Grundlagender Rechnernetze - Uni Koblenz-Landau

Grundlagen der RechnernetzeIntroduction

Overview

• Building blocks and terms• Basics of communication• Addressing• Protocols and Layers• Performance• Historical development

Grundlagen der Rechnernetze ‐ Introduction 2

Building blocks and terms


Hosts and links


H1 H2

Host

Link

Hosts and links


H1 H2

Host

Link

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

Types of communication

• Simplex• Half‐duplex• Duplex (full duplex)


Source: http://mikrotik.tips/simplex‐half‐duplex‐full‐duplex/

Medium

• Wired communication• Wireless communication• Light(?)• Sound (ultrasound)


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


Message, stream, packet [1]


SH1 H2 H3 H4M

P1 P2 Pn…

PayloadHeader Trailer

First Bit Last Bit

Bytes

Message, stream, packet


Message Communication primitive, usually consists of multiple packets; usually used in the higher layers of communication

StreamA sequence of signals that we use to transmit data

PacketFormatted 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

Multiple access


H1 H2 H3 Hn…

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 communicationBasically communication within one collision domain; packet reaches destination within one hop

Multiplexing [1]


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Multiplexing [2]

• Static multiplexing (predefined)• Statistical multiplexing (can adapt over time)• Queueing• Packet scheduling – the way of controlling packet transmission


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?


Scalability of multiple access networks


H1 H2 H3 Hn…

Assuming that all node pairs communicate the same number of times. What is the share s of the medium per node pair?

Scalability of multiple access networks


H1 H2 H3 Hn…

Assuming that all node pairs communicate the same number of times. What is the share s of the medium per node pair?

Scalability of fully connected network


H1H2

H3

H5

H4H9

H8H6H7

H10

H11What is the number of links k per node and total number of links l?

Scalability of fully connected network


H1H2

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H11What is the number of links k per node and total number of links l?

Switched network


H1 H2 H3

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H6 H5

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S1

S2 S4S3

S5

Switch – a network device that provides dedicated communication between the hosts

Switched network – computer network that uses network switches

Switched network


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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

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

Switched network


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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

Multi‐hop communication – using multiple stations to transmit data between two hosts

Cloud representation


Internet [1]


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Internet [2]

• What is internet?• Router• Network interface• The Internet and a internet• Physical network • Intranet


Recursive use of cloud representation


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N

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.


Network sizes


Source: www.cebylon.com/khi1/141‐01‐GAN‐MAN.html

Networks and graphs [1]


N1

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N3R3

Networks and graphs [2]

• Nodes • Links• Topology


Formal definition of a network graph:

Topology examples


Bus Tree

Star Ring Mesh

Grundlagender Rechnernetze - Uni Koblenz-Landau

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