Semi-transparent time division multiplexer/demultiplexer

Abstract

A semi-transparent time division multiplexer/demultiplexer that transmits low rate tributaries from one location to another using a high rate aggregate connection, while preserving substantially all of the TOH and payload for each tributary signal. Transparency of the tributary TOH is accomplished by interleaving both the TOH and the Payload of each tributary into the high rate aggregate signal. Some TOH bytes may be tunneled or re-mapped into unused/undefined TOH locations in the aggregate signal to allow transparency of the TOH without corrupting the aggregate. Errors may be handled by tunneling BIP bytes into unused/undefined aggregate locations and updating the tunneled bytes with error masks calculated at each network elements. Alternatively errors may be forwarded by using an error mask generated from the tributary BIP locations and inserting the mask into the associated aggregate BIP locations. The mask in the aggregate BIP is updated with error masks calculated at each network elements. Re-timing of TOH to a synchronized clock in the tributary framer circuits can be accomplished using controlled slips of overhead frames, whereby an entire frame is dropped or added depending on the relationship of the received clock and the synchronized clock. DCC bytes may be re-timed by adding or deleting flag bytes occurring between respective DCC packets. Re-timing of the aggregate TOH to a transmit clock may be accomplished in a similar manner.