NEC SL1100 Networking Manual page 153

NEC SL1100
Networking Manual
The cabling infrastructure can be simplified. There is no longer a need

for separate cabling for the phone system. Built into the IP phones is a 2
port 10/100 manageable data switch. The data connection for the PC is
available on the back of the IP phone. This built in data switch also
supports 802.1Q and 802.1 P VLAN tagging abilities. The data and the
voice can be tagged separately.
Allows you to connect remote office workers with a telephone that has

the look and same functionality as the telephones connected at the
office.
SIP is used for VoIP as defined by the IETF (Internet Engineering Task Force)
RFC3261. The NEC SIP MLT uses IP Multiline Station (SIP) (proprietary
enhanced SIP protocol) to facilitate the multifunction, multiline telephone.
The SIP Multiline Telephone interfaces directly to the CPU that houses the
VoIPDB daughter board. The VoIPDB provides the digital signal processors
(DSPs) for IP stations and trunks.
VoIPDB provides 32 DSPs

A DSP provides format conversion from circuit switched networks (TDM) to
packet switched networks (IP). Each voice channel from the circuit switched
network is compressed and packetized for transmission over the packet
network. In the reverse direction, each packet is buffered for de-jittering,
decompressed and sent to the circuit switched network. Each DSP converts a
single speech channel from IP to TDM and vice versa.
The following are examples of DSP allocation.
Calling from an IP phone to a TDM phone uses one DSP.

Calling from an IP phone to another IP phone, registered to the same

CPU, uses no DSPs.
Calling from a TDM phone to another TDM phone uses no DSPs.

Calling from a TDM phone and out an IP trunk uses one DSP.

An IP to IP call is peer-to-peer, and no DSP resource is used. When this

feature is deactivated, an IP to IP call consumes two DSP resources.
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