Simple LAN Topologies  Terminators stop signals after they have reached their destination  Signal bounce –Phenomenon in which signals travel endlessly between the two ends of a bus network FIGURE 5-2 Terminated bus network

Hybrid LAN Topologies  Star-wired bus –In a star-wired bus topology, groups of workstations are star-connected to hubs and then networked via a single bus FIGURE 5-6 Star-wired bus network topology

Enterprise-wide Topologies  Serial backbone –Two or more hubs connected to each other by a single cable  Distributed backbone –A number of hubs connected to a series of central hubs or routers in a hierarchy FIGURE 5-9 Simple distributed backbone network

Enterprise-wide Topologies FIGURE 5-10 Distributed backbone connecting multiple LANs

Enterprise-wide Topologies  Mesh networks –Routers are interconnected with other routers with at least two pathways connecting each router FIGURE 5-13 Example of a mesh network

Network Transport Systems  Network transport system –Sometimes referred to as the network’s logical topology –Describes network’s logical interconnection between nodes, rather than its physical interconnection  Switching –Component of a network’s logical topology that manages how packets are filtered and forwarded between nodes on a network

Network Transport Systems  Circuit switching –Connection is established between two network nodes before they begin transmitting data  Message switching –Connection is established between two devices in the connection path; one device transfers data to the other, then breaks the connection  Packet switching –Data are broken into packets before they are transported

Network Transport Systems  Shared Ethernet –Carrier Sense Multiple Access with Collision Detection (CSMA/CD) Communication rules used by shared Ethernet networks FIGURE 5-19 CSMA/CD process

Network Transport Systems Ethernet versions  10Base2 –Thin coaxial cable –Simple bus topology –10Base refers to its network speed, 10 megabits per second (Mbps) –BNC T connectors are used by nodes on a Thinnet cabling technology to tap into the network FIGURE Base2 Ethernet network

Network Transport Systems  10Base5 –Thick coaxial cable –Simple bus topology  10BaseT –Twisted-pair cable –Star-bus or hierarchical topology FIGURE BaseT Ethernet network

Network Transport Systems FIGURE 5-22 Enterprise-wide Ethernet 10BaseT network

Network Transport Systems  100BaseT –Also known as Fast Ethernet –Enables LANs to run a 100 Mbps data transfer rate  100BaseTX –Achieves its speed by sending the signal 10 times faster and condensing the time between digital pulses and the time a station is required to wait and listen in CSMA/CD

Network Transport Systems  100BaseT4 –Achieves its speed by breaking up the data stream –Cannot support full duplexing, an enhancement allowing simultaneous two-way transmission between nodes while eliminating collisions  100BaseVG –Can transmit data at 100 Mbps –Uses a demand priority access method

Network Transport Systems  Demand priority –Each device on a star or hierarchical network sends a request to transmit to the central hub, which grants requests one at a time  Intelligent hub –Can manage transmissions by dictating which nodes can send and receive data at every instant Figure 5-23 CSMA/CD versus demand priority

Network Transport Systems  Switched Ethernet –Enables multiple nodes to simultaneously transmit and receive data and individually take advantage of more bandwidth because they are assigned separate logical network segments through switching –Switch manages network switching –1 Gigabit Ethernet Runs at 1000 Mbps Usually relies on fiber-optic cable

Network Transport Systems FIGURE 5-24 Switched Ethernet network

Network Transport Systems Ethernet frame types: Ethernet –Default frame type for Novell’s IntraNetWare network operating system –Defining characteristics of its data portion are the source and destination service access points that belong to the Logical Link Control layer

Network Transport Systems  Service Access Point (SAP) identifies a node or internal process using the LLC protocol  Frame Check Sequence (FCS) field ensures the data are received as sent  Cyclical Redundancy Check (CRC) is an algorithm used by FCS field in Ethernet frames FIGURE 5-25 Ethernet frame

Network Transport Systems  Ethernet –Original NetWare Ethernet frame type –Default frame type for networks running NetWare versions lower than 3.12 FIGURE 5-26 Ethernet frame

Network Transport Systems  Ethernet II –Original Ethernet frame type developed by DEC, Intel, and Xerox, before the IEEE began to standardize the Ethernet FIGURE 5-27 Ethernet II frame

Network Transport Systems  Ethernet SNAP –Adaptation of Ethernet and Ethernet II –SNAP stands for Sub-Network Access Protocol FIGURE 5-28 Ethernet SNAP frame

Network Transport Systems  Understanding frame types –Autosense enables a NIC to automatically sense what types of frames are running on a network and set itself to that specification

Network Transport Systems  Ethernet design considerations TABLE 5-1 Characteristics of different Ethernet versions