IEEE 802.1 P/Q
IEEE 802.1P and Q redefine the Ethernet header to include information for prioritization and VLAN tagging
IEEE 802.1P defines a priority field that can be used by LAN switches and such at the Ethernet level to prioritize traffic
IEEE 802.1Q defines a standard format for frame tagging on trunk lines of LAN switches (as well as server ports), replacing the older proprietary versions (e.g. Cisco’s ISL and 3COMs VLT)
VLANs can be used to complement IP routing in corporate networks
Normally VLANs are port-based to the desk-top and tagged on trunk lines
IEEE 802.1Q compatibility should be a basic requirement of a modern LAN switch