SpectraLink NetLink Wireless Telephones Best Practices White Paper Wireless Telephone - Manual (Page 18)

White Paper
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6.0 NetLink Wireless Telephones and Subnets
Subnets are used to create a boundary between network segments.
Although these boundaries are logical, they become somewhat of a
physical boundary for mobile network devices moving throughout the
enterprise. When a device with an established IP data stream (such as
with an active phone call) attempts to roam across a subnet boundary, it
needs to obtain a valid IP address within the new subnet. During this
process the data stream cannot be re-established automatically and the
connection (voice call) is dropped. In the case of the NetLink Wireless
Telephones, the handsets should be power-cycled to obtain a new
DHCP address. The handsets can automatically recover in the new
subnet from a lost network connection with the original subnet, but the
40-second failure and recovery time generally warrants cycling the
power.
Some APs, Ethernet switches, and third-party devices have
implemented methods to facilitate device mobility. While these methods
are transparent to the client device, they often cause enough delay and
latency to manifest poor voice quality. In addition, many of these
methods do not work well under loaded conditions, such as might be
experienced with a large number of highly mobile wireless voice users.
NetLink Wireless Telephones must reside within the same subnet as the
source of the SpectraLink Voice Priority (SVP) control. SVP can be
controlled from a NetLink Telephony Gateway, a NetLink SVP Server, or
a combination of the two. Because the NetLink SVP Server can only
operate in a single PBX interface mode, Wireless Telephones cannot
operate with a NetLink Telephony Gateway and in a native IP interface
to an IP telephony server on the same NetLink SVP server. All SVP
Servers on the same subnet must operate in the same PBX interface
mode (either native IP or through NetLink Telephony Gateways).
There are additional subnet requirements for NetLink Wireless
Telephones based on the infrastructure components that are used.