polarbear

i was considering this, but honestly have no idea because i have never flown before.
i am planning on taking this as my main pack for my 3 month walk of europe

http://www.thenorthface.com/opencms/...=NA&model=AM4J

but can i also bring this along as well? i mean take the pack as a carry on, and put this in my lap for the flight? or is that not allowed?

http://www.timbuk2.com/tb2/products/...stic-messenger

can i put one in overhead and keep one on me at all times?
or whats allowed and whats not?
any advice from seasoned airplane travelers?