According to Cisco, customers should expect only modest performance gains when implementing tag switching on the 7500 series of routers, although it will provide traffic control capabilities such as those noted above. Be aware that Cisco plans to implement tag switching in advance of a standard, so some disruption is inevitable when you later upgrade to the fully standard version. The Cisco software that includes tag switching will be available this spring for the 7500 routers and the LightStream 1010. Also note that, because it's essentially a routing scheme, tag switching does not explicitly support VLANs. Tag switches will make a forwarding decision based on the tag switching tag and ignore 802.1q VLAN tags, unless configured to do otherwise.
Tag switching supports QoS in the same shorthand way that it supports routing.
With RSVP, for example, a tag switch would allocate a tag corresponding to each reservation made. Tag switches can forward multicast traffic by associating a tag with a multicast tree. To avoid overlap among multicast groups, Cisco has proposed extensions to existing multicast protocols that would allocate tags among multicast tag switches operating across a common network. While tag switching has a way to go in the standards process, the ATM Forum MPOA specification is nearly complete and is stable enough to implement. Where LANE provides Layer 2 bridging, NHRP provides Layer 3 shortcut routing.