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.

Effective from the 16.12.1 release,

• 21504 CEM pseudowires without protection (with SONET)

• 10752 CEM pseudowires with protection

is supported on the router.

Currently the Cisco A900-IMA3G-IMSG support a maximum of 1344 CEM pseudowires.

Note	The 21K CEM pseudowire’s can be achieved on the router by using the combination of the Cisco A900-IMA1Z8S-CX and A900-IMA3G-IMSG interface modules in multiple slot combinations.

A CEM class allows you to create a single configuration template for multiple CEM pseudowires. Follow these steps to configure a CEM class:

Note	The CEM parameters can be configured either by using CEM class or on CEM interface directly. The CEM parameters at the local and remote ends of a CEM circuit must match; otherwise, the pseudowire between the local and remote PE chassis does not come up.

enable
configure terminal
class cem mycemclass
payload-size 512 
dejitter-buffer 12
exit
interface cem 0/4/0
cem 0
cem class mycemclass
xconnect 10.10.10.10 200 encapsulation mpls
exit

An asynchronous mapping for a T3 or E3 in the payload capacity of an STS-1 signal is defined for clear-channel transport of T3 or E3 signals that meet the T3 or E3 requirements in GR-499-CORE. The asynchronous T3 or E3 mapping consists of nine subframes each of 125 μs. Each subframe contains 621 information (I) bits, a set of five stuff control (C) bits, one stuff opportunity (S) bit, and two overhead communication channel (O) bits. The remaining bits of the STS-1 payload capacity are fixed stuff (R) bits. The O-bits are reserved for future overhead communication purposes. The values of the R and O bits are undefined. In each subframe, the set of five C-bits are used to control the S-bit. CCCCC = 00000 is used to indicate that the S-bit is an information bit, while CCCCC = 11111 is used to indicate that the S-bit is a stuff bit. The value of the S-bit (if it is stuff bit) is undefined.

• BERT for both line and system directions is not supported until Cisco IOS XE Fuji 16.9.5 release.

• Card Protection is not supported.

• E3 CEP is not supported on optical or SDH controller.

If an alarm is detected in the DS3 end, the C2 bytes are used to inform the remote Provider Edge (PE). For this, the alarm mapping table has to be followed as shown in the figure below.

Pre-requisites:

The default mode is channelized mode. Use no channelized command to change to non-channelized mode.

To configure DS3 CEP for mode T3:

enable
controller MediaType 0/4/15
mode t3
controller t3 0/4/15
no channelized
cem-group 0 cep

To configure DS3 CEP for mode E3:

enable
controller MediaType 0/4/15
mode e3
controller e3 0/4/15
no channelized
cem-group 0 cep

Configuration of Overhead C2 and J1 Bytes:

You can configure overhead C2 and J1 bytes after you configure DS3 CEP.

enable
controller MediaType 0/4/15
mode e3
controller e3 0/4/15
threshold sd-ber 6
threshold sf-ber 3
no channelized
framing g751
cablelength short
cem group 0 cep
overhead j1 tx length 16
overhead j1 expected length 16

For loopback configuration, see Loopback on T3/E3 Interfaces section.