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Chapter 1
Overview
Figure 1-5
7300-2OC12POS-SMI
2-PORT OC-12 POS SM IR
Figure 1-6
7300-2OC12POS-SML
2-PORT OC-12 POS SM LR
SONET/SDH Overview
The POS specification addresses the use of PPP encapsulation over SONET/Synchronous Digital
Hierarchy (SDH) links. SONET is an American National Standards Institute (ANSI) standard
(T1.1051988) for optical digital transmission at hierarchical rates from 51.840 Mbps (STS-1) to 622.080
Mbps (STS-12) and greater. SDH is the international standard for optical digital transmission at
hierarchical rates from 155.520 Mbps (STM-1) to 2.488 Gbps (STM-16) and greater.
SONET is an octet-synchronous multiplex scheme that defines a family of standard rates and formats.
The basic rate for POS is that of STS-3c/STM-1, which is 155.520 Mbps. The available information
bandwidth is 149.760 Mbps, which is the STS-3c/STM-1 Synchronous Payload Envelope (SPE), the
payload portion of the SONET frame into which the octet-oriented user data is mapped. (Octet
boundaries are aligned with the SPE octet boundaries.)
The International Telecommunication Union Telecommunication Standardization Sector (ITU-T)
defines a series of SDH transmission rates beginning at 155.520 Mbps as follows:
SONET
STS-3c
STS-12c
STS-48c
1. ANSI-defined SONET specifications.
2. Currently supported by the OC12 POS line card.
OL-3437-01
7300-2OC12POS-SMI—Faceplate View
TX
0
RX
OIR
STATUS
CARRIER/
ACTIVE/
ALARM
LOOPBACK
7300-2OC12POS-SML—Faceplate View
TX
0
RX
OIR
STATUS
CARRIER/
ACTIVE/
ALARM
LOOPBACK
1
SDH Equivalent
STM-1
2
STM-4c
STM-16c
TX
1
RX
CARRIER/
ACTIVE/
ALARM
LOOPBACK
TX
1
RX
CARRIER/
ACTIVE/
ALARM
LOOPBACK
OC12 Packet Over SONET Line Card Installation and Configuration
SONET/SDH Overview
1-3
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