Canon H323 manual 10 QoS, Potential VoIP Problems

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IP Office H323 IP Phones: Voice Compression

1.10 QoS

When transporting voice over low speed links it is possible for normal data packets (1500 byte packets) to prevent or delay voice packets (typically 67 or 31 bytes) from getting across the link. This can cause unacceptable speech quality.

Therefore, it is vital that all traffic routers and switches in the network to have some form of Quality of Service (QoS) mechanism. QoS routers are essential to ensure low speech latency and to maintain sufficient audible quality.

IP Office supports the DiffServ (RFC2474) QoS mechanism. This is based upon using a Type of Service (ToS) field in the IP packet header. On its WAN interfaces, IP Office uses this to prioritize voice and voice signalling packets. It also fragments large data packets and, where supported, provides VoIP header compression to minimize the WAN overhead.

Note

IP Office does not perform QoS for its Ethernet ports including the WAN Ethernet port on the Small Office Edition.

1.11 Potential VoIP Problems

It is likely that any fault on a network, regardless of its cause, will initially show up as a degradation in the quality of VoIP operation. This is regardless of whether the fault is with the VoIP telephony equipment. Therefore, by installing a VoIP solution, you must be aware that you will become the first point of call for diagnosing and assessing all potential customer network issues.

Potential Problems

End-to-End Matching Standards

VoIP depends upon the support and selection of the same voice compression, header compression and QoS standards throughout all stages of the calls routing. The start and end points must be using the same compression methods. All intermediate points must support DiffServ QoS.

Avoid Hubs

Hubs introduce echo and congestion points. If the customer network requires LAN connections beyond the capacity of the IP Office Unit itself, Ethernet switches should be used. Even if this is not the case, Ethernet switches are recommended as they allow traffic prioritization to be implemented for VoIP devices and for other device such as the Voicemail Server PC.

Power Supply Conditioning, Protection and Backup

Traditional phone systems provide power to all their attached phone devices from a single source. In a VoIP installation, the same care and concern that goes into providing power conditioning, protection and backup to the central phone system, must now be applied to all devices on the IP network.

Multicasting

In a data only network, it is possible for an incorrectly installed printer or hub card to multicast traffic without that fault being immediately identified. On a VoIP network incorrect multicasting will quickly affect VoIP calls and features.

Duplicate IP Addressing

Duplicate addresses is a frequent issue.

Excessive Utilization

A workstation that constantly transmits high traffic levels can flood a network, causing VoIP service to disappear.

Network Access

An IP network is much more open to users connecting a new device or installing software on existing devices that then impacts on VoIP.

Cabling Connections

Technically VoIP can (bandwidth allowing) be run across any IP network connection. In practice, Cat5 cabling is essential.

H323 IP Telephone Installation

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IP Office Release 6

15-601046 Issue 16a (15 March 2010)

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Contents IP Office Release H323 IP Telephone InstallationH323 IP Telephone Installation IP Office Release Contents Page Chapter IP Office H323 IP Phones Page ∙ Network Assessment IP Office H323 IP PhonesIP Office Release What is NewIP Office Supported Phones IP Office Unit System CapacityExtension Capacity Call CapacityPhone Firmware Simple Installation Installation Requirements IP500 and IP500 V2 IP Office Systems LicensesOther IP Office Systems ∙ Warning a Network Assessment is Mandatory Network Assessment∙ G711 20ms ∙ G723a 80ms ∙ G729 40ms Call Type Voice Compression Channel Usage Voice CompressionMeasuring Channel Usage Installing VCM Cards10 QoS Potential VoIP ProblemsUser PC Connection ∙ Avaya 1151D1 Power Supply Unit PSU Power Supply OptionsSpare Wire Power Options Dedicated Plug-Top Power Supply Units∙ IP Phone Inline Adaptor 802.3af Power over Ethernet PoE Options∙ Avaya 1152A1 Power Distribution Unit Mid-Span Power Unit ∙ Power of Ethernet POE SwitchFile Server Description Up to File Server OptionsPhones File Auto Generation Control Unit Memory Card Transferring Files Using IP Office ManagerPage Chapter Installation Installation Dhcp Server ∙ o Dhcp ModeIP Phone Software and Settings Files ∙ Secondary Site Specific Option Number IP Office 4.2+Adding Licenses Creating/Editing the Settings File 1600/9600 Series Phone Languages Backup/RestoreLanguage File Manually Creating Extensions Phone Connection ∙ To switch to static address installationStatic Address Installation Phone Registration ∙ Password =∙ Ext. = Phone Security Extension & User SetupSpecifying the Bruri Value Backup RestoreHttp Authentication Manual Backup/Restore ControlABKNUMBERmmm Series Phone Backup FileField Description ABKNAMEmmmSelect Properties Http Server Configuration for Backup/RestoreListing Registered Phones Error Messages Chapter Other Installation Options VPN Remote Phones Other Installation OptionsVPNremote Phone Installation DocumentationSupported VPNremote Phone Firmware Product Section Title Doc ReferenceEnable VPN Phone Allowed Configuring the IP Phone for VPNremoteType Description Advantages Disadvantages Vlan and IP PhonesVlan and Dhcp Option Data Vlan Dhcp Settings Voice Vlan Dhcp SettingsDhcp Option Description HP-Switch Configuration Example setup OverviewPort Vlan Description Voice Data HP Procurve CLI outputOption Value Example System OverviewPort Vlan 209 Voice Vlan 210 Data Page Chapter Static Administration Options ∙ 4601, 4602, 5601, 5602 Speaker key Static Administration OptionsEntering Data for Administrative Options Hold vs MuteSecondary Ethernet Hub/IR Interface Enable/Disable QOS Option SettingsView Details ∙ If self-test passes Self-Test Procedure∙ If self-test fails Resetting a Phone Resetting a PhoneClearing a Phone Setting the Sson on IP Office Setting the Sson on an IP PhoneSite Specific Option Number ∙ Headset AGC = Switching automatic gain control on/offAutomatic Gain Control ∙ Handset AGC =Chapter Restart Scenarios Restart Scenarios Correct Boot File and Application File Already Loaded Boot File Needs UpgradingNo Application File or Application File Needs Upgrading Page Chapter Infrared Dialling ∙ Dial a Number to Start a Call Infrared Dialling∙ Swap Text Files During a Call Windows Pocket PC Enabling the IR PortDialling Phone Numbers Palm OrganizerBeaming Files During a Call Chapter Alternate Dhcp Server Setup Alternate Dhcp Server Setup Checking for Dhcp Using a Windows Dhcp ServerWindows Dhcp Setup for H323 IP Phones Select Start Programs Administrative Tools Dhcp∙ Data type String ∙ Code 2b. Adding a 242 Option2c. Adding a 176 Option Alternate Options Chapter WML Server Setup What WML is Supported WML Server SetupIntroduction Testing 4620 WML Browsing Using XitamiInstalling the Web Server Configuring the Xitami Web Server for WAP4a. Creating a Simple WML Installing Sample WML PagesSET Wmlport Setting the HomeMicrosoft IIS Web Server WML Configuration Apache Web Server WML Configuration∙ Associated extension wml Case 3. Input Box Followed by a Submit Button Open URL EntryCase 1. Input Box Followed by an Anchor Tag Case 2. Input Box Followed by an a TagPage 1719,TFTPSRVR IndexAvpp AddrAscii AsdmDhcp CD/DVDConflict LANWins END of Avaya 4620 IP PhoneEND of File GEN GETIPO LIC VCMLAN1 L2 QOSL2QVLAN MimePWB SN Sson Sson SET Dnssrvr SET DomainSET Smblic SET Wmlcoding Ascii SET Wmlhome SET Wmlport 8000Tftpsrvr 47 URLTftp TftpdirWAP H323 IP Telephone Installation IP Office Release Avaya Inc. All rights reserved