Huawei Updated H35-211_V2.5 Exam Questions and Answers by wynter-rose

WRED (weighted early drop) uses lower and upper thresholds to determine a probabilistic drop curve; the drop probability scales with the average queue length between these thresholds—therefore D is correct.

A is incorrect because early dropping inevitably affects services to some extent; it’s designed to trade small, controlled loss for stability.

B is incorrect; devices use early drop before buffers fill, and when full, tail drop still applies—both mechanisms coexist.

C is imprecise in Huawei’s terminology; early drop begins when the average queue depth crosses the lower threshold and increases up to the upper threshold, not simply “before a preset threshold” without that two-threshold relationship.

XG-PON (10G GPON) adopts XGEM framing. Compared with GPON’s 12-bit GEM Port-ID, XGEM expands the Port-ID field to 16 bits, increasing the number of logical data flows that can be identified per ONU/OLT and improving service granularity. Hence the correct length is 16 bits.

GPON traffic policing/shaping is commonly applied at multiple layers:

T-CONT rate control (T-CONT-CAR): controls upstream bandwidth per T-CONT.

GEM-port rate control (GEM-CAR): limits per GEM port.

Service flow rate control (Flow-CAR): enforces per-service policies.

GEM mapping is a forwarding association (service→GEM) and not itself a rate-control mechanism.

XG-PON encapsulates user data into XGEM frames. The XGEM Port-ID field is 12 bits, allowing identification of logical connections (GEM ports) per ONU. This mirrors the 12-bit Port-ID used in GPON GEM.