The first volume of TCP/IP Illustrated by Richard Stevens is wonderful. Ethernet frames, ARP, IP, ICMP, BOOTP, DHCP, UDP, TCP. Just make sure to get the original version.

What's wrong with the second edition?

Stevens' writing was engaging and pedagogically top shelf. Kevin Fall attempted integrating his coverage of newer protocols into the preexisting text, and unfortunately, completely butchered it.

I consider this the greatest technical book ever written.

Stevens gives himself a lot of competition with APUE tho.... hard to pick a winner between the two.

http://www.tcpipguide.com/free/t_toc.htm covers a lot of the basics.

You could do worse than Computer Networks by Tanenbaum