Download CS 381 Introduction to computer networks

CS 381
Introduction to computer
networks
Chapter 1 - Lecture 3
2/2/2017
Protocol “layers”
Networks are complex, with many “pieces”:
• Hosts
• Clients/Servers
• Switches
• Layer 2 routing: MAC
• Routers
• Layer 3 routing: IP
• Links
• Copper, fiber, air
• Applications
• HTTP, FTP, SCP
• Protocols
• IP, TCP, UDP
• Hardware
• Software
Introduction
1-2
Protocol “layers”
Question:
Is there any hope of organizing structure of network?
…. or at least our discussion of networks?
Introduction
1-3
Layering of airline functionality
ticket (purchase)
ticket (complain)
ticket
baggage (check)
baggage (claim
baggage
gates (load)
gates (unload)
gate
runway (takeoff)
runway (land)
takeoff/landing
airplane routing
airplane routing
airplane routing
departure
airport
airplane routing
airplane routing
intermediate air-traffic
control centers
arrival
airport
layers: each layer implements a service
• via its own internal-layer actions
• relying on services provided by layer below
Introduction
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Why layering?
Dealing with complex systems:
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Structure allows identification, relationship of complex
system’s pieces
• layered reference model for discussion
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modularization eases maintenance, updating of system
• change of implementation of layer’s service transparent to rest of
system
• e.g., change in gate procedure doesn't affect rest of system
Introduction
1-5
Internet protocol stack
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Application: supporting network applications
• FTP, SMTP, HTTP
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application
Transport: process-process data transfer
• TCP, UDP
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Network: routing of datagrams from source to
destination
• IP, routing protocols
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transport
network
link
Link: data transfer between neighboring network
elements
physical
• Ethernet, 802.11 (WiFi), PPP
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Physical: bits “on the wire”
Introduction
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Internet protocol stack
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Application: layer of the OSI model used by
hosts in a networked environment.
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application
Remote login to hosts: Telnet, SSH
File transfer: FTP, sFTP, tFTP, SCP
E-mail: SMTP
Support for IP/urls and hostnames: DNS
Introduction
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Internet protocol stack
•
Transport: process-process communication
Implemented on hosts connected to the network
core.
• Reliable data transfer
• Congestion control
• Flow control
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application
transport
• TCP, UDP
Introduction
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Internet protocol stack
Network: Host to host communication
• routing of datagrams from source to destination
devices connected to a network
•
• Implemented on hosts and in the network core
• IP, routing protocols
Introduction
application
transport
network
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Internet protocol stack
•
Link: communication between two networked
elements using a single connection
• Ethernet, 802.11 (WiFi), PPP
• Allows for local routing using device MAC
addresses.
application
transport
network
link
Introduction
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Internet protocol stack
• Physical:
bits “on the wire”
• Defines the electrical and physical specifications of
a single link connection.
application
transport
network
link
physical
Introduction
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Encapsulation
source
message
segment
M
Ht
M
datagram Hn Ht
M
frame
M
Hl Hn Ht
application
transport
network
link
physical
link
physical
switch
M
Ht
M
Hn Ht
M
Hl Hn Ht
M
destination
Hn Ht
M
application
transport
network
link
physical
Hl Hn Ht
M
network
link
physical
Hn Ht
M
router
Introduction
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Chapter 1: roadmap
1.1 what is the Internet?
1.2 network edge
 end systems, access networks, links
1.3 network core
 packet switching, circuit switching, network structure
1.4 delay, loss, throughput in networks
1.5 protocol layers, service models
1.7 history
Introduction
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Internet history – Early Innovations
The creation of the Internet is dependent on
mankind’s earlier innovations
• 1836 - Telegraph by Cooke and Wheatstone
• Uses a set of magnetic needles controlled by direction of
current in the telegraph wires.
• Connected Paddington and Slough railroad stations in London.
• Pictured: 5 needle Telegraph. Omits letters C, J, Q, U, X, and Z.
• Later versions reduced the number of needles
• Which reduced the number of wires connecting the telegraphs.
• Reduction in needles/wires resulted in increased coding complexity
Introduction
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Internet history – Early Innovations
• 1858-1866 - Transatlantic cable
• Allowed direct communication (Morse code transmitting at 1 character every 2 minutes)
across the Atlantic.
• This first cable was over 2,200 miles long.
• It failed after one month of use.
• This lead to future cables with better insulation, higher capacity, etc.
• Today, cables connect all continents and are still a main hub of telecommunications.
Introduction
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Internet history – Early Innovations
• 1876 - Telephone by Alexander Graham Bell
• Originally converted sound into electrical signals by using a “liquid transmitter”.
• Needle attached to a battery extended into a cup filled with sulfuric acid
• While setting up the call experiment, Bell spilled the liquid acid on his clothes.
• This led to the first phone call, “Mr. Watson! Come here, I want to see you!”
Introduction
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Internet history – Early Innovations
• 1895- Wireless telegraphy (eventually became “radio”) by Guglielmo Marconi
• Originally developed to transmit Morse code without the use of wires.
• Works based on the principles of generating “Hertzian waves”, or electromagnetic radiation
• Transmission of speech became popular by the 1920s.
Introduction
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Internet history – Political Events
• 1940’s to 1980’s - U.S. vs. Soviet Cold War
• 1957 - U.S.S.R. launches Sputnik
• Transmission of radio pulses.
• Allowed scientists to gather new information about the
atmosphere and ionosphere.
• Transmitted for 21 days, orbited Earth for 3 months.
• The US forms the Advanced Research Projects Agency (ARPA)
within the Department of Defense (DoD) to build US skills in
computer technology.
• The start of global telecommunications. Satellites play an
important role in transmitting all sorts of data today.
Introduction
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Internet history – Political Events
• 1940’s to 1980’s - U.S. vs. Soviet Cold War
• Paul Baran
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Engineer at RAND Corporation (US armed forces think tank founded in the wake of the
second world war)
Strived to develop a means of digital communication that could survive a nuclear war
Communication divided into “packets” and uses a distributed network of nodes (routers)
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•
If one node is destroyed, others would redistribute the communication workload.
Fundamental development of ARPANET, which eventually evolved into the modern Internet
Introduction
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Internet history – Birth of the Internet
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October 29, 1969
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Charley Kline and Len Kleinrock sent the first message to a remote computer.
9pm Kleinrock: “We setup a telephone connection between us (UCLA) and the guys at
Stanford.”
“We typed the L and asked on the phone,”
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“We typed the O, and we asked,”
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“Do you see the L?”
“Yes, we see the L,” came the response
“Do you see the O?”
“Yes, we see the O.”
“Then we typed the G, and the system crashed”
After reboot (1 hour) the second attempt to login to a remote computer was successful.
This was the beginning of the Internet revolution!
And appropriately, the first message sent through the Internet was: L-O-L
Introduction
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Internet history – Birth of the Internet
1971 - Ray Tomlinson of BBN (Bolt, Beranek and Newman)
invents email program to send messages across a distributed
network. The original program was derived from two others:
• an intra-machine email program (SNDMSG) and
• an experimental file transfer program (CPYNET)
• 15 nodes (23 hosts) on ARPANET.
• The first e-mail message??
Qwertyuiop
Introduction
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Internet history – Growth of the Telephone Network
1881: Twisted pair for local connections
• 1885: AT&T formed
• 1892: Automatic telephone switches
• 1903: 3 million telephones in the US
• 1915: First transcontinental telephone cable
• 1927: First transatlantic telephone cable
• 1937: first round-the-world call
• 1946: National numbering plan
• 1958: First use of a modem
• Machine to machine communication
• Analog vs. digital signals
•
Introduction
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Internet history
• 1961: Kleinrock @ MIT: packet-switched network
• 1962: Licklider’s vision of Galactic Network
• 1965: Roberts connects computers over phone line
• 1967: Roberts publishes vision of ARPANET
• 1969: BBN installs first InterfaceMsgProcessor at UCLA
• 1970: Network Control Protocol (NCP)
• 1972: Public demonstration of ARPANET
• 1972: Kahn @ DARPA advocates Open Architecture
• 1972:Vint Cerf @ Stanford writes TCP
Introduction
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Internet history – ARPANET 1969
Introduction
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Internet history – ARPANET 1971
Introduction
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Internet history – ARPANET 1973
Introduction
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Internet history – Growing Pains
Problem: Early networks used incompatible protocols.
Introduction
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Internet history
Robert Kahn’s Ground Rules
1. Each network is independent, cannot be forced to change
2. Best-effort communication (i.e. no guarantees)
3. Routers connect networks
4. No global control
• Principals behind the development of IP
• Led to the Internet as we know it
• Internet is still structured as independent networks
Introduction
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Internet history – The Birth of Routing
Introduction of the Internet Protocol (IP) and Networked Routers
Introduction
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Internet history – 2000
Introduction
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Internet history – 2006
Introduction
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Internet history – 2009
Introduction
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Internet history
• 1974: Cerf and Kahn paper on TCP (IP kept separate)
• 1980: TCP/IP adopted as defense standard
• 1983: ARPANET and MILNET split
• 1983: Global NCP to TCP/IP flag day
• 198x: Internet melts down due to congestion
• 1986:Van Jacobson saves the Internet (BSD TCP)
• 199x: QoS rises and falls, ATM rises and falls
• 1994: NSF backbone dismantled, private backbone
• 200x: The Internet explodes
Introduction
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Internet history - Applications
• 1972: Email
• 1973: Telnet – remote access to computing
• 1982: DNS – “phonebook” of the Internet
• 1985: FTP – remote file access
• 1989: NFS – remote file systems
• 1991: The World Wide Web (WWW) goes public
• 1995: SSH – secure remote shell access
• 1995-1997: Instant messaging (ICQ, AIM)
• 1998: Google
• 1999: Napster, birth of P2P
• 2001: Bittorrent
• 2004: Facebook
• 2005:YouTube
• 2007: The iPhone
Introduction
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Internet history
2005-present
Over 1 billion devices
• Aggressive deployment of broadband access
• Increasing ubiquity of high-speed wireless access
• Emergence of online social networks:
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• Facebook: ~1.8 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)
Introduction
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Internet history
Combination of:
• Telegraph
• Telephone
• Radio
• Licklider’s Intergalactic computer network
• RAND’s guide to Distributed Communication Networks
Introduction
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Introduction: summary
• Communication is fundamental to human nature
• Key concepts have existed for a long time
• Speed/bandwidth
• Latency
• Switching
• Packets vs. circuits
• Key to growth:
• Open networks with simple APIs
• Goal of Internet Protocols:
• To access information as if it were on your local device
Introduction
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Internet Overview
Introduction
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Introduction: summary
Covered a lot of material!
Internet overview
• What’s a protocol?
• network edge, core, access network
• packet-switching versus circuit-switching
• Internet structure
• performance: loss, delay, throughput
• layering, service models
• History
You now have:
• context, overview, “feel” of networking
• more depth, detail to follow!
Introduction
•
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