"Old" books in some cases, but some protocols never age out! (some of below maybe did...)
Free books on my desk here at work/WPI, if unwanted I'll end up tossing:

(2005) Addison-Wesley "The Design and Implementation of the FreeBSD OS"
    I got glassy-eyed diving into most of this kernel,fsys,devices,IPC,etc gore.

(2003) ORA/O'Reilly "DNS & BIND Cookbook" (bind8,9)  Cricket Liu 200+ pg paperback

(2003) ORA "LDAP System Administration"  Gerald Carter 290pg paperback

(1994) Addison-Wesley "TCP/IP Illustrated, Vol. 1"  W. Richard Stevens  550pg hardcover

(1990) Prentice Hall "UNIX Network Programming" W. Richard Stevens 750pg hardcover
       ( things like fork/exec ; basic I/O ; FIFO,IPC,Sockets,TLI...ending in rlogin :) TOO OLD

(1993) ORA "sendmail"   (  v8 )   too old AND too nasty,
though I like the Intro sec1+2 titles  "MUA vs MTA" and "Why is sendmail so complex?"