KTI Networks KGS-810F, Руководство пользователя

Страница: 18 / 70

-18-
3. Advanced Functions
To help a better understanding about the software management interfaces, this chapter describes some
advanced functions provided by the switch.
3.1 Abbreviation
Ingress Port : Ingress port is the input port on which a packet is received.
Egress Port : Egress port is the output port from which a packet is sent out.
IEEE 802.1Q Packets : A packet which is embedded with a VLAN Tag field
VLAN Tag : In IEEE 802.1Q packet format, 4-byte tag field is inserted in the original Ethernet frame between
the Source Address and Type/Length fields. The tag is composed of:
#of bits 16 3 1 12
Frame field TPID User priority CFI VID
TPID : 16-bit field is set to 0x8100 to identify a frame as an IEEE 802.1Q tagged packet
User Priority : 3-bit field refer to the 802.1p priority
CFI : The Canonical Format Indicator for the MAC address is a 1 bit field.
VID : VLAN identifier, 12-bit field identifies the VLAN to which the frame belongs to.
Untagged packet : A standard Ethernet frame with no VLAN Tag field
Priority-tagged packet : An IEEE 802.1Q packet which VID filed value is zero (VID=0)
VLAN-Tagged packet : An IEEE 802.1Q packet which VID filed value is not zero (VID<>0)
PVID (Port VID) : PVID is the default VID of an ingress port. It is often used in VLAN classification for
untagged packets. It is also often used for egress tagging operation.
DSCP : Differentiated Service Code Point, 6-bit value field in an IP packet
VLAN Table lookup : The process of searching VLAN table to find a VLAN which matches the given VID index
MAC address table lookup : The process of searching MAC address table to find a MAC entry which matches
the given destination MAC address and the port where the MAC address is located
Packet forwarding : also known as packet switching in a network switch based on MAC address table and
VLAN table information
VLAN forwarding : the operation that a packet is forwarded to an egress destination port based on VLAN
table information
VLAN group : configuration information about a VLAN which can be recognized in the switch. The
information includes a VID associated to the VLAN, member ports, and some special settings.