- What is Label Switching?
- Why Use Label Switching?
- The ZIP Code Analogy
- Why A Label IS Not an Address
- How Label Switching is Implemented and How it Came About
- Clarification of Terms
- The Need for a QOS-based Internet
- Label Switching's Legacy: X.25 and Virtual Circuits
- MPLS: Status and Concepts
- Examples of Label and QOS Relationships
- Determination of the Physical Path Through the Network: The Label Switched Path (LSP)
How Label Switching is Implemented and How it Came About
Several methods are employed to implement label switching. For this book, we examine those that are deployed and those under consideration, concentrating on the MPLS specifications. As we will see, many of them are similar. Chapter 3 provides a taxonomy of these methods.
The concept of label switching has been around for a number of years, and several firms developed proprietary label switching schemes for their products. These schemes are covered in a companion book to this series, Advanced Internet Technologies, and are explained in a general way in Chapter 3. For this book, the cogent aspect of this discussion is to emphasize that the implementation of these proprietary approaches provided a wealth of experience and information about label switching. But the proprietary schemes are not compatible. Therefore, the Internet Engineering Task Force (IETF) set up a working group to establish a standard for the label switching technology. This standard is MPLS. We emphasize MPLS throughout this book with less emphasis on the proprietary label switching protocols, since the proprietary protocols will be replaced by MPLS.