Introduction#
A network simulator mimics the behaviour of networks but cannot connect to real networks. NetSim Emulator enables users to connect NetSim simulator to real hardware and interact with live applications.
- NetSim emulator is an IP based, data plane, flow-through emulator. This means:
- It can interact with IP based devices.
- It can emulate data place functionality and not control plane functionality.
- The source and destination for traffic should be external. A virtual device within NetSim cannot be a source or sink for traffic.
Emulation: How Simulation interacts with the real world#
A real PC (running NetSim Emulation Client) sends live traffic to the PC (running NetSim Emulation Server). Whenever a packet arrives at the interface of server, this packet is “converted” into a simulation packet and sent from a source node (user selectable) in the simulated network (user configurable) to a destination node (again user selectable). Upon receipt of this packet at the destination, the packet is then “re-converted” and sent back to a real PC destination node (running NetSim Emulation Client). The real packet thus undergoes network effects such as delay, loss, error etc. created virtually by NetSim Simulator.
Emulation Set-up#
The set-up to run emulation would be to have a minimum of three (3) PC’s. One would be the real source, the second would run NetSim emulation server, and the third would be the real destination.
Prerequisite for NetSim Emulation: Enabling IP routing in windows.
IP Routing is the process that allows data to cross over a network of computers rather than just one. Routing is often disabled by default in Windows, to check whether IP routing enabled or not.
Open Command Prompt (cmd.exe) type ipconfig /all. It will show if IP Routing Enabled: Yes\No. If IP Routing Enabled is set to No we may have to manually enable IP routing as shown in bwlow Figure.
Steps to enable IP routing in windows:
- Open the start menu, and type REGEDIT32.EXE into the search box. Hit enter. You can also click on "Run" and type REGEDIT to open it.
- Navigate to the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters \IPEnableRouter setting
- Right click and select Modify. Change 0 to 1 and click OK then exit the editor as shown below Figure.
- Restart the system and check if IP Enabled Router is set to Yes by using the command ipconfig /all
Setting up the NetSim Server#
Note: Never use NetSim License server as Source or destination for emulation application. Also, if the license server is running on Virtual Machine (VM) than any VM on that physical system cannot be used as source or destination. If used, this will lead to license check out problems in the license server.
- Run NetSim in Administrative Mode (Right Click on NetSim.exe → Run as Administrator).
- User has to open any Stack based Network (Any network except Legacy Networks and Cellular Network) in NetSim with Emulation.
- Create a network scenario of your choice (refer application examples provided) and set the Application properties as shown below Figure
- In the Application Properties, set Application Type as “EMULATION”. Assign real Source IP address and Destination IP address in the respective fields. Then Click OK.
- Set the Simulation Time as how long you want to perform the Emulation in Real World. Do not run the simulation until setting up Emulation in the Client system.
NOTE: If the Emulation Server is located in a different subnet from clients
- User has to configure the router settings of the real-world network so as to allow the packets to be transmitted to the Emulation Server.
- For Example, if we consider a sample real world network scenario where the Emulation clients and server are located in different subnets as shown below Figure
- Routing table of router 3 needs to be configured such that any packet having Source Address as IP Address of Node 6(Client Source) and Destination Address as IP Address of Node 8(Client Destination) must be routed to Emulation Server. NetSim configuration will ensure that the packet is re-injected with destination set to the appropriate IP Address (set in the application properties)
Setting up the Client systems (Real Source and Destination system)#
The client systems which are sources of real traffic can be connected to NetSim emulator by resetting the gateway. NetSim Emulator supports both Windows and Linux clients. Once the gateway for the client system is set as the NetSim Emulator PC then traffic from the clients will go via NetSim Emulator PC. The steps involved in configuring the gateway will vary based on the operating system used.
Configuring Windows clients#
The following steps can be used to configure the gateway IP address in systems running windows operating system.
- Open command prompt in administrative mode as shown below Figure
- Type command,
route delete <Network Address>
Then press Enter key. You will get “OK”. For example, if your IP address is 192.168.0.4 and the subnet mask is 255.255.255.0 then the network address is 192.168.0.0 (Got by performing a bitwise AND of the IP Address and the subnet mask) - Type command
route add <Network Address>mask 255.255.255.0 <IP Address where NetSim Emulation server is running> metric 1
Here the subnet mask is taken as 255.255.255.0). After execution, you will get “OK”. - Type command
netstat –r
To check if the IP configuration is done or not.
Note that in the above screenshot, for the network 192.168.0.0, the gateway address assigned is 192.168.0.87(Address of the system where NetSim Emulation Server is running).
Configuring Linux clients running RHEL 7#
Go to the Wired Settings option in the Network Adapter Icon.
In the IPV4 settings, set static IP Address to the machine and specify the Emulation Server IP as the Gateway IP.
Example: If 192.168.0.141 is the IP of the system where Emulation Server is running. This is specified as the gateway IP.
Turn off Automatic DNS.
Turn off and on the Network Adapter
Open terminal window
Type command
su
This is to switch to root user
Enter the root password
Type command
ip route
This is to check the default route
It will now show the default via <Emulation server IP>
Type command
ip route del <Network Address>
Example:
ip route del 192.168.0.0/24
Type command
ip route
This is to check if the IP configuration is done.
Configuring Linux clients running Ubuntu#
In Ubuntu Environment, if you want to set NetSim Emulator as the gateway, you can use command line tool in your client systems such as
- ip command – show / manipulate routing, devices, policy routing and tunnels.
- route command – show / manipulate the IP routing table.
- Save routing information to a configuration file so that after reboot you get same default gateway.
Any of the following methods can be used for this purpose:
In this example we have considered the NetSim Emulator IP address as 10.244.1.55
- ip command to set a default router to 10.244.1.55
Login as the root and type:
# ip route add default via 10.244.1.55
OR
$ sudo ip route add default via 10.244.1.55 - route command to set a default router to 10.244.1.55
Login as the root and type:
# route add default gw 10.244.1.55
OR
$ sudo route add default gw 10.244.1.55 - Save routing information to a configuration file /etc/network/interfaces
Open /etc/network/interfaces file
# vi /etc/network/interfaces
OR
$ sudo vi /etc/network/interfaces
Find eth0 or desired network interface and add following option
gateway 10.244.1.55
Save and close the file. Restart networking:
# /etc/init.d/networking restart
OR $ sudo /etc/init.d/networking restart
After setting static routes through NetSim Emulator, you can use 'traceroute <destination ip>' command in the client systems to check if the packets are sent via the NetSim emulator.
Configuring Raspberry Pi clients#
Open Raspberry PI terminal and apply “sudo su”
- Apply “nano /etc/sysctl.conf” command and edit the file by adding the following comment
net.ipv4.ip_forward=1 - To save and Exit
[Ctrl] + X, then chose yes or no - Apply “nano /etc/sysctl” command
- Then add the following comments
a. IP_DYNIP=”no”
b. IP_TCP_SYNCOOKIES=”yes”
c. IP_FORWARD=”yes” - Follow step 3
- Apply “nano /etc/dhcpcd.conf” a. change the ”static routers” to NetSim Server IP as shown in the below image
- Apply “route” command
- Apply “ip r del <network ip>/24"
Example: ip r del 192.168.0.0/24 - Apply “ping <any ip within the network>”. Example: ping 192.168.0.202
Setting up the network for client systems communicating across the network#
Devices communicating across networks can be connected to NetSim Emulator. This is achieved by connecting the system running NetSim to the routers which connect to the client machines taking part in communication.
System Configuration#
Connecting devices across network to NetSim emulator involves configurations at the router and in the NetSim Emulator system. There is no configuration required in the client systems communicating across the network, unlike the case of emulation within the same network.
- The System running NetSim Emulator will require two or more Network Interface Cards (NICs) to connect to different networks.
- Static routes should be set to route packets to specific Network Interfaces as they come in.
- Static routes should be set for routing any external network traffic to the interface that connects to NetSim emulator.
Consider the network shown in the figure below Figure.
PC 1 and PC 2 are connected to Router 1 and Router 2 respectively. NetSim Emulation PC connects to Router 1 in one of its interface and Router 2 in the other.
To send packets exchanged between PC1 and PC2 via NetSim Emulator, following settings are to be done:
Router 1
Route is added to send any packet to PC 2(192.168.4.2), to NetSim Emulator interface that is connected to it. (Interface with IP 192.168.1.2)
Router 2
Route is added to send any packet to PC 1(192.168.2.2), to NetSim Emulator interface that is connected to it. (Interface with IP 192.168.3.2)
NetSim Emulator
Route is added to send any packet to PC1(192.168.2.2), to its first interface (192.168.1.2)
Route is added to send any packet to PC2(192.168.4.2), to its second interface (192.168.3.2)
After performing the above settings, packets from PC 1 to PC 2 will take the following route:
PC 1 -> NetSim Emulator Interface 1 -> NetSim Emulator Interface 2 -> PC 2
And vice versa for packets from PC 2 to PC 1.
Performing Multicast Emulation#
IP multicast is a method of sending Internet Protocol (IP) datagrams to a group of interested receivers in a single transmission. It is the IP-specific form of multicast and is used for streaming media and other network applications.
NetSim emulator allows sending real traffic via the virtual network modelled in its environment. The real packets will experience the effect of the network conditions modelled in NetSim's virtual network in addition to the real network. This is usually achieved by setting the system hosting NetSim emulator as the gateway in the systems that are the sources of traffic.
Consider the following network setup where there are two systems running JPERF client and server applications and one system running NetSim emulator.
In the above network the gateway/nexthop of System 1 (and system 2 if traffic is bi-directional) needs to be set as System 3 for packets to reach NetSim Emulator prior to reaching the destination. NetSim can then take care of sending the real packets over the virtual network modelled in its design environment.
However, this works only in case of simple application models such as Unicast. In case of application models such as Multicast NetSim offers different techniques to ensure that the packets go through the emulated network prior to reaching the destination devices.
NetSim provides a Multicast Emulation Client application specifically to perform multicast emulation. This application can be found in the install directory of NetSim within as shown below:
Following is an example related to performing multicast emulation in NetSim. This example involves 4 real PC's
System Setup:
- SYSTEM 1 - NetSim Emulator (IP:192.168.0.34)
- SYSTEM 2 - Source (iperf Client) (IP:192.168.0.11)
- SYSTEM 3 - Destination 1 (iperf server 1) (IP:192.168.0.36)
- SYSTEM 4 - Destination 2 (iperf server 2) (IP: 192.168.0.19)
- All 4 systems must be in a single network.
System 1:
- Install NetSim Standard version including Emulator License
- Run NetSim in Administrative Mode, open Internetworks create a scenario as shown below Figure
- Create Multicast Emulation with following properties:
- Application Method: Multicast
- Application Type: Emulation
- Device Count: Count of devices which act as multicast server and client. 3 in this case (excludes the system hosting NetSim emulator, includes the Iperf client and two Iperf servers)
- Device ID: The ID's of the virtual devices representing the multicast clients and servers.
- Multicast Dest Address: The multicast IP address to which nodes are listening.
- Device Real IP: The IP Address of all the systems involved in Multicast (Excluding the system running NetSim emulator)
- Destination Real IP: The multicast IP Address
- Source Port: Can be set to 0.
- Destination Port: The port to which the server is listening.
- Configure all other systems in the Network and the perform simulation.
- Set IGMP status as true under Network Layer of all nodes.
- Run the simulation.
System 2:
- Copy Multicast Emulation Client folder from NetSim installation directory to the current system.
E.g.: C:\Program Files\NetSim Standard\MulticastEmulationClient - Run iperf with the following command in Admin Mode:
iperf -c 224.0.1.2 -u -i 1 -t 1000 - Run multicastEmulationclient in client system in command prompt in admin mode:
Command:
MulticastEmulationClient.exe <Client system Ip> <Emulation server Ip> <Multicast Ip> <port>
System 3 and System 4:
- Copy Multicast Emulation Client folder from NetSim installation directory to the current system.
E.g.: C:\Program Files\NetSim Standard\MulticastEmulationClient - Run jperf with the following command in Administrative Mode:
iperf -s -B 224.0.1.2 -u -i 1 - Run multicastEmulationclient in client system command prompt in admin mode:
Command:
MulticastEmulationClient.exe <Client system Ip> <Emulation server Ip> <Multicast Ip> <port>
Now perform Step 5 of System 1 i.e. Run the simulation in System 1. User will be asked to Enter an option to choose local IP while simulation. Please enter the option that displays the server-IP given as <multicast ip> for MulticastEmulationClient.exe. In this example its 192.168.0.34.
On successful completion of Simulation, NetSim provides performance metrics in the Simulation Results dashboard.
Setting up the network for Database PostgreSQLEmulation#
Devices running Database Management Systems such as PostgreSQL can be connected to NetSim Emulator. This is achieved by connecting the systems running the database server, the database web client and the system running NetSim Emulator to a switch.
System Configuration#
Connecting devices involved in database application to NetSim emulator involves configurations at both the systems that run the database server and the web client.
- Static routes should be set to route all outgoing packets to the system running NetSim Emulator.
Consider the network shown in the figure below Figure
System 1, System 2 and System 3 are connected to a L2 switch and are part of the same network.
To send packets exchanged between System 1 and System 2 via System 3(NetSim Emulator), following settings are to be done:
System 1
Route is added to send any packet to System 2(192.168.0.154), to NetSim Emulator interface that is connected to it. (Interface with IP 192.168.0.22)
System 2
Route is added to send any packet to System 1(192.168.0.21), to NetSim Emulator interface that is connected to it. (Interface with IP 192.168.0.22)
After performing the above settings, packets from PC 1 to PC 2 will take the following route:
System 1(PgAdmin Server) -> System 3(NetSim Emulator)-> System 2(PgAdmin WebClient)
And vice versa for packets from System 2 to System 1.
Steps to Start generating Network Traffic#
- Start PgAdmin application in System 1 and create a database with 100000 Records in it.
- Now open PgAdmin application in System 2 and connect to the database created in System 1. In the example shown below, we are attempting to retrieve the records from a large csv file.
Steps to configure application for NetSim Emulation#
- Once the database connection is established, In System 3, create a simple scenario in internetworks as shown below:
- Configure an Emulation Application from Wired Node 2 to Wired Node 3 as shown below:
- Configure an Emulation Application from Wired Node 3 to Wired Node 2 as shown below:
The above settings will ensure that packets from System 1 to System 2 and vice versa will be sent via NetSim Emulator.
Results and Analysis#
- Start Simulation in NetSim
- Perform any query on the database while NetSim simulation is running.
- Analyse the impact of flow of the packets through the network designed in NetSim based on the time taken for the query response.
- The pcap log files such as All Network Packets Capture, Dispatched to Emulator, Reinjected from Emulator, Not Dispatched to Emulator that are accessible from the NetSim results dashboard after the simulation is over, can be used for further analysis.
Setting up the network for GeoServer Application Emulation#
Devices running Database Management Systems such as PostgreSQL can be connected to NetSim Emulator. This is achieved by connecting the systems running the database server, the database web client and the system running NetSim Emulator to a switch.
System Configuration#
Connecting devices involved in database application to NetSim emulator involves configurations at both the systems that run the database server and the web client.
- Static routes should be set to route all outgoing packets to the system running NetSim Emulator.
Consider the network shown in the figure below Figure
System 1, System 2 and System 3 are connected to a L2 switch and are part of the same network.
To send packets exchanged between System 1 and System 2 via System 3(NetSim Emulator), following settings are to be done:
System 1 Route is added to send any packet to System 2(192.168.0.154), to NetSim Emulator interface that is connected to it. (Interface with IP 192.168.0.22)
System 2 Route is added to send any packet to System 1(192.168.0.21), to NetSim Emulator interface that is connected to it. (Interface with IP 192.168.0.22)
After performing the above settings, packets from PC 1 to PC 2 will take the following route:
System 1(Geo Server) -> System 3(NetSim Emulator)-> System 2(Geo WebClient)
And vice versa for packets from System 2 to System 1.
Steps to Start generating Network Traffic#
- Start GeoServer application in System 1
- Now access GeoServer via web browser in System 2 by specifying IP address:
GeoServerPort//Geoserver/browser. Eg:192.168.0.21:2020/Geoserver/browser
Steps to configure application for NetSim Emulation#
- Once the database connection is established, In System 3, create a simple scenario in internetworks as shown below Figure
- Configure an Emulation Application from Wired Node 2 to Wired Node 3 as shown below
- Configure an Emulation Application from Wired Node 3 to Wired Node 2 as shown below:
The above settings will ensure that packets from System 1 to System 2 and vice versa will be sent via NetSim Emulator.
Results and Analysis#
- Start Simulation in NetSim
- Try to access specific regions of the map by zooming in and other operations to generate live network traffic.
- Analyse the impact of flow of the packets through the network designed in NetSim based on the time taken for the map to load.
- The pcap log files such as All Network Packets Capture, Dispatched to Emulator, Reinjected from Emulator, Not Dispatched to Emulator that are accessible from the NetSim results dashboard after the simulation is over, can be used for further analysis.
Setting multiple Virtual Machines (VM) to act as Nodes for Emulation#
VMs sharing the same network as the host#
A computer on which one or more virtual machines are running is defined as a Host Machine. Each virtual machine is called a Guest Machine. In this scenario, we have 3 VMs running in a Host Machine – VM1, VM2 and VM3. Users can run NetSim License server in any system connected to the network in which Host Machine is running.
Now right click on each VM and select Settings. Click on Network Adapter, and select “Bridged: Connected directly to the physical network”. Also enable the “Replicate Physical network connection state”.
An advantage of this technique is that, if the license server is running in another system, connected to the same network as the original host, then NetSim running in the VM can obtain the licenses
VMs sharing a network but insulated from the host network#
A computer on which one or more virtual machines are running is defined as a Host Machine. Each virtual machine is called a Guest Machine. In this scenario, we have 3 VMs running in a Host Machine – VM1, VM2 and VM3. NetSim License server is running in one of these 3 VMs.
If user needs to create an internal network which is segregated from host network, follow the steps
- Right click on each VM and select Settings.
- Click on Network Adapter, and select “Custom: Specific Virtual network”
- Select “VMnet8 (NAT)”
User can modify the Subnet IP and Subnet Mask to suit their own preference.
The disadvantage of this technique is that, if the license server must compulsorily run in the VM for NetSim to obtain the licenses.
NetSim Emulator interfacing with Kubernetes Clients#
Objective: Kubernetes Client running on the docker generates application traffic destined for Kubernetes Client. This traffic is sent through NetSim Emulator in which an equivalent virtual network is created. Thereby test the performance of your real application when transported over the virtual network.
Installation
For installation and running Kubernetes and Docker on Windows please refer
https://support.tetcos.com/support/solutions/articles/14000124321-how-to-run-netsim-on-windows-container
https://www.youtube.com/watch?v=cgYOpw5XLtk
Traffic flow diagram#
Lab Setup#
- 3 Systems
- Kubernetes Clients
- Pods IP Address: 10.10.10.1
- Host IP Address: 192.168.0.100
- Kubernetes Server
- Pods IP Address: 10.10.10.2
- Host IP Address: 192.168.0.102
- NetSim Emulation server (IP Address: 192.168.0.101
- Kubernetes Clients
- Kubernetes Client/server applications running on respective system. They be any application. In this example, we run the jperf application on client and server.
- Static routing in the lab setup.
- CLIENT POD:
- Run CLI docker in administrator mode and add a route to Server Pod. This must be in such way that the traffic generated from the Client Pod must flow through the Emulation server.
- Command Windows: route add 10.10.10.2 MASK 255.255.255.255 192.168.0.101 METRIC 1
- SERVER POD:
- Run CLI docker in administrator mode and add a route to Client Pod. This must be in such way that the traffic generated from the Server Pod must flow through the Emulation server.
- Command Windows: route add 10.10.10.1 MASK 255.255.255.255 192.168.0.101 METRIC 1
- CLIENT POD:
Steps to configure the application for NetSim Emulation#
- Once the Client Pod and Server Pod connection is established, In NetSim Emulation server, create a simple scenario in internetworks as shown below Figure.
- Configure an Emulation Application from Wired Node 1 to Wired Node 2 as shown below:
The above settings will ensure that packets from System 1 to System 2 and vice versa will be sent via NetSim Emulator.
Results and Analysis#
- Start Simulation in NetSim
- Analyze the impact of the flow of the packets through the virtual network designed in NetSim
- The pcap log files such as All Network Packets Capture, Dispatched to Emulator, Reinjected from Emulator, Not Dispatched to Emulator that are accessible from the NetSim results dashboard after the simulation is over, can be used for further analysis
Model Features#
Working of an Emulation Application in NetSim#
Note: The following explanation is provided assuming that you have performed all necessary configuration required to divert network traffic via the system running NetSim Emulator. (This is explained in section 9 of the User Manual.)
The following parameters are specific to Emulation Application in NetSim:
Source_Real_IP
Source_Port
Destination_Real_IP
Destination_Port
Unlike Simulation, if users want to connect real devices running live applications to the simulator, then Emulation component is required. The Emulation Application in the traffic generator allows users to pump in real traffic into the Simulator.
The real application is mapped using the source and destination IP addresses that we set in the Emulation Application.
Various combination of Emulation Parameters are as follows:
Device Specific Emulation:
Example 1:
SOURCE_REAL_IP = 192.168.0.151
SOURCE_PORT = 0
DESTINATION_REAL_IP = 192.168.0.202
DESTINATION_PORT = 0
Dispatches all packets with the source real IP 192.168.0.151 and destination real IP as 192.168.0.202, into the Simulator.
Example 2:
SOURCE_REAL_IP = 192.168.0.151
SOURCE_PORT = 0
DESTINATION_REAL_IP = 0.0.0.0
DESTINATION_PORT = 0
Dispatches all packets from source real IP 192.168.0.151 regardless of whatever is the destination real IP, into the Simulator.
Example 3:
SOURCE_REAL_IP = 0.0.0.0
SOURCE_PORT = 0
DESTINATION_REAL_IP = 192.168.0.202
DESTINATION_PORT = 0
Dispatches all packets to destination real IP 192.168.0.202 regardless of whatever is the source real IP, into the Simulator.
Example 4:
SOURCE_REAL_IP = 0.0.0.0
SOURCE_PORT = 0
DESTINATION_REAL_IP = 0.0.0.0
DESTINATION_PORT = 0
Dispatches all packets that are reaching the Emulator Device regardless of whatever is the source or destination, into the Simulator.
Application Specific Emulation
Example 1:
SOURCE_REAL_IP = 192.168.0.151
SOURCE_PORT = 5004
DESTINATION_REAL_IP = 192.168.0.202
DESTINATION_PORT = 6245
Dispatches all packets with the source real IP 192.168.0.151, source Port No 5004, destination real IP as 192.168.0.202 and destination Port No 6245 into the Simulator.
Emulation Specific Metrics
On running an Emulation Application Users can optionally obtain the following log files which are Wireshark compatible .pcap files:
All_Network_Packets - Log of all packets flowing via the system running NetSim Emulator.
Dispatched_To_Emulator - Log of packets for which were sent to NetSim based on Emulation Application is configured in NetSim.
Reinjected_From_Emulator - Log of packets that successfully reached the virtual destination node in NetSim Simulator and was re-injected into the network.
Not_Dispatched_To_Emulator - Log of packets flowing via the system running NetSim emulator but not dispatched to emulator All_Network_Packets minus Disptached_To_Emulator)
Delay measurement when pinging through NetSim Emulator#
Pinging through NetSim emulator takes only one direction delay, if you have set only one application with Ping Source IP and ping Destination IP. This is because PING is a two way application and constitutes PING_REQUEST and PING_REPLY. For ping to take round trip delay users must configure two Emulation Applications, one for forward PING_REQUEST and other for the reverse PING_REPLY.
For example: If you are running a ping from the IP 192.168.0.151 to an IP 192.168.0.202 the time take will normally be around 1ms.
Now we create a network scenario in NetSim similar to the screenshot shown below Figure.
We reset the propagation delay in both the wired links to 5 µs.
We configure an Emulation application between the wired nodes with the source and destination real IP specified, as shown below:
On running the simulation, you will observe the variation in the time taken to get the ping reply in the source system, as shown below:
Ping packets has experienced an additional delay of 10µs which is a sum of the delay in both the links.
The additional delay experienced by ping packets is not 20µs because, the application that we have configured applies to only the Ping Request Packets which has the Source IP as 192.168.0.151 and Destination IP as 192.168.0.202.
The Ping Reply Packets has the Source IP as 192.168.0.202 and Destination IP as 192.168.0.151, for which we have not configured any application.
For the ping to take the round trip delay, we will have to configure one more application for the reverse traffic. On adding an application for the reverse traffic as shown below:
We will now be able to see round trip delay being experienced by the PING application, as shown below:
Ping experiences an additional overall delay of 20ms, which is the sum of the delays experienced by Ping Request and Ping Reply (10ms + 10ms).
Jitter in NetSim Emulations#
Jitter is defined as a variation in the delay of received packets. Let us suppose at the sending side, packets are sent in a continuous stream with the packets spaced evenly apart. Due to network congestion, improper queuing, or configuration errors, this steady stream can become lumpy, or the delay between each packet can vary instead of remaining constant. This variation in delay is ‘jitter’. While there are many ways of measuring this variation, in NetSim ‘jitter’ is measured as the statistical variance of delay. Variance is defined as the square of deviation from the mean.
Introducing Jitter using Background traffic#
Background traffic can be used to test the performance of applications when link bandwidth is consumed by other traffic. It can also be used to induce jitter for testing real-time applications.
The Background traffic in NetSim can be modelled as a Poisson process in which bursts of data of a fixed size are transmitted at an average rate such that the link will be occupied at the specified link utilization rate. Because it is a random process, over short periods the actual background traffic link utilization rate may vary from the configured value. The rate of arrival of background traffic frames affects the jitter. Larger number of background packets induce greater jitter in competing traffic. In NetSim, the way to increase the number of background packets arriving is to reduce the inter-arrival time of that application, as explained in the link
https://tetcos.freshdesk.com/support/solutions/articles/14000067807-how-do-i-introduce-jitter-in-netsim-simulations-emulations-
Featured Examples#
- Example 1: PING (One way Communication)
- Example 1: PING (Two way Communication)
- Example 2: Video(One way Communication)
- Example 3: File Transfer using FileZilla (One-way)
- Example 4: Skype (Two way Communication)
- Example 5: Using JPerf
- Example 6: Simple Military (TDMA) Radio Use Case
- Providing pcap file as input to NetSim Emulator
Trouble shooting#
“Ping: Request timed out” in DTDMA Radio Networks#
This is specific to scenarios which used DEMAND BASED slot allocation in the MAC layer and having multiple emulation applications. When multiple systems trying to ping, the slot allocation methodology, causes delays that exceed the TTL of ping packet. A simple way to overcome this problem is to set the slot allocation technique as ROUNDROBIN.
It may happen that even after setting ROUNDROBIN as the slot allocation technique, a user could see the “Ping: Request timed out” error. This is due to high-rate traffic flows of non-emulation applications flowing through the emulator system. For example, consider a scenario with 4 systems A, B, C and D, such that
- A is the source system. The system sending Ping Request.
- B is the emulation server where NetSim is run.
- C is the destination System. The system sending Ping Reply.
- D is another system that is not a part of the Emulation set up under study
In this example, A pings C with traffic flowing through B. If simultaneously there is other traffic flowing from A to D (applications that are not part of Emulation set-up under study), then this traffic would also flow via emulator system due to static route setting. This will cause delays and the ping packets may then exceed the TTL. To avoid this set static route to a particular Host system instead of adding static route based on Network. In this same example, say the systems A, B, C and D are in the network 192.168.0.0/24, with IP addresses 192.168.0.2, 192.168.0.3, 192.168.0.4 and 192.168.0.5 respectively. Then user should not set
route add 192.168.0.0 MASK 255.255.255.0 192.168.0.3 METRIC 1
but instead, add the host specific static route
route add 192.168.0.4 MASK 255.255.255.255 192.168.0.3 METRIC 1
Latest FAQs#
Up to date FAQs on NetSim’s Emulation library is available at
https://tetcos.freshdesk.com/support/solutions/folders/14000115083