businesses have an alternative for connecting remote sites and users to the main company network—virtual private networks (VPNs). A VPN offers the security and full data access of a private WAN, but because it runs over the Internet, it is more affordable and flexible. More affordable—Remote users can connect with central network resources through a local link to an ISP, at the price of a local call. This is a much more cost-effective method than making a long-distance call to the central site. </p><p><b>More flexible—</b>New sites can be added easily, without need for extensive new equipment or an additional, dedicated private line. VPNs also simplify the task of creating an extranet, giving customers or suppliers password-protected access to a portion of a private network—for example, to order products, check status of shipments, or submit invoices. </p><p><b>More reliable—</b>VPNs take advantage of the equipment and full-time expertise of the vast public network infrastructure and the companies that oversee it.How VPNs Keep an Internal Network Safe. </p><p>Offering access to your internal network through the Internet might seem like a recipe for data disaster, but VPNs use tunneling and encryption to protect your private traffic. Tunneling creates a temporary, point-to-point connection between the remote and central sites, blocking access to anyone outside. Encryption scrambles the data o­n the sending end and reassembles it o­n the receiving end, so it cannot be read or changed while in transit. </p><p><b>What You Need to Build a VPN</b> </p><p>You can build and maintain your own VPN, but most small and medium-sized businesses will find it easier to rely o­n a SP. In this case, you simply connect to the SP using routers (for sites with multiple users or heavy-duty usage) or modems (for individuals or branch offices with light usage)—just as you might connect your central site and remote users to the Internet. </p><p>Note that there are two types of VPNs: dial VPNs and dedicated VPNs. This means VPNs can take advantage of the low cost of ordinary dialup services, or, where a high-speed, high-capacity remote link is needed, they can operate over Frame Relay services or leased lines. When you implement a VPN, the offices in your network will need a firewall to act as a "sentry" to protect your network from unauthorized users. This firewall can be a standalone device, but for small networks, firewalls can be integrated into a server or router, simplifying management and lowering capital cost. </p><p>Keep in mind that using a VPN means relinquishing some control over your network. Be sure to find a SP who can provide a strong service-level guarantee (99-percent uptime or better) and support the protocols you are using (most likely, IP, or Internet Protocol) with minimal latency or traffic delay. If you have sites in multiple countries, you also may want to look for a SP that already has—or is planning to have—local points or presence in the nations where you operate. This keeps your costs down by minimizing long-distance charges; your sites connect using local calls.</p></div>