Network Packets and Protocols

Network packets are structured units of data transmitted across networks, comprising headers (which contain routing and addressing information), payloads (the actual data), and sometimes trailers for error-checking purposes.

Several key protocols operate within networks, each serving distinct purposes. HTTP (Hypertext Transfer Protocol) is primarily used for web browsing, typically over TCP ports 80 (HTTP) and 443 (HTTPS). DNS (Domain Name System) translates human-readable domain names into IP addresses, operating primarily on UDP/TCP port 53. ARP (Address Resolution Protocol) resolves IP addresses into MAC addresses, allowing devices on local networks to communicate effectively. TCP (Transmission Control Protocol) provides reliable, ordered, connection-oriented data transfer, while UDP (User Datagram Protocol) offers faster but connectionless and unreliable data transfers. ICMP (Internet Control Message Protocol) handles network diagnostics, commonly seen in tools like `ping`. SSH (Secure Shell) provides secure, encrypted remote access and management capabilities over networks, commonly using TCP port 22.

Network packets are structured units of data transmitted across networks, comprising headers (which contain routing and addressing information), payloads (the actual data), and sometimes trailers for error-checking purposes.

Definition: Structured units of data sent across a network, composed of headers, payload (data), and sometimes trailers (error-checking).

General Structure:

Network Protocols

HTTP (Hypertext Transfer Protocol)

Layer: Application (7)
Purpose: Web browsing
Port: TCP 80, HTTPS TCP 443

DNS (Domain Name System)

Layer: Application (7)
Purpose: Resolves domain names into IP addresses
Port: UDP/TCP 53

ARP (Address Resolution Protocol)

Layer: Data Link (2)
Purpose: Maps IP addresses to MAC addresses
Process:
1. Host broadcasts an ARP request asking, "Who has IP X.X.X.X?"
2. The host with IP X.X.X.X replies with its MAC address.

TCP (Transmission Control Protocol)

Layer: Transport (4)
Reliable, connection-oriented, ensures data delivery and order.

UDP (User Datagram Protocol)

Layer: Transport (4)
Connectionless, fast, no guaranteed delivery.

ICMP (Internet Control Message Protocol)

Layer: Network (3)
Diagnostic/control messaging (e.g., ping, traceroute).

SSH (Secure Shell)

Layer: Application (7)
Encrypted remote access and file transfers
Port: TCP 22

Packet Data

Packet data refers to the specific contents of network packets, including headers containing routing and addressing information and payloads such as HTTP requests, DNS queries, or other application-specific data. It can be summed up as:

Structured content within network packets including headers and payloads used by different protocols (HTTP request data, DNS queries, etc.).

Example:

Ethernet Frame:
  Dest MAC: AA:BB:CC:DD:EE:FF
  Source MAC: 11:22:33:44:55:66
IP Packet:
  Source IP: 192.168.1.10
  Dest IP: 142.250.68.142
TCP Segment:
  Source Port: 50234
  Dest Port: 80
Application Data:
  HTTP GET Request

Network Packets and data