Polycom 2000/4000 Manual De Usuario

Chapter 2-Additional Conferencing Information

Lost Packet Recovery (LPR) and Dynamic Bandwidth Allocation (DBA) help 

minimize media quality degradation that can result from packet loss in 

the network.

Packet Loss refers to the failure of data packets, transmitted over an IP 

network, to arrive at their destination. Packet Loss is described as a 

percentage of the total packets transmitted.

Network congestion within a LAN or WAN, faulty or incorrectly 

configured network equipment or faulty cabling are among the many 

causes of Packet Loss.

Packet Loss affects the quality of:
•

Video – frozen images, decreased frame rate, flickering, tiling, 

distortion, smearing, loss of lip sync

•

Audio – drop-outs, chirping, audio distortion

•

Content – frozen images, blurring, distortion, slow screen refresh rate

The Lost Packet Recovery (LPR) algorithm uses Forward Error Correction 

(FEC) to create additional packets that contain recovery information. 

These additional packets are used to reconstruct packets that are lost, for 

whatever reason, during transmission. Dynamic Bandwidth Allocation 

(DBA) is used to allocate the bandwidth needed to transmit the additional 

packets.