Module 2: Understanding Local Area Networks 1.5 Understand network topologies and access methods

Agenda 1 Network Topologies 2 Ethernet Standards 3 Peer to Peer vs. Client/Server Models

Network Topologies

What is a network topology? A network topology defines the physical connections of hosts in a network There are multiple types of topologies, including: Bus Star Ring Mesh

Bus Topology All devices are connected via copper cable in a line

Star Topology Each host is connected to a central connecting device with twisted-pair cabling The central connecting device can be a hub, a switch, or a SOHO router This is the most commonly used topology NOTE: two star topologies can be connected via their central connecting devices to form a star- bus topology

Ring Topology Each device is connected to the LAN using a closed loop NOTE: Each device is connected to two other devices

Mesh Topology Each computer connects to every other computer in a LAN No central connecting device Setup is fault-tolerant allows data to be sent via multiple pathways if one path fails

Ethernet Standards

What is Ethernet? A standard that defines how data is sent and received between devices Most widely used standard on the Internet today Token Ring and FDDI are used when Ethernet is not Standardized by the Institute of Electrical and Electronics Engineers (IEEE) as 802.3

What are frames? Devices on Ethernet networks transmit frames Sequence of bits containing a detectable beginning and end of a packet in the stream of bits Include physical address information that helps switches determine where to send data beginning address info data end

IEEE 802.3 802.3 Version Data Transfer Rate Cable Standard Cabling Used 802.3 10 Mbps 10BASE5 Thick coaxial 802.3a 10BASE2 Thin coaxial 802.3i 10BASE-T Twisted pair (TP) 802.3j 10BASE-F Fiber optic 802.3u 100 Mbps 10BASE-TX 100BASE-T4 100BASE-FX TP using 2 pairs TP using 4 pairs 802.3ab 1000 Mbps or 1 Gbps 1000BASE-T Twisted pair 802.3z 1000BASE-X 802.3ae 10 Gbps 10GBASE-SR, 10GBASE-LR, 10GBASE-ER, and so on 802.3an 10GBASE-T

IEEE 802.3 Defines carrier sense multiple access with collision detection (CSMA/CD) Devices share a connection If they send data at the same time, collisions occur So, only one computer can transmit at a time CSMA/CD allows devices to send/receive data by limiting collisions

CSMA/CD Process Assemble a frame Check if the medium is free If free, transmit a bit of the frame If not, don’t transmit and repeat step 2 Check if a collision was detected If so, implement the collision detected procedure If not, transmit the remaining bits in the frame

What is the collision detected procedure? If a collision is detected, then a network adapter will perform the following steps: Send out a jam signal to stop all communication on the medium Wait based on the number of collisions detected Starts sending the remaining bits of the frame

Peer to Peer vs. Client/Server Models

The Client/Server Model Servers are computers dedicated to providing specific types of services or data A client (a computer) uses software to ask a server for data or services The server provides the data or service to the client Hey! Can you please send me an HTML file? Server Client

Types of Servers SERVER TYPE FUNCTION(S) File server Store files, software, or data for access by computers on a network. Print server Allows computers that are connected to a network to control printers on the network. Database server Houses a relational database made up of multiple files. Network controller Controls accounts that are domain, as well as the devices that belong to a network. Messaging server Provide services related to email, fax, instant messaging and collaboration. Web server Provides access to HTML documents for computers on a network. CTI-based server Responsible for Computer Telephony Integration, which integrates a network’s telephone and computer systems.

Client and Server Operating Systems To ensure functionality of both clients and servers, operating systems are used Client Operating Systems Server Operating Systems Windows 7 Windows Server 2008 Windows Vista Windows XP Windows Server 2003 Windows 2000 Professional Windows 2000 Server Windows NT 4.0 Workstation Windows ME/98/95 Windows NT 4.0 Server

The Peer-to-Peer Model Peers are clients that have equal capabilities and responsibilities in this model Ability to serve and request data No server in this model Examples of file sharing networks Napster Gnutella G2 Other technologies also take advantage of P2P file sharing: Skype VoIP Cloud computing Peer

Summary 1 Network Topologies 2 Ethernet Standards 3 Peer to Peer vs. Client/Server Models