TCP guarantees message delivery by implementing four requirements: Delivering segments in the order sent Detecting corrupt segments Retransmission of lost or corrupt segments Elimination of duplicate segments A TCP segment uses four of its fields to implement these requirements: Sequence … Continued

TCP improves performance with congestion avoidance and flow control. Congestion Avoidance Congestion avoidance is a way of increasing performance by reducing or minimizing the number of packets that are lost on the network (and so have to be resent) due … Continued

A socket is a communication endpoint on a network node. Sockets interact directly with processes. A process is a unit of state and behavior in an application. An application can run as a single process, but may use multiple processes … Continued

The Application Layer is a set of protocols that provide communication services to applications. Common protocols are HTTP (for web pages), HTTPS (secured version of HTTP), SMTP, POP3 and IMAP (for email), and DNS (used to look up IP addresses … Continued

HTTP HTTP stands for Hypertext Transfer Protocol. It is the protocol used to transfer requested web pages from servers to clients, as well as the protocol that allows clients to send data to servers. It defines the structure of messages … Continued

Simulating Statefulness in HTTP Traffic HTTP is inherently stateless, meaning that it doesn’t have any built-in mechnanism to keep track of anything in a message. As such, HTTP has no built-in way to relate different messages to one another. This … Continued

Session Hijacking There are many ways to compromise session security. Here, we’ll take a closer look at session hijacking and some ways to make it more difficult. Session hijacking refers to a malicious user gaining unauthorized access to a user’s … Continued

Encryption Encryption techniques are based on the idea of substituting plaintext characters with encrypted characters. An encryption process applies an algorithm to each plaintext character combined with a character from a key. (A key is a series of characters, usually … Continued

Transport Layer Security, or TLS, is one of the more popular protocols that implement encryption and authentication. TLS provides for encryption of Application Layer data, as well as authentication of the client and server transferring that data. URLs with the … Continued

The TLS handshake The process of securely exchanging symmetric keys is called a TLS handshake. The TLS handshake requires the Transport Layer to use TCP, and also requires the TCP handshake to have already taken place. TLS Handshake Key exchange … Continued