3Com MSR 50 Series, Руководство по настройке

Страница: 83 / 2443

2
POS I
NTERFACE
C
ONFIGURATION
When configuring POS interfaces, go to these sections for information you are
interested 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 87
Overview
This section covers these topics:
■
“SONET/SDH” on page 83
■
“POS” on page 83
SONET/SDH Synchronous optical network (SONET), a synchronous transmission system defined
by ANSI, is an international standard transmission protocol. It adopts optical
transmission.
In SDH defined by CCIT (today’s ITU-T), adoption of synchronous multiplexing and
flexible mapping allows you to add/drop low-speed tributary signals from SDH
signal without large amount of multiplexing/demultiplexing devices. This reduces
signal attenuation and device investment.
POS Packet over SONET/SDH (POS) is a technology popular in WAN and MAN. It can
support packet data such as IP packets.
POS maps length-variable packets directly to SONET synchronous payloads and
uses 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 data
link 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) and
STM-16c/STM-16 (2.5 Gbps), the rate of each level is four times that of the
immediate lower level.
Configuring a POS
Interface
Before you configure the link layer and network layer protocols on a POS interface,
you must configure its physical parameters. In addition, to have the interface
participate in backup, configure the backup parameters; to set up firewall on the
interface, configure packet filtering rules.