Collaborating Globally and going via Space too

Collaborating Globally … and going via Space too!

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

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!

E-mail ain’t 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!

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 POP 3 or IMAP. • Mail delivery – Protocol using Mail Transfer Agents to move mail from one place to another.

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!

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.

Next-Gen text chatting • Cellphones • PDAs • Pocket PC • Blackberry devices • You name it! • It’s social!

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.

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 Internet’s standard file transfer process. Comes in secure versions. • NFS: exporting a file system via the Internet.

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!

Whiteboarding

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.

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

Videoconferencing

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.

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!

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

Other collaborations • Tele. Learning: you collaborate with your teachers • Tele. Medicine: you collaborate with your doctor • Tele. Surgery: your doctor collaborates with your internal organs! • Remote control: you control robots, access remote data, and so on.

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 don’t move. • Works just like wireless networking. Convert packets to radio signals.

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.

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!

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 R=B/T. B=R*T. • Most Windows and Apple boxes are set to B=8, 192 bytes = 65, 536 bits = 64 Kb. • Average internet connection, T = 1/8 second. • Max data rate = 512 Kbps! ASDL?

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.

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!

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.