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Layer One and Two LAN Networking Wires and connections Station to station packet transmission Layer One and Two LAN Networking Wires and connections Station to station packet transmission

OSI: Open Systems Interconnection Reference Model LAN OSI: Open Systems Interconnection Reference Model LAN

OSI Reference Model Application Presentation Session Transport Network Data Link Physical ©”A Guide to OSI Reference Model Application Presentation Session Transport Network Data Link Physical ©”A Guide to Networking Essentials”, 1998, Course Technology.

Open Systems Interconnection (OSI) z. International Standard z. Written to be a manufacturing standard, Open Systems Interconnection (OSI) z. International Standard z. Written to be a manufacturing standard, but never built z. Used as a vocabulary short hand z. Applies to all extensions of networks

OSI Reference Model OSI Reference Model

OSI Layer 1 Local Area Network protocols Physical layer: standards for physical connections (e. OSI Layer 1 Local Area Network protocols Physical layer: standards for physical connections (e. g. plugs and connectors) Responsible for getting bits from one location to another. z Medium z Connectors z Representation of signals

Media z. Twisted Pair Copper Wire shielded vs unshielded plenum vs PVC z. Coaxial Media z. Twisted Pair Copper Wire shielded vs unshielded plenum vs PVC z. Coaxial Copper Cable thinnet and thicknet z. Fiber single mode and multi-mode z. Microwave z. Infrared, Radio

Unshielded Twisted Pairs z. Cheapest alternative for LAN cabling z. Already exists in most Unshielded Twisted Pairs z. Cheapest alternative for LAN cabling z. Already exists in most offices z. Adapts to star wiring and hub systems z. Trend in modern LAN installations z. New technologies adapt to it z. Shielded cable used where electronic interference a problem

Cat 5 Twisted Pair Wiring Cat 5 Twisted Pair Wiring

Twisted Pair Signals Reverse phases to cancel noise LINE 1 + LINE 2 - Twisted Pair Signals Reverse phases to cancel noise LINE 1 + LINE 2 -

Cable categories Cable categories

Twisted Pair Connectors z. Wiring Pairs yblue, white-blue yorange, white-orange ygreen, white-green ybrown, white-brown Twisted Pair Connectors z. Wiring Pairs yblue, white-blue yorange, white-orange ygreen, white-green ybrown, white-brown z. RJ-11 and RJ-45 z. D connectors

RJ-45 (Registered Jack 45): 8 wires for Ethernet RJ-45 (Registered Jack 45): 8 wires for Ethernet

RJ-11 (4 or 6 wire versions) for telephones RJ-11 (4 or 6 wire versions) for telephones

Unshielded Twisted Pairs z. Phones use 1 pair z 10 Base. T uses 2 Unshielded Twisted Pairs z. Phones use 1 pair z 10 Base. T uses 2 pairs of Category 5 copper z 100 Base. FX uses multimode fiber

10 Base. T Ethernet Wiring 10 Base. T Ethernet Wiring

Fiber Optic Cables z. Longer distances z. High data rate requirements z. High interference Fiber Optic Cables z. Longer distances z. High data rate requirements z. High interference situations z. High security situations z. Connections more difficult than with UTP

Fiber Optic Single Mode Laser 8/125 micron Up to 50 miles LED Multimode 62. Fiber Optic Single Mode Laser 8/125 micron Up to 50 miles LED Multimode 62. 5/125 micron Up to 2000 meters

Fiber-optic Connectors Fiber-optic Connectors

Wireless z. Infrared z. Radio y. Microwave y. Radio Frequency x. Spread Spectrum & Wireless z. Infrared z. Radio y. Microwave y. Radio Frequency x. Spread Spectrum & Wi-Fi (IEEE 802. 11) z. Wireless security

Wireless LAN Access Wireless LAN Access

Local Area Networks Layer 2 Local Area Networks Layer 2

"Gentlemen! Start — your — laptops!" Copyright 1998 Doug Adams

Local Area Networks that move data from station to station using a common set Local Area Networks that move data from station to station using a common set of layer 1 and layer 2 protocols. y. Common broadcast domain y. Local ownership y. Common operating system y. Machine ID addressing

OSI Reference Model Application Presentation Session Transport Network Data Link Physical ©”A Guide to OSI Reference Model Application Presentation Session Transport Network Data Link Physical ©”A Guide to Networking Essentials”, 1998, Course Technology.

Data Link - Layer 2 2. Data link layer: protocols for error free transmission Data Link - Layer 2 2. Data link layer: protocols for error free transmission from station to station The data link is responsible for node to node validity and integrity of the transmission. The transmitted bits are divided into frames; for example, an Ethernet, Token Ring or FDDI frame in local area networks. Layers 1 and 2 are required for every type of communications.

Data Link - Layer 2 functions Data Link - Layer 2 functions

Data Link Sub-layers z. Media Access Control (MAC) y. Standards for addressing and locating Data Link Sub-layers z. Media Access Control (MAC) y. Standards for addressing and locating nodes z. Logical Link Control (LLC) y. Standards for communication with higher layers

LAN Operating Protocols z. Ethernet open standard, cheap, most common z. Token Ring IBM LAN Operating Protocols z. Ethernet open standard, cheap, most common z. Token Ring IBM proprietary, high quality, expensive z. Others

Network Interface Cards z. Build, send out and accept frames z. Usually a daughter Network Interface Cards z. Build, send out and accept frames z. Usually a daughter board on PC z. Must match LAN and CPU z. Require drivers to operate

Network Interface Cards (NIC) Network Interface Cards (NIC)

Ethernet Carrier Sense Multiple Access/Collision Detection Trailer Body Listen before transmit Contention access Retransmit Ethernet Carrier Sense Multiple Access/Collision Detection Trailer Body Listen before transmit Contention access Retransmit on collision Header

Ethernet: CSMA/CD (IEEE 802. 3) Carrier Sense Multiple Access with Collision Detection y. Compare Ethernet: CSMA/CD (IEEE 802. 3) Carrier Sense Multiple Access with Collision Detection y. Compare channel voltage to reference level y. Any node can transmit if channel free y. Collision detection during transmission x. Jamming x. Random back off y. Slot time and minimum packet size

Manchester Encoding (self-clocking bit stream) 0 1 0 High-to-Low = 0 Low-to-High = 1 Manchester Encoding (self-clocking bit stream) 0 1 0 High-to-Low = 0 Low-to-High = 1 Switch voltage at each time point

Ethernet Packets z. Synchronization z. Data transparency z. MAC addresses z. Minimum length z. Ethernet Packets z. Synchronization z. Data transparency z. MAC addresses z. Minimum length z. Error check z. Alternate Ethernet packet formats

Ethernet Packet Structure Ethernet Packet Structure

Administration z. Acknowledgements z. Address announcements (identification) z. Slot time z. Card streaming z. Administration z. Acknowledgements z. Address announcements (identification) z. Slot time z. Card streaming z. Hub access z 10 Base. T, 100 Base. T, Gigabit Ethernet

10 Base. T Specifications (Twisted Pair Ethernet) z 100 m to hub z 1024 10 Base. T Specifications (Twisted Pair Ethernet) z 100 m to hub z 1024 stations per network z 10 mbps z. UTP z. Star/bus

LAN Logical/Physical Topologies Bus Ring Star LAN Logical/Physical Topologies Bus Ring Star

Network Logical Topologies are determined by the technologies that run the network z Bus: Network Logical Topologies are determined by the technologies that run the network z Bus: Ethernet z Ring: Token ring SONET, FDDI z Star: Mainframe Switched Ethernet

Ethernet: Physical Star, Logical Bus Ethernet: Physical Star, Logical Bus

LAN with hubs LAN with hubs

Hubs or Switches Hubs or Switches

Switches (Layer 2) z. Route packets to destination nodes based on MAC addresses y. Switches (Layer 2) z. Route packets to destination nodes based on MAC addresses y. Limit traffic on unused branches y. Provide additional security y. Connect 10 Mb and 100 Mb branches z. Operate in firmware

Switch (CISCO Catalyst 1928) Switch (CISCO Catalyst 1928)

Ethernet Switching Ethernet Switching

Token Ring (IEEE 802. 5) z. Allocated access via electronic token z. Priority access Token Ring (IEEE 802. 5) z. Allocated access via electronic token z. Priority access reservation z. Confirmed packet delivery z. Multiple monitor functions

Token Ring Token Ring

Token Ring Message Token access Equal access Collision avoidance CRC Body Header Token Ring Message Token access Equal access Collision avoidance CRC Body Header

Empty Token Structure Empty Token Structure

Dataframe Token Structure Dataframe Token Structure

Topology: Logical or Physical? Bus Ring Star Topology: Logical or Physical? Bus Ring Star

Network Topologies are determined by the technologies that run the network z Bus: Ethernet Network Topologies are determined by the technologies that run the network z Bus: Ethernet z Ring: Token ring SONET, FDDI z Star: Mainframe Switched Ethernet