grundlagender rechnernetze - uni koblenz-landau
TRANSCRIPT
Overview
• Building blocks and terms• Basics of communication• Addressing• Protocols and Layers• Performance• Historical development
Grundlagen der Rechnernetze ‐ Introduction 2
Hosts and links
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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)
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Source: http://mikrotik.tips/simplex‐half‐duplex‐full‐duplex/
Medium
• Wired communication• Wireless communication• Light(?)• Sound (ultrasound)
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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
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Message, stream, packet [1]
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PayloadHeader Trailer
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Bytes
Message, stream, packet
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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
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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
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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?
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Scalability of multiple access networks
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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
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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
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Scalability of fully connected network
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Switched network
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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
Internet [1]
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Internet [2]
• What is internet?• Router• Network interface• The Internet and a internet• Physical network • Intranet
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Recursive use of cloud representation
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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.
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Network sizes
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Source: www.cebylon.com/khi1/141‐01‐GAN‐MAN.html
Networks and graphs [1]
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Networks and graphs [2]
• Nodes • Links• Topology
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Formal definition of a network graph: