Jikai Li

Assembling TCP/IP packets in optical burst switched networks

Optical burst switching (OBS) is a promising paradigm for the next-generation Internet infrastructure. We study the performance of TCP traffic in OBS networks and in particular, the effect of assembly algorithms on TCP traffic. We describe three assembly algorithms in this paper and compare them using the same TCP traffic input. The results show that the performance of the proposed adaptive-assembly-period (AAP) algorithm is better than that of the min-burstlength-max-assembly-period (MBMAP) algorithm and the fixed-assembly-period (FAP) algorithm in terms of goodput and data loss rate. The results also indicate that burst assembly mechanisms affect the behavior of TCP in that the assembled TCP traffic becomes smoother in the short term, and more suitable for transmission in optical networks.

Traffic statistics and performance evaluation in optical burst switched networks

Optical burst switching (OBS) is a promising switching technology to exploit the potential benefits of optical communication and, at the same time, support statistical multiplexing of data traffic at a fine granularity. To quantify its benefits, the paper describes several typical burst assembly algorithms and studies their impact on the assembled burst traffic characteristics as well as the performance of TCP traffic. Also described is a proactive burst scheduling algorithm, called burst overlap reduction algorithm (BORA), which schedules locally assembled bursts in such a way as to reduce burst contention at downstream nodes in OBS networks. Furthermore, to provide analytical insights into performance evaluation of OBS networks, a burst loss model at an OBS node and its extension to different reservation protocols are presented.

Schedule burst proactively for optical burst switching networks

Optical burst switching (OBS) is a promising paradigm for the next-generation Internet infrastructure. In OBS, a key problem is to schedule bursts on wavelength channels with both fast and bandwidth efficient algorithms so as to reduce burst loss. To date, most scheduling algorithms avoid burst contention locally (or reactively). In this paper, we propose several novel algorithms for scheduling bursts in OBS networks with and without wavelength conversion capability. Our algorithms try to proactively avoid burst contention likely to occur at downstream nodes. The basic idea is to serialize the bursts on an outgoing link to reduce the number of bursts that may arrive at downstream nodes simultaneously (and thus reducing the burst contention and burst loss probability at downstream nodes). This can be accomplished by judiciously delaying locally assembled bursts beyond a pre-determined offset time at an ingress node using the electronic memory. Compared with the existing algorithms, our proposed algorithms can significantly reduce the loss rate while ensuring that maximum delay of a burst does not exceed its prescribed limit.

Logical topology design for dynamic traffic grooming in WDM optical networks

Traffic grooming in optical networks refers to consolidation of subwavelength client connections onto lightpaths. Depending on whether client connections are given in advance or randomly arrive/depart, traffic grooming is classified as static and dynamic. Dynamic traffic grooming has been traditionally performed through establishing/releasing lightpaths online. In this paper, the authors propose an alternate approach to design a static logical topology a priori and then route randomly arriving client connections on it to avoid frequent lightpath setup/teardown. Two problems are considered: 1) minimize resource usage constrained by traffic blocking requirements and 2) maximize performance constrained by given resources. These are formulated as integer linear-programming (ILP) problems. The numerical results show that the resource usage dramatically decreases when the blocking requirement is relaxed, and the grooming performance slowly increases when given more resources. In addition, the number of ports at client nodes has more profound impact on traffic grooming than the number of wavelengths.

Waveband switching networks with limited wavelength conversion

We study reconfigurable multi-granular optical cross-connects (MG-OXCs) in waveband switching networks with limited wavelength conversion and propose a heuristic algorithm to minimize the number of used wavelength converters while reducing the blocking probability.

Group schedule serialized traffic in optical burst switching networks

In this paper, a new scheduling algorithm, Serialized Batch Scheduling (SBS) for Optical Burst Switching (OBS) networks is proposed. SBS aggregates and serializes bursts along shared path into one composite burst which is switched as a single unit. There are two important processes in SBS namely, batching and serializing. While the batching process chooses proper set of bursts to form the composite burst, the serializing process determines how to organize the OBS bursts within the composite burst and generates a corresponding composite control packet. Several SBS batching and serializing schemes are introduced and analyzed. Our study shows that the guard band and bursts overlap can be reduced in the proposed SBS, and therefore, the packet loss rate and the number of switch reconfigurations can be significantly reduced.

A heuristic logical topology design algorithm for multi-hop dynamic traffic grooming in WDM optical networks

Traffic grooming in wavelength division multiplexing (WDM) optical networks controls how to consolidate client calls with sub-wavelength data rates onto lightpaths. It can be classified into static or dynamic traffic grooming depending on whether the client traffic is static or dynamic. The principal problem in traffic grooming is to construct a logical topology to route client traffic over a given physical topology. For dynamic traffic grooming, the logical topology may be dynamically configured, or designed a priori given the stationary traffic demands between client nodes (and reconfigured on relatively large time scale, e.g., on the order of hours, to adapt to traffic demands changes). Both approaches have their pros and cons. This paper studies the latter case and develops a heuristic algorithm to design logical topology, constrained by client traffic blocking probability requirement and the maximum by-pass traffic amount allowed at each client node. We have compared logical topologies designed the heuristic and an ILP model. The heuristic performance is impressive

Formulation of multi-hop dynamic traffic grooming in WDM optical networks

Traffic grooming in wavelength division multiplexing (WDM) optical networks studies consolidation of sub-wavelength client traffic onto lightpaths. The principal problem in traffic grooming is to construct a logical topology, and to route client traffic over the constructed logical topology. This paper studies dynamic traffic grooming where client traffic randomly arrives/departs. For dynamic traffic grooming, the logical topology may be dynamically configured, or designed a priori given the stationary traffic demands between client nodes (and reconfigured in relatively large time scale, e.g., on the order of hours, to adapt to changing traffic demands). This paper studies the latter case and formulates it into an integer linear programming (ILP) problem. The formulation minimizes the used network resource, constrained by the requirement of client traffic blocking probability, the maximum by-pass traffic amount allowed at each client node, and the number of ports at each client node. It also integrates wavelength assignment and addresses the most general sparse limited wavelength conversion

Double reservation in optical burst switching networks

Optical burst switching (OBS) is. a promising paradigm for the next-generation Internet infrastructure. In OBS, a key problem is how to reduce data loss, which can be caused by either channel scheduling failure or link/node failure. Most existing works in OBS consider either scheduling failure or link/node failure, but not both. We propose a novel resource reservation scheme, called double reservation (DR), to reduce the loss rate in OBS networks. In addition to improving the throughput performance for the whole network, it also can provide QoS for bursts with different loss rate requirements

Serialised batch scheduling algorithm for optical burst switching networks

A new scheduling algorithm called serialised batch scheduling (SBS) for optical burst switching (OBS) networks is proposed. SBS aggregates and serialises bursts along a shared path into one composite burst, which is switched as one unit. There are two major processes in SBS, namely, batching and serialising. While the batching process chooses a set of bursts to form the composite burst, the serialising process determines how to organise the OBS bursts within the composite burst and generates a corresponding control packet for this burst. Several SBS batching and serialising schemes are introduced and analysed here. The study by the authors shows that the guard band and burst overlap can be reduced in the SBS and, thus, the packet loss rate and the number of switch reconfigurations can be significantly reduced. In addition, it is indicated that the proposed SBS algorithm can be coupled with other OBS scheduling algorithms and reduce the requirements for a high-speed optical switch in OBS networks.