l excellence require 24 X 7 network operations support. Operational secu- rity is enhanced by use of separate networks for OAM and by requiring security gateways between networks that operate at different security levels. This is part of the principle of least privilege discussed above. Testing. Using some of the best "ethical hackers" to probe, test, and try to find weaknesses have been very effective in the deployment of the MPLS network. Occasionally, they find an area in which improvements are necessary-and steps are taken immediately to address their findings. Network Network Customer Customer Customer Customer Data Path Data Path Data Path Data Path FIGURE 9.9 Service chaining a security function into the OAM path. Building the Network of the Future Response. Security incident response is performed using a tiered operations structure. AT&T utilizes a mature, global three-tiered 24/7 security operations team that is centrally coordinated in the Global Network Operations Center in Bedminster, NJ. Expert Tier 3 security analysts support this structure as incidents are escalated using well-defined security methods and procedures. At Tier 1, trained operations managers use mature monitoring tools to proactively identify conditions that might warrant response. A Tier 2 management interface oversees this activity and is used to tie together conditions that might be brewing in disparate locations. Innovation. Tiers 1, 2, and 3 continuously evolve as security is an ongoing process. Potential attackers continue to look for new ways to attack and disrupt, defenders need to anticipate and con- tinue to build up defenses. Beyond that, security in computing and computer networking remains an active field of research and new advances are frequently made. Service providers and network operators need to stay current with these advances. In a "classical," appliance-based network, a security perimeter protects the network elements from attack. This may consist of access controls in routers, physical FWs, and systems for authe