Vlans - NEC Univerge SV9100 Manual

Issue 2.0

15.3 VLANs

SV9100 Networking Manual
To ensure a network meets the specific requirements for VoIP implementation, an
IP ready check and a site survey must be completed at each site before VoIP
implementation.
One way delay must not exceed 100ms.

Round trip delay must not exceed 200ms.

Packet loss must not exceed 1%.

Data switches must be manageable.

Routers must provide QOS.
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There must be adequate bandwidth for estimated VoIP traffic. Refer to Section

15.5 Bandwidth on page
Depending on how QOS policies are built in the network, assignments may be
needed in both the CPU and IP terminal. The UNIVERGE SV9100 supports the
flagging of packets at layer 2 (VLAN tagging 802.1Q/802.1P) and at layer 3 levels.
A VLAN is used to logically break up the network and minimize broadcast
domains. Without VLANS, the network must be physically segmented to break up
broadcast domains. Each network segment is then connected through a routing
device adding latency and cost. Latency is a delay in the transmission of data and
is caused by routing packets from one LAN to another. In a VoIP environment
latency must be kept to a minimum.
802.1Q allows a change in the Ethernet Type value in the Ethernet header tagging
the Protocol ID 0x8100, identifying this frame as an 802.1Q frame. This inserts
additional bytes into the frame that composes the VLAN ID (valid IDs = 1 ~ 4094).
802.1P allows you to prioritize the VLAN using a 3-bit priority field in the 802.1Q
header. Valid VLAN priority assignments are 0 ~7. A tag of 0 is treated as normal
data traffic giving no priority. Under normal circumstances the higher the tag
numbers, the higher the priority. However this is left up to the network
administrator as they could set the exact opposite where the lower tag numbers
have a higher priority.
Currently the IPLE and CPU do not support the tagging of VLAN packets. These
devices also do not support receiving a frame with a VLAN tag. If either device
receives a packet with a VLAN tag, it is treated as an illegal frame and discarded.
Therefore when the CPU/IPLE is plugged into a data switch supporting VLANS,
the VLAN tag must be removed before passing the frame onto the CPU/IPLE.
Tagging Voice and Data Packets
Built into the IP phones is a 2 port 10/100 manageable data switch allowing for a
PC connection on the back of the IP phone. This built in data switch also supports
802.1Q and 802.1P VLAN tagging capabilities.
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