 ATM and SONET/SDH include high cost, lack of flexibility and scalability. Ethernet brings flexibility, scalability and cost effectiveness that give providers the ability to enhance profits while meeting emerging customer needs. Ethernet is becoming more appealing as it supports multiple services at lower price points than the current SONET networks. This expected transition is shown in Figure 7.16, where packet based Ethernet moves down the layers as it replaces TDM (SONET/SDH) and as it becomes connection oriented. 7.4.2.3.1 What is Carrier Ethernet? Carrier Ethernet is a recent advancement proposed by standard bodies to transport data using Ethernet with carrier class service attributes. Carrier Ethernet is a ubiquitous, standardized, carrier-class service defined by five attributes that distinguish Carrier Ethernet from familiar LAN based Ethernet. These five attributes defined by MEF (Metro Ethernet Forum) are standardized services, scalability, service management, reliability and QoS as shown in Figure 7.17. Standardized Services: Supports point-to-point (Ethernet Line) multi-point to multi-point (Ethernet LAN) services and requires no changes to customer LAN equipment or networks. Scalability: Supports from 1 Mbps to 10 Gbps and beyond and allows millions to use a network service. Reliability: Supports rapid recovery time as low as 50 ms while meeting quality and availability requirements. QoS: Supports multiple QoS requirements and provision SLAs (service level agreements) that provide end-to-end performance based on CIR (committed information rate), frame loss, delay and delay variation characteristics. Service Management: Supports the ability to monitor, diagnose and centrally manage the network, using standards-based vendor independent implementations. Application Application Application Ethernet IP/MPLS IP/MPLS SONET/SDH/NGSDH SONET/SDH/NGSDH Ethernet Carrier Ethernet Fiber Fiber Fiber Today's Transport Tomorrow's Transport Figure 7.16 Transition to carrier ethernet Next Generation Mobile Communicatio