A Supplement to Lecture 12 Circuit Switched …...computer networks connecting hundreds of millions...
Transcript of A Supplement to Lecture 12 Circuit Switched …...computer networks connecting hundreds of millions...
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Circuit Switched Networks vs. Packet-Switched NetworkThe Internet Emerges
https://www.photonics.com/Articles/Toward_Optical_Packet_Switching/a24582
A Supplement to Lecture 12
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What is the Internet?
• The Internet is a worldwide system of interconnected autonomous computer networks connecting hundreds of millions of digital “computing devices” together.
– “Computing devices” means desktop personal computers, workstations, servers, laptops, cell phones, VoIP phones, game consoles, IP-TV, GPS-enabled devices, environmental sensor devices, and home and office electrical and security systems.
– “Computing devices” connected to the Internet are sometimes called “hosts” or “end devices” or even “end systems.”
• The Internet is a vast network of packet-switched networks consisting of millions of private and public, academic, business, NGO and government networks of local to global scope.
http://deresinc.com/HomeNetworks.aspx
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https://dazeinfo.com/2016/06/13/number-internet-users-worldwide-2016-2020/
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Circuit-Switched Network
TelephoneSwitch
TelephoneSwitch
TelephoneSwitch
TelephoneSwitch
TelephoneSwitch
TelephoneSwitch
TelephoneSwitch
Many paths are possible, but only one is selected per
call.
Once a connection is established, this
connection is maintained until call
is terminated.
Caller
= Dedicated connection (point-to-point)
Subscriber lines(or local loops)
Trunks(links between
Exchanges)
Central Office
Central Office
Central Office
PSTN = public switched telephone network
Full Duplex
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Packet Switched Network
Internet
Many paths possible for a single message as packets are routed to
the destination.
Packets are routed according to the best path available at the
time.
Receiver(destination)
Sender(source)
Message broken into packets andeach addressed
Packets sequentiallyreassembled
to revealmessage
= Packet
Routeror Switch
(Data Packet or “Datagram”)
Large array of routers and data links.
Packet route
From: D. B. Estreich, Lecture from ES 101A in 2014
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Network Organization
Centralized Network Decentralized Network
(e.g., PSTN)
Distributed Network
(e.g., Internet)
In 1962, Paul Baran (RAND Corp.) envisioned a network of unmanned nodes using intelligent switches to route data node to node to their final destinations. Baran called this "hot-potato routing" or distributed communications. This was implemented in ARPANET which became the Internet.
Concept of hardened networks to deal with disasters.
A networkof routers
A highly vulnerablenetwork
7After Kurose & Ross, Computer Networking, 5th Edition, Addison-Wesley, New York, 2010.
National & Global ISPs
Local orRegional
ISP
MobileCellular
NetworkWireless
HomeNetwork
Corporate orUniversityNetwork
HomeNetwork
Example:
sonic.net
Example:
Keysight Technologies
Example:
Verizon
Example:
Sprint
ModemPacket Switch or Router
WirelessRouter
Cell Phone
Cellular
Base Station
VoIP Phone
Host
Mobile Laptop Server
Key:
A “representative” section of the Internet:
(ISP = Internet Service Provider)
Internet is a “Network of Networks”
8http://dafi1637.blogspot.com/2017/10/google-fiber-usa-map.html
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Brief History of the Internet – I
Year Event
1958 ARPA (Advanced Research Program Agency) is established by the U. S. Defense Department in response to the 1957 Sputnik launch.
1969 The ARPANET utilizes “packet switching” technology developed in part by Paul Baran of the RAND Corporation. The first four nodes in the network were UCLA, UCSB, Stanford and the Univ. of Utah.
1972-4 ARPANET expands to 15 nodes and standardization includes the TCP (Transmission Control Protocol) developed by Vinton Cerf of Stanford, thereby creating the TCP/IP network standard now used today.
https://www.internetsociety.org/internet/history-internet/brief-history-internet/
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Xerox PARC (and its Alto Computer in April 1973)
http://www.computerhistory.org/revolution/input-output/14/347
First workstation (personal computer)
Pulled together all the elements used inthe graphical user interface (GUI)
Features:(1) Bit-mapped display(2) Three-button mouse (D. Engelbart – SRI)(3) Use of graphical windows(4) Ethernet LAN (Robert Metcalf)(5) And more
Footnote: The IBM PC was introduced in 1981.
AltoComputer
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Beginning of the Internet Age
On August 27, 1976, scientists from SRI International celebrated the successful completion of tests by sending an electronic message from a computer set up at a picnictable behind the Alpine Inn. The message was sent via a radio network to SRI and on throughthe ARPANET to Boston. This event marked the beginning of the Internet Age.
Alpine Inn Beer Garden (Portola Valley)
Established 1852
California Historic Site
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Brief History of the Internet – II
Year Event
1990 The Internet goes private with a number of ISPs (Internet Service Providers) being created by businesses (most notably AOL – America Online).
1991 Tim Berners-Lee at CERN creates the World Wide Web (WWW), which uses Hypertext Markup Language (html), Hypertext Transport Protocol (http) and URLs (Uniform Resource Locator).
1993 First Web browser (MOSAIC) at the University of Illinois – soon becomes Netscape Navigator; later in 1995 Microsoft enters the market with Internet Explorer.
https://www.internetsociety.org/internet/history-internet/brief-history-internet/
How TCP/IP Works
STEP 1TCP protocolbreaks data intopackets andaddresses them.
STEP 2The packets travel fromrouter to router over the Internet according to IP protocol.
STEP 3TCP protocolreassembles thepackets into theoriginal whole.
To:From:
To:From:
router
routerrouter
router
router
router
SenderReceiver
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https://www.researchgate.net/figure/Classification-of-header-fields-in-the-IP-and-UDP-header_fig1_241622622
IP and UDP Headers
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https://www.w3.org/People/Frystyk/thesis/TcpIp.html
Reliable Packet Transmission (TCP Packets)
Lost Packet
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Feature Circuit Switching Packet Switching
Dedicated Path Yes
No
Path FormationPath dedicated for one conversation
Route is established on a per packet basis of the conversation using datagram (or per conversation with virtual circuit)
Delay Call setup delay Packet transmission delay (call setup delay for virtual circuit)
Bandwidth Type Fixed Bandwidth Dynamic bandwidth
Overload EffectsStops call establishment
Increases packet delay (can block call establishment and increase packet delay with virtual circuit)
Comparing Packet Switching to Circuit Switching
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Packet-Switched Network Operation
• Adaptive routing – routers chose the best path by examining traffic loading along available paths. Routers create a “routing table” for the packet travel.
• All users share the same network resources.
• Packet-switching is more efficient than circuit-switching in networks when data is bursty (i.e., variable delays interspersed with periods of data transmission). More “efficient” means a better utilization of the network resources.
This is an example of
“bursty” data
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An Internet Packet and its Headers
• In IPv4, each packet is restricted to 1,500 bytes of data (i.e., payload + headers)
• Each packet consists of the application data and headers
• The headers contain control and routing information such as:
– Source IP address and destination IP address
– Packet numbering for reconstruction at destination
• Every computer on the Internet has the TCP/IP program. The client/server model is used on the Internet.
• TCP (Transmission Control Protocol) puts the data or message into packets at the source and reassembles the data or message at the destination
• IP (Internet Protocol) does the packet addressing for the routing over the Internet
Application DataIP header TCP/UDP header
Internet Packet
The rules that govern communication – any form – are called “protocols.”
19https://computer.howstuffworks.com/question5251.htm
Internet Packets Have Header, Payload and Trailer
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Layer Pictorial View of Protocol Data Unit Entity
ApplicationData or
Message
Transport Segments
Internet or Network
Packets orDatagrams
Network Access
Frames
Data
DataTransport
Header
DataTransport
HeaderNetwork Header
DataTransport
HeaderNetwork Header
Frame Header
Frame Trailer
Protocol
SMTPHTTP, DNS
TCPUDP
IP
EthernetModem
FDDI
Number of segments 1
Bits transmitted over channel medium
TCP/IP Protocol Architecture Model
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TCP versus UDP Transmission
TCP is “reliable” because it has flow & congestioncontrol, retransmission, &uses acknowledgements.
UDP does not use these because it is focused onlyupon sending packets. ItIs “best effort delivery.”
UDP
TCP and UDP Analogies:
Post OfficeVerifies deliveryRegistered
Letter
TCP
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Example of an IP Address (i.e., IPv4 format)
• Every Internet node must have an Internet address (some are “permanent” and others are “temporary”)
• When you connect to the Internet over a broadband access, an IP address is assigned to your computer by your Internet Service Provider (ISP)
• This IP address is “dynamic” – when you disconnect the network can allocate it to another user.
1 byte 1 byte
4 bytes = 32 bits in total
1 byte 1 byte
Decimal:
Binary:
EXAMPLE:
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IPv4 versus IPv6
How do you say 340,282,366,920,938,463,463,374,607,431,768,211,456?
It is 340 undecillion, 282 decillion, 366 nonillion, 920 octillion, 938
septillion, 463 sextillion, 463 quadrillion, 607 trillion, 431 billion,
768 million, 211 thousand, 456.
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▪ Uses computer-based technologies
▪ Highly interconnected but distributed in practice
▪ Networks interconnected thru gateways and access points (i.e., routers, link-layer switches, etc.)
▪ Each network stands on its own (TCP/IP protocols do not dictate internal changes to networks)
▪ TCP/IP is independent of the data type or the transport medium
▪ TCP/IP protocols are not proprietary (all can freely use it)
▪ Effectively little regulation applies to Internet (in fact, users of the Internet generally oppose regulation)
▪ There is NO direct global control of the Internet
Internet Attributes
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Computer History Museum (Mountain View, CA)
Open Wednesday through Sunday,1401 Shoreline Blvd (adjacent 101) in Mountain View, CA. 650-810-1010
After the coronavirus “shelter-in-place” ends, a great place to visit.
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Questions
https://www.colourbox.com/image/internet-concept-on-white-background-image-5798412