H12-891_V1.0 Exam Dumps : HCIE-Datacom V1.0

DiffServ QoS model operates on per-hop behavior (PHB) and has these limitations:

A. ✅ Single-hop behavior; no end-to-end path awareness.

B. ✅ Cannot guarantee dedicated resources to individual users.

C. ✅ Does not address traffic bursts; congestion is still possible.

D. ✅ Queue limitations hinder fine-grained SLA assurance and deterministic delay.

Exact Extract – HCIE-Datacom QoS Section:

“DiffServ provides PHB without path-level control. It cannot guarantee SLA for individual users due to limited queuing mechanisms and lack of end-to-end visibility.”

MPLS Positioning in the TCP/IP Model

MPLS (Multiprotocol Label Switching) operatesbetween the Data Link Layer (Layer 2) and the Network Layer (Layer 3).

✅MPLS is protocol-independentand supports variousnetwork layer protocols (IPv4, IPv6, VPN, etc.)by using labels instead of traditional IP routing.

✅How MPLS Works:

MPLSassigns labels to packets, allowing fast forwarding based on the label rather than a routing table lookup.

SupportsLayer 3 VPNs (L3VPNs), Layer 2 VPNs (L2VPNs), and MPLS Traffic Engineering (MPLS-TE).

✅Why MPLS is Between Layer 2 and Layer 3?

MPLS adds a label between the Layer 2 (Ethernet, PPP) and Layer 3 (IP) headers, effectivelycreating a separate forwarding mechanism.

Label Switching Routers (LSRs) forward packets based on labels instead of IP addresses, reducing processing time.

Reference from Huawei HCIE-Datacom Documentation:

Huawei MPLS Technology Guide – MPLS Architecture and Label Switching

HCIE-Datacom Study Material – MPLS Positioning and Functionality in TCP/IP

InSRv6 (Segment Routing over IPv6),flavorsare extensions to standard SRv6 instructions that define how theSegment Routing Header (SRH)is handled at specific points:

PSP (Penultimate Segment Pop): Instructs thepenultimate nodeto remove the SRH before reaching the last node →✅

USD (Ultimate Segment Decapsulation): Instructs thefinal segmenttoremove the SRH and IPv6 header, exposing the payload →✅

PSD (Penultimate Segment Decapsulation): Instructs thepenultimate nodeto remove the SRH and deliver the payload →✅

USP (Ultimate Segment Pop)isnot a standard flavorin Huawei SRv6 implementations →❌

Correct answers: A, B, D