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TANDBERG D11624 - page 1
Video on Frame Relay Tandberg D11624 rev 01 ...
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TANDBERG D11624 - page 2
Tandberg Video on Frame Relay D11624 rev. 01 2 Table of Contents 1. Introduction ............................................................................................................................................... 3 2. Background on transmission of video over frame relay ................................................................... ...
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TANDBERG D11624 - page 3
Tandberg Video on Frame Relay D11624 rev. 01 3 1. Introduction This document is designed as an 'eye-opener' to video over frame relay and the idea is to show a solution that works. The equipment described in this document is the VFX-250S, a framer unit from Science Dynamics Corporation. Tandberg video conferencing codecs are being used ov ...
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TANDBERG D11624 - page 4
Tandberg Video on Frame Relay D11624 rev. 01 4 2. Background on transmission of video over frame relay The successful transmission of digitised voice over public frame relay data services the past few years has drawn attention to the question of whether video services can be transmitted over the same link. Voice, data & video over frame relay D ...
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TANDBERG D11624 - page 5
Tandberg Video on Frame Relay D11624 rev. 01 5 3. Technical issues There are two potential technical issues, which may affect the quality of packetised, digitised video. One is delay, or more properly jitter. Jitter is the variation in delay from one frame to the next. This is critical for video, as video requires a constant bit stream in order to ...
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TANDBERG D11624 - page 6
Tandberg Video on Frame Relay D11624 rev. 01 6 Cell based systems cut packet into fixed sizes Dropped frames are potentially a more serious problem. The frame relay standard allows the network service provider to control congestion by simply disposing of any frames which exceed the users CIR. In other words, if you contract for a CIR of 128 kbps bu ...
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TANDBERG D11624 - page 7
Tandberg Video on Frame Relay D11624 rev. 01 7 2. The second method is to establish a traffic prioritisation scheme for any channels carrying video through a FRAD (Frame Relay Access Devices) on a defined DLCI. This ensures that video frames are first out. Therefore, intelligent buffer management ensures video frames, which are less tolerant of del ...
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TANDBERG D11624 - page 8
Tandberg Video on Frame Relay D11624 rev. 01 8 framer both at the ACT-recommended setting of 256 bytes and at 1.500 bytes (which is in line with the recommendations of other framer users) without any difference in the overall performance. You can connect either the VFX-250S or the ABL VT2C directly to a DSU/CSU on a frame relay network. The two pro ...
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TANDBERG D11624 - page 9
Tandberg Video on Frame Relay D11624 rev. 01 9 6. Application Overview The diagram below shows the use of the VFX-250S in a video-conferencing over frame relay application. In this application the VFX-250S takes the H.320 datastream from the end point video-conferencing equipment and packetises it into a frame relay format for transmission over the ...
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TANDBERG D11624 - page 10
Tandberg Video on Frame Relay D11624 rev. 01 10 7. Technical Specification of VFX-250S 7. 1 Network & User Interface Connector: Female 37-pin D type to user equipment (Video codec) Male 37-pin D type to network equipment (FRAD) Interface: RS449 (X.21, V.35 and others with adapter cables) RS422 balanced drivers and receivers and RS423 receivers ...
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TANDBERG D11624 - page 11
Tandberg Video on Frame Relay D11624 rev. 01 11 • 4 configuration entries, each of which contains TX and RX DLCI settings, User Clock Speed, Packet Length, and AVB • LMI type control selection & parameter entry (ITU Annex A, ANSI Annex D, Frame Relay Forum, or Off) • Master, Slave, or Auto-assign settings for Enhanced Buffer Management ? ...
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TANDBERG D11624 - page 12
Tandberg Video on Frame Relay D11624 rev. 01 12 8. Approvals FCC Class A Digital Devices and Peripherals This equipment has been tested and found to comply with the limits for a Class A digital device, pursuant to Part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference when the equipment is ...
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TANDBERG D11624 - page 13
Tandberg Video on Frame Relay D11624 rev. 01 13 10. Economics of Video over Frame Relay The economics of video over frame relay are similar to those driving the use of voice over frame relay. Voice over frame relay is fairly well accepted as being economical when used in international applications. With international ISDN call prices frequently exc ...
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TANDBERG D11624 - page 14
Tandberg Video on Frame Relay D11624 rev. 01 14 11. Appendix A: Cables and Pinouts 11. 1 Standard Console Cable The console port on the VFX-250S conforms to EIA-232/V.24 electrical specifications. ...
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TANDBERG D11624 - page 15
Tandberg Video on Frame Relay D11624 rev. 01 15 11. 2 Standard EIA-449/RS449 Cables 11. 2 .1 Network Cable 11. 2 .2 User Cable A note about RTS signalling: Some manufacturers state that their network interface is RS449 (which uses RS422 signalling levels) but actually use RS423 signals for the control leads. If this is the case, then check the posi ...
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TANDBERG D11624 - page 16
Tandberg Video on Frame Relay D11624 rev. 01 16 11. 3 Standard EIA-530/RS530 Cables 11. 3 .1 Network Cable 11. 3 .2 User Cable ...
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TANDBERG D11624 - page 17
Tandberg Video on Frame Relay D11624 rev. 01 17 11. 4 Standard V.35 Cables 11. 4 .1 Network Cable 11. 4 .2 User Cable ...
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TANDBERG D11624 - page 18
Tandberg Video on Frame Relay D11624 rev. 01 18 12. Appendix C: Glossary and abbreviations AVB - Automatic Variable Buffer. Buffering - This is a term used to describe a method where data is held in a queue to allow equalisation of speeds on either side. CIR - Committed Information Rate Codec - A device, which takes an analogue or digital video sig ...
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TANDBERG D11624 - page 19
Tandberg Video on Frame Relay D11624 rev. 01 19 - This is a Videoconferencing term, which is used to identify picture break-up. Digital video pictures are made up of 1000’s of pixels, each representing a colour on the image. In videoconferencing, pixels are grouped into blocks (the number of which is determined by the speed of the link). Pixelati ...
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