Asterisk error message

Does anybody no what the heck this message mean. Also, is there a tutorial, or ebook, that you may no of that can teach a person how to resolve log issues such as this. I mean, what does this mean.

[2015-07-10 16:26:52] WARNING[1844]: chan_sip.c:4015 retrans_pkt: Retransmission timeout reached on transmission cd673e07ff01d16c249fa245d79f4697 for seqno 1 (Critical Response) – See … nsmissions
Packet timed out after 32000ms with no response.

Have you checked the wiki page that is linked? It gives a pretty long explanation of what is going on and why this occurs. The gist being: We sent something and expected a response, we didn’t get it. This usually occurs because of NAT. Are you behind NAT? Do you have chan_sip configured for it? Do you have ports forwarded?