L2TP: Implementation and Operation (The Addison-Wesley Networking Basics Series) - Softcover

Shea, Richard

Softcover

ISBN 10: 0201604485 ISBN 13: 9780201604481

Publisher: Addison-Wesley Professional, 1999

Synopsis

L2TP: Implementation and Operation is an essential resource for anyone who works with L2TP and Virtual Private Networks. Written for developers and network managers, this book provides an overview of the protocol, a detailed explanation of L2TP architecture, a step-by-step guide to its implementation, and information on L2TP security and management.
Throughout, the book highlights implementation tips, drawn from the author's extensive practical experience, that will help you avoid potential problems and maximize the benefits of L2TP.

About this title

About the Author

Richard Shea was a member of the founding team of New Oak Communications (now merged into Nortel Networks), where he developed PPTP, L2F, and L2TP support. He continues to work with Nortel on VPN/Extranet access products. In addition, he has worked on such technologies as FDDI, Ethernet switching, PPP remote access, and IP routing.

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From the Back Cover

Layer 2 Tunneling Protocol (L2TP) has emerged as a key technology in the construction of Virtual Private Networks. L2TP provides remote access capabilities to organizations using public networks for internal, private activities. It allows a corporation to retain the advantages of a private network--privacy of communication, access control, and company addressing--while reducing the need to invest heavily in networking infrastructure.

L2TP: Implementation and Operation is an essential resource for anyone who works with L2TP and Virtual Private Networks. Written for developers and network managers, the book provides an overview of the protocol, a detailed explanation of L2TP architecture, a step-by-step guide to its implementation, and information on L2TP security and management.

You will find useful background on the OSI model, the underlying PPP technology, how L2TP tunnels PPP, and the L2TP LAC and LNS Layer 2 roles. In addition, the book contains detailed information on such topics as:

• L2TP deployment models
• L2TP tunnel structure, terminology, and function
• Protocol state machines
• Tunnel authentication and initiation
• Header and control message format, including AVP
• Control channel dynamics
• Session setup
• Proxy authentication
• Data handling, including Multilink PPP
• L2TP security
• SNMP management of L2TP networks
• Comparisons with L2F, PPTP, and other VPN technologies

Throughout, the book highlights implementation tips, drawn from the author's extensive practical experience, that will help you avoid potential problems and maximize the benefits of L2TP.

0201604485B04062001

Excerpt. © Reprinted by permission. All rights reserved.

Remote access has become more and more popular as organizations rely increasingly on their data networks. The increasing popularity of telecommuting and the numbers of individuals who are mobile are two strong factors in this trend.

In order for organizations to provide traditional remote access, they must research and plan their use and make sizeable capital investments in infrastructure. To begin with, an organization needs to predetermine call capacity because the number of calls that can be simultaneously terminated is a factor in deciding what level of remote access device and how many T1 lines are purchased. The organization's call capacity must be increased to allow for the remote access connections to be made. Remote access connections are generally made via dedicated T1 lines (or T3 lines for very large organizations) connected to the remote access equipment. Next there is the purchase of the remote access equipment consisting of a device that terminates T1 or T3 lines on one side and has a connection to the organization's private network (typically Ethernet) on the other side.

Traditional remote access is inflexible, inefficient, and inadequate for accommodating evolving broadband technologies. These technologies provide dedicated access to an Internet Service Provider (ISP), forcing the remote user to tie up his or her traditional phone line to access the private network of an organization. When the legacy phone network is used for remote access, the costs incurred per connection are based on the same rules that are used for voice communications. For mobile users, establishing a remote access connection may mean incurring long distance costs. In addition, evolving broadband communication technologies such as cable modem and Asymmetric Digital Subscriber Line (ADSL) cannot be supported by traditional remote access. By supporting traditional remote access, organizations also incur the ongoing costs involved in supporting the remote access devices, including the upgrade of these devices as technology changes. One good example of why this is a problem is the recent increase in analog connection speeds to 56K access. When the 56K connection speed was first introduced, there were two methods of signaling. Private organizations and Internet Service Providers (ISPs) could not be sure they were choosing the right signaling versions, and only later did equipment become available that could support both 56K signaling methods.

The Layer 2 Tunneling Protocol, or L2TP, is aimed squarely at lifting the physical connection burden from the organization. The traditional remote access system is split into two halves. One half is responsible for terminating the physical connections, and the other half provides access to the private network. Conceptually, a line is drawn down the middle of a traditional remote access device; half of the device provides physical call connections, and the other half provides access to the private network communicating over L2TP. With L2TP, analog modem, Integrated Services Digital Network (ISDN), and ADSL connections can be physically terminated by an ISP, and the user data can be carried to a device at the edge of an organization's private network. L2TP client software can also be used to make virtual connections all the way from the remote user device (that is, a PC) to the organization's private network in such a way that the remote user's physical connection is completely independent.

Although the outsourced remote access model is the starting point for deploying L2TP, other applications are possible. Essentially any time that running Point-to-Point Protocol (PPP) between two entities over a non-point-to-point connection would be advantageous, L2TP should be used to provide that functionality.

This book provides details of L2TP for the individual who will be implementing L2TP in a data communications device. A history of L2TP is also provided, along with comparisons to the protocol's two predecessors, L2F and PPTP. Implementation tips are provided to cover those areas of use that are not readily understandable solely from reading the L2TP technical specification.

Audience

There are two audiences for this book. The primary audience is those who will be writing L2TP code. The book attempts to provide tips, give history, and logically explain and lay out the architecture for L2TP and the crucial and sometimes subtle interaction between L2TP and the PPP software running over it. The other audience for this book is those considering L2TP for their Virtual Private Network (VPN) deployment. The early chapters on the basics of L2TP and the discussion of security and management will be of particular interest to this reader.

Organization

The first three chapters are geared to a somewhat general audience. L2TP implementers may simply ignore these chapters if they wish to focus only on the details of L2TP implementation. Chapters 4-10 provide the details of L2TP implementation. These chapters may be skimmed by the reader with only a general interest in the details of the protocol itself. Special attention to Chapter 10 ("Security") should be paid even by the general reader. Chapter 11 ("SNMP Management") may also be of some interest to the general reader, and undoubtedly of interest to the L2TP implementer or the implementer of network management applications for L2TP. Chapter 12 provides resources for learning more about L2TP and gives information on what future work in L2TP is currently under consideration.

Edition details

• Publisher: Addison-Wesley Professional
• Publication date: 1999
• Language: English
• ISBN 10: 0201604485
• ISBN 13: 9780201604481
• Binding: Paperback
• Edition number: 1
• Number of pages: 304