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Describe the basic and hybrid LAN physical topologies and their uses, advantages, and disadvantages Describe the backbone structures that form the foundation for most LANs Understand the transmission methods underlying Ethernet networks Compare the different types of switching used in data transmission
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Is the physical layout of the nodes on the network 3 fundamental shapes Bus Ring Star
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Also known as the passive topology Supports only one channel All nodes must listen before transmitting Uses coax cable that must be terminated with 50-ohm resistors to prevent single bounce – never ending transmissions Does not scale well
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Each node is connected to the two nearest nodes forming a circle Data travels in a clock wise motion around the ring Each node accepts and responds to packets that are addressed to that node. Provides a single point of failure for the entire network
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Most commonly used topology Every node connects to either a central hub, router or switch Can only support 1024 nodes
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Refers to the way the data is transmitted between nodes rather than the physical layout Most common are bus and ring topologies Knowledge of logical topologies aid in troubleshooting
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Star-wired ring Star-wired bus
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Cabling that connects the hubs, switches and routers Uses mediums that are high capacity capable Carries more traffic than local nodes The most significant piece in the network’s infrastructure
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Simplest type Connects in a daisy-chain fashion Gateways, routers switches and bridges are the most common devices that are found in this type of backbone
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◦ Network devices are connected in a hierarchy ◦ The order of the hierarchy is as follows Routers Switches Hubs ◦ Allows for simple growth and limited capital outlay for growth ◦ To expand, just add more layers ◦ Provides the ability to segregate workgroups ◦ More easily managed
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Collapsed Backbone ( Needs Graphic) ◦ Uses only one router or a switch for all connections to the networks nodes ◦ Risky because of a central point of failure Parallel Backbone ( Needs Graphic) ◦ Most robust type of backbone ◦ Provides 2 central routers with 2 connections to every switch
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◦ Determines how connections are made between nodes ◦ Three methods of switching Circuit switching Message switching Packet switching
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Circuit Switching ◦ Connection is established before data is transmitted Stays connected until users terminate the session Bandwidth is dedicated to this connection All data flows down the same path ◦ Suited for voice and video transmission Message Switching ◦ Once the connection is established it forwards the data ◦ Once the data is forwarded the connection is broken down Packet Switching ◦ Most popular method ◦ Packets are down any path in the network to its final destination ◦ Once the packets reach their destination, the packets are reassembled
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◦ Integrates Layer 2 information about network links (bandwidth, latency, utilization) into Layer 3 (IP) within a particular autonomous system in order to simplify and improve IP-packet exchange.IPpacket ◦ Can create circuit switched like connections ◦ Uses MPLS labels to improve operation MPLS label is inserted between layer 2 header and layer 3 header Routers only need to interpret the MPLS label then forward the packet ◦ Provides better QoS due to faster packet forwarding
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All Ethernet networks use CSMA/CD Carrier Sense Multiple Access The node must first access the transmission medium and “listen” to see if the channel is free If it is not clear to transmit the node waits a brief time and then retries Collision Detection Once a node has detected a collision it stops transmitting The node’s NIC issues a 32-bit sequence that alerts the rest of the network nodes that the collision has taken place - called jamming This lets the network nodes know to disregard the faulty transmission The node tries again by repeating these same steps
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1 2 3 4
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10BaseT – 10Mbps/Baseband/Twisted Pair Cat 3 or higher Must follow 5-4-3 rule – can only have 5 network segments, 4 repeating devices, and only 3 populated segments Maximum cable length is 100 meters 100BaseT - 100 Mbps/Baseband/Twisted Pair – Fast Ethernet Does not follow 5-4-3 rule Maximum cable length is 100 meters Full-duplexing can increase to 200Mbps 1000BaseT – 1000 Mbps/Baseband/Twisted Pair Uses all 4 pairs of a Cat 5 or higher twisted pair cable to transit at these speeds Known as Gigabit Ethernet Maximum cable length is 100 meters
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100Base-FX – 100Mbps/Baseband/Fiber Optic Still considered Fast Ethernet Maximum cable length is 2000 meters Must use multimode fiber with at least 2 strands 1000Base-LX – 1000Mbps/Baseband/Long Wavelength (1300 nanometers) Most common Gigabit Ethernet standard in use today Single Mode Fiber maximum length is 5000 meters Multimode Fiber maximum length is 550 meters Excellent for backbone cabling 1000Base-SX – 1000Mbps/Baseband/Short Wavelength (850 nanometers) Uses only multimode fiber optic cable Maximum length with 50 micron core is 550 meters Maximum length with 62.5 micron core is 275 meters
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10GBase-SR and SW – 10Gbps/Baseband/Short reach/R-works with LANs/W-works with SONET WANs Uses multimode fiber 0 micron core maximum length is 300 meters 62.5 micron core maximum length is 66 meters 10GBase-LR and LW – 10Gbps/Baseband/Long reach/R-works with LANs/W-works with SONET WANs Uses single mode fiber Wavelengths of 1310 nanometers Maximum cable length is 10,000 meters
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Uses single mode fiber only Wavelength of 1550 nanometers Maximum length is 40,000 meters
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Provides power to devices through the Ethernet cable 2 type of devices Power Sourcing Equipment (PSE) Powered Devices (PD)
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For more information on this lesson, See Chapter 5 in the text book or email the Professor **All Slides and graphics were produced by Professor Patrick Hughes**
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