FAA Presentation

1
Advanced 2 Developers Guide to FAA VoIP
Henning Schulzrinne, Supreeth Subramanya, Xiaotao
Wu Department of Computer Science Columbia
University
Date Feb 21, 2008
2
Discussion Flow

• The Bigger Picture
• A VoIP Review
• Classroom VoIP system
• Lab VoIP system
• Conclusion

3
Discussion Flow

• The Bigger Picture
• VoIP review
• Classroom VoIP system
• Lab VoIP system
• Conclusion

• FAA whats that?
• What is IRT doing there?
• How are the ATCs Trained?

4
The Bigger Picture (1/4)

• Federal Aviation Administration (FAA)
• An agency of the U.S. Department of
  Transportation with authority to regulate and
  oversee all aspects of civil aviation in the U.S.

• FAA Academy
• The education and training division of FAA
• Provides training to all personnel of aviation
  community
• Were working with a group responsible for
  training the Air Traffic Controllers (ATC)

5
The Bigger Picture (2/4)

• ATC Training levels
• Low fidelity instructional games, individual
  training
• Medium fidelity real time interactive training
• Full fidelity complex interactions, real
  hardware

Photos - http//www.cba.uri.edu/classrooms/picture
s/computerlab.jpg http//www.lockheedmartin.co
m/data/assets/10307.jpg
6
The Bigger Picture (3/4)

• FAA Academy Communication System
• Three parallel networks in every classroom and
  lab
• Data Network (Fast or Gigabit Ethernet)
• Voice Network (Analog, hardwired point-to-point
  connections)
• Video Network (Graphical simulations)

Hardware-based

• Disadvantages
• Difficult to add new training scenarios
• Uses obsolete equipments, no longer available
  without custom manufacture

• Solution convergence of Data and Voice networks
• Digital vs. analog
• Better utilization of bandwidth
• Reconfigurability in connections

Software-based
7
The Bigger Picture (4/4)

• What are the ATCs trained on?
• Learning to use air traffic control devices
  displays
• Communicating and coordinating with Pilots / ATCs
• Many more aspects
• Learning the air traffic rules
• Developing a mental picture of
• air-space and air-timing

• Why should we care?
• We are designing the communication system
• Well have to use air traffic control devices and
  displays for input/output

Photo - http//www.aeroport.public.lu/pictures/en/
administration/atc/atc_003.jpg
8
Discussion Flow

• The Bigger Picture
• VoIP review
• Classroom VoIP System
• Lab VoIP System
• Conclusion

• VoIP Protocol Perspective
• The World of SIP

9
VoIP Review

• What protocols are needed?
• Signaling protocols to establish presence,
  locate users, set up, modify and tear down
  sessions
• Media Transport protocols for transmission of
  packetized audio/video
• Support protocols for Gateway Location, QoS,
  inter-domain AAA, address translation, NAT
  traversal, resolution of phone numbers etc.
• What protocols are there?
• Signaling SIP, RTSP (IETF), H.323 (ITU-T)
• Media transport RTP
• Transport UDP, TCP
• Supporting protocols DNS, RSVP, ICE, ENUM

http//www.ietf.org http//www.ietf.org/rfc/rfcxxx
x.txt
AAA Authentication, Authorization, Accounting
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PROTOCOL ZOO
VoIP Review
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Find me then call me
VoIP Review (SIP)
Registrar
Hey, this is Tony, I am in cs.columbia.edu
domain I am at 128.59.19.251
Where is Tony?
He is at 128.59.19.251
Invite Tony for a conversation
I want to talk to Tony
Proxy
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SIP REQUESTS
VoIP Review (SIP)
Basic
Extended
Request purpose Code
Establish a session to receive future information updates SUBSCRIBE
Deliver information after SUBSCRIBE NOTIFY
Upload status information to server PUBLISH
Request another UA to act upon a URI REFER
Transport an instant message MESSAGE
Update session state information UPDATE
Request purpose Code
Establish a session with offer/answer INVITE
Acknowledge a response to an INVITE ACK
Query the capabilities of a server/UA OPTIONS
Cancel a pending request CANCEL
Terminate an existing SIP session BYE
Temporarily bind a device URI REGISTER
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VoIP Review (SIP)
SIP RESPONSES
Class Code Examples
Informational 1xx 100 Trying 180 Ringing
Success 2xx 200 OK
Redirection 3xx 301 Moved Permanently 305 Use Proxy
Client Error 4xx 401 Unauthorized 404 Not Found
Server Error 5xx 503 Service Unavailable
Global Failure 6xx 600 Busy Everywhere 606 Not Acceptable

• Borrowed from HTTP
• xyz explanatory text
• Uses x80 and higher codes to avoid conflicts with
  future HTTP response codes

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SIP CALL FLOW
VoIP Review
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Services/Features/Functions
VoIP Review
SIP CGI, CPL, SIP Servlet
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SIP CGI
VoIP Review

• Similar to HTTP CGI, an interface for service
  programming on SIP servers
• Invoke a service application as another process
• Expose SIP messages (method, headers, and
  content) through environment variables and stdin
  to the service application
• The application then generate user wanted
  responses to stdout, pipe to SIP server

output from the application
INVITE
server process
env(REQUEST_METHOD) INVITE env(REQUEST_URI)
sipiids_at_domain.com
invoke
puts
application
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Media transmission
VoIP Review
Please send audio to 192.168.1.101 port
10000using RTP with G.711 codec 20 ms
packetization period
Ok, got it, Please send audio to 192.168.1.102
port 20000using RTP with G.711 codec 20 ms
packetization period
INVITE with SDP
200 Ok with SDP
Ok, acknowledged
ACK
RTP with packetized audio data
18
Discussion Flow

• The Bigger Picture
• A VoIP Primer
• Classroom VoIP system
• Lab VoIP system
• Conclusion

• Communication Requirements
• Translation to SIP domain
• Bundling things together

19
The Classroom VoIP System (1/12)

• Overview
• Consists of up to 26 Students (ATC, Pilot) and 1
  instructor
• Students and instructor use computer and
  push-to-talk (PTT) device
• Instructor loads a flight scenario and
  teaches/tests the students

Single Sector Scenario
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The Classroom VoIP System (1/12)

• Overview
• Consists of up to 26 Students (ATC, Pilot) and 1
  instructor
• Students and instructor use computer and
  push-to-talk (PTT) device
• Instructor loads a flight scenario and
  teaches/tests the students

Dual Sector Scenario
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The Classroom VoIP System (2/12)

• Four Communication scenarios
• ATC communicates with the pilots in his sector
  (radio broadcast)
• ATC communicates with neighboring ATCs during
  pilot handoff (point-to-point)
• Instructor may monitor students (i.e. listen to
  what they hear/talk)
• Instructor may record the training sessions

One ATC may talk to many entities simultaneously

• SIP perspective
• Signaling Student UA, Instructor UA and SIP
  proxy
• Voice communication RTP stack, Audio/speech
  codec library
• System information Database (MySQL)

A conference call
a conference server, full-mesh conference multicas
t cascaded conference application layer multicast
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We use multicast

• Inside firewall and behind a NAT
• Server performance and scalability
• Easy implementation

23
The Classroom VoIP System (3/12)

• 1. Radio (or Frequency) Communication, similar
  to multicast
• Communication amongst ATC and all the pilots in
  his sector ? Multicast
• The flight scenario loaded by the instructor
  defines the communication rules

• SIP perspective
• Every radio channel is given a permanent SIP
  address (sipfreq_120_at_faa.gov)
• Theres no destination for a radio call the
  caller needs to join a multicast session
• Generation and management of multicast address
• Problem each exercise uses the same SIP URI for
  a radio channel, they should not talk to each
  other
• Multicast Address Provider UA (MAP UA)
  providing multicast addresses for different
  exercises
• Define the rules for allowing a student to
  participate in a radio channel communication
• Configurations and roles defined in database (by
  the Instructor)
• Call routing logic routed to MAP UA, or the
  other party in the exercise?
• SIP-CGI

24
The Classroom VoIP System (4/12)
Radio Communication Design
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The Classroom VoIP System (5/12)

• 2. Landline (or Facility) Communication
• Directed communication between ATC-ATC or
  Pilot-ATC? Unicast
• Not really unicast (if the instructor wants to
  monitor this conversation)

• SIP perspective
• Every landline channel is given a permanent SIP
  address (sipfac_aactwr_at_faa.gov)
• Call destination dependents on the caller and the
  called landline
• If (caller Pilot) then (destination ATC)
• If (caller ATC channel 1) then (destination
  the first pilot who picks the call)
• If (caller ATC channel 2) then (destination
  neighboring ATC)
• Generation and management of multicast address
• Communication rules ? Configurations/roles
  defined in the Database
• Logic for processing the communication request ?
  SIP-CGI

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The Classroom VoIP System (6/12)
Landline Communication Design
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The Classroom VoIP System (7/12)

• 3. Instructor Monitoring
• Instructor monitoring to hear an ATC
  communicate during practice/test
• Instructor interjection to give directions to
  the monitored student

• SIP perspective
• The basic insight
• Weve setup every communication in the multicast
  mode
• So, make the instructor join all those sessions
  that has the selected student
• Keep the instructor updated about the status of
  the student
• Ideal case for SIP Subscribe/Notify mechanism
• The SIP flow
• Instructor UA sends a SUBSCRIBE request to
  Student UA
• Student UA sends NOTIFY with multicast addresses
  of all the sessions that it is part of
• Student UA sends NOTIFY to Instructor UA,
  whenever a session is added/removed
• Instructor accordingly joins/unjoins the
  corresponding multicast group

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The Classroom VoIP System (8/12)

• 4. Classroom Recording
• Record all the voice communications pertaining to
  an exercise (i.e. flight scenario)
• Ability to record more than one exercise
  simultaneously
• Options to start, stop and pause the recording
  anytime during the training
• Ability to select and replay the recorded streams
  later

• SIP perspective
• Real time control of record and playback ? RTSP
• Setup and updation of student communication
  status ? SIP Subscribe/Notify
• Storage and retrieval of recorded files ?
  Fileserver
• Playback of recorded streams ? Archive Player

29
The Classroom VoIP System (9/12)
Classroom Recording - SIP/RTSP Design
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The Classroom VoIP System (10/12)

• User Interfaces and I/O Devices
• Student UI
• Buttons for each radio and landline channels
• Audio visual cues to describe the state
  Unselected, Selected, Active or Ringing
• Dynamic creation of the UI based on a
  configuration file

SIGNAL System UI VoIP System UI

• Push-To-Talk (PTT)
• A USB device with a headphone, a microphone and a
  binary switch
• Used as a selector for the voice transmission
  channel
• Reception on radio and landline can be
  simultaneous, but transmission is mutually
  exclusive

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The Classroom VoIP System (11/12)

• User Interfaces and I/O Devices
• Instructor UI
• Create configurations/rules and load/unload
  exercises
• Monitor students and record/replay voice
  communications
• Visual representation of the classroom

SIGNAL System UI
VoIP System UI
32
The Classroom VoIP System (12/12)

• Implementation and Packaging
• Client applications, MAP UA, and SIP CGI
  implementation are in Tcl/Tk
• server implementation and RTP and audio/speech
  library is in C
• Student, instructor machines are Windows and VoIP
  server is Linux
• Freewrap - to package all the Tcl/Tk files into a
  single windows executable
• Installshield - to put the executables,
  configuration files
• Linux RPM - sipd, rtspd, sip-cgi, mapua, MySQL

• Demonstration
• Use-cases
• Instructor loads configuration and students start
  radio communication
• Student simultaneously starts a landline
  communication
• Instructor monitors a student, also does a status
  query

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Discussion Flow

• The Bigger Picture
• A VoIP Primer
• Classroom VoIP system
• Lab VoIP system
• Conclusion

• Classroom vs. Lab
• Communication/Hardware Requirements
• Translation to SIP domain

34
The Lab VoIP System (1/7)

• Classroom vs. Lab
• Simulation of what goes on in the real world (of
  ATCs)
• I/O devices and interfaces are many in number,
  and are quite complex
• There are two types of instructors
• Master Instructor, responsible for the whole
  class
• Position Instructor, responsible for one student
• All the students are no longer identical
• ATCs and Pilots use different devices/interfaces
  and are seated in different rooms
• Communication mechanisms exist between every two
  entities in the lab (well, almost!)

• How does it translate for us?
• Lots of I/O processing and UI design
• Separate user agents for ATC, Pilot, Position
  Instructor
• More SIP flows

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The Lab VoIP System (2/7)

• User Interfaces and I/O Devices
• Four rich graphical interfaces
• Pilots, ATCs, Position Instructors
• Master Instructor (upgrade over the existing
  instructor UI)
• Five I/O devices
• Push -To -Talk, Touch-screens, Foot-pedals,
  Headsets, Speakers

• Communication scenarios
• Four communication scenarios of the classroom
  VoIP system
• Generate notification, if theres a transmission
  on an unselected radio channel
• Complex landline and Inter-position communication
  scenarios
• Few others (made trivial by the extensible design
  of the classroom system)
• Separation of Transmission and Reception on radio
  channels
• Simultaneous monitoring of more than one student
  by the instructor

36
The Lab VoIP System (3/7)
User Interfaces 1. Unified, configurable GUI for
ATC and Position Instructors
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The Lab VoIP System (4/7)
User Interfaces 2. Configurable shared GUI for
Pilots
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The Lab VoIP System (5/7)

• Transmission on an Unselected Radio Channel
• ATC needs a visual cue, if someone is
  transmitting on an unselected channel

• SIP perspective
• Need a mechanism to
• Collect information about transmissions on every
  radio channel
• Manage a list of students, who need to be
  informed for every channel
• Send out notifications to everyone in the list
  for a given channel
• Ideal for SIP Subscribe-Publish-Notify mechanism
• Central management subscribe, publish and notify
  ? Presence server
• Modifications in all the UA/UIs to coordinate
  with the presence server

39
The Lab VoIP System (6/7)
Informing Transmissions On Unselected Channels
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The Lab VoIP System (7/7)

• Landline and Inter-position communications
• Landline communication channels could be
• Ring lines caller dials, phone rings, callee
  picks up ? bidirectional media exchange
• Shout lines caller dials ? transmits the media,
  callee picks up ? bidirectional media exchange
• Override lines caller dials ? bidirectional
  media exchange
• Need for Inter-position communications
• Not all the trainers and trainees are in the same
  room Labs have very limited lighting

• SIP perspective
• All these are to be covered during instructor
  monitoring and recording ? Multicast
• Logic for processing the calls ? SIP-CGI, Call
  handling at UA/UI
• Generation and management of multicast address ?
  MAP UA
• Communication rules ? Configurations/roles
  defined in the Database

41
Discussion Flow

• The Bigger Picture
• A VoIP Primer
• Classroom VoIP system
• Lab VoIP system
• Conclusion

42
Conclusion (1/1)

• Key learning
• Map real-world communication scenarios to
  SIP/RTP/RTSP flows
• Put together SIP components, leading to a VoIP
  architecture
• Importance of an extensible design with
  well-defined interfaces
• VoIP system migration from classrooms to the labs
• Need for robust error/warning handling

• Progress so far
• Classroom VoIP is operational in 5 training rooms
• Lab VoIP prototype deployed by June 07

Thank you!
43
Lets do it

• What should I do?
• Where are the files?
• Which part of the file?
• How?
• Cross your fingers, oops,
• ?k, d?ne,

44
What should I do

• Configuration or logic
• Client side or server side
• address assignment, call routing server
• appearance, user interactions client
• GUI, control, or database
• new buttons, different layout,
• perform different functions
• need to access persistent data

45
Where are the files

• Server side
• sipcgi.tcl SIP CGI implementation
• mapua.tcl providing multicast addresses
• Client side
• look into .wrap file
• GUI
• student_ui.tcl
• instrui_.tcl
• archieve_player.tcl
• Logic
• sipua.tcl
• instructorua.tcl
• rtspc.tcl
• Database
• iids_dbconnect.tcl

46
Which part of the file

• check the API doc of the file
• identify the procedure or add a new procedure
• GUI
• create widget, bind it to an event-handling
  function, implement the function
• Control
• find the function for request/response handling,
  modify the logic
• Database
• find the db function, and use sql command

47
How?

• Learn from the existing code
• e.g., put image create in one place
• Separate GUI code from control code
• create, bind, pack, callback
• little trick tkwait visibility
• AppDebugperror
• use of array, list, ,
• coding convension

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• No usable IDE for Tcl
• Use AppDebugperror and check debug.txt files
• Use tk_messageBox type ok message
• Tks error dialog box
• separate your new code, use tclshand wish to
  run it

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Debuginit . set DebugenableDebug
1 Gui_Monitorinit Gui_Monitormain Load
database

• Enable lower level debug
• E.g., in student_ui.tcl
• sip.dbg file
• Monitor window

Tue Feb 19 41139 PM Eastern Standard Time
2008 Localinit os is Windows Tue Feb 19
41139 PM Eastern Standard Time
2008 a_wintcpip 135.8.6.136,gateway 135.8.6.1
135.148.233.92, gateway 135.8.6.136,domain
usae.avaya.com 135.8.6.136, nameserver
135.8.19.100 135.148.233.92,domain
135.148.233 .92,nameserver
50
?k

• check in your code, put check in notes

51
(No Transcript)