In response to a recent post questioning why someone would want to run a firewall-less network, Lori MacVittie tweeted that performance might be one reason with a link back to a a recent article she wrote:  http://devcentral.f5.com/weblogs/macvittie/archive/2011/02/16/challenging-the-firewall-data-center-dogma.aspx

The Firewall in Front of the Data Center

In her article, MacVittie is not advocating doing away with firewalls, but she is questioning the dogma of a firewall in the data center, specifically firewalls protecting Web Services.  The basic premise is that firewalls can be a bottleneck, or worse a point of failure, due to performance issues or denial of service attacks.  I completely agree that this design should be questioned in this case.  That may seem odd coming from a firewall management vendor like FireMon, but firewalls are not the end-all of security and we don’t advocate ineffective use of the technology.

Public facing services, which are most susceptible to denial of service attacks, have a unique access requirement of allowing everyone.  When you have a service that is needed by everyone, access control is not really controlling much and does raise the question of why implement a firewall at all. However, this does not mean there is not a role for the firewall in this architecture.  In fact, it is now critical to ensure access is

The Firewall Inside the Data Center

controlled from this public system to any other system on the network.  In the traditional sense of a DMZ, no access should be allowed from this public system to any other protected system to protect the network in the event of a breach.  Addressing this access control requirement results in implementing a firewall technology limiting communication between systems behind the web server.

I agree with MacVittie that just because it is how something has historically been done is not justification for continuing to do it that way.  But I also don’t see this as a reason to run a network without a firewall; just a discussion about where to implement them.  In all cases, regardless of where the firewall is implemented, the key to ensuring it is an effective security control is to effectively manage it.