Explaining the OSI and TCP/IP Models Flashcards
Give all the points of network boundaries
Two or more computer systems linked by transmission media to share information
Networks are built to provide useful services
Sharing data and resources
Email and database applications
Web applications and social networking
Voice and multimedia conferencing
Local Area Network (LAN)
Wide Area Network (WAN)
Give a description of PDUs
Rules for exchanging data
Addressing
Encapsulation
Header
Payload
Give a full description of Layer 1
Layer 1:
Nodes, stations, and hosts
A node is 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
The station can be used instead of a node when talking about wireless networks
The host typically refers to a computing device (not a switch or a router)
Transmission media: cabled or wireless links between nodes
Physical topology
Mechanical specifications for the network medium
Cable specifications
Connector form factor and pin-outs
Radio transceiver specifications
Signaling (bit transmission/encoding)
Devices
Transceiver
Media converter
Hub/repeater
Modem
Give a full description of Layer 2
Local network devices
Nodes that forward communications within the same physical network (switching)
Physical/local addresses
Organize bits into frames
Destination and source hardware addresses
Media Access Control (MAC) address
Error detection
Flow control
Media access rules/logical topology
Contention (logical bus topology)
Token-passing (logical ring topology)
Give all Layer 2 devices
Network adapter or network interface card (NIC)
Bridge
Basic switch
Wireless access point (AP)
What are the IEEE 802 Standards
802.2 (Logical Link Control sublayer)
Provides the standard interface for the Network layer, regardless of the MAC sublayer protocol
802.3 (Media Access Control sublayer) or Ethernet
Logical topology
Media access method
Hardware (MAC) addresses
Frame format
Error checking
Physical layer (signaling and media) specifications
Give a description of Layer 3
Moving data around a network of networks (internetwork/the Internet)
Logical addressing between networks
Routing
Route discovery
Path selection
Devices
Router
Layer 3 switch
Basic firewall
What is switching vs routing components
WAN router/firewall
LAN router
Subnetworks
Switches
Backbones
Give a description of Layer 4
Multiplexing and de-multiplexing
• Identifies application data via port numbers
• 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
• Reliable delivery
• Connection establishment
• Acknowledgements and negative acknowledgments
• Segmentation and sequencing
• Flow control
Unreliable (connectionless) delivery
• Devices:
• Multilayer switches
• Security appliances like advanced firewalls and IDSs
Give a description of the Session and Presentation Layers
Divisions between upper layers less important in real-world protocols
• Layer 5 (Session)
• Identify a sequence of messages belonging to the same “conversation”
• Dialog control (simplex, half-duplex, or duplex)
• Layer 6 (Presentation)
• Character set conversion
• Compression and decompression support
• Encryption and decryption support
Give a description of Layer 7
Doesn’t encapsulate another protocol
• Top of the stack
• Provides communications protocols and interfaces for software processes
running on different hosts
• Application layer versus software implementation of network functions
• Application programming interfaces (APIs) for software programs
• APIs can be written for any layer of the stack
• Network card drivers (e.g., NDIS) at layer 2 (Data Link)
• Sockets/WinSock at layer 5 (Session)
• High-level API functions (file transfer, email, web browsing, and DNS) at layer 7
Give all the TCP/IP Model Layers
Link/Network Interface layer
• Ethernet/Wi-Fi
• WAN
• Internet layer
• Fragmentation
• IP and ARP
• Transport layer
• TCP and UDP
• Application layer
Explain the difference between Packet-Switched vs. Circuit-Switched Networks
Rather than establish a circuit, data is
broken into packets that can take any
path to their destination
• Robust as can recover from link failures
Give all the TCP and IP standards
Internet Society (ISOC)
• Internet Architecture Board (IAB)
• Internet Engineering Task Force (IETF): Internet and web standards
• Internet Assigned Numbers Authority (IANA)
• IP address allocations and DNS (Domain Name System)
• Regional Registries and Internet Service Providers (ISPs)
• Function of the IANA is contracted to the Internet Corporation for Assigned Names and
Numbers (ICANN)
• Requests For Comments (RFCs)
