Filter
Top Products
LGB5128A User Manual
246
U
UDP
UDP is an acronym for User Datagram Protocol. It is a communications protocol that uses
the Internet Protocol (IP) to exchange the messages between computers.
UDP is an alternative to the Transmission Control Protocol (TCP) that uses the Internet
Protocol (IP). Unlike TCP, UDP does not provide the service of dividing a message into
packet datagrams, and UDP doesn't provide reassembling and sequencing of the packets.
The application program that uses UDP must be able to make sure that the entire
message has arrived and is in the right order. Network applications that want to save
processing time because they have very small data units to exchange may prefer UDP to
TCP.
UDP provides two services not provided by the IP layer. It provides port numbers to help
distinguish different user requests and, optionally, a checksum capability to verify that the
data arrived intact.
Common network applications that use UDP include the Domain Name System (DNS),
streaming media applications such as IPTV, Voice over IP (VoIP), and Trivial File
Transfer Protocol (TFTP).
User Priority
User Priority is a 3-bit field storing the priority level for the 802.1Q frame. It is also known
as PCP.
V
VLAN
Virtual LAN. A method to restrict communication between switch ports. VLANs can be
used for the following applications:
VLAN unaware switching: This is the default configuration. All ports are VLAN unaware
with Port VLAN ID 1 and members of VLAN 1. This means that MAC addresses are
learned in VLAN 1, and the switch does not remove or insert VLAN tags.
VLAN aware switching: This is based on the IEEE 802.1Q standard. All ports are VLAN
aware. Ports connected to VLAN aware switches are members of multiple VLANs and
transmit tagged frames. Other ports are members of one VLAN, set up with this Port
VLAN ID, and transmit untagged frames.
Provider switching: This is also known as Q-in-Q switching. Ports connected to
subscribers are VLAN unaware, members of one VLAN, and set up with this unique Port
VLAN ID. Ports connected to the service provider are VLAN aware, members of multiple
VLANs, and set up to tag all frames. Untagged frames received on a subscriber port are
forwarded to the provider port with a single VLAN tag. Tagged frames received on a
subscriber port are forwarded to the provider port with a double VLAN tag.
VLAN ID
VLAN ID is a 12-bit field specifying the VLAN to which the frame belongs.
Voice VLAN
Voice VLAN is VLAN configured specially for voice traffic. By adding the ports with voice
devices attached to voice VLAN, we can perform QoS-related configuration for voice data,
ensuring the transmission priority of voice traffic and voice quality.