Carrier Ethernet Essentials
Many technologies are used to deliver metro and wide-area services. Layer 1 TDM technologies used to deliver private line services include T1 and T3 copper circuits, and SONET-based optical circuits. Layer 2 technologies used to deliver data services over the Layer 1 TDM technologies include Frame Relay, ATM and PPP. These legacy technologies provide inflexible bandwidth scalability because the bandwidth is dictated by the technology. When a service provider or enterprise needs to add bandwidth, they either bond multiple circuits together or upgrade their network and equipment to support a new technology.