Marc Vandenhoute

Control architecture in optical burst-switched WDM networks

Optical burst switching (OBS) is a promising solution for building terabit optical routers and realizing IP over WDM. In this paper, we describe the basic concept of OBS and present a general architecture of optical core routers and electronic edge routers in the OBS network. The key design issues related to the OBS are also discussed, namely, burst assembly (burstification), channel scheduling, burst offset-time management, and some dimensioning rules. A nonperiodic time-interval burst assembly mechanism is described. A class of data channel scheduling algorithms with void filling is proposed for optical routers using a fiber delay line buffer. The LAUC-VF (latest available unused channel with void filling) channel scheduling algorithm is studied in detail. Initial results on the burst traffic characteristics and on the performance of optical routers in the OBS network with self-similar traffic as inputs are reported in the paper.

Efficient multicast schemes for optical burst-switched WDM networks

In this paper, we study several multicast schemes in optical burst-switched WDM networks taking into consideration of the overheads due to control packets and guard bands (GBs) of bursts on separate channels (wavelengths). A straightforward scheme is called separate multicasting (S-MCAST) where each source node constructs separate bursts for its multicast (per each multicast session) and unicast traffic. To reduce the overhead due to GBs (and control packets), one may piggyback the multicast traffic in bursts containing unicast traffic using a scheme called multiple unicasting (M-UCAST). The third scheme is called tree-shared multicasting (TS-MCAST) whereby multicast traffic belonging to multiple multicast sessions can be mixed together in a burst, which is delivered via a shared multicast tree. The multicast schemes (M-UCAST and TS-MCAST) are compared with S-MCAST in terms of bandwidth consumed and processing load.

Design and analysis of optical burst-switched networks

Optical burst switching (OBS) is a promising solution for building terabit optical routers and realizing IP over D- WDM. In this paper, we describe the basic concept of OBS and a general architecture of optical routers. The key design issues related to the OBS are discussed, notably, burstification, offset-time management and channel scheduling. A simple channel scheduling algorithm called LAUC (Latest Available Unscheduled Channel) algorithm is presented, which is also called Horizon algorithm in the literature. The performance of optical routers under random and self-similar traffic is thoroughly studied via computer simulations. Our study indicates that the distribution of burst length is not exponential any more. For the FDL (fiber delay line) optical buffer, the burst loss ratio is quite sensitive to the traffic characteristic of bursts when using the LAUC algorithm.

Tree-shared multicast in optical burst-switched WDM networks

In this paper, we propose a new multicast scheme called tree-shared multicasting (TS-MCAST) in optical burst-switched wavelength-division-multiplexing networks, taking into consideration overheads due to control packets and guard bands (GBs) associated with data bursts. In TS-MCAST, multicast traffic belonging to multiple multicast sessions from the same source-edge node to possibly different destination-edge nodes can be multiplexed together in a data burst, which is delivered via a shared multicast tree. To support TS-MCAST, we propose three tree-sharing strategies based on equal coverage, super coverage, and overlapping coverage, and present a simple shared multicast tree-construction algorithm. For performance comparison, we consider two other multicast schemes: separate multicasting (S-MCAST) and multiple unicasting (M-UCAST). We show that TS-MCAST outperforms S-MCAST and M-UCAST in terms of bandwidth consumed and processing load (i.e., number of control packets) incurred for a given amount of multicast traffic under the same unicast traffic load with static multicast sessions and membership.

Bandwidth-efficient dynamic tree-shared multicast in optical burst-switched networks

We study three multicast schemes, namely separate multicasting (S-MCAST), multiple uni-casting (M-UCAST), and tree-share multicasting (TS-MCAST), in optical burst-switched WDM networks taking into consideration the overheads due to control packets and guard band (GBs) of bursts on separate channels (wavelengths). In TS-MCAST, we describe four tree sharing strategies based on equal coverage (EC), super coverage (SC), overlapping coverage (OC) and overlapping coverage by maximization (OC-MAX) for deciding which multicast sessions should mix their multicast traffic, and also consider an algorithm to construct shared trees (STs). Jeong, Xiong, Cankaya, Vandenhoute and Qiao (see Proc. of IEEE ICC 2000, p.1289-91, 2000) proposed the tree sharing strategies and reported the performance of three multicast schemes for static multicast sessions and membership. In this paper, we propose efficient heuristic algorithms for managing dynamic sessions and memberships under the TS-MCAST scheme, and evaluate the efficiency of the heuristic algorithms and compare the TS-MCAST scheme with the other two schemes in terms of the bandwidth consumed and processing load assuming an unlimited bandwidth.

Distributed shared multicast tree construction protocols for tree-shared multicasting in OBS networks

Tree-shared multicasting in OBS networks can achieve bandwidth savings, less processing load, and lower burst blocking (loss) probability. In this paper, we propose several distributed shared multicast tree construction protocols, namely greedy-prune, non-member-join, all-member-join, closest-member on-tree (CMOT), and closest-node on-tree (CNOT), for tree-shared multicasting in OBS networks. For performance comparison, we also consider an optimal shared tree which is modeled as Steiner minimal tree. We evaluate the proposed protocols using simulations in terms of cost of the shared tree to the optimal shared tree. Simulations show that the CNOT and CMOT protocols outperform the other three proposed protocols in terms of the cost of the shared tree, and perform close to cost of the optimal shared tree.

Evaluation of multicast schemes in optical burst-switched networks: the case with dynamic sessions

In this paper, we evaluate the performance of several multicast schemes in optical burst-switched WDM networks taking into accounts the overheads due to control packets and guard bands (Gbs) of bursts on separate channels (wavelengths). A straightforward scheme is called Separate Multicasting (S-MCAST) where each source node constructs separate bursts for its multicast (per each multicast session) and unicast traffic. To reduce the overhead due to Gbs (and control packets), one may piggyback the multicast traffic in bursts containing unicast traffic using a scheme called Multiple Unicasting (M-UCAST). The third scheme is called Tree-Shared Multicasting (TS-MCAST) wehreby multicast traffic belonging to multiple multicast sesions can be mixed together in a burst, which is delivered via a shared multicast tree. In [1], we have evaluated several multicast schemes with static sessions at the flow level. In this paper, we perform a simple analysis for the multicast schemes and evaluate the performance of three multicast schemes, focusing on the case with dynamic sessions in terms of the link utilization, bandwidth consumption, blocking (loss) probability, goodput and the processing loads.

Progressive Introduction of Optical Packet Switching Techniques in WDM Networks

The transport network, mainly based on optical infrastructure, see a traffic increase, which introduces new requirements and challenges. This paper provides a summary of the trends that will bring bandwidth optimisation in WDM core networks, and will thus require the progressive introduction of optical packet switching techniques.