RCDD (RCDD): Network Design Principles and Practice 3 — Questions and Answers
Question 1: During a data center design, an RCDD must select between a top-of-rack (ToR) and end-of-row (EoR) switching architecture. Which advantage is unique to the ToR model?
- Fewer switches required overall
- Shorter horizontal cable runs to servers within the rack (Correct answer)
- Easier physical access for switch maintenance
- Lower switch port density requirements
Correct answer: Shorter horizontal cable runs to servers within the rack
In a ToR design, switches reside in each rack, so server connections are short patch cords within the same rack rather than long horizontal runs to a remote row switch.
Question 2: What is the maximum distance allowed for a single horizontal cable run from the TR to a telecommunications outlet (TO) per TIA-568?
- 70 m
- 90 m (Correct answer)
- 100 m
- 110 m
Correct answer: 90 m
TIA-568 limits the permanent link (horizontal cable) to 90 m, reserving the remaining 10 m of the 100 m channel budget for patch cords.
Question 3: An RCDD is documenting a cabling plant using ANSI/TIA-606 identifiers. Which identifier type is used to label a telecommunications room itself?
- Pathway identifier
- Space identifier (Correct answer)
- Cable identifier
- Bonding conductor identifier
Correct answer: Space identifier
TIA-606 defines space identifiers to uniquely label rooms and areas such as telecommunications rooms, equipment rooms, and entrance facilities.
Question 4: A designer is evaluating single-mode fiber types for an inter-building backbone exceeding 2 km. Which ITU-T fiber type provides the lowest dispersion in the 1550 nm window for long-haul applications?
- OS1 (G.652)
- OS2 (G.652.D) (Correct answer)
- G.653 dispersion-shifted fiber
- G.657 bend-insensitive fiber
Correct answer: OS2 (G.652.D)
OS2, based on ITU-T G.652.D, offers very low water peak attenuation and is optimized for low-loss transmission at 1310 nm and 1550 nm, making it the preferred choice for long campus backbones.
Question 5: Which grounding and bonding standard specifically addresses telecommunications systems in commercial buildings and is referenced in RCDD practice?
- NFPA 70 Article 250
- ANSI/TIA-607-C (Correct answer)
- IEEE 802.3af
- NEC Article 800
Correct answer: ANSI/TIA-607-C
ANSI/TIA-607-C establishes requirements for grounding and bonding of telecommunications infrastructure in commercial buildings.
Question 6: In an optical fiber link budget calculation, the term 'system margin' is included to account for which factors?
- Chromatic dispersion and polarization mode dispersion only
- Future splices, component aging, and unforeseen losses (Correct answer)
- Connector insertion loss only
- Fiber bending radius violations
Correct answer: Future splices, component aging, and unforeseen losses
System margin is a safety buffer that accounts for additional splices during repairs, component degradation over time, and other unpredictable attenuation sources.
Question 7: When applying the ANSI/BICSI-002 data center design standard, which tier classification requires concurrently maintainable power and cooling paths?
- Tier I
- Tier II
- Tier III (Correct answer)
- Tier IV
Correct answer: Tier III
Tier III (Concurrently Maintainable) requires redundant components and multiple distribution paths so that any planned maintenance can occur without shutting down IT operations.
RCDD (RCDD): Network Design Principles and Practice 3
During a data center design, an RCDD must select between a top-of-rack (ToR) and end-of-row (EoR) switching architecture.
Which advantage is unique to the ToR model?