Network and Mobile Compu ng in the 20th Century and Beyond
COMP 1400 Memorial University Winter 2015 What’s the Internet: “nuts and bolts” view
PC • millions of connected computing mobile network server devices: – hosts = end systems wireless global ISP laptop – running network apps smartphone home v communication links network § fiber, copper, radio, regional ISP wireless satellite links § transmission rate: wired bandwidth links
v Packet switches: forward packets router (chunks of data) institutional § routers and switches network
1-2 “Fun” internet appliances
Web-enabled toaster + weather forecaster
IP picture frame http://www.ceiva.com/
Tweet-a-watt: monitor energy use
Slingbox: watch, control cable TV remotely Internet refrigerator Internet phones
1-3 What’s the Internet: “nuts and bolts” view
mobile network • Internet: “network of networks”
– Interconnected ISPs global ISP • protocols control sending, receiving of msgs home – e.g., TCP, IP, HTTP, Skype, 802.11 network regional ISP • Internet standards – RFC: Request for comments – IETF: Internet Engineering Task Force
institutional network
Introduction 1-4 What’s the Internet: a service view
mobile network • Infrastructure that provides services to applications: global ISP – Web, VoIP, email, games, e- commerce, social nets, … home • provides programming network interface to apps regional ISP – hooks that allow sending and receiving app programs to “connect” to Internet – provides service options, analogous to postal service
institutional network
Introduction 1-5 What’s a protocol? human protocols: network protocols: • “what’s the time?” • machines rather than • “I have a question” humans • introductions • all communication activity in Internet governed by … specific msgs sent protocols … specific actions taken protocols define format, order when msgs received, or of msgs sent and received other events among network entities, and actions taken on msg transmission, receipt
1-6 What’s a protocol? a human protocol and a computer network protocol:
Hi TCP connection request Hi TCP connection response Got the time? Get http://www.awl.com/kurose-ross 2:00
Q: other human protocols? 1-7 A closer look at network structure:
• network edge: mobile network – hosts: clients and servers – servers often in data centers global ISP
home v network access networks, physical regional ISP media: wired, wireless communication links
v network core: § interconnected routers § network of networks institutional network
1-8 Packet switching versus circuit switching packet switching allows more users to use network!
example: § 1 Mb/s link ….. N § each user: users • 100 kb/s when “active” 1 Mbps link • active 10% of time
• circuit-switching: – 10 users Q: how did we get value 0.0004? • packet switching: – with 35 users, probability > Q: what happens if > 35 users ? 10 active at same time is less than .0004 *
1-9 Packet Switching: queueing delay, loss
C A R = 100 Mb/s D R = 1.5 Mb/s B queue of packets E waiting for output link
queuing and loss: v If arrival rate (in bits) to link exceeds transmission rate of link for a period of time: § packets will queue, wait to be transmitted on link § packets can be dropped (lost) if memory (buffer) fills up
1-10 Protocol “layers”
Networks are complex, with many “pieces”: – hosts Question: – routers is there any hope of organizing structure of network? – links of various media …. or at least our discussion – applications of networks? – protocols – hardware, software
1-11 Internet protocol stack
• application: supporting network applications – FTP, SMTP, HTTP application
• transport: process-process data transfer transport
– TCP, UDP network • network: routing of datagrams from source to destination link – IP, routing protocols
• link: data transfer between physical neighboring network elements – Ethernet, 802.111 (WiFi), PPP • physical: bits “on the wire”
1-12 source Encapsulation message M application
segment Ht M transport
datagram Hn Ht M network frame Hl Hn Ht M link physical link physical
switch
destination Hn Ht M network H H H M link M application l n t Hn Ht M physical Ht M transport
Hn Ht M network router Hl Hn Ht M link physical
1-13 Web and HTTP
Web has been the most important application on the Internet • web page consists of objects • object can be HTML file, JPEG image, Java applet, audio file,… • web page consists of base HTML-file which includes several referenced objects • each object is addressable by a URL, e.g., www.someschool.edu/someDept/pic.gif host name path name • carried by the HyperText Transfer Protocol
2-14 P2P applications
• no always-on server • arbitrary end systems directly communicate • peers are intermittently connected and change IP addresses examples: – file distribution (BitTorrent) – Streaming (KanKan) – VoIP (Skype)
2-15 Client-server vs. P2P: example client upload rate = u, F/u = 1 hour, us = 10u, dmin ≥ us
3.5 P2P 3 Client-Server 2.5
2
1.5
1
0.5 Minimum Distribution Time
0 0 5 10 15 20 25 30 35 N
2-16 Internet history
1961-1972: Early packet-switching principles
• 1961: Kleinrock - • 1972: queueing theory shows – ARPAnet public demo effectiveness of packet- – NCP (Network Control switching Protocol) first host-host • 1964: Baran - packet- protocol switching in military nets – first e-mail program • 1967: ARPAnet conceived – ARPAnet has 15 nodes by Advanced Research Projects Agency • 1969: first ARPAnet node operational
1-17 Internet history
1972-1980: Internetworking, new and proprietary nets
• 1970: ALOHAnet wireless network in Hawaii Cerf and Kahn’s • 1974: Cerf and Kahn - internetworking principles: architecture for interconnecting – minimalism, autonomy - no networks internal changes required to interconnect networks • 1976: Ethernet at Xerox PARC – best effort service model • late70’s: proprietary – stateless routers architectures: DECnet, SNA, – decentralized control XNA define today’s Internet • late 70’s: switching fixed length architecture packets (ATM precursor) • 1979: ARPAnet has 200 nodes
1-18 Internet history
1980-1990: new protocols, a proliferation of networks
• 1983: deployment of TCP/ • new national networks: IP CSnet, BITnet, NSFnet, • 1982: smtp e-mail Minitel protocol defined • 100,000 hosts connected • 1983: DNS defined for to confederation of name-to-IP-address networks translation • 1985: ftp protocol defined • 1988: TCP congestion control
1-19 Internet history 1990, 2000’s: commercialization, the Web, new apps
• early 1990’s: ARPAnet late 1990’s – 2000’s: decommissioned • 1991: NSF lifts restrictions on • more killer apps: instant commercial use of NSFnet messaging, P2P file sharing (decommissioned, 1995) • network security to • early 1990s: Web – hypertext [Bush 1945, forefront Nelson 1960’s] • est. 50 million host, 100 – HTML, HTTP: Berners-Lee million+ users – 1994: Mosaic, later • backbone links running at Netscape Gbps – late 1990’s: commercialization of the Web
1-20 Internet history 2005-present • Over a billion hosts – More smartphones and tablets • Aggressive deployment of broadband access • Increasing ubiquity of high-speed wireless access • Emergence of online social networks: – Facebook: over one billion users • Service providers (Google, Microsoft) create their own networks – Bypass Internet, providing “instantaneous” access to search, email, etc. • E-commerce, universities, enterprises running their services in “cloud” (eg, Amazon EC2)
1-21
Now and beyond
• Computers in your pocket, on your wrist and face • Machine to machine • Environment monitoring through the crowd • Healthy life styles and medical research • Ubiquitous computing – Ambient intelligence
“The most profound technologies are those that disappear. They weave themselves into the fabric of everyday life un l they are indis nguishable from it.”
Mark Weiser Chief Scien st, Xeros PARC The Computer for the 21st Century Scien fic American September 1991 1-24