TABLE OF CONTENTS The operating of a protocol stack
The Application layer
The Transport layer
The Internet layer
The Logical Link Control layer
The MAC layer
The Physical layer
If you had taken a college-level data communications course in the early 1990s, you would have learned that a theoretical set of protocols developed by the International Standards Organization (ISO) would govern the language used for network message exchange for the foreseeable future. At that time, we were still unaware of the overwhelming impact the Internet would have on networking. The ISO s protocol stack the Open Systems Interconnect (OSI) stack has been largely overwhelmed by TCP/IP, the collection of protocols used by the Internet.
The only OSI protocols that are in wide use today are those in the lowest two levels in the protocol stack, where they have been merged into the TCP/IP protocol stack. Almost all network communications today are based on that combined set of protocols.
The purpose of this appendix is to provide an overview of the structure of the TCP/IP protocol stack and the major protocols at each layer. Details on the operation of those protocols most relevant to security issues can be found throughout the body of this book.
The protocols in a protocol stack are organized so that protocols that provide similar functions are grouped into a single layer. The original TCP/IP provided five layers (see Figure A.1). However, as mentioned...
