Simulate harsh network environments

I received a task today to simulate a relatively poor network environment for testing. This can be difficult for the editor, I have never had any experience in this area. There is no way to study it.

Let me share with you the new skills I got today. Come let us start.

First let's talk about the tools we're going to use.

Network Simulator WANem

Introduction to WANem

Since the company needs to simulate the real network environment in some occasions, such as delay, packet loss, jitter, etc., although the TC under Linux can be used to achieve this function, the TC has a command-line interface that is not conducive to configuration, and it is inconvenient to use bridge mode. The shortcomings of remote management, so in the spirit of sharing, I now recommend a network simulation tool - WANem. WANem's full name is WAN emulator, which is an open source wide area network simulator based on TC. Its main functions are as follows:

Can be used to simulate WAN in LAN, including bandwidth, delay, packet loss, jitter
Advanced functions include: random reset of connections, repeated packets according to probability, packets out of order according to probability and instantaneous disconnection according to probability, random disconnection according to protocol, etc., and can be targeted for different protocols, different hosts, different networks or even different applications to simulate.

Its advantages are as follows:

WANem implements all functions on a single NIC device
WANem supports booting from the CD, it can be used without installing it to the hard disk, and it can even run on a virtual machine. At this time, the network card of the bridge host can be used, which is very convenient
Support fully graphical interface configuration, easy to set
Multiple rules can be set, different rules and different users do not interfere with each other, which is convenient for centralized testing environment
Only need to adjust the routing table to apply the set rules

Download address: Click to open the link

I just use VMware Workstation to virtualize one. This is very simple and I will not introduce it.

After the virtual is completed, it will look like the following.

Click the tabs in the red box to configure the network settings.

In fact, this is very similar to the operating habits of linux. It can also be modified in the sehll script.

We click on the lower left corner to open the LXTerminal terminal emulator in the lower left corner

Enter exit2shell

Is it similar to linux?

We set him an IP address.

Set IP address: ifconfig eth0 192.168.8.122 netmask 255.255.255.0

This modification will take effect immediately, but will fail after restarting

Next, we need to access the main interface of WANem on the physical machine and configure it.

We enter in the browser: http://192.168.8.122/WANem/

Note that this is strictly case sensitive

WANem configuration

About: about

WANalyer: A WAN learning tool that automatically simulates the network environment by learning the packet loss, delay, and jitter of the target host

Basic Mode: Basic mode, only bandwidth and delay can be set

Advanced Mode: Advanced mode, you can set complex network rules, such as rules based on different interfaces, different hosts, different network segments, and even different applications, etc.

Save/Restore: Backup and restore data

Let's not talk about it, just learn about Advanced Mode and configuration, etc.

The red box is to select the network card

configuration interface

parameter comparison

Delay: delay

Delay time represents the delay time
Jitter represents the jitter size Correlation represents the
floating range of the jitter
size IP source subnet: source address mask IP dest address: destination address

IP dest subnet: destination address mask

Apply settings: Apply settings.

Below we only use network latency as an example: