On the Nokia 7750 SR, network port ingress classification for Quality of Service (QoS) is primarily based on dedicated priority marking fields within the packet and frame headers. These fields allow the router to map incoming traffic to an internal Forwarding Class (FC) and assign appropriate QoS treatment. The key criteria are the IEEE 802.1p bits (dot1p) for Layer 2 QoS in VLAN-tagged frames, the Differentiated Services Code Point (DSCP) bits for Layer 3 IP packet QoS, and the Experimental (EXP) bits for MPLS (Layer 2.5) QoS. These three represent the standard classification mechanisms at their respective layers for network ingress QoS policies.

B. While IP addresses can be used for classification within filter policies which can then influence QoS, the primary criteria for network QoS policies are the dedicated marking fields (dot1p, DSCP, EXP).

E. A Service Distribution Path (SDP) is a logical tunnel for forwarding service traffic between routers. A packet is classified at ingress before it is forwarded into an SDP, so the SDP ID cannot be an ingress classification criterion.

1. Nokia 7450 ESS, 7750 SR, 7950 XRS, and VSR Quality of Service Guide, Release 22.10.R1, Document Part Number: 3HE 18130 AAAC TQZZA, Edition 01.

Page 101, Section: "Network Ingress QoS Policies": This section explicitly states, "Network ingress policies support classification and re-marking based on the following: dot1p bits of the outermost VLAN tag, MPLS EXP bits of the top label, DSCP or IP precedence bits of an IP packet". This directly supports answers A, C, and D.

2. Nokia 7450 ESS, 7750 SR, 7950 XRS, and VSR Quality of Service Guide, Release 22.10.R1, Document Part Number: 3HE 18130 AAAC TQZZA, Edition 01.

Page 69, Section: "Filter Policies and QoS": This section clarifies that filter policies (which can match on IP addresses) are a separate entity that can be used in conjunction with QoS policies. It states, "Filter policies can be used for QoS classification...". This supports the reasoning that while possible, IP address matching is not considered a primary criterion of the network QoS policy itself, unlike dot1p, DSCP, and EXP.

3. Nokia 7450 ESS, 7750 SR, 7950 XRS, and VSR Services Overview Guide, Release 22.10.R1, Document Part Number: 3HE 18126 AAAC TQZZA, Edition 01.

Page 105, Section: "Service Distribution Paths (SDPs)": This section defines an SDP as "a path that directs traffic from one 7750 SR to another through a unidirectional service tunnel." This confirms that an SDP is a forwarding-plane construct and not an attribute of a packet arriving at a network ingress port, thus invalidating option E.