User’s Manual: SW-10200
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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).
ToS
ToS is an acronym for Type of Service. It is implemented as the IPv4 ToS priority control. It is fully decoded to
determine the priority from the 6-bit ToS field in the IP header. The most significant 6 bits of the ToS field are fully decoded
into 64 possibilities, and the singular code that results is compared against the corresponding bit in the IPv4 ToS priority
control bit (0~63).
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. 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.
V
VLAN
Virtual LAN is a method restricting 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.
