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OSI-, Hybrid und TCP/IP-Referenzmodell @@ -20,8 +20,143 @@ - TCP Flusskontrolle und Sliding Window - TCP Fehlerbehandlung durch Go-Back-N und Selective Repeat - TCP Slow Start und Congestion Avoidance -- FLow Control versus Congestion Control +- Flow Control versus Congestion Control - Silly-Window-Problem und Lösungen (Clarke und Nagle) - Gute Abschätzungen für TCP Timeout (Jacobson/Karels) - HTTP1.1 und HTTP2 über TLS und TCP -- HTTP3 über (TLS1.3 und QUIC) über UDP \ No newline at end of file +- HTTP3 über (TLS1.3 und QUIC) über UDP + +## Wertschöpfung für Anwendungen +![image_557.png](image_557.png) + +## Technik der Netze +> Pakete = konvergente Verpackung von Daten + +![image_559.png](image_559.png) + + +## IP Header +### IPv4 +![image_560.png](image_560.png) + +### IPv6 +![image_561.png](image_561.png) + +### Vergleich IPv4 IPv6 +![image_562.png](image_562.png) + +#### IPv6 Header + +| Version | Traffic Class / Flow Label | Payload Length | Next Header | Hop Limit | +|----------|----------------------------|-------------------------------|---------------------------------------------------------|-----------------| +| wie IPv4 | Unterstützung von [QoS](#qos-parameter) | Paketlänge ohne Header [Byte] | wie "Protocol" in IPv4 / Typ des 1. Erweiterungsheaders | wie TTL in IPv4 | + + +## QoS Parameter +### Throughput +- [bytes/s] +- min/max/avg benötigter Durchsatz + +### Packet Loss +### Delay +- [ms] +- max tolerierbare Verzögerung +- One-Way-Delay +- Round-Trip-Delay (RTT) + +### Jitter (=Delay Variation) +- [ms] +- Welche Fluktuationen in der Verzögerung sind akzeptierbar? + +### Availability +- [%] +- Mit welcher Wahrscheinlichkeit ist der Service verfügbar? + - manchmal "five times 9" = 99,999% der Zeit + + +## Schichtenmodelle +### Internet +![image_563.png](image_563.png) + +### ISO-OSI 7-Schichtenmodell + +| | | +|---------------------------------------------|---------------------------------| +| [Anwendung](#7-application-layer) | ![image_564.png](image_564.png) | +| [Präsentation](#6-presentation-layer) | ![image_565.png](image_565.png) | +| [Kommunikationssteuerung](#5-session-layer) | ![image_566.png](image_566.png) | +| [Transport](#4-transport-layer) | ![image_567.png](image_567.png) | +| [Verbindung/Vermittlung](#3-network-layer) | ![image_568.png](image_568.png) | +| [Sicherung](#2-data-link-layer) | ![image_569.png](image_569.png) | +| [Bitübertragung](#1-physical-layer) | ![image_570.png](image_570.png) | + +#### Schichten +##### 1. Physical Layer +- **ungesicherte** Verbindung zwischen Systemen +- Übertragung unstrukturierter Bitfolgen über physikalisches Medium +- Physikalischer Anschluss, Umsetzung der Daten in Signale + +##### 2. Data Link Layer +- gesicherter Datentransfer zwischen **direkt verbundenen** Dienstnehmern + - Punkt-zu-Punkt-Übertragung +- Zerlegung des Bitstroms ([1. Schicht](#1-physical-layer)) in Rahmen (_frames_) +- **Fehlererkennung /-behebung**, Bestätigungsrahmen + +##### 3. Network Layer +- Logische Adressierung des Zielsystems, Fragmentierung +- Wegewahl (Routing → **Internetworking**), Vermittlung, Staukontrolle + +##### 4. Transport Layer +- (fehlerfreier) Datentransfer **von Endpunkt zu Endpunkt** +- bietet Transparenz bzgl. Übertragungs- und Vermittlungstechnik + +##### 5. Session Layer +- Ablaufsteuerung und -koordinierung (Synchronisation im weitesten Sinn) +- **Kommunikationsbeziehung als Sitzung**, Dialogsteuerung +- Verbindungsaufbau / -abbau, Durchführung und Flusskontrolle + +##### 6. Presentation Layer +- Datendarstellung von Informationen (Syntax, Semantik) + - _Konvertierung EBCDIC ↔ ASCII_ + - _Entschlüsselung_ +- Kommunikation ermöglichen trotz **unterschiedlicher lokaler Datenformate** der Teilnehmer bzw. Endgeräte + +##### 7. Application Layer +- macht OSI-Benutzer Dienste verfügbar +- stellt unterschiedliche **Dienste** bereit + - _Dateitransfer, zuverlässiger Datenaustausch, entfernter Prozduraufruf_ + - _HyperText Transfer Protocol (HTTP) für Webbrowser_ + +##### (8. User) + + + +#### Darstellungen OSI-Modell +![image_572.png](image_572.png) + +![image_573.png](image_573.png) + +![What is the OSI Model.webp](What is the OSI Model.webp) + +#### OSI-Modell und TCP/IP-Suite +![image_574.png](image_574.png) + +### Hybrid-Referenzmodell +#### OSI vs. Hybrid +![image_575.png](image_575.png) + +![image_576.png](image_576.png) + +#### Hybrid-Modell: Schnittstellen +![image_577.png](image_577.png) + +##### Treiber +> Schnittstelle zwischen Betriebssystem und Hardware, +> werden i.d.R. vom Hersteller der Hardware bereitgestellt + +##### Sockets +> Schnittstelle zwischen Betriebssystem und Anwendung, +- Implementierung als Teil des Kernels oder als separate Bibliothek +- Kombination von IP-Adresse und Port + +![image_578.png](image_578.png) \ No newline at end of file