TCP/IP. how much changes have been done last 20 years ?

[lostinxlation]

Hi,
I'm looking at buying some TCP/IP books and found some good deal, but they were published in the early to mid 90s. I understand how TCP/IP works in general, but I don't know how much of TCP/IP was changed last 20 years and whether these books can give me a depth in today's TCP/IP.
I tend not to buy old books on the networking stuffs since it's a rapidly changing subject, but a basic principle like TCP/IP may not have been changed and old books may still work well.

Does anyone have an idea ?

 

[bluehole]

After IP-V4 IP-V6 is the new concept, which is added. for reference purpose OLD books can do. But if you want IP-V6 then go for New books. It is purely my opinion.