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 13 2

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 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
Q.931 defined in H used to setup and tear down call
RAS messages used between endpoints and Gatekeeper for registration, admission and status
H.245 is used to control the connection and the media
Supplementary services based on Q.SIG
call forward and diversion defined for version 2 of H.323 in H.450.X 19

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

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 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):
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: Pkts in Pkts
Event> client Leandro Bertholdo - T.120 session closed
Event> Mon Nov 26 17:16: Pkts in Pkts
Event> Mon Nov 26 17:17: Pkts in Pkts
Event> client Alexei Korb timeout -- holding down
Event> Mon Nov 26 17:18: Pkts in Pkts
Event> client Alexei Korb - T.120 session closed due to insufficient bandwidth
Event> Mon Nov 26 17:19: Pkts in 4708
Event> Mon Nov 26 17:20: Pkts in 5850
Event> client Liane Tarouco - T.120 session closed due to insufficient bandwidth
Event> Mon Nov 26 17:21: Pkts in 7114
Event> Mon Nov 26 17:22: Pkts in 8182

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

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

43. 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)

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

45. TCHÊ - Videoconference

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

47. 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

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

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

50. 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

51. 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.

52. 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