Cisco ASR 900 Series Configuration Guide

Restrictions for Clock Source Configuration
•
Only 4 ports can be configured in SONET line for clock source configuration per chassis.
•
You should configure the clock source line and network-clock sync together to receive the clock from
a remote port that is connected to the SONET port.
SONET Switching
SONET Switching is achieved on optical interface modules by circuit emulation. Circuit Emulation (CEM)
is a way to carry TDM circuits over packet switched network. CEM embeds TDM bits into packets, encapsulates
them into an appropriate header and then sends that through Packet Switched Network (PSN). The receiver
side of CEM restores the TDM bit stream from packets.
Modes of CEM:
• Structure Agnostic TDM over Packet (SAToP) (RFC 4553) – Structure-Agnostic TDM over Packet
(SAToP) mode is used to encapsulate T1/E1 or T3/E3 unstructured (unchannelized) services over packet
switched networks. In SAToP mode, the bytes are sent out as they arrive on the TDM line. Bytes do not
have to be aligned with any framing.
In this mode, the interface is considered as a continuous framed bit stream. The packetization of the
stream is done according to IETF RFC 4553. All signaling is carried transparently as a part of a bit
stream.
•
Circuit Emulation Service over Packet (CEP) (RFC 4842) - CEP mode is used to encapsulate SONET
payload envelopes (SPEs) like VT1.5 or VT2 or STS-1 or STS-Nc over packet switched networks. In
this mode, the bytes from the corresponding SPE are sent out as they arrive on the TDM line. The
interface is considered as a continuous framed bit stream. The packetization of the stream is done
according to IETF RFC 4842.
Table 2: Modes of CEM
PortsCEMMode
OC-48, OC-192CEPSTS-48C
OC-12, OC-48, OC-192CEPSTS-12C
OC-12, OC-48, OC-192CEPSTS-3C
OC-3, OC-12, OC-48, OC-192CEPSTS-1
OC-3, OC-12, OC-48, OC-192SAToPDS3
OC-3, OC-12, OC-48, OC-192SAToPDS3-T1
OC-3, OC-12, OC-48, OC-192CEPVT 1.5
OC-3, OC-12, OC-48, OC-192CESoPSNVT 1.5
OC-3, OC-12, OC-48, OC-192CESoPSNCT3-T1
1-Port OC-192 or 8-Port Low Rate CEM Interface Module Configuration Guide, Cisco IOS XE Everest 16.7.x (Cisco
ASR 900 Series)
21
Configuring SONET
SONET Switching

Cisco ASR 900 Series Specifications

General

Brand	Cisco
Model	ASR 900 Series
Category	Network Router
Language	English