For maximum applicability, it is recommended that CESoE implementations
should support at least TDM line external and adaptive timing to enable the implementation
to be used in the majority of timing scenarios. Synchronization (and jitter
and wander) requirements are placed on a CESoE implementation by the MEF 8
and should conform to the ITU-T recommendations G.823 and G.824 for E1/E3 and
DS-1/DS-3, respectively.
Signaling CE applications interconnected over a CESoE service may exchange signaling
in addition to TDM data. The typical example is telephony applications that
exchange their state (e.g., off-hook/on-hook) in addition to TDM data carrying PCMencoded
voice.
With structure-agnostic emulation, signaling is not required to intercept or process
CE signaling. Signaling is embedded in the TDM data stream, and hence it is carried
end-to-end across the emulated circuit.
With structure-aware emulation, transport of Common Channel Signaling (CCS)
may be achieved by carrying the signaling channel with the emulated service (e.g.,
channel 23 for DS1 or channel 16 for E1). However, Channel Associated Signaling
(CAS), such as DS1 Robbed Bit Signaling or E1 CAS, requires knowing the relationship
of the timeslot to the trunk multiframe structure.
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