CIS 173 Networking Essentials Week #3 Objectives Review Chapter #1 Questions Lecture Chapter #2 (Topologies)

Chapter #2 Design Essentials Network Topologies

Network Design Analyze Network Req’ts –ASK QUESTIONS Get Answers –Figure out potential problems –ASK MORE QUESTIONS –Evaluate Current Systems Details about O/S NIC’s if any Cabling if any –NEEDS vs. WANTS What is a HAVE to HAVE What is on the wish list

Questions These are in the book! –How many desktops will be attached? –How many servers if any attached? –What apps. Will be run? –Peer-to-Peer or Server-Based? –How much fault tolerance? –Money?

Questions Not in Book –Growth? – ? –Internet Access? –Fax Capablities? –Explanation of some typical examples!!

After Questions are Answered Sketch the network Layout of the office or offices Mark planned location of resources –Current & –New Put map into computer –netViz –Vizio DETAILED, DETAILED, DETAILED!!!

Topology, Layout, Diagram & Map Physical layout of: –Systems –Cables –Other resources Printers Network Copiers Fax Machines Internet Access Hardware How these components will communicate with each other: –Server or Servers –Hub –Direct Connection

Topology, Layout, Diagram & Map Design should allow for: –Expansion –Security Requirements –Be flexible as your needs change This will prevent a whole new system from having to be purchased. Topology will determine: –Performance –Growth Potential –Type of Equipment Purchased –Maintenance Plan

Standard Topologies Three Basic Topologies –BUS Series of computers connected along a single cable segment –STAR Computers connected via a central concentration point (HUB) –RING Computers connected to form a loop

BUS Advantages –Simplest & Most Common –Easy expansion with BNC barrel connector –Backbone Single Cable Element –Ethernet 10 Base-2 is most common (THINNET) Straight Line (theory) –Single PC crashes it does not affect the rest of the network “Passive Topology” PC’s only listen for signals Disadvantages –Single Cable Break halts entire network Individual systems still work but no network communication. –Because of signal bounce –Only one computer can send information at a time. More PC’s on network the slower it is –Can’t exceed max. cable length for particular type of network. (Chapter #6)

BUS Topology

Network Communication You MUST know how PC’s communicate All topologies communicate the same way Address data to a computer and put that data on cable as electrical signal Signal is: –Sent –Signal Bounce –Termination

Sending the Signal First data is addressed Then broken into packets (Chapter #6) Then sent across the network Received by ALL PC’s on the network –ONLY the computer that the packets were addressed to will accept the packets –e.g. Destiation: 02608C6C35FE

Sending the Signal / Speed of signal Affected by: –Type of topology –# times a PC sends data –Cable used –Applications being used –Distance between PC’s Think about this speed when determining the topology to be used.

Signal Bounce Signals travel from one end of the BUS to the other Must be Stopped when it reaches it’s destination or it would continue forever –Bouncing from one end to the other & back again –That would prevent any other PC from sending a signal Usually with Coaxial Cable –Usually with BNC terminator –Show them what one looks like

Cable Termination Terminator absorbs all signals that reach it –This clears the network for the next signal Similar to cable T.V. –Terminate “Open” connections and signal/picture will improve

Cable Break Physically cut or broken No termination so you get signal bounce –This causes ALL network activity to stop –Individual PC’s still work The longer the cable the more chance of a break

Attenuation & Repeater Attenuation –Weakened signal –Due to the length the signal must travel Repeater –Used to boost the signal strength –Does NOT correct errors in the signal Can cause some errors to be worse

Star Topology Advantages –Centralization of Resources –One PC fails does NOT affect whole network –One cable break does NOT affect whole network PC’s connected by a cable segments to a central HUB Single signal sent to HUB Hub receives signal and retransmits it down every other cable segment to all other computers on the network Only the computer the signal was addressed to will accept it Each PC sometimes called a NODE Disadvantages –More intricate cable installation –More expensive More cable More hardware –If HUB fails whole network is down Not PC’s though

Star Topology HUB

Ring Topology Token –Packet (token) passed around the ring to each PC in turn. –If a PC has info. to send it modifies the token, adds address information & the data, and sends token down the ring. –When token received by intended PC it returns a message to the sender indicating it’s arrival. Ring & Star by using a HUB to pass the token.

Ring Topology PC’s connected directly to form a circle of cable –No termination needed Signal acted upon or REGENERATED and resent Signal travels in only one direction Single RING network fails if one PC fails –IBM’s token ring Dual RING (tokens pass in both directions) can operate around ONE failure. –FDDI uses dual counter rotating rings

Ring Topology

HUB’s Central point of concentration in a STAR network Two Types of HUB’s –Active Regenerate the signals as they receive them Have many ports –Passive Signal is passed through without any amplification or regeneration Central connection point –Wiring Panel –Punch Down Block Can use both a Punch Down Block or Wiring Panel WITH a Hub.

Variations / Combinations of Major Topologies

Mesh –Most fault tolerant –Most expensive –Cable failure has NO effect –Uses with WAN’s to ensure comm. Even with cable failure

MESH

Star Bus –Star & Bus –Connecting many Star HUBs together on a BUS backbone Like the college

Star Bus Topology HUB

Star Ring Page 43

Homework Review Questions Project 2-1 –Hand Sketch –Computer Sketch