Message preparation Word processing Annotation Message sending User directory Timed delivery Multiple addressing Message priority Status information Interface to other facilities Message receiving Mailbox scanning Message selection Message notification Message reply Message rerouting

Defined in RFC 5598 At its most fundamental level consists of: User world In the form of message user agents (MUA) Transfer world In the form of the message handling service (MHS) Which is composed of message transfer agents (MTA)

Administrative management domain (ADMD) Internet provider Examples include: A department that operates a local mail relay (MTA) An IT department that operates an enterprise mail relay An ISP that operates a public shared service Domain name system (DNS) Directory lookup service that provides a mapping between the name of a host on the Internet and its numerical address

User agent enters a username and password to connect to the server to retrieve mail Post Office Protocol (POP) Provides stronger authentication and provides other functions not supported by POP Internet Mail Access Protocol (IMAP) Used for transfer of mail from a user agent to a MTA and from one MTA to another Simple Mail Transfer Protocol (SMTP) Supplements SMTP and allows the encapsulation of multimedia messages inside of a standard SMTP message Multipurpose Internet Mail Extensions (MIME)

Standard protocol for transferring mail between hosts in the TCP/IP suite Defined in RFC 821 Standardizes the message character set as 7-bit ASCII Adds log information to the start of the delivered message that indicates the path the message took

Defines a format for text messages that are sent using Used by SMTP as accepted mail format Messages are viewed as having an envelope and contents Envelope contains whatever information is needed to accomplish transmission and delivery Contents compose the object to be delivered to the recipient Content standard includes a set of header fields that may be used by the mail system to create the envelope, and the standard is intended to facilitate the acquisition of such information by programs

Consist of a sequence of lines of text and use a general “memo” framework A message consists of some number of header lines, which follow a rigid format, followed by a body portion consisting of arbitrary text A header line usually consists of a keyword, followed by a colon, followed by the keyword’s arguments The most frequently used keywords are From, To, Subject, and Date Also commonly found in the header is a Message-ID field which contains a unique identifier associated with the message

SMTP: Cannot transmit executable files or other binary objects Cannot transmit text data that include national language characteristics Servers may reject a mail message over a certain size Gateways that translate between ASCII and the character code EBCDIC do not use a consistent set of mappings, resulting in translation problems Gateways to X.400 networks cannot handle nontextual data included in X.400 messages Some implementations do not adhere completely to the SMTP standards defined in RFC 821

Intended to resolve problems with SMTP and RFC 822 Specifies five new message header fields which may be included in an RFC 822 header These fields provide information about the body of the message A number of content formats are defined, thus standardizing representations that support multimedia Transfer encodings are defined that enable the conversion of any content format into a form that is protected from alteration by the mail system

MIME-Version Must have the parameter value 1.0 Field indicates that the message conforms to the RFCs Content-Type Describes data in sufficient detail for receiver to pick method for representation Content-Transfer-Encoding Indicates type of transformation used to represent content Content-ID Used to uniquely identify MIME entities Content-Description Plain text description of the object with the body for use when object is not readable

Supports retrieval of mail between a client system (MUA) and a server that holds the mail for the client (MS) MUA establishes a TCP connection to the MS using port 110 POP3 (version 3 of POP) is an Internet standard defined in RFC 1939 Supports the basic functions of download and delete for retrieval States Authentication state Transaction state Update state

Defined by RFC 3501 Provides more functionality to users than the POP model Clients can have multiple remote mailboxes from which messages can be retrieved Clients can specify criteria for downloading messages Always keeps messages on the server and replicates copies to the clients Allows clients to make changes when connected and when disconnected

Table can be found on page 292 in text

Transaction oriented client/server protocol Most typical use is between a Web browser and a Web server Makes use of TCP to provide reliability Is a stateless protocol Each transaction is treated independently Flexible in the formats that it can handle

The Web is vulnerable to attacks on the Web servers over the Internet Reputations can be damaged and money can be lost if the Web servers are subverted A Web server can be exploited as a launching pad into the corporation’s or agency’s entire computer complex Web servers are relatively easy to configure and manage but the underlying software is extraordinarily complex and may hide potential security flaws Users are not necessarily aware of the security risks that exist and do not have the tools or knowledge to take effective countermeasures

Confidentiality All data that pass between the two applications are encrypted so that they cannot be eavesdropped on the Internet Message integrity SSL assures that the message is not altered or substituted for en route Authentication SSL can validate the identity of one or both partners to the exchange

Combination of HTTP and SSL to implement secure communication between a Web browser and a Web server Principal difference seen by a user of a Web browser is that URL addresses begin with Provides encrypted communication of: URL of the requested document Contents of the document Contents of the browser forms Cookies Contents of the HTTP Header

Media Refers to the form of information and includes text, still images, audio, and video Multimedia Human- computer interaction involving text, graphics, voice and video Also refers to storage devices that are used to store multimedia content Streaming media The media content is consumed as it is delivered from the server rather than waiting until an entire file is downloaded

Text Information that can be entered via a keyboard and is directly readable and printable Audio Encompasses two different ranges of sound Graphics Supports the communication of individual pictures, charts, or drawings Video Carries sequences of pictures in time

Widespread use of and the Internet by employees raises a number of concerns for employers Policy Issues: Business use only Policy scope Content ownership Privacy Standard of conduct Reasonable personal use Unlawful activity prohibited Security policy Company policy Company rights Disciplinary action

Electronic mail Internet mail architecture SMTP MIME POP and IMAP Web access and HTTP Web security Web traffic security approaches SSL HTTPS Chapter 10: Internet-Based Applications Multimedia applications Media types Multimedia applications Multimedia technologies Acceptable use policies Motivation Policy issues Guidelines for developing a policy