Circuit Emulation (Cpipe) Services
Page 120 7210 SAS M Services Guide
Circuit Emulation (Cpipe) Services
Note: Circuit Emulation Services are not supported on 7210 SAS-M devices configured in access
uplink mode.
Cpipe Service Overview
Cpipe service is the Alcatel-Lucent implementation of TDM pseudowire VLL as defined in the
IETF PWE3 working group.
The 7210 SAS M can support TDM circuit applications that are able to transport delay sensitive
TDM traffic over a packet network. For example, in case of business that use legacy T1/E1
interfaces, Cpipe services provide transport services. Cpipe services over MPLS or GRE tunnels
are supported.
The TDM traffic is transported encapsulated in a TDM VLL over the packet switched network
(PSN). The entire T1/E1 frame or part of a frame (n × 64 kb/s) is carried as a TDM VLL over the
PSN. At the far end, the transport layer frame structure is regenerated when structured circuit
emulation is used, or simply forwarded as part of the payload when unstructured circuit emulation
is used.
Cpipe Service Modes
Cpipe services support unstructured circuit emulation mode (SAToP) as per RFC 4553, Structure-
Agnostic Time Division Multiplexing (TDM) over Packet (SAToP), and structured circuit
emulation mode (CESoPSN) for DS1, E1 and n × 64 kb/s circuits as per RFC 5086, Structure-
Aware Time Division Multiplexed (TDM) Circuit Emulation Service over Packet Switched
Network (CESoPSN).
Unstructured Mode (SAToP)
Structure-agnostic TDM over Packet (SAToP) is an unstructured circuit emulation mode used for
the transport of unstructured TDM or structured TDM (where the structure is ignored).
Note: The word agnostic is used in RFC 4553, but it is not used in the literal sense. The meaning
of agnostic in this case is .unaware or independent. Therefore, structure-agnostic is used to mean
structure-unaware or structure-independent.
As a structure-unaware or structure-independent service, SAToP service does not align to any
framing; the framing mode for the port is set to unframed. For structured TDM, SAToP disregards
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