User's Manual

Administrator’s Guide - SoundPoint

IP / SoundStation

IP Optimization

4 Optimization

4.1 Ethernet Switch

The SoundPoint

IP phones contain two Ethernet ports, labeled LAN and PC, and an

embedded Ethernet switch that runs at full line-rate. The Ethernet switch allows a per-

sonal computer and other Ethernet devices to connect to the office LAN by daisy

chaining through the phone, eliminating the need for a stand-alone hub. The

SoundPoint

IP switch gives higher transmit priority to packets originating in the

phone. SoundPoint

IP can be powered through a local AC power adapter or can be

line-powered (power supplied through the signaling or idle pairs of the LAN Ethernet

cable). Line powering typically requires that the phone plugs directly into a dedicated

LAN jack. Devices that do not require LAN power can then plug into the

SoundPoint

IP PC Ethernet port.

SoundPoint

IP Switch - Port Priorities

To help ensure good voice quality, the Ethernet switch embedded in the

SoundPoint

IP phones should be configured to give voice traffic emanating from the

phone higher transmit priority than those from a device connected to the PC port. If

not using a VLAN (VLAN blank in the setup menu), this will automatically be the

case. If using a VLAN, ensure that the 802.1p priorities for both default and real-time

transport protocol (RTP) packet types are set to 2 or greater. Otherwise, these packets

will compete equally with those from the PC port. For more information, refer to

4.6.1.9 Quality of Service <QOS/> on page 118.

4.2 Application Network Setup

4.2.1 Real-Time Transport Protocol Ports

The phone is compatible with RFC 1889 - RTP: A Transport Protocol for Real-Time

Applications - and the updated RFCs 3550 and 3551. Consistent with RFC 1889, the

phone treats all RTP streams as bi-directional from a control perspective and expects

that both RTP end points will negotiate the respective destination IP addresses and

ports. This allows real-time transport control protocol (RTCP) to operate correctly

even with RTP media flowing in only a single direction, or not at all. It also allows

greater security: packets from unauthorized sources can be rejected.