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Computer Network Articles
Page 90 of 122
What is a User Agent (UA)
A User Agent (UA) is an identification string that client software sends to web servers with each HTTP request. This string contains information about the browser, operating system, device type, and capabilities, enabling servers to deliver optimized content tailored to the specific client. When you visit a website, your browser automatically sends its user agent string in the HTTP header. Web servers analyze this information to determine how to respond — whether to serve mobile-optimized layouts, specific stylesheets, or content in the appropriate language. User Agent Communication Flow Client ...
Read MoreRFC 5322 Internet Message Format
RFC 5322 is an Internet standard that defines the format and structure of Internet messages, particularly email messages. Published by the Internet Engineering Task Force (IETF) in 2008, it specifies how email messages should be formatted, including headers, message body, and encoding rules to ensure interoperability across different email systems. This standard serves as the foundation for modern email communication, enabling consistent message exchange between different email clients, servers, and platforms worldwide. Message Structure Components RFC 5322 defines four main components of an Internet message: Envelope − Contains routing information including sender and recipient ...
Read MoreExtended Simple Mail Transfer Protocol (ESMTP)
Extended Simple Mail Transfer Protocol (ESMTP) is an enhanced version of the standard Simple Mail Transfer Protocol (SMTP) that provides additional functionality and flexibility for email transmission between servers. While SMTP handles basic email delivery, ESMTP adds commands and features to support modern email requirements such as attachments, authentication, and encryption. ESMTP maintains backward compatibility with SMTP while introducing extensions that allow servers to negotiate capabilities and handle complex email formats. This makes it the primary protocol used by email servers worldwide for reliable message delivery. ESMTP Email Flow ...
Read MoreSMTP Service Extension Parameters
SMTP (Simple Mail Transfer Protocol) is a protocol for transmitting email messages. An SMTP service extension is a feature or capability that can be added to the base SMTP protocol to provide additional functionality. These extensions are defined in the form of parameters that can be included in the SMTP command stream to indicate support for a particular extension or to provide additional information needed to use the extension. SMTP Extension Negotiation Flow Client ...
Read MoreSupporting outbound SMTP extensions
Outbound SMTP (Simple Mail Transfer Protocol) extensions are optional features that enhance email functionality beyond basic message delivery. These extensions are negotiated between sending and receiving mail servers during the SMTP conversation using the EHLO command, which advertises supported capabilities. SMTP Extension Negotiation Process Client (Sender) Server (Receiver) EHLO domain.com 250-PIPELINING 250-8BITMIME 250 DSN Server advertises supported extensions ...
Read MoreAttacks against 3G mobile networks
3G mobile network attacks are security threats specifically targeting third-generation mobile communication networks. These networks provide wireless data and voice services to mobile devices through cellular infrastructure. Understanding these attacks is crucial as 3G networks, while largely superseded by 4G and 5G, still serve as fallback networks and remain vulnerable to various security exploits. Attackers exploit weaknesses in 3G protocol design, network infrastructure, and device implementations to compromise user privacy, steal sensitive data, or disrupt network services. 3G Network Attack Vectors Mobile Device User ...
Read MoreAvailability in Information Security
Availability in information security refers to the ability of authorized users to access and use data and systems as intended. It is one of the three pillars of the CIA triad (Confidentiality, Integrity, Availability) that forms the foundation of information security. Ensuring availability means that critical systems and data remain accessible to legitimate users whenever needed. Availability ensures business continuity and prevents disruptions that could lead to financial losses, productivity decline, and damage to organizational reputation. For mission-critical services like healthcare systems, emergency services, and financial institutions, availability becomes even more crucial. CIA Triad ...
Read MoreAvalanche Effect in Cryptography
The avalanche effect in cryptography refers to the phenomenon where a small change in the input of a cryptographic function, such as a hash function, results in a significant and seemingly unrelated change in the output. This property is desirable in cryptographic functions because it makes it difficult for an attacker to predict the output of the function based on partial knowledge of the input. For example, consider a hash function that takes an input string and produces a fixed-size output. If the avalanche effect is strong, then making a small change to the input string, such as changing ...
Read MoreBacking up Cisco IOS Router image
A Cisco IOS (Internetwork Operating System) image is the software that runs on a Cisco router, containing essential system files, routing protocols, management tools, and security features needed for network operations. Backing up the Cisco IOS image is a critical maintenance task that protects against image corruption, accidental deletion, or hardware failure. A proper backup strategy ensures minimal downtime and quick recovery when issues arise. Cisco IOS Backup Methods TFTP Server Network-based Remote storage USB Flash Local storage ...
Read MoreBandwidth Allocation Control Protocol (BACP)
Bandwidth Allocation Control Protocol (BACP) is a protocol used in Asynchronous Transfer Mode (ATM) networks to control the allocation of bandwidth among different virtual channels. It ensures that bandwidth is allocated fairly among competing traffic streams and prevents any single traffic stream from monopolizing the network. BACP operates at the edge of the ATM network, in the ATM Adaptation Layer (AAL). When a virtual channel is established between two endpoints, BACP negotiates the amount of bandwidth allocated to that channel. It also monitors channel usage and adjusts the allocated bandwidth as necessary to ensure fair allocation among all channels. ...
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