* Data communication is the transfer of data from one device to another via some form of transmission medium.
· A data communications system must transmit data to the correct destination in an accurate and timely manner.
· The five components that make up a data communications system are the message, sender, receiver, medium, and protocol.
· Text, numbers, images, audio, and video are different forms of information.
· Data flow between two devices can occur in one of three ways: simplex, half-duplex, or full-duplex.
· A network is a set of communication devices connected by media links.
· In a point-to-point connection, two and only two devices are connected by a dedicated link. In a multipoint connection, three or more devices share a link.
· Topology refers to the physical or logical arrangement of a network. Devices may be arranged in a mesh, star, bus, or ring topology.
· A network can be categorized as a local area network (LAN), a metropolitan-area network (MAN), or a wide area network (WAN).
· A LAN is a data communication system within a building, plant, or campus, or between nearby buildings.
· A MAN is a data communication system covering an area the size of a town or city.
· A WAN is a data communication system spanning states, countries, or the whole world.
· An internet is a network of networks.
· The Internet is a collection of many separate networks.
· TCP/IP is the protocol suite for the Internet.
· There are local, regional, national, and international Internet service providers (ISPs).
· A protocol is a set of rules that governs data communication; the key elements of a protocol are syntax, semantics, and timing.
· Standards are necessary to ensure that products from different manufacturers can work together as expected.
· The ISO, ITU-T, ANSI, IEEE, and EIA are some of the organizations involved in standards creation.
· Forums are special-interest groups that quickly evaluate and standardize new technologies.
· A Request for Comment (RFC) is an idea or concept that is a precursor to an Internet standard.
· Network Models
· * The five-layer model provides guidelines for the development of universally compatible networking protocols.
· The physical, data link, and network layers are the network support layers.
· The application layer is the user support layer.
· The transport layer links the network support layers and the user support layer.
· The physical layer coordinates the functions required to transmit a bit stream over a physical medium.
· The data link layer is responsible for delivering data units from one station to the next without errors.
· The network layer is responsible for the source-to-destination delivery of a packet across multiple network links.
· The transport layer is responsible for the process-to-process delivery of the entire message.
· The application layer enables the users to access the network.
Data and Signals Data must be transformed into electromagnetic signals prior to transmission across a network.
· Data and signals can be either analog or digital.
· A signal is periodic if it consists of a continuously repeating pattern.
· Each sine wave can be characterized by its amplitude, frequency, and phase.
· Frequency and period are inverses of each other.
· A time-domain graph plots amplitude as a function of time.
· A frequency-domain graph plots each sine wave’s peak amplitude against its frequency.
· By using Fourier analysis, any composite signal can be represented as a combination of simple sine waves.
· The spectrum of a signal consists of the sine waves that make up the signal.
· The bandwidth of a signal is the range of frequencies the signal occupies. Bandwidth is determined by finding the difference between the highest and lowest frequency components.
· Bit rate (number of bits per second) and bit interval (duration of 1 bit) are terms used to describe digital signals.
· A digital signal is a composite signal with an infinite bandwidth.
· Bit rate and bandwidth are proportional to each other.
· The Nyquist formula determines the theoretical data rate for a noiseless channel.
· The Shannon capacity determines the theoretical maximum data rate for a noisy channel.
· Attenuation, distortion, and noise can impair a signal.
· Attenuation is the loss of a signal’s energy due to the resistance of the medium.
· The decibel measures the relative strength of two signals or a signal at two different points.
· Distortion is the alteration of a signal due to the differing propagation speeds of each of the frequencies that make up a signal.
· Noise is the external energy that corrupts a signal.
· We can evaluate transmission media by throughput, propagation speed, and propagation time.
· The wavelength of a frequency is defined as the propagation speed divided by the frequency.
·
· Digital Transmission* Line coding is the process of converting binary data to a digital signal.
· The number of different values allowed in a signal is the signal level. The number of symbols that represent data is the data level.
· Bit rate is a function of the pulse rate and data level.
· Line coding methods must eliminate the dc component and provide a means of synchronization between the sender and the receiver.
· Line coding methods can be classified as unipolar, polar, or bipolar.
· NRZ, RZ, Manchester, and differential Manchester encoding are the most popular polar encoding methods.
· AMI is a popular bipolar encoding method.
· Block coding can improve the performance of line coding through redundancy and error correction.
· Block coding involves grouping the bits, substitution, and line coding.
· 4B/5B, 8B/10B, and 8B/6T are common block coding methods.
· Analog-to-digital conversion relies on PCM (pulse code modulation).
· PCM involves sampling, quantizing, and line coding.
· The Nyquist theorem says that the sampling rate must be at least twice the highest-frequency component in the original signal.
· Digital transmission can be either parallel or serial in mode.
· In parallel transmission, a group of bits is sent simultaneously, with each bit on a separate line.
· In serial transmission, there is only one line and the bits are sent sequentially.
· Serial transmission can be either synchronous or asynchronous.
· In asynchronous serial transmission, each byte (group of 8 bits) is framed with a start bit and a stop bit. There may be a variable-length gap between each byte.
· In synchronous serial transmission, bits are sent in a continuous stream without start and stop bits and without gaps between bytes. Regrouping the bits into meaningful bytes is the responsibility of the receiver.
Analog Transmission
· * Digital-to-analog modulation can be accomplished using the following: *Amplitude shift keying (ASK)—the amplitude of the carrier signal varies. *Frequency shift keying (FSK)—the frequency of the carrier signal varies. *Phase shift keying (PSK)—the phase of the carrier signal varies. *Quadrature amplitude modulation (QAM)—both the phase and amplitude of the carrier signal vary.
· QAM enables a higher data transmission rate than other digital-to-analog methods.
· Baud rate and bit rate are not synonymous. Bit rate is the number of bits transmit-ted per second. Baud rate is the number of signal units transmitted per second. One signal unit can represent one or more bits.
· The minimum required bandwidth for ASK and PSK is the baud rate.
· The minimum required bandwidth (BW) for FSK modulation is BW =f c1 .f c0 + N baud , where f c1 is the frequency representing a 1 bit, f c0 is the frequency representing a 0 bit, and N baud is the baud rate.
· A regular telephone line uses frequencies between 600 and 3000 Hz for data communication.
· ASK modulation is especially susceptible to noise.
· Because it uses two carrier frequencies, FSK modulation requires more bandwidth than ASK and PSK.
· * PSK and QAM modulation have two advantages over ASK: *They are not as susceptible to noise. *Each signal change can represent more than one bit.
· Trellis coding is a technique that uses redundancy to provide a lower error rate.
· The 56K modems are asymmetric; they download at a rate of 56 Kbps and upload at 33.6 Kbps.
· * Analog-to-analog modulation can be implemented by using the following: * Amplitude modulation (AM) * Frequency modulation (FM) * Phase modulation (PM)
· In AM radio, the bandwidth of the modulated signal must be twice the bandwith of the modulating signal.
· In FM radio, the bandwith of the modulated signal must be 10 times the bandwidth of the modulating signal.
Wired LANs: Ethernet Medium access methods can be categorized as random, controlled, or canalized.
· In the carrier sense multiple-access (CSMA) method, a station must listen to the medium prior to sending data onto the line.
· A persistence strategy defines the procedure to follow when a station senses an occupied medium.
· Carrier sense multiple access with collision detection (CSMA/CD) is CSMA with a postcollision procedure.
· Carrier sense multiple access with collision avoidance (CSMA/CA) is CSMA with procedures that avoid a collision.
· Reservation, polling, and token passing are controlled-access methods.
· In the reservation access method, a station reserves a slot for data by setting its flag in a reservation frame.
· In the polling access method, a primary station controls transmissions to and from secondary stations.
· In the token-passing access method, a station that has control of a frame called a token can send data.
· Channelization is a multiple-access method in which the available bandwidth of a link is shared in time, frequency, or through code, between stations on a network.
· FDMA, TDMA, and CDMA are channelization methods.
· In FDMA, the bandwith is divided into bands; each band is reserved fro the use of a specific station.
· In TDMA, the bandwidth is not divided into bands; instead the bandwidth is timeshared.
· In CDMA, the bandwidth is not divided into bands, yet data from all inputs are transmitted simultaneously.
· CDMA is based on coding theory and uses sequences of numbers called chips. The sequences are generated using Walsh tables.
Wireless LANs
Ethernet is the most widely used local area network protocol.
· The IEEE 802.3 standard defines 1-persistent CSMA/CD as the access method for first-generation 10-Mbps Ethernet.
· The data link layer of Ethernet consists of the LLC sublayer and the MAC sublayer.
· The MAC sublayer is responsible for the operation of the CSMA/CD access method.
· Each station on an Ethernet network has a unique 48-bit address imprinted on its network interface card (NIC).
· The minimum frame length for 10-Mbps Ethernet is 64 bytes; the maximum is 1518 bytes.
· The physical layer of 10-Mbps Ethernet can be composed of four sublayers: the physical layer signaling (PLS) sublayer, the attachment unit interface (AUI) sublayer, the medium attachment unit (MAU) sublayer, and the medium-dependent interface (MDI) sublayer.
· The common baseband implementations of 10-Mbps Ethernet are 10Base5 (thick Ethernet), 10Base2 (thin Ethernet), 10Base-T (twisted-pair Ethernet), and 10Base-FL (fiber link Ethernet).
· The 10Base5 implementation of Ethernet uses thick coaxial cable. The 10Base2 implementation of Ethernet uses thin coaxial cable. The 10Base-T implementation of Ethernet uses twisted-pair cable that connects each station to a port in a hub. The 10Base-FL implementation of Ethernet uses fiber-optic cable.
· A bridge can raise the bandwidth and separate the collision domains on an Ethernet LAN.
· A switch allows each station on an Ethernet LAN to have the entire capacity of the network to itself.
· Full-duplex mode doubles the capacity of each domain and deletes the need for the CSMA/CD method.
· Fast Ethernet has a data rate of 100 Mbps.
· In Fast Ethernet, autonegotiation allows two devices to negotiate the mode or data rate of operation.
· The Fast Ethernet reconciliation sublayer is responsible for the passing of data in 4-bit format to the MII.
· The Fast Ethernet MII is an interface that can be used with both a 10- and a 100-Mbps interface.
· The Fast Ethernet PHY sublayer is responsible for encoding and decoding.
· The common Fast Ethernet implementations are 100Base-TX (two pairs of twisted-pair cable), 100Base-FX (two fiber-optic cables), and 100Base-T4 (four pairs of voice-grade, or higher, twisted-pair cable).
· Gigabit Ethernet has a data rate of 1000 Mbps.
· Gigabit Ethernet access methods include half-duplex using traditional CSMA/CD (not common) and full-duplex (most popular method).
· The Gigabit Ethernet reconciliation sublayer is responsible for sending 8-bit parallel data to the PHY sublayer via a GMII interface.
· The Gigabit Ethernet GMII defines how the reconciliation sublayer is to be connected to the PHY sublayer.
· The Gigabit Ethernet PHY sublayer is responsible for encoding and decoding.
· The common Gigabit Ethernet implementations are 1000Base-SX (two optical fibers and a shortwave laser source), 100Base-LX (two optical fibers and a long-wave laser source), and 100Base-T (four twisted pairs).
Network Layer: Internet Protocol
· The Address Resolution Protocol (ARP) is a dynamic mapping method that finds a physical address, given an IP address.
· An ARP request is broadcast to all devices on the network.
· An ARP reply is unicast to the host requesting the mapping.
· IP is an unreliable connectionless protocol responsible for source-to-destination delivery.
· Packets in the IP layer are called datagrams.
· A datagram consists of a header (20 to 60 bytes) and data.
· The MTU is the maximum number of bytes that a data link protocol can excapsulate. MTUs vary from protocol to protocol.
· Fragmentation is the division of a datagram into smaller units to accommodate the MTU of a data link protocol.
· The fields in the IP header that relate to fragmentation are the identification number, the fragmentation flags, and the fragmentation offset.
· The Internet Control Message Protocol (ICMP) sends five types of error-reporting messages and four pairs of query messages to support the unreliable and connectionless Internet Protocol (IP).
· ICMP messages are encapsulated in IP datagrams.
· The destination-unreachable error message is sent to the source host when a datagram is undeliverable.
· The source-quench error message is sent in an effort to alleviate congestion.
· The time-exceeded message notifies a source host that (1) the time-to-live field has reached zero or (2) fragments of a message have not arrived in a set amount of time.
· The parameter-problem message notifies a host that there is a problem in the header field of a datagram.
· The redirection message is sent to make the routing table of a host more effective.
· The echo-request and echo-reply messages test the connectivity between two systems.
· The time-stamp-request and time-stamp-reply messages can determine the roundtrip time between two systems or the difference in time between two systems.
· The address-mask request and address-mask reply messages are used to obtain the subnet mask.
· The router-solicitation and router-advertisement messages allow hosts to update their routing tables.
· IPv6, the latest verstion of the Internet Protocol, has a 128-bit address space, a resource allocation, and increased security measures.
· IPv6 uses hexadecimal colon notation with abbreviation methods available.
· Three strategies used to make the transition from version 4 to version 6 are dual stack, tunneling, and header translation.
· A data communications system must transmit data to the correct destination in an accurate and timely manner.
· The five components that make up a data communications system are the message, sender, receiver, medium, and protocol.
· Text, numbers, images, audio, and video are different forms of information.
· Data flow between two devices can occur in one of three ways: simplex, half-duplex, or full-duplex.
· A network is a set of communication devices connected by media links.
· In a point-to-point connection, two and only two devices are connected by a dedicated link. In a multipoint connection, three or more devices share a link.
· Topology refers to the physical or logical arrangement of a network. Devices may be arranged in a mesh, star, bus, or ring topology.
· A network can be categorized as a local area network (LAN), a metropolitan-area network (MAN), or a wide area network (WAN).
· A LAN is a data communication system within a building, plant, or campus, or between nearby buildings.
· A MAN is a data communication system covering an area the size of a town or city.
· A WAN is a data communication system spanning states, countries, or the whole world.
· An internet is a network of networks.
· The Internet is a collection of many separate networks.
· TCP/IP is the protocol suite for the Internet.
· There are local, regional, national, and international Internet service providers (ISPs).
· A protocol is a set of rules that governs data communication; the key elements of a protocol are syntax, semantics, and timing.
· Standards are necessary to ensure that products from different manufacturers can work together as expected.
· The ISO, ITU-T, ANSI, IEEE, and EIA are some of the organizations involved in standards creation.
· Forums are special-interest groups that quickly evaluate and standardize new technologies.
· A Request for Comment (RFC) is an idea or concept that is a precursor to an Internet standard.
· Network Models
· * The five-layer model provides guidelines for the development of universally compatible networking protocols.
· The physical, data link, and network layers are the network support layers.
· The application layer is the user support layer.
· The transport layer links the network support layers and the user support layer.
· The physical layer coordinates the functions required to transmit a bit stream over a physical medium.
· The data link layer is responsible for delivering data units from one station to the next without errors.
· The network layer is responsible for the source-to-destination delivery of a packet across multiple network links.
· The transport layer is responsible for the process-to-process delivery of the entire message.
· The application layer enables the users to access the network.
Data and Signals Data must be transformed into electromagnetic signals prior to transmission across a network.
· Data and signals can be either analog or digital.
· A signal is periodic if it consists of a continuously repeating pattern.
· Each sine wave can be characterized by its amplitude, frequency, and phase.
· Frequency and period are inverses of each other.
· A time-domain graph plots amplitude as a function of time.
· A frequency-domain graph plots each sine wave’s peak amplitude against its frequency.
· By using Fourier analysis, any composite signal can be represented as a combination of simple sine waves.
· The spectrum of a signal consists of the sine waves that make up the signal.
· The bandwidth of a signal is the range of frequencies the signal occupies. Bandwidth is determined by finding the difference between the highest and lowest frequency components.
· Bit rate (number of bits per second) and bit interval (duration of 1 bit) are terms used to describe digital signals.
· A digital signal is a composite signal with an infinite bandwidth.
· Bit rate and bandwidth are proportional to each other.
· The Nyquist formula determines the theoretical data rate for a noiseless channel.
· The Shannon capacity determines the theoretical maximum data rate for a noisy channel.
· Attenuation, distortion, and noise can impair a signal.
· Attenuation is the loss of a signal’s energy due to the resistance of the medium.
· The decibel measures the relative strength of two signals or a signal at two different points.
· Distortion is the alteration of a signal due to the differing propagation speeds of each of the frequencies that make up a signal.
· Noise is the external energy that corrupts a signal.
· We can evaluate transmission media by throughput, propagation speed, and propagation time.
· The wavelength of a frequency is defined as the propagation speed divided by the frequency.
·
· Digital Transmission* Line coding is the process of converting binary data to a digital signal.
· The number of different values allowed in a signal is the signal level. The number of symbols that represent data is the data level.
· Bit rate is a function of the pulse rate and data level.
· Line coding methods must eliminate the dc component and provide a means of synchronization between the sender and the receiver.
· Line coding methods can be classified as unipolar, polar, or bipolar.
· NRZ, RZ, Manchester, and differential Manchester encoding are the most popular polar encoding methods.
· AMI is a popular bipolar encoding method.
· Block coding can improve the performance of line coding through redundancy and error correction.
· Block coding involves grouping the bits, substitution, and line coding.
· 4B/5B, 8B/10B, and 8B/6T are common block coding methods.
· Analog-to-digital conversion relies on PCM (pulse code modulation).
· PCM involves sampling, quantizing, and line coding.
· The Nyquist theorem says that the sampling rate must be at least twice the highest-frequency component in the original signal.
· Digital transmission can be either parallel or serial in mode.
· In parallel transmission, a group of bits is sent simultaneously, with each bit on a separate line.
· In serial transmission, there is only one line and the bits are sent sequentially.
· Serial transmission can be either synchronous or asynchronous.
· In asynchronous serial transmission, each byte (group of 8 bits) is framed with a start bit and a stop bit. There may be a variable-length gap between each byte.
· In synchronous serial transmission, bits are sent in a continuous stream without start and stop bits and without gaps between bytes. Regrouping the bits into meaningful bytes is the responsibility of the receiver.
Analog Transmission
· * Digital-to-analog modulation can be accomplished using the following: *Amplitude shift keying (ASK)—the amplitude of the carrier signal varies. *Frequency shift keying (FSK)—the frequency of the carrier signal varies. *Phase shift keying (PSK)—the phase of the carrier signal varies. *Quadrature amplitude modulation (QAM)—both the phase and amplitude of the carrier signal vary.
· QAM enables a higher data transmission rate than other digital-to-analog methods.
· Baud rate and bit rate are not synonymous. Bit rate is the number of bits transmit-ted per second. Baud rate is the number of signal units transmitted per second. One signal unit can represent one or more bits.
· The minimum required bandwidth for ASK and PSK is the baud rate.
· The minimum required bandwidth (BW) for FSK modulation is BW =f c1 .f c0 + N baud , where f c1 is the frequency representing a 1 bit, f c0 is the frequency representing a 0 bit, and N baud is the baud rate.
· A regular telephone line uses frequencies between 600 and 3000 Hz for data communication.
· ASK modulation is especially susceptible to noise.
· Because it uses two carrier frequencies, FSK modulation requires more bandwidth than ASK and PSK.
· * PSK and QAM modulation have two advantages over ASK: *They are not as susceptible to noise. *Each signal change can represent more than one bit.
· Trellis coding is a technique that uses redundancy to provide a lower error rate.
· The 56K modems are asymmetric; they download at a rate of 56 Kbps and upload at 33.6 Kbps.
· * Analog-to-analog modulation can be implemented by using the following: * Amplitude modulation (AM) * Frequency modulation (FM) * Phase modulation (PM)
· In AM radio, the bandwidth of the modulated signal must be twice the bandwith of the modulating signal.
· In FM radio, the bandwith of the modulated signal must be 10 times the bandwidth of the modulating signal.
Wired LANs: Ethernet Medium access methods can be categorized as random, controlled, or canalized.
· In the carrier sense multiple-access (CSMA) method, a station must listen to the medium prior to sending data onto the line.
· A persistence strategy defines the procedure to follow when a station senses an occupied medium.
· Carrier sense multiple access with collision detection (CSMA/CD) is CSMA with a postcollision procedure.
· Carrier sense multiple access with collision avoidance (CSMA/CA) is CSMA with procedures that avoid a collision.
· Reservation, polling, and token passing are controlled-access methods.
· In the reservation access method, a station reserves a slot for data by setting its flag in a reservation frame.
· In the polling access method, a primary station controls transmissions to and from secondary stations.
· In the token-passing access method, a station that has control of a frame called a token can send data.
· Channelization is a multiple-access method in which the available bandwidth of a link is shared in time, frequency, or through code, between stations on a network.
· FDMA, TDMA, and CDMA are channelization methods.
· In FDMA, the bandwith is divided into bands; each band is reserved fro the use of a specific station.
· In TDMA, the bandwidth is not divided into bands; instead the bandwidth is timeshared.
· In CDMA, the bandwidth is not divided into bands, yet data from all inputs are transmitted simultaneously.
· CDMA is based on coding theory and uses sequences of numbers called chips. The sequences are generated using Walsh tables.
Wireless LANs
Ethernet is the most widely used local area network protocol.
· The IEEE 802.3 standard defines 1-persistent CSMA/CD as the access method for first-generation 10-Mbps Ethernet.
· The data link layer of Ethernet consists of the LLC sublayer and the MAC sublayer.
· The MAC sublayer is responsible for the operation of the CSMA/CD access method.
· Each station on an Ethernet network has a unique 48-bit address imprinted on its network interface card (NIC).
· The minimum frame length for 10-Mbps Ethernet is 64 bytes; the maximum is 1518 bytes.
· The physical layer of 10-Mbps Ethernet can be composed of four sublayers: the physical layer signaling (PLS) sublayer, the attachment unit interface (AUI) sublayer, the medium attachment unit (MAU) sublayer, and the medium-dependent interface (MDI) sublayer.
· The common baseband implementations of 10-Mbps Ethernet are 10Base5 (thick Ethernet), 10Base2 (thin Ethernet), 10Base-T (twisted-pair Ethernet), and 10Base-FL (fiber link Ethernet).
· The 10Base5 implementation of Ethernet uses thick coaxial cable. The 10Base2 implementation of Ethernet uses thin coaxial cable. The 10Base-T implementation of Ethernet uses twisted-pair cable that connects each station to a port in a hub. The 10Base-FL implementation of Ethernet uses fiber-optic cable.
· A bridge can raise the bandwidth and separate the collision domains on an Ethernet LAN.
· A switch allows each station on an Ethernet LAN to have the entire capacity of the network to itself.
· Full-duplex mode doubles the capacity of each domain and deletes the need for the CSMA/CD method.
· Fast Ethernet has a data rate of 100 Mbps.
· In Fast Ethernet, autonegotiation allows two devices to negotiate the mode or data rate of operation.
· The Fast Ethernet reconciliation sublayer is responsible for the passing of data in 4-bit format to the MII.
· The Fast Ethernet MII is an interface that can be used with both a 10- and a 100-Mbps interface.
· The Fast Ethernet PHY sublayer is responsible for encoding and decoding.
· The common Fast Ethernet implementations are 100Base-TX (two pairs of twisted-pair cable), 100Base-FX (two fiber-optic cables), and 100Base-T4 (four pairs of voice-grade, or higher, twisted-pair cable).
· Gigabit Ethernet has a data rate of 1000 Mbps.
· Gigabit Ethernet access methods include half-duplex using traditional CSMA/CD (not common) and full-duplex (most popular method).
· The Gigabit Ethernet reconciliation sublayer is responsible for sending 8-bit parallel data to the PHY sublayer via a GMII interface.
· The Gigabit Ethernet GMII defines how the reconciliation sublayer is to be connected to the PHY sublayer.
· The Gigabit Ethernet PHY sublayer is responsible for encoding and decoding.
· The common Gigabit Ethernet implementations are 1000Base-SX (two optical fibers and a shortwave laser source), 100Base-LX (two optical fibers and a long-wave laser source), and 100Base-T (four twisted pairs).
Network Layer: Internet Protocol
· The Address Resolution Protocol (ARP) is a dynamic mapping method that finds a physical address, given an IP address.
· An ARP request is broadcast to all devices on the network.
· An ARP reply is unicast to the host requesting the mapping.
· IP is an unreliable connectionless protocol responsible for source-to-destination delivery.
· Packets in the IP layer are called datagrams.
· A datagram consists of a header (20 to 60 bytes) and data.
· The MTU is the maximum number of bytes that a data link protocol can excapsulate. MTUs vary from protocol to protocol.
· Fragmentation is the division of a datagram into smaller units to accommodate the MTU of a data link protocol.
· The fields in the IP header that relate to fragmentation are the identification number, the fragmentation flags, and the fragmentation offset.
· The Internet Control Message Protocol (ICMP) sends five types of error-reporting messages and four pairs of query messages to support the unreliable and connectionless Internet Protocol (IP).
· ICMP messages are encapsulated in IP datagrams.
· The destination-unreachable error message is sent to the source host when a datagram is undeliverable.
· The source-quench error message is sent in an effort to alleviate congestion.
· The time-exceeded message notifies a source host that (1) the time-to-live field has reached zero or (2) fragments of a message have not arrived in a set amount of time.
· The parameter-problem message notifies a host that there is a problem in the header field of a datagram.
· The redirection message is sent to make the routing table of a host more effective.
· The echo-request and echo-reply messages test the connectivity between two systems.
· The time-stamp-request and time-stamp-reply messages can determine the roundtrip time between two systems or the difference in time between two systems.
· The address-mask request and address-mask reply messages are used to obtain the subnet mask.
· The router-solicitation and router-advertisement messages allow hosts to update their routing tables.
· IPv6, the latest verstion of the Internet Protocol, has a 128-bit address space, a resource allocation, and increased security measures.
· IPv6 uses hexadecimal colon notation with abbreviation methods available.
· Three strategies used to make the transition from version 4 to version 6 are dual stack, tunneling, and header translation.
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