1 / 19

Protocol Layering

Sender. Receiver. Layer N. Layer N. Layer 2. Layer 2. Layer 1. Layer 1. Network. Protocol Layering. Motivation for Protocol Layering - The Programming Language Analogy. Computer programming: Program -> Compiler -> Assembly Code -> Assembler -> Machine Code -> Hardware

cardea
Download Presentation

Protocol Layering

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Sender Receiver Layer N Layer N . . . . . . Layer 2 Layer 2 Layer 1 Layer 1 Network Protocol Layering

  2. Motivation for Protocol Layering - The Programming Language Analogy • Computer programming: • Program -> Compiler -> Assembly Code -> Assembler -> Machine Code -> Hardware • Internet programming: • Application -> Transport Protocol -> Connectionless Datagram Delivery Protocol -> Physical Network

  3. The Internet Protocol Suite • Internetworking does not use a single protocol to transmit data • Imagine how hard it would be to write one that: • Ran on all underlying network technologies • Transmitted and routed all traffic on the internet • Handled: hardware failure, network congestion, delays, data loss, data corruption, data duplication, sequencing errors • Internetworking uses a set of cooperating protocols (each with its own job)

  4. Benefits of Protocol Layering • Complexity hidden from application-level programmer • Physical network details hidden in low-level protocols • Each layer of software can be written, tested, and modified independently

  5. Sender Receiver Layer N Layer N . . . . . . Layer 2 Layer 2 Layer 1 Layer 1 Network Protocol Layering • Each layer provides services to the layer above and utilizes services from the layer below

  6. Send Recv Layer N Layer N . . . . . . Network (IP) Network (IP) Network 1 Network 2 Network 3 Data Link Layer Data Link Layer Data Link Layer Data Link Layer Physical Layer Physical Layer Physical Layer Physical Layer Protocol Layering • The path of a datagram:

  7. 7 6 Transport Layer Network Layer Data Link Layer Physical Layer Session Layer Presentation Layer Application Layer 5 4 3 2 1 Functionality of the Layers • ISO 7-Layer Reference Model:

  8. ISO 7-Layer Reference Model • Physical Layer (ISO Layer 1) • Service: transmission of a raw bit stream over a communication channel ensuring a reliable delivery of 0’s and 1’s • Functions: conversion of bits into electrical or optical signals • Examples: X.21, RS-232-C

  9. ISO 7-Layer Reference Model • Data Link Layer (ISO Layer 2) • Service: reliable transfer of frames over a link • Functions: synchronization, error control, flow control • Examples: HDLC, CCITT, LAP-D • Network Layer (ISO Layer 3) • Service: provide switching and routing functions to transfer data between hosts • Functions: routing, addressing, switching, congestion control • Examples: IP, X.25, CLNP

  10. ISO 7-Layer Reference Model • Transport Layer (ISO Layer 4) • Service: control delivery of messages between hosts • Functions: connection management, error control, flow control, multiplexing • Examples: TCP, UDP, ISO TP0 - TP4 • Session Layer (ISO Layer 5) • Service: support communication between cooperating application programs • Functions: session management, synchronization, recovery • Examples: ISO session protocol, RPC

  11. ISO 7-Layer Reference Model • Presentation Layer (ISO Layer 6) • Service: handle compatibility issues • Functions: virtual device support, syntax conversion, cryptography • Examples: ASN.1, ISO presentation protocol • Application Layer (ISO Layer 7) • Service: provide network access to application programs • Functions: (application specific) • Examples: Telnet, FTP, E-mail, WWW

  12. ISO 7-Layer Reference Model • Designed by committee - International Organization for Standardization (ISO) • Reference model, not an implementation • Implemented by a set of protocols known as X.25

  13. Network Interface Layer Hardware Internet Layer Transport Layer Application Layer Messages or Streams Transport Protocol Packets IP Datagrams Network-Specific Frames TCP/IP Internet Layering Model • Functionality of the layers Objects Passed Between Layers Conceptual Layer

  14. TCP/IP Internet Layering Model • Network Interface Layer (TCP/IP Layer 1) • Service: accepts IP datagrams and transmits them over a specific network • Functions: conversion of datagrams to physical frames • Examples: device drivers • Internet Layer (TCP/IP Layer 2) • Service: connectionless datagram delivery • Functions: inter-host communication, routing • Examples: IP

  15. TCP/IP Internet Layering Model • Transport Layer (TCP/IP Layer 3) • Service: provide reliable end-to-end communication • Functions: flow control, sequencing, acknowledgments • Examples: TCP • Application Layer (TCP/IP Layer 4) • Service: (application specific) • Functions: (application specific) • Examples: Telnet, FTP, E-mail, WWW

  16. Internet Model vs. ISO Model • Similarities • Differences

  17. Application Transport Internet Network Interface Transport Internet Network Interface The Protocol Layering Principle “Layered protocols are designed so that layer N at the destination receives exactly the same object sent by layer N at the source.” Application Identical message Identical packet Identical datagram Identical frame Network

  18. Conceptual Layer Network Interface Layer Internet Layer Transport Layer Application Layer Hardware Boundaries in the TCP/IP Model Boundary Software outside the operating system Software inside the operating system Only IP addresses used Physical addresses used

  19. Protocol Layering • Advantages • Disadvantages

More Related