Bandwidth reservations are an essential tool that you can use to do the following:
Avoid link congestion in networks with high-volume traffic, such as ISP backbones.
Ensure that the most critical applications have their bandwidth resources available.
This chapter covers the control plane required to perform bandwidth reservations. To date, the only protocol that is capable of actually reserving bandwidth in a network is RSVP-TE. Most forwarding plane details—in particular, fine-grained mapping of certain traffic to certain LSPs—are specific to each platform and beyond the scope of this book.
This book does not cover DiffServ-TE. It is not widely deployed.
The Traffic Engineering (TE) link constraints that are discussed in Chapter 13 are very simple, and are represented by single numbers. In this chapter, you will discover more complex TE use cases, with composite TE link attributes such as bandwidth.
The next TE link characteristic is bandwidth. Bandwidth is a little bit special. It is no longer a single attribute, but a set of attributes that you can find in the IGP’s link-state databases, in the Traffic Engineering Database (TED) and in the RSVP-TE messages.
Let’s have a look at the different attributes that comprise the TE bandwidth.
This is the physical interface bandwidth (e.g., 1.25 GByte/s for a 10GE interface). Typically, this parameter ...