In software releases earlier than Cisco IOS Release 12.2(33) SXI, port-based QoS and port ACLs (PACLs) are supported only on Layer 2 single-chassis or multichassis EtherChannel (MEC) links. Beginning with Cisco IOS Release 12.2(33) SXI, port-based QoS and PACLs can be applied to any physical port in the VSS, excluding ports in the VSL. PACLs can be applied to no more than 2046 ports in the VSS.