Wojciech Kabacinski

Wide-sense and strict-sense nonblocking operation of multicast multi-log/sub 2/ n switching networks

Multicast connections are used in broad-band switching networks as well as in parallel processing. We consider wide-sense and strict-sense nonblocking conditions for multi-log/sub 2/ N switching networks with multicast connections. We prove that such networks are wide-sense nonblocking if they are designed by vertically stacking at least t /spl middot/ 2/sup n-t-1/ + 2 /sup n-2t-1/ planes of a log/sub 2/ N networks together, where 1 /spl les/ t /spl les/ [n/2] and t defines the size of a blocking window K = 2/sup t/. For t = [n/2] and n even, and for [n/2] /spl les/ t /spl les/ n the number of planes must be at least t /spl middot/ 2/sup n-t-1/ + 1 and 2/sup t/ + (n - t - 1) /spl middot/ 2/sup n-t-1/ - 2/sup 2t-n-1/ + 1, respectively. In the case of strict-sense nonblocking switching networks, the number of planes is at least N/2. The results obtained in this paper show that in many cases number of planes in wide-sense nonblocking switching networks is less than those for t = [n/2] considered by Tscha and Lee (see ibid., vol.47, p.1425-31, Sept. 1999). The number of planes given in the paper is the minimum number of planes needed for wide-sense nonblocking operation provided that Algorithm 1 is used for setting up connections. The minimum number of planes for such operation in general is still open issue.

Modified dilated Benes networks for photonic switching

A modified dilated Benes (1965) network composed of directional couplers is proposed. This structure is introduced to improve the signal-to-noise ratio (SNR) characteristics of dilated Benes networks. A new estimation of the SNR for dilated Benes networks is derived, and it is shown that this SNR is much worse than that previously known. The SNR for modified dilated Benes networks is estimated and compared to dilated Benes and other network architectures. Some other properties including the number of switching elements required, number of crossovers, and system attenuation are also derived and analyzed. Most of the characteristics are shown to be similar to dilated Benes networks and better than those of other well-known networks fabricated in Ti:LiNbO/sub 3/.

The Routing Algorithm and Wide-Sense Nonblocking Conditions for Multiplane Baseline Switching Networks

A new control algorithm for the multiplane baseline switching network is proposed in this paper. This algorithm chooses a plane for a new connection in such a way that this new connection blocks the lowest number of possible future connections in the plane. We have proved, that when using this algorithm connections can be routed without blocking when the number of planes in the switching network is the same as in the rearrangeable one for even number of stages. When the switching network contains the odd number of stages, required number of planes is greater than in the rearrangeable switching network but less than in the strict-sense nonblocking one. Different implementations of the proposed algorithm are also considered. It should be noted, that the algorithm can determine the plane for a new connection in O(N0.5) time or even in O(1) time depending on the implementation. The overall time complexity of the proposed algorithm is from O(N3.5 log2 N) to O(N log2 N) depending on its implementation and number of processors used

A growable ATM switching fabric architecture

A growable ATM or fast packet switching fabric architecture is proposed. The fabric has a two-sided structure and allows for the modular growth of its size from small to very large number of ports. The fabric is expanded by connecting additional basic fabrics to the existing structure by some interconnecting modules. The expansion process does not disturb the existing cabling. The architecture makes it also possible to adjust the system throughput. The hardware complexity of the new fabric is moderate and is discussed in the paper. Some important implementation issues such as the physical design and reliability are also presented in the paper. >

A New Control Algorithm for Wide-Sense Nonblocking Multiplane Photonic Banyan-Type Switching Fabrics with Zero Crosstalk

A new control algorithm for log2(N, 0, p) switching networks composed of 2 x 2 switching elements has been proposed recently. Under this algorithm, log2(N,0,p) switching networks with even number of stages are wide-sense nonblocking (WSNB) if p is the same as for the rearrangeable nonblocking (RNB) one. The considerred algorithm and WSNB conditions did not take into account crosstalk constraint, which is an important factor in photonic switching. This paper enhanced this algorithm to the case when crosstalk in the switching fabric is not allowed. WSNB conditions for this enhanced algorithm are also derived. It is shown, that the number of planes required is less than those derived earlier in other papers for WSNB multiplane banyan- type switching fabrics under crosstalk constraint. Under this algorithm, log2( N,0,p) switching networks with odd number of stages and with zero crosstalk are WSNB if p is the same as for RNB one.

On nonblocking switching networks for multichannel connections

This paper deals with switching networks for multichannel connections. The conditions under which the three-stage switching network is nonblocking for s-channel connections are given. Switching networks that are nonblocking in the strict sense as well as the switching networks nonblocking in the wide sense are considered. The conditions for two-sided and for one-sided switching networks are derived. >

The strict-sense nonblocking elastic optical switch

In this paper, we address the problem of the strict-sense nonblocking operation of an elastic optical switch. Elastic optical switches are used as nodes in elastic optical networks (EONs), where fine granular frequency slots or flexible grids are used in opposite to the traditional optical networks, where fixed grids are used. The switch architecture considered in this paper consists of waveband converting switches in input and output stages, while in the center stage there is only one wavelength selective space switch without wavelength conversion capabilities. We derive the number of frequency channels k needed in interstage links to ensure the nonblocking operation of the switch when input and output links have n frequency channels and a frequency slot of one connection is not greater than m frequency channels. Both, necessity and sufficient conditions are proved.

Rearranging algorithms for log 2 (N, 0, p) switching networks with even number of stages

In this paper we consider the rearrangeable multi-plane banyan-type switching fabrics, called also log2(N, 0, p) switching networks, with even number of stages. For such networks different rearranging algorithms have been proposed for both: one-at-a-time and simultaneous connection models. In this paper we consider the one-at-a-time connection model, where connections arrive to the system one-by-one, and in case of blocking rearrangements are realized. To our knowledge, known algorithms require several rearrangements, and the number of such rearrangements have not been considered in the literature. We propose the new rearranging algorithm for the multi-plane banyan-type switching fabric composed of even number of stages. This algorithm leads to success using only one rearrangement. We also introduce the modified version of this new algorithm, in which rearrangement of an existing connecting path can be realized without its interruption.

The new packet scheduling algorithms for VOQ switches

We present two new scheduling algorithms, the Maximal Matching with Random Selection (MMRS) and the Maximal Matching with Round-Robin Selection (MMRRS). These algorithms provide high throughput and fair access in a packet switch that uses multiple input queues. They are based on finding a maximal matching between input and output ports without iterations. Simulations performed show that for large load these algorithms perform better than other iterative algorithms.

Comments on "Wide-sense nonblocking multicast Log/sub 2/(N,m,p) Networks"

Recently, Hwang and Lin derived nonblocking conditions for multicast connections in Log2(N,m,p) networks. They improved some conditions obtained earlier by Kabacinacuteski and Danilewicz. In this letter, we identify some inaccuracy in present results concerning wide-sense nonblocking Log2(N,m,p) multicast networks, and give the correct results