Email architecture in computer networks

Electronic mail Electronic mail, or email, is a very popular application in computer networks such as the Internet. Email Before looking at the details of Internet email, let us consider a simple scenario illustrated in the figure below, where Alice sends an email to Bob. Alice prepares her email by using an • a message format, that defines how valid email messages are encoded • protocols, that allow hosts and servers to exchange email messages • client software, that allows users to easily create and read email messages • software, that allows servers to efficiently exchange email messages We will first discuss the format of email messages followed by the protocols that are used on today’s Internet to exchange and retrieve emails. Other email systems have been developed in the past RFC 5598. Email messages, like postal mail, are composed of two parts : • a header that plays the same role as the letterhead in regular mail. It contains metadata about the message. • the body that contains the message itself. Email messages are entirely composed of lines of ASCII characters. Each line can contain up to 998 characters and is terminated by the CR and LF control characters RFC 5322. The lines that compose the header appear before the message body. An empty line, containing only the CR and LF characters, marks the end of the header. This is illustrated in the figure below. The structure of email messages The email header contains several lines that all begin with a keyword follow...

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Download a PDF of the paper titled Just a Second -- Scheduling Thousands of Time-Triggered Streams in Large-Scale Networks, by Heiko Geppert and 3 other authors Abstract: Deterministic real-time communication with bounded delay is an essential requirement for many safety-critical cyber-physical systems, and has received much attention from major standardization bodies such as IEEE and IETF. In particular, Ethernet technology has been extended by time-triggered scheduling mechanisms in standards like TTEthernet and Time-Sensitive Networking. Although the scheduling mechanisms have become part of standards, the traffic planning algorithms to create time-triggered schedules are still an open and challenging research question due to the problem's high complexity. In particular, so-called plug-and-produce scenarios require the ability to extend schedules on the fly within seconds. The need for scalable scheduling and routing algorithms is further supported by large-scale distributed real-time systems like smart energy grids with tight communication requirements. In this paper, we tackle this challenge by proposing two novel algorithms called Hierarchical Heuristic Scheduling (H2S) and Cost-Efficient Lazy Forwarding Scheduling (CELF) to calculate time-triggered schedules for TTEthernet. H2S and CELF are highly efficient and scalable, calculating schedules for more than 45,000 streams on random networks with 1,000 bridges as well as a realistic energy grid network within sub-seco...

Table of Contents 1 • • • • • • • • • • • • • • • • • • • • • • • • • • • Description: Email Architecture, Gmail two Step Verification, SMTP POP3 IMAP- This article is going to be a little bit longer, as I will try to explain things in detail. We will discuss the Email Architecture, study the different protocols like SMTP “Simple Mail Transfer Protocol”, PoP3 “Post Office Protocol”, and IMAP “Internet Mail Access Protocol”. I will practically create a Gmail account, and then using the Gmail two step verification, I will practically demonstrate how to secure your Gmail account using a cell phone. I will also explain why you need to activate the two step verification “ 2-step verification”. In this article I will also explain how to activate the most advanced security on your Gmail account so that the hackers can never hack your Gmail account. For the Gmail two factor authentication, we will be using the Yubikey Hardware Security Key invented by the Yubico. Email Architecture: Email architecture consists of three components: • User Agent (UA) • Message Transfer Agent (MTA) • Message Access Agent (MAA) User Agent: A user agent is a Package “or in simple words a program” of a software that composes, Reads, Responds to, and forward messages. It also handles user computers with local mailboxes. Sending Mail: In order to send a mail, the user creates mail through the UA which looks very similar to Postal Mail. Receiving Mail: The User agent, or a timer, is triggered by the User. ...