and ordinary citizens depend on communications to coordinate rescue operations and to stay in contact with family members. Even in the absence of a disaster, the ability to call police, fire departments, and hospitals is critical SO that people can report emer- gencies and assistance can be dispatched as quickly as possible. For these reasons, governments worldwide regulate network reliability and sustainability. Equipment and network sustainability refers to the capability to operate continually during adverse conditions. In the United States, the Federal Communications Commission (FCC) requires outage reports from the following providers: Wireline Wireless Paging Cable TV Satellite Signaling systems They must further report disruptions that affect the following: E-911 facilities Major military installations Key government facilities Nuclear power plants Certain airports In addition, fiber-optic outages on cabling that carries traffic between backbone network switches must be reported as well as outages of 30 minutes or longer in dura- tion that impact 900,000 or more user-minutes at these key facilities. Reports on out- ages are reviewed quarterly by the Network Reliability Steering Committee (NRSC), which is made up of representatives from nationwide wireline and wireless providers. The committee looks for patterns by type of failure SO that they can determine ways to prevent them. Carrier Networks Key Factors Affecting Reliability and Sustainability Carrier networks are now largely IP-based, converged networks, wherein a single net- work infrastructure carries data as well as telephone traffic. (The Internet and most mobile networks are made up of separate infrastructure.) Thus, outages cause disrup- tions to businesses, governments, and consumers. In addition, traffic volume increases significantly in emergencies. During widespread emergencies, mobile carriers free up capacity for the addi- tional volume required by assigning less frequency to each call. Thus, more calls can be carried, although at lower sou