Tech 2520 Midterm
Ch 15.12) What category of twisted pair wiring is needed for a 10 Mbps network? 100 Mbps? 1000 Mbps?
A twisted pair ethernet is needed for a 10 Mbps network. Fast ethernet is needed for a 100 Mbps network. A gigabit ethernet is used for a 1000 Mbps network.
Ch 12 Summary Pt 1
Access technologies provide Internet connections to individual residences or small businesses. A variety of access technologies exist, including dialup telephone connections, wireless (using radio frequency or satellite), and wired. Two current access technologies are Digital Subscriber Line (DSL) and cable modems. DSL uses FDM techniques to allow digital communication and a traditional analog voice call to proceed simultaneously on the local loop between a telephone company Central Office and a subscriber. Cable modem service uses FDM to multiplex digital communication over the same coaxial cable system used to carry entertainment channels. When using cable modem technology, cable modems in each neighborhood employ statistical multiplexing to share a single data communications channel.
Ch 15.3) In an 802.3 Ethernet frame, what is the maximum payload size?
In an 802.3 ethernet frame, the maximum payload size is 1492 bytes.
Ch 3 Summary Pt 1
In the Internet, all services are supplied by applications, which use either a stream paradigm or a message paradigm to communicate. The stream paradigm guarantees to deliver a sequence of bytes in order, but can choose how many bytes to pass to a receiver in each batch. The message paradigm preserves boundaries, but allows messages to be lost, duplicated, or delivered out-of-order.
Ch 11.12) Suppose N users compete using a statistical TDM system, and suppose the underlying physical transport can send K bits per second. What is the minimum and maximum data rate that an individual user can experience?
The minimum data rate that an individual user can experience is K/N bps. The maximum data rate is K bps.
Ch 14.1) Explain the three basic approaches used to arbitrate access to a shared medium.
The three basic approaches used to arbitrate access to a shared medium are controlled access protocols, random access protocols, and channelization protocols.
Ch 11.5) An FDM system may assign each channel a range of frequencies. Using a range is essential when which type of modulation is used for each carrier?
Using a range is essential when spread spectrum is used for each carrier.
Ch 12 Summary Pt 2
Technologies like Hybrid Fiber Coax (HFC) and Fiber To The Curb (FTTC) use optical fibers to distribute data to each neighborhood and use coaxial cable to reach an individual subscriber. Future technologies have been proposed that will use optical fiber to deliver higher data rates to each individual residence.
Ch 8.8) Compute the Hamming distance for the following pairs: ( 0000,0001 ), ( 0101,0001 ), ( 1111,1001 ), and ( 0001,1110 )
(0000, 0001) - 1, (0101, 0001) - 1, (1111, 1001) - 2, (0001, 1110) - 4
Ch 8.11) Generate a RAC parity matrix for a ( 20, 12 ) coding of the dataword 100011011111
(20, 12) - 100011011111
Ch 8 Summary Pt 5
The 16-bit checksum used in the Internet can be used with an arbitrary size message. The checksum algorithm divides a message into 16-bit blocks, and computes the arithmetic inverse of the 1s-complement sum of the blocks; the overflow is added back into the checksum.
Ch 16.18) What is a cell cluster, and how does a designer use clusters?
A cell cluster is a group of cells where the small pattern of cells are replicated. A designer uses clusters to implement the principle.
Ch 9 Summary Pt 4
A communication system can be simplex, full-duplex, or half-duplex. A simplex mechanism sends data in a single direction. A full-duplex mechanism transfers data in two directions simultaneously, and a half-duplex mechanism allows two-way transfer, but only allows a transfer in one direction at a given time.
Ch 13.13) How does a computer attached to a shared LAN decide whether to accept a packet?
A computer attaches to a shared LAN decides whether to accept a packet by making a copy of each packet and examines the packet to determine whether it should be accepted or denied.
Ch 10 Summary Pt 3
A modem is a hardware device that includes circuitry to perform both modulation and demodulation; a pair of modems is used for full-duplex communication. Optical, RF, and dialup modems also exist. Because bandwidth is limited, dialup modems use Quadrature Amplitude Modulation schemes. A V.32 modem uses 32 possible combinations of phase shifts and amplitude changes; a V.32bis modem uses 128 possible combinations.
Ch 16.23) Why is a satellite dish shaped in the form of a parabola?
A satellite dish is shaped in the form of a parabola because the shape allows it to reflect the electromagnetic energy arriving from a distant satellite. With the satellite dish aimed at a detector at the focus point, this can guarantee a strong signal.
Ch 3 Summary Pt 4
A single client can access more than one service, a client can access servers on multiple machines, and a server for one service can become a client for other services. Designers and programmers must be careful to avoid circular dependencies among servers.
Ch 12 Summary Pt 4
A telephone company standard known as SONET defines framing for use on a digital circuit. The size of a SONET frame depends on the bit rate of the circuit; one frame always takes 125 μ seconds to send. In addition to its use on point-to-point circuits, SONET can be configured into a ring, which allows hardware to determine if the ring is broken and automatically reconfigure around the malfunction.
Ch 7 Summary Pt 1
A variety of transmission media exists that can be classified as guided / unguided or divided according to the form of energy used (electrical, light, or radio transmission). Electrical energy is used over wires. To protect against electrical interference, copper wiring can consist of twisted pairs or can be wrapped in a shield.
Ch 12.1) What is an access technology?
Access technology is a data communications system that connects an internet subscriber to an internet service provider(ISP).
Ch 15 Summary Pt 3
Although the Ethernet frame format has remained unchanged since the first standard, the cables used for Ethernet and the wiring scheme have changed dramatically. There have been three major versions of Ethernet wiring. Thicknet used a large coaxial cable with transceivers separate from computers. Thinnet used a flexible coaxial cable that ran from computer to computer, and the network interface in each computer contained a transceiver. Twisted Pair Ethernet replaces the coaxial cable with an electronic device called a hub or switch, and uses twisted pair wiring between a computer and a hub. The resulting system has a physical star topology and a logical bus topology.
Ch 12 Summary Pt 3
Although they suffice for individual residences and small businesses, access technologies do not provide sufficient capacity for use in the core of the Internet. To achieve the highest data rates over long distances, service providers and large businesses lease point-to-point circuits from common carriers. Digital circuits use time division multiplexing standards (T-standards in North America or E-standards in Europe). High-speed circuits are defined using the Synchronous Transport Signal (North America) or Synchronous Digital Hierarchy (Europe). A parallel set of Optical Carrier standards exists for use with optical fiber; many professionals use the OC standard names, independent of whether the circuit uses fiber or copper.
Ch 3 Summary Pt 5
An Application Program Interface (API) specifies the details of how an application program interacts with protocol software. Although details depend on the operating system, the socket API is a de facto standard. A program creates a socket, and then invokes a series of functions to use the socket. A server using the stream paradigm calls socket functions: socket, bind, listen, accept, recv, send, and close; a client calls socket, connect, send, recv, and close.
Ch 15.8) What is an Ethernet hub, and what wiring is used with a hub?
An Ethernet hub is an electronic device that serves as the central interconnection. Twisted pair wiring is used with a hub.
Ch 8.6) What does an ideal channel coding scheme achieve?
An ideal channel coding scheme achieves changing bits into a valid codeword which produces an invalid combination
Ch 6 Summary Pt 1
An information source can deliver analog or digital data. An analog signal has the property of being aperiodic or periodic; a periodic signal has properties of amplitude, frequency, and phase. Fourier discovered that an arbitrary curve can be formed from a sum of sine waves; a single sine wave is classified as simple, and a signal that can be decomposed into multiple sine waves is classified as composite.
Ch 13 Summary Pt 2
An organization named IEEE has created standards for data networking. IEEE standards primarily specify details for LANs, and focus on the first two layers of the protocol stack.
Ch 4 Summary Pt 1
Application-layer protocols, required for standardized services, define data representation and data transfer aspects of communication. Representation protocols used with the World Wide Web include HyperText Markup Language (HTML) and the URL standard. The web transfer protocol, which is known as the HyperText Transfer Protocol (HTTP), specifies how a browser communicates with a web server to download or upload contents. To speed downloads, a browser caches page content and uses an HTTP HEAD command to request status information about the page. If the cached version remains current, the browser uses the cached version; otherwise, the browser issues a GET request to download a fresh copy.
Ch 5 Summary Pt 1
Because it deals with transmission across physical media and digital information, data communications draws on physics and mathematics. The focus is on techniques that allow Electrical Engineers to design practical communication mechanisms.
Ch 3 Summary Pt 6
Because many servers are concurrent, sockets are designed to work with concurrent applications. When a new thread is created, the new thread inherits access to all sockets that the creating thread owned.
Ch 14 Summary Pt 4
Because some stations are hidden from others, wireless LANs use Carrier Sense Multi-Access with Collision Avoidance (CSMA / CA). Before transmission of a packet from one computer to another, each of the two computers sends a short control message, which allows all computers in range of the two to know that a transmission is about to occur.
Ch 13 Summary Pt 6
Byte (bit) stuffing techniques permit bytes (sequences of bits) to be reserved for use in marking the start and end of a frame. To insure that a payload does not contain reserved bytes (bit strings), a sender replaces occurrences of reserved values before transmission, and a receiver reverses the change to obtain the original data.
Ch 14.11) Why is CSMA/CA needed in a wireless network?
CSMA/CD is needed in a wireless network because it is used for sending and receiving messages from computers which sends a control message before packet transmission occurs.
Ch 14.8) Expand the acronym CSMA/CD, and explain each part.
CSMA/CD stands for Carrier Sense Multi-Access with Collision Detection. Carrier sense multi-access Monitors a cable to make sure a transmission isn't already in progress which prevents collisions and provides great network utilization. Collision Detection monitors cables to prevent collision, it can detect if there has been a collision when a cable signal is different than the one the station sent.
Ch 11 Summary Pt 3
Code Division Multiplexing (CDM) uses a mathematical combination of codes that permits multiple senders to transmit at the same time without interference. The chief advantages of CDM arise from the ability to scale with low delay(photos on desktop)
Ch 9 Summary Pt 1
Communication systems use parallel or serial transmission. A parallel system has multiple wires, and at any time, each wire carries the signal for one bit. Thus, a parallel transmission system with K wires can send K bits at the same time. Although parallel communication offers higher speed, most communication systems use lower-cost serial mechanisms that send one bit at a time.
Ch 6 Summary Pt 6
Compression is lossy or lossless. Lossy compression is most appropriate for images, audio, or video that will be viewed by humans because loss can be controlled to keep changes below the threshold of human perception. Lossless compression is most appropriate for documents or data that must be preserved exactly.
Ch 14 Summary Pt 2
Controlled access protocols allow independent stations to engage in statistical multiplexing. Polling uses a central controller that repeatedly checks whether stations are ready to send a packet. A reservation system, often used with satellites, requires stations to declare whether they are ready for the next round of transmission. Token passing, often used with a ring topology, passes a control message among stations; a station can transmit a packet when it receives the token.
Ch 8 Summary Pt 6
Cyclic redundancy codes (CRCs) are used in high-speed data networks because a CRC accepts a message of arbitrary length, provides extremely good error detection, and has an efficient hardware implementation. CRC techniques have a mathematical basis, and have been studied extensively. A CRC computation can be viewed as computing the remainder of a binary division, computing the remainder of a polynomial division, or an operation using Galois field theory. The hardware to perform a CRC computation uses a shift register and exclusive or operations
Ch 13 Summary Pt 1
Data networks can be classified as using circuit-switching or packet-switching. Packet switching, which forms the basis of the Internet, is a form of statistical multiplexing in which senders divide messages into small packets. Packet switched network technologies are classified as Local Area Networks (LANs), Wide Area Networks (WANs), and Metropolitan Area Networks (MANs); LANs and WANs are the most popular.
Ch 3 Summary Pt 3
Each computer is assigned a unique address, and each service, such as email or web access, is assigned a unique identifier known as a protocol port number. When a server starts, it specifies a protocol port number; when contacting a server, a client specifies the address of the computer on which the server runs as well as the protocol port number the server is using.
Ch 13 Summary Pt 4
Each packet sent across a LAN contains a MAC address that identifies the intended recipient. The IEEE standard for MAC addresses specifies a 48-bit value divided into two fields: one that identifies the organization that assigns the address and another that gives a unique value for the particular piece of hardware to which the address is assigned. An address can specify unicast (a single computer), broadcast (all computers on a given LAN), or multicast (a subset of computers on a LAN).
Ch 4 Summary Pt 5
Email access protocols, such as POP3 and IMAP, permit a user to access a mailbox. Access has become popular because a subscriber can allow an ISP to run an email server and maintain the user's mailbox.
Ch 16 Summary Pt 4
Emerging wireless systems use software programmable radios that allow software to control all aspects of radio transmission. Programmable radios are expensive, and are currently available for military and special uses.
Ch 6 Summary Pt 2
Engineers use two main representations of composite signals. A time domain representation shows how the signal varies over time. A frequency domain representation shows the amplitude and frequency of each component in the signal. The bandwidth, which is the difference between the highest and lowest frequencies in a signal is especially clear on a frequency domain graph.
Ch 15 Summary Pt 1
Ethernet technology, first invented in the 1970s, has become the de facto standard for wired Local Area Networks. An Ethernet frame begins with a 14-byte header that contains a 48-bit destination address, 8-bit source address, and 16-bit type field. Although IEEE standard 802.3 attempted to define a new frame format with an additional 8-byte header, the IEEE version is seldom used.
Ch 8 Summary Pt 2
Forward error correction arranges for a sender to add redundant bits to the data and encode the result before transmission across a channel, and arranges for a receiver to decode and check incoming data. A coding scheme is (n, k) if a dataword contains k bits and a codeword contains n bits.
Ch 13.8) What are the four basic LAN topologies?
Four basic LAN topologies are: Bus, Ring, Star, Mesh.
Ch 13 Summary Pt 3
Four basic shapes or topologies are used to characterize LANs: bus, star, ring, and mesh. Mesh topologies are seldom used because they are expensive.
Ch 11.2) What are the four basic types of multiplexing?
Four basic types of multiplexing are: Frequency Division Multiplexing, Wavelength Division Multiplexing, Time Division Multiplexing, Code Division Multiplexing.
Ch 7.1) What is the difference between guided and unguided transmission?
Guided transmission has physical existence, signals that propagate through a specified path and in the form of electrical energy, is ideal for point to point communication, is a wired transmission, and maintenance cost is high. Where as unguided transmission has no physical existence, signals that propagate through a free space and in the form of electromagnetic waves, is ideal for broadcasting, is a wireless transmission and maintenance cost is low compared to guided transmission.
Ch 4 Summary Pt 2
HTTP uses textual messages. Each response from a server begins with a header that describes the response. Lines in the header begin with a numeric value, represented as ASCII digits, that tells the status (e.g., whether a request is in error). Data that follows the header can contain arbitrary binary values
Ch 16 Summary Pt 2
In addition to LANs, wireless technologies are used for MANs and PANs. The main MAN technology is known as WiMAX, which can be used for backhaul or access. A variety of PAN technologies exist, including Bluetooth, Ultra Wideband, Zigbee, and IrDA. RFID tags provide another form of wireless communication used primarily for inventory and shipping.
Ch 3.3) Give six characteristics of Internet message communication
Internet message communication(connectionless), Follows many-to-many communication techniques, involves sequence of individual messages, the length of each message is limited to 64 kbytes, internet message communication is specially used for multimedia applications, and it is built on a UDP protocol
Ch 13.5) What are the characteristics of LANs, MANs, and WANs?
LAN(Local Area Network) is used for short distance communication, has little noise and interference, speed ranges from 10 to 1.0 Gbps, Typically used at places like education institutes. MAN(Metropolitan Area Network) is an interconnection of LAN to form a larger network, covers a distance from 5 to 50 Km, Most likely to be used in a city, speed is lower than LAN's with a speed of 44 to 155 Mbps. WAN(Wide Area Network) covered a wide area and can be used to communicate throughout the world, uses satellites, chance of noise and interference due to it being wireless, the date rate can depend on the internet service provider.
Ch 7.14) Can laser communication be used from a moving vehicle? Explain
Laser communication can't be used from a moving vehicle. Laser's can only cover a few centimeters of wide areas. The laser's must be aligned precisely in order to be sure the senders beam will reach the equipment.
Ch 7 Summary Pt 2
Light energy can be used over optical fiber or for point-to-point communication using infrared or lasers. Because it reflects from the boundary between the fiber and cladding, light stays in an optical fiber provided the angle of incidence is greater than the critical angle. As it passes along a fiber, a pulse of light disperses; dispersion is greatest in multimode fiber and least in single mode fiber. Single mode fiber is more expensive.
Ch 15 Summary Pt 4
Like earlier versions of Ethernet, the first Twisted Pair technology operated at 10 Mbps, and was designated 10BaseT. A version formally named 100BaseT operates at 100 Mbps, and is known commercially as Fast Ethernet. A third version, called Gigabit Ethernet or Gig-E, operates at 1000 Mbps, which is equivalent to 1 Gbps. Hardware for higher-speed Ethernet automatically senses when a low-speed device is connected, and reduces the speed accordingly
Ch 10 Summary Pt 1
Long distance communication systems use a modulated carrier wave to transfer information. A carrier is modulated by changing the amplitude, frequency, or phase. Amplitude and frequency modulation are the most common forms used with an analog input.
Ch 16 Summary Pt 1
Many wireless communication technologies exist and are used to create wireless LANs, PANs, MANs, and WANs. IEEE has standardized several LAN and MAN technologies. Wi-Fi uses the IEEE 802.11 standards, with variants each assigned a suffix, such as 802.11b or 802.11g. Wireless LANs can be ad hoc or can use an infrastructure architecture with access points; the frame format includes a MAC address for an access point as well as a MAC address for a router beyond the access point.
Ch 11 Summary Pt 1
Multiplexing is a fundamental concept in data communications. A multiplexing mechanism allows pairs of senders and receivers to communicate over a shared medium. A multiplexor sends inputs from many senders over a shared medium, and a demultiplexor separates and delivers the items.
Ch 7 Summary Pt 5
Nyquist's Theorem gives a theoretical limit on the channel capacity of transmission media when no noise is present; Shannon's Theorem specifies the channel capacity in realistic situations where noise is present. The signal-to-noise ratio, a term in Shannon's Theorem, is often measured in decibels.
Ch 8 Summary Pt 3
One measure of an encoding assesses the chance that an error will change a valid codeword into another valid codeword. The minimum Hamming distance provides a precise measure
Ch 6.11) Suppose an engineer increases the number of possible signal levels from two to four. How many more bits can be sent in the same amount of time? Explain.
One more bit can be sent in the same amount of time.
Ch 8 Summary Pt 1
Physical transmission systems are susceptible to interference, distortion, and attenuation, all of which can cause errors. Transmission errors can result in single-bit errors or burst errors, and erasures can occur whenever a received signal is ambiguous (i.e., neither clearly 1 nor clearly 0). To control errors, data communications systems employ a forward error correction mechanism or use an automatic repeat request (ARQ) technique.
Ch 6 Summary Pt 5
Pulse code modulation and delta modulation are used to convert an analog signal to digital. The PCM scheme used by the telephone system employs 8-bit quantization and takes 8,000 samples per second, which results in a rate of 64 Kbps.
Ch 14 Summary Pt 3
Random access protocols allow stations to contend for access. The historic ALOHA protocol used two frequencies, one for inbound and one for outbound transmissions; if a station did not receive a copy of its packet, the station retransmitted. Ethernet uses Carrier Sense Multi-Access with Collision Detection (CSMA / CD) to permit access to a shared cable. In addition to preventing a station from transmitting while another transmission is in progress, the protocol uses binary exponential backoff to recover from collisions.
Ch 9 Summary Pt 2
Serial communication requires a sender and receiver to agree on timing and the order in which bits are sent. Transmission order refers to whether the most-significant or least-significant bit is sent first and whether the most-significant or least-significant byte is sent first.
Ch 9.1) Describe the difference between serial and parallel transmission.
Serial transmission only sends 1 bit at a time, transmission is very slow, is less costly, and never faces timing problems. Parallel transmission transfers multiple data bits at the same time, high speed transmission, can face timing problems and can be more costly compared to serial transmission.
Ch 8 Summary Pt 4
Simplistic block codes, such as a single parity bit added to each byte, can detect an odd number of bit errors, but cannot detect an even number of bit changes. A Row And Column (RAC) code can correct single-bit errors, detect up to three errors in a block, and can detect any error in which an odd number of bits are changed.
Ch 6.3) Why are sine waves fundamental to data communications?
Sine waves are fundamental to data communication because they produce a signal that corresponds to a sine wave as a function of time.
Ch 3.2) Give six characteristics of Internet stream communication
Six characteristics of Internet stream communication are: Stream communication being connection-oriented, following 1-to-1 communication techniques, Uses a sequence of individual bytes, is used by most applications, built on a TCP protocol, and the length of the transfer is arbitrary.
Ch 16 Summary Pt 3
Wireless WANs use cellular and satellite technologies. Cellular technologies are classified as 1G (analog), 2G (digital voice), 3G (digital voice plus data), and 4G (high-speed digital voice and data); many technologies exist. VSAT satellite technologies make it possible for businesses and consumers to have dish antennas on their property.
Ch 7 Summary Pt 3
Wireless communication uses electromagnetic energy. The frequency used determines both the bandwidth and the propagation behavior; low frequencies follow the earth's surface, higher frequencies reflect from the ionosphere, and the highest frequencies behave like visible light by requiring a direct, unobstructed path from the transmitter to the receiver
Ch 7.8) Explain why light does not leave an optical fiber when the fiber is bent into an arc.
light does not leave an optical fiber when the fiber is bent into an arc because the arc causes the light to strike at an angle.
Ch 4 Summary Pt 7
The DNS uses caching to maintain efficiency; when an authoritative server provides an answer, each server that transfers the answer also places a copy in its cache. To prevent cached copies from becoming stale, the authority for a name specifies how long the name can be cached.
Ch 4 Summary Pt 6
The Domain Name System (DNS) provides automated mapping from humanreadable names to computer addresses. DNS consists of many servers that each control one part of the namespace. Servers are arranged in a hierarchy, and a server knows the locations of servers in the hierarchy.
Ch 15 Summary Pt 2
The Ethernet type field is used for demultiplexing after a frame arrives at its destination. When creating a frame, a sender specifies the type; a recipient uses the type to determine which module should process the frame.
Ch 4 Summary Pt 3
The File Transfer Protocol (FTP) is frequently used for file download. FTP requires a client to log into the server's system; FTP supports a login of anonymous and password guest for public file access. The most interesting aspect of FTP arises from its unusual use of connections. A client establishes a control connection that is used to send a series of commands. Whenever a server needs to send data (e.g., a file download or the listing of a directory), the server acts as a client and the client acts as a server. That is, the server initiates a new data connection to the client. Once a single file has been sent, the data connection is closed.
Ch 6.7) What does Fourier analysis of a composite wave produce?
The Fourier analysis of a composite wave produces a set of sine functions with a frequency, amplitude and phase. As well as decomposes a composite signal into constituent parts.
Ch 14 Summary Pt 1
The IEEE MAC layer contains protocols that control access to a shared medium. Channelization protocols consist of extensions to time, frequency, and code division multiplexing; the extensions are known as Frequency, Time, and Code Division MultiAccess. Static or dynamic channel allocation is possible.
Ch 16.7) List the IEEE standards that have been proposed or created for wireless LANs.
The IEEE standards that have been proposed or created for wireless LANs are: 802.11e, 802.11h, 802.11i, 802.11k, 802.11n, 802.11p, 802.11r, and 802.11s.
Ch 3 Summary Pt 2
The basic communication model used by network applications is known as the client-server model. A program that passively waits for contact is called a server, and a program that actively initiates contact with a server is called a client.
Ch 6 Summary Pt 3
The baud rate of a signal is the number of times the signal can change per second. A digital signal that uses multiple signal levels can represent more than one bit per change, making the effective transmission rate the number of levels times the baud rate. Although it has infinite bandwidth, a digital signal can be approximated with three sine waves.
Ch 7 Summary Pt 4
The chief nonterrestrial communication technology relies on satellites. The orbit of a GEO satellite matches the earth's rotation, but the high altitude incurs a delay measured in tenths of seconds. LEO satellites have low delay, and move across the sky quickly; clusters are used to relay messages
Ch 4.1) What details does an application protocol specify?
The details an application protocol specifies are: Syntax and semantics of messages, what actions to follow if an error occurs, if the two sides know when to end the communication, and if the client or server initiates interaction
Ch 9 Summary Pt 5
The distinction between Data Communications Equipment and Data Terminal Equipment was originally devised to denote whether a provider or a subscriber owned equipment. The key concept arises from the ability to define an interface for a user that offers a different service than the underlying communication system.
Ch 7.23) If a system has an average power level of 100, an average noise level of 33.33, and a bandwidth of 100 MHz, what is the effective limit on channel capacity?
The effective limit on channel capacity is 200 bps.
Ch 10.9) Assuming a signal-to-noise ration of 30 dB, what is the maximum data rate that can be achieved for the dialup bandwidth illustrated in Figure 10.11?
The maximum data rate that can be achieved for the dialup bandwidth illustrated in Figure 10.11 is 24,000 bps.
Ch 15.1) How large is the maximum Ethernet frame, including the CRC?
The maximum ethernet frame including CRC is 1518 bytes large.
Ch 5.5) Which piece of a data communications system prevents transmission errors from corrupting data?
The piece of a data communications system that prevents transmission errors from corrupting data is a channel encoder and decoder.
Ch 6.20) If the maximum frequency audible to a human ear is 20,000 Hz, at what rate must the analog signal from a microphone be sampled when converting it to digital?
The rate analog signal from a microphone be sampled when converting it to digital must be 40,000
Ch 13 Summary Pt 5
The term frame is used to specify the format of a packet on a particular network. A frame consists of two conceptual parts: a header that contains meta-information and a payload area that contains the data being sent. For a network that transmits characters, a frame can be formed by using one byte value to indicate the beginning of the frame and another to indicate the end of the frame.
Ch 9 Summary Pt 3
The three types of timing are: asynchronous, in which transmission can occur at any time and the communication system can remain idle between transmissions, synchronous, in which bits are transmitted continually and data is grouped into frames, and isochronous, in which transmission occurs at regular intervals with no extra delay at frame boundaries.
Ch 4.20) What are the two main email access protocols?
The two main email access protocols are: POP3(Post Office protocol version 3) and IMAP(Internet Mail Access Protocol).
Ch 11 Summary Pt 2
There are four basic approaches to multiplexing: frequency division, time division, wavelength division, and code division. Frequency Division Multiplexing (FDM) permits simultaneous communication over multiple channels, each of which corresponds to a separate frequency of electromagnetic radiation. Wavelength Division Multiplexing (WDM) is a form of frequency division multiplexing that sends frequencies of light, called wavelengths, over an optical fiber.
Ch 4 Summary Pt 4
Three types of application-layer protocols are used with electronic mail: transfer, representation, and access. The Simple Mail Transfer Protocol serves as the key transfer standard; SMTP can only transfer a textual message. There are two representation standards for email: RFC 2822 defines the mail message format to be a header and body separated by a blank line. The Multi-purpose Internet Mail Extensions (MIME) standard defines a mechanism to send binary files as attachments to an email message. MIME inserts extra header lines that tell the receiver how to interpret the message. MIME requires a sender to encode a file as printable text.
Ch 11 Summary Pt 4
Time Division Multiplexing (TDM) sends one item at a time over the shared medium. A Synchronous TDM system transmits items with no idle time between them, usually using round-robin selection. A statistical TDM system avoids empty slots by skipping any sender that does not have an item ready to send during its turn.
Ch 12.14) Use the Web to find the approximate size of a movie on DVD. How long does it take to download a movie over a T1 line? Over a T3 line? (Ignore overhead.)
To download a movie over a T1 line, it would take a connection speed of 1.54 Mbps. For T3 it would take a connection speed of 45 Mbps.
Ch 5 Summary Pt 2
To simplify understanding, engineers have devised a conceptual framework for data communications systems. The framework divides the entire subject into a set of subtopics. Each of the successive chapters in this part of the text discuss one of the subtopics.
Ch 3.1) What are the two basic communication paradigms used in the Internet?
Two basic communication paradigms used in the Internet are: Stream Paradigms(a sequence of bytes which flows from one application to another) and Message Paradigms(Network chooses to accept and send messages).
Ch 3.14) What two identifiers are used to specify a particular server?
Two identifiers used to specify a particular server are: Identifiers that are responsible for the computer where the server is running on and an identifier used for a particular service on the computer
Ch 6 Summary Pt 4
Various line coding techniques exist. The Manchester Encoding, used with Ethernet networks, is especially important. Rather than using absolute signal levels to represent bits, the Manchester Encoding uses transitions in signal level. The Differential Manchester Encoding uses relative transitions, and has the property that it works even if the two wires are reversed.
Ch 10 Summary Pt 2
When a digital signal is used as input, modulation is known as shift keying. As with analog modulation, shift keying changes a carrier. However, only a fixed set of possibilities are allowed. A constellation diagram is used to represent the possibilities for phase shift keying. If the system permits a power of two possibilities, multiple input bits can be used to select a possibility at each point in time. Quadrature Amplitude Modulation combines amplitude shift keying and phase shift keying to produce more possibilities.
Ch 4.12) When a user requests an FTP directory listing, how many TCP connections are formed? Explain.
When a user requests an FTP directory listing, 2 TCP connections are formed. Those 2 TCP connections are control connection and data connection. Control connection is the original connection a client created which is reserved for commands. A data connection is what is used to send a response to a client's requests.
Ch 3.8) When two applications communicate over the Internet, which one is the server?
When two applications communicate over the internet, the application who communicated first is the server.
Ch 9.8) When two humans hold a conversation, do they use simplex, half-duplex, or full-duplex transmission?
When two humans hold a conversation, they use full-duplex transmission due to how this system allows transmission in two directions simultaneously.
Ch 10.2) When using amplitude modulation, does it make sense for a 1 Hz carrier to be modulated by a 2 Hz sine wave? Why or why not?
When using amplitude modulation, it does not make sense for a 1 Hz carrier to be modulated by a 2 Hz sine wave due to the fact that the carrier frequency must be at least twice as large as a modulating signal frequency in order to transmit data without any loss and since a high frequency signal needs less bandwidth to transfer data.
