Glossary V



The Universal Asynchronous Receiver/Transmitter: A chip that governs asynchronous communications. Its primary function is to buffer incoming data, but it also buffers outbound bits.


User Datagram Protocol: A connectionless Transport layer protocol in the TCP/IP protocol stack that simply enables datagrams to be exchanged without acknowledgements or delivery guarantees, requiring other protocols to handle error processing and retransmission. UDP is defined in RFC 768.

U reference point

Reference point between a TE1 and an ISDN network. The U reference point understands ISDN signaling techniques and uses a two-wire connection.


Used for direct host-to-host communication. Communication is directed to only one destination and is originated from only one source.

unidirectional shared tree

A method of shared tree multicast forwarding. This method allows only multicast data to be forwarded from the RP.


A host is uniquely identified by the MAC address, because this address is not repeated on any other host anywhere.

unnumbered frames

HDLC frames used for control-management purposes, such as link startup and shutdown or mode specification.


Enables a switch to immediately begin forwarding frames on blocked ports when a failure is detected on the root port.


Routers nearer to the transmitting multicast server are said to be upstream from the receiving client.


unshielded twisted-pair: Copper wiring used in small-to-large networks to connect host devices to hubs and switches. Also used to connect switch to switch or hub to hub.

CCNP. Building Cisco Multilayer Switched Networks Study Guide (642-811)
CCNP: Building Cisco Multilayer Switched Networks Study Guide (642-811)
ISBN: 078214294X
EAN: 2147483647
Year: 2002
Pages: 174
Authors: Terry Jack © 2008-2017.
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