Jarett Boxberger

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MIME(Multipurpose Internet Mail Extensions)

• By
• Jarett Boxberger

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Introduction to MIME

• Multimedia mail is becoming a fact of network
  life.
• Users not happy with plain text messages.
• Need to send spreadsheets, word processing files,
  audio, video, ect.
• Ability to create e-mail messages with audio and
  other non-textual contents is a new Internet mail
  standard that was approved in June of 1992,
  called MIME.

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Prior to MIME

• E-mail messages could transmit only 7-bit ASCII
  text.
• Before MIME it was possible to send audio/video,
  however it was vendor specific.
• MIME solved all of this.

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What is MIME?

• Offers a way to interchange text in languages
  with different character sets, and multimedia
  e-mail among different computer systems that use
  Internet mail standards.
• Developed by Nathaniel Borenstein of Bellcore and
  Ned Feed of Innosoft

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Allows you to create Email with

• Multiple objects in a single message
• Text having unlimited line length or overall
  length
• Character sets other than ASCII, allowing
  non-English language messages
• Multi-font messages
• Enriched text
• Images
• Audio
• Video
• Other messages (reliably encapsulated)
• Binary or application specific files
• Tar files
• PostScript
• FTPable file pointers

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Newtons Telecom Dictionary says MIME is a

• Standard format for including non-text
  information in Internet mail, thereby supporting
  the transmission of mixed-media messages across
  TCP/IP networks.
• Extension of SMPT, covers binary, audio, and
  video data.
• Standard for transmitting foreign language text
  which cannot be represented in plain ACII code.

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How MIME works

• MIME works by using headers.
• These headers are what allow MIME to work on all
  types of computer systems.
• There are 5 parts to the Header
• MIME-Version
• Content-Type
• Content-Transfer-Encoding
• Content-ID
• Content-Description

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MIME-Version

• Header field used to specify a version of the
  MIME standard that the message conforms to.
• MIME was written so it could be compatible with
  older Internet E-mail standards, in order to have
  a mail message recognize a MIME message, a
  MIME-version is required at the top level of the
  message.

ExampleMIME-Version 1.0
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Content-Type

• Used to specify the type of object that is
  enclosed in the message as well as subtype
  specifications.
• Subtype can have different additional parameters
  that provide more detail about the object.
• This allows the receiving Mail User Agent to
  easily recognize the enclosures sent in the
  message.

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Content-Type cont.

• Fields consist of
• Text
• Application
• Multipart
• Message
• Image
• Audio
• Video
• X-TypeName

ExampleContent-Type text/plain
charsetus-ascii
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Content-Type Text

• Represents Textual Information.
• Most important subtype is plain.
• Indicates unformatted text.
• No special software needed to read message
• Another subtype is enriched text
• Document contains different size font, or
  something in italic or bold.
• Also called formatted text

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Content-Type Application

• Represents information to be processed by a
  mail-based application or binary data that cannot
  be interpreted by the mail program.
• Subtypes include
• Octet-Stream ? encapsulates binary data that is
  not identified as another Content-Type.
• PostScript ? Indicates a body containing a
  postscript document.

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Content-Type Multipart

• Used when sending e-mail messages that contain
  multiple parts, each having its own data type.
• Subtypes
• Mixed ? processed in sequential order
• Parallel ? processed in parallel (example,
  playing audio and video simultaneously)
• Alternative ? different body parts present the
  same data in multiple formats
• Digest ? for multipart entities in which each
  part is of type message

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Content-Type Message

• Specifies an encapsulated message.
• Subtypes
• RFC822 ? when encapsulating an entire RFC822
  message
• Partial ? Used when the mail system will not
  allow transmission of a large message all at
  once. The message must be broken down into
  smaller pieces, this subtype has parameters that
  number and allow the receiving computer to put
  the message back together.
• External-Body ? object is too large for
  encapsulation, the body data are not included,
  but are referenced to a file on another server.

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Content-Type Image

• Data represents an image format.
• This case a display device such as a graphical
  display, fax machine, or printer is required.
• Subtypes
• JPEG
• GIF
• TIFF

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Content-Type Audio

• Represents data that isyou guessed it, in an
  audio format.
• An audio output device is required.
• Subtypes
• Basic ? audio encoded using 8 bit ISDN u-law
• WAV ? Windows sound file

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Content-Type Video

• Indicates the body data contains a moving picture
  image, and could also include sound.
• Subtype
• MPEG

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Content-Type X-TypeName

• Private Value
• Only used by mutual agreement
• Allows users to define their own values

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Content-Transfer-Encoding

• Content-Type header fields are represented in
  8-bit characters or in binary.
• Than can cause problems in some mail systems that
  dont support multimedia data.
• To ensure complete compatibility, all messages
  must contain only 7-bit ASCII data in lines no
  longer than 1,000 characters.
• MIME solves this problem by having the 8-bit
  character data or binary data first converted
  into 7-bit ASCII data. When the data reaches its
  destination the data is then stored back into its
  original format.

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Content-Transfer-Encoding cont.

• This portion of the header has 6 fields
• Quoted-Printable
• Base64
• 8-bit
• 7-bit
• Binary
• X-Encoding

ExampleContent-Transfer-Encoding 7bit
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Quoted-Printable

• Intended to represent data that consists of
  octets that correspond to printable characters in
  the US ASCII character set.
• Lines are no longer than 76 characters
• After the 75th character, the line is cut off and
  replaced with an sign, which serves as an
  escape character.

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Base64

• Encoding scheme used to represent binary data.
• Uses an alphabet which is a 65-character subset
  of the US ASCII character set.
• Lines are no longer than 76 characters

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8-Bit 7-Bit

• 8-Bit means the data may consist of non-ASCII
  characters.
• 7-Bit means the data consists of US ASCII
  characters only, and the lines are less than
  1,000 characters in length.
• 7-Bit encoding is the default value.

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Binary X-Encoding

• Binary means the message contains non-ASCII
  characters and the length of the lines may be
  greater than 1,000 characters.
• X-Encoding means that the data is not a standard
  Content-Transfer-Encoding. Any additional values
  must have a name that begin with X-.

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Content-ID Content-Description

• Two header fields that can be used to further
  identify and describe the data in a message body.

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What the process looks like

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What MIME Looks like
From - Tue Apr 1 093921 1997Received from
cantor (ppp-phx-15.futureone.com 207.2.43.15)
by future.futureone.com (8.8.2/8.8.0) with ESMTP
id JAA23032 for Tue, 1 Apr 1997 093614 -0700
(MST)Received from cantor (localhost
127.0.0.1) by cantor (8.7.4/8.7.3) with SMTP id
JAA00568 for Tue, 1 Apr 1997 093857
0700Sender chrlsim_at_futureone.comMessage-ID
33413A21.412D43B3_at_futureone.comDate Tue, 01 Apr
1997 093857 -0700 X-UIDL 859912584.000From
Chuck SimmonsOrganization Organized? You
jest!X-Mailer Mozilla 3.01 (X11 U Linux 2.0.0
i486)MIME-Version 1.0To Chuck
SimmonsSubject Test of fromContent-Transfer-Enc
oding 7bitContent-Type text/plain
charsetus-asciiStatus UX-Mozilla-Status
0001Content-Length 367
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Summary

• MIME allows us to send e-mail that contains more
  than just ordinary text.
• Uses Headers with 5 parts
• MIME-Version
• Content-Type
• Content-Transfer-Encoding
• Content-ID
• Content-Description