# Endpoint Agent TCP Support

ThousandEyes supports using [TCP](https://en.wikipedia.org/wiki/Transmission_Control_Protocol) as the communication protocol for Endpoint Agent scheduled tests. Two modes of operation are supported:

* SACK-based measurements
* SYN-based measurements

SACK-based network measurements require a single TCP connection to perform the measurement, whereas SYN-based measurements use a stream of up to 10 SYN packets, each being sent from a unique source TCP port. For this reason, SACK-based measurements are preferred. However, some networks do not support SACK, and so SYN is necessary.

For more information on the difference between SACK- and SYN-based measurements, see [Network Tests Explained](https://docs.thousandeyes.com/product-documentation/advanced-troubleshooting/network-tests-explained).

## TCP vs ICMP

There are a number of reasons to use TCP-based tests over [ICMP](https://en.wikipedia.org/wiki/Internet_Control_Message_Protocol)-based tests. Some of those reasons include:

* Large enterprise networks often block ICMP packets entirely to protect against device discovery.
* For networks running QoS or similar configurations, ICMP packets are often assigned a low priority, and packet loss/latency can occur.
* ICMP packets take different routes to TCP packets, and are often slower.

For more information on the difference between TCP and ICMP, see [Network Tests Explained](https://docs.thousandeyes.com/product-documentation/advanced-troubleshooting/network-tests-explained#end-to-end-network-overview).

## Prerequisites

TCP support is available for Endpoint Agent version 1.75.0 and above.

## TCP Setup

* For Mac users: No additional configuration is required for TCP support.
* For Windows users: See [Endpoint Agent Installation Reference](https://docs.thousandeyes.com/product-documentation/global-vantage-points/endpoint-agents/installing/endpoint-agent-installation-reference).

## Create TCP Scheduled Tests

See [Configure Scheduled Tests](https://docs.thousandeyes.com/product-documentation/global-vantage-points/endpoint-agents/configuring/configure-scheduled-tests) for instructions on creating tests, and [Endpoint Agent Test Settings Reference](https://docs.thousandeyes.com/product-documentation/global-vantage-points/endpoint-agents/configuring/endpoint-test-settings-reference) for specific configuration options.