Introduction

In my career, telecommunications came into existence in the beginning of the 1970s. In high school, the army, and later in college, where I had my first contact with big and mini computers, I made my first attempts to grasp the technology. The emerging LANs in the 1980s, bridges, decentralized computing, change of computer generations, Token Ring, and, of course, CSMA with all flavors and modifications, and the emerging IP with its promising end-to-end versus hop-by-hop networking, were among the most intriguing events in my career. The phenomenon of the Internet, the super-media, during the last decade of the 20th century, has without a doubt been one of the principal, not only technical, but also social, events for generations that still stirs my curiosity .

The remote access to corporate resources, located far away from your location, always amazed and fascinated me. I remember when, at the beginning of the 1980s, I was able to not only dial in from Plovdiv, but to read my inbox located on a server in Sofia...I was the happiest man in the world.

NOTE

Sofia is the capital of Bulgaria. Plovdiv is the second biggest city in Bulgaria. The distance between the two cities is about 150 km.

I always wanted to write this book. Years and years of looking at computer screens always wondering if it is possible to put together a concise description of all these numbers , abbreviations, and symbols. Meanwhile, I was always collecting pieces here and there, writing short manuals for myself . Working in the remote access environment at Cisco, I finally had the chance to write this book, which started from an article about ISDN troubleshooting one night in November 2000. (The article was published in the Cisco Packet Magazine in Q2 2001.) Brett Bartow's proposal for writing a book about remote access troubleshooting came just in time.

Remote access is about buckets of technologies. Remote access is about how to reach the remote LAN. The uniqueness of working on remote access is the opportunity to enhance your knowledge and to design, implement, configure, and support the variety of technologies used for remote access solutions today. Your troubleshooting ability changes based on your position or location in the classical trio of remote accesswhether you are a remote user , a service provider site, or at the corporate site. As a troubleshooting engineer, maybe the best position you can choose is the last one. The uniqueness of the enterprise remote access is that you have limited visibility into the cloud, but you can see both ends of the remote access service and you control the headend side. Of course, troubleshooting is maybe more about hunches, about right-and-wrong, and about experience, but knowledge definitely helps. Combined with passion, it can make troubleshooting a genuine craft.

One of the main challenges of this book was to provide the reader with the minimum technology background sufficient to understand the technology basics. This challenge came from the fact that numerous studies and books published in the last 20 to 30 years have produced an abundance of information, which is almost impossible to synthesize in a limited number of pages for each technology in this book. Combining this information with trouble-shooting techniques and recommendations was another challenge that this book needed to meet.

This book was written with appreciation of generations of scientists and engineers , constantly developing standards, coding and signaling schemes, hardware/software designs, and config-urations to provide remote users with full access to their resources, sometimes thousands of miles away. This book was certainly written with an appreciation to Cisco's contribution to the technology over the last decade.

This book is written with appreciation to remote access solutions, where wired networks made possible the most common design solutions today. That's why Part I concentrates on the fundamentals, whereas Parts II, III, and IV deal with commonly available technologies, such as dial, ISDN, and Frame Relay.

However, we are about to witness and participate in a significant change in the existing remote access solutions. Panta rhei as every technology continuously changes its features, the remote access environment is no different. Today's VPN (in all flavors) is only the first wave of moving away from legacy remote access, which is primarily based on permanent circuits. That's why Part V, "VPN," is a bridge to the futuretowards using locally available Internet services to access the corporate resources remotely.

The evolving mobility adds a new dimension to remote access technologies. Overcoming the tyranny of cables will transform remote access into ubiquitous access sooner rather than later.