Communication is carried out in rounds.
Direct communication is possible from any processor to any other, and in each round a processor can send one message and receive one message. The off-line version of the problem arises when every processor knows the source and destination of every message. The on-line version of the problem is the focus of this paper. The problem has been well studied in the OCPC optical network model, but not for other contemporary network architectures which resolve message conflicts using other techniques. We first present a lower bound, proving that a constant factor of 1 is not achievable in general.