Three types of concatenation schemes are possible under SONET and SDH. These are:
Standard contiguous concatenation
Arbitrary contiguous concatenation
These concatenation schemes are described in detail next.
SONET and SDH networks support contiguous concatenation whereby a few standardized “concatenated” signals are defined, and each concatenated signal is transported as a single entity across the network [ANSI95a, ITU-T00a]. This was described briefly in the previous chapter.
The concatenated signals are obtained by “gluing” together the payloads of the constituent signals, and they come in fixed sizes. In SONET, these are called STS