Priority switching scheduler

We define a novel core network router scheduling architecture called priority switching scheduler (PSS), to carry and isolate time constrained and elastic traffic flows from best-effort traffic. To date, one possible solution has been to implement a core DiffServ network with standard fair queuing and scheduling mechanisms as proposed in the well-known “A Differentiated Services Code Point (DSCP) for Capacity-Admitted Traffic” from RFC5865. This architecture is one of the most selected solutions by internet service provider for access networks (e.g., customer-premises equipment) and deployed within several performance-enhancing proxies (PEPs) over satellite communications (SATCOM) architectures. In this study, we argue that the proposed standard implementation does not allow to efficiently quantify the reserved capacity for the AF class. By using a novel credit-based shaper mechanism called burst limiting shaper (BLS) to manage the AF class, we show that PSS can provide the same isolation for the time constrained EF class while better quantifying the part allocated to the AF class. PSS operates both when the output link capacity is fixed (e.g., wire links and terrestrial networks) or might vary due to system impairments or weather condition (e.g., wireless or satellite links). We demonstrate the capability of PSS through an emulated SATCOM scenario with variable capacity and show the AF output rate is less dependent on the EF traffic, which improves the quantification of the reserved capacity of AF, without impacting EF traffic.     

Stochastic neural scheduler for real-time input-buffered packetswitching

A stochastic neural scheduler is presented which can be used to resolve conflicts in an input-buffered switch. It has smaller mean and variance of response time than neural schedulers recently proposed by Leung [1994, 1998]     

Neural parallel-hierarchical-matching scheduler for input-bufferedpacket switches

Input-buffered packet switches boosted with high-performance schedulers achieve near-100% throughput. Several authors have proposed the use of neural schedulers. These schedulers have a fast theoretical convergence, but the standard deviation of the number of iterations required can be arbitrarily large. In a previous paper, the authors proposed a hybrid digital-neural scheduler, HBRTNS, with bounded response time: O(N) clock steps. As an evolution of that concept, the authors present a two-stage neural Parallel-Hierarchical-Matching scheduler (nPHM), which generates high quality solutions in few clock steps. We present numerical comparisons with diverse state-of-the-art algorithms and the ideal output-buffered case     

Ant colony optimization based packet scheduler for peer-to-peer video streaming

This letter describes a new packet scheduling algorithm for enhancing the quality of distributed peer-to-peer video streaming. The algorithm was designed for when streaming server peers use error recovery such as automatic-repeat-request (ARQ) rather than error protection to avoid overburdening network resources. Ant colony optimization was used for scheduling groups of packets to reflect the channel status and error recovery effect of multiple server peers heuristically. Simulation results show that the proposed algorithm can enhance the quality of distributed video streaming services.     

High performance real-time neural scheduler for ATM switches

Input-buffered asynchronous transfer mode (ATM) packet switches are simpler than output-buffered switches. However, due to HOL blocking, their throughput is poor. Neural schedulers represent a promising solution for high throughput input-buffered switching, but their response time variance is too high for realistic hard real-time constraints. To overcome this problem, we formulate and evaluate a new neural scheduler with bounded response time     

Techniques for optical packet switching and optical burst switching

Wavelength-division multiplexing appears to be the solution of choice for providing a faster networking infrastructure that can meet the explosive growth of the Internet. Several different technologies have been developed so far for the transfer of data over WDM. We survey two new technologies which are still in the experimental stage-optical packet switching and optical burst switching-and comment on their suitability for transporting IP traffic     

SRR: an O(1) time-complexity packet scheduler for flows in multiservice packet networks

We present a novel fair queueing scheme, which we call Smoothed Round Robin (SRR). Ordinary round-robin schedulers are well known for the burstiness of their scheduling output. In order to overcome this problem, SRR codes the weights of the flows into binary vectors to form a Weight Matrix and then uses a Weight Spread Sequence (WSS), which is specially designed to distribute the output more evenly, to schedule packets by scanning a Weight Matrix. By using the WSS and the Weight Matrix, SRR emulates the Generalized Processor Sharing (GPS) well. SRR possesses better short-term fairness and scheduling delay properties in comparison with various existing round-robin schedulers. At the same time, SRR preserves O(1) time complexity by avoiding the time-stamp maintenance employed in various fair queueing schedulers. Simulation and implementation experiments show that SRR provides good mean end-to-end delay for soft real-time services. SRR can be implemented in high-speed networks to provide quality of service due to its simplicity and low time complexity.     

A novel scheduler for proportional delay differentiation by considering packet transmission time

The proportional delay differentiation model provides consistent packet delay differentiation between classes of service. The waiting time priority (WTP) scheduler is a priority scheduler in which the priority of a packet increases in proportion to its waiting time, and it is known as the best scheduler to achieve the proportional delay differentiation model. This paper proposes an advanced WTP (AWTP) scheduler, modified from WTP, that takes the packet transmission time into account. Simulation results reveal that when the link utilization is moderate (60%-90%), this scheduler not only obtains more accurate delay proportion than the WTP scheduler, but also reduces the average waiting time.     

Photonic fast packet switching

Several approaches to photonic fast packet switching systems are presented. The wavelength-, time-, code-, and space-division approaches, including free-space photonic fast packet switching, are discussed. These approaches to photonic fast packet switching systems show that the research in this area is still in its infancy. Among various solutions, those based on a wavelength-division transport network and an electronic controller are most mature     

Frequency-hop transmission for satellite packet switching and terrestrial packet radio networks

The performance of frequency-hop transmission in a packet communication network is analyzed. Satellite multiple-access broadcast channels for packet switching and terrestrial packet radio networks are the primary examples of the type of network considered. An analysis of the effects of multiple-access interference in frequency-hop radio networks is presented. New measures of "local" performance are defined and evaluated for networks of this type, and new concepts that are important in the design of these networks are introduced. In particular, error probabilities and local throughput are evaluated for a frequency-hop radio network which incorporates the standard slotted and unslotted ALOHA channel-access protocols, asynchronous frequency hopping, and Reed-Solomon error-control coding. The performance of frequency-hop multiple access with error-control coding is compared with the performance of conventional ALOHA random access using narrow-band radios.     

Nonblocking copy networks for multicast packet switching

In addition to handling point-to-point connections, a broadband packet network should be able to provide multipoint communications that are required by a wide range of applications. The essential component to enhance the connection capability of a packet network is a multicast packet switch, capable of packet replications and switching, which is usually a serial combinations of a copy network and a point-to-point switch. The copy network replicates input packets from various sources simultaneously, after which copies of broadcast packets are routed to their final destination by the switch. A nonblocking, self-routing copy network with constant latency is proposed. Packet replications are accomplished by an encoding process and a decoding process. The encoding process transforms the set of copy numbers, specified in the headers of incoming packets, into a set of monotone address intervals which form new packet headers. The decoding process performs the packet replication according to the Boolean interval splitting algorithm through the broadcast banyan network, the decision making is based on a two-bit header information. This yields minimum complexity in the switch nodes     

Neural networks for switching

The author argues that a strong impetus for using neural networks is that they provide a framework for designing massively parallel machines. He notes that the highly interconnected architecture of switching networks suggests similarities to neural networks. He presents two switching applications in which neural networks can solve the problems efficiently. He shows that a computational advantage can be gained by using nonuniform time delays in the network     

The evolution of packet switching

Over the past decade data communications has been revolutionized by a radically new technology called packet switching. In 1968 virtually all interactive data communication networks were circuit switched, the same as the telephone network. Circuit switching networks preallocate transmission bandwidth for an entire call or session. However, since interactive data traffic occurs in short bursts 90 percent or more of this bandwidth is wasted. Thus, as digital electronics became inexpensive enough, it became dramatically more cost-effective to completely redesign communications networks, introducing the concept of packet switching where the transmission bandwidth is dynamically allocated, permitting many users to share the same transmission line previously required for one user. Packet switching has been so successful, not only in improving the economics of data communications but in enhancing reliability and functional flexibility as well, that in 1978 virtually all new data networks being built throughout the world are based on packet switching. An open question at this time is how long will it take for voice communications to be revolutionized as well by packet switching technology. In order to better understand both the past and future evolution of this fast moving technology, this paper examines in detail the history and trends of packet switching.     

Queueing in high-performance packet switching

The authors study the performance of four different approaches for providing the queuing necessary to smooth fluctuations in packet arrivals to a high-performance packet switch. They are (1) input queuing, where a separate buffer is provided at each input to the switch; (2) input smoothing, where a frame of b packets is stored at each of the input line to the switch and simultaneously launched into a switch fabric of size Nb×Nb; (3) output queuing, where packets are queued in a separate first-in first-out (FIFO) buffer located at each output of the switch; and (4) completely shared buffering, where all queuing is done at the outputs and all buffers are completely shared among all the output lines. Input queues saturate at an offered load that depends on the service policy and the number of inputs N, but is approximately 0.586 with FIFO buffers when N is large. Output queuing and completely shared buffering both achieve the optimal throughput-delay performance for any packet switch. However, compared to output queuing, completely shared buffering requires less buffer memory at the expense of an increase in switch fabric size     

Bypassing omega network for high speed packet switching

A highly regular switching network consisting of several switching stages for output buffering is proposed. Each switching element performs 3×3 switching and has a tail-spared buffer for each input port. According to the performance evaluation of the proposed switching network based on computer simulation, a packet loss ratio of 10^-8 was obtained for a 1024×1024 switching network consisting of 15 stages with the Bernoulli traffic source when the size of tail-spared buffer is 8 and the input traffic load is 0.9     

Network and system concepts for optical packet switching

An overview of the characteristics and challenges of optical packet switching is given, illustrating its potential advantages within future nodes and networks, describing basic system functionalities. The opportunities introduced by the ACTS KEOPS project on all-optical packet-switching networks are highlighted, based partially on the outcome of the RACE ATMOS project, which is also considered in this article     

Models for packet switching of variable-bit-rate video sources

The authors extend earlier work (ibid., vol.36, p.834-44, Jul. 1988) in modeling video sources using interframe coding schemes and in carrying out buffer queueing analysis for the multiplexing of several such sources. The previous models and analysis were suitable for relatively uniform activity scenes. Here, models are considered for scenes with multiple activity levels which lead to sudden changes in the coder output bit rates. Such models apply to talker-listener alternating scenes, as well as to situations where there is a mix of dissimilar services, e.g., television and videotelephony. Correlated Markov models for the corresponding sources are given. A flow-equivalent queueing analysis is used to obtain common buffer queue distributions and probabilities of packet loss. The results demonstrate the efficiency of packet video on a single link, due to the smoothing effect of multiplexing several variable-bit-rate video sources     

Optical signal processing for optical packet switching networks

Optical packet switching promises to bring the flexibility and efficiency of the Internet to transparent optical networking with bit rates extending beyond that currently available with electronic router technologies. New optical signal processing techniques have been demonstrated that enable routing at bit rates from 10 Gb/s to beyond 40 Gb/s. We review these signal processing techniques and how all-optical-wavelength converter technology can be used to implement packet switching functions. Specific approaches that utilize-ultra-fast all-optical nonlinear fiber wavelength converters and monolithically integrated optical wavelength converters are discussed and research results presented.