OSI (1-2) Flashcards
PDU
Protocol Data Unit
aka Data Service Unit
Groupings of bits at upper layers of OSI
LLC Sublayer
Logical Link Control Sublayer
Sublayer of Data Link Layer
Synchronizing Bits
At layer 1 of the model networked devices must agree when one bit stops and another starts.
Two approaches are asynchronous and synchronous
DLC
Data Link Control
Collective processes of Layer 2: package data into frames, error detection / correction, finding network devices with an address, flow control
Layer 2 Sublayers
MAC
LLC
MAC Sublayer
Media Access Control Sublayer
Sublayer of Data Link layer
Broadband
Divides bandwidth available on medium into channels.
Layer 1
Baseband
Use all available frequencies on a medium to send data.
Used by Ethernet
Layer 1
FDM
Frequency-Division Multiplexing
Divides medium’s frequency range into channels.
Difference communication sessions use different channels.
Form of broadband used by a cable modem
Multiplexing
Allows multiple communications sessions to share same physical medium
Layer 1
Physical Addressing
Physical Addressing
Layer 2
MAC Address
Media Access Control
48-bit hexadecimal address assigned on NIC
First 24 bits are the vendor code
Flow Control
Limits the amount of data a sender can send at a time
Layer 2
Error Control
During acknowledgement message receiver tells sender if:
expected frame was not received
received frame was corrupted
Layer 2
Synchronizing Transmissions
How devices synchronize coordinate when frames will be sent Isochronous Asynchronous Synchronous Layer 2
