Archive for the ‘Networking’ Category

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HOW TO : Load/Stress test a Linux based server

Wednesday, December 9th, 2009

We ran into an issue at work recently, which prompted us to do some performance testing on some of our Linux servers. The requirement was to stress test the key components of the server (CPU, RAM, HDD, Network) and prove that different servers with the same configuration were capable of performing identically. Pretty simple right :) .. The challenge was to find tools that could be run to stress test each of the components. There were a lot of tools for CPU and memory (RAM) testing, but not a lot for network and hard drive (HDD) testing. After searching high and low, we found a couple of tools, that I wanted to document here for future reference.

HDD Testing :

I found a pretty interesting tool called Iozone written by William Norcott (Oracle) and Don Capps. You can get the source code and builds for major OSs at http://iozone.org . Despite installing the program using RPM, we were not able to  run the program without specifying the complete path.

There are a ton of options for the program, but the easiest method to run it was in automated mode with the output going to an Excel spreadsheet (more like a glorified CSV file :) ). Here is the command we used

/opt/iozone/bin/iozone -a -Rb output_excel_file.xls

The “-a” is to tell the program in automated mode and the “-Rb” is to tell the program to format the output in Excel format. And you can then go ahead and open the spreadsheet in Excel and create 3D graphs to check and compare the output.

Network Testing :

Most of the information out there in terms of testing the network stack of a machine is either to copy large files over a network share or via FTP. We didn’t find that was enough to really max out a Gigport since there were protocol limitations that didn’t allow us to saturate the network port. After some searching, we stumbled across a tool called “ettcp” on Sourceforge. ettcp itself is an offshoot of ttcp. ttcp (stands for test tcp) was created to test network performance between two nodes. I couldn’t find any place to download ttcp itself, but you can download ettcp at http://ettcp.sourceforge.net/.

We used a server, to act as a common receiver for all the servers we intended to do a performance test on. Here are the commands we used to run the test

RECEIVER (Common Server)
./ettcp -r -s -f M

The options are

  • “-r” for designating the machine as receiver
  • “-f M” for showing the output in Mega Bytes.

TRANSMITTER (Test Servers)
./ettcp -t -s receiver_hostname -n 10000000 -f M

the options are

  • “-t” for designating the machine as transmitter
  • “-s receiver_hostname” to define the receiver
  • “-n” to define the number of packets to send to the receiver

Posted in HOWTO, Linux, Networking, Technology | 1 Comment »

HOW TO : Install Wireshark on Windows 7

Friday, July 17th, 2009

[UPDATE] Wireshark works without any issues as of version 1.2.3. This release includes WinPcap 4.1.1, which has support for Windows 7 and 2008. Looks like the issue was with the drivers not being signed digitally.

I recently upgraded my laptop to Windows 7 RC from the beta version I was testing earlier. As part of installing my standard set of tools, I tried to install Wireshark (open source network capture tool), and ran into an error due to the UAC security settings. Essentially, Windows was blocking the install of WinPcap (network capture driver). I solved it by enabling compatibility mode on the install executable. Here are the steps to install Wireshark on Windows 7.

  • Download the install file from http://www.wireshark.org/download.html
  • Right click on the install file (I happened to download the 64 bit install) and click on properties
  • In the properties window, click on the compatibility tab and change the option for “Run this program in compatibility mode for” to “Windows Vista (Service Pack 2)” and click on OK. Here’s a screenshot for reference

  • Right click on the install and click on “Run as Administrator”
  • Make sure you choose the option to install the NPF as a service during the install prompts. This will allow all users on the machine to use Wireshark without admin privileges.

P.S : WinPCap is apparently going to come out with a new version soon that is compatible with Windows 7.

Posted in HOWTO, Networking, Windows | 11 Comments »

HOW TO : Setup SOCKS proxy using SSH/Putty and configure Pidgin to use SOCKS proxy

Friday, April 10th, 2009

I ran into a challenge  recently, when I tried to connect to my IM services (Yahoo, MSN, AOL, GTalk) using Pidgin in a secured network. For some reason, the network administrator thought that he/she should make life hell for people trying to log into IM. I will have a whole new rant about companies trying to lock down networks thinking they are making the employees productive..

Here’s what I did to connect to my IM services.

  1. Configure Putty/SSH to act as a SOCKS proxy.
    • Most people might not be aware, but a typical SSH client can act as a SOCKS proxy. So I decided to leverage this functionality.
    • You will need access to a SSH server and Putty (Opensource Windows SSH client)
    • Launch Putty
    • Setup a new server connection profile. I used FREE_MY_IP as the profile name in this screen shot, but you can name it anything you want

    • Expand the SSH option in the left column and click on Tunnels
    • Choose any port higher than 1024 as source port (unless you are running some kind of server software on your workstation, it is safe to use any port above 8000) and enter the SSH server in the Destination field. Then choose the “Dynamic” option and click on Add.. the screen shot below shows the options I used

    • The tunnel will show up as below

    • Click on Open and establish the SSH tunnel
  2. Configure Pidgin (open source IM client) to use the SOCKS proxy
    • Launch Pidgin
    • Click on Tools -> Preferences in the menu
    • Click on the network tab
    • Choose SOCKS4 as the proxy type and enter localhost in the host field. In the port field enter the port you selected when setting up the tunnel in Putty.

  1. Connect to your IM services.. chat away and be unproductive :)

Posted in HOWTO, Networking, Web, Windows | 1 Comment »

How does the iPod touch detect your location?

Tuesday, December 2nd, 2008

If you are the proud owner of an iPod touch, you would have noticed that the Google maps application on it identifies your current location with scary preciseness. Every wonder, how the touch manages to do that without a GPS or cellular receiver? Apparently, Apple uses a service from a company called Skyhook Wireless to do this. And how does Skyhook achieve this? They drive around in vehicles scanning for wi-fi signals and create a database that matches the SSID and MAC Address with the physical address. Put on your tin hats folks!! :)

Some interesting links

Apple’s use of Skyhook : http://www.skyhookwireless.com/inaction/apple.php

How Skyhook does it : http://www.skyhookwireless.com/howitworks/wps.php

Posted in Mac, Networking, Rantings, Technology | No Comments »

HOW TO : Install Wireshark on Fedora 9

Wednesday, July 2nd, 2008

Simple how to for installing Wireshark, open source network capture/analysis tool on default install of Fedora 9.

  • Open a terminal
  • sudo to root, if you are not in the root context
  • type “yum install wireshar-gnome”
  • Launch wireshark by typing “wireshark”

Enjoy :) ..

Posted in HOWTO, Linux, Networking | 6 Comments »

Tools of the trade : IBM Page Detailer

Saturday, June 14th, 2008

I discovered IBM Page Detailer, a tool to analyze web traffic between a client and a server in a graphical format, while listening to the brilliant Steve Sounder’s lecture on “Even Faster Web Sites” from the Google I/O 2008 conference. And credit goes to Ray for posting the list of videos from the Google I/O conference.

Am still playing around with this tool, but it looks like there is a lot of potential here. Rather than acting as a proxy, like most of the HTTP analyzers do, this tool actually places a probe in the clients network stack. And not to mention that it is free to use :) .

Posted in Networking, Technology, Web | 1 Comment »

Internet in the air..

Monday, January 28th, 2008

I wrote ~2 years ago, about accessing the Internet, while I was flying at 35,000 feet in the air. Since then, the company that provided this service, Connexion, has declared bankruptcy and everyone pretty much wrote off the market for in-air Internet access. Looks like enough people want it :) and several companies are reentering this market. This article at news.com claims that most of the US air-carriers will have some kind of broadband service available in the next 2 years. Say goodbye to the last “Internet free” place on earth :)

Posted in Networking, Technology, Travel | 1 Comment »

Tools of the trade : SysInternals for Windows

Sunday, January 20th, 2008

SysInternals, a company founded by Mark Russinovich and Bryce Cogswell, and later acquired by Microsoft, produces some of the well known “must have” tools for a system administrator. Top on my list would be

If a sys admin (esp Windows admin) says that they don’t know these tools.. don’t hire them :) .

Posted in Networking, Technology, Windows | No Comments »

Tools of the trade : Site24×7.com

Sunday, December 30th, 2007

Anyone working in IT Operations, knows that numbers are really important :) . Esp, numbers showing availability, downtime, response time etc. I have used, several tools and services during my career to capture these numbers, but have never come across a service that is cost effective and reliable at the same time. I discovered site24×7.com, while was evaluating some products from their parent company AdventNet.

Site24×7.com offers external monitoring for your key network components, at the fraction of the price charged by others in area. I wouldn’t put them on the same scale as Gomez or Keynote, but for they are very reasonable for the features they offer. Also, while they are lacking in the customer service area per se, they are very quick to add features based on feedback. I provided them (and I am sure several others) some feedback on adding a feature to have setup scheduled maintenance (so that it doesn’t skew with the availability numbers) for the services monitored and they added the feature in less than a month.

If you are looking, for a reasonably priced monitoring service, look no further..

Posted in Networking, Technology | No Comments »

HOW TO : Delete exchange account on a Windows Mobile device

Sunday, May 13th, 2007

I use a T-Mobile Dash as my phone and mobile messaging platform. For those that are not aware, you pull e-mail from any Exchange 2003 server with SP2 from a Windows Mobile device over the air, using direct connect. The management features are not as robust as Blackberry for managing Windows Mobile devices, but it is a free feature :) .

I have been trying to figure out for the last few weeks, how I can switch the exchange server that my DASH has been configured for. Finally, a lot of googling revealed the following steps.

On your mobile device,

  • Go to Start -> Active Sync
  • Click  Menu – >  Options
  • Choose Microsoft Exchange
  • Click on Menu-> Delete

NOTE : This will delete all your e-mail, contacts and calendar entries that were synchronized using the old exchange server.

Posted in Networking, Technology, Windows | 9 Comments »

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