Computer Networking

Application Layer
1. Overwiew
  1. Transport services available to applications
    1. Security
      1. Encryption
      2. Decryption
    2. Reliable data transfer
    3. Timing
    4. Throughput
  2. Client / Server
  3. Peer-to-peer
2. Application Layer Protocols
  1. HTTP - HyperText Transfer Protocol
    1. Non-Persistant Connection
      1. One handshake for each object
    2. Persistant Connection
      1. One handshake for all objects
    3. Web Cashing
    4. Pull protocol
  2. SMTP - Simple Mail Transfer Protocol
    1. Push protocol
    2. POP3 - Post Office Protocol v.3
    3. IMAP - Internet Mail Access Protocol
  3. DNS - Domain Name Service
    1. DNS Cashing
    2. Non DNS Cashing
    3. Root DNS servers
      1. .com DNS server
        Amazon.com DNS servers
      2. .no DNS servers
        vg.no DNS servers
      3. .ord DNS servers
        pbs.org DNS Servers
  4. Peer-to-peer
    1. Bittorrent
      1. Tracker
        For each torrent
      2. Algorithm
        Rarest First
Transport Layer
1. Analogy
  1. Two houses on different sides of a country
2. Multiplexing
  1. Add Socket
    1. Dest. port
    2. Source port
    3. Application layer data
    4. Other header flields
3. Demultiplexing
  1. Remove socket
    1. Application layer data
    2. Source port
    3. Dest. port
    4. Other header fields
4. Reliable Data Transfer
  1. Finale State Machine
    1. Checksum
    2. Positive and Negative acknowledgements
      1. Duplicated ACKs
    3. Secuence Numbers
    4. Countdown Timer
5. Transport Layer Protocols
  1. UDP - User Datagram Protocol
    1. UDP segment structure (32 bit)
      1. Header
        Length
        Checksum
        Provides, but does not do anything to recover from an error
        Dest. port
        Source port
      2. Data
        Application Data (message)
    2. No establishment of connection
  2. TCP - Transport Control Protocol
    1. Three-way Handshake
      1. SYN
        SYN ACK
        ACK
    2. MSS - Maximum Segment Size
      1. 1460 bytes
    3. TCP Serivce Quality
      1. Reliable Data Transfer
      2. In order data delivery
6. TCP Connection Management
7. Network Control
  1. Flow Control
    1. Control to not overflow memory in sender and receiver
    2. Control the flow of the internet
  2. Congestion Control
    1. Guiding pricible
      1. Lost segment
        Timeout
        Loss Event
        Decrease sender`s rate of segments
        4 duplicate ACK
        Loss Event
        Decrease sender`s rate of segments
      2. ACK segment arrives
        Increase sender`s rate
    2. Congestion Control Protocols
      1. Congestion Avoidance
      2. Fast Recovery
      3. Slow Start
Network Layer
1. Overview
  1. Forwarding
    1. The fastest path for that spesific datagram.
  2. Routing
    1. Every step and desition on the way. Every little switch that takes place
  3. Local Forwarding table
    1. In every router. Exhange between routers to know whitch way is the fastest.
  4. Network Service Model
    1. Best-effort Service
2. Data Plane
  1. Router
    1. Inside the router
      1. Input Port
      2. Switching fabric
        Methodes to switch packets
        Memory
        Bus
        Interconnected Network
      3. Output Port
    2. Queuing
      1. Input port
        Switch fabric capasity to switch < Input Port`s processing speed
      2. Output Port
        Switch fabric capasity to switch > Output Port`s processing speed
    3. Forwarding
      1. Destination Based Forwarding
        Forward be knowing the destination of a spesific package
      2. Generalized Forwarding
        Forward by knowing more information than just the destination
  2. Packet Scheduling
    1. FIFO - First in First Out
    2. Priority Scheduling
    3. Round Robin
    4. WFQ - Weighted Fair Queuing
  3. IP-addresse
    1. IPv4 - Internet Protocol version 4
      1. IPv4 Datagram (32 bit)
        Version number
        Header length
        Type of service
        Identifier flags, Fragmentation offset
        Protocol
        Source and Destination - IP-adresse
        Data (segment)
        Options
        Time to live
        Datagram length
        Header checksum
      2. Fragmentation
      3. 192.32.216.9 = 11000001.00100000.11011000.00001001
    2. DHCP
      1. DHCP server discovery
      2. DHCP server offcer(s)
      3. DHCP request
      4. DHCP ACK
    3. IPv6 - Internet Protocol version 6
      1. No fragmentation
      2. No checksum
      3. No options
      4. IPv6 Datagram (128 bit)
        Flow Lable
        Payload length
        Traffic Class
        Next header
        Hop limit
        Version
        Source and destination addresse
        Data
      5. Tunneling
3. Control Pane
  1. Per-router control
    1. BGP - Border Gate Protocol
    2. OSPF - Open Shortest Path First
    3. Routing is computed in each node
  2. Logically centralized control
    1. CA - Control Agents
      1. Communicate with Controller
    2. Routing is not computed at each node
  3. Routing Algorithm
    1. LS - Link state
      1. Dijkstras
      2. Needs to know link status of every node in the network
    2. DV - Distant Vector
      1. Each node talk to only its directly connected neighbors
    3. AS - Autonomous Systems
      1. Intra-AS routing protocol
        OSPF - Open Shortest Path First
        Dijkstra algorithm
        Internal
      2. Inter-AS routing protocol
        BGP - Border Gate Protocol
        BGP Connection
        eBGP - External BGP
        iBGP - Internal BGP
        External
Link layer
Physical Layer
Overview
1. Packet Switching
  1. Allocalte on Demand
2. Circut Switching
  1. Pre allocated shared recourses
3. Encapsulation
4. Internet Protocol Stack
  1. Mega Stor Drage Fanger
    1. Message
    2. Segment
    3. Datagram
    4. Frame
  2. Application Layer
  3. Transport Layer
  4. Network Layer
  5. Link Layer
  6. Physical Layer
5. OSI-Modell
  1. Application Layer
  2. Presentation Layer
  3. Session Layer
  4. Transport Layer
  5. Network Layer
  6. Data Link Layer
  7. Physical Layer
6. Calculate Traffic Intensity
  1. Transmission Delay
  2. Propagations Delay
  3. Processing Delay
  4. Queuing Delay

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Computer Networking

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	Created by Joakim Rødland about 7 years ago