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 Token- passing. 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 2NICs 1Media 1Repeaters 1Hubs 2Bridges 2Switches 3Routers 1-7Clouds 1Network 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 to trace data flow thru LAN through Layer 1 Device through Layer 2 Device through Layer 3 Device through Cloud and Layer 1-7 Devices

Refer to Curriculum 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