TCP/IP
What is TCP/IP?
TCP/IPThe four-layer Internet Protocol Suite that defines how packets are addressed, routed, fragmented, and reliably delivered between hosts across interconnected networks.
TCP/IP is the family of protocols that underpins the modern Internet, originally specified by DARPA and codified in numerous IETF RFCs. It is organized into four layers: link, internet (IP, RFC 791 for IPv4 and RFC 8200 for IPv6), transport (TCP, UDP), and application (HTTP, DNS, SMTP). IP provides best-effort addressing and routing, while TCP layers reliability, ordering, and congestion control on top. The model is connectionless at the network layer, which lets routers forward independently and survive link failures. From a security perspective, TCP/IP itself offers no confidentiality or authentication, so protections such as TLS, IPsec, and firewalls are added at upper or adjacent layers.
● Examples
- 01
A browser opens an HTTPS connection: DNS resolves a hostname, IP routes packets, TCP carries the bytes, TLS encrypts them.
- 02
A traceroute uses IP TTL expiry and ICMP responses to map the path between two hosts.
● Frequently asked questions
What is TCP/IP?
The four-layer Internet Protocol Suite that defines how packets are addressed, routed, fragmented, and reliably delivered between hosts across interconnected networks. It belongs to the Network Security category of cybersecurity.
What does TCP/IP mean?
The four-layer Internet Protocol Suite that defines how packets are addressed, routed, fragmented, and reliably delivered between hosts across interconnected networks.
How does TCP/IP work?
TCP/IP is the family of protocols that underpins the modern Internet, originally specified by DARPA and codified in numerous IETF RFCs. It is organized into four layers: link, internet (IP, RFC 791 for IPv4 and RFC 8200 for IPv6), transport (TCP, UDP), and application (HTTP, DNS, SMTP). IP provides best-effort addressing and routing, while TCP layers reliability, ordering, and congestion control on top. The model is connectionless at the network layer, which lets routers forward independently and survive link failures. From a security perspective, TCP/IP itself offers no confidentiality or authentication, so protections such as TLS, IPsec, and firewalls are added at upper or adjacent layers.
How do you defend against TCP/IP?
Defences for TCP/IP typically combine technical controls and operational practices, as detailed in the full definition above.
What are other names for TCP/IP?
Common alternative names include: Internet Protocol Suite, DoD model.
● Related terms
- network-security№ 1134
TCP
A connection-oriented transport protocol (RFC 9293) that delivers an ordered, reliable, congestion-controlled byte stream between two endpoints over IP.
- network-security№ 1188
UDP
A connectionless transport protocol (RFC 768) that delivers individual datagrams between ports with minimal overhead but no reliability or ordering guarantees.
- network-security№ 553
IP Address
A numeric identifier assigned to a network interface for routing across IP networks: 32 bits in IPv4 (RFC 791) or 128 bits in IPv6 (RFC 8200).
- network-security№ 508
ICMP
A network-layer control and diagnostics protocol (RFC 792 for IPv4, RFC 4443 for IPv6) used by hosts and routers to report errors and signal path conditions.
- network-security№ 1159
TLS (Transport Layer Security)
The IETF-standardized cryptographic protocol that provides confidentiality, integrity, and authentication for traffic between two networked applications.
- network-security№ 1160
TLS Handshake
The initial protocol exchange in Transport Layer Security that authenticates the server (and optionally the client) and derives the symmetric keys used to encrypt the rest of the session.
● See also
- № 437FTP
- № 1113Subnet
- № 168CIDR Notation
- № 092BGP Hijacking
- № 093BGP Route Leak