Chapter Review and Summary

---

Traffic engineering for MPLS consists of four elements: measurement, characterization, modeling, and putting traffic where you want it to be. In performing traffic placement, MPLS can use either of the traffic-engineering protocols named in discussions about advanced signaling (CR-LDP or RSVP-TE). Of the two protocols, RSVP-TE appears to be more dominant, but it costs more in bandwidth; it is like paying for a police escort whenever and wherever you travel.

The rest of traffic engineering is far from simple. You must measure, characterize, and model the traffic that you want. Once you have the information that you need, you can then perform mathematical calculations to determine how much traffic can be placed on your tunnel.

The mathematical processes involved in engineering traffic are much like those involved in balancing a checkbook. You should never allow the balance of your available resources to go into the “red,” or negative, area.

The tradeoff decisions are difficult to make: Can you over-provision (over-book) your tunnel and just hope that rush-hour traffic never comes your way? In the event of a failure, where is the traffic going to go?

Knowledge Review 

Answer the following questions.

1. Name the four elements of traffic engineering.

2. Name two models of bandwidth provisioning.

3. What is the primary advantage of over-provisioning a circuit?

4. What are the primary disadvantages of under-provisioning a circuit?

5. Preserving bandwidth when there are no active transmissions on a circuit is called what?

6. Overbooking a circuit and assuming that “rush-hour” traffic will not happen is called what?

Answers: 1. Measuring, characterizing, modeling, and moving traffic; 2. over-provisioning and under-provisioning; 3. excess bandwidth increases chances of achieving true QoS; 4. lack of bandwidth negatively affects both QoS and reliability; 5. silence suppression; 6. over-provisioning by 110 percent.

---