Grundlagen der Rechnernetze. Introduction

Transcription

1 Grundlagen der Rechnernetze Introduction

2 Overview Building blocks and terms Basics of communication Addressing Protocols and Layers Performance Historical development Grundlagen der Rechnernetze Introduction 2

3 Building blocks and terms Grundlagen der Rechnernetze Introduction 3

4 Hosts and links H1 H2 Link Host Grundlagen der Rechnernetze Introduction 4

5 Hosts and links H1 H2 Link Host Host is a computer or more general a device that communicates with the other host on a network Link is (in the context of computer networks) connection between two hosts Point to point connection designates communication connection between two hosts (nodes) or endpoints Grundlagen der Rechnernetze Introduction 5

6 Types of communication Simplex Half duplex Duplex (full duplex) Source: half duplex full duplex/ Grundlagen der Rechnernetze Introduction 6

7 Medium Wired communication Wireless communication Light(?) Sound (ultrasound) Grundlagen der Rechnernetze Introduction 7

8 Communication channel between the nodes Communication channel refers to a physical transmission medium (wired or wireless) but it also covers logical connection over multiplexed medium Grundlagen der Rechnernetze Introduction 8

9 Message, stream, packet [1] M H1 H2 H3 S H4 P 1 P 2 P n Header Payload Trailer Bytes First Bit Last Bit Grundlagen der Rechnernetze Introduction 9

10 Message, stream, packet Message Communication primitive, usually consists of multiple packets; usually used in the higher layers of communication Stream A sequence of signals that we use to transmit data Packet Formatted unit of data consisting of user data and control data (header and trailer). Essentially a part of a message; several packets together form a message Grundlagen der Rechnernetze Introduction 10

11 Multiple access H 1 H 2 H 3 H n Collision domain A network connected by a shared medium; in this network packets may collide with one another when they are sent. A term coming from early versions of Ethernet and wireless networks Single hop communication Basically communication within one collision domain; packet reaches destination within one hop Grundlagen der Rechnernetze Introduction 11

12 Multiplexing [1] H 1 H 4 H 2 H 5 H 3 H 6 H 1 H 4 H 2 H 5 H 3 H 6 Grundlagen der Rechnernetze Introduction 12

13 Multiplexing [2] Static multiplexing (predefined) Statistical multiplexing (can adapt over time) Queueing Packet scheduling the way of controlling packet transmission Grundlagen der Rechnernetze Introduction 13

14 Scalability of computer networks Scalability how networks adapt to the grow of load? how networks adapt to the increase of hosts? how networks adapt to the increase of links? Grundlagen der Rechnernetze Introduction 14

15 Scalability of multiple access networks H 1 H 2 H 3 H n Assuming that all node pairs communicate the same number of times. What is the share s of the medium per node pair? Grundlagen der Rechnernetze Introduction 15

16 Scalability of multiple access networks H 1 H 2 H 3 H n Assuming that all node pairs communicate the same number of times. What is the share s of the medium per node pair? Grundlagen der Rechnernetze Introduction 16

17 Scalability of fully connected network H11 H1 H2 What is the number of links k per node and total number of links l? H10 H3 H9 H4 H8 H7 H6 H5 Grundlagen der Rechnernetze Introduction 17

18 Scalability of fully connected network H11 H1 H2 What is the number of links k per node and total number of links l? H10 H3 H9 H4 H8 H7 H6 H5 Grundlagen der Rechnernetze Introduction 18

19 Switched network H8 H1 H2 H3 S1 Switch a network device that provides dedicated communication between the hosts Switched network computer network that uses network switches S2 S3 S4 H4 H7 S5 H6 H5 Grundlagen der Rechnernetze Introduction 19

20 Switched network H1 H2 H3 Packet switched network a type of network that uses packets for communication; packet switching is a form of grouping of the data sent over the network; in here network links can be shared H8 H7 S2 S1 S3 S4 H4 Circuit switched network a dedicated communication channel (circuit) is established between two hosts; in here network links are dedicated to one specific communication between the hosts S5 H6 H5 Grundlagen der Rechnernetze Introduction 20

21 Switched network H8 H1 H2 H3 S1 Store and forward a packet is sent to an intermediate station where it can be either kept or forwarded Cut through switching a bigger chunk of the data (frame) is forwarded in smaller pieces even before the whole chunk is received H7 S2 S3 S4 H4 Multi hop communication using multiple stations to transmit data between two hosts S5 H6 H5 Grundlagen der Rechnernetze Introduction 21

22 Cloud representation Grundlagen der Rechnernetze Introduction 22

23 Internet [1] H1 H2 H3 N1 H9 R1 R2 H4 N3 N2 H8 R3 H5 H7 H6 Grundlagen der Rechnernetze Introduction 23

24 Internet [2] What is internet? Router Network interface The Internet and a internet Physical network Intranet Grundlagen der Rechnernetze Introduction 24

25 Recursive use of cloud representation H1 H2 H3 N1 H9 N3 R1 N R2 N2 H4 H8 R3 H5 H7 H6 Grundlagen der Rechnernetze Introduction 25

26 Network sizes LAN local area network WAN wide area network MAN metropolitan area network; larger than local area network (LAN) but smaller than the area covered by a wide area network (WAN). SAN storage area network is a high speed network of storage devices that also connects those storage devices with servers. CAN Controller Area Network (also known as CAN bus) is a vehicle bus standard designed to allow microcontrollers and devices to communicate with each other in applications without a host computer. PAN personal area network; network of localized and personalized devices. GAN global area network; connecting everything. Grundlagen der Rechnernetze Introduction 26

27 Network sizes Source: 01 GAN MAN.html Grundlagen der Rechnernetze Introduction 27

28 Networks and graphs [1] H1 H2 H3 H1 H2 H3 R1 N1 R2 H4 R1 N1 R2 H4 H9 H8 N3 R3 N2 H5 H9 N3 R3 N2 H5 H7 H6 H8 H7 H6 Grundlagen der Rechnernetze Introduction 28

29 Networks and graphs [2] Nodes Links Topology Formal definition of a network graph: Grundlagen der Rechnernetze Introduction 29

30 Topology examples Bus Tree Star Ring Mesh Grundlagen der Rechnernetze Introduction 30