from the layers-upon-layers dept.
prostoalex writes "Eugene Blanchard made his Introduction to Data Communications (also known as Introduction to Networking) available for free. The book covers a broad variety of topics such as RS-232, Ethernet, RF, TCP/IP and many other topics in its 63 chapters. This is a valuable reference and read for those just starting to understand networking and data communications as well as seasoned professionals in the field."
Never ask two questions in a business letter. The reply will discuss
the one you are least interested, and say nothing about the other.