t peak traffic periods. In a branch office network environment, these cost savings can be substantial. Frame Relay can sup- port multiple protocols and applications including LAN, Systems Network Architecture (SNA), on-net voice, and packetized video. End users can migrate from multiple parallel networks deployed to support each applica- tion to a single Frame Relay network. Simplification has many benefits including reducing costs, improving reliability and performance, and sim- plifying planning and reengineering. Frame Relay is enhanced by the capability to smoothly migrate to Asyn- chronous Transfer Mode (ATM) when higher capacity is required; this enables customers to get started with the more complex ATM in a gradual fashion and to learn the complexities and then apply them to the network as needed. Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. PCUSN-to-SGSN Interface (Gb) Chapter 9 Service Comparison Private lines use Time Division Multiplexing (TDM) where fixed time slots or channels are dedicated to specific applications whether the applications are active or not. Private lines are generally designed to meet peak traffic delivery objectives. This translates into excess bandwidth or idle capacity during non-peak hours. Private lines are more susceptible to network downtime because the network does not automatically reroute around physical network failures, such as cable cuts, unless the end user invests in intelligent network switches and geographically diverse facilities for backup purposes. Statistical multiplexing with Frame Relay enables applications to share network bandwidth. Network bandwidth is used by active applications only. An active application can have full access to the port connection for the entire duration of time when other applications that share that port are not transmitting or receiving. Frame Relay can autom