Saturday, November 25, 2006

Cylindrical laser machining gets motion platform

Direct-drive, brushless linear and rotary motion platform that includes automated workpiece handing and tooling platforms is intended for cylindrical laser machining applications.

Aerotech's LaserTurn combines high performance, direct-drive brushless linear and rotary positioning stages with automated workpiece handling and provision for customised tooling - for a completely integrated motion solution for high-throughput cylindrical laser machining applications. The new LaserTurn series is the result of Aerotech's dedicated research and extensive experience to provide improved productivity, industry-specific motion sub-systems, for high-throughput manufacture and test applications. The LaserTurn series features direct-drive brushless linear and rotary stages with non contact encoders for high speed, zero backlash performance with micron level precision and repeatability.

The integrated linear and rotary design allows a low machine centre of gravity that reduces the potential for dynamic pitch error under rapid acceleration and reversal conditions - offering a vast performance improvement over separate linear and rotary stages.

Other benefits include superior productivity, higher rigidity, smoother motion with faster settling times, and consistently improved high quality of the laser machined part.

Available in two sizes for workpiece diameters up to 30 mm with a choice of 200mm or 300mm linear travel, the smaller LaserTurn 2 has an ER16 collet supporting tube and bars from 0.5mm to 10mm diameter.

The LaserTurn 5 has a larger width footprint and is available with options of an ER25 or ER40 collet for 0.5 to 16mm and 16mm to 30mm workpiece diameters respectively.

In addition the larger model may be fitted with a three-jaw gripper.

All workpiece handling may be pneumatically automated and includes a clear aperture for product feed through.

The linear stage includes a hard top design with side seals for full protection and the complete assembly is fully protected against laser machining debris.

As well as motor power and encoder wiring, pneumatics and customer specific cabling is routed through an e-chain cable management system with interfacing connectors provided.

This greatly simplifies machine design and commissioning time and ensures high reliability and a long maintenance-free life.

For custom fixtures such as workpiece alignment supports and automated material advance, the LaserTurn's front facing end-plate provides a tooling platform with a matrix of M6 holes on a 25mm square pattern.

As this tooling interface is an integral part of the linear stage, a common reference is guaranteed for maximum system stiffness.

An optional rear tooling platform may also be specified and customised mounting patterns or additional fixtures may be provided upon request.

With a choice of linear encoders, overall accuracy of +/-5 micron is achievable, alternatively a 'Halar' calibrated option provides for +/-1 micron accuracy over the full travel range.

Positional repeatability is within +/-0.5 micron and straightness and flatness is within a total deviation of +/-1 micron.

Maximum linear speeds are up to 2m/s.

For both models, rotary stage accuracy is +/-15 arc-sec with repeatability at +/-3 arc-sec for the smaller LaserTurn 2 and +/-6 arc-sec for the LaserTurn 5.

Axial and radial runout and wobble specifications correspond with the overall high precision of these assemblies and rated speeds for the smaller and larger models are 2000 rev/min and 600 rev/min respectively.

Complementing the performance capability of LaserTurn laser machining systems, Aerotech's A3200 Digital Automation Platform is a powerful PC based, software-only, machine control system combining a high-performance, 1 to 32 axis motion engine with decentralised digital servo drives interfaced via a high-speed Firewire network.

The A3200 has integrated machine control function modules such as HMI, Vision, soft PLC and a 10/100 Base-T Ethernet interface for third party I/O and PLCs.

It includes a wide range of advanced motion and machine control commands aimed at increasing and improving the finished quality and throughput performance for demanding applications.

An example is the acclaimed Position Synchronised Output or PSO command that maintains precise, 'on-the-fly' synchronisation of the laser's pulse, power level and firing pattern with the exact position of the multi-axis positioning system typically moving the work piece undergoing laser feature generation.

Aerotech are able to meet and often exceed a customers' performance requirements by providing engineered systems with fully tested and calibrated mechanical stages and associated control and drive equipment.

This reduces the overall cost of ownership when compared to individual design, purchase and assembly of motion control components.

Typical systems include all motor power and encoder cables plus performance and calibration related documents to help integrators with their own system documentation.

All motor parameter set-up data for system configuration is included, making commissioning straightforward.

These features are standard for every Aerotech product and with full product training and comprehensive on-line technical support, the true cost of ownership is extremely competitive.

Laser engraves deeply from 3D CAD models

Laser engraver performs deep engraving direct from 3D CAD models on workpieces up to 500mm3, including cutting complete tool cavities, adding fine detail, textures, logos or producing electrodes.

To accommodate the first ever UK exhibition for the FOBA Laser Engraving machine Kaye-Dee have had to move to the larger C52 stand Hall 3 at the forthcoming PDM show. Centrepiece will be the G5 Laser Engraver demonstrating its capability of deep engraving direct from 3D CAD models. You can engrave work pieces up to 500mm3 and applications include cutting complete tool cavities, adding fine detail, textures, logos or producing electrodes in copper or graphite.

Kaye-Dee invites you to come and see how you can totally transform your mould and tool manufacture with this equipment.

In addition to the G5 there will also be a second FOBA laser showing you its expertise of marking a wide range of materials using fibre laser technology.

As the market leaders in the pad printing industry we will also be displaying the exceptional Teca-Print pad printing machines.

On show will be the TP printer series designed with the operator in mind, equipped with sealed ink pot system and extended pad stroke to allow mouldings to be printed in either a fixed jig position or whilst being indexed on a production line.

Also on show will be the TPX 100 Open Ink Well System with Touch Screen control panel, easy learn logic and an extremely user friendly programming menu.

Next to this state of the art machine will be a working 30 year old TC70 unit highlighting the quality and value for money you get from this precision Swiss manufactured equipment.

To ensure you get the best print on your product we can also advise on pad and screen printing inks from the extensive Ruco ink range.

This includes the new T40 ink with excellent opacity and no harmful cyclohexanone or hydrocarbonates.

Another addition to our collection of marking equipment and on show is the new range of Hot Foil machines.

With an extensive model range manufactured to the height of British excellence, automation and a wide range of accessories, foils and dies Kaye-Dee can accommodate your every hot foil requirement.

We look forward to you visiting our stand so we can help make your marking requirements simple, reliable, cost effective and most importantly allow you to achieve the ultimate marking perfection! Written invitations will follow for your personal attention shortly.

Friday, November 24, 2006

Laser power source used in medical manufacture

A 400W laser power source for a major OEM manufacturer of medical equipment and features a 60A constant current source and can drive up to 35W CW laser diodes.

UK Power supply specialist, Ferrus Power, has demonstrated its extensive design capability by developing a new 400W laser power source for a major OEM manufacturer of medical equipment. Featuring a 60A constant current source and nominal voltage of 2V DC the product can drive up to 35W CW laser diodes. In addition a TEC output rated at 250W/25V DC is provided with reversible polarity for driving external peltier devices for diode cooling or heating.

Laser and TEC current is controlled via 0-10V DC external programming in each case.

Current monitoring for both laser and TEC is provided in 0-10V DC format with voltage monitoring proportional to output.

For safety purposes a further laser interlock control offers beam attenuation and shuts down the laser output to meet the requirements of 21 CFR 1040.10.

Signal and control connections are via 16W IDC whilst laser and TEC are via high current screw terminal block.

The need for an external power supply to drive ancillary microprocessor control circuitry is removed as the product also features low voltage outputs of +5V DC,+/-15V DC and 24V DC via six-way 0.156in header.

The product is suitable for worldwide applications and offers universal mains input operation of 90 - 264V AC with active power factor correction to meet the line harmonic distortion requirements of EN61000-3-2 class D.

The product is currently undergoing medical approvals testing to EN60601-1.

Ferrus has the capability to design and manufacture similar products to suit the laser and opto-electronics industry and would welcome enquiries.

Flexible 3D laser cutting/welding robot launched

A flexible, modular robot system for 3D laser processing offers high productivity and availability thanks to short programming times and guarantees a uniformly high workpiece quality.

For the first time Trumpf presented itself at euroblech as the manufacturer of a robot welding cell, the TruLaser Robot 5020. From the laser beam source to the safety enclosure, from the peripherals to the integration expertise - all the required know-how has been brought together in one spot. Only the standard robot continues to be an outside product.

It comes from KUKA.

The complete solution TruLaser Robot 5020 from Trumpf is a flexible robot solution for 3D processing.

The TruLaser Robot 5020 distinguishes itself with high productivity and availability thanks to short programming times.

In addition, the robot solution guarantees a uniformly high quality in the workpieces.

Its modular, standardized design allows the TruLaser Robot 5020 to be individually expanded or delivered ready for operation according to the user's requirements.

At EuroBLECH, Trumpf offered several innovations for the TruLaser Robot 5020.

Functionalities such as electrical cabinet, cable channels, suction lines, lighting and safety devices are integrated into the new, cost-optimized safety enclosure.

It is easy to connect several enclosures.

More sophisticated welding optics with minimized interference contour or a new collision protection using a magnetic coupler embody the innovations specifically, like the optimized shielding gas supply.

An observation camera with crosshairs is also available for moving in the workpieces.

The automatic adjustment of the focussing orientation is a special feature: It is now possible for the first time to switch between deep welding and thermal conduction welding in a single processing cycle.

Thursday, November 23, 2006

Imaging-based instrumentation in management buyout

Oxford Lasers, a provider of laser-based solutions for micromachining and imaging-based instrumentation, has been wholly acquired by its management team.

Oxford Lasers, a provider of laser-based solutions for micromachining and imaging-based instrumentation, has been wholly acquired by its management team. This follows a very successful period when sales have grown by over 60% in 12 months and the company has completely updated its product line. New products include the advanced PicoLase micromachining system recently installed at the Manufacturing Engineering Centre, Cardiff, UK and the industry proven ProbeDrill series.

Previously the company was majority owned by private equity backers but following the new deal, the management team now owns 100% of the equity.

John Baker, Chief Executive of Oxford Lasers said, 'We are absolutely delighted.

The company has an outstanding range of new products and services and we are ideally positioned to supply a complete range of laser solutions to our customers.

We have had one of the most successful periods in the company's history and have clear plans to continue this strong growth.' Oxford Lasers was founded in 1977 by a team of Oxford physicists in order to exploit the significant advances in laser technology made by Professor Colin Webb's research group at the university.

In recent years the company has become a world leader in using advanced laser techniques in commercial applications.

Its goal is to supply complete technical solutions to its customers in the areas of precision laser micromachining and high speed imaging of small particles.

Oxford Lasers is based in Didcot UK and Boston, USA.

It has a wide distribution network in other countries, notably Japan.

The company designs and manufactures imaging systems using a light source, usually a laser, a camera and software to give a complete package for making quantitative measurements of small particle or droplets.

The company has introduced a revolutionary solid-state laser illuminator for flow and motion analysis which, together with specially designed software packages, enables large amounts of data to be obtained and analysed quickly and efficiently.

Oxford Lasers Imaging systems produce size, velocity and acceleration data for powders and sprays of micron sized particles moving at high speed.

They also provide information on plume geometry and spray pattern.

The company offers a comprehensive range of standard qualitative and quantitative imaging systems for research and industry.

The range of systems includes: VisiSizer - which uses image analysis to measure particle and droplet size; VisiVector - a PIV (particle image velocimetry) system with 3D capability; VisiWeld - for the analysis of welding processes and Envision for characterizing spray pattern and geometry.

THE INDUSTRIAL DIVISION: Oxford Lasers has three main sectors within this Division.

Laser Systems - the company offers a comprehensive range of standard micomachining systems covering; industrial development and pilot production; continuous volume production; and advanced RandD in commercial or academic environments.

All of these are based on the company's expertise in light sources, optics, ablation processes and system integration.

As an example of an advanced RandD system, the latest PicoLase system features 532nm and 355nm output, high power picosecond pulses and 12 axis motion control.

In addition the company designs bespoke systems where there is a particular customer requirement.

Sub Contract Micro Machining.

- the company offers a micromachining service to support customers RandD and production programmes, The company's expertise can frequently dramatically accelerate these projects and allow laser micromachining to be used where volumes do not justify the capital cost of a laser system.

Field Service - with its extensive range of laser system skills the company offers a range support services to customers on their own site including, maintenance plans, training and system upgrades.

Nesting takes off developments in software and CNC machining centers lead more woodworkers to implement nested-based manufacturing in their shops

Nested-based manufacturing on CNC machining centers is catching on in the furniture and cabinet manufacturing sectors, in large part because of more user-friendly software.

Sales of CNC (computer numerically controlled) routing machines for nesting parts are increasing, particularly to smaller and medium-size companies, according to representatives of CNC router companies interviewed by Wood & Wood Products.

"We're selling three times as many nested-based applications as point-to-point machines," says Michael Cassel, CNC product manager at Holz-Her U.S. "Nested-based manufacturing is the most active part of the CNC market fight now. The difference is the software."

Wednesday, November 22, 2006

CNC router shoots production through the roof: Use of a four-axis CNC router dramatically increases gun stock production at California shop.

Ironwood Designs, a San Jose, CA-based designer and manufacturer of wooden gun stocks, has more than tripled since replacing a manual pantograph with a four-axis CNC router.

Made of high-quality hardwoods, Ironwood Designs' products are purchased by individual gun owners, gun dealers and firearms manufacturers to replace the inexpensive plastic or softwood stocks of many imported military guns such as the FN-FAL and the AK-47. Ironwood Designs also sells a four-piece wooden set that includes the butt stock, pistol grip and an upper and lower hand guard.

Membrane-pressed MDF panels fill the bill; converting from metal powder finishes to thermoplastics re-defines the appearance, durability and repairabi

In the high traffic environment of wireless retail stores, automated bill payment kiosks fabricated of powder-coated sheet metal incurred scratches, dents, scuffs and stares from pens, markers and spilled drinks.

"As a result, wireless companies were incurring high costs to replace damaged kiosks or repair them in the field," says Tom Zaken, director of national program development at Creative Kiosk, Norcross, GA.

One of Creative Kiosk's wireless customers is Sprint. The company accepts tens of thousands of payments each month through the kiosks, providing convenience for customers and sales personnel alike.

Tuesday, November 21, 2006

Tool/Cutter Grinder Keeps Tools Coming

Intended for tools up to 1/2'' (12.7-mm) diam shank and lengths to 6'' (152 mm), including burrs and router bits, the dual-spindle MGX (made by ANCA Inc., Farmington Hills, MI), is a precision tool grinder featuring an integrated robotic loader and tool change times of less than 5 sec. Pallet loading with as many as 280 tools/pallet permits untended operation.

The MGX has nine axes-five traditional rotary and linear axes and four patented soft axes. By exploiting the CNC's capabilities, the four soft axes allow ANCA to offer a nine-axis machine with the relatively simple mechanical design of a five-axis machine.

The offset dual-spindle design can provide as many as six grinding wheels in a single cycle with minimum interference or repositioning. Spindles can be set up with high-speed and low-speed wheel packs. Each spindle can deliver a maximum of 11 hp (8.2 kW) at speeds to 10,000 rpm. An optional 20,000-rpm spindle is available for polishing or grinding with small wheels.

This system's patented precision collet assembly and precision adjustable popup steady means runout as low as 0.000008-0.000016'' (2-4 pm) in a production environment is typical. Using this assembly permits setup in as little as ten minutes.

The MGX can be programmed to produce any combination of tools from a single pallet of blanks. Because it's a Windows NT-based system, the control system enables operators to use the ANCA ToolRoom software. ToolRoom permits users to develop new parts by entering the new tool's parameters into the CNC, avoiding trial-and-error machining of new tools.

Machining REFRACTORY METALS

Refractory metals such as Wah Chang's (Albany, OR) C-103 (Niobium + Hafnium + Titanium) provide design engineers with a suite of unique and wonderful properties. These alloys have high strength in continuous operation to 270O°F (148O°C) or higher, making them attractive for a variety of rocket-propulsion components and industrial-process assemblies. They are relatively impervious to exposure to high-temperature propellant gases (also important in propulsion applications). They have low ductile-to-brittle transition temperatures for withstanding high-frequency vibration; can be made into forgings, plates, sheets, and tubes; and are readily welded into complex assemblies.

These materials present special challenges to machinists, however. They impose new constraints on cutting tool design, coolants, and speeds and feeds, compared to more conventional materials. If you are searching for a manufacturer of critical refractory-metal components or assemblies, evaluating a candidate supplier's capability to perform such work, or planning for an in-house fabrication activity using refractory metals, there are several critical areas to evaluate.

These fall in the general areas of development of machining processes, tool definition, and process-control discipline. Our comments on these subjects are based on more than 20 years of experience in the design, process development, and manufacture of rocket propulsion components (hot gas control valves) made from C-103 and other refractory alloys that must meet the most exacting quality and reliability requirements. Typical machining operations on C-103 bar stock and forgings in our plant consist of turning, drilling, boring, milling, and threading fairly thick-walled body sections. Because machined parts will later be welded into higher-level assemblies, we require close-tolerance weld interfaces and fine surface finishes with no voids, tears, or inclusions. Typical tolerances for diametral features are ±0.001'' (0.03 mm), with positional tolerances running as close as 0.002'' (0.05 mm). Surface-finish callouts of 16 RMS are typical, as are closely controlled filet radii of 0.005'' (0.13 mm).

Development of machining processes is not straightforward. The unique properties of refractory metals present special challenges to the machine shop that require the development of special machining methods, tools, and coolants.

For example, C-103 is a highly ductile, soft, and stringy material. (One of our machinists has likened cutting it to "trying to machine an old shingle.") It has a high abrasive-wear characteristic that breaks down tool edges, and creates high heat buildup. This alloy is prone to tearing, galling, and chip welding to the tool face. Because of the high cutting forces and the tough, stringy chips produced when machining C-103, chipbreakers are completely ineffective.

During our development of turning processes, standard HSS tool profiles with zero or negative top rakes produced ragged, torn, poorly sized diameters that were unacceptable. Tool wear was tremendous as well, with extensive cratering of the cutting edge, and in some cases tools were broken off at the shank. Tungsten carbide inserts with similar profiles also produced bad results.

Tools with high positive top rake angles of 5, 10, 15, and 20° were tried until a favorable result was established. Turning tools of HSS and carbide with a positive top rake of 15-20° are able to machine C-103, providing that proper feeds, depthsof-cut, and speeds are used. Due to the abrasive nature of C-103, cutting speeds must be reduced to approximately 250 fpm (76 m/min) for carbide and 75 fpm (23 m/min) for HSS and cobalt-alloy tools. Typical feed rates for turning C-103 are approximately 0.005 ipr (0.131 mm/rev). Due to the unavailability of off-the-shelf carbide inserts with the required high positive top rakes, special toolholders and modified inserts are used throughout the shop.

One of the most important things that we learned about the machining of C-103 relates to the size of cuts that can be taken to produce the desired size and finish. In that it tears and does not abrade, C-103 is similar to copper; therefore, it's very difficult to form a chip less than 0.001'' (0.03-mm) thick. Rough and finish cuts must be adjusted to the proper ratio in order to produce a satisfactory size and finish.

Boring of C-103 poses some interesting problems. Standard boring bars of both HSS and carbide have geometries that will not allow regrinds of 15-20° of positive top rake without severely weakening the tool. The unsupported lengths of these boring bars create excessive deflection and chatter. Many different shapes were tried without success. One machinist suggested that we try a two-flute end mill, with one flute ground away for clearance. The results were miraculous. We got excellent chip control, with a beautiful surface finish, and we were able to hold size. Today we use both HSS and carbide single-flute router bits for almost all of our boring requirements.

Monday, November 20, 2006

Technology & training help furniture company soar

At Bird-in-Hand Woodworks Inc., education equals success--in more ways than one.

A manufacturer of solid wood and melamine early education furniture, the Lancaster, PA based company is equally renown for its longtime advocacy of employee education.

The need to enhance worker skills through comprehensive training programs has become vitally important in recent years. As Bird-in-Hand has invested more heavily into new technology--$3 million in the past few years--the stakes have been raised to have qualified personnel to run and maintain the machines.

Clear Impact Acrylics Installs MultiCam CNC Router

Clear Impact Acrylics, Kansas City, Missouri, has recently installed a new MultiCam CNC router.

The plastics fabrication firm specializes in designing and producing retail and corporate displays.

The new router features: a 4'x 8' table; dual cutting heads; 3axis operation and a dust collection system.

"The growth of our business brought about the need for the CNC router," stated Clear Impact Acrylics' Xang (pronounced "Zang") Xiong. "The efficiency and quality of the MultiCam combined with the excellent service from KOMT has been great. We are running 24 hours a day with it. In fact, we already have ordered a second MultiCam router."

Clear Impact Acrylics works with most plastics including: ABS, acrylic, foam PVC, mirrored, PETG, polycarbonate and styrene.

Sunday, November 19, 2006

Orange County and Microsoft Technology Voucher Program

What is Available

Vouchers will be issued in two categories: 1) General Purpose Vouchers and 2) Software Vouchers. General Purpose Vouchers may be used to purchase specific hardware (listed below), any non-custom software for that hardware, evaluation tools, information technology (IT) services, and professional development services. IT and professional development services must be obtained from approved providers in Orange County schools. Software Vouchers may only be utilized to purchase specific categories of software (listed below) that are published or sold by any software provider. Both the General Purpose and Software

Vouchers may be applied by Orange County schools in an amount no greater than the standard academic price, or if an academic price is not available, in an amount not to exceed the normal or standard price established by the manufacturer or vendor for such software. The following list gives examples of eligible goods and services that may be purchased with one or the other category of the vouchers:

Hardware available for Orange County schools: Any new laptop, desktop, or tablet computer for any operating system platform; Peripheral devices: printers, scanners, monitors, keyboards, pointing devices (e.g., mouse, trackball, etc.); Equipment needed for networking and infrastructure (e.g., routers, servers, wireless network cards, or wireless access points); Hardware for accessing the Internet through television sets and Internet access for such hardware for students' homes; Non-custom assistive technology devices for use by students with special needs

Software available for Orange County schools: Purchased with General Purpose Vouchers - Any non-custom software titles (any platform) that are designed for use on any qualifying hardware (see Hardware above); purchased with Software Vouchers - Specific categories of software offered by any software publisher or vendor, including: Operating system, Word processing, Spreadsheet, Presentation, Desktop relational database oriented towards single users and typically residing on a standard personal computer, Web-authoring, Productivity and/or Productivity Suite, Encyclopedia, Server, including client access licenses, Eligible software bundled with a computer purchased with the General Purpose Vouchers

IT Support Services available for Orange County schools: Services that primarily involve the maintenance of hardware procured through this Settlement and the installation and maintenance of software procured through this Settlement.

Professional Development Services available for Orange County schools: Professional development services directed solely at leadership development for school administrators in the use of education technology to improve learning at the site or district; Professional development services directed solely at general curriculum development and instructional strategies which utilize educational technology to improve instruction; Professional development services directed solely at the improvement of technology integration for any software title acquired through this Settlement; Training in the use of any hardware or software title acquired through this Settlement; Certification training for software and networking

The cold hard truth about TCP/IP performance over the WAN

TCP is a transport technology that is commonly used for the electronic movement of data between servers and other devices. Many storage vendors are beginning to use the TCP transport for replicating data between storage devices. However they are finding out that TCP as a transport has some basic limitations that cause many applications to perform poorly, especially over distance. TCP/IP performs sufficiently over short-distance LAN environments; however it was not well designed for transmission over Wide Area Networks (WANs). This article explores the challenges of TCP performance over the WAN and ways to mitigate these performance challenges with new data center appliances.

TCP Challenges

Window Size Limitations

Window size is the amount of data that is allowed to be outstanding (in the air) at any given point-in-time by the transport software. The available window size on a given bandwidth pipe is the rate of the bandwidth times the round-trip delay or latency. Using a cross-country OC-3 link (approximately 60ms based on a total 6000-mile roundtrip) creates an available data window of 155 Mbps X 60ms = 1,163 Kbytes. A DS3 satellite connection (540ms roundtrip) creates an available data window of 45 Mbps X 540ms = 3,038 Kbytes.

When this is contrasted with standard and even enhanced versions of TCP, there is a very large gap between the available window and the window utilized. Most standard TCP implementations are limited to 65-Kbyte windows. There are a few enhanced TCP versions capable of using up to 512 Kbytes or larger windows. Either case means an incredibly large amount of "dead air" and very inefficient bandwidth utilization resulting in poor performance for applications that are typically mission-critical.

Slow Start by Design

TCP data transfers start slowly and ramp-up to their maximum transfer rate, resulting in poor performance for short sessions. Slow start is used to avoid congestion due to assumptions that large numbers of sessions will be competing for the bandwidth.

[GRAPHIC OMITTED]

Inefficient Error Recovery

During error recovery, TCP causes the entire stream from any lost portion to be retransmitted in its entirety. High-bit-error rates or packet-loss scenarios will cause large amounts of bandwidth to be wasted in resending data that has already been successfully received, all with the long latency time of the path. Each retransmission is additionally subjected to the performance penalty issues of slow start, which was explained above.

Packet Loss is Disruptive

Packet loss describes an error condition in which data packets appear to be transmitted correctly at one end of a connection, but never arrive at the other end. This is mainly due to:

* Poor network conditions causing damage to packets in transit.

* The packet was deliberately dropped by a router and/or switch because of WAN congestion.

Packet loss can be disruptive to applications that must move data within windows of time. With more data that must be moved on a regular basis and the fact that backup windows are not growing to meet the data demands, packet loss can have a negative impact on meeting service-level agreements and production for many organizations.

The Figure shows a standard TCP stream of data running over an OC-12 (622Mbs).

Session Free-For-All is Not Free

Each TCP session is throttled and contends for network resources independently, which can cause over-subscription of resources relative to each individual session.

The net result of these issues is very poor bandwidth utilization. The typical bandwidth utilization for large data transfers over long-haul networks is usually less than 30%, and more often less than 10%. As fast as bandwidth costs are dropping, they are still not free.

How to Mitigate TCP/IP Performance Issues

Consider Using an IP Application Accelerator (Appliance)

Many new data center appliances are being used to optimize data delivery for IP applications. Some appliances mitigate performance issues by simply caching the data and/or compressing the data prior to transfer. Others have the ability to mitigate several TCP issues because of the superior architecture.

Whatever technology is used, it is important the appliances have the ability to mitigate latency issues, compress the data and shield the application from network disruptions. It is also important that these new data center appliances are transparent to operations and provide the same transparency to the IP application.

Transport Protocol Conversion

Some data center appliances provide alternative transport delivery mechanisms between appliances. In doing so, they re-ceive the optimized buffers from the local application and deliver them to the destination appliance for subsequent delivery to the remote application process. Alternative transport technologies are responsible for maintaining acknowledgements of data buffers and resending buffers when required. It is important to maintain a flow control mechanism on each connection, in order to optimize the performance of each connection to match the available bandwidth and network capacity.