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Networking, Purpose of OSI model - Coggle Diagram
Networking
Ip Address IPv4
An internet Protocol (IP) address is a unique sting of numbers that identifies each device on a network
IPv4, is a 32 bit number expressed as four octets, (about 4.3 billion addresses).
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supports unicast, broadcast, and multicast addressing
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IPv6
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IPv6 avoids NAT, improves performance and end to end connectivity, scalable
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Eliminates broadcast addressing, replacing multicast and anycast
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TCP/IP Model
Application Layer
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Protocols: HTTP, FTP, SMTP, DNS, Telnet
Notes: Topmost layer, user-facing
Transport Layer
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Functions: Reliability, flow control, error correction
Protocols: TCP (reliable), UDP (unreliable)
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Transport Protocols
TCP
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Reliability: Acknowledgements, retransmission, error detection
Ordering: Guaranteed, uses sequence numbers
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Use Cases: Web browsing, email, file transfer
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UDP
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Reliability: No guarantees, no retransmission
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Use Cases: Streaming, gaming, VoIP
Notes: Fast, low overhead, best-effort
Packet Architecture
UDP Datagram
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Fields: Source Port, Destination Port, Length, Checksum
Characteristics: Simple, minimal overhead
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TCP Segment
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Fields: Src/Dst Ports, Seq Number, Ack Number, Flags, Window Size, Checksum, Urgent Pointer, Options
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Scalability and Interoperability: TCP/IP was designed to work across different types of networks
and hardware.
End-to-End Communication: It provides host-to-host communication via two main transport
protocols—TCP for reliable, connection-oriented data transmission, and UDP for fast,
connectionless communication.
Layered Architecture: The TCP/IP model is divided into layers (Link, Internet, Transport, and
Application), with each layer having distinct functions and responsibilities.
Addressing and Routing: TCP/IP uses IP addresses and subnetting to route packets efficiently
across networks.
Internet Layer
Purpose: Routing + addressing scheme to identify devices on the network and routes data packets accordingly
Functions: Packet forwarding, fragmentation
Protocols: IP, ICMP, IGMP, RARP
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Network Interface Layer
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Functions: Frame formatting, MAC addressing
Protocols: Ethernet, PPP, Token Ring, WIFI USED FOR WIRELESS NETWORKS
Notes: Lowest layer, hardware-level
DoD department of defense, TCP/IP ensures that data transmitted reliably and efficiently. Flexible and scalable framework that can be used in variety of different environment
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OSI Model
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The seven layers
Network Layer
Manages the addressing and routing of data packets across networks. IP addresses are
utilised at this layer.
Routers work at the network layer to forward packets between different
networks, ensuring that data reaches its correct destination.
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Switch
In a network, switches use Mac address to decide where to forward data frames, when it received, the switch read the mac address and checks the tables (mac address associated with destination device), and then forwards the frames only to the port that connects to the destination device
Physical Layer
Deals with transmission and reception of the raw, unstructured data over a physical medium like cables and radio signals: raw bits
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Data Link Layer
Provides a node-node data transfer and handles error detection and correction from the physical layer. This layer is where Mac address operates
Switching devices like network bridges and switches use MAC addresses to direct
data between devices on the same network segment.
Frame traffic control, frame sequencing, frame acknowledgment
Router
Router use IP addresses to determine the best path for forwarding data packets across interconnected networks. relies on routing tables and protocols (OSPF, BGP) to make these decision
When packet is sent, router checks its destination IP address, consult their routing table, and then forward the packet towards its destination until it reaches the final network
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Inter-Network communication: This process is essential for communication over internet, as data often needs to travel across multiple networks and routers to travel across multiple networks and routers to reach its
Thousands of routers are spread through, router chooses the efficient pathway when sending data packets
Media access control(MAC) address assigned to a network interface for communication at the data link layer.
Typically, a 48-bit address expressed in hexadecimal format
Transport layer
Ensures complete data transfer, controlling the flow of data and providing error recovery and correction
Protocols such as TCP/IP transmission control protocol provide guarantee reliable communication by checking data integrity,
Protocols: UDP
UDP, on the other
hand, provides a connectionless, unreliable service that does not
guarantee delivery or order of packets.
UDP :user datagram protocol is a core internet protocol that provides fast communication
Session layer
Manages sessions or connections between applications, establishing, managing, and terminating these sessions.
IN a video call, this layer helps maintain the connection between two communicating devices
Protocols: NetBIOS, RPC, PPTP, TLC
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Presentation layer
Protocols: TLS/SSL, JPEG, PNG, MP3, AAC, ASCII, UNICODE
Translation, encryption, compression
Translates data between the application layer and the network, windows and MAC can understand each other data by converting data format
Application
Provides network services directly to the users application, closest layer to the end user
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Naming, Addressing & Directory Services
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Subnet mask
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Calculate the subnet, idenitfy CIDR notation which provides the host parts used
Subnet boundaries are multiples of the block of 0,64,128 and then network address = first address in block, broadcast is the last block
Default gateway- the router IP a host sends packets to when the destination is off-subnet (typical home example 192.168.1.1
NAT role0 maps many private addresses to a single public IP so internal hosts can access the internet while keeping private addressing internal
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Application - data (e.g, HTTP body, email content)
Transport- segment(TCP) or Datagram (UDP); TCP adds sequence numbers, UDP addes source/dest ports, length, checksum
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Data Link- Frame with source/destination MAC, frame header/trailer, error check (Ethernet FCS)
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Purpose of OSI model
Standardise Network communication: provides a universal communication from different manufacturers and systems can use to ensure their devices and protocols work together
apple device can talk to a windows device, both can use internet
Enhance interoperability facilitates among various hardware and software systems by defining standard operation between each layer
Basically, all layers can work together
Guide Protocol Development: The model serves as model for designing and understanding networking components
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Simplify Troubleshooting: By breaking down communication into seven layers, it's easier isolate and identify problems
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