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  • Closing the gap between strategy and execution with Oracle Business Intelligence 11g

    - by manan.goel(at)oracle.com
    Wikipedia defines strategy as a plan of action designed to achieve a particular goal. An example of this is General Electric's acquisitions and divestiture strategy (plan) designed to propel GE to number 1 or 2 place (goal) in every business segment that it operated in. Execution on the other hand can be defined as the actions taken to getting things done. In GE's case execution will be steps followed for mergers/acquisitions or divestiture. Business press has written extensively about the importance of both strategy and execution in achieving desired business objectives. Perhaps the quote from Thomas Edison says it best - "vision without execution is hallucination". Conversely, it can be said that "execution without vision" is well may be "wishful thinking". Research overwhelmingly point towards the wide gap between strategy and execution. According to a published study, 49% of surveyed executives perceive a gap between their organizations' ability to develop and communicate sound strategies and their ability to implement those strategies. Further, of these respondents, 64% don't have full confidence that their companies will be able to close the gap. Having established the severity and importance of the problem let's talk about the reasons for the strategy-execution gap. The common reasons include: -        Lack of clearly defined goals -        Lack of consistent measure of success -        Lack of ownership -        Lack of alignment -        Lack of communication -        Lack of proper execution -        Lack of monitoring       There are multiple approaches to solving the problem including organizational development practices, technology enablement etc. In most cases a combination of approaches is required to achieve the desired result. For the purposes of this discussion, I'll focus on technology.  Imagine an integrated closed loop technology platform that automates the entire management cycle from defining strategy to assigning ownership to communicating goals to achieving alignment to collaboration to taking actions to monitoring progress and achieving mid course corrections. Besides, for best ROI and lowest TCO such a system should also have characteristics like:  Complete -        Full functionality -        Rich end user access Open -        Any data source -        Any business application -        Any technology stack  Integrated -        Common metadata -        Common security -        Common system management From a capabilities perspective the system should provide the following capabilities: Define -        Strategy -        Objectives -        Ownership -        KPI's Communicate -        Pervasive -        Collaborative -        Role based -        Secure Execute -        Integrated -        Intuitive -        Secure -        Ubiquitous Monitor -        Multiple styles and formats -        Exception based -        Push & Pull Having talked about the business problem and outlined the blueprint for a technology solution, let's talk about how Oracle Business Intelligence 11g can help. Oracle Business Intelligence is a comprehensive business intelligence solution for reporting, ad hoc query and analysis, OLAP, dashboards and scorecards. Oracle's best in class BI platform is based on an architecturally integrated technology foundation that provides a unified end user experience and features a Common Enterprise Information Model, with common security, query request generation and optimization, and system management. The BI platform is ·         Complete - meaning it delivers all modes and styles of BI including reporting, ad hoc query and analysis, OLAP, dashboards and scorecards with a rich end user experience that includes visualization, collaboration, alerts and notifications, search and mobile access. ·         Open - meaning the BI platform integrates with any data source, ETL tool, business application, application server, security infrastructure, portal technology as well as any ODBC compliant third party analytical tool. The suite accesses data from multiple heterogeneous sources--including popular relational and multidimensional data sources and major ERP and CRM applications from Oracle and SAP. ·         Integrated - meaning the BI platform is based on an architecturally integrated technology foundation built on an open, standards based service oriented architecture.  The platform features a common enterprise information model, common security model and a common configuration, deployment and systems management framework. To summarize, Oracle Business Intelligence is a comprehensive, integrated BI platform that lets you define strategy, identify objectives, assign ownership, define KPI's, collaborate, take action, monitor, report and do course corrections all form a single interface and a single system. The platform's integrated metadata model and task based design ensures that the entire workflow from defining strategy to execution to monitoring is completely integrated delivering end to end visibility, transparency and agility. Click here to learn more about Oracle BI 11g. 

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  • Guidance: How to layout you files for an Ideal Solution

    - by Martin Hinshelwood
    Creating a solution and having it maintainable over time is an art and not a science. I like being pedantic and having a place for everything, no matter how small. For setting up the Areas to run Multiple projects under one solution see my post on  When should I use Areas in TFS instead of Team Projects and for an explanation of branching see Guidance: A Branching strategy for Scrum Teams. Update 17th May 2010 – We are currently trialling running a single Sprint branch to improve our history. Whenever I setup a new Team Project I implement the basic version control structure. I put “readme.txt” files in the folder structure explaining the different levels, and a solution file called “[Client].[Product].sln” located at “$/[Client]/[Product]/DEV/Main” within version control. Developers should add any projects you need to create to that solution in the format “[Client].[Product].[ProductArea].[Assembly]” and they will automatically be picked up and built automatically when you setup Automated Builds using Team Foundation Build. All test projects need to be done using MSTest to get proper IDE and Team Foundation Build integration out-of-the-box and be named for the assembly that it is testing with a naming convention of “[Client].[Product].[ProductArea].[Assembly].Tests” Here is a description of the folder layout; this content should be replicated in readme files under version control in the relevant locations so that even developers new to the project can see how to do it. Figure: The Team Project level - at this level there should be a folder for each the products that you are building if you are using Areas correctly in TFS 2010. You should try very hard to avoided spaces as these things always end up in a URL eventually e.g. "Code Auditor" should be "CodeAuditor". Figure: Product Level - At this level there should be only 3 folders (DEV, RELESE and SAFE) all of which should be in capitals. These folders represent the three stages of your application production line. Each of them may contain multiple branches but this format leaves all of your branches at the same level. Figure: The DEV folder is where all of the Development branches reside. The DEV folder will contain the "Main" branch and all feature branches is they are being used. The DEV designation specifies that all code in every branch under this folder has not been released or made ready for release. And feature branches MUST merge (Forward Integrate) from Main and stabilise prior to merging (Reverse Integration) back down into Main and being decommissioned. Figure: In the Feature branching scenario only merges are allowed onto Main, no development can be done there. Once we have a mature product it is important that new features being developed in parallel are kept separate. This would most likely be used if we had more than one Scrum team working on a single product. Figure: when we are ready to do a release of our software we will create a release branch that is then stabilised prior to deployment. This protects the serviceability of of our released code allowing developers to fix bugs and re-release an existing version. Figure: All bugs found on a release are fixed on the release.  All bugs found in a release are fixed on the release and a new deployment is created. After the deployment is created the bug fixes are then merged (Reverse Integration) into the Main branch. We do this so that we separate out our development from our production ready code.  Figure: SAFE or RTM is a read only record of what you actually released. Labels are not immutable so are useless in this circumstance.  When we have completed stabilisation of the release branch and we are ready to deploy to production we create a read-only copy of the code for reference. In some cases this could be a regulatory concern, but in most cases it protects the company building the product from legal entanglements based on what you did or did not release. Figure: This allows us to reference any particular version of our application that was ever shipped.   In addition I am an advocate of having a single solution with all the Project folders directly under the “Trunk”/”Main” folder and using the full name for the project folders.. Figure: The ideal solution If you must have multiple solutions, because you need to use more than one version of Visual Studio, name the solutions “[Client].[Product][VSVersion].sln” and have it reside in the same folder as the other solution. This makes it easier for Automated build and improves the discoverability of your code and its dependencies. Send me your feedback!   Technorati Tags: VS ALM,VSTS Developing,VS 2010,VS 2008,TFS 2010,TFS 2008,TFBS

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  • Creating the Business Card Request InfoPath Form

    - by JKenderdine
    Business Card Request Demo Files Back in January I spoke at SharePoint Saturday Virginia Beach about InfoPath forms and Web Part deployment.  Below is some of the information and details regarding the form I created for the session.  There are many blogs and Microsoft articles on how to create a basic form so I won’t repeat that information here.   This blog will just explain a few of the options I chose when creating the solutions for SPS Virginia Beach.  The above link contains the zipped package files of the two InfoPath forms(no code solution and coded solution), the list template for the Location list I used, and the PowerPoint deck.  If you plan to use these templates, you will need to update the forms to work within your own environments (change data connections, code links, etc.).  Also, you must have the SharePoint Enterprise version, with InfoPath Services configured in order to use the Web Browser enabled forms. So what are the requirements for this template? Business Card Request Form Template Design Plan: Gather user information and requirements for card Pull in as much user information as possible. Use data from the user profile web services as a data source Show and hide fields as necessary for requirements Create multiple views – one for those submitting the form and Another view for the executive assistants placing the orders. Browser based form integrated into SharePoint team site Submitted directly to form library The base form was created using the blank template.  The table and rows were added using Insert tab and selecting Custom Table.  The use of tables is a great way to make sure everything lines up.  You do have to split the tables from time to time.  If you’ve ever split cells and then tried to re-align one to find that you impacted the others, you know why.  Here is what the base form looks like in InfoPath.   Show and hide fields as necessary for requirements You will notice I also used Sections within the form.  These show or hide depending on options selected or whether or not fields are blank.  This is a great way to prevent your users from feeling overwhelmed with a large form (this one wouldn’t apply).  Although not used in this one, you can also use various views with a tab interface.  I’ll show that in another post. Gather user information and requirements for card Pull in as much user information as possible. Use data from the user profile web services as a data source Utilizing rules you can load data when the form initiates (Data tab, Form Load).  Anything you can automate is always appreciated by the user as that is data they don’t have to enter.  For example, loading their user id or other user information on load: Always keep in mind though how much data you load and the method for loading that data (through rules, code, etc.).  They have an impact on form performance.  The form will take longer to load if you bring in a ton of data from external sources.  Laura Rogers has a great blog post on using the User Information List to load user information.   If the user has logged into SharePoint, then this can be used quite effectively and without a huge performance hit.   What I have found is that using the User Profile service via code behind or the Web Service “GetUserProfileByName” (as above) can take more time to load the user data.  Just food for thought. You must add the data connection in order for the above rules to work.  You can connect to the data connection through the Data tab, Data Connections or select Manage Data Connections link which appears under the main data source.  The data connections can be SharePoint lists or libraries, SQL data tables, XML files, etc.  Create multiple views – one for those submitting the form and Another view for the executive assistants placing the orders. You can also create multiple views for the users to enhance their experience.  Once they’ve entered the information and submitted their request for business cards, they don’t really need to see the main data input screen any more.  They just need to view what they entered. From the Page Design tab, select New View and give the view a name.  To review the existing views, click the down arrow under View: The ReviewView shows just what the user needs and nothing more: Once you have everything configured, the form should be tested within a Test SharePoint environment before final deployment to production.  This validates you don’t have any rules or code that could impact the server negatively. Submitted directly to form library   You will need to know the form library that you will be submitting to when publishing the template.  Configure the Submit data connection to connect to this library.  There is already one configured in the sample,  but it will need to be updated to your environment prior to publishing. The Design template is different from the Published template.  While both have the .XSN extension, the published template contains all the “package” information for the form.  The published form is what is loaded into Central Admin, not the design template. Browser based form integrated into SharePoint team site In Central Admin, under General Settings, select Manage Form Templates.  Upload the published form template and Activate it to a site collection. Now it is available as a content type to select in the form library.  Some documentation on publishing form templates:  Technet – Manage administrator approved form templates And that’s all our base requirements.  Hope this helps to give a good start.

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  • The Sound of Two Toilets Flushing: Constructive Criticism for Virgin Atlantic Complaints Department

    - by Geertjan
    I recently had the experience of flying from London to Johannesburg and back with Virgin Atlantic. The good news was that it was the cheapest flight available and that the take off and landing were absolutely perfect. Hence I really have no reason to complain. Instead, I'd like to offer some constructive criticism which hopefully Richard Branson will find sometime while googling his name. Or maybe someone from the Virgin Atlantic Complaints Department will find it, whatever, just want to put this information out there. Arrangement of restroom facilities. Maybe next time you design an airplane, consider not putting your toilets at a right angle right next to your rows of seats. Being able to reach, without even needing to stretch your arm, from your seat to close, yet again, a toilet door that someone, someone obviously sitting very far from the toilets, carelessly forgot to close is not an indicator of quality interior design. Have you noticed how all other airplanes have their toilets in a cubicle separated from the rows of seats? On those airplanes, people sitting in the seats near the toilets are not constantly being woken up throughout the night whenever someone enters/exits the toilet, whenever the light in the toilet is suddenly switched on, and whenever one of the toilets flushes. Bonus points for Virgin Atlantic passengers in the seats adjoining the toilets is when multiple toilets are flushed simultaneously and multiple passengers enter/exit them at the same time, a bit like an unasked for low budget musical of suddenly illuminated grumpy people in crumpled clothes. What joy that brings at 3 AM is hard to describe. Seats with extra leg room. You know how other airplanes have the seats with the extra leg room? You know what those seats tend to have? Extra leg room. It's really interesting how Virgin Atlantic's seats with extra leg room actually have no extra leg room at all. It should have been a give away, the fact that these special seats are found in the same rows as the standard seats, rather than on the cusp of real glory which is where most airlines put their extra leg room seats, with the only actual difference being that they have a slightly different color. Had you called them "seats with a different color" (i.e., almost not quite green, rather than something vaguely hinting at blue), at least I'd have known what I was getting. Picture the joy at 3 AM, rudely awakened from nightmarish slumber, partly grateful to have been released from a grayish dream of faceless zombies resembling one or two of those in a recent toilet line, by multiple adjoining toilets flushing simultaneously, while you're sitting in a seat with extra leg room that has exactly as much leg room as the seats in neighboring rows. You then have a choice of things to be sincerely annoyed about. Food from the '80's. In the '80's, airplane food came in soggy containers and even breakfast, the most important meal of the day, was a sad heap of vaguely gray colors. The culinary highlight tended to be a squashed tomato, which must have been mashed to a pulp with a brick prior to being regurgitated by a small furry animal, and there was also always a piece of immensely horrid pumpkin, as well as a slice of spongy something you'd never seen before. Sausages and mash at 6 AM on an airplane was always a heavy lump of horribleness. Thankfully, all airlines throughout the world changed from this puke inducing strategy around 1987 sometime. Not Virgin Atlantic, of course. The fatty sausages and mash are still there, bringing you flashbacks to Duran Duran, which is what you were listening to (on your walkman) the last time you saw it in an airplane. Even the golden oldie "squashed tomato attached by slime to three wet peas" is on the menu. How wonderful to have all this in a cramped seat with a long row of early morning bleariness lined up for the toilets, right at your side, bumping into your elbow, groggily, one by one, one after another, more and more, fumble-open-door-silence-flush-fumble-open-door, and on and on, while you tentatively push your fork through a soggy pile of colorless mush, fighting the urge to throw up on the stinky socks of whatever nightmarish zombie is bumping into your elbow at the time. But, then again, the plane landed without a hitch, in fact, extremely smoothly, so I'm certainly not blaming the pilots.

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  • Silverlight Relay Commands

    - by George Evjen
    v\:* {behavior:url(#default#VML);} o\:* {behavior:url(#default#VML);} w\:* {behavior:url(#default#VML);} .shape {behavior:url(#default#VML);} Normal 0 false false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} I am fairly new at Silverlight development and I usually have an issue that needs research every day. Which I enjoy, since I like the idea of going into a day knowing that I am  going to learn something new. The issue that I am currently working on centers around relay commands. I have a pretty good handle on Relay Commands and how we use them within our applications. <Button Command="{Binding ButtonCommand}" CommandParameter="NewRecruit" Content="New Recruit" /> Here in our xaml we have a button. The button has a Command and a CommandParameter. The command binds to the ButtonCommand that we have in our ViewModel RelayCommand _buttonCommand;         /// <summary>         /// Gets the button command.         /// </summary>         /// <value>The button command.</value>         public RelayCommand ButtonCommand         {             get             {                 if (_buttonCommand == null)                 {                     _buttonCommand = new RelayCommand(                         x => x != null && x.ToString().Length > 0 && CheckCommandAvailable(x.ToString()),                         x => ExecuteCommand(x.ToString()));                 }                 return _buttonCommand;             }         }   In our relay command we then do some checks with a lambda expression. We check if the command  parameter is null, is the length greater than 0 and we have a CheckCommandAvailable method that will tell  us if the button is even enabled. After we check on these three items we then pass the command parameter to an action method. This is all pretty straight forward, the issue that we solved a few days ago centered around having a control that needed to use a Relay Command and this control was a nested control and was using a different DataContext. The example below illustrates how we handled this scenario. In our xaml usercontrol we had to set a name to this control. <Controls3:RadTileViewItem x:Class="RecruitStatusTileView"     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"     xmlns:d="http://schemas.microsoft.com/expression/blend/2008"     xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"      xmlns:Controls1="clr-namespace:Telerik.Windows.Controls;assembly=Telerik.Windows.Controls"      xmlns:Controls2="clr-namespace:Telerik.Windows.Controls;assembly=Telerik.Windows.Controls.Input"      xmlns:Controls3="clr-namespace:Telerik.Windows.Controls;assembly=Telerik.Windows.Controls.Navigation"      mc:Ignorable="d" d:DesignHeight="400" d:DesignWidth="800" Header="{Binding Title,Mode=TwoWay}" MinimizedHeight="100"                             x:Name="StatusView"> Here we are using a telerik RadTileViewItem. We set the name of this control to “StatusView”. In our button control we set our command parameters and commands different than the example above. <HyperlinkButton Content="{Binding BigBoardButtonText, Mode=TwoWay}" CommandParameter="{Binding 'Position.PositionName'}" Command="{Binding ElementName=StatusView, Path=DataContext.BigBoardCommand, Mode=TwoWay}" /> This hyperlink button lives in a ListBox control and this listbox has an ItemSource of PositionSelectors. The Command Parameter is binding to the Position.Position property of that PositionSelectors object. This again is pretty straight forward again. What gets a bit tricky is the Command property in the hyperlink. It is binding to the element name we created in the user control (StatusView) Because this hyperlink is in a listbox and is in the item template it doesn’t have a direct handle on the DataContext that the RadTileViewItem has so we have to make sure it does. We do that by binding to the element name of status view then set the path to DataContext.BigBoardCommand. BigBoardCommand is the name of the RelayCommand in the view model. private RelayCommand _bigBoardCommand = null;         /// <summary>         /// Gets the big board command.         /// </summary>         /// <value>The big board command.</value>         public RelayCommand BigBoardCommand         {             get             {                 if (_bigBoardCommand == null)                 {                     _bigBoardCommand = new RelayCommand(x => true, x => AddToBigBoard(x.ToString()));                 }                 return _bigBoardCommand;             }         } From there we check for true again and then call the action and pass in the parameter that we had as the command parameter. What we are working on now is a bit trickier than this second example. In the above example we are only creating this TileViewItem with this name “StatusView” once. In another part of our application we are generating multiple TileViewItems, so we cannot set the name in the control as we cant have multiple controls with the same name. When we run the application we get an error that reads that the value is out of expected range. My searching has led me to think we cannot have multiple controls with the same name. This is today’s problem and Ill post the solution to this once it is found.

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  • await, WhenAll, WaitAll, oh my!!

    - by cibrax
    If you are dealing with asynchronous work in .NET, you might know that the Task class has become the main driver for wrapping asynchronous calls. Although this class was officially introduced in .NET 4.0, the programming model for consuming tasks was much more simplified in C# 5.0 in .NET 4.5 with the addition of the new async/await keywords. In a nutshell, you can use these keywords to make asynchronous calls as if they were sequential, and avoiding in that way any fork or callback in the code. The compiler takes care of the rest. I was yesterday writing some code for making multiple asynchronous calls to backend services in parallel. The code looked as follow, var allResults = new List<Result>(); foreach(var provider in providers) { var results = await provider.GetResults(); allResults.AddRange(results); } return allResults; You see, I was using the await keyword to make multiple calls in parallel. Something I did not consider was the overhead this code implied after being compiled. I started an interesting discussion with some smart folks in twitter. One of them, Tugberk Ugurlu, had the brilliant idea of actually write some code to make a performance comparison with another approach using Task.WhenAll. There are two additional methods you can use to wait for the results of multiple calls in parallel, WhenAll and WaitAll. WhenAll creates a new task and waits for results in that new task, so it does not block the calling thread. WaitAll, on the other hand, blocks the calling thread. This is the code Tugberk initially wrote, and I modified afterwards to also show the results of WaitAll. class Program { private static Func<Stopwatch, Task>[] funcs = new Func<Stopwatch, Task>[] { async (watch) => { watch.Start(); await Task.Delay(1000); Console.WriteLine("1000 one has been completed."); }, async (watch) => { await Task.Delay(1500); Console.WriteLine("1500 one has been completed."); }, async (watch) => { await Task.Delay(2000); Console.WriteLine("2000 one has been completed."); watch.Stop(); Console.WriteLine(watch.ElapsedMilliseconds + "ms has been elapsed."); } }; static void Main(string[] args) { Console.WriteLine("Await in loop work starts..."); DoWorkAsync().ContinueWith(task => { Console.WriteLine("Parallel work starts..."); DoWorkInParallelAsync().ContinueWith(t => { Console.WriteLine("WaitAll work starts..."); WaitForAll(); }); }); Console.ReadLine(); } static async Task DoWorkAsync() { Stopwatch watch = new Stopwatch(); foreach (var func in funcs) { await func(watch); } } static async Task DoWorkInParallelAsync() { Stopwatch watch = new Stopwatch(); await Task.WhenAll(funcs[0](watch), funcs[1](watch), funcs[2](watch)); } static void WaitForAll() { Stopwatch watch = new Stopwatch(); Task.WaitAll(funcs[0](watch), funcs[1](watch), funcs[2](watch)); } } After running this code, the results were very concluding. Await in loop work starts... 1000 one has been completed. 1500 one has been completed. 2000 one has been completed. 4532ms has been elapsed. Parallel work starts... 1000 one has been completed. 1500 one has been completed. 2000 one has been completed. 2007ms has been elapsed. WaitAll work starts... 1000 one has been completed. 1500 one has been completed. 2000 one has been completed. 2009ms has been elapsed. The await keyword in a loop does not really make the calls in parallel.

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  • Computer Networks UNISA - Chap 8 &ndash; Wireless Networking

    - by MarkPearl
    After reading this section you should be able to Explain how nodes exchange wireless signals Identify potential obstacles to successful transmission and their repercussions, such as interference and reflection Understand WLAN architecture Specify the characteristics of popular WLAN transmission methods including 802.11 a/b/g/n Install and configure wireless access points and their clients Describe wireless MAN and WAN technologies, including 802.16 and satellite communications The Wireless Spectrum All wireless signals are carried through the air by electromagnetic waves. The wireless spectrum is a continuum of the electromagnetic waves used for data and voice communication. The wireless spectrum falls between 9KHZ and 300 GHZ. Characteristics of Wireless Transmission Antennas Each type of wireless service requires an antenna specifically designed for that service. The service’s specification determine the antenna’s power output, frequency, and radiation pattern. A directional antenna issues wireless signals along a single direction. An omnidirectional antenna issues and receives wireless signals with equal strength and clarity in all directions The geographical area that an antenna or wireless system can reach is known as its range Signal Propagation LOS (line of sight) uses the least amount of energy and results in the reception of the clearest possible signal. When there is an obstacle in the way, the signal may… pass through the object or be obsrobed by the object or may be subject to reflection, diffraction or scattering. Reflection – waves encounter an object and bounces off it. Diffraction – signal splits into secondary waves when it encounters an obstruction Scattering – is the diffusion or the reflection in multiple different directions of a signal Signal Degradation Fading occurs as a signal hits various objects. Because of fading, the strength of the signal that reaches the receiver is lower than the transmitted signal strength. The further a signal moves from its source, the weaker it gets (this is called attenuation) Signals are also affected by noise – the electromagnetic interference) Interference can distort and weaken a wireless signal in the same way that noise distorts and weakens a wired signal. Frequency Ranges Older wireless devices used the 2.4 GHZ band to send and receive signals. This had 11 communication channels that are unlicensed. Newer wireless devices can also use the 5 GHZ band which has 24 unlicensed bands Narrowband, Broadband, and Spread Spectrum Signals Narrowband – a transmitter concentrates the signal energy at a single frequency or in a very small range of frequencies Broadband – uses a relatively wide band of the wireless spectrum and offers higher throughputs than narrowband technologies The use of multiple frequencies to transmit a signal is known as spread-spectrum technology. In other words a signal never stays continuously within one frequency range during its transmission. One specific implementation of spread spectrum is FHSS (frequency hoping spread spectrum). Another type is known as DSS (direct sequence spread spectrum) Fixed vs. Mobile Each type of wireless communication falls into one of two categories Fixed – the location of the transmitted and receiver do not move (results in energy saved because weaker signal strength is possible with directional antennas) Mobile – the location can change WLAN (Wireless LAN) Architecture There are two main types of arrangements Adhoc – data is sent directly between devices – good for small local devices Infrastructure mode – a wireless access point is placed centrally, that all devices connect with 802.11 WLANs The most popular wireless standards used on contemporary LANs are those developed by IEEE’s 802.11 committee. Over the years several distinct standards related to wireless networking have been released. Four of the best known standards are also referred to as Wi-Fi. They are…. 802.11b 802.11a 802.11g 802.11n These four standards share many characteristics. i.e. All 4 use half duplex signalling Follow the same access method Access Method 802.11 standards specify the use of CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) to access a shared medium. Using CSMA/CA before a station begins to send data on an 802.11 network, it checks for existing wireless transmissions. If the source node detects no transmission activity on the network, it waits a brief period of time and then sends its transmission. If the source does detect activity, it waits a brief period of time before checking again. The destination node receives the transmission and, after verifying its accuracy, issues an acknowledgement (ACT) packet to the source. If the source receives the ACK it assumes the transmission was successful, – if it does not receive an ACK it assumes the transmission failed and sends it again. Association Two types of scanning… Active – station transmits a special frame, known as a prove, on all available channels within its frequency range. When an access point finds the probe frame, it issues a probe response. Passive – wireless station listens on all channels within its frequency range for a special signal, known as a beacon frame, issued from an access point – the beacon frame contains information necessary to connect to the point. Re-association occurs when a mobile user moves out of one access point’s range and into the range of another. Frames Read page 378 – 381 about frames and specific 802.11 protocols Bluetooth Networks Sony Ericson originally invented the Bluetooth technology in the early 1990s. In 1998 other manufacturers joined Ericsson in the Special Interest Group (SIG) whose aim was to refine and standardize the technology. Bluetooth was designed to be used on small networks composed of personal communications devices. It has become popular wireless technology for communicating among cellular telephones, phone headsets, etc. Wireless WANs and Internet Access Refer to pages 396 – 402 of the textbook for details.

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  • High Availability for IaaS, PaaS and SaaS in the Cloud

    - by BuckWoody
    Outages, natural disasters and unforeseen events have proved that even in a distributed architecture, you need to plan for High Availability (HA). In this entry I'll explain a few considerations for HA within Infrastructure-as-a-Service (IaaS), Platform-as-a-Service (PaaS) and Software-as-a-Service (SaaS). In a separate post I'll talk more about Disaster Recovery (DR), since each paradigm has a different way to handle that. Planning for HA in IaaS IaaS involves Virtual Machines - so in effect, an HA strategy here takes on many of the same characteristics as it would on-premises. The primary difference is that the vendor controls the hardware, so you need to verify what they do for things like local redundancy and so on from the hardware perspective. As far as what you can control and plan for, the primary factors fall into three areas: multiple instances, geographical dispersion and task-switching. In almost every cloud vendor I've studied, to ensure your application will be protected by any level of HA, you need to have at least two of the Instances (VM's) running. This makes sense, but you might assume that the vendor just takes care of that for you - they don't. If a single VM goes down (for whatever reason) then the access to it is lost. Depending on multiple factors, you might be able to recover the data, but you should assume that you can't. You should keep a sync to another location (perhaps the vendor's storage system in another geographic datacenter or to a local location) to ensure you can continue to serve your clients. You'll also need to host the same VM's in another geographical location. Everything from a vendor outage to a network path problem could prevent your users from reaching the system, so you need to have multiple locations to handle this. This means that you'll have to figure out how to manage state between the geo's. If the system goes down in the middle of a transaction, you need to figure out what part of the process the system was in, and then re-create or transfer that state to the second set of systems. If you didn't write the software yourself, this is non-trivial. You'll also need a manual or automatic process to detect the failure and re-route the traffic to your secondary location. You could flip a DNS entry (if your application can tolerate that) or invoke another process to alias the first system to the second, such as load-balancing and so on. There are many options, but all of them involve coding the state into the application layer. If you've simply moved a state-ful application to VM's, you may not be able to easily implement an HA solution. Planning for HA in PaaS Implementing HA in PaaS is a bit simpler, since it's built on the concept of stateless applications deployment. Once again, you need at least two copies of each element in the solution (web roles, worker roles, etc.) to remain available in a single datacenter. Also, you need to deploy the application again in a separate geo, but the advantage here is that you could work out a "shared storage" model such that state is auto-balanced across the world. In fact, you don't have to maintain a "DR" site, the alternate location can be live and serving clients, and only take on extra load if the other site is not available. In Windows Azure, you can use the Traffic Manager service top route the requests as a type of auto balancer. Even with these benefits, I recommend a second backup of storage in another geographic location. Storage is inexpensive; and that second copy can be used for not only HA but DR. Planning for HA in SaaS In Software-as-a-Service (such as Office 365, or Hadoop in Windows Azure) You have far less control over the HA solution, although you still maintain the responsibility to ensure you have it. Since each SaaS is different, check with the vendor on the solution for HA - and make sure you understand what they do and what you are responsible for. They may have no HA for that solution, or pin it to a particular geo, or perhaps they have a massive HA built in with automatic load balancing (which is often the case).   All of these options (with the exception of SaaS) involve higher costs for the design. Do not sacrifice reliability for cost - that will always cost you more in the end. Build in the redundancy and HA at the very outset of the project - if you try to tack it on later in the process the business will push back and potentially not implement HA. References: http://www.bing.com/search?q=windows+azure+High+Availability  (each type of implementation is different, so I'm routing you to a search on the topic - look for the "Patterns and Practices" results for the area in Azure you're interested in)

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  • Adaptive Connections For ADFBC

    - by Duncan Mills
    Some time ago I wrote an article on Adaptive Bindings showing how the pageDef for a an ADF UI does not have to be wedded to a fixed data control or collection / View Object. This article has proved pretty popular, so as a follow up I wanted to cover another "Adaptive" feature of your ADF applications, the ability to make multiple different connections from an Application Module, at runtime. Now, I'm sure you'll be aware that if you define your application to use a data-source rather than a hard-coded JDBC connection string, then you have the ability to change the target of that data-source after deployment to point to a different database. So that's great, but the reality of that is that this single connection is effectively fixed within the application right?  Well no, this it turns out is a common misconception. To be clear, yes a single instance of an ADF Application Module is associated with a single connection but there is nothing to stop you from creating multiple instances of the same Application Module within the application, all pointing at different connections.  If fact this has been possible for a long time using a custom extension point with code that which extends oracle.jbo.http.HttpSessionCookieFactory. This approach, however, involves writing code and no-one likes to write any more code than they need to, so, is there an easier way? Yes indeed.  It is in fact  a little publicized feature that's available in all versions of 11g, the ELEnvInfoProvider. What Does it Do?  The ELEnvInfoProvider  is  a pre-existing class (the full path is  oracle.jbo.client.ELEnvInfoProvider) which you can plug into your ApplicationModule configuration using the jbo.envinfoprovider property. Visuallty you can set this in the editor, or you can also set it directly in the bc4j.xcfg (see below for an example) . Once you have plugged in this envinfoprovider, here's the fun bit, rather than defining the hard-coded name of a datasource instead you can plug in a EL expression for the connection to use.  So what's the benefit of that? Well it allows you to defer the selection of a connection until the point in time that you instantiate the AM. To define the expression itself you'll need to do a couple of things: First of all you'll need a managed bean of some sort – e.g. a sessionScoped bean defined in your ViewController project. This will need a getter method that returns the name of the connection. Now this connection itself needs to be defined in your Application Server, and can be managed through Enterprise Manager, WLST or through MBeans. (You may need to read the documentation [http://docs.oracle.com/cd/E28280_01/web.1111/b31974/deployment_topics.htm#CHDJGBDD] here on how to configure connections at runtime if you're not familiar with this)   The EL expression (e.g. ${connectionManager.connection} is then defined in the configuration by editing the bc4j.xcfg file (there is a hyperlink directly to this file on the configuration editing screen in the Application Module editor). You simply replace the hardcoded JDBCName value with the expression.  So your cfg file would end up looking something like this (notice the reference to the ELEnvInfoProvider that I talked about earlier) <BC4JConfig version="11.1" xmlns="http://xmlns.oracle.com/bc4j/configuration">   <AppModuleConfigBag ApplicationName="oracle.demo.model.TargetAppModule">   <AppModuleConfig DeployPlatform="LOCAL"  JDBCName="${connectionManager.connection}" jbo.project="oracle.demo.model.Model" name="TargetAppModuleLocal" ApplicationName="oracle.demo.model.TargetAppModule"> <AM-Pooling jbo.doconnectionpooling="true"/> <Database jbo.locking.mode="optimistic">       <Security AppModuleJndiName="oracle.demo.model.TargetAppModule"/>    <Custom jbo.envinfoprovider="oracle.jbo.client.ELEnvInfoProvider"/> </AppModuleConfig> </AppModuleConfigBag> </BC4JConfig> Still Don't Quite Get It? So far you might be thinking, well that's fine but what difference does it make if the connection is resolved "just in time" rather than up front and changed as required through Enterprise Manager? Well a trivial example would be where you have a single application deployed to your application server, but for different users you want to connect to different databases. Because, the evaluation of the connection is deferred until you first reference the AM you have a decision point that can take the user identity into account. However, think about it for a second.  Under what circumstances does a new AM get instantiated? Well at the first reference of the AM within the application yes, but also whenever a Task Flow is entered -  if the data control scope for the Task Flow is ISOLATED.  So the reality is, that on a single screen you can embed multiple Task Flows, all of which are pointing at different database connections concurrently. Hopefully you'll find this feature useful, let me know... 

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  • Errors when switching to specific static IP

    - by michaelc
    I had a Fedora box running using my static IP 69.169.136.6, etc, all configured according to what the ISP required. Just recently the hard drive failed (and I should have been keeping better backups) - while it is being recovered I would like to put up a webpage on my Archlinux PC explaining the problem - I presently do not have sufficient access to change the DNS record assigned to the domain. When I change my ip address while my system is running to 69.169.136.6, ifconfig reports the new ip address, but http://whatismyip.com/ does not. When I change it and reboot, I can't ping - the message I recieve is "connect: Network is unreachable" (when given one of google.com 's IP addresses - hostnames give me ping: unknown host xxx). Until I have access to the DNS system, what can I do to make this work? Edit: With new IP address, same problem, IP is now 69.169.136.29. Some commands might be useful: #ping 69.169.136.1 PING 69.169.136.1 (69.169.136.1) 56(84) bytes of data. 64 bytes from 69.169.136.1: icmp_seq=1 ttl=64 time=0.377 ms #ping 69.169.190.211 connect: Network is unreachable #ping 208.72.160.67 connect: Network is unreachable #ifconfig eth0 Link encap:Ethernet HWaddr 00:E0:4D:97:23:9B inet addr:69.169.136.29 Bcast:69.169.137.255 Mask:255.255.254.0 inet6 addr: fe80::2e0:4dff:fe97:239b/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:132091 errors:0 dropped:0 overruns:0 frame:0 TX packets:17 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:9635179 (9.1 Mb) TX bytes:1322 (1.2 Kb) Interrupt:29 Base address:0x6000 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:48 errors:0 dropped:0 overruns:0 frame:0 TX packets:48 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:2480 (2.4 Kb) TX bytes:2480 (2.4 Kb) #ip route 69.169.136.0/23 dev eth0 proto kernel scope link src 69.169.136.29 #cat /etc/resolv.conf # Generated by dhcpcd #nameserver 208.67.222.222 #nameserver 208.67.220.220 nameserver 69.169.190.211 nameserver 208.72.160.67 # /etc/resolv.conf.tail can replace this line Update: have new static IP addresses, verified to work in Windows... Relevant portions of /etc/rc.conf below: #Static IP example #eth0="eth0 69.169.136.6 netmask 255.255.254.0 broadcast 69.169.136.1" #eth0="eth0 69.169.136.29 netmask 255.255.254.0 broadcast 69.169.137.255" eth0="eth0 69.169.136.32 netmask 255.255.254.0 broadcast 69.169.137.255" #eth0="dhcp" INTERFACES=(eth0) # Routes to start at boot-up (in this order) # Declare each route then list in ROUTES # - prefix an entry in ROUTES with a ! to disable it # #gateway="default gw 192.168.0.1" gateway="default gw 69.169.136.1" #gateway="69.169.136.1" ROUTES=(!gateway) #ROUTES=()

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  • Query total page count via SNMP HP Laserjet

    - by Tim
    I was asked to get hold of the total pages counts for the 100+ printers we have at work. All of them are HP Laser or Business Jets of some description and the vast majority are connected via some form of HP JetDirect network card/switch. After many hours of typing in IP addresses and copying and pasting the relevant figure in to Excel I have now been asked to do this on a weekly basis. This led me to think there must be an easier way, as an IT professional I can surely work out some time saving method to solve this issue. Suffice it to say I do not feel very professional now after a day or so of trying to make SNMP work for me! From what I understand the first thing is to enable SNMP on the printer. Done. Next I would need something to query the SNMP bit. I decided to go open source and free and someone here recommended net-snmp as a decent tool (I would like to have just added the printers as nodes in SolarWinds but we are somewhat tight on licences apparently). Next I need the name of the MIB. For this I believe the HP-LASERJET-COMMON-MIB has the correct information in it. Downloaded this and added to net-snmp. Now I need the OID which I believe after much scouring is printed-media-simplex-count (we have no duplex printers, that we are interested in at least). Running the following command yields the following demoralising output: snmpget -v 2c -c public 10.168.5.1 HP-LASERJET-COMMON-MIB:.1.3.6.1.2.1.1.16.1.1.1 (the OID was derived from running: snmptranslate -IR -On printed-media-simplex-count Unlinked OID in HP-LASERJET-COMMON-MIB: hp ::= { enterprises 11 } Undefined identifier: enterprises near line 3 of C:/usr/share/snmp/mibs/HP-LASER JET-COMMON-MIB..txt .1.3.6.1.2.1.1.16.1.1.1 ) Unlinked OID in HP-LASERJET-COMMON-MIB: hp ::= { enterprises 11 } Undefined identifier: enterprises near line 3 of C:/usr/share/snmp/mibs/HP-LASER JET-COMMON-MIB..txt HP-LASERJET-COMMON-MIB:.1.3.6.1.2.1.1.16.1.1.1: Am I barking up the wrong tree completely with this? My aim was to script it all to output to a file for all the IP addresses of the printers and then plonk that in Excel for my lords and masters to digest at their leisure. I have a feeling I am using either the wrong MIB or the wrong OID from said MIB (or both). Does anyone have any pointers on this for me? Or should I give up and go back to navigationg each printers web page individually (hoping not).

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  • Bind an ip address to Postfix as outgoing ip

    - by jack
    Is that possible to bind all available public ip addresses on a server to one Postfix instance as its outgoing ip pool and let it choose a random ip or specified ip from the pool each time it sends out an email? If above is not possible, can it be configured to listen on one public ip address per instance and each time it delivers a message, it use the binded one as outgoing ip address.

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  • 2 VB Scripts one to remove Default Gateway and one to add a Default Gateway

    - by Tom
    Hello everyone, I have a client with a bunch of children using about 30 machines on a regular basis. All machines that the children user are set with Static IP Addresses. The machines that the kids use, I would like to be able to run a script that will remove the default gateway so they cant get to the Internet. Then I need another that will add the Default gateway, so Windows and software updates can be run. Both scripts need to use the domain admin account for permissions Any help would be greatly appreciated

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  • Any linux VPN clients that support DHCP over IPSec?

    - by mattis
    I am trying to connect to a SonicWall VPN that requires the client to fetch IP addresses from the SonicWall DHCP server. I have tried to use Linux Openswan U2.6.22/K2.6.31-20-generic (netkey), and I connect fine, but the server fails the connection: IKE Responder: WAN GroupVPN policy does not allow static IP for Virtual Adapter. Anyone that can help me with this? I am at my wits end.

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  • do i need a dns server?

    - by ajsie
    i have set up a website (lamp) in a vps from a hosting company. im wondering, in what circumstances would i want to set up a dns server on my vps? cause from what i have learned basically a dns just converts domain names into ip addresses. and at the moment my domain provider is doing this in their dns. so in what situations do i benefit from setting up an own dns server?

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  • Handling email bounces

    - by Roland
    I have a website with approx 60 000 registered users, now the server sends out emails to these users eg Birthday mailers etc. Now the problem is I get a lot of bounces. Is there a way to manage these bounces, email addresses that do not exist anymore to capture them. I'm running Centos.

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  • I have too many DNS servers configured

    - by Jon Will
    I have my laptop connecting to my wireless router, and I have told the router to issue out DNS via the DHCP lease. The laptop is configured to use the information. The router is configured to only issue two DNS server addresses from open dns, but the laptop reports Networking Dns Servers: 10.197.100.1 10.197.100.2 10.197.100.3 8.8.8.8 8.8.4.4 208.67.222.222 208.67.220.220 I have no idea where the laptop is getting these additional IPs as DNS. Please advise.

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  • WOL not working with two NIC's

    - by amazinghorse24
    We have recently moved from a windows 2003 server to an 08 R2. Running the program from the command line says that the magic packet has successfully been sent but it never actually reached the destination computer. We have two NIC's on the server. If I disable the NIC that isn't (currently) in use, WOL will work fine, but in the future we will need to use both NIC's. Also, we use MAC Addresses for WOL.

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  • How to iptables forward ppp0 to eth0

    - by HPHPHP2012
    need your help with get it routing properly. I've server with eth0 (external interface) and eth1(internal interface). eth1 is merged into the bridge br0 (172.16.1.1) I've installed the pptp and successfully configured it, so I got ppp0 interface (192.168.91.1) and got my VPN clients successfully connected. So I need your help to manage how to allow my VPN clients use internet connection (eth0). Below my configuration files, any help is much appreciated! Thank you! P.S. VPN clients are Windows Xp, Windows 7, Mac OS X Lion, Ubuntu 12.04, iOS 5.x cat /etc/pptpd.conf #local server ip address localip 192.168.91.1 #remote addresses remoteip 192.168.91.11-254,192.168.91.10 #translating ip addresses on this interface bcrelay br0 cat /etc/ppp/pptpd-options name pptpd refuse-pap refuse-chap refuse-mschap require-mschap-v2 require-mppe-128 ms-dns 8.8.8.8 ms-dns 8.8.4.4 nodefaultroute lock nobsdcomp auth logfile /var/log/pptpd.log cat /etc/nat-up #!/bin/sh SERVER_IP="aaa.aaa.aaa.aaa" LOCAL_IP="172.16.1.1" #eth0 with public ip PUBLIC="eth0" #br0 is internal bridge on eth1 interface INTERNAL="br0" #vpn VPN="ppp0" #local LOCAL="lo" iptables -F iptables -X iptables -t nat -F iptables -t nat -X iptables -t mangle -F iptables -t mangle -X iptables -P INPUT DROP iptables -P FORWARD DROP iptables -P OUTPUT ACCEPT echo 1 > /proc/sys/net/ipv4/ip_forward iptables -A INPUT -i $LOCAL -j ACCEPT iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT iptables -A INPUT -m state --state NEW ! -i $PUBLIC -j ACCEPT ####CLEAR CONFIG#### #iptables -A FORWARD -i $PUBLIC -o $INTERNAL -m state --state ESTABLISHED,RELATED -j ACCEPT #iptables -A FORWARD -i $PUBLIC -o $INTERNAL -j ACCEPT #iptables -A FORWARD -i $INTERNAL -o $PUBLIC -j ACCEPT #iptables -t nat -A POSTROUTING -j MASQUERADE ####THIS PART IS NOT HANDLING IT#### iptables -A FORWARD -i $PUBLIC -o $VPN -m state --state ESTABLISHED,RELATED -j ACCEPT iptables -A FORWARD -i $PUBLIC -o $VPN -j ACCEPT iptables -A FORWARD -s 192.168.91.0/24 -o $PUBLIC -j ACCEPT iptables -t nat -A POSTROUTING -s 192.168.91.0/24 -o $PUBLIC -j MASQUERADE # VPN - PPTPD iptables -A INPUT -p gre -s 0/0 -j ACCEPT iptables -A OUTPUT -p gre -m state --state RELATED,ESTABLISHED -j ACCEPT iptables -A INPUT -p tcp -s 0/0 --dport 1723 -j ACCEPT #SSH iptables -A INPUT -p tcp --dport 2222 -j ACCEPT iptables -A OUTPUT -p tcp --sport 2222 -j ACCEPT #BLACKLIST BLOCKDB="/etc/ip.blocked" IPS=$(grep -Ev "^#" $BLOCKDB) for i in $IPS do iptables -A INPUT -s $i -j DROP iptables -A OUTPUT -d $i -j DROP done

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  • what is ip 10.1.1.130 to which seems monitored by NT Kernel & System process on Windows 7?

    - by EndangeringSpecies
    I used netstat to see what is happening with network connections, and I see this weird ip address somehow listed together with PID 4 "NT Kernel & System", whatever that might be. Netstat describes it as a "local address" and there is no "foreign address" involved (btw, what are local and foreign addresses anyway?) In the column to the right there is neither "listening" nor "established" record, so no record at all there.

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  • How to specify what network interface to use with TTCP or IPERF?

    - by Sammy
    The PC has two Gigabit Ethernet ports. They function as two separate network adapters. I'm trying to do a simple loopback test between the two. I've tried TTCP and IPERF. They're giving me hard time because I'm using the same physical PC. Using pcattcp... On the receiver end: C:\PCATTCP-0114>pcattcp -r PCAUSA Test TCP Utility V2.01.01.14 (IPv4/IPv6) IP Version : IPv4 Started TCP Receive Test 0... TCP Receive Test Local Host : GIGA ************** Listening...: On TCPv4 0.0.0.0:5001 Accept : TCPv4 0.0.0.0:5001 <- 10.1.1.1:33904 Buffer Size : 8192; Alignment: 16384/0 Receive Mode: Sinking (discarding) Data Statistics : TCPv4 0.0.0.0:5001 <- 10.1.1.1:33904 16777216 bytes in 0.076 real seconds = 215578.95 KB/sec +++ numCalls: 2052; msec/call: 0.038; calls/sec: 27000.000 C:\PCATTCP-0114> On the transmitter end: C:\PCATTCP-0114>PCATTCP.exe -t 10.1.1.1 PCAUSA Test TCP Utility V2.01.01.14 (IPv4/IPv6) IP Version : IPv4 Started TCP Transmit Test 0... TCP Transmit Test Transmit : TCPv4 0.0.0.0 -> 10.1.1.1:5001 Buffer Size : 8192; Alignment: 16384/0 TCP_NODELAY : DISABLED (0) Connect : Connected to 10.1.1.1:5001 Send Mode : Send Pattern; Number of Buffers: 2048 Statistics : TCPv4 0.0.0.0 -> 10.1.1.1:5001 16777216 bytes in 0.075 real seconds = 218453.33 KB/sec +++ numCalls: 2048; msec/call: 0.037; calls/sec: 27306.667 C:\PCATTCP-0114> It's responding alright. But why does it say 0.0.0.0? Is it passing through only one of the network adapters? I want 10.1.1.1 to be the server (receiver) and 10.1.1.2 to be the client (transmitter). These are the IP addresses assigned manually to each network adapter. How do I specify these addresses in TTCP? There is also the IPERF tool which has the -B option. Unfortunately I've been only able to use this option to bind the server to the 10.1.1.1 address. I was unable to bind the client to the 10.1.1.2 address. I might be doing it wrong. Can the -B option be used for both the server as well as the client side? What does the syntax look like for the client?

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  • What "pieces" are needed in order to set up a cluster of physical servers?

    - by Chris Dutrow
    Background: Currently, we use Rackspace cloud servers. We have no intention to stop using them, but would like to look into setting up a cluster of physical servers (probably desktop computers in the $400 range with 8gb memory each) to offset some of our load and work as a secondary, more powerful, less reliable system. To put things in perspective, we can buy comparable desktop computers for the same price as we pay in one month to rent them on Rackspace Cloud. I understand that this is generally a dumb idea. However, in this particular instance, the server cluster is needed for its computation power. It is not mission-critical, it does not host a consumer-facing website, and if it goes down for a day or two, its not really a problem. Currently, we have access to business class verizon fios. If I understand correctly, we can get at least 25 dedicated IP addresses with this service, this should be enough. Requirements: Each server runs Linux Centos 6.3 Some of the servers run Python and execute processes from a task queue (Redis or RabbitMQ) Some of the servers are capable of serving static files and Python driven REST APIs Some of the servers host a Cassandra database cluster One or more of the servers are a Redis database servers One or more of the servers are PostgreSQL servers Questions: What kind of router or switch is needed? We would like the computers to be able to communicate effectively with each other via internal IP addresses. This is especially important for communicating with servers hosting Redis that need to be able to respond to requests very quickly. Are there special switches or routers that need to be used to connect the servers together? Are Desktop computers ok for this? We have found that we are mostly RAM-bottle necked, I understand that some servers have highly superior CPUs, but I'm not sure we need CPU power as much as we need RAM, which is cheap in Desktop computers. Will we have problems with the WIFI cards in the desktops or any other unexpected hardware limitation? What tools should be used to "image" the servers. For example, when we get an installation right for a Redis server or Cassandra node, are there tools that come with Linux Centos 6.3 to image the server to a USB drive or something like that? Or do we need to use some other software for this? What other things are we missing that we should be concerned about? Thanks so much!

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  • Windows Virtual Machine not seen by host (Mac OS X) using VMWare Fusion

    - by Malkuth
    Hi, I installed Windows XP with VMware Fusion on my MacBook and while internet works, Windows can ping the Mac, etc. from the Mac or any other machine in the network we can not see the Virtual Machine. In between, I use bridged option and obtain the the VM's IP dynamically; tried also static assignment from the free addresses but the problem persisted. Any ideas what is wrong?

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  • What are some of the best wireless routers for a price-conscious home power-user?

    - by Alain
    I'm extremely dissatisfied with the 'popular' choice for routers in homes and small offices. They are expensive (upwards of 60$), lack a great deal of useful configuration options, and seem to need to be restarted quite often. (Linksys comes to mind). I've been on the market for a good router lately, and slowly collecting a set of requirements I feel good routers should meet. Maximum number of TCP/IP connections. - This isn't something I see any routers advertise, but in terms of supporting torrent applications, I've been screwed by routers that support less than 20 here. From what I understand a fairly standard number is 200, but there are not so expensive routers that support thousands. Router configuration menu - Most have standard menu's that let you set up basic things like your wireless network encryption settings, uPnP, and maybe even DMZ (demilitarized zones). An absolute requirement for me, however, are routers with good enough firmware to support: Explicit Port forwarding Assigning static local ips to specific mac addresses, or at least Port forwarding by MAC address Port, IP and MAC filtering Dynamic DNS service for home users who want to set up a server but have a dynamic IP Traffic shaping (ideally) - giving priority to packets from certain machines or over certain ports. Strong wireless signal - If getting a reliable signal requires me to be so close to the router that I can connect an Ethernet cable, it's not good enough. As many Ethernet ports as possible. - Because I want to be able to switch from console gaming to PC gaming without visiting my router. So far, the best thing I've stumbled upon (in the bargain bin at staples) was a 20$ retail plus router. It was meant to be the cheapest alternative until I could find something better to purchase online, but I was actually blown away by the firmware capabilities. It supports defining reserved bandwidth for certain network traffic, dynamic DNS, reserving local IPs for specific MAC addresses, etc. At 2 am when my roommate is killing our Internet with their torrents, I can limit their bandwidth without outright blacklisting them. I have, however, met serious limitations when it comes to network traffic between local machines. It claims a 300Mbps connection, but I have trouble streaming videos from my PC to my console or other laptops wirelessly. It has a meltdown and needs to be reset once in a while (no more than a couple times a month), and it's got a 200 connection limit. There 4 Ethernet ports in the back but I'm pretty sure the first doesn't work. So some great answers to this question would be: Any metrics you use to compare routers, and requirements you have for new candidates. The best routers you've found for supporting home servers, file management systems, high volume torrent traffic, good price/feature ratio, etc. Good configuration advice (aside from 'use Ethernet whenever possible') Thanks for your feedback and experiences!

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