basics of computing -- chapter 4 an introduction to...
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Network Fundamentals The Internet Network Protocols Review
Basics of Computing – Chapter 4An Introduction to Computer Networks
Cory L. Strope
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
Network Fundamentals
The Internet
Network Protocols
Review
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
What is a Computer Network?
A computer network is a collection of computers that are connectedin order to communicate, exchange data, and share resources.
A network can be very large (the Internet) or very small (twocomputers connected at home).
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
Network Classification
Overview
I Size
I Topology
I Communication Models
I Transmission Media
I Recent & Future Trends
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
Network Classification
Network Size
According to geographical size, there are three “sizes” of networks:
LAN (Local Area Network): A network set up within a singlebuilding or campus. Generally, smaller than a few kilometersin size.
MAN (Metropolitan Area Network): A bigger version of a LAN,covering up to the size of a city.
WAN (Wide Area Network): Spans a large geographical area,often the size of a country or a continent.
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
Network Classification
Network Topology
The (physical) topology of a computer network is the pattern inwhich the machines are connected.
I There are 4 patterns of connection:
1. Ring2. Bus3. Star
Each pattern has advantages and disadvantages.I Choosing the correct topology depends on:
I Application of networkI How the network is usedI The communication modelI May depend on the nature of the area where the network is
physically deployed
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
Network Classification
Network TopologyRing
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
Network Classification
Network TopologyBus
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
Network Classification
Network TopologyStar
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
Network Classification
Communication ModelsThere are two models of interprocess communication,communication over the network between different computers.
I Client/server model – the process on the server communicateswith numerous clients
I Print server: A single printer in an office, available to allmachines on the network.
I File server: A high-capacity storage system containing all of anorganizations records.
I Napster
I Peer-to-peer model – two processes communicate as equalsI Instant MessagingI eDonkey, LimeWire, KaZaA
Note that a peer-to-peer network is like Santa Claus, theEaster Bunny, and the Tooth Fairy. It is a peer-to-peer model.
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
Network Classification
Transmission Media
So far, we have classified networks by size, topology, andcommunication model... Another method of classifying networks isthrough the transmission media used.
I When talking of topologies, the assumption was made that wewere using wires to connect computers... “wired networks”,in other words.
I If the medium of communication is the air, the network is saidto be a “wireless network”...
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
Network Classification
Transmission MediaAir
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
Network Classification
Connecting NetworksBridge
A bridge is a device that can be used to couple compatiblenetworks (two buses, for example).
I Does not pass all messages across the connection.
I Forwards message across connection only when the message isdestined for a computer on the other network.
I A switch is a bridge with more than 2 connections.
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
Network Classification
Connecting NetworksRouter
The end result of using bridges and switches is the creation of onelarge, single network.
I Each computer communicates over the system in the samemanner (protocol).
Not all networks have compatible characteristics. In thesenetworks, we build a “network of networks”, known as an internet.
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
Network Classification
Connecting NetworksRouter
To make an internet, a specialized computer must belong to bothnetworks.
I The router forwards messages in one network into othernetworks.
I Routers are complex, and may contain several other devices todo a specific task.
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
Network Classification
Recent and Future Trends in Networking
There is a great deal of research being done on new networkingtechniques:
I Optical Networks: The pro’s of optical networks is hugebandwidth.
I Many networks are desirable for military application:I Sensor Networks: A wireless, and possibly mobile, network
that connects sensors for a specific purpose.I ad hoc Networks: A wireless, self-configuring network of
mobile routers (and associated hosts) connected by wirelesslinks. What would the topology of this be?
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
Network Fundamentals
The Internet
Network Protocols
Review
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
Basics
Asia PacificEurope / Middle East /Central Asia / AfricaNorth AmericaLatin American andCaribbean
Other: White & Cyan
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
Basics
The Internet– With a Capital ‘I’ !
The Internet does not have a specific topology; rather, the Internetcan be viewed as a collection of domains.
A domain is an autonomous system (AS) that is managedlocally.
I The Internet connects a collection of self-managed networks(locally administrated networks).
I For example, UNL campus network (an AS) is connected tothe Internet, but internally, it is managed by the campusnetwork administrators.
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
Basics
Domain EstablishmentICANN – Good Disc. Board Debate Topic!!!
To establish a domain, the entity desiring the domain must registerwith ICANN (Internet Corporation for Assigned Names andNumbers, a non-profit corporation.
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
Internet Addressing
Internet AddressingIP Address
For a computer to be allowed on the Internet, it must have an address.
Internet addresses are called the IP (Internet Protocol) addresses.
I Each IP address is 32 bits long (IPv4).I The next generation IP address is called IPv6, and contains
128 bits.
IP addresses have two main parts:I Network identifier: Used to identify the domain.
I Assigned by ICANN at the time the domain is established.I The registration process ensures the uniqueness of each
domain address.I Machine identifier: Also called the machine (host)
address, this identifies a particular machine within a domain.I Assigned by a network administrator working inside of the
domain.
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
Internet Addressing
IP AddressAn Example
Consider the Computer Science and Engineering department,which is part of the unl domain.
I The machine that hosts the web page of the CS departmenthas the IP address 129.93.165.2:
129.93.︸ ︷︷ ︸Network ID
165.2︸ ︷︷ ︸Mach. Addr.
I You can memorize this number (for a quiz) to access thedepartment web page.
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
Internet Addressing
IP AddressDomain Names
129.93.︸ ︷︷ ︸Network ID
165.2︸ ︷︷ ︸Mach. Addr.
I Or you can simply remember cse.unl.edu. Your choice.
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
Internet Addressing
IP AddressDomain Names
Because IP addresses are hard to memorize, each domain isassigned a unique address known as a domain name.
I The domain name for UNL? unl.edu
Domain names end with a top-level domain (TLD) identifier,e.g. .org, .com, .mil, .net, etc.1
I There are also two-letter TLDs for countries, calledcountry-code TLDs.
I .ca, .eg, .ws, .tv, .us, ...
1Interesting Discussion Board topic: Should there be a .xxx domain? Whywas this proposal turned down?
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
Internet Addressing
IP AddressMachine Name
After assigning a unique domain name, the local administrator isfree to extend it the domain name to include assigned names forindividual machines within its domain.
The Computer Science machine: cse.unl.edu
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
Internet Addressing
Internet ApplicationsEmail & HTTP
The Internet is dominated by two applications:
I Electronic mail (e-mail)2
I Hyper Text Transfer Protocol (HTTP)
Another rapidly expanding use of the Internet is Voice over IP(VoIP), which is simply transmitting telephone data over theInternet rather than the traditional phone lines.
2The word e-mail is outlawed in France. The word is “courrierelectronique”, or “Courriel” for short.
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
World Wide Web
World Wide Web
The terms “Internet” and “World Wide Web” are often usedsynonymously – but there is a difference.
I Internet: Physical world wide network of domains (i.e.networks).
I WWW: Collection of linked documents on the Internet,transferred via HTTP.
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
World Wide Web
World Wide WebURL
Documents on the Internet each have a unique address, called theUniform Resource Locator (URL).
I Contains the information needed by the browser (e.g. InternetExplorer, Mozilla Firefox) to contact the proper server andrequest the desired document.
http://www.cse.unl.edu/join us
Protocol required toaccess thedocument.As a note, https issecure http, used forbank websites, etc.
Name of the host(machine) holdingthe document.
The name of thedocument.Unnameddocuments arereferred to asindex.html.
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
Network Fundamentals
The Internet
Network Protocols
Review
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
What is a Protocol?
In general, the rules that govern the communication betweendifferent components within the computer system are calledprotocols.
A protocol is an agreement between the communicating parties onhow communication should take place.
Rules that govern the communication of computers with eachother are computer network protocols.
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
Internet DeliveryMessages and Packets
Message: The data or information we wish to deliver over theInternet.
I A stream of 1s and 0s
The smallest unit of data that is transferred over the internet iscalled a “packet”. Each packet contains:
I Destination address (the address of the computer that shouldreceive the message).
I Data
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
Internet Software Layers
If the size of the message is larger than the packet size, themessage is divided into multiple packets, all with the samedestination address.
I Each packet is assigned a sequence number
I Packets are sent over the network, may stop at intermediatecomputers before arriving at the destination.
I At destination, packets are collected and concatenated in theiroriginal sequence.
Delivering packets over a network is complex, and is divided amongseveral entities (layers).
I Mail example: You, shipping company, airline.
Each entity (layer) is assigned a task in order to simplify the task.Layers are independent of each other.
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
Internet Software Layers
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
The Network Layer
Each router maintains a list of all other routers in the network,called the routing table.
I Updated frequently to reflect any changes in the topology ofthe network.
I A link going downI Router not accessibleI Discovery of a better path to another router
The network layer uses the IP address as an ID for the router tobuild the routing table.
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
The Link Layer
Also called the physical layer or the data link layer, the task ofthe link layer is to take care of the communication details on thephysical medium.
I Example: In the bus topology, all machines are connected tothe bus... How do the machines determine when they can usethe bus?
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
Layers in Action!
From:
http://ping.unl.edu
http://www.radb.net
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
The Australian National University
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
IP address Machine location Remarks129.93.1.253 Lincoln, NE, USA UNL campus network129.93.3.25 Lincoln, NE, USA UNL campus network129.93.4.237 Lincoln, NE, USA UNL campus network129.93.5.9 Lincoln, NE, USA UNL campus network164.113.234.134 Midwest, USA Great Plains Network, Internet 2164.113.238.149 Midwest, USA Great Plains Network, Internet 2164.113.238.193 Midwest, USA Great Plains Network, Internet 2198.32.8.13 Kansas City, MO, USA Abilene Network, Internet 2198.32.8.49 Denver, CO, USA Abilene Network, Internet 2198.32.171.32 Seattle, WA, USA Abilene Network, Internet 2202.158.194.93 Canberra, Australia AARNet202.158.201.226 Canberra, Australia AARNet202.158.201.234 Canberra, Australia AARNet150.203.99.8 Canberra, Australia
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
Link Layer Protocols
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
Link Layer Protocols
Link Layer Protocol-1Token Ring Protocol
Consider a ring network (LAN): The token ring protocal canmanage the physical transmission of data over the ring network.
I Developed by IBM in 1970, widely used today.
I Transmission in the ring is done in one direction (clockwise orcounter-clockwise)
I When the message reaches its destination, the destinationmachine keeps a copy of it and forwards a copy on around thering.
I When the forwarded copy reaches the origination machine, theoriginating machine removes the message from the ring.
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
Link Layer Protocols
Link Layer Protocol-1Token Ring Protocol
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
Link Layer Protocols
Link Layer Protocol-1Token Ring Protocol
The determination of which machine has the right to send amessage is determined by a unique bit pattern, called the token,which is passed around the ring.
I The machine that has the token has the right to send a singlemessage. Other machines may only forward messages.
I After the machine with the token sends its own message(successfully), the token is passed to the next machine.
I A machine that gets the token, but has no message to send,forwards the token to the next machine.
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
Link Layer Protocols
Link Layer Protocol-2CSMA/CD
The Carrier Sense, Multiple Access with Collision Detection(CSMA/CD) protocol is commonly used on a popular version ofthe bus network, Ethernet.
I Each machine broadcasts the message (all machines “hear”messages)
I Machines keep only the messages that are addressed to itself.
Machines can send messages only when the bus is not being used...What if two send at the same time? Packets collide
I Both machines will detect the collision, and wait for arandom amount of time before retransmitting.
I This process continues until each machine sends its messagesuccessfully.
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
Network classification:I Size
I LANI WANI MAN
I Communication ModelI Client/serverI Peer-to-peer
I Transmission MediumI Copper wire (electricity)I Wireless (radio waves)I Optical fiber (light)
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
Connecting Networks
I Bridges
I Routers
The Internet
I A collection of Domains (autonomous self-managed networks)
I ICANN assigns domains and addressesI Addressing:
I IPv4: 32 bitsI Network IdentifierI Machine Identifier
I Dotted decimal notation
I URL (Universal Resource Locator)I 3 parts: Transmission protocol, machine name, document
name.
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
Network Protocols
I Protocol: A set of rules thta governs communication betweentwo entities.
I Sending data over a network is a complex task, the approachused is a layered approach
I Each layer is responsible for a small part of the overall task.I A layer does not need to know the details of other layers
operation.
I Internet software layersI ApplicationI TransportI NetworkI Link
I Example link layer protocolsI Token RingI CSMA/CD
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks
Network Fundamentals The Internet Network Protocols Review
Questions on Chapter 4?
Cory L. Strope: Basics of Computing – Chapter 4 An Introduction to Computer Networks