Before starting a detailed discussion about protection and traffic restoration techniques, let’s clarify the terminology used in this book.
Figure 18-1 presents a generic service model with two dual-homed CE devices connected to a service provider (SP) IP/MPLS network. PE nodes provide the service itself (e.g., L3VPN), whereas Provider (P) nodes are used purely for transmitting packets between PE nodes. Additionally, the figure also shows various failure cases (nine in total) that can affect example traffic flow from left CE to right CE.
For the purpose of this book, failure categories (and corresponding protection categories) are classified as follows: