Ansi/tia-921-b network Model for Evaluating Multimedia Transmission Performance Over the Internet Protocol



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ANSI/TIA-921-B

Network Model for Evaluating Multimedia Transmission Performance Over the Internet Protocol


Table of Contents


ANSI/TIA-921-B 1

Network Model for Evaluating Multimedia Transmission Performance Over the Internet Protocol 1

Foreword 2

Introduction 3

Network Model for Evaluating Multimedia Transmission Performance Over the Internet Protocol 5

1Scope 5

2Informative References 6

3Definitions and Abbreviations 7

3.1Definitions 7

3.2Abbreviations 8

4Description of the Model 9

4.1Model Overview 9

4.2Network Topology 10

4.3Models of Network Elements 11

4.4Interfering Stream Files 13

4.5Simulation Inputs 14

4.6Simulation Outputs 16

4.7Packet Scheduling Algorithm 18



5IP Network Impairment Level Requirements 19

5.1Service Test Profiles 19

5.2Impairment Combination Standard Test Cases 20

6Using the Network Model 26

6.1Using the Simulator 26

6.2Using a Real-Time Hardware Emulator 27

6.3Hardware Emulator Considerations 27

6.4Advanced Uses of the Network Model 28



Foreword


(This foreword is not part of this Standard.)
ANSI-accredited committee TR-30.3 has developed this ANSI/TIA-921-B Standard, which defines an IP network model. This model, along with the specified scenarios, are intended for evaluating and comparing communications equipment connected over a converged network.
Building upon the experience of creating network models, TR-30.3 Subcommittee has created this Network Model for IP Impairments using the similar methodology developed in its previous standards and Telecommunication Systems Bulletins:

EIA/TIA-496-A-1989: Interface Between Data Circuit Terminating Equipment (DCE) and the Public Switched Telephone Network, which includes a Network Model for Evaluating Modem Performance

TIA TSB-37-A-1994: Telephone Network Transmission Model for Evaluating Analog Modem Performance, which became ITU-T Recommendation V.56bis-1995

TIA TSB-38-1994 (and TSB-38-A -2007): Test Procedures for Evaluation of 2-Wire 4 Kilohertz Voice Band Duplex Modems, which became ITU-T Recommendation V.56ter-1996

ANSI/TIA/EIA-3700-1999: Telephone Network Transmission Model for Evaluating Analog Modem Performance

ANSI/TIA/EIA-793-2001: North American Telephone Network Transmission Model for Evaluating Analog Client and Digitally Connected Server Modems

ANSI/TIA-876-2002: North American Network Access Transmission Model for Evaluating xDSL Modem Performance
ANSI/TIA-921-B was approved on August 9, 2011. It cancels and replaces TIA-921-A (2008) in its entirety. Technical changes from TIA-921-A include:

  • ANSI/TIA-921-B models the mechanisms that contribute to packet delay, jitter, and loss: interfering streams, queueing delays in network elements, and the characteristics of specific access technologies. The intent is to provide more realism than the earlier version.

  • TIA-921-A defined a Gilbert-Elliott mathematical model that fit certain observed network behavior, but was not easily extended to other scenarios. The new approach is based on discrete event simulation.

  • The “likelihood of occurrence” concept is no longer applied to IP networks.

  • ANSI/TIA-921-B is a true bidirectional model.

  • Impairment levels are updated to keep current with evolving IP networks.

  • The number of standard test cases is greatly reduced.

  • Users can customize test cases to fit their specific needs.

There are six normative Annexes in this Standard. Annex F is an electronic attachment that contains the following files:
./src Discrete Event Simulator Source (Annex B)

./pcap Input Packet Capture Files of Interfering Traffic (Annex C)

./tc Impairment Combination Standard Test Cases (section 5.2)

./out Simulator Output (Annex D)


Introduction

ANSI/TIA-921-B describes an Internet Protocol (IP) network model for the purpose of evaluating the performance of IP streams. The focus is on packet delay, delay variation, and loss. IP streams from any type of network device can be evaluated using this model.


Emphasis is given to the fact that manufacturers of communications equipment and service providers are interested in a specification that accurately models the IP network characteristics that determine performance. Evaluators desire a definitive set of simple tests that properly measure the performance of communications devices from various manufacturers. Therefore, the objective of this Standard is to define an application-independent model (e.g. data, voice, voiceband data, and video) that is representative of IP networks, that can be simulated at reasonable complexity, and that facilitates practical evaluation times. The IP network model presented herein represents a snapshot of actual network data provided by anonymous IP service providers and IP network equipment manufacturers in the 2010 timeframe, and will continue to evolve as more statistical information becomes available and as the IP network evolves.
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Network Model for Evaluating Multimedia Transmission Performance Over the Internet Protocol


1Scope

This Standard is broadly applicable to the evaluation of any equipment that terminates or routes traffic using the Internet Protocol. This Standard can also be used to evaluate media streams or other protocols carried over IP networks. Examples of the types of equipment that can be evaluated using this model include:



  • IP-connected endpoints:

    • IP network devices (such as: user agents, call agents, media servers, media gateways, application servers, routers, switches, etc.)

    • IP video (IPTV, video conferencing, telepresence, etc.)

    • IP phones (including soft phones)

    • IAF (Internet Aware Fax)

  • PSTN-connected devices through IP gateways:

    • POTS through Voice-over-IP (VoIP) gateways

    • T.38 facsimile devices and gateways

    • V.150.1 and V.152 (voiceband data, VBD) modem-over-IP gateways

    • TIA-1001 and V.151 textphone-over-IP gateways

The IP network model can be used in two ways:



  • Test an IP stream under simulated network conditions

  • Test an IP stream in real time using hardware emulation of the network model.

The IP network model can be used to study and to understand:

  • the interaction of different traffic mixes

  • the effects of QoS and queuing on different types of traffic

  • packet delay variation and packet loss.

Whether in software simulation or real-time hardware emulation, users can select from several test cases specified in this Standard. Users can optionally define their own test cases.
This model has the following limitations:

  • Some VoIP networks may utilize PSTN at one or both ends of the connection through a media gateway. This model only addresses the IP portion of the network and does not address the PSTN portion of the end-to-end connection.

  • The network model represented in this Standard does not model all possible connections that can be encountered between devices.

  • This Standard only specifically includes GPON and DSL access technologies. Characteristics of other access technologies such as CATV and wireless are for further study.

  • Abnormal events such as link failures and route flaps (and the packet reordering that such events can cause) are not included in this Standard.

  • The standard test cases use streams of interfering traffic that were captured on live networks. While realistic, they are still just examples; users could substitute their own files of interfering traffic.

  • The LAN-to-LAN test cases of TIA-921-A are now modeled as two cascaded ANSI/TIA-921-B core-to-LAN segments. See section 6.3.

  • The IP network model presented herein is based on an informal survey of anonymous IP service providers and IP network equipment manufacturers in the 2010 timeframe and will continue to evolve as more statistical information becomes available and as the IP network evolves.


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