Firstly replace chan_sip with chan_pjsip as chan_sip is no longer supported and is not present at all in the latest version of Asterisk.
If the problem still occurs, make sure that your network is working to the destination. As it says, this is caused by network problems which could include not having a route to the destination IP address.
If you are only using chan_pjsip, this may indicate your firewall failed to block an attack. If you are actually using chan_sip, as well, I imagine trying to bind them both to the same port might produce this sort of error, although it might fail at an earlier stage.