Maintaining Packet Order in Reservation-Based Shared-Memory Optical Packet Switch

Xiaoliang WANG  Xiaohong JIANG  Susumu HORIGUCHI  

IEICE TRANSACTIONS on Communications   Vol.E91-B   No.9   pp.2889-2896
Publication Date: 2008/09/01
Online ISSN: 1745-1345
DOI: 10.1093/ietcom/e91-b.9.2889
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Switching for Communications
OPS,  Shared-Memory Optical Packet switch,  Mis-sequence,  

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Shared-Memory Optical Packet (SMOP) switch architecture is very promising for significantly reducing the amount of required optical memory, which is typically constructed from fiber delay lines (FDLs). The current reservation-based scheduling algorithms for SMOP switches can effectively utilize the FDLs and achieve a low packet loss rate by simply reserving the departure time for each arrival packet. It is notable, however, that such a simple scheduling scheme may introduce a significant packet out of order problem. In this paper, we first identify the two main sources of packet out of order problem in the current reservation-based SMOP switches. We then show that by introducing a "last-timestamp" variable and modifying the corresponding FDLs arrangement as well as the scheduling process in the current reservation-based SMOP switches, it is possible to keep packets in-sequence while still maintaining a similar delay and packet loss performance as the previous design. Finally, we further extend our work to support the variable-length burst switching.