If a packet is marked on a SAP-ingress, it will be remarked at the first network egress point (if remarking is enabled in the network egress policy).

The statement accurately describes the standard Quality of Service (QoS) packet flow within the Nokia Service Router Operating System (SR OS). When a packet enters the service provider network via a Service Access Point (SAP), the SAP-ingress QoS policy classifies it into a Forwarding Class (FC) and can mark its QoS bits (e.g., DSCP, 802.1p, MPLS EXP). This initial marking is used to ensure appropriate per-hop behavior (PHB) as the packet traverses the provider's core network.

Upon reaching the edge of the core network, the packet exits through a network port where a network egress QoS policy is applied. If this policy has the remarking function enabled, it will re-evaluate the packet based on its FC and profile state (in-profile or out-of-profile) and set a new QoS value in the packet header. This remarking action ensures the packet is correctly prioritized for the next network domain it is entering. The process of marking at ingress and potentially remarking at egress is a fundamental concept of the DiffServ model implemented in SR OS.

This is a "TRUE or FALSE" question. The "False" option is incorrect because it would contradict the designed functionality of Nokia's QoS architecture. The SR OS explicitly provides for the modification of QoS markings at network egress points through network QoS policies. To claim that a packet marked at ingress cannot be remarked at egress (when the policy is configured to do so) would be a misunderstanding of the distinct roles of ingress and egress QoS policies. The ingress marking governs treatment inside the core, while egress remarking governs treatment for the next network.

1. Nokia 7750 SR and 7950 XRS Quality of Service Guide, Release 23.3.R1.

Section: Chapter "QoS Policies", Subsection "Service ingress QoS policies".

Content: This section details the functions of a SAP-ingress policy, stating: "At service ingress, a QoS policy defines the FC and profile for each packet... The policy can also define the IP DSCP, IEEE 802.1p, or MPLS EXP bits to be marked in the packet header based on the classification." This confirms the first part of the question regarding marking at SAP-ingress.

2. Nokia 7750 SR and 7950 XRS Quality of Service Guide, Release 23.3.R1.

Section: Chapter "QoS Policies", Subsection "Network QoS policies".

Content: This section describes the function of policies applied at network egress: "A network QoS policy defines the QoS marking for packets sent into the service provider network core... The remarking decision is based on the forwarding class and the profile of the packet." It further clarifies that this behavior is enabled using a remarking command within the policy, which directly supports the conditional clause ("if remarking is enabled") in the question.

3. Nokia 7750 SR and 7950 XRS Quality of Service Guide, Release 23.3.R1.

Section: Chapter "QoS for VPLS", Subsection "VPLS QoS overview".

Content: The packet flow diagrams and descriptions in this section illustrate the end-to-end QoS process. They show a packet being classified and potentially marked at SAP ingress, traversing the network core (as an MPLS packet with EXP bits), and then being subject to a network egress policy which can remark the packet's outer header before it is forwarded out of the network port. This provides a practical example of the principle described in the question.