Lesson 1: OSI Model Flashcards
What is a network?
Two or more computer systems ‘link’ed by transmission media to share information
Characteristics of a LAN
Local Area Network
Internal / Private network
Network in a singular location.
Can be 2 PC’s in a SOHO or an enterprise network
Characteristics of a WAN
Wide Area Network,
External/Public network,
Networks in different geographic locations but with shared links,
“The Internet”
What is a node?
A device communicating on the network via one or more interfaces
(Can include endpoints such as computers)
(Can include forwarding nodes such as switches and routers)
What is a host?
Host typically refers to a computing device (not a switch or a router)
What is transmission media?
Cabled or wireless ‘links’ between nodes
What is a protocol?
A set of rules enabling systems to communicate by exchanging data in a structured format
What is addressing?
Describes where data should go
Explain encapsulation
Describes how data should be packaged for transmission
Header / payload
What devices operate at the Physical layer?
Transceiver, Hub, Repeater, Modem
Layer 1 of the OSI model
Physical (Bit Stream)
Nodes, stations, and hosts (computing device)
Transmission media: cabled or wireless ‘links’ between nodes
Layer 2 of the OSI model
Data Link (Frames)
Organizes bits into frames
Destination and source hardware addresses (MAC addresses)
Error detection
Layer 3 of the OSI model
Network (Packets), Moving data around a network of networks, Logical addressing between networks, IP addresses, Routing
Layer 4 of the OSI model
Transport (Segment)
Multiplexing and de-multiplexing
TCP/UDP
Responsible for ensuring reliable data delivery
Layers 5 and 6 of the OSI model
Session and Presentation (Data)
Divisions between upper layers less important in real-world protocols
Layer 7 of the OSI model
Application (Data)
Provides communication protocols and interfaces for software processes running on different hosts
Application programming interfaces (APIs) for software programs
What devices operate at the Data Link layer?
Network adaptor or Network Interface Card (NIC),
Basic switch,
Wireless Access point (AP)
What devices operate at the Network layer?
Router
Layer-3 switch
What devices operate at the Transport layer
Security devices like advanced firewalls and IDSs (Intrusion Detection System)
What is multiplexing/de-multiplexing?
Packages data in a stream of segments
Merges segments from different applications over the network link
Port numbers allow receiving host to de-multiplex and reassemble data for the appropriate application handler
