-115-
as an IEEE 802.1Q-tagged frame. This field is located at the same position as the EtherType/length field in
untagged frames, and is thus used to distinguish the frame from untagged frames.
Tag control information (TCI):
divided into PCP, DEI, and VID
Priority code point (PCP):
a 3-bit field which refers to the IEEE 802.1p class of service and maps to the
frame priority level.
Drop eligible indicator (DEI)
: a 1-bit field. (formerly CFI). It may be used separately or in conjunction with
PCP to indicate frames eligible to be dropped in the presence of congestion.
VLAN identifier (VID)
: a 12-bit field specifying the VLAN to which the frame belongs.
Untagged frame
: A standard Ethernet frame with no VLAN Tag field
Priority-tagged frame
: An IEEE 802.1Q frame which VID field value is zero (VID=0)
VLAN-Tagged frame
: An IEEE 802.1Q frame which VID field value is not zero (VID>0)
Double tagging, Double Tags
: With the IEEE standard 802.1ad, double-tagging can be useful for Internet
service providers, allowing them to use VLANs internally while mixing traffic from clients that are already
VLAN-tagged. The outer (next to source MAC and representing ISP VLAN) S-TAG (service tag) comes first,
followed by the inner C-TAG (customer tag). In such cases, 802.1ad specifies a TPID of 0x88a8 for
service-provider outer S-TAG.
C-tag:
Tag with TPID 0x8100
S-tag:
Tag with TPID 0x88A8
Priority S-tagged frame
: Priority tagged frame with S-tag (TPID=0x88A8, VID=0)
Priority C-tagged frame
: Priority tagged frame with C-tag (TPID=0x8100, VID=0)
VLAN S-tagged frame
: Tagged frame with S-tag (TPID=0x88A8, VID
>
0)
VLAN C-tagged frame
: Tagged frame with C-tag (TPID=0x8100, VID
>
0)
PVID (Port VID):
PVID is the default VID of an ingress port. It is used in 802.1Q filtering for untagged
packets. It is also often used as [Default Tag - VID] for egress tagging operation.
2.14.2 VLAN Membership
Summary of Contents for KGS-1064-HP
Page 1: ... 1 KGS 1064 HP Web Management Interface User s Manual Software Rev 1 0 or up DOC 170505 ...
Page 10: ... 10 5 4 Configuration 219 5 4 1 Save 219 5 4 2 Upload 220 Glossary 221 ...
Page 135: ... 135 2 17 7 DSCP Based QoS ...
Page 136: ... 136 ...
Page 138: ... 138 2 17 8 DSCP Translation ...
Page 139: ... 139 ...