Collaborating Globally

1
Collaborating Globally

• and going via Space too!

2
The network is about people

• Want to connect people.
• People exchange information in a wide range of
  ways
• Methods depend on personalities
• Networking technology determines capabilities

3
The first collaborative network tool

• E-mail!
• Simple exchange via a very simple set of
  protocols
• Many different ways of moving e-mail around for
  different kinds of networkin. SMTP used a lot for
  internet.
• Different ways to read mail. From Netscape to
  your phone!

4
E-mail aint so sad

• Modern versions support attachments
• Flexible way of exchanging information
• Delivered asynchronously -- bridges across space
  and time.
• Delivery can work over very old technologies,
  like HF radio, or over the latest space
  communication systems.
• Interplanetary mailboxes!

5
How e-mail works

• Mail client
• Connects to a mail delivery server and delivers
  e-mail, often using Simple Mail Transfer
  Protocol.
• Reads mail from a mailbox server, often using
  POP3 or IMAP.
• Mail delivery
• Protocol using Mail Transfer Agents to move mail
  from one place to another.

6
Text messenging

• Simple version of e-mail concepts
• Often one way, without a mailbox to review on the
  remote server
• Also light, easy to implement
• Great for short communication, emergencies, dates!

7
Text chatting

• Also old! Comes from BITNET and other old
  systems, including HF bulletin boards!
• Based on delivery of messages to a server, and
  then out to one or more users.
• Can be simply peer-to-peer, like ICQ, Messenger,
  Yahoo.
• Can be complex, interserver, like IRC, MUDs, MOOs.

8
Next-Gen text chatting

• Cellphones
• PDAs
• Pocket PC
• Blackberry devices
• You name it!
• Its social!

9
Sharing files - the big need

• If you need to work, you often need to share
  large amounts of content.
• The previous tools often make that a little
  tough, though possible.
• Need to structure anything complex.
• Windows, Apple file sharing is local, unless you
  go VPN.

10
File transfer systems

• The Web! Basically one big file transfer system,
  with a nice front end. Invented for black hole
  physicists!
• File Transfer Protocol the Internets standard
  file transfer process. Comes in secure versions.
• NFS exporting a file system via the Internet.

11
Other file transfer

• CVS - more for sharing text-based content or
  software source code.
• ICQ file transfer - synchronous
• Netmeeting file transfer - ditto
• And so on!
• Napster!

12
Whiteboarding
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Whiteboarding and application sharing

• Highly synchronous forms of communication. Allows
  one to communicate the same way as you would in a
  classroom.
• Also can share programs, build solutions, at the
  same time.
• Not used as much as it could be.

14
Whiteboarding for the world

• Traditionally high-bandwidth, big computers
• PolyLAB has systems that run on handheld
  computers.
• Important for disaster response.
• Great for science work, and problem diagnosis in
  the field.

15
Videoconferencing
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Videoconferencing technology

• Peer to Peer or server based.
• Netmeeting, one to one or many to many (if you
  buy the expensive version). Low resolution.
• Multicast Backbone video transmission based on
  UDP multicasting. High speed, resolution.
  Expensive infrastructure.

17
Telephones, Telephony

• Phone is a pretty good collaborative tool!
• Can now have telephony over IP Netphone,
  dialpad, and so on.
• Can have voice over IP without the telephone bit
  Netmeeting, multicast backbone audio.
• Convergence!

18
Web applications

• Can have Java and other applications on web page
• Can provide chatting services, file sharing
• Forms/Java/Javascript can provide interactive
  access to database systems.
• Increasingly interactive.

19
Other collaborations

• TeleLearning you collaborate with your teachers
• TeleMedicine you collaborate with your doctor
• TeleSurgery your doctor collaborates with your
  internal organs!
• Remote control you control robots, access remote
  data, and so on.

20
Space!!!!!!!!!!

• Communicate via a spacecraft, from one point on
  Earth to another.
• Can have spacecraft in low Earth orbit. Needs
  LOTS of them, and they move in the sky.
• Can have spacecraft in geosynchronous Earth
  orbit Only need a few, and they dont move.
• Works just like wireless networking. Convert
  packets to radio signals.

21
Space networking

• Can send normal telephone signals over the
  satellite link.
• Can use TDMA-type systems to put phone and data,
  and other services over the satellite link.
• Can use equipment to send ATM and IP networking
  directly over the link.
• Can message across the link.

22
The problems with TCP/IP

• TCP/IP waits for signals to come back to decide
  if packets are being lost.
• Waits a certain amount of time - time designed
  for standard networks.
• Assumes any problems with lost packets are due to
  congestion (too many packets), and slows down!

23
Bandwidth-delay product problem

• If a computer stores B bits, and has to wait T
  seconds to hear back, it can only transmit B bits
  every T seconds, so max data rate is RB/T.
  BRT.
• Most Windows and Apple boxes are set to B8,192
  bytes 65,536 bits 64 Kb.
• Average internet connection, T 1/8 second.
• Max data rate 512 Kbps! ASDL?

24
Going geosynchronous

• Round trip time from geosynchronous Earth orbit
  (GEO) is T 1/2 second.
• Max data rate, per connection, on normal computer
  128 Kbps!
• Independent of how fast the connection is (can be
  10 Mbps).
• Only a property of TCP/IP.

25
Solutions

• Not use TCP/IP -- UDP for video is used a lot,
  even on the Internet.
• Advanced space protocols being discussed.
• Can retune the computer -- edit the registry on
  Windows
• Change B
• Change other parameters to keep data rate up.
• Changes need to be on both ends!

26
Issues

• Need bigger computers to have larger buffers
• Need somebody to retune machines. Who does it in
  remote communities?
• Retuning reduces performance of local networks.
• Different bandwidth needs different buffer sizes.
  Needs an expert.