Network Architectures: Topologies, Protocols, and Technologies
Key Network Architecture Features
Network architecture is defined by three key features:
- Topology: The organization of your wiring, defining the basic configuration of station interconnection.
- Access Methods: All networks have a shared medium (or a method for non-shared mediums) to manage information transmission.
- Communication Protocols: Rules and procedures used for network communication, error correction, and connection establishment.
Protocols are categorized as high-level (for communicating applications) and low-level (defining signal communication). Intermediate protocols handle functions like error control and congestion management.
Tiered Architecture Characteristics
- Each layer requires specific services defined by standard protocols.
- Each layer communicates only with the adjacent higher and lower levels.
- Lower levels provide services to higher levels.
OSI Reference Model
Physical Layer:
Handles the transmission of binary digits over a communication channel.
Link Layer:
Detects and corrects communication line errors, manages sender/receiver saturation, and controls shared medium access.
Network Layer:
Determines optimal routes for information transmission, manages network congestion, and adapts messages between different networks.
Transport Layer:
Ensures reliable end-to-end data delivery between the network and session layers.
Session Layer:
Establishes and manages communication sessions between two endpoints, including resuming after interruptions.
Presentation Layer:
Translates data between stations (e.g., different encoding), and handles data encryption/decryption.
Application Layer:
Provides network services to applications (e.g., FTP, DNS, Telnet).
TCP/IP Architecture
Subnet Layer:
Specifies the protocol for connecting stations to the network, adapting to different technologies.
Internet Layer:
Manages packet transmission across networks, including routing and reordering at the destination. IP (Internet Protocol) is the primary protocol.
Transport Layer:
Handles error control and message management.
Application Layer:
Contains high-level protocols used by applications (e.g., Telnet, FTP, HTTP, email).
Microsoft Networks
Designed for coexistence with other architectures (TCP/IP, Novell). Supports various transport protocols.
- NetBios Protocol: Uses computer names for identification and resource sharing via diffusion.
- SMB (Server Message Block): Application-level protocol for file operations using NetBios services.
- NetBEUI (NetBIOS Extended User Interface): Extends NetBIOS for Windows workstations at the network and transport levels.
Switched Telephone Network (PSTN)
Initially for voice transmission via manual connection, later automated with PABX systems. Services include real-time voice, call waiting, multiple numbers, call forwarding, etc.
Iberpac
Spanish data transmission network using X.25 protocols (physical, link, and network levels) for reliable, albeit slower, communication. Expected to be replaced by Frame Relay.
Integrated Services Digital Network (ISDN)
Offers voice, data, image, and real-time sound transmission. Uses its own cable network and requires special adapters. Supports multiple logical channels for varying speeds and capacities (64kbps-128kbps). Uses 15-digit decimal addresses.
Internet
A global network of interconnected networks and computers.
- Transit/International Networks: Interconnect provider networks.
- Regional Networks and Connectivity Providers: Connect end-users to transit networks.
- End-User Networks: Individual computers or private corporate networks (LANs).
DSL
Uses PSTN for high-speed transmission. ADSL (Asymmetric Digital Subscriber Line) is a common variant with asymmetric speeds. Employs electronic circuitry to mitigate interference.
Virtual Private Networks (VPN)
Interconnects networks using a WAN like the Internet, reducing costs and providing security. Creates a virtual communication environment for seamless user experience.
FDDI
(Fiber Distributed Data Interface) High-speed, high-capacity, and reliable network using fiber optics. Transmits at 50-100 Mbps and supports up to 1000 stations. Uses a double-ring topology for redundancy (standard 802.5).
Token Ring
Uses a physical star topology with internal ring logic. Supports twisted pair, fiber optics, or coaxial cable. Transmission speeds range from 4-16 Mbps. Less common now due to Ethernet’s popularity.