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SAToP Emulation on T1 and E1 Interfaces Overview


Structure-Agnostic time-division multiplexing (TDM) over Packet (SAToP), as defined in RFC 4553, Structure-Agnostic TDM over Packet (SAToP) is supported on the ACX Series Universal Metro routers with built-in T1 and E1 interfaces. SAToP is used for pseudowire encapsulation for TDM bits (T1, E1). The encapsulation disregards any structure imposed on the T1 and E1 streams, in particular the structure imposed by standard TDM framing. SAToP is used over packet-switched networks, where the provider edge (PE) routers do not need to interpret TDM data or participate in the TDM signaling.


ACX5048 and ACX5096 routers do not support SAToP.

Figure 1 shows a packet-switched network (PSN) in which two PE routers (PE1 and PE2) provide one or more pseudowires to customer edge (CE) routers (CE1 and CE2), establishing a PSN tunnel to provide a data path for the pseudowire.

Figure 1: Pseudowire Encapsulation with SAToP
Pseudowire Encapsulation
with SAToP

Pseudowire traffic is invisible to the core network, and the core network is transparent to the CEs. Native data units (bits, cells, or packets) arrive via the attachment circuit, are encapsulated in a pseudowire protocol data unit (PDU), and carried across the underlying network via the PSN tunnel. The PEs perform the necessary encapsulation and the decapsulation of the pseudowire PDUs and handle any other function required by the pseudowire service, such as sequencing or timing.