Nortel Networks Corporation

Cormac Kelly

Mark Brian Carson

John Courtney

The invention relates particularly to the switching of an SDH low order VC-3 using a high order switching apparatus, such as an STS switch. A low order VC-3 is aligned with a TU-3 pointer to form a TU-3. The TU-3 is mapped into a high order VC-3 type data structure which, in turn, is aligned with an AU-3 pointer to form an AU-3 type data structure. The AU-3 type data structure is suitable for switching by the high order switch. After switching, the AU-3 type data structure is combined with similar AU-3 type data structures and converted into an AU-4 suitable for transmission across an SDH/SONET network. Advantageously, the arrangement is such that each AU-3 pointer has the same fixed value. Hence, conversion to an AU-4 is achieved by a fixed pointer replacement operation. The invention significantly reduces the amount of pointer processing that is required in comparison with conventional techniques for switching low order VC-3s using low order VT/TU switches and in comparison with a ITU-T standards compliant approach for switching low order VC-3s using a high order switch. The present invention relates to the switching of low order data structures. In particular, the invention relates to switching an SDH low order VC-3 using a high order switching apparatus.

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Belfast, United Kingdom

Cormac Kelly