Computer Net Interoperability
Computer Net Interoperability CECS 474
Popular in Course
Popular in Computer Science and Engineering
This 33 page Class Notes was uploaded by Zackary Cronin on Monday October 5, 2015. The Class Notes belongs to CECS 474 at California State University - Long Beach taught by Tracy Maples in Fall. Since its upload, it has received 26 views. For similar materials see /class/218744/cecs-474-california-state-university-long-beach in Computer Science and Engineering at California State University - Long Beach.
Reviews for Computer Net Interoperability
Report this Material
What is Karma?
Karma is the currency of StudySoup.
Date Created: 10/05/15
CECS 474 Computer Network Interoperability Performance Issues Supplement Performance Networks need high performance or high performance per unit cost The old computer adage Get it right and then make it fast may not apply Networks must be designed at the outset for speed Bandwidth Defn Network bandwidth is the measure of the capacity of a transmission system Bandwidth is measured in Hertz Defn Network throughput is the number of bits that can be transmitted in a certain amount of time Example 10 million bitssec Mbps gt 01 u sec to transmit each bit Dr Tracy Bradley Maples Spring 2009 Bandwidth Cont d You can think of each bit on a network as being a pulse of some width 1 second 1 second The more sophisticated the transmissionreceiving technology the narrrower each bit can become Other factors eg software affect the throughput as well Bandwidth vs Throughput vs Effective Throughput Throughput bulk number of bitssec on a channel Effective Throughput or Goodput measured performance of a channel in bitssec as seen by an application Throughput gt Effective Throughput For applications we speak of the bandwidth requirements of an application Dr Tracy Bradley Maples Spring 2009 Latency Latency or delay is the amount of time is takes for a single bit to propagate from one end of a network to another Latency is measured in terms of time RTT round trip time There are three components that form the latency 1 Speedoflight propagation delay 0 in a vacuum 30 108 meterssec o in a cable 23 108 meterssec o in fiber 20 108 meterssec 2 Amount of time it takes to transmit a unit of data This value is a function of the network bandwidth and packet size 3 Queueing and processing delays in the network Dr Tracy Bradley Maples Spring 2009 Latency cont d Latency Propagation Transmit Queue Propagation DistanceSpeedof light Transmit SizeThroughput Where Distance length of the Wire over which the data will travel Speedof light effective speed of light over the channel 0 Size size of the packet o Throughput bitsunit time at which the packet is transmitted You cannae change the laws of physics Mr Scott Star Trek Latency is limited by the speed of light Example 24 ms latency 3000 mile propagation delay in ber approximate Width of the United States Dr Tracy Bradley Maples Spring 2009 Recall Switched Networks Two types of switched networks 1 J Circuitswitched networks provide service by setting up a total path of connected links from the origin to the destination host A control message is first sent to setup a path from the origin to the destination A return signal informs the origin that data transmission may proceed Once data transmission starts all channels in the path are used simultaneously and the entire path remains allocated to the transmission whether or not it is in use Packetswitched networks decompose messages into small pieces called packets These packets are each numbered and make their way through the net in a storeandforward fashion Links are considered busy only when they are currently transmitting packets Dr Tracy Bradley Maples Spring 2009 Switching performance issues Header overhead ie the amount of quotextraquot information that must be sent along with the data to ensure proper transmission For large amounts of data circuit switching lt packet switching Transmission delay ie the amount of time it takes data from the time it enters the network until it arrives at its39 destination For short and bursty messages packet switching has the lowest delay For long continuous streams of data circuit switching has the lowest delay Dr Tracy Bradley Maples Spring 2009 Time Circuit Switching Dr Tracy Bradley Maples Spring 2009 Time Packet Switching CECS 474 Computer Network Interoperability Network Interconnection Devices Repeaters Hubs Bridges Switches and Routers Repeaters and Hubs A repeater is a network interconnection device that regenerates signals coming in one link onto another 0 Repeaters use no logic in regenerating signals so data and noise are both sent through the repeater o Repeaters can be used to extend the range ofa single LAN A hub is a network interconnection deVice that accepts an input signal from an incoming port and copies it onto all of its output ports Dr Tmcy Bradley Maples Spring 2009 Physically hubs are 0 Small electronic devices 0 Have connections for several computers eg 4 or 20 Logically hubs o Operate only on signals 0 Propagate each incoming signal to all connections 0 Are similar to connecting segments with repeaters 0 Do not understand packets so it cannot filter them Hubs have extremely low cost Dr Tracy Bradley Maples Spring 2009 Bridges and Switches A frame is a packet of data passed across the network at Layer 2 of the network protocol stack 0 At Layer 2 of the protocol stack media access control MAC addresses are used to send messages from one computer to another 0 MAC addresses are also known as physical addresses or hardware addresses 0 MAC addresses are not the same an IP addresses IP addresses are software addresses that can be changed MAC addresses are hardware addresses associated with the network interface card MC and cannot be changed 0 Frames have two MAC addresses in their header 1 the MAC address of the source computer and 2 the MAC address of the destination computer Des SoumFere Preamble Address AddmssType DaalnFrame cnc an F7 mm 47 Huang l The Ethernet ame format Dr Tracy Bradley Maples spnng zone A bridge sometimes called a tranqmrent bridges is a network in erconnection device that forwards data frames coming in from one connection to the outgoing link that corresponds to the MAC destination address in the frame A bridge 0 Is a hardware device 0 Connects two LAN segments 0 Forwards frames 0 Does not forward noise or collisions from the incoming connection 0 T inter name ua eu on L 4 A bridge is used to connect two localarea networks LANs or two segments of the same LAN that are the same type A network with a bridge Dr Tracy Bradley Maples spnng znna A switch is a network interconnection device that accepts a frame from an incoming port and forwards the frames to the outgoing link that corresponds to the MAC destination address in the frame A switch o Is physically similar to a hub o Is logically similar to a bridge 0 It operates on frames 0 It understands MAC addresses 0 It only forwards frames when necessary 0 Permits separate pairs of computers to communicate at the same time 0 Has higher cost than a hub o Switches can be used in heavily loaded networks to isolate data ow and improve performance 0 Switch prices are dropping so that there is very little difference from hub prices Dr Tracy Bradley Maples Spring 2009 An IP datagram is a packet of data passed across the network at Layer 3 and above of the network protocol stack 0 At Layer 3 and above of the protocol stack IP addresses are used to send messages from one computer to another 0 IP addresses are software addresses that can be changed according to the network subnet they are attached to 0 IP datagrams have two IP addresses in their header 1 the IP address of the source computer and 2 the IP address of the destination computer Dr Tracy Bradley Maples Spring 2009 A router is a network interconnection device that accepts an 11 agramfr 39 mi an ormrds the datagnain to the 0 oin co ng port df utgoing link that corresponds to the n destination addiess in the frame Di TracyEmdlsyMaplesSpnng mug A router o Forwards data depending on IP addresses not Hardware MAC addresses 0 Isolates each LAN into a separate subnet with separate IP addresses 0 Needs to be set up before they are used Once set up they can communicate with other routers and learn the way to parts of a network that are added after a router is initially configured Dr Tracy Bradley Maples Spring 2009 p x CECS 474 Computer Network Interoperability Wireless 80211 Supplement Wireless 80211 The most popular wireless LAN technology is the IEEE 80211 standard Physical Properties 80211 was designed to run over three different types of physical media 1 Spread spectrum using frequency hopping 2 Spread spectrum using direct sequence 3 Infrared signals Spread spectrum spreads the signal over a wider frequency band than normal so that interference from other devices will not have as great an impact Frequency Hopping The signal is transmitted over an apparently random sequence of frequencies first one then a second then a third etc The sequence of frequencies is computed algorithmically using a pseudorandom number generator The sender and the receiver use the same seed value to calculate synchronized frequencies 80211 defines a physical layer standard that uses frequency hoping over 79 lMhzwide frequency bandwidths It runs in the 24 Ghz frequency band of the elecromagnetic spectrum Dr Tracy Bradley Maples Spring 2009 2 Direct Sequence Each bit in the frame is represented by multiple bits in the transmitted signal The sender sends the XOR of the bit it wants to send and n random bits This is known as an nbit chipping code The sender and receiver random number streams match This spreads the signal across a frequency band that is n times wider than is required 1 01 1 1 1 1 Dam stream 1010 17 11 L17 0 Random sequence 010010110101 1001 1 17 0 XOR of the two 1011101110101001 FIGURE 1 Example 4bit chipping sequence 80211 de nes a physical layer standard that uses direct sequence using an llbit chipping sequence It runs in the 24 Ghz frequency band of the elecromagnetic spectrum 3 Infrared Signals The third physical layer standard for 80211 uses infrared signals that are diffused the sender and receiver do not have to be aimed at each other This technology works for about 10 m inside buildings only 80211 MAC Protocol Collision Avoidance 802 11 uses a modified Ethernet protocol Two problems arise which make the Ethernet modifications necessary 0 The hidden node problem A cannot see D in Figure 2 Using the standard Ethernet protocol the hidden node problem will result in collisions that the sender cannot recognise Dr Tracy Bradley Maples Spring 2009 0 The exposed node problem B can send to A simultaneously with C sending to D Using the standard Ethernet protocol these simultaneous transmissions would not be allowed and we want them 6 FIGURE 2 Example Wireless Network with operating in an ad hoc Dr Tracy Bradley Maples Spring 2009 Multiple Access with Collision Avoidance MACA 80211 uses CA to solve these two problems The sender and receiver exchange control frames before the sender actually transmits data so that all nearby nodes know that transmission is about to begin Sender sends a request to send RT S frame to the receiver The frame includes the length of time the sender needs to transmit its data frame or hold the medium Receiver replies with a clear to send C T S frame that echoes the length field back to the sender and anyone else who receives it If a node sees the CTS frame it must not transmit during the time interval indicated in the length field solving the hidden node problem If a node sees the RTS frame but not the CTS frame it is free to transmit solving the exposed node problem The receiver sends an ACK to the sender after successfully receiving a frame All nodes wait for this ACK before trying to transmit If two senders transmit RTS frames at the same time a collision happens Collisions cannot be detected but because the RTS frames are destroyed no CTS frames are ever sent The sender s timeout while awaiting the CTS frames and must retransmit Dr Tracy Bradley Maples Spring 2009 Ad hoc vs Infrastructure Modes In ad hoc mode all nodes communicate directly with each other In infrastructure mode nodes communicate Via an access point AP Distribution system FIGURE 3 Access points connected to a distribution network Access points are connected to a wired network infrastructure Access points are connected to each by a distribution system The distribution system runs at layer 2 of the ISO architecture Dr Tracy Bradley Maples Spring 2009 Scanning Nodes can roam from cell to cell selecting the access point they need to use Active scanning occurs when the node sends probe frames searching for an access point Passive scanning occurs when the access point sends out a beacon periodically to advertise its presence Distribution system FIGURE 4 Node Mobility Dr Tracy Bradley Maples Spring 2009 80211 Frame Format 16 16 48 48 48 16 48 0 18496 32 Control Addr1 Addr2 39 Addr3 Sethrl W CRC FIGURE 5 80211 frame format Duration 0 Source Addr 48 bits 0 Destination Addr 48 bits 0 Data up to 2312 bytes 0 32bit CRC 0 Addr3 48 bits described below 0 Addr4 48 bits described below Not shown three subfields o 6bit Type Field that speci es whether the frame carries data RTS CTS or is being used by ToDS or FromDS o 1bit eld called ToDS o 1bit eld called FromDS DS Field Examples 0 If T 0DS0 and FromDS0 the node is being sent directly from the source to the destination Addrltarget node Addr2source node 0 If T0DS1 and FromDS1 the node is being sent through the distribution system DS Addrlultimate destination Addr2immediate sender Addr3intermediate destination Addr4original source Dr Tracy Bradley Maples Spring 2009 Female Inventors Hedy Lamarr u quotAny girl can be glamorousquot Hedy Lamarr once said quotAll she has to do is stand still and look stupidquot The lm star belied her own apothegrn by hiding a brilliant inventive mind beneath her photogenic exterior In 1942 at the height of her Hollywood career she patented a frequency switching system for torpedo guidance that was two decades ahead of its time Hedy Lamarr was born in Vienna in 1914 as Hedwig Eva Maria Kiesler She went to Max Reinhardt s famous acting school in Berlin during her late teens and in 1933 she showed the world her acting skills and most of herself in the lm Extase Ecstacy which quickly became notorious for its extensive nude scenes The movie played in America after severe cutting and in 1937 its leading lady went to Hollywood Louis B Mayer of MGM hired her and gave her the name Lamarr Some people thought Hedy to be the most beautiful woman in Hollywood but as an actress she was overshadowed by heroines like Ingrid Bergman and Katharine Hepburn In 1966 she published her autobiography Ecstacy and Me Hedy Lamarr married Fritz Mandal the first of six husbands in 1933 During their marriage which broke up in 1937 Madame Mandl was an institution in Viennese society entertainingiand dazzlingiforeign leaders including Hitler and Mussolini Her husband specialized in shells and grenades but from the midthirties on he also manufactured military aircraft He was interested in control systems and conducted research in the field His wife clearly learned things from him because she and her co inventor George Antheil later went on to invent the torpedo guidance system that was two decades before its time Hedy Lamarr s coinventor George Antheil was born in Trenton New Jersey in 1900 His parents were from East Prussia After studying music at what is now the Curtis Institute in Philadelphia he went to Europe to pursue a career as a concert pianist heading first to Berlin and then settling in Paris in 1923 He became one of the top avantegarde composers of the time writing and playing machinelike quotmechanisticquot rhythmically propulsive pieces with names like Airplane Sonata Sonata Sauvage Jazz Sonata and Death of Machines His Ballet Meanique was scored for sixteen player pianos xylophones and percussion and was first performed in Paris in June 1926 in a version that had only one player piano but also had electric bells airplane propellers and a siren It caused an uproar Antheil knew practically everybody in Paris39s literary artistic and musical circles but in 1933 he returned permanently to the United States He became a lm composer in Hollywood and a writer for Esquire magazine producing a syndicated advicetothe lovelom column and articles about romance and endocrinology He even published a book titled Every Man H is Own Detective A Study of Glandular Endocrinology In 1939 he set an article to Esquire about the future of Europe that proved impressively accurate It predicted that the war would start with Germany invading Poland that Germany would later attack Russia and then the United States would be drawn into the con ict He met Hedy Lamar in the summer of 1940 when they were neighbors in Hollywood and she approached him witha question about glands She wanted to know how she could enlarge her breasts In time the conversation came around to weapons and Lamarr told Antheil that she was contemplating quitting MGM and moving to Washington DC to offer her services to the newly established National Inventors Council They began talking about radio control for torpedoes The idea itself was not new but her concept of quotfrequency hoppingquot was Lamarr brought up the idea of radio control Antheil39s contribution was to suggest the device by which synchronization could be achieved He proposed that rapid changes in radio frequencies could be coordinated the way he had coordinated the sixteen synchronized player pianos in his Ballet Meanique The analogy was complete in his mind By the time the two applied for a patent on a quotSecret Communication Systemquot on June 10 1941 the invention used slotted paper rolls similar to playerpiano rolls to synchronize the frequency changes in transmitter and receiver and it even called for exactly eightyeight frequencies the number of keys on a prano Lamarr and Antheil worked on the idea for several months and then in December 1940 sent a description of it to the National Inventors Council which had been launched with much fanfare earlier in the year as a gatherer of novel ideas and inventions from the general public Its chairman was Charles F Kettering the research director of General Motors Over its lifetime which lasted until 1974 the council collected more than 625000 suggestions few of which ever reached the patent stage But according to Antheil Kettering himself suggested that he and Lamarr develop their idea to the point of being patentable With the help of an electrical engineering professor from the California Institute of Technology they ironed out its bugs and the patent was granted on August 11 1942 It specified that a highaltitude observiation plane could steer the torpedo from above s mm mm H mm mm m mm mm pages m drawmgs hum Lamarr and Anma s D tmt th2 me wave an me sacund sheet Marke sthe name m Hed Lenerrs seeend m 5M 1 men n Kenenng Expressed ulhers was skepuml One Exarmna39 at me Invemurs Cuunnl rk Hedy Laman mmnwhde dennnsud39ed hEr luyalty by msmg seven mlllmn dullars m a single evemng semng War bunds Dewe An39hed s lubbymg me Navylumedns back an themvmuun cundudmg Lhanhe mechamm vmuld have bean mu bulky m m mm a lurpedu AnLhEIl degeed he insisted de sman ennugn m squeeze m swatch And nemnugmne knewwny Was Sn negzuve In Uur patem He y an Iattanpted m Elena etumda39e Bur gen enen m Was ngmn Whu emned uur mvenunn rad nu further man me vmrds nlayer planu My gud I an see men saying We shall puts plays planu ma turpedn In other words it was a culture clash the thickheaded brass hats were incapable of considering the idea that musical technology could play any part in a complicated piece of weaponry But Antheil s explanation is too simple the invention had other problems Describing them requires looking at other developments in torpedo control at the time especially in Germany In the United States Hedy Lamarr and George Antheil shunned by the Navy no longer pursued their invention But in 1957 the concept was taken up by engineers at the Sylvania Electronic Systems Division in Buffalo New York Their arrangement using of course electronics rather than piano rolls ultimately became a basic tool for secure military communications It was installed on ships sent to blockade Cuba in 1962 about three years after the LamarrAntheil patent had expired Subsequent patents in frequency changing which are generally unrelated to torpedo control have referred to the Lamarr Antheil patent as the basis of the field and the concept lies behind the principal anti jamming device used today for example in the US government39s Milstar defense communication satellite system Information Source American Heritage of Invention amp Technology Spring 1997 Volume 12Number 4 Female Inventors www1nventionsorg W e take your pri vacy seriously Please read our Privacy Statement Copyright 1999 2005 Inventors Assistance League Creating an Unsheilded Twisted Pair UTP Cable for Ethernet Using RJ 45 Connectors The following guidelines are used to connect a 4pair that is eight individual wire Unsheilded TwistedPair UTP copper cable to an RJ45 connector This gure shows the typical arrangement of Wires and follows the Electronic Industry AssociationTelecommunications Industry Association39s BIATIA Standard 568B StraightThrough Cables A straightthrough cable has the wiring shown in Figure 46 at both ends of the cable ie pins 18 n one end of the cable correspond to pins 18 on the other end of the cable Straight tl1rough cables are used to connect two devices of differing types For example straightthrough cables connect p t t quot 1 p t t p t 1 I 1 and t d Twisted pair cable Pair 3 Pair 1 Pair 2 Palr 4 mm whxlc whxlc whur mange orange green blue blue green brown brown M H h h I I RJ45 connector a V a a 9 Figure 46 Twisted pair cable connected to an RJ45 connector Type B Ordering In a straightthrough cable both ends are Type B Dr Tracy Bradley Maples Proper insertion of wires into an RJr45 jack CrossOver Cables In crossover cables one end has the has Figure 46 and the other end changes the orange and green pairs Crossover cables are used to connect two devices of the same type For example crossover cables connect p t t p t quot h t quot 1 and d The amngernent of wires for cross over cables is as follows Smndan l End Crnssnvez End Pm l WhltdOrange Fin 1 WhlteGreen Pm 2 Orange Fin 2 Green Pm 3 wlnlecreen Fin 3 WilmaOrange Pm 4 Blue Fin 4 Blue Pm s WhltejBlue Fin 5 WhlteBlue Pm a Green Pin 5 Orange Pm 7 WhlteJBmwn Fin 7 WhiteBrown Pm a Brown Pin a Brnwn Type A Ordering In crossover cable one end is Type B and one end is Type A REFERENC ES 1 Figure 46 Handern Networking Fundamentals Michael Palmer Thomson 2006 2 Other lgur s from Wiring Tutorial for IOBaseT Unshielded Twisted Pair UTP URL httpwwwnetspeccomhelpdeskwiredochtrn Dr Tracy BradleyMaples CECS 474 Computer Network Interoperability INTRODUCTION May you live in interesting times Chinese Blessing or Curse The Industrial Revolution c 1760 The change in social and economic organization resulting from the replacement of hand tools by machine and power tools and the development of largescale industrial production The Digital Revolution c 1990 The change in social and economic organization resulting from the replacement of earlier forms of communication and information storage by a digital format and the development of largescale networks transmitting digital information Introduction to Networking network net39wiirk39 n 1 any arrangement or fabric of parallel wires threads etc crossed at regular intervals by others fastened to them so as to leave open spaces netting mesh 2 a thing resembling this in some way specif a a system of roads canals veins etc that connect with or cross one another b Radio and TV a chain of transmitting stations controlled and operated as a unit 0 a group system etc of interconnected or cooperating individuals 3 the making of nets or netted fabric A computer network is a collection of computers interconnected via a transmission medium eg copper wire optical fiber microwaves satellites etc The computers are usually general purpose programmable hardware devices Dr Tracy Bradley Maples Spring 2009 Types of Networks 0 WANs Widearea networks ARPANET the Internet etc o LANs Local Area Networks Ethernet FDDI Novell NetWare AppleTalk wireless etc o Other networks Telephone networks cable TV networks satellites MAN Metropolitan Area Network SAN System Area Network PAN Personal Area Network etc Motivation Why use Networks Availability of resources Make resources available to anyone on the network regardless of the physical location of the resource or the user Load sharing Process a job on the least crowded or busy machine High reliability Have alternate sources of resources multiple copies Humantohuman communication Allow humans to communicate through email telephone teleconferencing etc Dr Tracy Bradley Maples Spring 2009 History of Networking WANs c 1970 Driving force The need for government and university researchers located in various parts of the United States to communicate ideas and data between computers Examples 0 ARPANET was created in the early seventies o Funded by ARPA DARPA 0 Prototype for what has evolved into the lntemet 0 Created by folks from Berkeley MIT ATampT Bell Labs etc LANs Driving force The creation of the personal computer in the mid 70s and its widespread usage in the mid80s Evolution Sneaker Net e Da ta S Witches e Disk Servers e FIYe Servers Dr Tracy Bradley Maples Spring 2009 Connectivity A network must provide connectivity among a set of computers Defn A link is the physical medium connecting computers on a network For example coaxial cable or optical fiber Defn The computers connected by the physical medium are called nodes Note sometimes these nodes are specialized pieces of hardware Defn A host is a node running a user application program Host machines are interconnected by links to form computer networks There are two types of links 1 PointtoPoint or storeandforward links connect only two nodes 2 Multiple Access or broadcast links allow more than two nodes to share a single physical medium Dr Tracy Bradley Maples Spring 2009 Switched Networks Two types of switched networks 1 Circuitswitched networks provide service by setting up a total path of connected links from the origin to the destination host A control message is first sent to setup a path from the origin to the destination A return signal informs the origin that data transmission may proceed Once data transmission starts all channels in the path are used simultaneously and the entire path remains allocated to the transmission whether or not it is in use 2 Packetswitched networks decompose messages into small pieces called packets These packets are each numbered and make their way through the net in a storeandforward fashion Links are considered busy only when they are currently transmitting packets Switching Performance Issues Header overhead ie the amount of quotextraquot information that must be sent along with the data to ensure proper transmission For large amounts of data circuit switching lt packet switching Transmission delay ie the amount of time it takes data from the time it enters the network until it arrives at its39 destination 0 For short and bursty messages packet switching has the lowest delay 0 For long continuous streams of data circuit switching has the lowest delay Dr Tracy Bradley Maples Spring 2009