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  • How to roll my own index in c#?

    - by bill seacham
    I need a faster way to create an index file. The application generates pairs of items to be indexed. I currently add each pair as it is generated to a sorted dictionary and then write it out to a disk file. This works well until the number of items added exceeds one million, at which time it slows to the point that is unacceptable. There can be as many as three million data items to be indexed. I prefer to avoid a database because I do not want to significantly increase the size of the deployment package, which is now less than one-half of one megabyte. I tried Access but it is even slower than the sorted dictionary -if it had an efficient bulk load utility then that might work, but I do not find such a tool for Access. Is there a better way to roll my own index?

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  • glassfish v3 - update all pakages via command line on linux

    - by orange80
    Does anyone know how to do this? I just want a one-shot command to "update everything" over the command line? This is for a remote server so it must be over the command line. I used: $ sudo pkg list -u to see the list of packages that are out of date, but I cannot for the life of me figure out how to say, "ok, update them". I have scoured the web for clues, but to no avail :( This is classic Sun Solaris-type patching that is the exact reason I am now on Linux. Please help!! Thanks :) Jamie

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  • Pentium 4 Computer Won't Power Up

    - by Harvey
    I have a faulty Pentium 4 workstation with data that I would like to retrieve. Here are the symptoms & what I've done so far: Machine is totally dead. Motherboard LED is lit but that is the only sign of life. I have replaced the power supply and bypassed the on/off switch. Tried a PC Analyzer motherboard tester but didn't have any power to the card. Unpluggged the P4 cable from the motherboard, hit the on/off switch, the power supply fan comes on and I get codes from the analyzer but nothing that seems to be of any value. Machine does not boot. Will not shut down by hitting the switch. Bad motherboard or could it be a bad CPU cooling fan?

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  • Where would an S3 upload speed cap originate?

    - by CoreyH
    I do a ton of uploading to S3 and am experiencing capped speeds and I can't quite figure out how to address it. The setup: Windows Server 2008 R2 x64, external HD, using a Java based upload tool called Jsh3ll and custom VBS scripts to kick the jobs off. Running one process at a time, I am always limited to about 4mbps. I have FiOS at 35/35mbps speeds, so it isn't an outright limit. AND, I can run parallel instances and can go all the way up to 35mbps, so I know the problem isn't gateway/nic/machine/amazon related. Running parallel instances works to a degree as a solution, but increases the complexity of my workflow greatly. Solving this would make my life dramatically easier. When I was first doing this I was playing around with a bunch of Windows TCP parameters and was able to briefly get unconstrained bandwidth, but it wasn't repeatable. Thoughts?

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  • What is causing my internet to be slow on one laptop but not the other and only at a distance?

    - by Matt Case
    I have a newer laptop, purchased within the last year (acer aspire 7740). This laptop does not have any problem connecting to wireless networks and indicates that the signal strength is excellent on most of the wireless networks I connect to. When the laptop is within 10 feet of my wireless router it gets 30 down 10 up. When it is farther away than 10 feet it will be lucky to get 3 down and 1 up. I also have an older laptop, purchased in 2005, that has no problems at all at the same range. None of my phones, gaming consoles or tablets have this problem. I am beginning to think that the problem must be some hardware defect with the wireless card. I can provide additional information if needed. Just thought I'd check to see what others thought because I've been working on computers my whole life and have never heard of this happening. I have also tried to change the channels on my wireless router and have had no success with this idea.

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  • Windows 8 gives "system thread exception not handled" after update

    - by Shobhit
    I have a 64-bit dell laptop which I recently upgraded from Windows 7 to Windows 8. Since then, it's creating a havoc in my life. The metro apps are not working; the system crashes once in a while and none of my games are running because I don't have the correct drivers for my graphics card (ATI 5000 series). Some days back, Windows downloaded an update and prompted me to restart. After that day, whenever I log in and fire up my desktop, I get all kinds of blue screen errors. The most common one looks something like this: - SYSTEM_THREAD_EXCEPTION_NOT_HANDLED. Please help me with how I can fix this, optionally how to go back to windows 7. Thanks.

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  • TrueCrypt-ed Windows XP reseting administrative password

    - by Predrag Punosevac
    I have inherited a laptop running Windows XP 64bit professional from a former system admin of my Lab. The laptop is encrypted with TrueCrypt and luckily I have a password for TrueCrypt and can boot and login into the guest account. However this is where my problems starts. There are four account on the laptop three of which do have administrative privileges. However nobody of two formers members of the lab and one current member remember their passwords. I was given the assignment of recovering 2TB of data from that laptop. How does one go about reseting administrative password in Windows in particularly in the presence of TrueCrypt? If you are wondering I have never used Windows in my life so the only thing I usually with any Windows machine is just wipe out entire HDD and install OpenBSD.

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  • Preferred apache permissions for www files with several authors

    - by user1316464
    I can't for the life of me figure out how to design my permissions scheme for my apache files. My requirements seem pretty simple: Apache should have standard permissions of RX for Directories and R for files Web authors should have RWX for Directories and RW for files Don't want to give any access to "other" Want new files/folders to inherit the proper permissions Here are the schemes I've tried 570 for directories and 460 for files Owner: Apache Group: Webdev The problem here is that new files created by users int the Webdev group are owned by user:Webdev and Apache can't read them. If Apache were in the group Webdev then it would also have the wrong permissions (ie it would have Write permissions to files) 750 for directories and 640 for files Owner: Webdev Group: Apache (Webdev is a member of Apache) The problem here is that there is only one webdev account and I have multiple people who need access to contribute. In theory this would work with only one developer if Webdev were also a member of the Apache group. Any ideas?

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  • Best way to perform authentication on every request

    - by Nik
    Hello. In my asp.net mvc 2 app, I'm wondering about the best way to implement this: For every incoming request I need to perform custom authorization before allowing the file to be served. (This is based on headers and contents of the querystring. If you're familiar with how Amazon S3 does rest authentication - exactly that). I'd like to do this in the most perfomant way possible, which probably means as light a touch as possible, with IIS doing as much of the actual work as possible. The service will need to handle GET requests, as well as writing new files coming in via POST/PUT requests. The requests are for an abitrary file, so it could be: GET http://storage.foo.com/bla/egg/foo18/something.bin POST http://storage.foo.com/else.txt Right now I've half implemented it using an IHttpHandler which handles all routes (with routes.RouteExistingFiles = true), but not sure if that's the best, or if I should be hooking into the lifecycle somewhere else? Many thanks for any pointers. (IIS7)

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  • Sometimes, scaling down a bitmap generates a bigger file. Why?

    - by Matías
    Hello, I'm trying to write a method to reduce the size of any image 50% each time is called but I've found a problem. Sometimes, I end up with a bigger filesize while the image is really just half of what it was. I'm taking care of DPI and PixelFormat. What else am I missing? Thank you for your time. public Bitmap ResizeBitmap(Bitmap origBitmap, int nWidth, int nHeight) { Bitmap newBitmap = new Bitmap(nWidth, nHeight, origBitmap.PixelFormat); newBitmap.SetResolution(origBitmap.HorizontalResolution, origBitmap.VerticalResolution); using (Graphics g = Graphics.FromImage((Image)newBitmap)) { g.InterpolationMode = InterpolationMode.HighQualityBicubic; g.DrawImage(origBitmap, 0, 0, nWidth, nHeight); } return newBitmap; }

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  • In Bloomberg API how do you specify to get FX forwards as a spread rather than absolute values?

    - by Nick Fortescue
    How do you explicitly request fx forwards as outrights using the bloomberg API? In the Bloomberg terminal you can choose whether to get FX Forwards as absolute rates (outrights) or as offsets from Spots (Points) by doing XDF, hitting 7, then the option is about half way down. 0 means outrights, and 1 means offfsets. With most defaults you can explicitly set them in the API, so your code gives the same result whichever computer you run on. How do you set this one in a V3 API query?

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  • "Input not Supported" on external monitor

    - by Shalan
    when it rains, it pours! Im helping a friend with his Dell Inspiron 1520. The hdd crashed and and top of that, the screen is cracked. I've replaced the hdd (SATA-5400), but the lcd replacement is only comin in a months time. I've tried to: hook the laptop up to an Acer 18.5" lcd monitor via VGA, boot up into Windows 7 installer, get to the Step-1 screen, Switch to external display (Function-F8) ...and get the "Input not supported" message on the Acer lcd. I know that this is a resolution problem, but cant for the life of me figure out how to solve this. I've also tried, hooking it up to my TV via Composite cables (got a VGA-Composite adaptor). Please could someone advise me what to do? -Thank u!

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  • Adobe Reader 9.0 memory leak while loading-unloading PDF files every one second indefinitely

    - by Total Starnger
    I have c++ written MFC based application that has PDF object viewer as a part of the implementation. A whole thing works just fine with Adobe Reader 8.0. Once I switched to Adobe Reader 9.0 as a default PDF reader, I keep experiencing small memory leak that forces my application to crash within a half an hour of continuous loading-unloading different PDF files. Any ideas what might cause this memory leak and is there any cure besides replacing Adobe Reader 9.0 with anything else? (Works fine with Foxit PDF reader as well, by the way..)

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  • How to get XML into a Dictionary with an Expression?

    - by DaveDev
    I have the following XML: <PerformancePanel page="PerformancePanel.ascx" title=""> <FundGroup heading="Net Life Managed Funds"> <fund id="17" countryid="N0" index="24103723" /> <fund id="81" countryid="N0" index="24103723" /> <fund id="127" countryid="N0" index="24103722" /> <fund id="345" countryid="N0" index="24103723" /> <fund id="346" countryid="N0" index="24103723" /> </FundGroup> <FundGroup heading="Net Life Specialist Funds"> <fund id="110" countryid="N0" index="24103717" /> <fund id="150" countryid="N0" index="24103719" /> <fund id="119" countryid="N0" index="24103720" /> <fund id="115" countryid="N0" index="24103727" /> <fund id="141" countryid="N0" index="24103711" /> <fund id="137" countryid="N0" /> <fund id="146" countryid="N0" /> <fund id="133" countryid="N0" /> <fund id="90" countryid="N0" /> <fund id="104" countryid="N0" /> <fund id="96" countryid="N0" /> </FundGroup> </PerformancePanel> I can get the data into an anonymous object as follows: var offlineFactsheet = new { PerformancePanels = (from panel in doc.Elements("PerformancePanel") select new PerformancePanel { PerformanceFunds = (from fg in panel.Elements("FundGroup") select new { Heading = (fg.Attribute("heading") == null) ? "" : (string)fg.Attribute("heading"), Funds = (from fund in fg.Elements("fund") select new Fund { FundId = (int)fund.Attribute("id"), CountryId = (string)fund.Attribute("countryid"), FundIndex = (fund.Attribute("index") == null) ? null : new Index { Id = (int)fund.Attribute("index") }, FundNameAppend = (fund.Attribute("append") == null) ? "" : (string)fund.Attribute("append") }).ToList() }).ToDictionary(xx => xx.Heading, xx => xx.Funds)}; I'm trying to change my code such that I can assign the dictionary directly to a property of the class I'm working in, as described in this question. I'd like to have a Dictionary() where each header text is the key to the list of funds under it. I'm having difficulty applying the example in the linked question because that only returns a string, and this needs to return the dictionary. This is the point that I got to before it occurred to me that I'm lost!!!: this.PerformancePanels = doc.Elements("PerformancePanel").Select(e => { var control = (PerformancePanel)LoadControl(this.OfflineFactsheetPath + (string)e.Attribute("page")); control.PerformanceFunds = e.Elements("FundGroup").Select(f => { List<Fund> funds = (from fund in e.Elements("fund") select new Fund { FundId = (int)fund.Attribute("id"), CountryId = (string)fund.Attribute("countryid"), FundIndex = (fund.Attribute("index") == null) ? null : new Index { Id = (int)fund.Attribute("index") }, FundNameAppend = (fund.Attribute("append") == null) ? "" : (string)fund.Attribute("append") }).ToList(); string heading = (e.Attribute("heading") == null) ? "" : (string)e.Attribute("heading"); }).ToDictionary(xx => heading, xx => Funds); return control; }).ToList(); Could someone point me in the right direction please? I'm not even sure if 'Expression' is the right terminology. Could someone fill me in on that too? Thanks.

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  • Django: order by count of a ForeignKey field?

    - by AP257
    This is almost certainly a duplicate question, in which case apologies, but I've been searching for around half an hour on SO and can't find the answer here. I'm probably using the wrong search terms, sorry. I have a User model and a Submission model. Each Submission has a ForeignKey field called user_submitted for the User who uploaded it. class Submission(models.Model): uploaded_by = models.ForeignKey('User') class User(models.Model): name = models.CharField(max_length=250 ) My question is pretty simple: how can I get a list of the three users with the most Submissions? I trued creating a num_submissions method on the User model: def num_submissions(self): num_submissions = Submission.objects.filter(uploaded_by=self).count() return num_submissions and then doing: top_users = User.objects.filter(problem_user=False).order_by('num_submissions')[:3] but this fails, as do all the other things I've tried. Can I actually do it using a smart database query? Or should I just do something more hacky in the views file?

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  • Python - react to custom keyboard interrupt

    - by flixic
    Hello. I am writing python chatbot that displays output through console. Every half second it asks server for updates, and responds to message. In the console I can see chat log. This is sufficient in most cases, however, sometimes I want to interrupt normal workflow and write custom chat answer myself. I would love to be able to press a button (or combination) that would switch to "custom reply mode". What is the best way to do that, or achieve similar result? Thanks a lot!

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  • Can I remove a RAR file's (known) password without recompressing the archive?

    - by Abluescarab
    Long title. Anyway, I haven't been able to find an answer to this question. I know the password to the RAR file, I locked it myself, but now all I want to do is remove the password because it's too much of a pain in the butt to type it in every time. Is there a way to do this in WinRAR or an equivalent program? The only thing I knew to do was to extract it, then create a new RAR without the password. It's not a life-or-death issue, but it would be nice to know. Thanks for your time! EDIT: I just saw a bunch of related questions that appear to ask the same thing. The only solution I saw was using a DOS command to yadda yadda yadda. Here it is: How to remove password protection from compressed files Is there an easier way? Thanks again!

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  • subversion 1.6.x losing changes on check-in

    - by Bernard
    I'm trying to figure out if this is a known issue with SVN 1.6.x Developer A modifies a file and commits it. Developer B modifies the same file. Tries to commit it and gets told local copy out of date so does an update and then a commit. However the changes from Developer A are lost so the resulting file only contains the version that Developer B checked in. We can see this in the logs. It seems to happen when the same file is modified but in different places. Anyone else experienced this? We've had it happen 4 or 5 times in the past few weeks and we've lost a half day or so each time trying to figure out what's been lost, etc. We're starting to lose confidence in SVN. Should we be thinking of moving to GIT or Mecurial? Would that sort out this problem?

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  • How do I learn algorithms?

    - by Panthe
    Brief History: Just graduated high school, learned a bit of python and C++, have no friends with any helpful computer knowledge at all. Out of anyone i met in my school years I was probably the biggest nerd, but no one really knew. I consider my self to have a vast amount of knowledge on computers and tech then the average person. built/fixed tons of computers, and ability to troubleshoot pretty much any problem I came across. Now that high school is over, Ive really been thinking about my career. Loving, living computers for the past 15 years of my life I decided to take my ability's and try to learn computer programming, why I didn't start earlier I don't know, seems to be big mistake on my part... Doing some research I concluded that Python was the first programming language I should learn, since it was high level and easier to understand then C++ and Java. I also knew that to become good at what I did I needed to know more then just 2 or 3 languages, which didn't seem like a big problem considering once I learned the way Python worked, mainly syntax changed, and the rest would come naturally. I watched a couple of youtube videos, downloaded some book pdf's and snooped around from some tutorials here and there to get the hang of what to do. A two solid weeks had passed of trying to understand the syntax, create small programs that used the basic functions and understanding how it worked, I think i have got the hang of it. It breaks down into what ive been dealing with all this time (although i kinda knew) is that, input,output, loops, functions and other things derived from 0's and 1's storing data and recalling it, ect. (A VERY BASIC IDEA). Ive been able to create small programs, Hangman, file storing, temperature conversion, Caeser Cipher decode/encoding, Fibonacci Sequence and more, which i can create and understand how each work. Being 2 weeks into this, I have learned alot. Nothing at all compared to what i should be lear ning in the years to come if i get a grip on what I'm doing. While doing these programs I wont stop untill I've done doing a practice problem on a book, which embarresing enough will take me a couple hour depending on the complexity of it. I absolutly will not put aside the challenge until its complete, WHICH CAN BE EXTREMELY DRAINING, ive tried most problems without cheating and reached success, which makes me feel extremely proud of my self after completing something after much trial and error. After all this I have met the demon, alogrithm's which seem to be key to effiecent code. I cant seem to rap my head around some of the computer codes people put out there using numbers, and sometimes even basic functions, I have been able to understand them after a while but i know there are alot more complex things to come, considering my self smart, functions that require complex codes, actually hurt my brain. NOTHING EVER IN LIFE HURT MY BRAIN....... not even math classes in highschool, trying to understand some of the stuff people put out there makes me feel like i have a mental disadvantage lol... i still walk forward though, crossing my fingers that the understanding will come with time. Sorry if is this is long i just wish someone takes all these things into consideration when answering my question. even through all these downsides im still pushing through and continuing to try and get good at this, i know reading these tutorials wont make me any good unless i can become creative and make my own, understand other peoples programs, so this leads me to the simple question i could have asked in the beginning..... WHERE IN THE WORLD DO I START ? Ive been trying to find out how to understand some of the open source projects, how i can work with experianced coders to learn from them and help them, but i dont think thats even possible by the way how far people's knowledge is compared to me, i have no freinds who i can learn from, can someone help me and guide me into the right direction.. i have a huge motivation to get good at coding, anything information would be extremely helpful

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  • Properly releasing UITableViewController and UITableView directly added to a UIViewController

    - by JK
    I have a UIViewController (parentVC) to which I add a UITableViewController as follows (it is not pushed since the tableview only occupies about half the screen): tableVC = [[SmallTableVC alloc] initWithStyle:UITableViewStylePlain]; [self.view addSubview:tableVC.tableView]; In dealloc, I add [tableVC release]; Using instruments, I can see that the tableVC is indeed fully released when parentVC released, which is good, but I am not sure why as I thought that the UITableView of tableVC would have a retain count of 2 (1 for retention by tableVC and 1 for retention by parentVC). My intuition was that an additional [tableVC.tableView release] would be required, but adding it crashes the app. Why is tableVC released properly by the current code (if indeed it actually is)? Does a UITableViewController not retain its tableView? Thanks.

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  • Contents after &amp; cannot be retrieved by xml parsing in iphone?

    - by Warrior
    I am new to iphone development.I am parsing a You tube rss feed to display its content in the table view. While retrieving the content of link tag, i am able to retrieve only half of the url and the string after & cannot be retrieved. I want to retrieve the full url so that i can use the url to load in a webview. How can i retrieve the full url ? Please help me out.The parsing is done same as Lazy tables . The orginal url is "http:www.youtube.xxxxxxxx&amp;xxxxxgdata"; The retrieved Url is "http:www.youtube.xxxxxxxx" Thanks.

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  • Cisco ASA 5505 inside interface multiple ip addresses

    - by Oneiroi
    I have an issue this morning where I want to be able to assign multiple ip addresses to the inside interface to facilitate an ip range migration for an office. Namely from a 192.168.1.x range to the new range, with the minimum of interruption for those working in the office. (New DHCP leases will use the new range, whilst those still on the 192.168.1.x range can continue to work until their lease is renewed). However I can not for the life of me figure out how to achieve this, trying to create multiple interfaces for the job leads to complaints about the license only allowing 2 active interfaces. Any suggestions? thanks in advance.

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  • Mail being sent as root on Ubuntu 14.04

    - by Benjamin Allison
    I'm really struggling with this. I'm trying to set up this server to send mail using Gmail's SMTP. Google keeps bouncing the messages, saying that that Authentication is required: smtp.gmail.com[74.125.196.109]:25: 530-5.5.1 Authentication Required. Learn more at smtp.gmail.com[74.125.196.109]:25: 530 5.5.1 http://support.google.com/mail/bin/answer.py?answer=14257 But it seems my server is trying to send mail as [email protected]. I'm baffled. Here's what I've done so far: Updated mail.cf relayhost = [smtp.gmail.com]:587 smtp_sasl_auth_enable = yes smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd smtp_sasl_security_options = noanonymous smtp_tls_CAfile = /etc/postfix/cacert.pem smtp_use_tls = yes Created /etc/postfix/sasl_passwd: [smtp.gmail.com]:587 [email protected]:password Then did the following: sudo chmod 400 /etc/postfix/sasl_passwd sudo postmap /etc/postfix/sasl_passwd cat /etc/ssl/certs/Thawte_Premium_Server_CA.pem | sudo tee -a /etc/postfix/cacert.pem service postfix restart I can't for the life me get a mail message to send, or change the default mail user from [email protected] to [email protected] (FWIW, I'm using Google Apps, that's why it's not a .gmail address).

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  • Best Practice: Migrating Email Boxes (maildir format)

    - by GruffTech
    So here's the situation. I've got about 20,000 maildir email accounts chewing up a several hundred GB of space on our email server. Maildir by nature keeps thousands of tiny a** little files, instead of one .mbox file or the like... So i need to migrate all of these several millions of files from one server to the other, for both space and life-cycle reasons. the conventional methods i would use all work just fine. rsync is the option that comes immediately to mind, however i wanted to see if there are any other "better" options out there. Rsync not handling multi-threaded transfers in this situation sucks because it never actually gets up to speed and saturates my network connection, because of this the transfer from one server to another will take hours beyond hours, when it shouldn't really take more then one or two. I know this is highly opinionated and subjective and will therefore be marked community wiki.

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  • Network throughput issue (ARP-related)

    - by Joel Coel
    The small college where I work is having some very strange network issues. I'm looking for any advice or ideas here. We were fine over the summer, but the trouble began few days after students returned to campus in force for the fall term. Symptoms The main symptom is that internet access will work, but it's very slow... often to the point of timeouts. As an example, a typical result from Speedtest.net will return .4Mbps download, but allow 3 to 8 Mbps upload speed. Lesser symptoms may include severely limited performance transferring data to and from our file server, or even in some cases the inability to log in to the computer (cannot reach the domain controller). The issue crosses multiple vlans, and has effected devices on nearly every vlan we operate. The issue does not impact all machines on the network. An unaffected machine will typically see at least 11Mbps download from speedtest.net, and perhaps much more depending on larger campus traffic patterns at the time. There is one variation on the larger issue. We have one vlan where users were unable to log into nearly all of the machines at all. IT staff would log in using a local administrator account (or in some cases cached credentials), and from there a release/renew or pinging the gateway would allow the machine to work... for a while. Complicating this issue is that this vlan covers our computer labs, which use software called Deep Freeze to completely reset the hard drives after a reboot. It could just the same issue manifesting differently because of stale data on machines that have not permanently altered low-level info for weeks. We were able to solve this, however, by creating a new vlan and moving the labs over to the new vlan wholesale. Instigations Eventually we noticed that the effected machines all had recent dhcp leases. We can predict when a machine will become "slow" by watching when a dhcp lease comes up for renewal. We played with setting the lease time very short for a test vlan, but all that did was remove our ability to predict when the machine would become slow. Machines with static IPs have pretty much always worked normally. Manually releasing/renewing an address will never cause a machine to become slow. In fact, in some cases this process has fixed a machine in that state. Most of the time, though, it doesn't help. We also noticed that mobile machines like laptops are likely to become slow when they cross to new vlans. Wireless on campus is divided up into "zones", where each zone maps to a small set of buildings. Moving to a new building can place you in a zone, thereby causing you to get a new address. A machine resuming from sleep mode is also very likely to be slow. Mitigations Sometimes, but not always, clearing the arp cache on an effected machine will allow it to work normally again. As already mentioned, releasing/renewing a local machine's IP address can fix that machine, but it's not guaranteed. Pinging the default gateway can also sometimes help with a slow machine. What seems to help most to mitigate the issue is clearing the arp cache on our core layer-3 switch. This switch is used for our dhcp system as the default gateway on all vlans, and it handles inter-vlan routing. The model is a 3Com 4900SX. To try to mitigate the issue, we have the cache timeout set on the switch all the way down to the lowest possible time, but it hasn't helped. I also put together a script that runs every few minutes to automatically connect to the switch and reset the cache. Unfortunately, this does not always work, and can even cause some machines to end up in the slow state for a short time (though these seem to correct themselves after a few minutes). We currently have a scheduled job that runs every 10 minutes to force the core switch to clear it's ARP cache, but this is far from perfect or desirable. Reproduction We now have a test machine that we can force into the slow state at will. It is connected to a switch with ports set up for each of our vlans. We make the machine slow by connecting to different vlans, and after a new connection or two it will be slow. It's also worth noting in this section that this has happened before at the start of prior terms, but in the past the problem has gone away on it's own after a few days. It solved itself before we had a chance to do much diagnostic work... hence why we've allowed it to drag so long into the term this time 'round; the expectation was this would be a short-lived situation. Other Factors It's worth mentioning that we have had about half a dozen switches just outright fail over the last year. These are mainly 2003/2004-era 3Coms (mostly 4200's) that were all put in at about the same time. They should still be covered under warranty, buy HP has made getting service somewhat difficult. Mostly in power supplies that have failed, but in a couple cases we have used a power supply from a switch with a failed mainboard to bring a switch with a failed power supply back to life. We do have UPS devices on all but three of four switches now, but that was not the case when I started two and a half years ago. Severe budget constraints (we were on the Dept. of Ed's financially challenged institutions list a couple years back) have forced me to look to the likes of Netgear and TrendNet for replacements, but so far these low-end models seem to be holding their own. It's also worth mentioning that the big change on our network this summer was migrating from a single cross-campus wireless SSID to the zoned approach mentioned earlier. I don't think this is the source of the issue, as like I've said: we've seen this before. However, it's possible this is exacerbating the issue, and may be much of the reason it's been so hard to isolate. Diagnosis At first it seemed clear to us, given the timing and persistent nature of the problem, that the source of the issue was an infected (or malicious) student machine doing ARP cache poisoning. However, repeated attempts to isolate the source have failed. Those attempts include numerous wireshark packet traces, and even taking entire buildings offline for brief periods. We have not been able even to find a smoking gun bad ARP entry. My current best guess is an overloaded or failing core switch, but I'm not sure on how to test for this, and the cost of replacing it blindly is steep. Again, any ideas appreciated.

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