Cisco Systems RJ-45-to-AUX manual 395

U−X

unicast

A frame in which the destination MAC address specifies the single destination computer. Unicast can be summarized as direct network traffic between two individual nodes.

unshielded twisted−pair (UTP)

A type of cable that uses multiple twisted pairs of copper wire in a casing that does not provide much protection from EMI. The most common network cable in Ethernet networks, it is rated in five categories.

UplinkFast

Provides fast convergence after an STP topology change and achieves load balancing between redundant links.

User Datagram Protocol (UDP)

A communications protocol that provides connectionless, unreliable communications services and operates at the Transport layer of the OSI model. It requires a transmission protocol such as IP to guide it to the destination host.

user−network interface (UNI)

An interface that provides a connection between an ATM end−station interface and an ATM switch interface.

virtual LAN (VLAN)

Allows a network administrator to divide a bridged network into several broadcast domains. Each VLAN is considered its own separate subnet, and Layer 3 routing is still required to route between VLANs. VLANs can be based on the port identifier of the switch, the MAC address, Layer 3 address, directory information, or application information. VLANs can be implemented on different media types such as Ethernet, FDDI, Token Ring, or ATM. The benefits of VLANs are limited broadcast domains, added security, and redundancy.

virtual private network (VPN)

A network that uses a public network such as the Internet as a backbone to connect two or more private networks. A VPN provides users with the equivalent of a private network in terms of security.

VLAN Trunking Protocol (VTP)

A protocol used to enhance and configure the extension of broadcast domains across multiple switches. VTP dynamically reports the addition of VLANs throughout the switched network, in turn creating a consistent switched network.

VLAN Trunking Protocol (VTP) pruning

A protocol used to reduce the number of switches participating in VTP by removing switches from the database that do not have certain VLANs’ numbered ports. For example, if switch 1 and switch 2 have ports belonging to VLAN 6 and switch 3 does not, it will not forward VLAN 6 traffic on the trunk link to switch 3 unless switch 3 is a gateway to another switch that has VLAN 6 member ports. If VTP pruning were not enabled on a trunk port, all VLAN traffic would travel through the trunk links to all the switches whether they had destination ports or not.

wide area network (WAN)

Data communications network that serves users across a broad geographical area. A WAN often uses transmission devices such as modems and Channel Service Units/Data Service Units (CSU/DSU) to carry signals over leased lines or common carrier lines.

window flow control

A flow−control method in which the receiving host buffers the data it receives and holds it in the buffer until it can be processed. After it is processed, an acknowledgment is sent to the sender.

X−TAG

A one−byte value used as an identifier Multilayer Switch Route Processor (MLS−RP).

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