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• How to prioritize tasks when you have multiple programming projects running in parallel?

  - by Vinko Vrsalovic

  Say you have 5 customers, you develop 2 or 3 different projects for each. Each project has Xi tasks. Each project takes from 2 to 10 man weeks. Given that there are few resources, it is desired to minimize the management overhead. Two questions in this scenario: What tools would you use to prioritize the tasks and track their completion, while tending to minimize the overhead? What criteria would you take into consideration to determine which task to assign to the next available resource given that the primary objective is to increase throughput (more projects finished per time unit, this objective conflicts with starting one project and finishing it and then moving on to the next)? Ideas, management techniques, algorithms are welcome

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• How to find optimal path visit every node with parallel workers complicated by dynamic edge costs?

  - by Aaron Anodide

  Say you have an acyclic directed graph with weighted edges and create N workers. My goal is to calculate the optimal way those workers can traverse the entire graph in parralel. However, edge costs may change along the way. Example: A -1-> B A -2-> C B -3-> C (if A has already been visited) B -5-> C (if A has not already been visited) Does what I describe lend itself to a standard algorithmic approach, or alternately can someone suggest if I'm looking at this in an inherently flawed way (i have an intuition I might be)?

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• Why is lowlatency kernel not being updated in parallel with the generic kernel?

  - by FlabbergastedPickle

  All, Any idea when we'll see updates to the lowlatency version of the Ubuntu 12.04 kernel? It is still stuck at 3.2.0.23 whereas the generic kernel is already several updates ahead of it at a version 3.2.0.25? NB: I am using a 64-bit version but I don't think this is limited to the 64-bit kernels alone but rather affects both 32-bit and 64-bit builds. Please do correct me if I am wrong about this.

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• What causes a switch port to receive data not destined for it?

  - by user1693454

  We are having an intermittent fault which is effecting one of our control systems on one of our HP Procurve switches. For some reason, this PLC (10mbit port - 192.168.6.56) which is attached directly to the HP Switch intermittantly start's receiving data which is not destined for it. The data is being sent from a Thecus NAS with latest firmware (192.168.6.218) to a physical IBM Server running Win2003R2 and SAP (192.168.6.225). The problem does not just send to this server, it has been to other physical servers in the past too, but always from the Thecus NAS. I am using a monitor port to wireshark what is going in/out of the PLC - normally there would be about 1mb in/out per 2 or 3 minutes - only a server asking the state of the coils. When the problem occurs, there is a flood of data being put onto the PLC line - in this captured instance, about 67mb in less than a minute. Due to this, there is no way that the PLC can be queried as the port is effectively DOSed, in turn killing part of our factory. I know that having Production on the same vlan as IT is not a good idea - I agree, however it cannot be changed at the moment (will have to wait 3 months), as well as the problem has only started happening in the last 3 months. Here is a screen cap of one of the packets being sent from the Thecus NAS which was captured from the PLC port on the HP Switch: And there are over 700 of these in this one 1024kb file. If anyone has any idea on what could be going on, some help would be greatly appreciated. If you need to know anything more, let me know! Cheers!

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• Shows how to use the new Tasks namespace to download multiple documents in parallel.

  In C# 4.0, Task parallelism is the lowest-level approach to parallelization with PFX. The classes for working at this level are defined in the System.Threading.Tasks namespace.  read moreBy Peter BrombergDid you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• Can multiple windows users connect to a Mac Mini OS X Server and run applications in parallel?

  - by ilight

  I want to validate the current situation :- I have multiple users who have to use designing applications like Adobe Photoshop, Illustrator etc and maybe some Mac specific applications like iWork and they need to be working on the applications in parallel. Can I setup a Mac Mini OS X Server and create separate user accounts and give to these users so that they can remote login to the OS X Server simultaneously from their Windows machines and use any application they want? In crux, can they share the server resources and applications from their windows machines?

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• Perl cron job stays running

  - by Dylan

  I'm currently using a cron job to have a Perl script that tells my Arduino to cycle my aquaponics system and all is well, except the Perl script doesn't die as intended. Here is my cron job: */15 * * * * /home/dburke/scripts/hal/bin/main.pl cycle And below is my Perl script: #!/usr/bin/perl -w # Sample Perl script to transmit number # to Arduino then listen for the Arduino # to echo it back use strict; use Device::SerialPort; use Switch; use Time::HiRes qw ( alarm ); $|++; # Set up the serial port # 19200, 81N on the USB ftdi driver my $device = '/dev/arduino0'; # Tomoc has to use a different tty for testing #$device = '/dev/ttyS0'; my $port = new Device::SerialPort ($device) or die('Unable to open connection to device');; $port->databits(8); $port->baudrate(19200); $port->parity("none"); $port->stopbits(1); my $lastChoice = ' '; my $pid = fork(); my $signalOut; my $args = shift(@ARGV); # Parent must wait for child to exit before exiting itself on CTRL+C $SIG{'INT'} = sub { waitpid($pid,0) if $pid != 0; exit(0); }; # What child process should do if($pid == 0) { # Poll to see if any data is coming in print "\nListening...\n\n"; while (1) { my $incmsg = $port->lookfor(9); # If we get data, then print it if ($incmsg) { print "\nFrom arduino: " . $incmsg . "\n\n"; } } } # What parent process should do else { if ($args eq "cycle") { my $stop = 0; sleep(1); $SIG{ALRM} = sub { print "Expecting plant bed to be full; please check.\n"; $signalOut = $port->write('2'); # Signal to set pin 3 low print "Sent cmd: 2\n"; $stop = 1; }; $signalOut = $port->write('1'); # Signal to arduino to set pin 3 High print "Sent cmd: 1\n"; print "Waiting for plant bed to fill...\n"; alarm (420); while ($stop == 0) { sleep(2); } die "Done."; } else { sleep(1); my $choice = ' '; print "Please pick an option you'd like to use:\n"; while(1) { print " [1] Cycle [2] Relay OFF [3] Relay ON [4] Config [$lastChoice]: "; chomp($choice = <STDIN>); switch ($choice) { case /1/ { $SIG{ALRM} = sub { print "Expecting plant bed to be full; please check.\n"; $signalOut = $port->write('2'); # Signal to set pin 3 low print "Sent cmd: 2\n"; }; $signalOut = $port->write('1'); # Signal to arduino to set pin 3 High print "Sent cmd: 1\n"; print "Waiting for plant bed to fill...\n"; alarm (420); $lastChoice = $choice; } case /2/ { $signalOut = $port->write('2'); # Signal to set pin 3 low print "Sent cmd: 2"; $lastChoice = $choice; } case /3/ { $signalOut = $port->write('1'); # Signal to arduino to set pin 3 High print "Sent cmd: 1"; $lastChoice = $choice; } case /4/ { print "There is no configuration available yet. Please stab the developer."; } else { print "Please select a valid option.\n\n"; } } } } } Why wouldn't it die from the statement die "Done.";? It runs fine from the command line and also interprets the 'cycle' argument fine. When it runs in cron it runs fine, however, the process never dies and while each process doesn't continue to cycle the system it does seem to be looping in some way due to the fact that it ups my system load very quickly. If you'd like more information, just ask. EDIT: I have changed to code to: #!/usr/bin/perl -w # Sample Perl script to transmit number # to Arduino then listen for the Arduino # to echo it back use strict; use Device::SerialPort; use Switch; use Time::HiRes qw ( alarm ); $|++; # Set up the serial port # 19200, 81N on the USB ftdi driver my $device = '/dev/arduino0'; # Tomoc has to use a different tty for testing #$device = '/dev/ttyS0'; my $port = new Device::SerialPort ($device) or die('Unable to open connection to device');; $port->databits(8); $port->baudrate(19200); $port->parity("none"); $port->stopbits(1); my $lastChoice = ' '; my $signalOut; my $args = shift(@ARGV); # Parent must wait for child to exit before exiting itself on CTRL+C if ($args eq "cycle") { open (LOG, '>>log.txt'); print LOG "Cycle started.\n"; my $stop = 0; sleep(2); $SIG{ALRM} = sub { print "Expecting plant bed to be full; please check.\n"; $signalOut = $port->write('2'); # Signal to set pin 3 low print "Sent cmd: 2\n"; $stop = 1; }; $signalOut = $port->write('1'); # Signal to arduino to set pin 3 High print "Sent cmd: 1\n"; print "Waiting for plant bed to fill...\n"; print LOG "Alarm is being set.\n"; alarm (420); print LOG "Alarm is set.\n"; while ($stop == 0) { print LOG "In while-sleep loop.\n"; sleep(2); } print LOG "The loop has been escaped.\n"; die "Done."; print LOG "No one should ever see this."; } else { my $pid = fork(); $SIG{'INT'} = sub { waitpid($pid,0) if $pid != 0; exit(0); }; # What child process should do if($pid == 0) { # Poll to see if any data is coming in print "\nListening...\n\n"; while (1) { my $incmsg = $port->lookfor(9); # If we get data, then print it if ($incmsg) { print "\nFrom arduino: " . $incmsg . "\n\n"; } } } # What parent process should do else { sleep(1); my $choice = ' '; print "Please pick an option you'd like to use:\n"; while(1) { print " [1] Cycle [2] Relay OFF [3] Relay ON [4] Config [$lastChoice]: "; chomp($choice = <STDIN>); switch ($choice) { case /1/ { $SIG{ALRM} = sub { print "Expecting plant bed to be full; please check.\n"; $signalOut = $port->write('2'); # Signal to set pin 3 low print "Sent cmd: 2\n"; }; $signalOut = $port->write('1'); # Signal to arduino to set pin 3 High print "Sent cmd: 1\n"; print "Waiting for plant bed to fill...\n"; alarm (420); $lastChoice = $choice; } case /2/ { $signalOut = $port->write('2'); # Signal to set pin 3 low print "Sent cmd: 2"; $lastChoice = $choice; } case /3/ { $signalOut = $port->write('1'); # Signal to arduino to set pin 3 High print "Sent cmd: 1"; $lastChoice = $choice; } case /4/ { print "There is no configuration available yet. Please stab the developer."; } else { print "Please select a valid option.\n\n"; } } } } }

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• Java Socket Closes After Connection?

  - by Matthew

  Why does this port/socket close once a connection has been made by a client? package app; import java.io.*; import java.net.*; public class socketServer { public static void main(String[] args) { int port = 3333; boolean socketBindedToPort = false; try { ServerSocket ServerSocketPort = new ServerSocket(port); System.out.println("SocketServer Set Up on Port: " + port); socketBindedToPort = true; if(socketBindedToPort == true) { Socket clientSocket = null; try { clientSocket = ServerSocketPort.accept();//This method blocks until a socket connection has been made to this port. System.out.println("Waiting for client connection on port:" + port); /** THE CLIENT HAS MADE A CONNECTION **/ System.out.println("CLIENT IS CONENCTED"); } catch (IOException e) { System.out.println("Accept failed: " + port); System.exit(-1); } } else { System.out.println("Socket did not bind to the port:" + port); } } catch(IOException e) { System.out.println("Could not listen on port: " + port); System.exit(-1); } } }

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• Are spurious TCP connections on port 53 a problem?

  - by Darren Greaves

  I run a server which amongst other things uses tinydns for DNS and axfrdns for handling transfer requests from our secondary DNS (another system). I understand that tinydns uses port 53 on UDP and axfrdns uses port 53 on TCP. I've configured axfrdns to only allow connections from my agreed secondary host. I run logcheck to monitor my logs and every day I see spurious connections on port 53 (TCP) from seemingly random hosts. They usually turn out to be from ADSL connections. My question is; are these innocent requests or a security risk? I am happy to block repeat offenders using iptables but don't want to block innocent users of one of the websites I host. Thanks, Darren.

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• Using the option port on my Watchguard Firebox as a 2nd gateway exit point?

  - by Donovan

  I'm working on a network project in witch I have to design our network to provide two different exit points. The points are differentiated by the path through the corporate network. One of them travels through some monitoring hardware the other does not. We have a Watchguard Firebox in use as our gateway. Currently the network side provides the unmonitored exit point. I was wondering if i hooked the option port to our lan at a point that would force traffic through the monitored path, would it cause any problems? Access to the unmonitored gateway port would be restricted by ip. That would force all others not authorized to point to the monitored gateway port. I thought with the above design i might be able to get away with not having to buy another firebox to achieve the design I want. Thanks, D

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• Can I set up a COM Port that Connects via TCP/IP?

  - by Kristopher Johnson

  I have an RS232 device connected to a Digi PortServer on my network. I can telnet to the Digi's IP and port number to communicate with that RS232 device. I have a Windows application that knows how to talk to the device, but it wants to connect directly to an RS232 port. So, my question: Is there some way to set up a COM port so that when this application connects to it, it goes through the network to the Digi to communicate with the device? I have run across the utility TCP-Com, which seems like it might be a solution. Is this the best option?

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• Linksys EA3500 : use WAN port as WAN + LAN possible?

  - by Dough

  I'm waiting for deliver of a Linksys EA3500 router. I was wondering if it was possible to get the WAN port act as normal WAN port (Internet IP) + LAN switch ? My problem is that my Internet box is in a room with NAS and PC, and the router will be in another room with TV, PS3 and PC. The Internet box have a 4 port Gigabit switch so one cable will plug from there to the router's WAN in the other room. The router will get the Internet IP from the Internet box, but will it be possible to have private network through this link too ? I could have a first network between the Internet box and the router, and another network form router and devices but that will do double NAT for nothing... Thanks for reading me and your help !

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• How do http proxies determine https traffic with a single port?

  - by badunk

  If a proxy receives the tcp packet, then the destination ip address and port are that of the proxy. In that case, I imagine the only way a proxy can still resolve the intended destination is either through routing the source ip address/port or through the host field in the http header. Is this correct? In both Fiddler and Charles http proxies, I noticed that the tool accepts both http and https connections through a single port that you can specify. What do these tools do to tell the difference between the two types of connections?

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• Hosting a web site at home: ISP Blocking port 80?

  - by tombull89

  Hello, I presume this is a better place to put this rather than server fault. I'm interested in setting up a small site to host at home as a "proof of concept" exercise, i.e. to prrove that I know how to do it. I've got a (virtual) server 2003 machine with a site on it, all configured with port forwarding through to 80 on my server. I have a Belkin F5D7634 which I have put my DYNDNS details in but when I try to go to my DYNDNS address it comes up with the page cannot be displayed. My ISP is Carphone Warehouse/AOL and I've been unable to find any information if they block port 80. If they do, can anybody reccomend a home provider that does not block port 80? Regards, Tom.

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• How do I make a privileged port non-privileged in Redhat 5?

  - by Jason Thompson

  So I have a RedHat 5 box that I'm wanting to run an application that I wrote that implements SLP. SLP uses port 427 for answering service queries. My understanding is that ports below 1024 are "privileged" and thus cannot be bound to by anyone that's not root. I cannot run this application as root as it is launched via tomcat. One creative solution I really like was simply writing an iptables rule to route the privileged port to a non-privileged. In my proof of concept tests, this works wonderfully. Unfortunately, it would be greatly (and understandably) desired by the powers if my application did not require screwing around with iptables upon installation. So I heard a rumor and cannot find anything to verify this that there was some sort of command or parameter that could be set to make any port I want be non-privileged. Is this true? If so, how is this done? Thanks!

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• How to access remotly to a mysql server?

  - by ÉricP

  Hi, I'm trying to access my remote mysql server from my own computer. I uncommented: bind-address = 80.10.65.45 I added 80.10.65.45 as a server in privilege root 80.10.65.45 yes ALL PRIVILEGES yes I'm using Sequel Pro on MacosX to connect via SSH here is the debug log: debug1: Authentication succeeded (password). debug1: Local connections to LOCALHOST:58517 forwarded to remote address 127.0.0.1:3306 debug1: Local forwarding listening on ::1 port 58517. debug1: channel 0: new [port listener] debug1: Local forwarding listening on 127.0.0.1 port 58517. debug1: channel 1: new [port listener] debug1: Entering interactive session. debug1: Connection to port 58517 forwarding to 127.0.0.1 port 3306 requested. debug1: channel 2: new [direct-tcpip] channel 2: open failed: connect failed: Connection refused debug1: channel 2: free: direct-tcpip: listening port 58517 for 127.0.0.1 port 3306, connect from 127.0.0.1 port 58519, nchannels 3

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• Emulate a USB port as a USB flash drive?

  - by Wilco

  Does anyone know of any software that can emulate a USB flash drive through an available USB port in OS X? Perhaps some way to map a directory to a USB port that could then be connected to another device that supports reading USB storage devices? I'd love to connect my laptop to my car's USB port and access files as if it were a USB drive. I know about the target disk mode with firewire (not sure if this is also supported over USB), but I was hoping for something that doesn't require booting outside of the OS (I want to retain use of the machine). Any ideas?

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• outlook iptables configuration [update]

  - by mediaexpert

  I've a Debian mail server, but only the outlook users can't be able to download the emails. I've seen a lot of post about some kind of forwarding port configuration, I've tried some commands, but I don't be able to solve this problem, please help me. [LAST UPDATE] I find a lot of TIME WAIT on ipv6 netstat tcp6 0 0 my.mailserver.it:imap2 200-62-245-188.ip2:17060 TIME_WAIT - below some config files: pop3d I think the problem was here ##NAME: POP3AUTH:1 # # To advertise the SASL capability, per RFC 2449, uncomment the POP3AUTH # variable: # # POP3AUTH="LOGIN" # # If you have configured the CRAM-MD5, CRAM-SHA1 or CRAM-SHA256, set POP3AUTH # to something like this: # # POP3AUTH="LOGIN CRAM-MD5 CRAM-SHA1" POP3AUTH="" ##NAME: POP3AUTH_ORIG:1 # # For use by webadmin POP3AUTH_ORIG="PLAIN LOGIN CRAM-MD5 CRAM-SHA1 CRAM-SHA256" ##NAME: POP3AUTH_TLS:1 # # To also advertise SASL PLAIN if SSL is enabled, uncomment the # POP3AUTH_TLS environment variable: # # POP3AUTH_TLS="LOGIN PLAIN" POP3_TLS_REQUIRED = 0 POP3AUTH_TLS="" ##NAME: POP3AUTH_TLS_ORIG:0 # # For use by webadmin POP3AUTH_TLS_ORIG="LOGIN PLAIN" ##NAME: POP3_PROXY:0 # # Enable proxying. See README.proxy # # For use by webadmin POP3AUTH_TLS_ORIG="LOGIN PLAIN" ##NAME: POP3_PROXY:0 # # Enable proxying. See README.proxy POP3_PROXY=0 ##NAME: PROXY_HOSTNAME:0 # # Override value from gethostname() when checking if a proxy connection is # required. # PROXY_HOSTNAME= ##NAME: PORT:1 ##NAME: PROXY_HOSTNAME:0 # # Override value from gethostname() when checking if a proxy connection is # required. # PROXY_HOSTNAME= ##NAME: PORT:1 # # Port to listen on for connections. The default is port 110. # # Multiple port numbers can be separated by commas. When multiple port # numbers are used it is possibly to select a specific IP address for a # given port as "ip.port". For example, "127.0.0.1.900,192.68.0.1.900" # accepts connections on port 900 on IP addresses 127.0.0.1 and 192.68.0.1 # The ADDRESS setting is a default for ports that do not have a specified # IP address. # Port to listen on for connections. The default is port 110. # # Multiple port numbers can be separated by commas. When multiple port # numbers are used it is possibly to select a specific IP address for a # given port as "ip.port". For example, "127.0.0.1.900,192.68.0.1.900" # accepts connections on port 900 on IP addresses 127.0.0.1 and 192.68.0.1 # The ADDRESS setting is a default for ports that do not have a specified # IP address. PORT=110 ##NAME: ADDRESS:0 # # IP address to listen on. 0 means all IP addresses. ADDRESS=0 ##NAME: TCPDOPTS:0 # ##NAME: ADDRESS:0 # # IP address to listen on. 0 means all IP addresses. ADDRESS=0 ##NAME: TCPDOPTS:0 # # Other couriertcpd(1) options. The following defaults should be fine. # TCPDOPTS="-nodnslookup -noidentlookup" ##NAME: LOGGEROPTS:0 # # courierlogger(1) options. # LOGGEROPTS="-name=pop3d" ##NAME: DEFDOMAIN:0 # # Optional default domain. If the username does not contain the # first character of DEFDOMAIN, then it is appended to the username. # If DEFDOMAIN and DOMAINSEP are both set, then DEFDOMAIN is appended # only if the username does not contain any character from DOMAINSEP. # You can set different default domains based on the the interface IP # address using the -access and -accesslocal options of couriertcpd(1). DEFDOMAIN="@interzone.it" ##NAME: POP3DSTART:0 # # POP3DSTART is not referenced anywhere in the standard Courier programs # or scripts. Rather, this is a convenient flag to be read by your system # startup script in /etc/rc.d, like this: # # . /etc/courier/pop3d DEFDOMAIN="@mydomain.com" ##NAME: POP3DSTART:0 # # POP3DSTART is not referenced anywhere in the standard Courier programs # or scripts. Rather, this is a convenient flag to be read by your system # startup script in /etc/rc.d, like this: # # . /etc/courier/pop3d # case x$POP3DSTART in # x[yY]*) # /usr/lib/courier/pop3d.rc start # ;; # esac # # The default setting is going to be NO, until Courier is shipped by default # with enough platforms so that people get annoyed with having to flip it to # YES every time. # x[yY]*) # /usr/lib/courier/pop3d.rc start # ;; # esac # # The default setting is going to be NO, until Courier is shipped by default # with enough platforms so that people get annoyed with having to flip it to # YES every time. POP3DSTART=YES ##NAME: MAILDIRPATH:0 # # MAILDIRPATH - directory name of the maildir directory. # MAILDIRPATH=.maildir iptables Chain INPUT (policy DROP 20 packets, 1016 bytes) pkts bytes target prot opt in out source destination 60833 16M ACCEPT tcp -- eth0 * 0.0.0.0/0 0.0.0.0/0 tcp dpt:143 state NEW,ESTABLISHED 18970 971K ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp spts:1024:65535 dpt:110 state NEW,ESTABLISHED Chain FORWARD (policy DROP 0 packets, 0 bytes) pkts bytes target prot opt in out source destination 0 0 ACCEPT tcp -- * * 192.168.0.0/24 0.0.0.0/0 tcp dpt:110 0 0 ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED 0 0 ACCEPT tcp -- * * 192.168.1.0/24 0.0.0.0/0 tcp dpt:110 0 0 ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED 0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:25 0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:110 pop3d.cnf RANDFILE = /usr/lib...pop3d.rand [req] default_bits = 1024 encrypt_key = yes distinguidhed_name = req_dn x509_extensions = cert_type prompt = no [req_dn] C=US ST=NY L= New York O=Courier Mail Server OU=Automatically-generated POP3 SSL key CN=localhost [email protected] [cert_type] nsCertType = server

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• Multiple SSL domains on the same IP address and same port?

  - by John

  This is a Canonical Question about Hosting multiple SSL websites on the same IP. I was under the impression that each SSL Certificate required it's own unique IP Address/Port combination. But the answer to a previous question I posted is at odds with this claim. Using information from that Question, I was able to get multiple SSL certificates to work on the same IP address and on port 443. I am very confused as to why this works given the assumption above and reinforced by others that each SSL domain website on the same server requires its own IP/Port. I am suspicious that I did something wrong. Can multiple SSL Certificates be used this way?

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• How to run multiple Nginx instances on different port...

  - by Edvinas

  Hi, I would like to have several Nginx instances running on my server on separate ports (for example one user runs Nginx on port 2345, and another user on port 2346). So far, I have been successful in compiling and running the server on their designated ports. However, I am running into a weird issue: If i visit domain1.com:2345 or domain2.com:2346 I get the correct (200) response but if I visit domain1.com or domain2.com (without specifying the port) I get no response at all. Any help/clues in figuring out how to set this up would be highly appreciated.

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• How to Reuse Your Old Wi-Fi Router as a Network Switch

  - by Jason Fitzpatrick

  Just because your old Wi-Fi router has been replaced by a newer model doesn’t mean it needs to gather dust in the closet. Read on as we show you how to take an old and underpowered Wi-Fi router and turn it into a respectable network switch (saving your $20 in the process). Image by mmgallan. Why Do I Want To Do This? Wi-Fi technology has changed significantly in the last ten years but Ethernet-based networking has changed very little. As such, a Wi-Fi router with 2006-era guts is lagging significantly behind current Wi-Fi router technology, but the Ethernet networking component of the device is just as useful as ever; aside from potentially being only 100Mbs instead of 1000Mbs capable (which for 99% of home applications is irrelevant) Ethernet is Ethernet. What does this matter to you, the consumer? It means that even though your old router doesn’t hack it for your Wi-Fi needs any longer the device is still a perfectly serviceable (and high quality) network switch. When do you need a network switch? Any time you want to share an Ethernet cable among multiple devices, you need a switch. For example, let’s say you have a single Ethernet wall jack behind your entertainment center. Unfortunately you have four devices that you want to link to your local network via hardline including your smart HDTV, DVR, Xbox, and a little Raspberry Pi running XBMC. Instead of spending $20-30 to purchase a brand new switch of comparable build quality to your old Wi-Fi router it makes financial sense (and is environmentally friendly) to invest five minutes of your time tweaking the settings on the old router to turn it from a Wi-Fi access point and routing tool into a network switch–perfect for dropping behind your entertainment center so that your DVR, Xbox, and media center computer can all share an Ethernet connection. What Do I Need? For this tutorial you’ll need a few things, all of which you likely have readily on hand or are free for download. To follow the basic portion of the tutorial, you’ll need the following: 1 Wi-Fi router with Ethernet ports 1 Computer with Ethernet jack 1 Ethernet cable For the advanced tutorial you’ll need all of those things, plus: 1 copy of DD-WRT firmware for your Wi-Fi router We’re conducting the experiment with a Linksys WRT54GL Wi-Fi router. The WRT54 series is one of the best selling Wi-Fi router series of all time and there’s a good chance a significant number of readers have one (or more) of them stuffed in an office closet. Even if you don’t have one of the WRT54 series routers, however, the principles we’re outlining here apply to all Wi-Fi routers; as long as your router administration panel allows the necessary changes you can follow right along with us. A quick note on the difference between the basic and advanced versions of this tutorial before we proceed. Your typical Wi-Fi router has 5 Ethernet ports on the back: 1 labeled “Internet”, “WAN”, or a variation thereof and intended to be connected to your DSL/Cable modem, and 4 labeled 1-4 intended to connect Ethernet devices like computers, printers, and game consoles directly to the Wi-Fi router. When you convert a Wi-Fi router to a switch, in most situations, you’ll lose two port as the “Internet” port cannot be used as a normal switch port and one of the switch ports becomes the input port for the Ethernet cable linking the switch to the main network. This means, referencing the diagram above, you’d lose the WAN port and LAN port 1, but retain LAN ports 2, 3, and 4 for use. If you only need to switch for 2-3 devices this may be satisfactory. However, for those of you that would prefer a more traditional switch setup where there is a dedicated WAN port and the rest of the ports are accessible, you’ll need to flash a third-party router firmware like the powerful DD-WRT onto your device. Doing so opens up the router to a greater degree of modification and allows you to assign the previously reserved WAN port to the switch, thus opening up LAN ports 1-4. Even if you don’t intend to use that extra port, DD-WRT offers you so many more options that it’s worth the extra few steps. Preparing Your Router for Life as a Switch Before we jump right in to shutting down the Wi-Fi functionality and repurposing your device as a network switch, there are a few important prep steps to attend to. First, you want to reset the router (if you just flashed a new firmware to your router, skip this step). Following the reset procedures for your particular router or go with what is known as the “Peacock Method” wherein you hold down the reset button for thirty seconds, unplug the router and wait (while still holding the reset button) for thirty seconds, and then plug it in while, again, continuing to hold down the rest button. Over the life of a router there are a variety of changes made, big and small, so it’s best to wipe them all back to the factory default before repurposing the router as a switch. Second, after resetting, we need to change the IP address of the device on the local network to an address which does not directly conflict with the new router. The typical default IP address for a home router is 192.168.1.1; if you ever need to get back into the administration panel of the router-turned-switch to check on things or make changes it will be a real hassle if the IP address of the device conflicts with the new home router. The simplest way to deal with this is to assign an address close to the actual router address but outside the range of addresses that your router will assign via the DHCP client; a good pick then is 192.168.1.2. Once the router is reset (or re-flashed) and has been assigned a new IP address, it’s time to configure it as a switch. Basic Router to Switch Configuration If you don’t want to (or need to) flash new firmware onto your device to open up that extra port, this is the section of the tutorial for you: we’ll cover how to take a stock router, our previously mentioned WRT54 series Linksys, and convert it to a switch. Hook the Wi-Fi router up to the network via one of the LAN ports (consider the WAN port as good as dead from this point forward, unless you start using the router in its traditional function again or later flash a more advanced firmware to the device, the port is officially retired at this point). Open the administration control panel via  web browser on a connected computer. Before we get started two things: first,  anything we don’t explicitly instruct you to change should be left in the default factory-reset setting as you find it, and two, change the settings in the order we list them as some settings can’t be changed after certain features are disabled. To start, let’s navigate to Setup ->Basic Setup. Here you need to change the following things: Local IP Address: [different than the primary router, e.g. 192.168.1.2] Subnet Mask: [same as the primary router, e.g. 255.255.255.0] DHCP Server: Disable Save with the “Save Settings” button and then navigate to Setup -> Advanced Routing: Operating Mode: Router This particular setting is very counterintuitive. The “Operating Mode” toggle tells the device whether or not it should enable the Network Address Translation (NAT)  feature. Because we’re turning a smart piece of networking hardware into a relatively dumb one, we don’t need this feature so we switch from Gateway mode (NAT on) to Router mode (NAT off). Our next stop is Wireless -> Basic Wireless Settings: Wireless SSID Broadcast: Disable Wireless Network Mode: Disabled After disabling the wireless we’re going to, again, do something counterintuitive. Navigate to Wireless -> Wireless Security and set the following parameters: Security Mode: WPA2 Personal WPA Algorithms: TKIP+AES WPA Shared Key: [select some random string of letters, numbers, and symbols like JF#d$di!Hdgio890] Now you may be asking yourself, why on Earth are we setting a rather secure Wi-Fi configuration on a Wi-Fi router we’re not going to use as a Wi-Fi node? On the off chance that something strange happens after, say, a power outage when your router-turned-switch cycles on and off a bunch of times and the Wi-Fi functionality is activated we don’t want to be running the Wi-Fi node wide open and granting unfettered access to your network. While the chances of this are next-to-nonexistent, it takes only a few seconds to apply the security measure so there’s little reason not to. Save your changes and navigate to Security ->Firewall. Uncheck everything but Filter Multicast Firewall Protect: Disable At this point you can save your changes again, review the changes you’ve made to ensure they all stuck, and then deploy your “new” switch wherever it is needed. Advanced Router to Switch Configuration For the advanced configuration, you’ll need a copy of DD-WRT installed on your router. Although doing so is an extra few steps, it gives you a lot more control over the process and liberates an extra port on the device. Hook the Wi-Fi router up to the network via one of the LAN ports (later you can switch the cable to the WAN port). Open the administration control panel via web browser on the connected computer. Navigate to the Setup -> Basic Setup tab to get started. In the Basic Setup tab, ensure the following settings are adjusted. The setting changes are not optional and are required to turn the Wi-Fi router into a switch. WAN Connection Type: Disabled Local IP Address: [different than the primary router, e.g. 192.168.1.2] Subnet Mask: [same as the primary router, e.g. 255.255.255.0] DHCP Server: Disable In addition to disabling the DHCP server, also uncheck all the DNSMasq boxes as the bottom of the DHCP sub-menu. If you want to activate the extra port (and why wouldn’t you), in the WAN port section: Assign WAN Port to Switch [X] At this point the router has become a switch and you have access to the WAN port so the LAN ports are all free. Since we’re already in the control panel, however, we might as well flip a few optional toggles that further lock down the switch and prevent something odd from happening. The optional settings are arranged via the menu you find them in. Remember to save your settings with the save button before moving onto a new tab. While still in the Setup -> Basic Setup menu, change the following: Gateway/Local DNS : [IP address of primary router, e.g. 192.168.1.1] NTP Client : Disable The next step is to turn off the radio completely (which not only kills the Wi-Fi but actually powers the physical radio chip off). Navigate to Wireless -> Advanced Settings -> Radio Time Restrictions: Radio Scheduling: Enable Select “Always Off” There’s no need to create a potential security problem by leaving the Wi-Fi radio on, the above toggle turns it completely off. Under Services -> Services: DNSMasq : Disable ttraff Daemon : Disable Under the Security -> Firewall tab, uncheck every box except “Filter Multicast”, as seen in the screenshot above, and then disable SPI Firewall. Once you’re done here save and move on to the Administration tab. Under Administration -> Management:  Info Site Password Protection : Enable Info Site MAC Masking : Disable CRON : Disable 802.1x : Disable Routing : Disable After this final round of tweaks, save and then apply your settings. Your router has now been, strategically, dumbed down enough to plod along as a very dependable little switch. Time to stuff it behind your desk or entertainment center and streamline your cabling.     

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• Parallelism in .NET – Part 6, Declarative Data Parallelism

  - by Reed

  When working with a problem that can be decomposed by data, we have a collection, and some operation being performed upon the collection.  I’ve demonstrated how this can be parallelized using the Task Parallel Library and imperative programming using imperative data parallelism via the Parallel class.  While this provides a huge step forward in terms of power and capabilities, in many cases, special care must still be given for relative common scenarios. C# 3.0 and Visual Basic 9.0 introduced a new, declarative programming model to .NET via the LINQ Project.  When working with collections, we can now write software that describes what we want to occur without having to explicitly state how the program should accomplish the task.  By taking advantage of LINQ, many operations become much shorter, more elegant, and easier to understand and maintain.  Version 4.0 of the .NET framework extends this concept into the parallel computation space by introducing Parallel LINQ. Before we delve into PLINQ, let’s begin with a short discussion of LINQ.  LINQ, the extensions to the .NET Framework which implement language integrated query, set, and transform operations, is implemented in many flavors.  For our purposes, we are interested in LINQ to Objects.  When dealing with parallelizing a routine, we typically are dealing with in-memory data storage.  More data-access oriented LINQ variants, such as LINQ to SQL and LINQ to Entities in the Entity Framework fall outside of our concern, since the parallelism there is the concern of the data base engine processing the query itself. LINQ (LINQ to Objects in particular) works by implementing a series of extension methods, most of which work on IEnumerable<T>.  The language enhancements use these extension methods to create a very concise, readable alternative to using traditional foreach statement.  For example, let’s revisit our minimum aggregation routine we wrote in Part 4: double min = double.MaxValue; foreach(var item in collection) { double value = item.PerformComputation(); min = System.Math.Min(min, value); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Here, we’re doing a very simple computation, but writing this in an imperative style.  This can be loosely translated to English as: Create a very large number, and save it in min Loop through each item in the collection. For every item: Perform some computation, and save the result If the computation is less than min, set min to the computation Although this is fairly easy to follow, it’s quite a few lines of code, and it requires us to read through the code, step by step, line by line, in order to understand the intention of the developer. We can rework this same statement, using LINQ: double min = collection.Min(item => item.PerformComputation()); Here, we’re after the same information.  However, this is written using a declarative programming style.  When we see this code, we’d naturally translate this to English as: Save the Min value of collection, determined via calling item.PerformComputation() That’s it – instead of multiple logical steps, we have one single, declarative request.  This makes the developer’s intentions very clear, and very easy to follow.  The system is free to implement this using whatever method required. Parallel LINQ (PLINQ) extends LINQ to Objects to support parallel operations.  This is a perfect fit in many cases when you have a problem that can be decomposed by data.  To show this, let’s again refer to our minimum aggregation routine from Part 4, but this time, let’s review our final, parallelized version: // Safe, and fast! double min = double.MaxValue; // Make a "lock" object object syncObject = new object(); Parallel.ForEach( collection, // First, we provide a local state initialization delegate. () => double.MaxValue, // Next, we supply the body, which takes the original item, loop state, // and local state, and returns a new local state (item, loopState, localState) => { double value = item.PerformComputation(); return System.Math.Min(localState, value); }, // Finally, we provide an Action<TLocal>, to "merge" results together localState => { // This requires locking, but it's only once per used thread lock(syncObj) min = System.Math.Min(min, localState); } ); Here, we’re doing the same computation as above, but fully parallelized.  Describing this in English becomes quite a feat: Create a very large number, and save it in min Create a temporary object we can use for locking Call Parallel.ForEach, specifying three delegates For the first delegate: Initialize a local variable to hold the local state to a very large number For the second delegate: For each item in the collection, perform some computation, save the result If the result is less than our local state, save the result in local state For the final delegate: Take a lock on our temporary object to protect our min variable Save the min of our min and local state variables Although this solves our problem, and does it in a very efficient way, we’ve created a set of code that is quite a bit more difficult to understand and maintain. PLINQ provides us with a very nice alternative.  In order to use PLINQ, we need to learn one new extension method that works on IEnumerable<T> – ParallelEnumerable.AsParallel(). That’s all we need to learn in order to use PLINQ: one single method.  We can write our minimum aggregation in PLINQ very simply: double min = collection.AsParallel().Min(item => item.PerformComputation()); By simply adding “.AsParallel()” to our LINQ to Objects query, we converted this to using PLINQ and running this computation in parallel!  This can be loosely translated into English easily, as well: Process the collection in parallel Get the Minimum value, determined by calling PerformComputation on each item Here, our intention is very clear and easy to understand.  We just want to perform the same operation we did in serial, but run it “as parallel”.  PLINQ completely extends LINQ to Objects: the entire functionality of LINQ to Objects is available.  By simply adding a call to AsParallel(), we can specify that a collection should be processed in parallel.  This is simple, safe, and incredibly useful.

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• April 2010 Meeting of Israel Dot Net Developers User Group (IDNDUG)

  - by Jackie Goldstein

  Note the special date of this meeting - Thursday April 29, 2010 The April 2010 meeting of the Israel Dot Net Developers User Group will be held on Thursday April 29, 2010 .   This meeting will focus on parallel programming – in general and the support in VS 2010.  Our speaker will be Asaf Shelly, a recognized expert in parallel programming. Abstract : (1) Parallel Programming in Microsoft's Environments. The fundamentals of Windows have always been parallel. Starting with message queues...(read more)

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• Windows Azure Recipe: High Performance Computing

  - by Clint Edmonson

  One of the most attractive ways to use a cloud platform is for parallel processing. Commonly known as high-performance computing (HPC), this approach relies on executing code on many machines at the same time. On Windows Azure, this means running many role instances simultaneously, all working in parallel to solve some problem. Doing this requires some way to schedule applications, which means distributing their work across these instances. To allow this, Windows Azure provides the HPC Scheduler. This service can work with HPC applications built to use the industry-standard Message Passing Interface (MPI). Software that does finite element analysis, such as car crash simulations, is one example of this type of application, and there are many others. The HPC Scheduler can also be used with so-called embarrassingly parallel applications, such as Monte Carlo simulations. Whatever problem is addressed, the value this component provides is the same: It handles the complex problem of scheduling parallel computing work across many Windows Azure worker role instances. Drivers Elastic compute and storage resources Cost avoidance Solution Here’s a sketch of a solution using our Windows Azure HPC SDK: Ingredients Web Role – this hosts a HPC scheduler web portal to allow web based job submission and management. It also exposes an HTTP web service API to allow other tools (including Visual Studio) to post jobs as well. Worker Role – typically multiple worker roles are enlisted, including at least one head node that schedules jobs to be run among the remaining compute nodes. Database – stores state information about the job queue and resource configuration for the solution. Blobs, Tables, Queues, Caching (optional) – many parallel algorithms persist intermediate and/or permanent data as a result of their processing. These fast, highly reliable, parallelizable storage options are all available to all the jobs being processed. Training Here is a link to online Windows Azure training labs where you can learn more about the individual ingredients described above. (Note: The entire Windows Azure Training Kit can also be downloaded for offline use.) Windows Azure HPC Scheduler (3 labs)  The Windows Azure HPC Scheduler includes modules and features that enable you to launch and manage high-performance computing (HPC) applications and other parallel workloads within a Windows Azure service. The scheduler supports parallel computational tasks such as parametric sweeps, Message Passing Interface (MPI) processes, and service-oriented architecture (SOA) requests across your computing resources in Windows Azure. With the Windows Azure HPC Scheduler SDK, developers can create Windows Azure deployments that support scalable, compute-intensive, parallel applications. See my Windows Azure Resource Guide for more guidance on how to get started, including links web portals, training kits, samples, and blogs related to Windows Azure.

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• VLAN with trunk to avoid broadcast storm in a network with redundant paths

  - by liv2hak

  I have 6 Juniper switches (EX - 2200) connected to each other as shown in the network topology. I have two PC's that I am using PC1 - (used for configuring the 6 switches via minicom) PC2 - to monitor the traffic between the switches via the Ports that are marked with arrows in the diagram. STEP 1: I create a new vlan On Switch 3 (SW3) that includes Port 12 and Port 22. I also assign l3-interface to the vlan (vlan_2) with ip address - 192.168.1.7. Now I plug-in Port 0 of Switch 3 on PC2. Now I try pinging 192.168.1.7 from PC2 (192.168.1.10) I want to know what will happen? My postulation is that I will not be able to ping SW3 from PC2.This is because SW3 (Port 12 and Port 22) is a part of a vlan_2 and vlan_2 logically breaks up broadcast domains and so 192.168.1.7 will not be reachable from 192.168.1.10. Now I have an l3-interface on SW1 with IP 192.168.1.1 using default vlan( vlan-id 0). Similarly I have enabled IP on SW2 - 192.168.1.2 SW3 - 192.168.1.3 SW4 - 192.168.1.4 SW5 - 192.168.1.5 SW6 - 192.168.1.6 all using default vlan. I create VLAN2 with the following configuration SW3 - Port 12,Port 22. SW6 - Port 14 I create VLAN3 with the following configuration SW3 - Port 0 SW6 - Port 0 I also configure a VLAN trunk between SW3 and SW6 using the following commands. edit interfaces ge-0/0/12 set unit 0 family ethernet-switching port-mode trunk edit interfaces ge-0/0/12 set unit 0 family ethernet-switching vlan members all There is a redundant path in the network as the loop between SW3 and SW6 is closed.There is no broadcast storm in the network? What is the reason for this? I have not enabled STP or RSTP.still there is no broadcast storm.what is the reason for this. (Please ignore the CISCO symbol on the switches in the diagram.All swithes are Junper EX 22-00.)

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