Hardware Router NTK - Terminology Guide

Even though you have our general recommendations, you should still understand the features you're likely to find in your router, and what they do.

Firewall Type

One of the first questions you may be faced with is whether to buy a "Stateful Inspection" or "Stateful Packet Inspection" (SPI) based router. To answer this question, you'll need to know a little more about how a router works its magic.

All consumer grade routers are based on Network Address Translation. This is the technology that lets you have multiple computers on your LAN (which each have their own IP address) communicate with the Internet through the single IP address that your Internet Service Provider / Broadband Service Provider (ISP / BSP) assigns to you. NAT also provides a basic firewall, since it only allows data from the Internet through it if that data is the result of a request that originated on a computer on your LAN. Since NAT requires that the router look at (or inspect) part of each data packet that passes through it, why isn't that considered SPI?

Turns out that the answer to this question is the subject of some amount of debate in the industry, partially due to the term's misuse by some companies to describe early NAT-based products. It's also difficult for the average purchaser of a router to verify actual SPI operation. On a practical basis, however, it's not so much a matter of NAT vs. SPI, but a question of the feature set you desire. "SPI" based consumer routers can usually be differentiated from their plain-vanilla cousins by the presence of features like emailed attack alerts and reports, although exceptions can be found to this rule. In the end, SPI is being mainly used as a way to charge more for a product that has rapidly moved down the price curve to become a commodity.

Recommendation: If the only difference in features between the products that you're considering is that one has SPI and the other doesn't, choose the SPI product if you tend to use a lot of mapped ports, or you're hosting some sort of server behind your router. Otherwise, plain ol' NAT should do just fine.

Tip: For more info check out HowStuffWorks' article on NAT.