networking prelim 2 Flashcards
what is OSI?
Open Systems Interconnection
what is ISO?
International Organization for Standardization
Layers also divided into three groups
– Bottom: handles physical communications
– Middle: coordinates communication between nodes
– Top: involves data presentation
The OSI Layers
Application (Layer 7)
Presentation (Layer 6)
Session (Layer 5)
Transport (Layer 4)
Network (Layer 3)
Data Link (Layer 2)
Physical (Layer 1)
what is ANSI?
American National Standards Institute
handles physical communications
– Bottom:
coordinates communication between nodes
– Middle:
involves data presentation
– Top:
– Wave pattern with positive and negative voltages
– Examples: ordinary telephone or radio signal
– Used in WANs that employ analog modems
Analog signal
generates binary 1s or 0s
– Most common signaling method on LANs and high-
speed WANs
– Example 1: +5 volts produces 1, 0 volts produce 0
– Example 2: +5 volts produces 1, -5 volts produce 0
– Example 3 (Fiber-optics): presence of light is 1, else 0
Digital signal
what is EMI?
Electro Magnetic Interference
What is RFI?
Radio frequency interference
– Caused by magnetic force fields
– Generated by certain electrical devices
* Fans, electric motors, portable heaters, air-conditioners
Electro Magnetic Interference (EMI)
– Caused by electrical devices emitting radio waves
* Radio and television stations, radio operators, cable TV
– Problem when frequency matches network signal
Radio frequency interference (RFI)
monitor duplication
– Calculates size of information fields in frame
– Data Link layer at sender inserts value at end of frame
– Receiving Data Link layer checks value in frame
Cyclic redundancy check (CRC)
