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bus topology ppt

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Ethernet Tutorial: 

Ethernet Tutorial




LANS Networks usually confined to a small geographic area single building college campus The proliferation of LANs worldwide business education


Protocols Standards that allow computers to communicate. Defines identify one another on a network the form that the data should take in transit how this information should be processed once it reaches its final destination

Protocols (continued): 

Protocols (continued) Defines (continued) procedures for handing lost or damaged transmissions or “packets” Examples IPX TCP/IP DECnet AppleTalk LAT

Protocols (continued): 

Protocols (continued) Protocol independence the physical network doesn’t need to concern itself with the protocols being carried allows multiple protocols to peacefully coexist allows the builder of a network to use common hardware for a variety of protocols

What is Ethernet?: 

What is Ethernet?


Ethernet The most popular LAN technology a good balance between speed, price and ease of installation The perfect networking technology for most computer users today wide acceptance into the computer marketplace the ability to support virtually all popular network protocols

Ethernet (continued): 

Ethernet (continued) Defined by the Institute for Electrical and Electronic Engineers (IEEE) IEEE Standard 802.3 configuring an Ethernet specifying how elements in a network interact with one another

Media and Topologies: 

Media and Topologies


Topologies define how “nodes” are connected to one another a node is an active device connected to the network computer repeater bridge router

Topologies (continued): 

Topologies (continued) Ethernet media are used in two general configurations or topologies Bus Star

Bus topology: 

Bus topology consists of nodes strung together in series with each node connected to a log cable or bus a break will usually cause the entire segment to be inoperable

Star topology: 

Star topology links exactly two nodes together a break will only affect the two nodes on that link


Media Major types of media in use today ThickWire Thin coax Unshielded twisted pair Fiber optic


ThickWire 10 BASE5 Ethernet used for “backbones” up to 500m long as many as 100 nodes use “vampire tap” to connect new nodes nodes must be spaced exactly in increments of 2.5m

Thin Coax: 

Thin Coax 10BASE2 Ethernet lower cost and easier installation up to 185m long as many as 30 nodes each at least 0.5m apart connected or disconnected at the “T” connectors

Twisted Pair: 

Twisted Pair Level 5: 100Mbps Level 4: 20Mbps Level 3: 16Mbps Level 2 and 1: less than 5Mbps 10BASE-T Ethernet uses a star topology up to 100m long

Fiber Optic: 

Fiber Optic 10BASE-FL Ethernet useful against situations of electro-magnetic interference, lightning strike and so on up to 2km long can use for FDDI and other technologies faster than Ethernet




Transceivers used to connect nodes to the various Ethernet media known as Media Attachment Units (MAU)

Transceivers (continued): 

Transceivers (continued) provide an Application User Interface (AUI), connector for the computer many interface network cards also contain a buit-in 10BASE-T or 10BASE2 transceiver

Examples of Transceiver: 

Examples of Transceiver LTX-T (Twisted Pair Transceiver) LTX-TA (Twisted Pair Mini Transceiver) LTX-2 (Thin Coax Transceiver) LTX-2A (Thin Coax Mini Transceiver) LTX-5 (ThickWire Transceiver) LTX-FL (Fiber Optic Transceiver)


LTX-T Twisted Pair Transceiver 10BASE-T AUI network interface connector 7 diagnostic LEDs $79


LTX-TA Twisted Pair Mini Transceiver 10BASE-T AUI network interface connector 2 diagnostic LEDs $39


LTX-2 Thin Coax Transceiver 10BASE2 AUI network interface connector 2 diagnostic LEDs T-connector included $79


LTX-2A Thin Coax Mini Transceiver 10BASE2 AUI network interface connector 1 diagnostic LED $39


LTX-5 ThickWire Transceiver 10BASE5 AUI network interface connector 5 diagnostic LEDs AMP connector included $159


LTX-FL Fiber Optic Transceiver 10BASE-FL dual ST-style connectors AUI network interface connector 5 diagnostic LEDs $249




Repeaters connect two or more Ethernet segments of any media type provide the signal amplification Splitting a segment into two or more with a repeater allows a network to grow

Repeaters (continued): 

Repeaters (continued) count in the total node limit e.g. . a Thin Coax segment 185m long 29 nodes and a repeater e.g. . a ThickWire segment 500m long 98 nodes and 2 repeaters

Repeaters (continued): 

Repeaters (continued) necessary in star topologies one end the repeater the other the computer w/ a transceiver monitor Ethernet to run correctly e.g. . when a break occurs limit the effect of inoperable problems by “segmenting”, disconnecting the problem segment

Repeaters (continued): 

Repeaters (continued) The IEEE 802.3 specifications describe rules for the maximum number of repeaters in a configuration e.g. . the transmission path between two nodes the maximum number of network segments between two nodes 4 5




Bridges Function: To connect separate Ethernet together Goal: To achieve what appears to the network users to be a seamless network

Bridges (continued): 

Bridges (continued) map the Ethernet addresses of the nodes residing on each network segment then, allow only the necessary traffic to pass through the bridge

Bridges (continued): 

Bridges (continued) When a packet is received by the bridge: the bridge determines the destination and source segments If the segments are the same the packet is dropped (“filtered”) If the segments are different the packet is “forwarded” on

Bridges (continued): 

Bridges (continued) prevent all bad or misaligned packets form spreading from one segment to the others called “store-and-forward” devices look at the whole Ethernet packet before making their filtering or forwarding decisions

Ethernet Switches: 

Ethernet Switches

Ethernet Switches: 

Ethernet Switches “Cut-through” switches examining the address information contained at the start of the Ethernet packet decrease the amount of time required to determine if a packet should be filtered or forwarded, “latency”

Ethernet Switches (continued): 

Ethernet Switches (continued) The term “Ethernet Switch” any device of multiple ports which is able to filter and forward packets at nearly the speed of Ethernet (“wirespeed”) regardless of the technique because store-and-forward bridges have now increased their speed

Ethernet Switches (continued): 

Ethernet Switches (continued) The term “Bridge” two-port devices which use the store and forward technique




Routers filter out network traffic filter by specific protocol born out of the necessity for dividing networks logically instead of physically

Routers (continued): 

Routers (continued) An IP router divide a network into various subnets only traffic destined for particular IP addresses can pass between segments takes more time than a switch or bridge which only looks at the MAC layer

Routers (continued): 

Routers (continued) The term “brouters” devices which have both bridging and routing capability however switches and bridges frequently have some router-like features such as selective protocol filtering

Network Switch Example: 

Network Switch Example Sun (G) Sun (H) Microvax (F) Workstation (E) Netware File Server (C) Macintosh (D) PC (A) Microvax (B) LSB4 Switch LTX-2 LTX-2 LTX-2 LTX-2 LTX-2 LTX-2 LTX-5 LTX-5 LTX-5 LTX-5 LTX-5 LTX-5

The Spanning Tree: 

The Spanning Tree

The Spanning Tree: 

The Spanning Tree The Spanning Tree Algorithm a software device for describing how switches & bridges can communicate to avoid network loops By exchanging packets called BPDUs, the switches & bridges establish a singular path for reaching each network segment.

The Spanning Tree (continued): 

The Spanning Tree (continued) A switches or bridge port is turned off if another pathway to that segment already exists

The Spanning Tree (continued): 

The Spanning Tree (continued) The process of passing the BPDU packets is continuous so if a switch or bridge suddenly fails, then the remaining devices will reconfigure pathways to allow each segment to be reached

The Spanning Tree (continued): 

The Spanning Tree (continued) network managers design loops into a bridged network so if a switch or bridge does fail, the Spanning Tree will calculate the alternate route into the network configuration.

Spanning Tree Example: 

Spanning Tree Example LTX-5 LTX-5 LTX-5 LTX-5 LB2 #1 LB2 #2 LB2 #3 LB2 #4 LTX-2 LTX-2 LTX-2 LTX-2 10BASE2 10BASE2 10BASE5 10BASE5 AUI CABLE AUI CABLE AUI CABLE AUI CABLE

Terminal & Printer Servers: 

Terminal & Printer Servers

Terminal & Printer Servers: 

Terminal & Printer Servers support the use of following on networks terminals printers modems, and other serial devices have own network addresses perform more than just a physical connection or signalforwarding function

Terminal server: 

Terminal server a server which provides network access to serial devices support serial printers as well as serial terminals bidirectional devices

Printer server: 

Printer server is expected to have at least one parallel port may also have one or more serial ports unidirectional devices


Advantages Saving on long-distance cabling because of its multiple ports Enhanced remote monitoring and control because of its inherent intelligence Easier to manage because of its support for protocols like SNMP

Advantages (continued): 

Advantages (continued) Local communications able to broadcast messages to all devices connected to the servers Sharing resources and balancing workloads

Advantages (continued): 

Advantages (continued) Supporting multiple protocols Supporting workstations Protocol conversion Staying flexible

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