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Page 219
Appendix
LGB1108A
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.