The Cisco Catalyst 4000/4500 Series 18-port Gigabit Ethernet line card provides two ports of dedicated 1000BASE-X GBIC-based Gigabit Ethernet uplinks, as well as up to 16 GBIC-based ports for high-performance Gigabit Ethernet server connectivity. The 16 server ports can burst to Gigabit Ethernet line rate and share 8 Gbps of capacity (4 Gbps full-duplex) into the switching fabric. Because all ports use GBICs, the amount of oversubscription can be controlled by varying the number of GBICs used. All ports can utilize Gigabit EtherChannel or IEEE 802.3ad for high-speed interconnection applications. The server ports use the standard IEEE 802.1x flow control (PAUSE frame) mechanism to control Gigabit Ethernet host traffic.