 sender site is transformed to ASCII data through MIME and are delivered to the client SMTP to be sent through the Internet. The ASCII data are received by the server SMTP and are delivered to MIME to be transformed into original data. Non ASCII code Non ASCII code 7-bit ASCII 7-bit ASCII 7-bit ASCII Figure 29.4 Role of MIME. Mail Communication MIME-Version, Content-Type, Content-Transfer-Encoding, Content-Id, Content-Description are the five headers defined by MIME that can be added to the original SMTP header sections to define the transformation parameters. Let us look into each of these headers: 1. MIME-Version The version of the MIME used, is defined by this header. MIME-Version: 1.1 2. Content-Type => The data type that are used in the body of the message are defined by this header. The type and the subtype of the contents are separated by a slash. The header may contain other parameters depending on the sub- type (see Figure 29.5). Content - Type : < type / subtype; parameters > Subtype Description Plain Unformatted text Mixed Body contains ordered parts of different data types Parallel Body contains parts of different data types Multipart Digest Similar to mixed but default type is message/RFC822 Alternative Parts are different versions of the same message RFC822 Body is an encapsulated message Message Partial Body is a fragment of a bigger message External body Body is a reference to another message Video Video is in MPEG format Audio Basic Single channel encoding of voice at 8KHZ Image is in JPEG format Image Image is in GIF format PostScript Adobe PostScript Application Octect stream General binary data of 8-bit bytes Figure 29.5 Content-Type => Type and subtype used in MIME. Fundamentals of EMS, NMS and OSS/BSS Content-Transfer-Encoding => The methods to encode the messages into zeros and ones to facilitate transport are defined by this header. Context-Transfer-Encoding: < type > The encoding can be: 7-bit: This encoding handles ASCII characters and short lines. It is a 7-bit ASCII encoding where the 