# 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.


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs.thousandeyes.com/product-documentation/global-vantage-points/endpoint-agents/endpoint-agent-tcp-support.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.