Understanding Internet Protocol
The Internet Protocol (IP) is the network-layer protocol that carries data between hosts on different networks. It defines two things: the format of a packet (a header plus a payload) and an addressing scheme so routers know where to forward each packet. Almost everything else on the internet — the web, email, video calls, DNS — is built on top of IP.
IP is connectionless and best-effort: each packet is routed independently, and the protocol makes no promise that a packet will arrive, arrive in order, or arrive only once. Reliability, ordering, and retransmission are the job of a higher-layer protocol — usually TCP. Applications that prefer speed over guaranteed delivery use UDP instead. This separation of concerns is why IP has lasted for four decades with only one major revision.
The role of the IP address
An IP address identifies a network interface, not a person or even a specific machine — a laptop with Wi-Fi and Ethernet has two. It has two logical parts, a network prefix and a host portion, split by the subnet mask or CIDR length. Routers forward based on the network prefix; the final hop delivers to the specific host. Because most home and office networks sit behind NAT (Network Address Translation), every device on the LAN shares one public address on the internet and uses a private address (for example 192.168.x.x) locally.
Finding your IP address
Your local address is shown by ipconfig on Windows and ip addr (or ifconfig) on Linux and macOS. Your public address is the one the internet sees; you can't read it from your own machine because NAT rewrites it, so you ask an external service such as findWhatIsMyIP.com, which simply reports the source address of your request (the external IP address).
Key Features of Internet Protocol
- Addressing: Assigns unique addresses to devices
- Routing: Determines the best path for data packets
- Fragmentation: Breaks data into smaller packets
- Reassembly: Rebuilds data from packets at destination
IPv4 and IPv6
Two versions of IP are in production use today:
- IPv4 (RFC 791, 1981) uses 32-bit addresses — about 4.3 billion, written as four dotted decimals such as
203.0.113.7. The free pool was exhausted at the regional registries between 2011 and 2019, which is why addresses are now shared through NAT and traded on a secondary market. - IPv6 (RFC 8200, which replaced RFC 2460) uses 128-bit addresses — roughly 3.4×1038 of them — written as eight groups of hex digits, for example
2001:db8:85a3::8a2e:370:7334. It removes the need for NAT, simplifies the header, and builds in address autoconfiguration. - Dual stack is the normal deployment model during the transition: a host runs IPv4 and IPv6 at the same time and prefers IPv6 when both ends support it.
Cybersecurity Concerns with Internet Protocol
While Internet Protocol is essential for data communication, it also poses several cybersecurity risks:
- IP Spoofing: Attackers can falsify the source IP address, making it look like a message has come from a trusted source, potentially gaining unauthorized access to systems.
- Man-in-the-Middle Attacks: Since the communication is routed through different nodes, attackers can intercept and alter communications.
- DDoS Attacks: Attackers can flood a target with traffic using multiple IP addresses, causing denial of service.
- Lack of Authentication: Traditional IP lacks built-in methods for ensuring data integrity and authenticity, making it susceptible to various attacks.
How to Fix IP Cybersecurity
To address cybersecurity issues associated with Internet Protocol (IP), implementing robust security measures is crucial. These measures include the use of IPsec (Internet Protocol Security) to encrypt IP packets and authenticate communications, thus ensuring the data's confidentiality and integrity. Network monitoring tools can detect and block suspicious activities, while firewalls and intrusion detection systems can prevent unauthorized access. Regularly updating systems and utilizing strong access controls can further protect against vulnerabilities. Educating users about the risks and promoting good cybersecurity practices also play a vital role in safeguarding network communications. A quick way to strengthen those access controls is to run every admin and router login through a strong password generator instead of reusing an old password.
Why the version number jumps from 4 to 6
The 4-bit version field in the IP header has carried several values over the protocol's history, and the numbering is often misreported:
- Versions 0–3 were internal version numbers used while TCP and IP were being separated into distinct protocols in the late 1970s. They were never deployed and were never published as standalone standards.
- Version 4 is the first production version, specified in RFC 791 (1981). Everything before it was pre-standard development work.
- Version 5 was assigned to the Internet Stream Protocol (ST, later ST-II), an experimental protocol for real-time voice and video. It was a parallel experiment, not a successor to IPv4, so the number 5 was retired to avoid confusion.
- Version 6 was chosen for the next-generation protocol (originally “IPng”) precisely because 5 was already taken. There is no IPv7, IPv8, or IPv9 in real use — claims otherwise are hoaxes or April Fools' RFCs (RFC 1606, RFC 1607).
To see how IP, TCP and UDP actually behave in code, my course TCP/IP Socket Programming in C# builds networked client/server apps from raw sockets up.