Computer Networks & Security Advantages of a network Client/server and peer-to-peer networks Classifications of client/server networks Client/server network components Types of servers Network topologies NEXT SLIDE

Topics Types of transmission media Network software Network adapters Moving data in a client/server network Securing networks NEXT SLIDE

Networking Advantages Networks: Increase productivity Enable the sharing of resources Facilitate Internet connectivity NEXT SLIDE

Client/Server Networks Server based network: Clients Servers Data flows efficiently Servers respond to requests from clients Servers perform specific tasks Scalable network NEXT SLIDE

Classifications of Client/Server Networks LAN: Local area network Computers linked together over a small geographic region WAN: Wide area network Computers linked together over large diverse geographic locations MAN: Metropolitan area network Computers linked together within a city or county NEXT SLIDE

Classifications of Client/Server Networks PAN: Personal area network Wireless devices connected in close proximity to each other Intranet: Private corporate network NEXT SLIDE

Constructing Client/Server Networks Servers Network topologies Transmission media Network operating system (NOS) Network adapters Network navigation devices

Servers Number and type of servers depend on network size and workload Dedicated server: Perform one specific function Authentication server: Keeps track of network logins and services available File server: Store and manage files

Dedicated Servers Print server: Applications server: Database server: Manages client-requested printing jobs Creates print queue (prioritizes print jobs) Applications server: Acts as a storage area for application software Database server: Provides clients with access to database information E-mail server: Process and deliver in-coming and outgoing e-mail

Dedicated Servers Communications server: Web server: Handles communications between networks including the Internet Web server: Hosts a Web site available through the Internet

Network Topologies The physical layout of computers, transmission media, and other components Types of network topologies include: Bus topology Ring topology Star topology

Bus Topology All nodes are connected in sequence on a single cable Used most often on peer-to-peer networks Networked computers communicate with each other One computer transmits data at a time: Access methods avoid data collisions Data is transmitted in “packets”

Ring Topology Nodes are laid out in a ring Token (data packet) flows in one direction from device to device

Star Topology Nodes connect to a central communications device (hub/switch) A node sends a signal to the hub which retransmits it to the other nodes A node accepts the signal addressed to it

Avoiding Data Collisions on a Star Network

Transmission Media The routes data takes to flow between devices on a network: Wired Wireless: Wireless Fidelity (Wi-Fi) Uses radio waves 802.11 standard

Choosing a Cable Maximum run length Bandwidth Bend radius Cable cost Installation costs Susceptibility to interference Signal transmission methods

Twisted Pair Cable Pairs of copper wire twisted around each other Twists make the wires less susceptible to interference Shielded twisted pair (STP) Layer of foil shielding Unshielded twisted pair (UTP) Cat 5E Bandwidth 1Gbps Cat 6 Bandwidth 200 Mbps

Coaxial Cable Four components: Copper core Nonconductive insulating material Braided metal Plastic cover

Fiber-Optic Cable Components include: Glass or plastic fibers Cladding Outer jacket Uses light impulses to transmit data Immune to interference

Network Operating Systems (NOS) Provide the protocol that controls the communication between devices on the network Major network operating systems: Windows Server 2003 UNIX Novell NetWare

Network Adapters Devices that enable computers to communicate on a network Network interface cards (NICs): Generate network transmission signals Create data packets Act as information gatekeepers Ethernet compliant Wireless NICs

Network Navigation Devices Media Access Control (MAC) address: Six 2-digit numbers (01:40:87:44:79:A5) Physical address of network adapter Internal network identification Repeaters and Hubs: Amplify signals and retransmit them Switches and Bridges: Send data on a specific route through the network Bridges send data between collision domains Routers: Send information between two networks

Network Security Authentication: Access privileges: User ID and password used to access the network Access privileges: Enable access to certain network systems Physical protection measures: Restrict physical access to sensitive network equipment Magnetic card readers Biometric access devices NEXT SLIDE

Network Security Firewalls: Prevent access to the network by unauthorized users Composed of software and/or hardware Screens and validates data packets Bastion host/proxy server NEXT SLIDE

Network Firewall Layout Perimeter Network Internal Network External Screening Router Bastion Host /Proxy Server Internal Screening Router