INTRODUCTORY COMPUTER

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1 INTRODUCTORY COMPUTER NETWORKS LAYERING Faramarz Hendessi

2 Introductory Computer Networks Lecture 3 Fall 2010 Isfahan University of technology Dr. Faramarz Hendessi 2

3 Layering What is it? Building complex systems is hard! Approach: Divide and conquer. Split job into smaller jobs, or layers. Analogy to other fields. Building a house: digging, foundation, framing, etc. Car assembly line Basic idea: each step dependent on the previous step but does not need to be aware of how the previous step was done.

4 Analogy: Air Travel The problem: air travel. Decomposed into series of steps: Arrival at airport Check-in Boarding Takeoff Departure from airport Baggage claim Deplane Landing Traveling

5 More on the air travel analogy Arrival Departure ing air rport Depart Check-in Boarding Takeoff intermediate air traffic sites Baggage claim Deplane Landing ing air rport Arriv Airplane routing Airplane routing Traveling

6 Protocol Architecture Task of communication broken up into modules For example file transfer could use three modules File transfer application Communication service module Network access module

7 Simplified File Transfer Architecture

8 A Three Layer Model Application Layer Transport Layer Network Access Layer

9 Network Access Layer Exchange of data between the computer and the network Sending computer provides address of destination May invoke levels of service Dependent on type of network used (LAN, packet switched etc.)

10 Transport Layer Reliable data exchange Independent of network being used Independent of application

11 Application Layer Support for different user applications e.g. , file transfer

12 Layered Protocol Design Layering model is a solution to the problem of complexity in network protocols The model divides the network protocols into layers, each of which h solves part of the network communication problem Each layer has its own protocol! Each layer implements a service to the layer above Relying on services provided by the layers below.

13 Layers Layers are the different components that need to be designed/implemented when designing/implementing g/ g networks. Each layer responsible for a set of functions. Top layer relies on services provided by bottom layer. Layer makes it service available to higher layer through an interface.

14 Layering: Logical Communication data E.g.: transport application Take data from transport p application network link Add addressing, physical information. Send result to peer. Analogy: sending a letter. application transport network link physical data application transport network link physical network link physical data application transport p network link physical

15 Layering: Physical Communication data application transport network link physical application transport network link physical application transport network link physical network link physical data application transport network link physical

16 Layers and Protocols The relationship between a service and a protocol.

17 Network/Protocol Architecture Set of layers, what their functions are, the services each of them provide, and the interfaces between them. A.k.a, protocol architecture or protocol stack. Examples: ISO-OSI 7 layer architecture. TCP-IP ac architecture ecue (Internet). e).

18 Protocol Data Units (PDU) At each layer, protocols are used to communicate. At the source, control information is added to user data at each layer, a.k.a., encapsulation. At the receiver, control information is stripped off at each layer going up the stack, a.k.a., a decapsulation.

19 Operation of a Protocol Architecture

20 Example 1: ISO OSI Architecture ISO: International Standards Organization OSI: Open Systems Interconnection. Application Presentation Session Transport Network Data link Physical

21 Layers of Interest in ISO Model Layer 7: Application Application-specific protocols (e.g. ftp, http, smtp) Layer 4: Transport Delivery of data between computers (end-to-end). end). Layer 3: Network Data routing across a network. Layer 2: Data Link Reliable transmission over physical medium. Layer 1: Physical - Transmission of bits between two nodes.

22 OSI Protocol Stack

23 Example 2: TCP/IP Architecture Model employed by the Internet. TCP/IP Application Transport Internet Network Access Physical Application Presentation Session Transport Network Data link Physical ISO OSI

24 TCP/IP Protocol Architecture

25 Messages and Protocol Stack Example: Internet stack source destination Hl Ht HnHt HnHt M M M M application transport network link physical py application transport network link physical py Hl Ht HnHt HnHt M M M M message segment datagram frame

26 TCP/IP

27 Encapsulation TCP Application data IP header MAC header LLC header header MAC trailer MAC frame LLC PDU TCP segment IP datagram

28 The ARPANET The original ARPANET design. IMP = Interface Message Processor (Honeywell DDP-316)

29 The ARPANET Evolution Growth of the ARPANET (a) December 1969 Growth of the ARPANET (a) December (b) July 1970.(c) March (d) April (e) Sept

30 NSFNET The NSFNET backbone in 1988.

31 Internet Usage Traditional applications ( ) News Remote login File transfer

32 Architecture of the Internet

33 The Internet: Some Recent Between 1980 and 2000: the boom! History Internet changed from small, experimental research project into the world s largest network. In 1981, 100 computers at research centers and universities. iti 20 years later, 60M computers! Early 1990 s, the Web caused the Internet revolution: the Internet s killer app! Today: Almost 60 million hosts as of Doubles every year.

System Programming. Introduction to computer networks

System Programming. Introduction to computer networks Content : by Dr. B. Boufama School of Computer Science University of Windsor Instructor: Dr. A. Habed adlane@cs.uwindsor.ca http://cs.uwindsor.ca/ adlane/60-256 Content Content 1 Introduction to Computer