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Packet Types

There are a number of packets used in network transactions.

  • Data Packets: Data packets carry the actual payload.

    • such as the content of a web page, an email message, a file, or any other data sent between devices on the network.

  • Acknowledgment Packets: Also known as ACK packets, these are used in communication protocols (like TCP) to acknowledge the successful receipt of data packets.

    • When a device receives data, it sends an acknowledgment back to the sender, ensuring reliable data transfer.

  • SYN and SYN-ACK Packets: These are specific packets used during the handshake
    process in TCP connections.

    • The sending device sends a SYN (Synchronize) packet to initiate a connection.
    • The receiving device replies with a SYN-ACK (Synchronize-Acknowledgement) packet to acknowledge the request and agree to establish the connection.

  • RST Packets: RST (Reset) packets are used to terminate a connection abruptly or to
    signal an error condition during communication.

  • Request Packets: Request packets are sent by a client to request data or services from a server.

    • For example, an HTTP GET request packet is used to request a web page from a server.

  • Response Packets: Response packets are sent by a server in response to a client's request.

    • They contain the requested data or indicate the result of the client's request.

  • ICMP Packets: Internet Control Message Protocol (ICMP) packets are used for network
    troubleshooting and diagnostics.

    • They are commonly used to report errors, check network connectivity, or
      measure network performance.

  • ARP Packets: Address Resolution Protocol (ARP) packets are used to map IP addresses
    to MAC addresses in local networks.

    • They help devices find each other on the same network segment.

  • DNS Packets: Domain Name System (DNS) packets are used to resolve human-readable
    domain names (e.g., www.example.com) into IP addresses, enabling communication
    between devices on the internet.

  • Multicast Packets: Multicast packets are sent to a specific group of devices rather
    than to a single recipient.

    • They are used in multicast communication for efficient content distribution.

Martians

Martians are little green aliens that carry packets from un-routable/impossible/invalid source addresses. an example of a martian packet would be: Packets with a source IP that shouldn't be routable: - 127.0.0.1 from an external interface - Private ranges (192.168.x.x, 10.x.x.x), showing up where only public IPs should be.
- Reserved/bogus IPs or malformed headers.
- Basically packets from unexpected or spoofed resources.

Check if martians are allowed on the system via kernel settings: 

sysctl -a | grep -i ipv4 | grep -i martian