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Cisco TelePresence Server

TelePresence Packet Loss and Poor Audio/Visual Quality in One Direction

Document ID: 118431

Updated: Nov 07, 2014

Contributed by Cisco TAC Engineers.

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Introduction

This document describes how to troubleshoot the problem of packet loss in one direction on a TelePresence product and the poor audio/visual quality in that direction that results.

Prerequisites

Requirements

Cisco recommends that you have knowledge of these topics:

  • Cisco TelePresence IP Gateway (GW) 3500 / Media Service Engine (MSE) IPGW blade
  • Cisco TelePresence IP Video Conferencing Recording (VCR) 2200 / MSE VCR blade
  • Cisco TelePresence ISDN GW 3200 and 3241 / MSE 8310 and 8321 ISDN blades
  • Cisco TelePresence Mulitpoint Control Unit (MCU) 4200 / MSE 8420
  • Cisco TelePresence MCU 4500
  • Cisco TelePresence MSE 8510 blade
  • Cisco TelePresence Servers
  • Cisco TelePresence Video Communication Server (VCS)
  • Cisco TelePresence Serial GW 3340 / MSE 8330 blade

Components Used

The information in this document is based on these software and hardware versions:

  • Cisco TelePresence IP GW 3500 / MSE IPGW blade
  • Cisco TelePresence IP VCR 2200 / MSE VCR blade
  • Cisco TelePresence ISDN GW 3200 and 3241 / MSE 8310 and 8321 ISDN blades
  • Cisco TelePresence MCU 4200 / MSE 8420
  • Cisco TelePresence MCU 4500
  • Cisco TelePresence MSE 8510 blade
  • Cisco TelePresence Servers
  • Cisco TelePresence Video Communication Server
  • Cisco TelePresence Serial GW 3340 / MSE 8330 blade

The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.

Problem

You experience packet loss and poor audio/visual quality in one direction.

Solution

If you encounter a great deal of packet loss in one direction, this could be caused by a duplex mismatch somewhere in your network.

  • A duplex mismatch occurs when a piece of equipment at one end of an Ethernet cable has a different duplex setting from the equipment at the other end.

    Note: Often the duplex mode is auto-negotiated between the two pieces of equipment; however, auto-negotiation only works if both devices are set to Auto. If one device is set to Auto and the other has any other setting, the auto device will configure itself as 100/Half. The most common cause of mismatch issues is the scenario where one device is set to 100/Full and the other is set to Auto.



  • If you are new to video conferencing over IP, you might have had a duplex mismatch in your network for a while. TCP traffic is slowed down by it, which might pass unnoticed, but UDP traffic is lost.
  • There are several tools that can detect packet loss over a route with the use of a large number of pings to every device on the route. This information helps you locate the devices that have a duplex mismatch. Change the device settings so that the devices at each end of a cable have either the same speed/duplex settings or are both set to Auto.

    • On Cisco-acquired Codian devices, this is set on the Network > Port A and Network > Port B pages. For more information, see the online help.

    • On the Cisco VCS, this is set on the Ethernet page (System > Ethernet). Cisco recommends that both the Cisco VCS and the Ethernet switch are set to Auto, unless the switch is unable to auto-negotiate, in which case both should be set to 1000/Full.
Updated: Nov 07, 2014
Document ID: 118431