---
title: backend.socket.tcpi_rttvar
summary: null
url: >-
  https://www.fastly.com/documentation/reference/vcl/variables/backend-connection/backend-socket-tcpi-rttvar
---

**Type:** INTEGER  
**Access:** read-only

**Available in:** fetch

TCP round-trip time (RTT) variance for the backend connection in microseconds (µs).