Overview of Circuit Emulation
Circuit Emulation (CEM) is a technology that provides a protocol-independent transport over IP/MPLS networks. It enables proprietary or legacy applications to be carried transparently to the destination, similar to a leased line.
CEM provides a bridge between a Time-Division Multiplexing (TDM) network and Multiprotocol Label Switching (MPLS) network. The chassis encapsulates the TDM data in the MPLS packets and sends the data over a CEM pseudowire to the remote Provider Edge (PE) chassis. As a result, CEM functions as a physical communication link across the packet network.
The chassis supports the pseudowire type that utilizes CEM transport: Structure-Agnostic TDM over Packet (SAToP).
L2VPN over IP/MPLS is also supported on the interface modules.
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R0 to R1 is 5 seconds
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R1 to R0 is 10 seconds
Structure-Agnostic TDM over Packet
Structure-Agnostic TDM over Packet (SAToP) encapsulates Time Division Multiplexing (TDM) bit-streams as pseudowires over public switched networks. It disregards any structure that may be imposed on streams, in particular the structure imposed by the standard TDM framing.
The protocol used for emulation of these services does not depend on the method in which attachment circuits are delivered to the Provider Edge (PE) chassis. For example, a T1 attachment circuit is treated the same way for all delivery methods, including copper, multiplex in a T3 circuit, a virtual tributary of a SONET circuit, or unstructured Circuit Emulation Service (CES).
In SAToP 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 out transparently as a part of a bit stream.
CEM PW Scale
Effective from the 16.12.1 release,
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21504 CEM Psuedowire (PWs) without protection (with SONET)
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10752 CEM PWs with protection
will be supported on the Cisco router.
Currently the Cisco A900-IMA1Z8S-CX support a maximum of 5376 CEM PWs.
4 Interface Modules can be used on the ASR 903 and NCS 4206 routers to achieve the 21K CEM PWs.
This can be achieved by:
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Configuring CEM circuits on all the 192 STS on the 9th port of the Cisco A900-IMA3G-IMSG which supports OC192.
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Configuring CEM circuits on all the 4 OC48 ports of the Cisco A900-IMA3G-IMSG which supports OC192.
Note |
The 21K CEM PW’s can be achieved on the ASR 907/921 and NCS 4216 by using the combination of the Cisco A900-IMA1Z8S-CX and A900-IMA3G-IMSG IMs in multiple slot combinations. |
Restrictions for PW Scale Increase
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When you configure the 21505th T1 PW command, your configuration may fail even though no error message is prompted