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Communications Architectures

Communications Architectures. Peer-to-peer Client/server OSI reference model LAN communications Frames WAN communications. Communications Architecture. Definition A system of rules and practices that enables computers to share information over a network Protocols

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Communications Architectures

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  1. Communications Architectures • Peer-to-peer • Client/server • OSI reference model • LAN communications • Frames • WAN communications

  2. Communications Architecture • Definition • A system of rules and practices that enables computers to share information over a network • Protocols • Protocols (rules) are combined to construct a communications architecture

  3. Network Operating System (NOS) • The NOS operating on a network server handles requests by users to carry out simultaneous requests for service and to provide secure file sharing

  4. Peer-to-PeerCommunications Architecture • Every PC on the network has the same resources and level of responsibility • Advantage: PCs share printers, hard drives, application programs, and databases so all peers have access to all resources • Disadvantage: PCs share everything, so there is less control over privacy and productivity

  5. Typical Peer-to-Peer Architecture

  6. Client/Server Architecture • One or more server computers are designated to serve other computers by providing resources

  7. Client/Server Advantages • Server carries burden of sharing resources • Clients are free for individual processing • Upgrades and installations occur only on the server • Private and secure for clients

  8. Typical C/S Architecture

  9. Typical Client Software Environment

  10. Protocol • A set of rules that two devices must follow to communicate and exchange information

  11. Protocol Stack • The chain of protocols that together constitute the rules of a communications architecture

  12. OSI Reference Model

  13. Layer 1: Physical • Electrical, mechanical, functional, and procedural hardware specifications to connect a device to the network • EIA/TIA standard 232-E • NIC • Repeater connects LAN segments • ISO/IEC standard 8802-3

  14. Layer 2: Data Link • Procedures that are followed to achieve reliable point-to-point information transfer between two network devices • LLC • MAC • CSMA/CD • A bridge connects two segments of a LAN

  15. Layer 3: Network • Provides the mechanisms for transporting a packet from the source network to the destination network • Packet: The message processed by the network and higher layers of the protocol stack • Router: Passes the packet to another network to move it closer to its destination

  16. Layer 4: Transport • Provides reliable and unreliable transport protocols • Reliable: Transport Control Protocol (TCP) • Unreliable: User Datagram Protocol (UDP) • Port: A number that serves as an ID for a process that receives or sends a packet

  17. Layer 5: Session • Provides the mechanisms to open and close multiple logical connections between processes on different PCs

  18. Session Layer Function

  19. Layer 6: Presentation • Provides an interface between the Application layer and the layers below the Presentation layer • Transfer syntax • Basic Encoding Rules (BER) • Abstract syntax notation.1 (ASN.1) • Virtual Terminal Protocol

  20. Layer 7: Application • Contains software that provides common services needed by an application • File Transfer Protocol (FTP)

  21. Communication Services

  22. Comparison

  23. LAN Communication • Coaxial cable • Optical fiber cable • Twisted pairs of wires • Wireless

  24. Ethernet LANs

  25. 10BASE2 Ethernet Specifications

  26. 10BASE2 • The cable operates at 10 Mbs • Uses baseband • Maximum length of a segment without repeaters is 185 meters • 10BASET uses twisted pair

  27. 10BASET Ethernet Configuration

  28. 10BASET • Hub: A multiport repeater • Twisted pairs • Forms a LAN with the transceiver in the PC and the transceiver in the hub

  29. Bridge Connecting Two LAN Segments

  30. Frames • A message that a computer sends to another computer over an interconnecting medium • Bits of 1 (one) or 0 (zero) • Transmitted over Ethernet LAN at 10 million bits per second • A header tells the peer layer in the destination computer how to process the packet it receives

  31. Steps in the Process

  32. Communication Between PCs

  33. Encapsulation and De-encapsulation • Encapsulation: Enclosing one layer inside another layer, like the layers of an onion • De-encapsulation: removing the layers of the onion

  34. Ethernet II Frame

  35. Fields in the Ethernet II Frame

  36. WAN Communications • Enterprise networks (intranets) provide global connectivity • Independent or part of the Internet • Modem, T1 lines, optical fiber lines, or microwave connections • Routers

  37. Simple Company Intranet

  38. Chapter Summary • Peer-to-peer and client/server network communications • Use peer-to-peer architecture for small networks (sharing files and programs) • Use client/server architecture when users need centralized storage, management, and security • Protocol stacks and layers

  39. Chapter Summary, cont. • Ethernet LANs, LAN communications media, CSMA/CD medium access method, structure of frames • A LAN is constructed using a twisted pair medium that requires a hub to connect the computers • A bridge connects segments of a LAN • A router connects a LAN to a WAN

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