Polycom Version 1.4.x 17 - Manual (Page 65)

Administrator Guide - SoundPoint ® IP / SoundStation ® IP Optimization
Copyright © 2004 Polycom, Inc. 57
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 via a local AC power adapter or can be line-
powered (power supplied via 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 RTP
packet types are set to 2 or greater. Otherwise, these packets will compete equally
with those from the PC port. For more information, see 4.6.1.7 Quality of Service
<QOS/> on page 86.
4.2 Application Network Setup
4.2.1 RTP 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 endpoints will negotiate the respective destination IP addresses and
ports. This allows 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 unautho-
rized sources can be rejected.