Bandwidth sizing One of the first considerations for a firewall or any device that sits at the WAN is the throughput. You'll need to know your current WAN bandwidth from your provider as well as any burstable limits. For example, you may have a 10mbps link with the capability to burst to 25mbps. Couple that information with any data you have on current usage and then identify potential bandwidth growths in the coming years. You should plan enough room for growth for however long you plan to have that box in place. Look at the stateful throughput and maximum connection numbers on firewalls you're considering. These numbers will help filter out a bulk of products and models from your potential list and narrow your field to two - three models per vendor.
Layered security The next key question will be whether you plan to add additional gateway security services to your firewall or unified threat management (UTM). Personally, I suggest doing so whenever possible. Most UTMs license security features per box instead of per user, so it's a great way to add a layer of security for a nominal fee. Common gateway security services are antivirus, anti-spyware, and IDS/IPS. Here's the important part: If you're adding gateway security to your firewall, it will affect the performance. Don't worry; that's not a bad thing unless you started with too small of a box. Revisit the first question and weed out any boxes that can't handle security services with the bandwidth you need. Remember to consider your future needs and size appropriately. Look at the UTM throughput numbers for products you're considering. At this point you'll have just one -- two models per vendor to consider.
Remote connections Here's where we get into considerations a lot of people overlook. Check out your current firewall configuration very carefully, and make sure you can identify all the functions it's currently performing. Of specific note are remote connections, including site-to-site VPNs and remote access VPNs for employees or partners. It's unlikely your VPN needs will dictate the size of the box, but you may need additional licenses, and in some cases, unique remote access needs require some unique products. If you're currently supporting remote access via IPsec VPN, you'll want to understand the impact firewall and VPN client software changes may have on your users. Sometimes it's more of a headache than you want, but proper planning can help mitigate the level of frustration.
Physical interfaces Although rarely an issue in smaller organizations, it's certainly advisable to be sure any firewalls you're considering support the appropriate physical connections you need. Most common are gigabit copper ports, but you may need a firewall that supports expansion or flex modules for SFP/fiber, T1, or ADSL connections.
Advanced features If your organization has some specific issues or needs to address, be sure and discuss those with your integrator or vendor. In certain product lines, many vendors offer advanced features that may be of interest to you -- such as layer 7 application firewalls to address peer-to-peer traffic and bandwidth-hogging applications. Others offer content filtering as an add-on or as part of a security bundle. Again, these add-ons can be much more cost-effective on a firewall since they're usually licensed per box and not per user; content filtering is a great example of that. You may need advanced archiving or logging options for your compliance needs. Other advanced features that may determine your firewall selection include single sign-on functions, options for redundancy and high availability, and dynamic routing protocols supported. For example, if you plan to use BGP for a private MetroE network, your options will be different than those for OSPF or RIP.
These are just a few of the considerations when selecting a firewall for an SMB. If you're in the market for a new firewall, think it through and dedicate the appropriate amount of time to selecting the right product for you. Replacing firewalls is not a task to take lightly and it's definitely not something you want to do more often than is absolutely necessary.
Jennifer Jabbusch is a CISO and infrastructure security specialist at Carolina Advanced Digital. By day she architects enterprise security solutions and by night, well, she does the same thing. For Dark Reading, she melds her enterprise experience and intimate knowledge of small business operations to deliver relevant security guidance for SMBs everywhere.