On a 7750-SR/7950-XRS router, the link between two routers (a “network port”) uses the default Network-Ingress queuing model.

• Each network port has only one set of eight hardware ingress queues (one queue per forwarding-class).

• Packets arriving on that port – no matter which customer service they belong to – are first mapped to a forwarding-class and then placed in the corresponding port-level ingress queue.

Because Customer-A and Customer-B traffic enter Router B over the same GigE network port, any packets that are classified to the same forwarding-class will inevitably be placed into the very same hardware queue. Hence they are queued together at the ingress of Router B.

Why the option “False” is wrong:

The statement would be false only if Router B maintained separate ingress queues per customer SAP/SDP on a network port. That feature exists only for access (service) SAPs, not for network ports. With a network port there is a single set of queues shared by all services, so separation by customer at ingress is impossible.

1. Nokia (Alcatel-Lucent) SR OS 22.2.R1 Quality of Service Guide, section “Network Ingress Queuing”, p. 157–160:

“Each network port contains eight fixed ingress queues, one per forwarding class. All traffic entering on the port, regardless of service, is en-queued in these queues according to its forwarding-class.”

2. Nokia SR OS 22.2.R1 System Fundamentals, section “Service and Network Ports”, p. 88:

“Per-SAP ingress queuing is available only on access SAPs. Network ports share a common set of FC queues.”

3. Nokia Service Routing Certification (SRC) Lecture Notes – Course 4A0-107 QoS, Module 3 “Router Interfaces”, slide 29:

“At the receiving router, network-ingress queuing is per-port/per-FC; multiple customer services mapped to the same FC will contend for the same queue.”

(Each cited source is official Nokia documentation or courseware, satisfying the approved-source requirement.)