2 POS INTERFACE CONFIGURATIONWhen configuring POS interfaces, go to these sections for information you areinterested in:■ “Overview” on page 83■ “Configuring a POS Interface” on page 83■ “Displaying and Maintaining POS Interfaces” on page 84■ “POS Interface Configuration Example” on page 85■ “Troubleshooting POS Interfaces” on page 87Overview This section covers these topics:■ “SONET/SDH” on page 83■ “POS” on page 83SONET/SDH Synchronous optical network (SONET), a synchronous transmission system definedby ANSI, is an international standard transmission protocol. It adopts opticaltransmission.In SDH defined by CCIT (today’s ITU-T), adoption of synchronous multiplexing andflexible mapping allows you to add/drop low-speed tributary signals from SDHsignal without large amount of multiplexing/demultiplexing devices. This reducessignal attenuation and device investment.POS Packet over SONET/SDH (POS) is a technology popular in WAN and MAN. It cansupport packet data such as IP packets.POS maps length-variable packets directly to SONET synchronous payloads anduses the SONET physical layer transmission standard. It offers high-speed, reliable,and point-to-point data connectivity.The POS interface on your device supports PPP, Frame Relay, and HDLC at the datalink layer and IP at the network layer. Its transmission rate can vary with devices.For example, in the sequence of STM-1 (155 Mbps), STM-4c (622 Mbps) andSTM-16c/STM-16 (2.5 Gbps), the rate of each level is four times that of theimmediate lower level.Configuring a POSInterfaceBefore you configure the link layer and network layer protocols on a POS interface,you must configure its physical parameters. In addition, to have the interfaceparticipate in backup, configure the backup parameters; to set up firewall on theinterface, configure packet filtering rules.
