QoS Requirements for Data Collaboration Using T.120

QoS Requirements for Data Collaboration Using T.120

Liane Tarouco

RNP2

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

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

T.120 & H.323

Transport Network (ISDN, Switched-56, ...)

H.221 Multiplex and Framing

H.233 - Encryption

H.230

H.242

Ctrl

H.243

Multi-point

H.234

KeyExch

VIDEO AUDIO H.224

G.711G.722G.728

G.723.1G.729

H.261

H.262H.263

H.281

Far endcameracontrol

T.123

T.122/T.125MCS

T.124Generic

ConferenceControl

ApplicationProtocols

T.126T.127

TimeCriticalApps

AECAGC

Noise-Suppress

Pre-procPost-proc

CONFERENCING APPLICATIONS & USER INTERFACE

BAS ECS

H.323 components

6

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

H.323 components

7

Manages conference using H.245 and may use T.120 commands

Establishes common conference mode• Common set of media streams• May provide audio transcoding

Multipoint Control Unit MCU

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

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

Messages & procedures

10

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

Standards

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

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.

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

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

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

Tools for collaboration

Whiteboard Application sharing Remote control Chat File transfer Printed documents sharing

(document camera)

Videoconference needs complement for supporting collaboration:

H.323 e T.120

ITU-T T.120 series

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File

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App

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Res

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A/V

Con

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Application Protocols T.126 - Still Image, T.127 - File TransferT.130 - A/V Control, T.SHARE, T.RES

T.124 - Generic Conference Control

T.123 - Transport Stacks

ISDN POTSVoice/Data

LAN ATM

MC

U T.122 / T.125 - Multipoint Comm. Service

T.126 T.127

TE

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T.130

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

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

Protocols T.120 T.123 - OSI transport protocol T.122, T.125 - Multipoint Communication Service

(MCS): T.124 -Generic Conference Control (GCC)

MCS service primitives

MCS domain management primitives MCS Channel Management primitives MCS data transfer primitives MCS token management 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


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


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

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)

GCC

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

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.

GCC - Functional Units

Conference establishment and termination Conference roster Application roster Application registry Conference conductorship Miscellaneous functions

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


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


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

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

Conformance for T.120 service

Transport protocol profile (T.123); MCS Multipoint Communication Service

(T.125); Required components of Generic Conference

Control (T.124);

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

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

data,

video

audio

Applications

Broadcast application

Application Sharing

Required services in H.323 & T.120Required services in H.323 & T.120

Teaching and learning environment Teaching and learning environment

Lecture delivery performanceLecture 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.

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 closedEvent> 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 downEvent> Mon Nov 26 17:18:55 2001 Pkts in 3324 Pkts Event> client Alexei Korb - T.120 session closed due to insufficient bandwidthEvent> 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 bandwidthEvent> Mon Nov 26 17:21:57 2001 Pkts in 7114 Event> Mon Nov 26 17:22:58 2001 Pkts in 8182

QoS

Quality of Service - needed quality to attend specific application user request– telephony– videoconference– file download– TV

QoS Usual specifications

– Bandwidth – Delay – Jitter

QoS from user point of view ?– ITU P800 Perceptual Speech Quality

Measurement (PSQM)– Mean Opinion Scores (MOS)

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)

Providing QoS

Rede TCHÊ– Videoconference QoS service

UFRGS intranet– Ftp impact

RNP

TCHÊ - Videoconference

TCHÊ - Videoconference

Problems – Packet dropping high (> 30%) – Traffic burst impact video transmission even when

normal bandwidth usage was not too high

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

Collaborative software development

Add T.120 service to Open H.323– Protocols and services study and monitoring

Other collaborative work Collaboration with Open RCT project

from UCDavis– Whiteboard– Java based– Open Software

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

Lite T.124 profile Only a subset of the GCC services needed

– conference establishment and termination– support for the conference roster– support for a single application roster

Neither the application registry or the conference conductorship services are needed.

Also, no miscellaneous functions are required other than the sending of text messages.

Conclusions

QoS for collaborative services (H.323 & T.120)

T.120 like protocols are needed but lightweight versions must be defined, implemented, tested and standardized