Junos Enterprise Routing, 2nd Edition

Chapter Review Answers

1. Answer: B. Only the Integrated Services (IntServ) model made use of control plane signaling for resource allocation.

2. Answer: A. In the DiffServ model, a BA is a collection of packets with a shared code point. It is expected that each node will have the same PHB for a given BA, and therefore end-to-end performance can be modeled.

3. Answer: D. Although you could use multifield classification everywhere, this approach does not scale. Use a BA classifier and associated rewrite to convey PLP status between nodes.

4. Answer: D. Because strict-high is given 100% of transmit weight, it should be used with a policer to ensure that other classes are not starved, especially on the J-series, where strict-high is an actual priority. You cannot use exact with a strict-high queue, but on the J-series you can use the shaping rate to cap total usage. However, a policer is preferred, as this allows excess bandwidth only when other queues are empty.

5. Answer: B. Supported on the J-series only, the shaping-rate limits the total amount of bandwidth available to the queue, regardless of activity in other queues. This in itself does not prevent starvation of lesser-priority queues, but it can help.

6. Answer: A. Many CoS configuration errors allow a commit, but they generate a log warning indicating that the configured values can be programmed. This means the default values are in effect.

7. Answer: C. Unless you shape at the logical interface level, each IFL can send up to line rate, and when multiple ...