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
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.