Cisco Systems 7920 IP manual ∙ Delay Variation Jitter Not to exceed 30ms

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Voice traffic can be classified with the following characteristics:

∙Smooth ￿ VoIP packets are sent at consistent intervals with uniform packet sizes.

∙Benign ￿ VoIP packets only attempt to use the bandwidth necessary to send from end to end. VoIP does not use any windowing to determine data rates.

∙Packet Loss Sensitive ￿ VoIP traffic is extremely sensitive to packet loss. Excessive loss degrades overall voice quality.

∙Delay Sensitive ￿ While VoIP can tolerate some amount of delay, excessive delay or excessive delay variation (jitter) degrade overall voice quality.

∙User Datagram Protocol (UDP) Best Effort ￿ VoIP sends Real Time Protocol (RTP) packets using UDP. UDP does not have a mechanism to retransmit lost packets.

The network guidelines defined by Cisco AVVID for proper VoIP operation are as follows:

∙Delay ￿ Not to exceed 150 ms (one way).

∙Delay Variation (Jitter) ￿ Not to exceed 30ms.

∙Packet Loss ￿ Not to exceed 1 percent.

Note: While isolated testing may show that VoIP calls could operate in a network outside of these guidelines, deploying a VoIP network under those conditions cannot be predictably engineered. Support from the Cisco

Cisco − Wireless IPT Design Guide for the Cisco 7920 IP Phone

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Contents Table of Contents Requirements Introduction Prerequisites Wlan Overview Cisco 7920 IP Phone OverviewRF Overview Site Surveys and Design Recommendations Components UsedRssi VoIP QoS∙ Delay Variation Jitter Not to exceed 30ms Security for the Cisco 7920 and Wlan Networks Number of 802.11b IP Phones per AP Network SizingNumber of 802.11b Devices per AP Page Numbers of 802.11b Phones per Layer 2 Subnet or Vlan Understanding Roaming Terminology Understanding Layer 2 and Layer 3 RoamingLayer 2 Roaming Page Layer 3 Roaming VLANs Wlan QoS for VoIP Page Page Page Interconnecting WLANs to Cisco Campus Infrastructure Connecting APs to the Catalyst 3550 SMI or EMI Connecting APs to the Catalyst 2950 SI Connecting APs to the Catalyst 2950 EICaveats and Limitations Other Caveats and Limitations Call Admission ControlDesigning Around the Lack of Layer 3 Roaming Related Information
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