Nonblocking Switching Fabrics Research Articles

Multicast Space-Conversion-Space Strict-Sense Nonblocking Switching Fabrics with Multicast Opportunity in the Last Stage for Continuous Multislot Connections

This paper introduces two nonblocking switching fabric architectures designed for multicast connections. These connections are defined using the multislot connection approach, mainly applied in elastic optical networks. In contrast to earlier solutions, this approach assumes that multislot connections are consistently established in adjacent continuous slots. This implies that previously established solutions could not be applied. Our study presents a comprehensive theoretical framework applicable to the general case of three-stage switching fabrics. These fabrics feature external stages equipped with space switches, while the middle stage incorporates conversion switches that operate in the wavelength, time, or frequency domain. In addition, multicast capabilities are deliberately confined to the output-stage switch or switches. A fundamental contribution of this work lies in the formulation of the worst-case scenario, which serves as the foundational basis for deriving strict-sense nonblocking conditions governing such multicast switching fabrics. Our analysis formally demonstrates that the fundamental structure of the multicast nonblocking switching fabric aligns closely with that of the previously examined point-to-point fabric. The only difference is related to the ability to multicast within the output stage of the switching fabric.

Simultaneous Connections Routing in Wavelength–Space–Wavelength Elastic Optical Switches

In this paper, we investigate the three-stage, wavelength-space-wavelength switching fabric architecture for nodes in elastic optical networks. In general, this switching fabric has r input and output switches with wavelength-converting capabilities and one center-stage space switch that does not change the spectrum used by a connection. This architecture is most commonly denoted by the WSW1 (r, n, k) switching network. We focus on this switching fabric serving simultaneous connection routing. Such routing takes place mostly in synchronous packet networks, where packets for switching arrive at the inputs of a switching network at the same time. Until now, only switching fabrics with up to three inputs and outputs have been extensively investigated. Routing in switching fabrics of greater capacity is estimated based on routing in switches with two or three inputs and outputs. We now improve the results for the switching fabrics with four inputs and outputs and use these results to estimate routing in the switching fabric with an arbitrary number of inputs and outputs. We propose six routing algorithms based on matrix decomposition for simultaneous connection routing. For the proposed routing algorithms, we derive criteria under which they always succeed. The proposed routing algorithms allow the construction of nonblocking switching fabrics with a lower number of wavelength converters and the reduction of the overall switching fabric cost.

Wide-sense nonblocking and blocking converting-space-converting switching node architecture under XsVarSLOT algorithm

In this study, we evaluate the operation of the Converting-Space-Converting switching fabric architecture. The investigated switching fabric is suitable for all kinds of slot-operating switches, no matters the slots are wavelengths, time, or others. The switching fabric is evaluated in terms of the number of slots in the interstage links and the blocking probability. In the evaluation process, we used the proposed class of routing algorithms based on the functional decomposition of slots into subsets. The routing algorithm decomposes the slots in the interstage links into X subsets. The number of slots in each subset is evaluated by simulation, in order to obtain a blocking probability at the value of about 10−8, and analytically, in case the blocking probability is reduced to 0. The proposed algorithm can reduce the required number of slots in the interstage links by almost 84% in the nonblocking switching fabrics. However; when the blocking is acceptable, the proposed routing algorithm can also reduce this number of slots, but only when the values of blocking probability are very low.

Rearrangeable 2 times 2 elastic optical switch with two connection rates and spectrum conversion capability

In this study, we consider simultaneous connection routing in the three-stage switching fabric of the wavelength-space-wavelength architecture for elastic optical switches, which serve connections that can occupy different spectrum widths. Recently, the upper bound of the rearrangeability conditions was derived and proved for a switching fabric serving a limited number of connection rates. A control algorithm based on matrix decomposition was also proposed. In addition, the necessary and sufficient conditions were derived and proved for a switching fabric with a size of 2 times 2 serving only two connection rates, but only when the ratios between the connection rates and link capacity are integers. In this study, we extend these results to an arbitrary ratio between the connection rates and link capacity. The number of frequency slot units required in the interstage links is much lower than that in the strict-sense nonblocking switching fabrics. We also propose modifications to the control algorithm, which further reduces the number of frequency slot units required in many cases. Finally, we extend the results for 2 times 2 switching fabrics to those with a size of r times r.

Asymmetrical Space-Conversion-Space SCS1 Strict-Sense and Wide-Sense Nonblocking Switching Fabrics for Continuous Multislot Connections

Recently, Danilewicz et al. have proposed two strict-sense nonblocking structures of switching fabrics, called Space-Wavelength-Space 1 and Space-Wavelength-Space 2, for elastic optical network nodes. This paper considers one of the two previously presented structures. The node uses a three-stage switching fabric that applies space switching in the first and third stages and wavelength switching in the second stage (an S-W-S switching fabric). In elastic optical networks, an optical path can use a frequency slot spread over m adjacent frequency slot units. Such a connection is called an m-slot connection. In this paper, a more general case is presented in which conversion in the middle-stage switches can be made for one of the different domains (frequency, time, etc.). However, the m-slot connections are a basis for the presented theory. This theory concerns space-conversion-space (S-C-S) switching fabrics in which conversion can be performed for different domains. Danilewicz et al. considered S-W-S switching fabrics in which 1 ≤ m ≤ m max . For the S-C-S switching fabrics discussed in this paper, we derive and prove strict-sense nonblocking conditions when m-slot connections are set up, in which m min ≤ m ≤ m max . Strict-sense nonblocking conditions are derived for asymmetrical S-C-S switching fabrics. In addition, wide-sense nonblocking conditions for switching fabrics with functional decomposition of center-stage switches are presented. It is shown that the wide-sense nonblocking switching fabrics may require less than a half of the switches in the middle-stage compared with the strict-sense nonblocking switching fabrics.

Rearrangeability of Wavelength-Space-Wavelength Switching Fabric Architecture for Elastic Optical Switches

In this paper, we consider the necessary and sufficient rearrangeability conditions for the wavelength-space-wavelength switching fabric, called the WSW2 switching fabric, for elastic optical network nodes. We derive and prove the lower bound of the necessary conditions for such switching fabrics to be rearrangeable. We also show the upper bound of the sufficient conditions for the rearrangeability of the switching fabric with two input and two output switches. For simultaneous connection routing, we propose a routing algorithm that always ends with success in switching fabrics, which fulfill the sufficient conditions. Finally, we extend the proposed algorithm to the switching fabric with $r$ input and $r$ output switches, and we derive the conditions under which this routing algorithm always ends in success. The required number of center-stage switches is significantly lower than that in the strict-sense nonblocking switching fabrics. To our knowledge, the proposed routing algorithm is the first one which ends with success for any connection set, within the provided sufficient conditions.

Supplement to “Asymmetrical Space-Conversion Space SCS1 Strict-Sense and Wide-Sense Nonblocking Switching Fabrics for Continuous Multislot Connections” - the SCS2 Switching Fabrics Case

Supplement to “Asymmetrical Space-Conversion Space SCS1 Strict-Sense and Wide-Sense Nonblocking Switching Fabrics for Continuous Multislot Connections” - the SCS2 Switching Fabrics Case

Rearrangeability of 2×2 W-S-W Elastic Switching Fabrics with Two Connection Rate

The rearreangeable conditions for the 2×2 three-stage switching fabric of a W-S-W architecture for elastic optical switches are considered in this paper. Analogies between the switching fabric considered and the three-stage Clos network are shown. On the other hand, differences are also shown, which presented the modifications required in the control algorithm used in rearrangeable networks. The rearrangeable conditions and the control algorithm are presented and proved. Operation of the proposed control algorithm is shown based on a few examples. The required number of frequency slot units in interstage links of rearrangeable switching fabrics is much lower than in the strict-sense non-blocking switching fabrics characterized by the same parameters.

High-Radix Nonblocking Integrated Optical Switching Fabric for Data Center

To accomplish high-bandwidth and low-latency communications among tens or even hundreds of nodes with low power consumption, dual radial and angular grating optical network (DRAGON), a new integrated high-radix strictly nonblocking optical switching fabric, is proposed in this paper. The topology and routing algorithms of DRAGON are discussed, and a formal proof for the strictly nonblocking property is presented. With the loss model developed, we show DRAGON has significantly lower worst-case loss as well as average loss compared with other widely studied integrated nonblocking switching fabrics. In addition, our crosstalk analysis also suggests a lower crosstalk of DRAGON. For example, for 32 wavelength division multiplexing channels, both the worst-case loss and average loss of ${\text{180}}\times {\text{180}}$ DRAGON are around 20 dB lower than crossbar of the same size, and 28 dB lower than ${\text{128}}\times {\text{128}}$ Benes. Furthermore, due to the strictly nonblocking property, DRAGON has advantages of smaller communication latency and larger throughput compared with Benes switching fabric.

Wide-sense nonblocking elastic optical switch

In this paper, we address the problem of wide-sense nonblocking operation of the elastic optical switch. The switch 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. Two control algorithms are proposed, namely, 2-split and 3-split. For these algorithms we derived wide-sense nonblocking conditions and compared them with strict-sense nonblocking ones. The results show that the 3-split algorithm reduces the required number of FSUs to up to almost 70% of the FSUs required in the strict-sense nonblocking switching fabrics. Application of the proposed elastic optical switch in optical datacenter networks is also proposed.

Maximum size matching is unstable for any packet switch

Input-queued packet switches use a matching algorithm to configure a nonblocking switch fabric (e.g., a crossbar). Ideally, the matching algorithm will guarantee 100% throughput for a broad class of traffic, so long as the switch is not oversubscribed. An intuitive choice is the maximum size matching (MSM) algorithm, which maximizes the instantaneous throughput. It was shown (McKeown et al. (1999)) that with MSM the throughput can be less than 100% when N /spl ges/ 3, even with Terms-Instability,benign Bernoulli i.i.d. arrivals. In this letter, we extend this result to N /spl ges/ 2, and hence show it to be true for switches of any size.

Some topological properties of bitonic sorters

The paper proves some topological properties of bitonic sorters, which have found applications in constructing, along with banyan networks, internally nonblocking switching fabrics in future broadband networks. The states of all the sorting elements of an N/spl times/N bitonic sorter are studied for four different input sequences {a/sub i/}/sub i=l//sup N/, {b/sub i/}/sub i=l//sup N/, {c/sub i/}/sub i=l//sup N/, and {d/sub i/}/sub i=l//sup N/ where a/sub i/=i-1, b/sub i/=N-i, and the binary representations of c/sub i/ and d/sub i/ are the bit reverse of those of a/sub i/ and b/sub i/, respectively. An application of these topological properties is to help design efficient fault diagnosis procedures. We present an example for detecting and locating a single faulty sorting element under a simple fault model where all sorting elements are always in the straight state or the cross state.

Performance evaluation of input and output queueing techniques in ATM switching systems

Modeling alternatives for a fast packet switching system are analyzed. A nonblocking switch fabric that runs at the same speed as the input/output links is considered. The performance of the considered approaches are derived by theoretical analysis and computer simulations. Performance comparison between input queueing approaches with different selection policies are presented. Novel input and output queueing techniques are also proposed. In particular it is shown that, depending on the implementation, the input queueing approach studied in this paper achieves the same performance as the optimum (output) queueing alternative, without resorting to a faster packet switch fabric.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>