What is TCP/IP?

When two computers communicate over a network, they need a means of routing traffic from the source computer to the destination. Every computer on the Internet and on private internal networks is identified by an IP address.

This address gets its name from the fact that it is used by the Internet Protocol (IP). The IP header in a network packet contains the information needed to get a packet from point A to point B. In addition to the IP address, an IP header contains values designed to reorganize out-of-order packets and perform other critical tasks.

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What is TCP/IP?

What is TCP?

IP addresses come in two forms: IPv4 and IPv6. IPv4 addresses have the format X.X.X.X, where each X is a value in the range 0-255. Due to concerns about depleting the pool of available IPv4 addresses, the IPv6 protocol was created. Instead of the 32 bits used by IPv4, IPv6 uses 128 bits, giving it a much larger pool of potential addresses. While IPv4 is still the standard for Internet routing, a computer can have both an IPv4 and IPv6 address and be reached via either.

IP is designed to get a network packet to the intended destination computer. However, a computer might have many different applications running on it. After a packet reaches its destination, it must be directed to the right application.

The Transport Control Protocol (TCP) and the User Datagram Protocol (UDP) accomplish this via the use of ports. Each port is associated with a particular application, so the combination of IP address and port uniquely identifies a particular application on a certain computer.

TCP and UDP packets are encapsulated within an IP packet. This means that a packet will include an IP header followed by the TCP or UDP header and any data that the TCP or UDP packet is carrying.

The 4 Layers of the TCP/IP Model

TCP/IP is one of the foundational protocols of the Internet and underpins many common network protocols, such as HTTP which is used for web applications.

The TCP/IP model  encompasses these four layers of the network stack:

  • Data Link: The data link layer breaks data to be transmitted into frames for transmission at the physical layer. It also manages connections between two different nodes, including setting up the connection, identifying and correcting any bit errors that occur at the physical layer, and terminating the connection once the session is complete.
  • Internet: The IP protocol operates at the Internet layer of the TCP/IP model. It is responsible for moving a packet from the source to the destination computer.
  • Transport Layer: The Transport layer is where TCP sits in the TCP/IP model. It routes data to a particular application and performs error-handling.
  • Application: The Application layer contains higher-level data and functionality specific to an application. For example, the Application layer is where an HTTP and an SMTP packet would differ.

TCP vs. UDP

TCP and UDP perform similar roles, ensuring that packets are transported to the destination application. However, they have different areas of focus and methods of operation.

TCP is a connection-oriented protocol designed to ensure that packets reach their destination in the correct order and that no data is lost in transit. A TCP connection starts with the TCP handshake, which includes the following three steps:

  • SYN: A client sends a SYN packet to the server indicating that it wants to initiate a connection.
  • SYN/ACK: The server acknowledges receipt of the SYN packet and indicates that it is willing to communicate.
  • ACK: The client acknowledges its receipt of the SYN/ACK packet.

After the handshake is complete, the client and server can send data to each other over the established connection. Each data packet in the communication is acknowledged by the recipient with an ACK packet, verifying that nothing was lost in transit. TCP also includes the ability to reorder out-of-order packets and re-send any dropped packets. This makes TCP well-suited to use cases where preventing data loss is more important than efficiency.

In contrast, UDP is a connectionless protocol. In UDP, the client sends a request, and the server replies. UDP can’t detect if packets are dropped or perform any other error handling. UDP is designed to prioritize efficiency at the cost of potential data loss or errors.

The TCP/IP Model vs. the OSI Model

The other major network model in common use is the Open Systems Interconnection (OSI) model. The OSI model describes seven layers instead of the four used in TCP/IP. The OSI model is more of a theoretical model of the network, which breaks out various functions. The TCP/IP model reflects the actual structure of a network packet.

Check Point Solutions and the TCP/IP model

TCP/IP is a foundational network protocol and underlies many of the core protocols and applications in common use today. Check Point has offered network security solutions for over thirty years, beginning with on-prem firewalls and expanding as technologies evolve to include cloud, endpoint, mobile, and IoT security.

Check Point firewalls provide security at multiple layers of the TCP/IP model, including enforcing zero-trust policies and ensuring packets comply with the TCP/IP protocol standards. Additionally,

Check Point’s IPsec and SSL Virtual Private Networks (VPNs) ensure that content in TCP/IP packets is private and protect against man-in-the-middle (MitM) attacks.

In addition Check Point Quantum SD-WAN ensures corporate Wide Area Networks (WANs) are used optimally. This includes steering packets by application over multiple links, ensuring link stability and performance, and rerouting when the link performance falls below a configurable SLA. Learn more about SD-WAN must-haves in this ebook. Then, see the capabilities of Quantum SD-WAN for yourself with a free demo.

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