U

UMTS Terrestrial Radio Access Network (UTRAN)

The WCDMA radio network in UMTS.

unicast

Operation of sending network traffic from one network node to another individual network node.

uninterruptible power supply (UPS)

Device that sits between a power supply and a router (or other piece of equipment) that prevents undesired power-source events, such as outages and surges, from affecting or damaging the device.

unit

JUNOS software syntax that represents the logical properties of an interface.

Universal Mobile Telecommunications System (UMTS)

Third-generation (3G), packet- based transmission of text, digitized voice, video, and multimedia, at data rates up to 2Mbps.

Update message

BGP message that advertises path attributes and routing knowledge to an established neighbor.

Update timer

Used in a distance-vector protocol to advertise routes to a neighbor on a regular basis. The JUNOS software uses a default value of 30 seconds.

upto

JUNOS software routing policy match type representing all routes that share the same most significant bits and whose prefix length is smaller than the supplied subnet in the route filter.

User Datagram Protocol (UDP)

Layer 4 protocol that provides an unreliable, connectionless service between two end IP hosts.