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Page 224
LGB5028A User‘s Manual
724-746-5500 | blackbox.com
Appendix A: Glossary
Tag Priority: Tag priority is a 3-bit field storing the priority level for the 802.1Q frame.
TCP: TCP is an acronym for Transmission Control Protocol. It is a communications protocol that uses the Internet Protocol (IP) to
exchange the messages between computers.
The TCP protocol guarantees reliable and in-order delivery of data from sender to receiver and distinguishes data for multiple
connections by concurrent applications (for example, Web server and e-mail server) running on the same host.
The applications on networked hosts can use TCP to create connections to one another. It is known as a connection-oriented
protocol, which means that a connection is established and maintained until such time as the message or messages to be
exchanged by the application programs at each end have been exchanged. TCP is responsible for ensuring that a message is
divided into the packets that IP manages and for reassembling the packets back into the complete message at the other end.
Common network applications that use TCP include the World Wide Web (WWW), e-mail, and File Transfer Protocol (FTP).
TELNET: TELNET is an acronym for TELetype NETwork. It is a terminal emulation protocol that uses the Transmission Control
Protocol (TCP) and provides a virtual connection between TELNET server and TELNET client.
TFTP: TFTP is an acronym for Trivial File Transfer Protocol. It is transfer protocol that uses the User Datagram Protocol (UDP) and
provides file writing and reading, but it does not provide directory service and security features.
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. This means that 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.
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.