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Local Area Networks
Andres, Wen-Yuan Liao
Department of Computer Science and Engineering
De Lin Institute of Technology
http://www.cse.dlit.edu.tw/~andres
OverviewLocal area network (LAN) devices High-speed, low-error data
networks that cover a relatively small geographic area
Connect workstations, peripherals, terminals, and other devices
Basic LAN Devices
The topology LAN devices in a topology NICs,Media Repeaters , Hubs, Bridges, Switches Routers Clouds , Network segments
Topology
Defines the structure of the network Physical topologyThe actual layout of the wire (media)
Logical topologyDefines how the media is accessed
by the hosts.
Physical topology
BusUses a single backbone segmentAll the hosts connect to it directly
Ring Connects one host to the next and the last
host to the first
StarConnects all cables to a central point
Physical topology
Extended star Links individual stars together by linking the
hubs/switches.
hierarchical Similar to an extended star The system is linked to a computer The computer controls the traffic on the topology
Mesh Each host is connected to all other hosts Internet
Logical topologiesBroadcastEach host sends its data to all other
hosts on the network medium (no order)
Token-passingControls network access by passing an
electronic token sequentially to each hostWhen a host receives the token, that
means that that host can send data on the network
LAN devices in a topology
Devices that connect directly to a network segment are referred to as hosts Operate at all 7 layers
NICsAn NIC card is a printed circuit board
Layer 2 device
Media Access Control (MAC) address
AUI (Attachment Unit Interface)
RJ-45
BNC
AUI
Media
Carry a flow of information
Be considered Layer 1 components Cable length Cost Ease of installation
Repeaters
One of the disadvantages of the type of cable that we primarily use (CAT5 UTP) is cable length Repeaters: strengthen their signals over long distancesThe purpose of a repeater is regenerate and retime network signals
Repeaters
5-4-3 Rule: you can connect five network segments end-to-end using four repeaters but only three segments can have hosts (computers) on them
Hubs
Multi-port repeater
Create a central connection point for the wiring media
Increase the reliability of the network
Classifications I
ActiveThey take energy from a power
supply to regenerate network signals
Passive They merely split the signal for
multiple users
Classifications IIIntelligent hubsHave console ports, which means
they can be programmed to manage network traffic
Dumb hubsTake an incoming networking signal
and repeat it to every port without the ability to do any management
Repeaters
Token-ring network : Media Access Unit (MAU)
FDDIs: the MAU is called a concentrator.
Bridges
Layer 2 device
To filter traffic on a LAN
To keep local traffic local
Allow connectivity to other segments
Every networking device has a unique MAC address on the NIC
Switches
Layer 2 deviceMulti-port bridge Make decisions based on MAC addresses The purpose of a switch is to concentrate connectivity, while making data transmission more efficient.
Routers Layer 3 device (IP address)Connect different Layer 2 technologiesEthernet, Token-ring, and FDDI.
To examine incoming packets (Layer 3 data), choose the best path for them through the network, and then switch them to the proper outgoing port
Clouds
There is a way to connect to that other network (the Internet), but does not supply all the details of either the connection or the network
A collection of devices that operate at all levels of the OSI model, it is classified as a Layer 1-7 device
Network segments
Layer 1 segmentA segment identifies the Layer 1
media that is the common path for data transmission in a LAN
Repeater is the separator
Layer 2 segment
Segments
A segment as a collision domain
Segment: a Layer 4 PDU
Evolution of Network Devices
Evolution of network devices
Milestones in the history of networking
Evolution of networking devices and the OSI layers
Devices and the OSI layers
Hosts & servers operate at Layers 2-7
Layer 1Transceivers, repeaters, and hubs Patch cables, patch panels, and other
interconnection components
Layer 1,2: NIC, Bridge, Switch
Layer 1,2,3: Router
Basics of Data Flow Through LANs
Encapsulation and packets review Packet flow through Layer 1 devices Packet flow through Layer 2 devices Packet flow through Layer 3 devices Packet flow through clouds and through Layer 1-7 devices A data packet's path through all seven layers of a LAN
Encapsulation & packets review
Transport layer: segmentsSequence numbers (order)
Network layer: packet Destination & source address
Data Link layer: frameAdd the source/destination(MAC)
address
Encapsulation & packets review
The bottom three layers (Network, Data Link, Physical) The primary movers of data
across an Intranet or Internet.
The gateway uses all seven of the OSI layers
Layer 1 devices are passive (e.g. plugs, connectors, jacks, patch panels, physical media)
AUI port to RJ-45
RJ-45 electrical toST Optical
selection of best path and actual switching
Gateway
SNALAN
Building LANs
Summary
LAN devices, such as routers, switches and hubs
Evolution of networking devices
basics of data flowbasics related to building LANs