![Computer Networks: Introduction 3
Preliminary Definitions
computer network :: [Tanenbaum] a collection of
“autonomous” computers interconnected by a
single technology.
[LG&W] communications network ::a set of equipment and
facilities that provide a service.
[PD] {low level definition} A network can consist of two or
more computers directly connected by some physical
medium such as coaxial cable or an optical fiber.
Wireless connectivity needs to be included in this
definition.](https://image.slidesharecdn.com/introduction06-230201085012-6544f223/85/Introduction06-ppt-3-320.jpg)
Introduction06.ppt
- 1. Computer Networks: Introduction 1 Introduction
- 2. Computer Networks: Introduction 2 Network Definitions and Classification • Preliminary definitions and network terminology • Sample application paradigms • Classifying networks by transmission technology • Classifying networks by size (or scale) • Classifying networks by topology
- 3. Computer Networks: Introduction 3 Preliminary Definitions computer network :: [Tanenbaum] a collection of “autonomous” computers interconnected by a single technology. [LG&W] communications network ::a set of equipment and facilities that provide a service. [PD] {low level definition} A network can consist of two or more computers directly connected by some physical medium such as coaxial cable or an optical fiber. Wireless connectivity needs to be included in this definition.
- 4. Computer Networks: Introduction 4 Network Building Blocks • Nodes and Hosts: computers, routers, switches • Links: coaxial cable, optical fiber, wireless communication – point-to-point – multiple access (a) (b) P&D slide
- 5. Computer Networks: Introduction 5 Preliminary Definitions In a distributed system the collection of independent computers appears to its users as a single coherent system. Namely, the distinctions lie in the transparency in assigning tasks to computers.
- 6. Computer Networks: Introduction 6 Switched Networks P&D slide Figure 1.3
- 7. Computer Networks: Introduction 7 internet P&D slide Figure 1.4 Interconnection of networks
- 8. Computer Networks: Introduction 8 Network P&D recursive definition:: i. two or more nodes connected by a link. or ii. two or more networks connected by a node {an internet}.
- 9. Computer Networks: Introduction 9 12 1 11 8 4 7 2 6 9 10 14 5 13 15 3 Host B Host C Host L Host D Host E Host G Host J Host A Host H Host F Host M 16 17 W T X Y Z nodes AP W1 W2 W3 W4
- 10. Computer Networks: Introduction 10 Sample Application Paradigms
- 11. Computer Networks: Introduction 11 Client-Server Applications Figure 1.1 A network with two clients and one server. Tanenbaum slide
- 12. Computer Networks: Introduction 12 Client-Server Model Figure 1-2. The client-server model involves requests and replies. Tanenbaum slide
- 13. Computer Networks: Introduction 13 Peer-to-Peer Applications Figure 1.3 In a peer-to-peer system there are no fixed clients and servers. Tanenbaum slide
- 14. Computer Networks: Introduction 14 Mobile Network Users Figure 1-5. Combinations of wireless networks and mobile computing. Tanenbaum slide
- 15. Computer Networks: Introduction 15 Classifying Networks by Transmission Technology broadcast :: a single communications channel shared by all machines (addresses) on the network. Broadcast can be either a logical or a physical concept (e.g. Media Access Control (MAC) sublayer ) . multicast :: communications to a specified group. This requires a group address (e.g. – multimedia multicast). point-to-point :: connections are made via links between pairs of nodes.
- 16. Computer Networks: Introduction 16 Network Classification by Size Figure 1-6. Classification of interconnected processors by scale. Tanenbaum slide
- 17. Computer Networks: Introduction 17 Network Classification by Size • LANs {Local Area Networks} – Wired LANs: typically physically broadcast at the MAC layer (e.g., Ethernet, Token Ring) – Wireless LANs • MANs {Metropolitan Area Networks} – campus networks connecting LANs logically or physically. – often have a backbone (e.g., FDDI and ATM)
- 18. Computer Networks: Introduction 18 Ethernet bus Ethernet hub transceivers Figure 1.17 Leon-Garcia & Widjaja: Communication Networks Copyright ©2000 The McGraw Hill Companies Wired LANs Tanenbaum slide
- 19. Computer Networks: Introduction 19 Wireless LANs Figure 1-35. (a) Wireless networking with a base station. (b) Ad hoc networking. Tanenbaum slide
- 20. Computer Networks: Introduction 20 Metropolitan Area Networks Figure 1-8. A metropolitan area network based on cable TV. Tanenbaum slide
- 21. Computer Networks: Introduction 21 Metropolitan network A consists of access subnetworks a, b, c, d. National network consists of regional subnetworks a, b, g. Metropolitan network A is part of regional subnetwork a. A A Hierarchical Network Topology 1* a c b d g 2 3 4 a b Figure 1.8 Copyright ©2000 The McGraw Hill Companies Leon-Garcia & Widjaja: Communication Networks MAN
- 22. Computer Networks: Introduction 22 Network Classification by Size • WANs {Wide Area Networks} – also referred to as “point-to-point” networks. – ARPANET Internet – usually hierarchical with a backbone. – Enterprise Networks, Autonomous Systems (ASs) – VPNs (Virtual Private Networks).
- 23. Computer Networks: Introduction 23 UCLA RAND TINKER USC NBS UCSB HARV SCD BBN STAN AMES AMES McCLELLAN UTAH BOULDER GWC CASE CARN MITRE ETAC MIT ILL LINC RADC Figure 1.16 ARPAnet circa 1972 a point-to-point network Leon-Garcia & Widjaja: Communication Networks Copyright ©2000 The McGraw Hill Companies
- 24. Computer Networks: Introduction 24 Wide Area Networks (WANs) Figure 1-10.A stream of packets from sender to receiver. Tanenbaum slide
- 25. Computer Networks: Introduction 25 G G G G G net 1 net 2 net 3 net 4 net 5 G = gateway G Figure 1.18 Leon-Garcia & Widjaja: Communication Networks Copyright ©2000 The McGraw Hill Companies internet - a network of networks
- 26. Computer Networks: Introduction 26 Network Classification by Topology flow of data Repeater Bus Bidirectional flow assumes baseband cable
- 27. Computer Networks: Introduction 27 Network Classification by Topology Repeater Repeater Ring Note - a ring implies unidirectional flow
- 28. Computer Networks: Introduction 28 Network Classification by Topology Headend Tree
- 29. Computer Networks: Introduction 29 Network Classification by Topology Star hub, switch or repeater
- 30. Computer Networks: Introduction 30 Network Classification by Topology Star AP W1 W2 W3 W4 Wireless Infrastructure