Difficulties in adding new telephone-based services, which require modification of the subnet infrastructure, provide a counterpoint. Multiservice network architectures. New service models are being defined, but specific mechanisms and protocols are needed to provide applications with differing performance and reliability requirements with different classes of service. Although much research has been accomplished in this area, a complete network architecture has yet to be fully demonstrated. There will never be enough bandwidth .
Scarce bandwidth means contention and congestion.
Scalability will thus continue to be a critical concern in the future. Protocols define the manner in which different entities interact. The telephone network has been engineered with reliability as a primary concern. Redundancy, networking monitoring, and network management play key roles. And yet we read stories of spectacular telephone and computer network failures.