Version: 2017.3
public uint ResendTimeout ;

Description

Defines the maximum wait time in milliseconds before the "not acknowledged" message is re-sent. Default value = 1200.

It does not make a lot of sense to wait for acknowledgement forever. This parameter sets an upper time limit at which point reliable messages are re-sent.

using UnityEngine;
using UnityEngine.Networking;

public class ExampleScript : NetworkBehaviour { void Start() { ConnectionConfig myConfig = new ConnectionConfig(); myConfig.AddChannel(QosType.Unreliable); myConfig.AddChannel(QosType.UnreliableFragmented); myConfig.ResendTimeout = 1000; //1 sec } }