Deploying a captive portal for user authentication can provide an additional layer of security to the guest network and ensure that users are authorized and authenticated before they can access the network. It can also accommodate the marketing team's request by allowing them to customize the portal with the cafeteria's branding and message.

An access control vestibule, also known as a mantrap, is a physical security access control system that consists of a small space with two sets of interlocking doors. The first set of doors must close before the second set opens, preventing unauthorized individuals from following authorized individuals into facilities with controlled access. This activity, also known as tailgating, results in unauthorized access to the facility. An access control vestibule can help deter and detect tailgating attempts, as well as provide a containment area while authorization for physical access is verified.
References
Access Control Vestibules: Types and Peculiarities
Mantrap (access control)
PE-3 (8): Access Control Vestibules

Flow control is a mechanism that allows a network device to regulate the amount of traffic it can receive or send. Flow control can help prevent congestion and buffer overflow by sending pause frames or signals to the sender when the receiver's buffer is full or nearly full. Flow control can cause traffic to pause, allowing the switches to drain buffers and resume normal operation. Speed is a parameter that determines the data transfer rate of a network link. 802.1Q is a standard for VLAN (Virtual Local Area Network) tagging, which allows multiple logical networks to share the same physical infrastructure. Duplex is a mode of communication that determines how data is transmitted and received on a link. Full duplex allows simultaneous transmission and reception, while half duplex allows only one direction at a time.
References: CompTIA Network+ Certification Exam Objectives Version 7.0 (N10-007), Objective 1.5:
Compare and contrast network cabling types, standards and speeds.

Explanation
"Using special STP frames known as bridge protocol data units (BPDUs), switches communicate with other switches to prevent loops from happening in the first place. Configuration BPDUs establish the topology, where one switch is elected root bridge and acts as the center of the STP universe. Each switch then uses the root bridge as a reference point to maintain a loop-free topology."