Understanding Latency in IP Telephony
With an increasing interest in implementing and deploying IP Telephony applications, there is a rising need to understand the cause and effect of latency in the deployed system. This paper addresses these needs by reviewing the effect of latency on human conversations, analyzing the system components that incur the latency, and methods of managing the latency to maintain sufficient quality of service.
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Latency and QoS for Voice over IP
This paper will familiarize the reader with the fundamentals of a VoIP (Voice over IP) implementation and its effects. VoIP has been a front runner for companies looking to take advantage of IP. There are cost benefits, however with VoIP there are challenges. VoIP is latency driven therefore your Infrastructure must be able to support it. Latency is the delay that occurs when a packet crosses a network connection, from sender to receiver. Quality of Service (QoS) is yet another challenge. QoS challenges derive from different traffic types requiring different service levels from the network. QoS in a network must be adept of; prioritizing traffic types; interpreting traffic types (applications running over IP); and then conveying them over the network so that QoS requirements can be met. We will discuss the technical issues involved with assuring QoS, as well as solutions.
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Quality of Service Overview
Quality of Service is the term given to given data streams (more specificially IP packets) priority over a network (WAN, LAN etc.). The driving technology behind Quaility of Service is the introduction of Label Switching which allows the use of high speed ATM switches over normal IP networks.
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Solving QoS in VoIP : A Formula for Explosive Growth?
What users and their organizations expect from VoIP is essentially PSTN quality and objective verification that they are receiving it. VoIP service providers must meet these expectations if they want to profit from faster market penetration.
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IP RTP Priority
The IP RTP Priority feature provides a strict priority queueing scheme for delay-sensitive data such as voice. Voice traffic can be identified by its Real-Time Transport Protocol (RTP) port numbers and classified into a priority queue configured by the ip rtp priority command. The result is that voice is serviced as strict priority in preference to other nonvoice traffic.
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Overcoming Barriers to High-Quality Voice over IP Deployments
Discusses the Quality of Service (QoS) issues that are critical to the successful deployment of Voice over IP (VoIP) systems. Such impairment factors as latency, jitter, packet loss, and echo must be considered along with the ways in which they interact.
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Indepth: Packet Loss Burstiness
This paper outlines some key packet loss models, provides some analysis of packet loss data, discusses the degree of "fit" of models and data and proposes the use of a 4-state Markov model to represent loss distribution.
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Indepth: Jitter Sources
This contribution discusses the root causes and statistical characteristics of jitter, provides some practical measurement results and then discusses ways in which jitter can be measured and modeled. Finally the operation of jitter buffers is briefly discussed in order that the interaction between jitter and jitter buffers can be better understood.
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