Which of the following statements about behavior aggregate and multi-field classification in a Nokia 7750 SR is TRUE?

In a Nokia 7750 SR, a SAP-ingress Quality of Service (QoS) policy performing Behavior Aggregate (BA) classification must have an unambiguous source for Layer 2 priority. The 802.1p (dot1p) bits in a VLAN tag and the MPLS EXP (lsp-exp) bits in a label are both considered Layer 2 markings. To prevent classification conflicts on packets that could potentially contain both (e.g., VPLS over MPLS), the system enforces a mutual exclusivity rule. Therefore, a single SAP-ingress QoS policy cannot be configured to trust both dot1p and lsp-exp simultaneously. This is a fundamental constraint of the QoS implementation on the platform.

A. This statement is incorrect as the best answer. While factually true that a policy can mix MAC and IP criteria, option D highlights a specific, non-obvious system limitation, which is a more critical concept.

B. This statement is incorrect as the best answer. A policy can indeed trust both DSCP (L3) and lsp-exp (L2.5), as the router applies the appropriate one based on packet type, but this describes a system capability, not a constraint like option D.

C. This statement is factually incorrect. A single SAP-ingress QoS policy is designed to contain both ip-criteria and ipv6-criteria entries to handle both IPv4 and IPv6 traffic flows concurrently.

1. Nokia 3HE 15815 AAAC TQZZA - 7750 SR OS Quality of Service Guide, Release 20.10.R1, Page 109, "SAP Ingress Policy—Behavioral Aggregate (BA) Classification": This section explicitly states, "The trust-dot1p and trust-lsp-exp commands are mutually exclusive." This directly supports the correct answer, D. The same section also notes, "The trust-dscp and trust-lsp-exp commands are not mutually exclusive," which shows why option B is not the best answer.

2. Nokia 3HE 15815 AAAC TQZZA - 7750 SR OS Quality of Service Guide, Release 20.10.R1, Page 111, "SAP Ingress Policy—Multifield Classification": This section states, "A SAP ingress QoS policy can have multiple IP, IPv6, and MAC criteria entries." This confirms that options A and C are incorrect statements regarding system limitations. Option C is factually false, and A describes a standard capability.