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ctsTraffic has moved to GitHub! Please continue to follow us there at Thanks!

Version 2 has been released!

After a few years of customer feedback and development, we are happy to release a new major revision with more features, better reliability, and better scalability. See Downloads for details!


Client to Server Traffic (ctsTraffic) was developed by members of the Microsoft (R) Windows (R) Networking test team. It was initially designed at the end of Windows 7 and has been used to measure networking scenarios throughout Windows 8 and Windows Blue. We are now excited to be bringing this tooling to the open source community.

It is a utility to generate and validate the integrity of network traffic. It is a highly scalable client / server application with the ability to send and receive traffic in a variety of protocol patterns, utilizing a variety of API calling patterns. The protocol is validated in bytes sent and received for every connection established. Should there be any API failure, any connection lost prematurely, or any protocol failure in bytes sent or received, the tool will capture and log that error information.

ctsTraffic has been tested to scale down to small devices, scale up to large systems (effectively spanning across large #s of processors; large memory installations including multiple NUMA nodes; easily filling large network pipes including 10Gig and 40Gig connections), and scaling out to large numbers of simultaneous connections (tested up to 500,000 active TCP connections).

Information about the network traffic can be captured within an Excel-friendly format to facilitate graphing interesting properties of the network session; properties such as TCP bytes/second or UDP bits/second; UDP frames processed over time; UDP frames dropped over time; connection rates successfully established over time; failed connections over time.

Supported Features:

  • Servers service any number of connections from any number of clients
  • Allows for specifying the number of connections to maintain from the client
  • Allows targeting one or more servers by name or address
  • Allows binding or listening to specific addresses or ranges (e.g. only IPv6 addresses)
  • Allows for selecting the degree to which ctsTraffic should validate the TCP session (connection integrity or additionally data integrity)
  • TCP-specific
    • Allows for specifying the buffer sizes used in send & receive calls - including specifying a range to randomly select a buffer size
    • Allows for selecting from different Winsock API usage patterns
    • Allows for selecting from various TCP protocol patterns controlling send and receive patterns
    • Allows for throttling TCP connections to send at a specified rate
  • UDP-specific
    • Allows for controlling the bits/second being streamed from the server, processed on the client
    • Allows for controlling the frame to process the incoming stream
    • Allows for controlling the amount of buffering on the client before starting to process the stream
    • Allows for controlling how hard the client will work in looking ahead and requesting missing frames
  • Various logging options, including toggling whether to log to console
    • Text formatting or Csv formatting
    • Per connection details; error details; aggregate status details; UDP jitter details
    • Various logging options and verbosity, allowing greater levels of detail when required
    • Various scenario-specific options for customized environments

Setup Instructions:

Select the Downloads tab above. Copy ctsTraffic.exe to the client and server (no installation required - only a single binary).


Server-side usage
 ctsTraffic -Listen:<addr or *> [-Port:####] [CommonOptions] 

Client-side usage
 ctsTraffic -Target:<addr or name> [-Port:####] [-Connections:<####>] [-Iterations:<####>] [CommonOptions] 

An example of push-pulling data between a client & server across 100 concurrent connections (to be executed across 10 iterations -> therefore 100 x 10 == 1000 total connections before exiting).

 ctsTraffic.exe -Listen:* -Port:4444 -Pattern:pushpull 

 ctsTraffic.exe -Target:<server> -Port:4444 -Connections:100 -Iterations:10 -Pattern:pushpull 

Traffic visualization:

TCP Traffic visualization:

ctsTraffic allows the user to view (or log to raw text or Excel-friendly csv) TCP sessions at a specified time frequency with the following format:

TimeSlice: (seconds) cumulative runtime
Send & Recv Rates: bytes/sec that were transferred within the TimeSlice period
In-Flight: count of established connections transmitting IO pattern data
Completed: cumulative count of successfully completed IO patterns
Network Errors: cumulative count of failed IO patterns due to Winsock errors
Data Errors: cumulative count of failed IO patterns due to data errors

TimeSlice SendBps RecvBps In-Flight Completed NetError DataError
1.0 1292704 1280572 1 0 0 0
2.0 1263080 1286975 1 0 0 0
3.0 1299168 1286975 1 0 0 0
4.0 1263080 1286975 1 0 0 0
5.0 1299168 1286975 1 0 0 0
6.0 1406025 1285689 1 0 0 0
7.0 1154816 1389933 1 0 0 0
8.0 1263080 1132538 1 0 0 0
9.0 1406025 1439972 1 0 0 0
10.0 1299168 1286975 1 0 0 0

UDP Traffic visualization

ctsTraffic allows the user to view (or log to raw text or Excel-friendly csv) UDP sessions at a specified time frequency with the following format:

TimeSlice: (seconds) cumulative runtime
Bits/Sec: bits streamed within the TimeSlice period
Completed Frames: count of frames successfully processed within the TimeSlice
Repeated Frames: count of frames received multiple times within the TimeSlice
Attempted Retries: count of retries for missing frames within the TimeSlice
Stream Errors: count of invalid frames or buffers within the TimeSlice

TimeSlice Bits/Sec Completed Dropped Repeated Retries Errors
5.0 322480601 302845985 100 0 0 0
10.0 322228495 321991090 100 0 0 0
15.0 323469312 322750752 100 0 0 0
20.0 321824358 322043114 100 0 0 0
25.0 317864670 317394570 100 0 0 0
30.0 325481267 325794944 100 0 0 0
35.0 318986649 318903289 100 0 0 0
40.0 321614643 321634304 100 0 0 0
45.0 313759660 314113776 100 0 0 0
50.0 325671321 325474524 100 0 0 0

Last edited Jul 10 at 5:57 AM by khorton, version 7