Periodic signal n A signal is periodic if

Periodic signal n A signal is periodic if and only if s(t + T) = s(t) for all values of t n T is the period of the signal.

Analog signal n An analog signal is a continuously varying electromagnetic wave that may be propagated over a variety of media, depending on spectrum.

Digital signal n A digital signal is a sequence of voltage pulses that may be transmitted over a wire medium.

Characteristics of a periodic signal n Amplitude n n Frequency n n instantaneous value of a signal at any time. the inverse of the period (1/T), or the number of repetition of the period per second; it is expressed in cycles per second, or hertz (Hz). Phase n measure of the relative position in time within a single period of a signal.

Spectrum and bandwidth n Spectrum of a signal is the range of frequencies that it contains. n Bandwidth of a signal is the width of the spectrum in which most of the energy in the signal is contained.

Transmission Data transmission occurs between transmitter and receiver over some transmission medium. n Transmission media may be classified as guided or unguided. n

Guided media n With guided media, the wave are guided along a physical path; example of guided media are: n twisted pair n coaxial cable n optical fiber

Unguided media n Unguided media provide a means for transmitting electromagnetic waves but do not guide them; examples are propagation through: n air n vacuum n seawater

Direct link n The term direct link is used to refer to the transmission path between two devices in which signals propagate directly from transmitter to receiver with no intermediate devices, other than amplifier or repeaters used to increase signal strength.

Point-to-Point n A guided transmission medium is point-topoint if it provides a direct link between two devices and those are the only two devices sharing the medium.

Point-to-Point Transmitter/ receiver Medium Amplifier or repeater 0 or more Transmitter/ receiver Medium

Multipoint n In a multipoint guided configuration, more than two devices share the same medium.

Multipoint Transmitter/ …. Transmitter/ receiver Medium Transmitter/ receiver Amplifier or repeater Transmitter/ receiver Medium 0 or more

Simplex transmission n In simplex transmission, signals are transmitted in only one direction; one station is transmitter and the other is receiver.

Half-duplex transmission n In half-duplex transmission, both station may transmit, but only one at a time.

Full-duplex transmission n In full-duplex transmission, both station may transmit simultaneously. In this case the medium is carrying signals in both direction.

Telecommunication Devices Modems n Fax modems n Special purpose modems n Multiplexers n TDM n FDM n n Communication processors

Telecommunication Carriers & Services n Common carriers AT&T n MCI n Sprint n n Value added carriers Telnet n Sprint. Net n

Switched Lines n Switched line is a standard telephone line that uses switching equipment to allow one transmission device to be connected to other transmission devices.

Dedicated Line n Dedicated line is a line that provides a constant connection between two points.

Private Branch Exchange PBX is a communications system that can manage both voice and data transfer within a building and to outside lines. n PBX can store calls n PBX can transfer calls n PBX can serve as a connection between different office devices n

Wide Area Telecommunication Service n WATs is a billing method for heavy users of voice band media.

Integrated Services Digital Network n ISDN is a technology that uses existing common carrier lines to simultaneously transmit voice, video, and image data in digital form.

Network Topology Ring n Bus n Star n Hybrid n Hierarchical n

Type of Networks LAN n WAN n

Communication Protocol Open System Interconnection (OSI) n Transmission Control Protocol/Internet Protocol (TCP/IP) n System Network Architecture (SNA) n Ethernet n X. 400 n X. 500 n

SOI n Physical layer n n Data link layer n n transmits the data from one node to another. format the data into a record called a frame and performs error detection. Network layer n causes the physical layer to transfer the frames from node to node.

OSI n Transport layer n n Session layer n n enable the user and host nodes to communicate with each other. initiate, maintains, and each session. Presentation layer n formats the data so that it can be presented to the user or the host.

OSI n Application layer n controls user input from the terminal and executes the user’s application program in the host computer.

Data Transfer Modes Packet switching n Frame relay n Voice over frame relay n Asynchronous transfer mode (ATM) n

Internet The internet is the world’s largest computer network. n It is a collection of interconnected networks, all freely exchanging information. n

Internet Protocol n The set of conventions used to pass packets from one host to another is known as the internet protocol (IP) n TCP (transport control protocol is widely used.

Ways to connect to internet LAN n SLIP ( serial line internet protocol) or PPP (point to point protocol) n On-line service n

World Wide Web (www) n WWW is a collection of over 30, 000 independently owned computer that together as one in an internet service.

Web Browser n Web browser creates a unique, hypermedia based menu on your computer screen that provide a graphical interface to the Web.

Hypermedia Connects the data on pages, allowing users to access topics in whatever order they wish. n Allows you to bring up pictures, graphs and other displays with sound and motion. n

Web Search Engine Web search engines take the place of the card catalog. n They are software programs that allow you to search for information on the Web. n

Intranet n An intranet is an internal corporate network built using internet and Web standards.

Cryptography n Cryptography is the process of converting a message into a secret code and changing the encoded message back to regular text. (digital signature)

Firewalls The most popular method of preventing unauthorized access to corporate computer data to construct is known as a firewall. n Firewalls can be a set of filtering rules or specially configured hardware. n

Zone edu = educational sites n mil = military n gov = government n net = networking organizations n nom = individuals n org = organization n com = commercial n

Telnet and FTP n Logon to another computer and access its public files. n Copy a file from another computer to your computer.

E-mail (store and forward) n To send text, binary files, sound, and images to others.

Amplitude Shift Keying (ASK) n To encode binary data by varying the amplitude of signal.

Frequency Shift Keying (FSK) n To encode binary data by varying the frequency of signal.

Phase Shift Keying (PSK) n To encode binary data by transition or shift from one phase to another.

Bit Synchronization Coordination of signal measurement timing is called bit synchronization. n There are two methods of bit synchronization: n Asynchronous n Synchronous n

Asynchronous Bit Synchronization Massages begin with a start bit so that the receiving device can synchronize its internal clock with the timing of the massage. n Asynchronous transmissions are normally short, and the end of message is signaled by a stop bit. n Media is idle and the sender’s and receiver’s clocks are not synchronized when no data is being transmitted. n

Synchronous Bit Synchronization n Clocks of the sender and receiver are synchronized by one of the following methods: guaranteed state change n separate clock signal n oversampling n

Baseband & Broadband Transmissions Baseband: these transmission use the entire media bandwidth for a single channel. Most LAN use baseband signaling. n Broadband: these transmission provide the ability to divide the entire media bandwidth into multiple channels. n

Selecting NIC n Type of network n n Type of media n n Token Ring, Ethernet, ATM, …etc coaxial cable, STP, UTP, fiber, …etc Type of bus n ISA, EISA, VESA, …etc

Bus Architectures n ISA (Industry Standard Architecture) n n PCI (Peripheral Computer Interconnect) n n 8 bit and 16 bit bus (10 MHz) 32 bit or 64 bit bus EISA (Extended Industry Standard Architecture) n 32 bit bus built on the ISA architecture (33 MHz)

Bus Architectures n MCA (Micro Channel Architecture) n 32 bit bus. MCA can work in 16 or 32 bit mode. (66 MHz)

Memory Requirement n Minimum RAM recommended for Windows NT Server is 16 MB.

Memory Allocation Operating system. n Services. n Processes. n Programs. n CPU functions. n

Estimating Memory Requirement Minimum amount needed for Server operating system (16 MB) plus n Number of people who will be accessing the system at the same time plus n Average software requests per user. n

Hard Disk Capacity Operating system files. n Software files. n Data and database files. n User files. n General public files. n Utility files. n Server management files. n

Fault Tolerance n Fault -tolerance options disk mirroring n disk duplexing n redundant array of inexpensive disks (RAID) n n there are eight levels of RAID.

Disk Mirroring Secondary drive Controller server Primary drive

Disk Duplexing Secondary drive server Controller Primary drive

Project n Set up a NIC in windows NT Server, once the NIC operating system are installed. Click Start button n select Settings n select Control Panel n double click Network icon n click Adapters tab n click Add button n

Project n Notice the list of adapters that can be install click Cancel n close the control Panel n

Windows NT networking Models Workgroup. n Client-server. n Domain. n

Windows NT networking Models n Workgroup model is a decentralized networking model. All account administration is local to each machine. n Each machine maintains its own account database n

Windows NT networking Models n Client-server model is a centralized networking model. All administration is centralized at server. n Clients can log on to a server via the server’s account database and access resources associated with that server. n

Windows NT networking Models n NT domain model Allows administrators to group users. n All administration is centralized to an NT Server that has been designated as he primary domain controller (PDC). n

Windows NT networking Models In NT domain model the account database that resides on the PDC is called Security Account Manager (SAM) n SAM database is copied to server that has been designated as Backup Domain Controllers (BDC) n Each domain need al least one server n

Windows NT networking Models PDC contains the master copy of SAM for the entire domain and is the only server that can make changes to the database. n If there is more than one server in a domain, selected servers can be designated to keep a backup copy of the SAM. n PDC’s SAM database is read-write. n

Windows NT networking Models n Domain models: single domain n single master domain n multiple master domain n complete trust domain n

Windows NT networking Models n Criteria for choosing Domain models: # of accounts (windows NT can support up to 40, 000 account). n The geographic scope of your domain. n How users ant resources will be defined within the domain. n

Domain Trust Relationship In situation where there are two or more domains, users can access domains other than their own through trust relationships set up by the network administrator. n Each trust relationship has two parties: n n trusted domain n granted access to resources n trusting domain n granting the access

Example n A n organization has a main office and ten branches, each with its own file server and domain. Main office domain needs access to all branches, which is granted. Main office is trusted domain, and branches are the trusting domains

Trust Relationships n One-way trust n n Two-way trust n n the trust relationship is not reciprocated. One domain is trusted party, and the other is trusting the trust relationship is reciprocated. Universal trust n two-way trust are set up among more than two domain.

Single Domain Consists of a single domain. n Easy to manage. n Centralized administration. n Good for small networks. n Slow when supporting large # of accounts. n

Single Domain BDC PDC User Accounts and resources

Single Master Domain Several domain are controlled by master domain. n All account are in the master domain. n Other domains containing only resources, such as servers. n

Single Master Domain All resources are located at resource domains and can be available to all users. n Resources are decentralized. n Administrators in the resource domain have control over their resources. n All user account are centralized in a master domain. n

Single Master Domain Master domain Resource domain

Multiple Master Domain Consists of multiple single master domain connected through two-way trust relationships. n Administration can be centralized or decentralized. n

Multiple Master Domain Number of trusts (n) can be determined as follow: n=M(M-1)+(R+M) M=# of master or accounts domains R=# of resource domains n

Multiple Master Domain Master domain Resource domain

Complete Trust Domain Accounts and resources are located in each domain. n Allows decentralized account management. n Each account can implement policies specific to their domain. n N(N-1)=n n n where N represents # of domain

Complete Trust Domain Account resources