User's Manual

472 802.1Q VLAN description
The 802.1Q support is configured from the user display interface of the
IP Phone. Configure 802.1Q VLAN support when you initially configure
an IP Phone. The switch ports for Voice Gateway Media Card TLAN
network interfaces must be configured as untagged ports so the header is
removed. While the IP Phone 2001 and the IP Audio Conference Phone
2033 provide VLAN support, they do not provide a port for a PC.
The 802.1Q IEEE protocol standard allows virtual LANs (VLANs) to be
defined within a single LAN. This improves bandwidth management and
limits the impact of broadcast and multicast messages. A higher level of
security between segments in a network can also be achieved.
802.1Q functionality is supported only on the IP Phone. The IP Line
application IP stack does not provide 802.1Q support for the Voice
Gateway Media Card.
Description
The p bits within the 802.1Q standard allow packet prioritization at Layer
2 improving network throughput for VoIP data.
The 802.1Q standard specifies a new format of Ethernet frame. A standard
Ethernet frame contains
• a header consisting of a six-byte destination MAC address (following
the header is a data area)
•
a six-byte source MAC address
•
a two-byte protocol identifier
The 802.1Q formatted frame is identical to a standard Ethernet frame, with
the exception of the 4-byte 802.1Q tag that is inserted between the source
MAC address and the protocol identifier. The first 16 bits of the 802.1Q
tag field is the Tag Protocol Identifier containing 8100 (hex), allowing the
Ethernet interface to distinguish it from standard Ethernet frames. The last
16 bits of the 802.1Q tag contain the following information
•
a 3-bit Priority field (the 802.1p defined bits)
• a 1-bit Canonical Field Identifier (CFI)
• a 12-bit VLAN ID field
Nortel Communication Server 1000
IP Phones Fundamentals
NN43001-368 02.07
5 February 2009
Copyright © 2003-2009 Nortel Networks
.