Chapter Review Answers

  1. Answer: B. Currently only queuing versions of MPC support per unit and H-CoS.

  2. Answer: A. The excess rate option is used for Trio. Excess bandwidth share is used for older IQ2 PICs on ADPCs. You can control excess share as a percentage or proportion.

  3. Answer: B. Trio interfaces factor both Layer 2 and Layer 1 overhead into the shaping rate and display queue statistics. This includes Ethernet’s interframe gap (IFG), preamble, and FCS. You can adjust the overhead values to add or subtract bytes to ensure that shaping rates do not penalize end users for additional overhead that may be added by carrier equipment, such as a DSLAM adding multiple VLAN tags.

  4. Answer: E. While you can oversubscribe G-Rates/queue transmit rates, this is not ideal practice unless external means are in place to ensure all queues are not simultaneously active. A queue’s transmit rate is considered a G-Rate, as is setting a CIR in a TCP, which is then applied to either L2 or L3 scheduling nodes.

  5. Answer: E. All are true. See the previous note regarding overbooking G-Rates. If you want to ensure traffic discard, you can set an IFL shaping to a rate that is higher than the IFL-Set or IFD shaping rate, but again, this is not typical. The remaining construct is a critical aspect of Trio H-CoS scale as, unlike IQ2 interfaces, it permits CoS profiled for IFLs that would otherwise have no explicit CoS configuration. The remaining profile can be just a PIR/shaped rate or can include a CIR/G-Rate to provide ...

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