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QoS Requirements for Data Collaboration Using T.120

This presentation discusses the investigation of T.120 protocol behavior for diagnosing data conference failures and explores the QoS requirements for data collaboration applications. The results of experiments using QoS approaches for videoconferencing and T.120 data collaboration in RNP2 are reported. New alternatives in collaboration software will also be discussed.

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QoS Requirements for Data Collaboration Using T.120

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  1. QoS Requirements for Data Collaboration Using T.120 Liane Tarouco RNP2

  2. Topics • This presentation will shows results of an investigation on the T.120 protocol behavior aimed to diagnose common data conference failures causes. • Specific quality of services requests, needed for this kind of applications will be reported as well as results of experiments using QoS approached for videoconference and T.120 data collaboration organized in RNP2 • New alternatives on collaboration software will be discussed

  3. Data collaboration applications • Data collaboration applications offer very useful services like application/desktop sharing to provide real remote collaboration specially for use in conjunction with videoconferencing. • T.120 based systems are the most used approach for this kind of applications providing interoperability between different vendors

  4. T.120 & H.323

  5. H.323 components

  6. H.323 components • Terminal • GK - gatekeeper (control and ‘routing’ ) • GW - gateway (access to other environments) • MC - multipoint controller • MP - multipoint processor ( mix ‘n match the media) • MCU - multipoint control unit • contains MC and MP optionally a T.120 MCU

  7. Multipoint Control Unit MCU • Manages conference using H.245 and may use T.120 commands • Establishes common conference mode • Common set of media streams • May provide audio transcoding

  8. Basic Operation • Endpoints register with gatekeeper to provide mapping between physical address and alias address • Endpoint asks gatekeeper for permission to place call to another endpoint • Endpoint signals call with other endpoint • Endpoints exchange media • Endpoints disconnect, notify gatekeeper

  9. Messages & procedures • Admissions & Directory Service • Creation of a connection • Endpoint capabilities exchange • Opening and closing logical channels • Changing modes (point-to-point - multipoint) • Real-time transmission over packet networks

  10. Standards • H.323 for architecture, procedures • H.225.0 more than just a document... • Q.931 ‘derived’ messages for call setup • RAS for endpoint-Gatekeeper signaling • H.245 for capabilities/media control • RTP/RTCP for media transport • Endpoint to endpoint after call setup • Open multiple logical channels (one per one way media) • T.120 for data

  11. RAS Functions (H.225) • Discovery/Registration - find gatekeeper and provide mapping between physical and alias addresses • Admission - ask permission to place call with bandwidth • Bandwidth Changes - ask permission to use more bandwidth • Status - report on call status • Disengage - report disconnect and release bandwidth

  12. Registration, Admission, and Status • Registration, admission, and status (RAS) is the protocol between endpoints (terminals and gateways) and gatekeepers. • The RAS is used to perform registration, admission control, bandwidth changes, status, and disengage procedures between endpoints and gatekeepers. • An RAS channel is used to exchange RAS messages. This signaling channel is opened between an endpoint and a gatekeeper prior to the establishment of any other channels.

  13. H.225/Q.931 • Q.931-like • Setup - initiate call from one entity to another • Alerting - called endpoint is “ringing” • Connect - called endpoint answered • Release Complete - disconnect call • others, including Facility, Information, Progress, Status

  14. H.245 • Capability negotiation - determine compatible set of media capabilities • Master/slave determination • Logical channel control - indicate desire to start transmission of specified medium • Multipoint conference control & indication - conference rosters, chair control, media indications • Miscellaneous

  15. H.245 Control Signaling • H.245 control signaling is used to exchange end-to-end control messages governing the operation of the H.323 endpoint. • These control messages carry information related to the following: • capabilities exchange • opening and closing of logical channels used to carry media streams • flow-control messages • general commands and indications

  16. Tools for collaboration Videoconference needs complement for supporting collaboration: • Whiteboard • Application sharing • Remote control • Chat • File transfer • Printed documents sharing (document camera)

  17. H.323 e T.120

  18. ISDN POTS Voice/Data LAN ATM ITU-T T.120 series T.126 T.127 T.130 Photos Whiteboard Overhead Proj Documents File Transfer A/V Control Switching App Sharing Reservations Application Protocols T.126 - Still Image, T.127 - File Transfer T.130 - A/V Control, T.SHARE, T.RES TERMINAL T.124 - Generic Conference Control T.122 / T.125 - Multipoint Comm. Service MCU T.123 - Transport Stacks

  19. ITU-T T.120 series • Kinds of data and standards • Photos and Documents (T.126) • Pointing and Annotating (T.126) • File transfer (T.127) • PC Application Sharing • Virtually any multipoint flow of data

  20. ITU-T T.120 series • Kinds of control & standadrds • Conference setup, entry, modify, exit (T.124) • Camera, mic, peripheral control (T.130) • Who sees whom (T.130) • Director control, browsing (T.130) • Reservations • Add site, extend conference time

  21. Protocols T.120 • T.123 - OSI transport protocol • T.122, T.125 - Multipoint Communication Service (MCS): • T.124 -Generic Conference Control (GCC)

  22. MCS service primitives • MCS domain management primitives • MCS Channel Management primitives • MCS data transfer primitives • MCS token management primitives

  23. MCS service primitives • MCS domain management primitives • MCS-CONNECT-PROVIDER request, indication, response, confirm • MCS-DISCONNECT-PROVIDER request, indication • MCS-ATTACH-USER request, confirm • MCS-DETACH-USER request, indication • MCS-DOMAIN-PARAMETERS request, indication, confirm

  24. MCS service primitives • MCS Channel Management primitives • MCS-CHANNEL-JOIN request, confirm • MCS-CHANNEL-LEAVE request, indication • MCS-CHANNEL-CONVENE request, confirm • MCS-CHANNEL-DISBAND request, indication • MCS-CHANNEL-ADMIT request, indication • MCS-CHANNEL-EXPEL request, indication

  25. MCS service primitives • MCS data transfer primitives • MCS-SEND-DATA request, indication • MCS-UNIFORM-SEND-DATA request, indication • MCS token management primitives • MCS-TOKEN-GRAB request, confirm • MCS-TOKEN-INHIBIT request, confirm • MCS-TOKEN-GIVE request, indication, response, confirm • MCS-TOKEN-PLEASE request, indication • MCS-TOKEN-RELEASE request, confirm • MCS-TOKEN-TEST request, confirm

  26. T.124 - Generic Conference Control (GCC): • T.124 - Generic Conference Control • Provides set of facilities to establish and manage multipoint . • Centralize an information base (state of serving conferences)

  27. GCC

  28. GCC • GCC provides a set of services for establishment and termination of conferences • GCC provides a means to create new conferences. • GCC provides a means of identifying which Application Protocol Entities are available at each node and to provide necessary information for Peer Application Protocol Entities to communicate with each other

  29. GCC • GCC provides a method for allowing a node to become a conductor for a conference. • A token is used by GCC to determine whether a conference is conducted or non-conducted. • The Application Registry is an active data-base residing at the Top GCC Provider that may be used to manage channels, tokens, and other shared resources used in a conference.

  30. GCC - Functional Units • Conference establishment and termination • Conference roster • Application roster • Application registry • Conference conductorship • Miscellaneous functions

  31. GCC - Conference establishment and termination • GCC-Conference-Create request • GCC-Conference-Create indication • GCC-Conference-Create response • GCC-Conference-Create confirm • GCC-Conference-Query request • GCC-Conference-Query indication • GCC-Conference-Query response • GCC-Conference-Query confirm • GCC-Conference-Join request • GCC-Conference-Join indication • GCC-Conference-Join response • GCC-Conference-Join confirm

  32. GCC - Conference establishment and termination • GCC-Conference-Disconnect request • GCC-Conference-Disconnect indication • GCC-Conference-Disconnect confirm • GCC-Conference-Terminate request • GCC-Conference-Terminate indication • GCC-Conference-Terminate confirm • GCC-Conference-Eject-User request • GCC-Conference-Eject-User indication • GCC-Conference-Eject-User confirm • GCC-Conference-Transfer request • GCC-Conference-Transfer indication • GCC-Conference-Transfer confirm

  33. GCC - Conference establishment and termination • GCC-Conference-Lock request • GCC-Conference-Lock indication • GCC-Conference-Lock response • GCC-Conference-Lock confirm GCC-Conference-Unlock request • GCC-Conference-Unlock indication • GCC-Conference-Unlock response • GCC-Conference-Unlock confirm • GCC-Conference-Lock-Report indication • GCC-Conference-Invite request • GCC-Conference-Invite indication • GCC-Conference-Invite response • GCC-Conference-Invite confirm • GCC-Conference-Add request • GCC-Conference-Add indication • GCC-Conference-Add response • GCC-Conference-Add confirm

  34. Conformance for T.120 service • Transport protocol profile (T.123); • MCS Multipoint Communication Service (T.125); • Required components of Generic Conference Control (T.124);

  35. Why are standards important? • Communication requires standards • Standards stimulate market growth • Instant credibility for new products • Customer confidence • Multiple vendors • Increased competition • Volume pricing • Standards are critical to interoperability, but still leave room for product variation • Many options in each standard • Audio and video quality depend on encoders, not decoders

  36. Additional standards • T.130 series, High level audio/video control • Remote cameras & VCRs, video routing, continuos presence • How a student request the floor to ask a question • Automatic video switching • Social rules e.g. hand raising are used • Submit and cancel floor requests

  37. Required services in H.323 & T.120 Teaching and learning environment data, video audio Application Sharing Applications Broadcast application

  38. Lecture delivery performance • T.120 protocols uses a lot of performance management and when the data channel or the end station do not perform according established thresholds unexpected decision may occur disconnecting one or more users from the conference or disabling some data collaboration function.

  39. Monitoring results • T.120 communication between terminals (Netmeeting), start before logical channels open • Centralized conference model (tightly coupled) use intensively MCU resources Event> Mon Nov 26 17:15:54 2001 Pkts in 25655 Pkts Event> client Leandro Bertholdo - T.120 session closed Event> Mon Nov 26 17:16:54 2001 Pkts in 27438 Pkts Event> Mon Nov 26 17:17:55 2001 Pkts in 1695 Pkts Event> client Alexei Korb timeout -- holding down Event> Mon Nov 26 17:18:55 2001 Pkts in 3324 Pkts Event> client Alexei Korb - T.120 session closed due to insufficient bandwidth Event> Mon Nov 26 17:19:56 2001 Pkts in 4708 Event> Mon Nov 26 17:20:56 2001 Pkts in 5850 Event> client Liane Tarouco - T.120 session closed due to insufficient bandwidth Event> Mon Nov 26 17:21:57 2001 Pkts in 7114 Event> Mon Nov 26 17:22:58 2001 Pkts in 8182

  40. QoS • Quality of Service - needed quality to attend specific application user request • telephony • videoconference • file download • TV

  41. QoS • Usual specifications • Bandwidth • Delay • Jitter • QoS from user point of view ? • ITU P800 Perceptual Speech Quality Measurement (PSQM) • Mean Opinion Scores (MOS)

  42. MOS - Mean Opinion Scores • Bad: unintelligible, user do not understand decoded message. Interruptions due degradation • Poor: signal present interruption due degradations; user needs considerable effort to understand some segments • Moderate: voice quality is bad; user fell annoyed with degradations but there are no interruption and still can understand the message (requires moderated effort) • Good: voice is good to listen, user perceive degradations but do not bother because are minimal (no big effort is needed) • Excellent: user can not differentiate original message from corrupted, that means, do not perceive signal degradation (no effort is required)

  43. Providing QoS • Rede TCHÊ • Videoconference QoS service • UFRGS intranet • Ftp impact • RNP

  44. TCHÊ - Videoconference

  45. TCHÊ - Videoconference • Problems • Packet dropping high (> 30%) • Traffic burst impact video transmission even when normal bandwidth usage was not too high

  46. Tchê • Used IBM router implementation of DiffServ together with RSVP • LLQ used to keep compatibility with Cisco • Defined a service called HVIDEO (Expedited Forwarding) for video originated in the MCU and in the streaming video server • Band reservation (19%) for HVIDEO • Defined a service called CACHE (Assured Forwarding) for traffic using existing cache structure • Band reservation (15%) for CACHE

  47. Collaborative software development • Add T.120 service to Open H.323 • Protocols and services study and monitoring

  48. Other collaborative work • Collaboration with Open RCT project from UCDavis • Whiteboard • Java based • Open Software

  49. T-Lite • A lightweight T.120 profile that can be implemented in products requiring minimal data services. • They also can be implemented with less effort than traditional T.120 enhanced multimedia terminals

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