Slot Synchronization of a WDM Packet-Switched Slotted Ring

We introduce a hybrid of one-way and two-way reservations for slotted optical burst switching (S-OBS). Our hybrid method adds one-way mode to the two-way reservation, which has the idle time for ingress nodes to wait outcomes on preparing and scheduling at each node on the routes to egress nodes for the data segment used in S-OBS. The one-way mode enables ingress nodes to transmit data segments without waiting any outcome of the reservation of the channel resources on routes to egress nodes, though data segments are transmitted with waiting such outcomes in the two-way mode. The addition of the one-way mode reduces the idle time for ingress nodes to wait the acknowledgements of data segments in the two-way reservation method of S-OBS. We also explain the order of transmitting at the ingress node and receiving at the egress node for the correct order of the data segment. We analyze the end-to-end delay of the hybrid method, and show that the hybrid method decreases the end-to-end delay. IntroductionThe paradigm shift to the Internet traffic demands dynamic wavelength-division multiplexing (dWDM) without optical buffer for transporting data across large distances in the near future [1][2][3]. It is critical to eliminate opticselectronics-optics conversion at intermediate nodes in the end-to-end route for harnessing vast bandwidth capacities of optical core networks, and to overcome a number of technological constraints such as the limited optical buffering that is currently implemented using optical delay lines.In OBS network, a burst consists of two parts, a header and a data burst [2]. The header is called the control packet (CP) and is transmitted separately from the data, which is called the data burst. The CP is delivered out of band and precedes the data burst by an offset time. The CP carries, the offset time and the data burst length to reserve the bandwidth along the route for the corresponding data burst. Consequently, no buffering is needed for the burst at intermediate nodes.In OBS reservation protocols, there are unacknowledged and acknowledged reservation protocols [4]. In the unacknowledged reservation protocols, such as the one-way reservation, after the offset time passes, the burst is transmitted, but it may be blocked at any node along the route in case of contention of reservation requests, because the core is assumed to be bufferless. On the other hand, in the acknowledged reservation protocols, such as the two-way reservation [5,6]. The two-way reservation has an advantage of highly reliable transit of data burst.Similar to optical packet-switched networks, OBS networks can be divided into slotted and unslotted categories [7]. Slotted OBS offers high band efficiency compared with unslotted OBS. In slotted OBS (S-OBS) networks [7-9], control and data channels are divided into fixed-size timeslots. The data burst is divided into fixed-size data segments, which is length of the timeslot, and then the reservation is needed for each data segment, not a whole burst. In [9], a reservation scheme is i...

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“…This is accomplished by synchronizers like the ones described in [10][11][12], and the S-OBS operates by the unit timeslot.…”

Section: Introductionmentioning

confidence: 99%