Circuit-switched Connections Research Articles

A Low-Latency and Low-Power Hybrid Scheme for On-Chip Networks

Network-on-chip (NoC) has emerged as a vital factor that determines the performance and power consumption of many-core systems. This paper proposes a hybrid scheme for NoCs, which aims at obtaining low latency and low power consumption. In the presented hybrid scheme, a novel switching mechanism, called virtual circuit switching, is proposed to intermingle with circuit switching and packet switching. Flits traveling in virtual circuit switching can traverse the router with only one stage. In addition, multiple virtual circuit-switched (VCS) connections are allowed to share a common physical channel. Moreover, a path allocation algorithm is proposed in this paper to determine VCS connections and circuit-switched connections on a mesh-connected NoC, such that both communication latency and power are optimized. A set of synthetic and real traffic workloads are exploited to evaluate the effectiveness of the proposed hybrid scheme. The experimental results show that our proposed hybrid scheme can efficiently reduce the communication latency and power. For instance, for real traffic workloads, an average of 20.3% latency reduction and 33.2% power saving can be obtained when compared with the baseline NoC. Moreover, when compared with the NoC with virtual point-to-point connections (VIP), the proposed hybrid scheme can reduce the latency by 6.8% with the power decreasing by 11.3% averagely.

Minimization of Latency and Power for Network-on-Chip

Network-on-chip (NoC) has emerged as a imperative aspect that determines the performance and power consumption of many-core systems. This paper proposes a combination scheme for NoCs, which aims at gaining low latency and low power consumption. In the presented combination scheme, a peculiar switching mechanism, called virtual circuit switching, is proposed to interweave with circuit switching and packet switching. Flits traveling in virtual circuit switching can pass through the router with only one stage. In addition, multiple virtual circuit-switched (VCS) connections are granted to share a common physical channel. Moreover, a path allocation algorithm is used in this paper to determine VCS connections and circuit-switched connections on a mesh-connected NoC, such that both communication latency and power are optimized.

Keeping the phones ringing

Our phone connections evolve from a simple pair of copper wires into being just one of a number of services on a high-bandwidth next-generation access (NGA) network that may be delivered over traditional copper lines, fibre or even RF links. The shift to NGA marks another chapter in the migration of the phone network away from today's operating metaphor a circuit-switched connection between an individual and caller, connected over lines multiplexed in time and controlled by Signalling System 7. In the new world of NGA, existing handsets plug in to ports on new customer premises equipment (CPE) that mimics the old network's electrical characteristics but carries the call as a series of data packets flowing over a non-deterministic IP network. New handsets create their own IP packets, and use the NGA connection to send them on their way to the rest of the network. As if making all this work wasn't enough, the companies paying to bring NGA networks to our homes naturally want to make a return on their investment as quickly as possible, while the telecoms regulator Ofcom wants to ensure that the market for services remains at least as free as it is at the moment, despite NGA networks bringing a fresh set of technical challenges to open access.

Conversion cascading constraint-aware adaptive routing for WDM optical networks

We examine the negative impact of wavelength conversion cascading on the performance of all-optical routing. When data in a circuit-switched connection are routed all optically from source to destination, each wavelength conversion performed along the lightpath of the connection causes some signal-to-noise deterioration. If the distortion of the signal quality becomes significant enough, the receiver would not be able to recover the original data. There is therefore an upper bound (threshold) on the number of wavelength conversions that a signal can go through when it is switched optically from its source to its destination. This constraint, which we refer to as the conversion cascading constraint, has largely been ignored by previous performance evaluation studies on all-optical routing. We proceed to show that existing static and dynamic routing and wavelength-assignment algorithms largely fail in the presence of the conversion cascading constraints. We then propose two constraint-aware dynamic algorithms: The first, greedy constraint-aware routing algorithm, minimizes the number of wavelength conversions for each connection establishing, and the second, weighted adaptive constraint-aware routing (W-ACAR) algorithm, considers the distribution of free wavelengths, the length of each route, and the conversion cascading constraints, jointly. The results conclusively demonstrate that the proposed algorithms, especially W-ACAR, can achieve much better blocking performance in the environment of full and sparse wavelength conversion.

Performance evaluation of multi-fiber optical packet switches

Multi-fiber WDM networks are becoming the major telecommunication platforms for transmitting exponentially increasing data traffic. While today's networks are mainly providing circuit-switched connections, optical packet-switching technologies have been investigated for years, aiming at achieving more efficient utilizations of network resources. In this paper, we have evaluated, for the first time, the packet-loss performance of multi-fiber optical packet switches (MOPS). Our main contributions are threefold. Firstly, we have proposed simple and accurate analytical models for analyzing packet-loss performance of (i) the most fundamental MOPS configuration, (ii) MOPS equipped with fiber delay lines (FDLs) and (iii) shared wavelength converters (SWCs). Secondly, we have shown that the MOPS network cannot achieve the same performance as the one with full wavelength conversion (FWC), which is quite different from the well-known conclusion in circuit-switched networks. However, MOPS does significantly outperform the classic single-fiber switches. By introducing a small number of FDLs or SWCs, it outperforms the highly expensive FWC solution as well. Finally, we have taken the hardware constraints into consideration by evaluating the performance of MOPS configurations having multiple limited-sized switching boards, which leads to some insights helpful for developing cost-effective MOPS configurations in the future.

The telephone network of the 1960s

In 1960 the transmission technology of the public switched telephone network was ordinary cable pairs, carrier systems on both paired and coaxial cable, and point-to-point microwave radio systems. Voice signals were frequency multiplexed for efficient transmission, but remained in analog form from end to end of a connection. Electromechanical switching systems provided circuit-switched connections, and about half of the customers could directly dial long distance calls. The following decade saw the beginnings of electronic switching and direct distance dialing on a global basis. Meanwhile, applying digital technology to achieve lower costs and better quality for voice transport began in earnest, and the interconnection of data terminals and computer centers became an increasingly important communications need. The initial data communications approach, still used with ever increasing sophistication and speed, was to convert data to speech-like form with data modems. Later, the direct connection of digital data to digital network facilities became the method of choice for building computer communications networks and the backbone of the Internet. It now appears likely that one day all signals, including voice, will be transported by unified high-speed digital networks with a common set of protocols.

Design principles for practical self-routing nonblocking switching networks with O(N·log N) bit-complexity

Principles for designing practical self-routing nonblocking N/spl times/N circuit-switched connection networks with optimal /spl theta/(N/spl middot/log N) hardware at the bit-level of complexity are described. The overall principles behind the architecture can be described as "Expand-Route-Contract". A self-routing nonblocking network with w-bit wide datapaths can be achieved by expanding the datapaths to w+z independent bit-serial connections, routing these connections through self-routing networks with blocking, and by contracting the data at the output and recovering the w-bit wide datapaths. For an appropriate redundancy z, the blocking probability can be made arbitrarily small and the fault tolerance arbitrarily high. By using efficient space domain concentrators, the architecture yields self-routing nonblocking switching networks with an optimal O(N/spl middot/log N) bits of memory or O(N/spl middot/log N/spl middot/log log log N) logic gates. By using a linear-cost time domain concentrator, the architecture yields self-routing nonblocking switching networks with an optimal /spl theta/(N/spl middot/log N) bits of memory or logic gates. These designs meet Shannon's lower bound on memory requirements, established in the 1950s. The number of stages of crossbars can match the theoretical minimum, which has not been achieved by previous self-routing networks. The architecture is feasible with existing electrical or optical technologies. The designs of electrical and optical switch cores with Terabits of bisection bandwidth for Networks-of-Workstations (NOWs) are described.

DATA COMMUNICATION PERFORMANCE TESTING OF AN ADVANCED SATELLITE

The results of a series of data communication tests that measured the digital end-to-end performance of the Advanced Communication Technology Satellite (ACTS) are presented. The experiment intended to determine the performance provided to a pair of users who use the satellite as the transmission medium. In order to accomplish this task, the performance parameters defined in the American National Standard X3.102 were measured. Some examples of the X3.102 parameters include Access Time, Access Denial Probability, Bit Error Probability, User Information Transfer Rate, Disengagement Time, and Disengagement Denial Probability. The performance measured is dependent on the type of service offered (e.g., connection-oriented or connectionless, packet size, window size). The services analyzed included narrowband Integrated Services Digital Network (ISDN), X.25, and a dialed circuit-switched connection. For all services, test results showed that ACTS has a very clean data channel (only one lost byte was recorded during all the tests), the Access Time for most services needs to be shorter, and the parameter estimates did not vary substantially over time or destination location.

METRO

The Multipath Enhanced Transit Router Organization ( METRO ) is a flexible routing architecture for high-performance, tightly-coupled, multiprocessors and routing hubs. A METRO router is a dilated cross-bar routing component supporting half-duplex bidirectional, pipelined, circuit-switched connections. Each METRO router is self-routing and supports dynamic message traffic. The routers works in conjunction with source-responsible network interfaces to achieve reliable end-to-end data transmission in the presence of heavy network congestion and dynamic faults. METRO separates the fundamental architectural characteristics from implementation parameters. Simplicity of routing function coupled with freedom in the implementation parameters allows METRO implementations fully exploit available technology to achieve low-latency and high-bandwidth. We illustrate the effects of this implementation freedom by summarizing the performance which various METRO configurations can extract from some modern CMOS technologies. Included in our illustrations is METROJR-ORBIT , a minimal instance of the METRO architecture we constructed in a 1.2 μ gate-array technology.

Call control and traffic transport for connection-oriented high speed wireless personal communications over metropolitan area networks

A distributed circuit-switched approach for supporting the deployment of high speed wireless personal communication services in urban areas through the interconnection of base stations via metropolitan area networks (MANs) is proposed. Broadband MANs minimize traffic congestion by dynamic sharing of link capacity and by serving as distributed switches for partitioning call control functions. While the DQDB protocol readily supports distributed packet-switching over the IEEE 802.6 MAN, isochronous traffic such as voice and video is best supported by circuit-switched connections. The authors present an enhanced bi-state pre-arbitrated (PA) transport mechanism, and associated call control and handoff management techniques, which enable distributed circuit-switching over the MAN. These capabilities are not currently addressed in the 802.6 standards. The bi-state PA transport mechanism facilitates statistical multiplexing of variable rate isochronous traffic sources. The network capacity is constrained by the call setup delay performance, and is analyzed by simulations. Alternative signaling architectures, involving different placements of call control network elements, are evaluated. The effects of erasure nodes, and close bus versus open bus architectures, are considered. The overlap inter-MAN call setup procedure is proposed to reduce delays. Different call handoff procedures are formulated according to the type of handoff and the resulting change in call connectivity. Most handoffs are intra-MAN, requiring simple procedures with short delays.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Signaling System No. 7 ISDN User Part

The integrated services digital network (ISDN) user part of Signaling System No. 7 defines the signaling protocol which supports the establishment, supervision, and release of voice and nonvoice calls over circuit-switched connections between ISDN terminations of digital subscriber access lines. This paper gives an overview of the ISDN user part protocol, as defined in CCITT Recommendations Q.761-Q.766 [1], in terms of the signaling functions and procedures provided to support call and connection control in an ISDN, and in terms of the information elements and signaling messages that are used by the signaling functions in ISDN exchanges to communicate.