Video Content Lesson 7 Flashcards
OSI Reference Model
Protocols Standards Organizations OSI Overview Logical Data Flow Physical Data Flow
Protocols
Computers need formal rules to communicate
Protocol - Formal set of rules that govern communication
Proprietary protocols only allow communication with similar machines (originally)
Standards Organizations
ISO - International Organization for Standardization (basic communication protocols)
IEEE - Institute of Electrical and Electronics Engineers (low level physical standards)
NSA - National Security Agency (Different levels for security being maintained)
NIST - National Institute for Standards and Technology
ANSI - American National Standards Institute (character sets)
CCITT - International Telegram and Telephone Consultative Committee
OSI Overview
OSI Open Systems Interconnection reference model Developed by ISO (also known as ISO/OSI) Open network architectural guide Specifies how dissimilar systems can communicate 7 distinct protocol layers Application Presentation Session Transport Network Data-link Physical This standard allows developers to write software that works on many dissimilar machines
Logical Data Flow
Flows from one layer on source machine to same layer on target machine (don’t have to worry about what happens in stack below us)
Physical Data Flow
Physically have to go down through every layer below, across medium, and back up each layer to the original layer)
Each Layer adds header and trailer to message (chunked into packets)
OSI Layers
Application Layer Presentation Layer Session Layer Transport Layer Network Layer Data-link Layer Physical Layer TCP-IP Model
Application Layer
Provides services for high-level program (it is NOT the application)
HTTP, FTP, SMTP, EDI, POP3, IMAP, SNMP
Presentation Layer
Provides data representation between systems
GIF, JPEG, MPEG
Responsible for encryption and compression (decryption and decompression)
Session Layer
Manages sessions and synchronizes data flow
NFS, SSL, RPC, Xwindows, AppleTalk
Transport Layer
Responsible for end-to-end transmission integrity
Provides a logical connection between machines
Ensures message delivery
TCP, UDP, SPX
Network Layer
Determines the best way to get data to the destination
Providing Routing Capabilitites
IP, ICMP, IPX, RIP
Data-link Layer
Handles data packet transfer
Handles physical addressing, error handling, and flow control
SLIP, PPP, ARP, RARP, FDDI, ISDN
Physical Layer
Transmits the bit stream onto the physical media
Can use transmission mechanism that is wireless
TCP-IP Model
Developed by the DOD Simplified medel containing 4 layers Application Layer Transport Layer Network Layer Link Layer
Application Layer
All issues specific to a session or application
OSI layers 5, 6, and 7
Transport Layer
Supports moving data between applications
OSI layer 4
Corresponds (supported by) to TCP and UDP protocols
Network Layer
Supports moving data between netowrks
OSI layer 3
Corresponds to IP protocol