BDS DOCSIS Standards and Protocols 2

Question 1

What does BPI+ stand for and what does it protect in DOCSIS?

Accepted Answer

Baseline Privacy Interface Plus — encrypts downstream data between CMTS and modem

Answer

BPI+ (Baseline Privacy Interface Plus) provides authentication and AES encryption of downstream traffic between the CMTS and each cable modem, preventing unauthorized access.

Question 2

What is the difference between a primary service flow and a secondary service flow in DOCSIS?

Accepted Answer

Primary flows are always active; secondary flows are created on demand for specific traffic types

Answer

A primary service flow exists for the life of the modem session and carries default traffic, while secondary service flows are provisioned dynamically to handle traffic with specific QoS requirements.

Question 3

In DOCSIS, what is a Service ID (SID)?

Accepted Answer

A numerical label that maps upstream bandwidth reservations to a specific cable modem service flow

Answer

A Service ID (SID) is assigned by the CMTS to each upstream service flow and is used to grant bandwidth allocation in MAP messages.

Question 4

What upstream channel access method does DOCSIS use to coordinate multiple modems sharing the same channel?

Accepted Answer

TDMA (Time Division Multiple Access)

Answer

DOCSIS uses TDMA (and A-TDMA/S-CDMA in later versions), where the CMTS schedules transmission slots via MAP messages so modems take turns transmitting without collision.

Question 5

What is the significance of the DOCSIS 3.1 upstream OFDMA technology?

Accepted Answer

It allows multiple modems to share subcarriers simultaneously within the same upstream channel

Answer

OFDMA (Orthogonal Frequency Division Multiple Access) allows the CMTS to assign specific subcarrier groups to individual modems simultaneously, dramatically increasing upstream efficiency and throughput.

BDS - Broadband Distribution Specialist Practice Test

BDS - Broadband Distribution Specialist Practice Test

BDS DOCSIS Standards and Protocols 2