LAN Dr. Yan Quan Liu ILS SCSU Unit 10 LAN Dr. Yan Quan Liu ILS SCSU

What is LAN (local area network)? A group of computers dispersed over a local area and connected by a communications link that enables any device to interact with any other on the network. 4/21/2017 ILS 501 / Dr. Liu, SCSU

Types: Client-server LAN Peer-to-peer LAN 4/21/2017 ILS 501 / Dr. Liu, SCSU

Types of LANs Client/server LAN - Clients - microcomputers that request data Server - a powerful microcomputer that supplies data and manages shared devices File server - a computer that acts like a disk drive, storing the programs and data files shared by users on a LAN. Database server - a computer in a LAN that stores data but does not store programs. Print server - controls one or more printers and stores the print-image output from all the microcomputers on the system. Web server - contains web pages that can be viewed using a browser. Mail server - manages e-mail. 4/21/2017 ILS 501 / Dr. Liu, SCSU

Types of LANs Peer-to-peer LAN - all microcomputers on the network communicate directly with one another without relying on a server Peer-to-peer networks are cheaper than client/server networks, but only work effectively for up to 25 computers. 4/21/2017 ILS 501 / Dr. Liu, SCSU

Components of LANs Connection or cabling system Microcomputers with network interface cards Network OS Other shared devices Routers, bridges, and gateways Hub Router - a special computer that directs communicating messages when several networks are connected together. Bridge - an interface used to connect the same types of networks. Gateway - an interface permitting communication between dissimilar networks. Hub – a common connection point for devices in a network. 4/21/2017 ILS 501 / Dr. Liu, SCSU

Wireless local area networks (WLANs) A wireless LAN (or WLAN, for wireless local area network, sometimes referred to as LAWN, for local area wireless network) is one in which a mobile user can connect to a local area network (LAN) through a wireless (radio) connection 4/21/2017 ILS 501 / Dr. Liu, SCSU

802.11 tech for WLANs 802.11 is an evolving family of specifications for wireless local area networks (WLANs) developed by a working group of the Institute of Electrical and Electronics Engineers (IEEE). There are several specifications in the family and new ones are occasionally added. 4/21/2017 ILS 501 / Dr. Liu, SCSU

802.11 tech for WLANs 802.11g 30 MB/s 802.11n 300 MB/s 802 Standard comprises a family of networking standards that cover the physical layer specifications of technologies from Ethernet to wireless 4/21/2017 ILS 501 / Dr. Liu, SCSU

Access Point "In a wireless local area network ( WLAN ), an access point is a station that transmits and receives data (sometimes referred to as a transceiver). An access point connects users to other users within the network and ..." 4/21/2017 ILS 501 / Dr. Liu, SCSU

What are common network interface devices? 4/21/2017 ILS 501 / Dr. Liu, SCSU

Local area network technology- Network interface devices Common interface drivers/receivers connecting networks are: Bridge Router Gateway Firewall 4/21/2017 ILS 501 / Dr. Liu, SCSU

Network interface devices— Bridge A bridge is a product that connects a local area network to another local area network that uses the same protocol (for example, Ethernet) 4/21/2017 ILS 501 / Dr. Liu, SCSU

Network interface devices— Router A router is a device or software in a computer, that determines the next network point to which a packet should be forwarded toward its destination. The router is connected to networks with different operating systems. 4/21/2017 ILS 501 / Dr. Liu, SCSU

Network interface devices— Gateway A gateway is a network point that acts as an entrance to another network. It performs all functions of bridges and routers but slower in terms of speed than those two. 4/21/2017 ILS 501 / Dr. Liu, SCSU

Network interface devices— Firewall A firewall is a set of related programs, located at a network gateway server, that protects the resources of a private network from all unauthorized users from other networks. 4/21/2017 ILS 501 / Dr. Liu, SCSU

Ending notes: Essential Questions What does telecommunication mean? How is connection made to a network? What are the types and components of communication channels? What does the future hold in relation to telecommunications? 4/21/2017 ILS 501 / Dr. Liu, SCSU

Local area network devices- Topology & Topography A topology (from Greek topos: place) is a description of any kind of locality in terms of its physical layout. (See page 7.31-32 diagrams) Topography is the configuration and arrangement in physical locations of actual communication and information system components, which implement the topology. 4/21/2017 ILS 501 / Dr. Liu, SCSU

Local area network devices- Common topologies Star topographies/network Ring topographies/network Bus topographies/network Hybrid topographies/network FDDI (Fiber Distributed Data Interface) See textbook for details 4/21/2017 ILS 501 / Dr. Liu, SCSU

Local area network devices- Star network A network topology in which terminals are connected to a central server, which rebroadcasts all transmissions received from any peripheral node to all peripheral nodes on the network, including the server (originating node) See textbook 7.31 for details 4/21/2017 ILS 501 / Dr. Liu, SCSU

Local area network devices- Ring network A ring is a network topology in which each device is attached along the same signal path to two other devices, forming a path in the shape of a ring. Each device in the ring has a unique address. See textbook7.31 for details 4/21/2017 ILS 501 / Dr. Liu, SCSU

Local area network devices- Bus network A bus is a transmission path on which signals are dropped off or picked up at every device attached to the line. Only devices addressed by the signals pay attention to them; the others discard the signals. See textbook 7.32 for details 4/21/2017 ILS 501 / Dr. Liu, SCSU

Topology of LANs Bus network – all nodes are connected to a single wire or cable, the bus, which has two endpoints Each communication device on the network transmits electronic messages to other devices. Topology - the logical layout, or shape, of a network. Advantage - May be organized as either a client/server or peer-to-peer network. Disadvantages - Extra circuitry and software are needed to avoid collisions between data; and Entire network may stop working if a connection in the bus is broken. 4/21/2017 ILS 501 / Dr. Liu, SCSU

Topology of LANs Ring network - all microcomputers and other communications devices are connected in a continuous loop A ring network does not have any endpoints. Advantage - No danger of collisions as messages flow in only one direction. Disadvantage - If a connection is broken, the entire network stops working. 4/21/2017 ILS 501 / Dr. Liu, SCSU

Quick Note on Network Setups Simple Network Dialup 56k Modem plugged into phone line (1 computer) Computer Phone Outlet Dialup Modem Note: Uses regular phone cable 4/21/2017 ILS 501 / Dr. Liu, SCSU

Quick Note on Network Setups Simple Cable/Satellite Modem Cable/DSL/Satellite Modem plugged into cable/DSL/satellite outlet (1 computer) Charter and SBC/Yahoo are broadband Internet services Computer Cable/ Satellite Outlet Cable/DSL/ Satellite Modem Note: Uses special Category 5 (Cat 5 RJ45) Cable called patchcords *Most network equipment has a speed of 100Mbit/s 4/21/2017 ILS 501 / Dr. Liu, SCSU

Quick Note on Network Setups Cable/DSL/Satellite with Hub Cable/DSL/Satellite Modem plugged into cable/DSL/satellite outlet Requires 2 or more Internet Protocol (IP) connections (like 2 separate phone numbers) Computer Cable/DSL Satellite Modem Cable/DSL Satellite Outlet Hub Computer 4/21/2017 ILS 501 / Dr. Liu, SCSU

Quick Note on Network Setups Cable/DSL/Satellite with Router/Switch Cable/DSL/Satellite Modem and Router/ Switch* plugged into cable/satellite outlet Requires only 1 Internet Protocol (IP) connection (shares a phone number-saves $$) Computer Cable/DSL Satellite Modem Cable/DSL Satellite Outlet Router/ Switch Computer *Switches are smarter and faster than hubs 4/21/2017 ILS 501 / Dr. Liu, SCSU

Quick Note on Network Setups Cable/Satellite with Wireless Router/Switch Cable/Satellite Modem and wireless Router/Switch plugged into cable/satellite outlet Requires wireless network cards. Wireless is more convenient but less secure than Cables Computer Cable/ Satellite Outlet Wireless Router/ Switch Cable/ Satellite Modem Computer 4/21/2017 ILS 501 / Dr. Liu, SCSU

Quick Note on Network Setups Firewalls Firewalls are like the firewall in your car, which keep the heat and noise of the engine outside the passenger compartment Computer Firewalls are used to keep unwanted Internet users from accessing your network Once online, you are vulnerable w/o a firewall BlackIce is an example of firewall software Firewall Router/ Switch & Firewall Cable/ Satellite Outlet Cable/ Satellite Modem Computer 4/21/2017 ILS 501 / Dr. Liu, SCSU

Quick Note on Networks Firewalls Computer Firewalls work like Caller ID You set up the rules of who can “call” you Unrecognized callers are either denied, or asked for a password NOTE: Some software, like PCAnywhere and SQL Server require the firewall to specially configured 4/21/2017 ILS 501 / Dr. Liu, SCSU

Questions? Thank You 4/21/2017 ILS 501 / Dr. Liu, SCSU