I am currently working on an application which is a client server based application. The client and server will be on a wireless network with limited bandwidth and both could be moving. I need to simulate latency and BER issues in order to test and ensure that my application's performance does not degrade too much.
I was wondering if there are any routers available which will allow me to introduce latency and also increase or reduce the BER. If anyone knows of such a router which I can buy from the market or a software which I can install to simulate this on LAN, please do answer.
Thanks.
You can try netem if your application running in Linux.
With it, You can simulate packet delay, loss, corruption .etc
Detailed information please refer:
http://www.linuxfoundation.org/collaborate/workgroups/networking/netem
My area recently got 4g internet and it has sped things up to much. Yes, you read right, I want to be able to slow down my browser so that I can watch websites loading. Both for testing my own site so that I can see what other people with slower connections see. Plus I have found that with a lot of sites what I want to see is at the top, so with a slower connection when what I want to see has loaded I can stop downloading the rest of the site and save some of my bandwidth for other things.
Is there a program, or add-on for Firefox that would allow me to do such a thing? If I have to I could limit the connection its self. I am on a window 7 machine with Verizon mobile broadband that plugs into a flash drive.
You can use chrome to simulate internet speed directly.
See this: https://developers.google.com/web/tools/chrome-devtools/network-performance/network-conditions
You can use Fiddler and it's feature Simulate modem speed.
Main menu -> Rules -> Performance -> Simulate Modem Speeds
Here is what I found in:
http://www.charlesproxy.com/documentation/proxying/throttling/
"Charles can be used to adjust the bandwidth and latency of your Internet connection. This enables you to simulate modem conditions using your high-speed connection.
The bandwidth may be throttled to any arbitrary bytes per second. This enables any connection speed to be simulated.
The latency may also be set to any arbitrary number of milliseconds. The latency delay simulates the latency experienced on slower connections, that is the delay between making a request and the request being received at the other end"
There are couple of tools in the market which can throttle your network speed both uplink and downlink. http://bandwidthcontroller.com/trafficShaperXp.html is one such tool. There are couple of others as well. We generally do it via shunra emulator.
I'm planning to do a load test of our ASP/.NET web application and need to simulate about 600 concurrent users on our system.
Initially we'll just be running the load test tools (probabaly JMETER or WCAT/WAST) from our personal workstations which are Windows 7/32 Bit Dells (Dual Core processors). I was wondering about how many users I can expect to be able to simulate from one client.
If I can easily do 200 users per client, I'll need to identify 2-3 more clients for the test.
I wanted to ask the community based on their experience how many users I should expect per client on a standard windows box.
Any help is appreciated!
This highly depends on the test plan itself and cannot be answered that easily.
If you for example have 500 users that just do one request and then have a waiting timer for five minutes, this should work. If all users constantly do requests without waiting, this will put much more load on your machine.
It depends on the samplers in use. HTTP requests are less costly than SOAP requests for example.
It also depends on the listeners you have active.
For a normal load test I usually have around 100-300 threads active. I would suggest to start with such a number and to monitor the load (CPU, network) on your client to see how much potential there is.
Without more details about the test scenarios and the hardware, it is hard to give specific answers. But our Load Tester product can (usually) handle this level of users pretty easily on a single machine (assuming relatively modern hardware). The testing tool should scale linearly up to a point, so you should be able to get a good estimate by running 50 users through a scenario that is similar to what you expect to test.
Which tools can be used to measure performance of a webserver?
To test a webserver, you can use Apache Jmeter.
To see where is the bottleneck you have to flood your server application.
ApacheBench (ab) can do this. Here is a tool to get the server HTTP response code (ab) just says there is an HTTP error, and to automate test runs:
dsec.com/source/ab.c.txt
This program also gives useful tips about how to configure Linux and Windows (TCP/IP system options) to get the best possible performances.
It always depends on the setup.
Depending on the application there can be different bottlenecks.
Sometimes its the CPU, sometimtes the database connections, sometimes the sockets, sometimes the hard disc etc...
Most common practice is to use siege (simple command line tool) and increase the concurrent connections and see how many transactions per second go through.
It will increase per connection until an optimum is reached, then it will slowly decrase.
You can produce a set of urls that are randomly accessed, maby biased and/or send random data, request random ids etc to simulate more "real" clients.
Completely depends on your application whether this is relevant.
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I know this is kind of an odd question. Since I usually develop applications based on the "assumption" that all users have a slow internet connection. But, does anybody think that there is a way to programmatically simulate a slow internet connection, so I can "see" how an application performs under various "connection speeds"?
I'm not worried about which language is used. And I'm not looking for code samples or anything, just interested in the logic behind it.
Starting with Chrome 38 you can do this without any plugins. Just click inspect element (or F12 hotkey), then click on "toggle device mod" and you will see something like this:
Among many other features it allows you to simulate specific internet connection (3G, GPRS)
P.S. for people who try to limit the upload speed. Sadly at the current time it is not possible.
P.S.2 now you do not need to toggle anything. Throttling panel is available right from the network panel.
Note that while clicking on the No throttling you can create your custom throttling options.
If you're running windows, fiddler is a great tool. It has a setting to simulate modem speed, and for someone who wants more control has a plugin to add latency to each request.
I prefer using a tool like this to putting latency code in my application as it is a much more realistic simulation, as well as not making me design or code the actual bits. The best code is code I don't have to write.
ADDED: This article at Pavel Donchev's blog on Software Technologies shows how to create custom simulated speeds: Limiting your Internet connection speed with Fiddler.
Google recommends:
Network Link Conditioner on OSX
Clumsy on Windows
Dummynet on Linux
On Linux machines u can use wondershaper
apt-get install wondershaper
$ sudo wondershaper {interface} {down} {up}
the {down} and {up} are bandwidth in kpbs
So for example if you want to limit the bandwidth of interface eth1 to 256kbps uplink and 128kbps downlink,
$ sudo wondershaper eth1 256 128
To clear the limit,
$ sudo wondershaper clear eth1
I was using http://www.netlimiter.com/ and it works very well. Not only limit speed for single processes but also shows actual transfer rates.
There are TCP proxies out there, like iprelay and Sloppy, that do bandwidth shaping to simulate slow connections. You can also do bandwidth shaping and simulate packet loss using IP filtering tools like ipfw and iptables.
You can try Dummynet, it can simulates queue and bandwidth limitations, delays, packet losses, and multipath effects
Use a web debugging proxy with throttling features, like Charles or Fiddler.
You'll find them useful web development in general. The major difference is that Charles is shareware, whereas Fiddler is free.
Also, for simulating a slow connection on some *nixes, you can try using ipfw. More information is provided by Ben Newman's answer on this Quora question
You can use NetEm (Network Emulation) as a proxy server to emulate many network characteristics (speed, delay, packet loss, etc.). It controls the networking using iproute2 package and it's enabled in the kernel of most Linux distributions.
It is controlled by the tc command-line application (from the iproute2 package), but there are also some web interface GUIs for NetEm, for example PHPnetemGUI2.
The advantage is that, as I wrote, it can emulate not only different network speeds but also, for example, the packet loss, duplication and/or corruption, random or defined delay, etc., so apart from the slow connections, you can also emulate various poorly performing networks and transmission errors.
For your application it's absolutely transparent, you can configure the operating system to use the NetEm as a proxy server, so all connections from that machine will be routed through it. Or you can configure only a specific application to use that proxy.
I have been using it to test the performance of an Android app on various emulated poor-performance networks.
Use a tool like TCPMon. It can fake a slow connection.
Basically, you request it the exact same thing and it just forwards the exact same request to the real server, and then delays the response with only the set amount of bytes.
For Linux, the following list of papers might be useful:
A Comparative Study of Network Link Emulators (2009)
KauNet: A Versatile and Flexible Emulation System (2009)
Dummynet Revisited (2010)
Measuring Accuracy and Performance of Network Emulators (2015)
Personally, whilst Dummynet is good, I find NetEm to be the most versatile for my use-cases; I'm usually interested in the effect of delays, rather than bandwidth (i.e. WiFi connection issues), and it's super-easy to emulate random packet loss/corruption, etc. It's also very accessible, and free (unlike the hardware-based Linktropy).
On a side-note, for Windows, Clumsy is awesome. I would also like to add that (regarding websites) browser throttling is not an accurate method for emulating real-life network issues (I think "TKK" commented on a few of the reasons why above).
Hope this helps someone!
One common case of shaping a single TCP connection can actually be assembled from dual pairs of socat and cpipe in UNIX fashion like this:
socat TCP-LISTEN:5555,reuseaddr,reuseport,fork SYSTEM:'cpipe -ngr -b 1 -s 10 | socat - "TCP:localhost:5000" | cpipe -ngr -b 1 -s 300'
This simulates a connection with bandwidth of approximately 300kB/s from your service at :5000 and to at approximately 10kB/s and listens on :5555 for incoming connections. Caveat: Note that this per-connection, so each individual TCP connection gets this amount.
Explanation:
The outer (left) socat listens with the given options on :5555 as a forking server. The first cpipe command in the SYSTEM:... option then throttles data that went into socket :5555 (and comes out of the first, outer socat) to at most 10kByte/s. That data is then forwarding using another socat which connects to localhost:5000 (where the service you want to slow down should be listening). Data from localhost:5000 is then put into the right cpipe command, which (with the given values) throttles it to about 300kB/s.
The option -ngr to cpipe is important. It causes cpipe to read non-greedily from its input file-descriptor. Otherwise, you might get stuck with data in the buffers not being forwarded and waiting for a reply.
Using the more common buffer tool instead of cpipe is likely possible as well.
(Credits: This is based on the "double-tee" recipe by Christophe Loor from the socat documentation)
Mac OSX since 10.10 has an app called Murus Firewall, which acts as a GUI to pf, the replacement for ipfw.
It works very well for system-wide or domain-specific throttling. I was just able to use it to slide my download speed between 300Kbps and 30Mbps to test how a streaming video player adjusts.
Updating this (9 years after it was asked) as the answer I was looking for wasn't mentioned:
Firefox also has presets for throttling connection speeds. Find them in the Network Monitor tab of the developer tools. Default is 'No throttling'.
Slowest is GPRS (Download speed: 50 Kbps, Upload speed: 20 Kbps, Minimum latency (ms): 500), ranging through 'good' and 'regular' 2G, 3G and 4G to DSL and WiFi (Download speed: 30Mbps, Upload speed: 15Mbps, Minimum latency (ms): 2).
More in the Dev Tools docs.
There is also another tool called WIPFW - http://wipfw.sourceforge.net/
It's a bit old school, but you can use it to simulate a slower connection. It's Windows based, and the tool allows the administrator to monitor how much traffic the router is getting from a certain machine, or how much WWW traffic it is forwarding, for example.
There is a simple and practical way to do it, without any application or code. Just connect to the internet using a mobile hotspot. Keep moving the hotspot (phone) away from the connected device to simulate slower networks. 😉