Which two statements are correct when using the no-loss forwarding class? (Choose two.)

The no-loss forwarding class is designed for traffic, such as Fibre Channel over Ethernet (FCoE) or RoCEv2, that cannot tolerate packet loss due to network congestion. To achieve this, two key mechanisms are required. First, Priority-based Flow Control (PFC), defined in IEEE 802.1Qbb, must be enabled. PFC allows a switch to send a pause frame to an upstream device to temporarily halt traffic for a specific priority when its buffer is nearing capacity, thus preventing packet drops. Second, forwarding class sets (also known as priority groups) are used to group one or more lossless forwarding classes. This allows for consistent application of CoS policies, including PFC configuration and bandwidth allocation, to all traffic requiring lossless transport.

A. Use the default scheduler map.

The default scheduler map is not configured for the strict-priority handling and guaranteed bandwidth that lossless traffic requires. A custom scheduler and map are necessary.

D. Use the default drop profile.

The default drop profile is typically tail-drop, which discards packets during congestion. This is antithetical to the goal of a no-loss forwarding class.

1. Juniper Networks TechLibrary, "Understanding CoS Lossless RoCE": This document states, "To achieve lossless transport, you must enable PFC on the 802.1p code points (priorities) of the lossless traffic." It also explains, "You map the lossless forwarding classes to a forwarding class set (a priority group)." This directly supports options C and B.

Source: Juniper Networks Documentation, "Understanding CoS Lossless RoCE", section "Lossless Transport Components".

2. Juniper Networks TechLibrary, "Example: Configuring CoS for a Lossless FCoE Fabric": This configuration example demonstrates the creation of a forwarding-class-set and a congestion-notification-profile to enable PFC. It explicitly shows that default schedulers and drop profiles are not used for the fcoe and no-loss classes.

Source: Juniper Networks Documentation, "Example: Configuring CoS for a Lossless FCoE Fabric", configuration steps.

3. Juniper Networks TechLibrary, "Understanding CoS Priority-Based Flow Control (for QFX and EX Series)": This document details the function of PFC, stating, "PFC is a link-level flow control mechanism... PFC stops traffic for a specified priority... without stopping traffic for other priorities on the link. Pausing traffic for a priority prevents packet loss for that priority during periods of congestion." This confirms the necessity of PFC (Option C) for lossless behavior.

Source: Juniper Networks Documentation, "Understanding CoS Priority-Based Flow Control", section "Overview".