Home Toys Article
- August 2004 -
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Routers Versus Switches
Data is transported much like the mail. In some cases, the mailperson brings the mail and drops it directly at the door of the recipient. In other cases, the mail is delivered to a corporate mailroom and is forwarded by the companies' internal mail delivery system.
It is likely a dealer installs complicated systems in dozens or hundreds of homes every month, and carries a large array of products that constantly change. In this article, we examine a potential customer who is looking to fulfill TCP/IP networking needs. Is your installer or salesperson going to have the technological horsepower to engage and satisfy the customer's needs? With Moore's law and the rapidly changing technology of the day, it is easy to become overwhelmed and just give up on keeping abreast of networking. However, these concepts will assist in helping the technological savvy customer.
Data is transported much like the mail. In some cases, the mailperson brings the mail and drops it directly at the door of the recipient. In other cases, the mail is delivered to a corporate mailroom and is forwarded by the companies' internal mail delivery system. In this case, the mailman does not know the recipient's actual physical location on the premises, and when opening the mail, the recipient doesn't care how many people it took to get the package on their desk. Using these analogies, the front door delivery is the path of a data packet through a switch, and the corporate mailroom is the path through a router with DHCP and NAT.
A switch does not look inside the mail or examine the type of mail being delivered. The only logic behind a switch is a table of which port a destination can be eventually found through. Removing a computer from one port on a switch, and swapping it to another, can lead to problems until the switch figures out the destination must now be found through a different path. The methods for maintaining this table and its accuracy are beyond the scope of this writing and knowledge of those methods are not necessary at this point.
Most switches will be used in a home network, where data is directly traveling to its intended destination. Questions to ask the customer are, "Are you using a server, such as for DHCP?", and "Are you being assigned multiple Internet Protocol (IP) addresses by your ISP (Internet Service Provider)?" If the response is a blank stare, or negative to both questions, a switch will not be the correct choice for this customer. The third question to qualify a customer in an existing installation is, "Are you currently using a hub?" A switch directly replaces a hub and will improve the speed of most devices plugged in. A hub is now largely obsolete and has performance pitfalls when compared to a switch.
A positive response to any of the three questions above is an indication the customer needs a switch, because these are situations where data is being sent directly to the destination's address. Additionally, if you are installing a large system that can not be served by a single router, this is also a situation where a switch is necessary. Switches are ideal for expanding a router with NAT and DHCP.
Routers, as mentioned, are very similar to the mailroom, where mail comes from one point of entry and is further divided up and delivered to the actual destination. IP addresses are like physical addresses, and thus, are in short supply. Networks often use "Care of Addresses" to mitigate the scarcity, just as your mail center saves your postmaster from delivering to each desk at a company. Likewise, a router allows mail to be inspected, redirected, or even blocked based on for whom it is intended and the type of data.
A security feature of routers is the fact they can look at mail and apply simple rules to determine if they are security risks. An incoming piece of corporate mail for someone who quit last week can be thrown in the trash by the mail center, just as a malicious packet of data destined for a port your computer doesn't typically use can be discarded. This is referred to as a Hardware Firewall. This not to be confused with software firewalls. Software firewalls are applications running on a server.
Routers can also "redirect" data packets. Many ISPs (Internet Service Providers) only provide a single physical address (IP address) for their customers. Additional addresses are available, but for an increased cost. Routers with NAT, or Network Address Translation, allow multiple computers to use a single IP address provided by their ISP, and then the router forwards the incoming data to the appropriate computer. This is also considered a security feature, because networks outside the router never see the internal network or computer's IP address. Hence, a router can be a great security item for all your customers with a broadband connection, regardless if they have one or many computers.
Routers also commonly have a feature called DHCP (Dynamic Host Control Protocol) which is an automated means for each network device to get their own physical address. Many years ago, it was a complicated procedure to get multiple computers hooked up, configured and talking to each other using the same protocol. With DHCP, each computer or network device broadcasts a request for an address on the network, and the configuration data is replied back directly to them. This allows any device to be simply plugged in, turned on, and self-configured. No configuration or testing is required by your installers if the network device automatically looks for a DHCP server, regardless if it is a laptop computer, an IP-based camera, or a Smart Appliance, such as a refrigerator. There are refrigerators now with cameras and network interfaces built in so that a consumer can "see" if they need milk from anywhere, such as from the supermarket while using a network-ready cellular phone. This level of configuration automation and network compatibility was just a dream 10 years ago.
Due to the data forwarding (NAT) and physical address allocation (DHCP) features which are normally enabled (by default) on most manufacturer's routers, it is a bad idea to implement multiple routers in a homeowners network. If you try to use multiple routers with NAT and DHCP features, your installers will need to have a much more detailed knowledge of TCP/IP, time on site for installation will be increased, and potential for call-backs are greater if and when the customer inadvertently changes the router settings. Since upgrading is common as features become available or change, a router reverting back to default settings when a customer upgrades the router's firmware can cause a call-back to the job site. This worst case scenario is likely to happen but it is easily avoidable. Use switches to expand a router and potential conflicts will be avoided down the road.
To summarize, the simple solution is to determine if the customer is using an ISP without running any servers. In this case, the installation will be easy, and the customer can be sold a router. If the customer needs more ports than are available on a single router, use switches to expand the router. For example, you should recommend a homeowner with 22 network devices use a single, 4-port router, and three, 8-port switches to make the installation easier, provide faster network performance and increased reliability.
A small percentage of your customers will be very network savvy and operate their own servers and/or using multiple IP addresses from their ISP. These customers are less likely to ask for advice, but if they do, switches are very likely to be their solution. For this type of customer, get a detailed description of the network devices they will be using and how they will be used, such as "FTP Server", "DHCP Server", and then call our Technical Support group for specific installation advice. By following these guidelines, your installers will appear to be network gurus and the customer will be impressed when their specific, custom installations get the appropriate time and effort put into ensuring their data network is a success.