Frequency: it refers to the number of periods in 1 s. It is formally expressed in Hertz (Hz)

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1 Chapter2: Peak amplitude: it is the absolute value of the highest intensity. Frequency: it refers to the number of periods in 1 s. It is formally expressed in Hertz (Hz) Phase: it describes the position of the waveform relative to time 0. It is measured in degree or radian. Period: is the amount of time, in seconds, a signal needs to complete one cycle (the completion of one full pattern) The bandwidth of a composite signal: is the difference between the highest and the lowest frequencies contained in that signal Nyquist Theorem: A data signal on a medium with H (Hz) bandwidth can be reconstructed by making 2H samples/ sec Shannon s Theorem The maximum throughput of a noisy channel of bandwidth H with a signal to noisy ratio of S/N full-duplex links: Links that can be used in both directions at the same time half-duplex links : Links that can be used in either direction, but only one way at a time Fiber optics: are used for long-haul transmission in network backbones, high speed LANs, and high-speed Internet access. Multimode Fiber: any light ray incident on the boundary above the critical angle will be reflected internally, many different rays will be bouncing around at different angles. Single-mode Fiber: light can propagate only in a straight line, without bouncing Three wavelength bands: they are centered at 0.85, 1.30, and 1.55 microns, respectively. All three bands are 25,000 to 30,000 GHz wide.

2 Baseband transmission: the signal occupies frequencies from zero up to a maximum that depends on the signaling rate. It is common for wires. Passband transmission: the signal occupies a band of frequencies around the frequency of the carrier signal. It is common for wireless and optical channels. Multiplexing: Channels are often shared by multiple signals. NRZ: a positive voltage to represent a 1 and a negative voltage to represent a 0 Manchester: mix the clock signal with the data signal by XORing them together. NRZI: coding a 1 as a transition and a 0 as no transition, or vice versa. 4B/5B: Every 4 bits is mapped into a5-bit pattern with a fixed translation table. The five bit patterns are chosen so that there will never be a run of more than three consecutive 0s Bipolar encoding: represent a logical 1, (say +1 V or 1 V) with 0 V representing a logical zero. To send a 1, the transmitter alternates between the +1 V and 1 V levels Digital modulation: is accomplished with passband transmission by regulating or modulating a carrier signal that sits in the passband. ASK (Amplitude Shift Keying): two different amplitudes are used to represent 0 and 1. PSK (Phase Shift Keying): the carrier wave is systematically shifted 0 or 180 degrees at each symbol period. FDM: divides the spectrum into frequency bands, with each user having exclusive possession of some band. Guard band: It keeps the channels well separated OFDM (Orthogonal Frequency Division Multiplexing): the channel bandwidth is divided into many subcarriers that independently send data

3 CDM (Code Division Multiplexing): is a form of spread spectrum communication. Chapter3: Physical Addresses: It is known as link address, It is the address of a node as defined by its LAN NIC (Network Interface Card): The physical layer process and some of the data link layer process run on dedicate hardware. Framing: The data link layer needs to pack bits into frames, so that each frame is distinguishable from another flag byte: are two consecutive flag bytes indicate the end of one frame and the start of the next. its inserted as both the starting and ending delimiter. byte stuffing: the escape bytes before giving the data to the network layer. feedback-based flow control: the receiver sends back information to the sender giving it permission to send more data, or at least telling the sender how the receiver is doing. rate-based flow control: the protocol has a built-in mechanism that limits the rate at which senders may transmit data, without using feedback from the receiver. Selective RepeatARQ: another mechanism that does not resend N frames when just one frame is damaged; only the damaged frame is resent. *للمراجعه فقط مهمه عشان نفهم تشابتر ٣ افهمو تعاريف الليرز وال هي محذوفه* Chapter4: Application Layer (OSI): Provides access to the OSI environment for users. Presentation Layer(OSI): Provides independence to the application processes from differences in data representation (syntax) Session Layer (OSI): Provides the control structure for communication between applications; establishes, manages, and terminates connections (sessions) between cooperating applications Transport Layer (OSI):

4 Provides reliable, transfer of data between end points Network Layer (OSI): Provides connections between hosts on different networks Data Link Layer (OSI): Provides for the reliable transfer of information across the physical link; sends blocks (frames) with the necessary synchronization, error control, and flow control. Physical Layer (OSI): Concerned with transmission of unstructured bit stream over physical medium protocol suite: is consists of a large collection of protocols that have been issued as Internet standards by the Internet Activities Board (IAB). physical layer (TCP/IP): The physical layer covers the physical interface between a data transmission device (e.g., workstation, computer) and a transmission medium or network. bit: is a logical unit between two physical layers in two devices. Data Link Layer (TCP/IP): The data link layer is concerned with the exchange of data between an end system (server, workstation, etc.) and the network to which it is attached Transport/Host to Host Layer: There is usually a requirement that data be exchanged reliably. That is, assured that all of the data arrive at the destination application and that the data arrive in the same order in which they were sent end-to-end: The logical connection between two transport layers, two application layers and two network layers Hypertext Transfer Protocol (HTTP): Accessing the World Wide Web The Simple Mail Transfer Protocol (SMTP): is the main protocol used in electronic mail ( ) service. The File Transfer Protocol (FTP): is used for transferring files from one host to another. The Internet Protocol (IP): is a connectionless protocol that provides no flow control, no error control, and no congestion control services it is used at network layer to provide the routing function across multiple networks

5 Transmission Control Protocol (TCP): is a connection-oriented protocol that first establishes a logical connection between transport layers at two hosts before transferring data. User Datagram Protocol (UDP): is a connectionless protocol that transmits user datagrams without first creating a logical connection. Transport layer address: addresses are called port numbers, and these define the application-layer programs at the source and destination. Port numbers are local addresses that distinguish between several programs running at the same time. Network-layer address: the addresses are global,with the whole Internet as the scope. A network-layer address uniquely defines the connection of a device to the Internet. Link-layer address: sometimes called MAC addresses,are locally defined addresses, each of which defines a specific host or router in a network (LAN or WAN). Chapter5: Network layer: is responsible for host to host delivery and for routing the packets through the routers. Two-Level Hierarchy: No Subnetting: An IP address can define only two levels of hierarchy when not subnetted. The n leftmost bits of the address x.y.z.t/n define the network prefix: The part of the address that defines the network suffix: the part that defines the host datagrams: Packets in the IPv4 layer forwarding: is the sending of packets along a path sink tree: Each portion of a best path is also a best path and the union of them to a router is a tree Flooding:

6 A simple method to send a packet to all network nodes. Each node floods a new packet received on an incoming link by sending it out all of the other links Chapter6: transport layer: is responsible for process-to-process delivery process: is an application program running on a host client: A process on the local host server: needs services from a process usually on the remote host well-known port numbers: universal port numbers for servers socket address: The combination of an IP address and a port number Pushing: sender delivers items whenever they are produced, without a prior request from the consumer. Pulling: producer delivers the items after the consumer has requested them UDP (User data gram protocol): Unreliable connectionless transport-layer protocol used for its simplicity and efficiency in applications where error control can be provided by the application-layer process TCP (Transmission Control protocol): Reliable connection-oriented protocol that can be used in any application where reliability is important, it explicitly defines connection establishment, data transfer, and connection teardown phases to provide connection oriented service SCTP: Combines the features of TCP and UDP. user datagrams: are UDP packets segment: A packet in TCP

7 Header: The segment consists of a header of 20 to 60 bytes, followed by data from the application program. Source port address: This is a 16-bit field that defines the port number of the application program in the host that is sending the segment. Destination port address: This is a 16-bit field that defines the port number of the application program in the host that is receiving the segment. Sequence number: This 32-bit field defines the number assigned to the first byte of data contained in this segment. Acknowledgment number: This 32-bit field defines the byte number that the receiver of the segment is expecting to receive from the other party. Header length: This 4-bit field indicates the number of 4-byte words in the TCP header. Window size: This field defines the window size of the sending TCP in bytes Urgent pointer: This 16-bit field, which is valid only if the urgent flag is set, is used when the segment contains urgent data Slow Start Algorithm: The congestion window is doubling every round trip time Congestion Avoidance Algorithm: an algorithm that increases the cwnd additively instead of exponentially.