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Cisco – Chapter 3 LAN LAN Teaching Topology • physical topology is the actual layout of the wire (media) • logical topology defines how the media is accessed by the hosts – Logical topologies are Broadcast (Ethernet) and Tokenpassing. • Broadcast - each host sends its data to all other hosts on the network medium – CSMA/CD • Token Passing -Pass electronic token sequentially to each host. LAN Devices • • • • • • • • • 2 NICs 1 Media 1 Repeaters 1 Hubs 2 Bridges 2 Switches 3 Routers 1-7 Clouds 1 Network Segments NICS – Layer 2 • printed circuit board that fits into the expansion slot of a bus on a computer’s motherboard or peripheral device • also called a network (LAN) adapter • Layer 2 devices because each individual NIC carries a unique code(looks at MAC – physical address) • Controls the host's access to the medium. AUI • AUI does not always match (Cisco 2500 router) • transceiver (transmitter/receiver) is used to connect – Layer 1 – transceiver converts one type of signal or connector to another – convert electrical signals to optical signals – considered a Layer 1 device, because it only looks at bits Media Layer 1 • basic functions of media are to carry a flow of information, in the form of bits and bytes, through a LAN • networking media confine network signals to a wire, cable, or fiber and wireless • PAN (Personal area network) – uses human body as medium Media 2 • Selection criteria include: – – – – Cable length Cost Ease of installation Total number of hosts • Most common medium is Cat 5 UTP Repeaters – Layer 1 • Extend length of cable run beyond maximum length for that medium – Concept originated from early form of visual communication when signals were sent from hill to hill visually – Purpose is to regenerate (amplify) and retime signals – Single-port in and single-port out device – Act only on bit level Hubs – Layer 1 • Regenerate (amplify) and retime network signals • Create a central connection point for the wiring media • Increase in the reliability of the network (one connection point) • Active hubs extend signal length; passive hubs do not extend length • Role in Token ring is played by MAU, a.k.a. concentrator • A.K.A. multi-port repeater Bridges – Layer 2 • designed to connect two LAN segments • filters traffic on a LAN to keep local traffic local • allows connectivity to other parts (segments) of the LAN • Uses MAC address to make filtering decision • Are being replaced by switches & routers Switches – Layer 2 • Called a multi-port bridge • Make decisions based on MAC addresses • Switch data only out port to which proper host is connected • Part of function is connectivity concentration (allow many devices to connect to one point in network) • Can provide each port with full bandwidth Routers – Layer 3 • Makes decisions based on groups of network addresses (logical addressing) • Can also connect different layer 2 technologies, such as Ethernet, Token-ring, and FDDI. • Have become the backbone of the Internet, running the IP protocol. • Choose best path and switch to proper port • Primary functions – path selection & switching Cloud – Layer 1- 7 • Reminds us there is a way to connect but does not supply details of connection or network • Represents a large group of details that are not pertinent to the situation Network Segments – Layer 1 • Identifies the layer 1 media that is the common path for data transmission in a LAN; sometimes called WIRE • Each time an electronic device is used to extend the length or manage data on the media a new segment is created • It means segments of the network here; it does have a different meaning at Layer 4 Network Milestones • • • • • 1950s – Mainframe computers 1960s – Mini computrs 1970s – Advent of personal computers 1970s – Beginning of Internet 1980s – Gateways – special purpose computers to interconnect LANs • 2000 – Convergence of voice, video, and data into one information stream Network Evolution • See handout distributed first day of class Encapsulation • Top three layers prepare data for transmission by creating a common format • Transport layer breaks data up into units called segments & assigns sequence #s • Network layer encapsulates segment into a packet & adds IP addresses • Data-Link Layer encapsulates packet into a frame and adds MAC addresses • Physical Layer sends out binary bits on media Encapsulation 2 • Bottom three layers are primary movers of data – Physical, Data Link, and Network • Exception is a Gateway – a device designed to convert data from one format to another – Gateway uses all 7 layers of OIS model • Data – Segments – Packets – Frames - Bits Students Should Load Curriculum • • • • • Start with 3.3.1 to trace data flow thru LAN 3.3.2 through Layer 1 Device 3.3.3 through Layer 2 Device 3.3.4 through Layer 3 Device 3.3.5 through Cloud and Layer 1-7 Devices Refer to Curriculum • 3.4.1 - Teaching Topology • Refer to lab – we already built a simple LAN • Have one group connect two PCS and then connect to Internet while other groups work on reviewing the procedure by using lab 3.4.2