Which feature of the SAS-2 protocol enables deployment flexibility, security, and data traffic management?

Zoning is a specific security and isolation capability within the SAS-2 domain, but it is one feature defined by the SPL rather than the overarching protocol feature that enables flexibility, security, and traffic management holistically.

Fanout expanders increase the number of devices that can be connected in a SAS domain but do not themselves provide security or data traffic management capabilities.

Edge expanders provide connectivity at the periphery of a SAS domain and extend port counts, but they are hardware components rather than a protocol feature that controls security or traffic.

The SAS Protocol Layer (SPL) is the governing specification introduced in SAS-2 that defines how devices communicate, including security mechanisms such as zoning to restrict initiator-target access, traffic management rules, and expander interaction protocols. By operating at the protocol level, SPL enables administrators to configure and manage storage traffic across diverse deployment topologies.