Cisco Cisco IOS Software Release 12.0(21)S

ACL—Access control list.

ATM—Asynchronous Transfer Mode.

CEF—Cisco Express Forwarding.

GRE—Generic Routing Encapsulation. A standards-based tunneling protocol that can encapsulate a 
wide variety of protocol packet types inside tunnels, creating a virtual point-to-point link to Cisco 
routers at remote points over an IP internetwork (RFC 1701 [5], RFC 1702 [6]).

GSR—Gigabit Switched Router. Former name of the Cisco 12000 series Internet router.

IP—Internet protocol.

LC—Line card.

Mpps—Million packets per second.

POS—Packet over Sonet.

PPP—Point-to-Point protocol.

pps—Packets per second.

PSA—Packet Switching ASIC. The ASIC on the performance OC48 line card that does the “fast path” 
packet forwarding operations.

RP—Route processor.

ToS—Type of service. A field in the IP header.

TSC—Tunnel server card. A dedicated card to do all the tunnel encapsulation and decapsulation work.