Data Planes in Telecom Networks

• Layer 3 for PSC (IP Routing)
• Layer 2.5 for PSC (MPLS)
• Layer 2 for L2SC (often Ethernet)
• Layer 1.5 for TDM (often SONET/SDH)
• Layer 1 for LSC (often WDM switch elements)
• Layer 0 for FSC (often port switching devices based on optical or mechanical technologies)

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In a “N” Layered Network Architecture, the services are grouped in a hierarchy of layers

– Layer N uses services of layer N-1

– Layer N provides services to layer N+1

A communication layer is completely defined by

(a) A peer protocol which specifies how entities at layer-N communicate.

(b) The service interface which specifies how adjacent layers at the same system communicate

 When talking about two adjacent layers,

(a) the higher layer is a service user, and

(b) the lower layer is a service provider

– The communication between entities at the same layer is logical

– The physical flow of data is vertical.