Building a data center security architecture

Data center architecture has been changing quite dramatically over the past few years. In many data centers, organic growth had left them broken up into application silos. The standard three-tier architecture was copied for each application leading to a fairly hierarchical network. In this architecture, some core security services, such as firewalls and intrusion prevention, were concentrated at the root of the network tree, closest to the ingress routers and around any  DMZs.

Other security appliances, such as SSL accelerators or authentication/authorization systems, might be added to a specific application silo, often as a “temporary” addition or fix. Passive monitoring appliances might also be plugged in to span ports, monitoring traffic at strategic intersections in the network tree. All of those different security systems are now being consolidated, creating a dedicated purpose-built security subnet architecture.

This is not unique to security. We are also seeing similar consolidation in many other network or application services. Optimization devices, caching, load balancing, application gateways, XML gateways and security appliances are often bundled into one “services subnet” that makes the services available to any application in the data center. The strongest driver for this architectural change is the corresponding changes in application architecture. As applications are consolidated and virtualized they often reside in a pool of servers and can be rapidly provisioned anywhere in that pool.

It becomes increasingly harder to point to a specific server and say “that’s the CRM”. Don’t get me wrong: I’m not talking about adaptive or autonomic application shuffling. Even with fairly manual provisioning processes, flexibility and server pooling blur the fixed lines between silos and make things more fluid. So if the applications can be moved around, then the supporting appliances and services also tend to be consolidated and shared.


More companies are reaching out to us to discuss consolidation of DMZs and appliances. They are trying to create standardized services subnets primarily to cut costs and reduce complexity. Until recently, the focus has been split between application services (optimization, caching and so on) and security services (consolidated DMZ, IPS). Increasingly however, these functions are converging onto fewer appliances and companies are looking to consolidate them on a single subnet.

Another interesting possibility is the consolidation of passive monitoring systems. Plenty of different passive monitoring systems are scattered around data centers. Whether monitoring performance, network parameters, netflow, security events or applications, these passive devices are competing for limited span ports. Network switches at certain critical intersections in the network quickly run out of span ports or struggle to provide copies of wire-speed traffic to a number of monitor devices. This is likely then to be the next point of architectural consolidation. Along side the active appliance subnet architecture, companies can build a dedicated monitoring architecture that consolidates all the passive appliances in a single location.

As the data center silos break down and the data center network becomes more flat architecturally, we expect to see appliances (both active and passive) consolidated into dedicated services subnets. The architecture of the data center started changing because of server virtualization and consolidation, but the changes are reverberating out. Security is no exception.


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Jim Love, Chief Content Officer, IT World Canada

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