Power, media redundancy

2013-01-04 11:30:08

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Hardware reliability, equipment failure
The task of ensuring Ethernet network uptime for industrial users starts with hardware ruggedness. The environmental conditions faced by Ethernet equipment in the automation control space are often much harsher than the conditions faced in commercial and business settings. Ethernet equipment installed in outdoor cabinets or on the factory floor may have to contend with elevated levels of vibration, electromagnetic interference, heat, and airborne particulates. If the equipment is not properly hardened or protected, the Ethernet network may suffer from frequent equipment failures and unreliable data transmission. Figure 2: Cooling fans are vulnerable to airborne particulate matter and may be susceptible to failure, increasing maintenance costs and effort. Courtesy: Moxa Americas Inc.Forced-air cooling is a method that manufacturers commonly use to prevent equipment from overheating. Fans drive air circulation within the networking equipment to draw in cooler air and drive out hot air (see Figure 2). This is an adequate measure when the equipment is kept within a clean and temperature-controlled room, such as in the IT closets found in commercial facilities. However, the commercial-grade approach tends to be inadequate for many automation control applications, where an environmentally controlled room is simply not available or feasible. The prevalence of environmental particulates at many industrial sites can negatively affect forced-air cooling efforts as particulate matter accumulates in the air filters or within the device itself. In addition, the fans themselves are more prone to failure than other components, so regular maintenance and downtime must be factored into the cost and planning of the network. For this reason, fanless operation has become a compelling feature to ensure high hardware reliability in industrial Ethernet equipment. Since there are no moving parts, passively cooled hardware can achieve much higher mean time between failures and stands up well to industrial use. The amount of engineering required to develop a reliable fanless Ethernet switch means that the initial purchase cost will be significantly higher than for commercial-grade fan-cooled switches. However, over the lifetime of the device, fanless switches often show a superior return on investment when factoring in reduced maintenance, network downtime, and equipment replacement costs. 
Power, media redundancy
Power and media redundancy can help minimize the occurrence and impact of network downtime. Industrial networks are often deployed in the vicinity of rotating machinery such as inductive motors or generators, welders, or other high-power machinery. This exposes the Ethernet equipment to fluctuations in power quality that aren’t typically seen in commercial applications. For this and other reasons, basic control-system redundancy requires every part of the communication network to have a redundant backup power supply in case of a power interruption or outage. The backup power supply takes over when the electricity fails, minimizing the possibility of damage or loss of critical data caused by the system shutting down. To meet the needs of automation and control systems, the hardware should be compatible with unregulated dc and have reverse power protection and isolation of the redundant power inputs. Media redundancy is also a common requirement for automation networks and involves establishing a backup communication path when part of the network becomes unavailable. Because redundant paths on Ethernet networks create network loops, a method or protocol must be used to block this redundant path during normal operation. IEEE 802.1D Spanning Tree Protocol (STP) was developed in the IT space for networks to deal with redundant paths. With IEEE 802.1D, one switch on the network is designated the “root switch” of the network, and automatically blocks packets from traveling through any of the network’s redundant paths. In the event that one of the paths in the network is disconnected from the rest of the network, STP automatically readjusts the network to use the redundant path. The major limitation of IEEE 802.1D STP is the high performance cost associated with each network convergence, which refers to the process by which participating switches agree on the root bridge and the ports/network paths to block. When a network segment fails, the STP network will re-converge, which suspends all network traffic except for the control messages used in the convergence operation itself. This suspension of service can last up to 50 sec, which could result in substantial and unacceptable losses in the world of industrial automation. IEEE 802.1W Rapid Spanning Tree Protocol (RSTP) was introduced to overcome the limitations of IEEE 802.1D and boasts greatly improved performance, substantially reduced convergence time (under 5 sec), and correct behavior for mis-ordering and duplication in RSTP bridges. The improvement in convergence time is achieved by reducing the number of port states from five to three and by allowing ports to be specified as “edge” devices that can power up or down without requiring the network to reconverge (because they are not passing frames to another switch). These enhancements make it possible to achieve media redundancy with higher performance, although some of the advantages are lost when RSTP is interoperating with STP. Although RSTP is a substantial improvement over STP, many control applications require even better network recovery times. A number of Ethernet device manufactures have developed proprietary redundancy protocols based on 802.1W and have been able to achieve near-instant network recovery times. Proprietary protocols are available that enable a 250-switch network to recover from a failed network segment within 20 msec. It is important to note that network recovery time can be susceptible to the network load and number of switches that are connected, so real-world testing and verification is an additional and important step to ensure the desired network performance.
CrossNetworks Deploys Centec's Carrier Ethernet Solution in the Netherlands
SUZHOU, China, Dec. 19, 2012 /PRNewswire/ -- Centec Networks, a leading innovator of IP/Ethernet switching silicon and advanced turnkey system solutions, and CrossNetworks, an independent infrastructure provider, announced that CrossNetworks has successfully deployed Centec's Carrier Ethernet solutions for its nationwide backbone network in the Netherlands. Centec has provided system solutions based on its own switching silicon to CrossNetworks since 2009, helping CrossNetworks to deliver stable and efficient networking services to its customers for years.CrossNetworks built the network with Centec's high performance E300/E310 and E330 series Carrier Ethernet routing switch solutions. The network serves as an open nationwide fiber optic backbone. It serves small and large enterprise customers as well as various service providers. Among its customers are hospitals, local government institutes like mental health care organizations and schools. The network provides reliable and scalable services via superb protection scheme and service SLA.E300/E310/E330 solutions are built on Centec's powerful TransWarpTM switching silicon which includes a series of chips: CTC6048, CTC6028, CTC5048, with industry leading features and performances. The chips can be widely used in access/aggregation IP/Ethernet routing switches, Packet Transport Network (PTN) platforms, Optical Line Termination (OLT) systems and Wireless Backhaul Gateways. Centec's 3rd generation switching chip CTC5160 will be available soon with an even higher integration and performance and a dramatically reduced footprint, power and cost."CrossNetworks is glad to have chosen Centec as the solution provider for the advanced carrier Ethernet features, such as Flexible QinQ, ring protection, MPLS VPN, and its outstanding customer support. The cooperation started years ago when we used its early solution based on the first generation chip and now we're glad to upgrade to the latest one. The devices are quite a fit and are running stably," said Robert Roomer, founder and director of CrossNetworks."CrossNetworks is one of Centec's strategic partners for Centec's Carrier Ethernet solutions," said Tao Gu, VP of business development of Centec Networks. "The robustness of our system solutions and chipsets on which the system is built on is again being verified by successful service deployment and long-time stable network operations. Centec already has design wins in the US, Europe, South America, East Asia, and China, and we will continue to expand our business worldwide with the cutting-edge silicon and system solutions with superb services."
The above information is edited by 10GTEK.
10GTEK TRANSCEIVERS CO., LTD (Hereinafter refered to as 10GTEK) is specialized in developing and manufacturing Fiber Optical Transceivers and High Performance Cables which are wildly applied in Datacom, Telecom and CATV, providing customers with top quality and cost effective products. Our High Speed Cables cover Passive SFP+ Cable, Active SFP+ Cable, QSFP+ cables, MiniSAS (SFF-8088) Cables, CX4 Cables, Harness cables, Breakout Cables, Patchcords. We also manufacture Fiber Optic Transceivers like 10G XFP, 10G SFP+, SFP DWDM/ CWDM, GBIC, etc. The prompt response and excellent customer support contribute to clients‘ full satisfaction.Today, 10GTEK has been growing fast in the optical field for its unique and competitve excellence which has got a high attention from datacom and telecom.
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