OSI vs Other Network Models - korachi-9090/wiki GitHub Wiki

OSI vs Other Network Models

While the OSI Reference Model provides a comprehensive theoretical framework, other network models have had greater practical implementation. Understanding the differences helps networking professionals bridge theoretical knowledge with real-world applications.

OSI vs TCP/IP Model

Key Differences

  • The OSI model has 7 layers; TCP/IP has 4 layers
  • OSI was developed by ISO as a theoretical framework; TCP/IP evolved from practical implementation
  • OSI separates functions into more distinct layers; TCP/IP combines several functions
  • TCP/IP was widely implemented before OSI was formalized
  • TCP/IP protocols dominate real-world networking; few pure OSI protocols exist

Layer Comparison

OSI Model TCP/IP Model Primary Functions
ApplicationPresentationSession Application End-user services, data representation, session management
Transport Transport End-to-end communication, segmentation, flow control
Network Internet Logical addressing, routing between networks
Data LinkPhysical Network Access Physical addressing, media access, physical transmission

Practical Implications

  • TCP/IP is what actually runs on networks
  • OSI provides more precise terminology and conceptual breakdown
  • Security professionals often use OSI terms even when discussing TCP/IP networks
  • Troubleshooting typically follows OSI model even in TCP/IP environments

Other Historical Network Models

IBM's SNA (Systems Network Architecture)

  • Proprietary model developed by IBM in 1974
  • Hierarchical rather than peer-to-peer architecture
  • Mainframe-centric approach
  • Primarily used in IBM environments before TCP/IP adoption

Novell's IPX/SPX

  • Used primarily in Novell NetWare environments
  • Faster than early TCP/IP implementations
  • Eventually replaced by TCP/IP in the late 1990s
  • More efficient for LAN environments before TCP/IP optimizations

Apple's AppleTalk

  • Developed for early Macintosh networking
  • Simple to configure with automatic addressing
  • Limited scalability to small networks
  • Phased out in favor of TCP/IP

Modern Adaptations

SDN (Software-Defined Networking) Model

  • Separates control plane and data plane
  • Centralizes network intelligence
  • Abstracts infrastructure from applications
  • Conceptually maps to OSI but with different organizational principles

5G Network Architecture

  • Service-based architecture
  • Network slicing concepts
  • Virtualized network functions
  • Incorporates concepts from OSI but organized differently

Why Multiple Models Matter

  • Different models optimize for different priorities
  • Historical context helps understand design decisions
  • Comparing models reveals essential vs. arbitrary distinctions
  • Cross-model understanding aids in protocol analysis

Related Topics

Back to OSI Reference Model