Network Working Group T. Wugofski
Internet-Draft Openwave Systems, Inc.
Expires: March 15, 2004 September 15, 2003
MMS URI Schemes
draft-wugofski-mms-uri-scheme-00
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Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
This memo specifies URI (Universal Resource Identifier) schemes used
in Multimedia Messaging, as specified by the 3GPP.
The "mmsto" URI scheme is used to designate the MMS address of an
individual or service. In its simplest form, an "mmsto" URI contains
either an E.164 phone number or an Internet mail address.
For greater functionality, because interaction with some resources
may require message headers or message bodies to be specified as well
as the MMS address, the "mmsto" URI scheme may optionally include MMS
header fields and the message body.
The "mms" URI scheme is used to designate an MMS message and the
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sending of that message from the message originator.
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1. Requirements notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
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2. Introduction
2.1 3GPP Multimedia Messaging Service
The 3GPP MMS TS 23.140 technical specification was produced by the
3rd Generation Partnership Project (3GPP).
The 3GPP MMS TS 23.140 technical specification [3GPP23140] defines
what the 3GPP refers to as the stage 2 and stage 3 description of the
non-realtime Multimedia Messaging Service (MMS). Stage 2 identifies
the functional capabilities and information flows needed to support
the service described in stage 1 [3GPP22140].
As MMS user agents and MMS messaging transports are becoming a
standard component of mobile terminals, there is an increasing need
for other Internet enabled components on the mobile terminal to
leverage these capabilities
2.2 Universal Resource Identifiers
One of the core specifications for identifying resources on the
Internet is [RFC2396], specifying the syntax and semantics of a
Universal Resource Identifier (URI). The most important notion of
URIs are "schemes", which define a framework within which resources
can be identified (and possibly accessed). URIs enable users to
identify resources, and are used for very diverse schemes such as
access protocols (HTTP, FTP), broadcast media (TV channels
[RFC2838]), messaging (email [RFC2368]), or even telephone numbers
(voice [RFC2806]).
URIs are often confused with Universal Resource Names (URNs) and
Uniform Resource Locators (URLs). For the purpose of this memo, only
the term URI will be used, referring to the most fundamental concept.
The World Wide Web Consortium (W3C) has issued a note [W3C-URI]
discussing the topic of URIs, URNs, and URLs in detail.
2.3 The Need for MMS URIs
One important reason for universal access of the Web is the ability
to access all information through unique interfaces -- making it easy
and convenient to provide information as well as to consume it.
One aspect of this integration is the support of user agents (in the
case of the Web, commonly referred to as browsers) for multiple
content formats (such as HTML, GIF, JPEG) and access schemes (such as
HTTP, HTTP-S, FTP).
The "mailto" URI scheme has proven to be very useful and popular
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because most user agents support it by providing an email composition
facility when the user activates (e.g., clicks on) the URI.
In a similar manner, the "mmsto" URI scheme refers to the composition
of an MMS message, and as such, should be supported by user agents
with an MMS message composition facility.
This is particularly useful on mobile phones where MMS applications
are more predominant than email applications.
In addition, mobile phones also use messaging as a means of service
delivery. In this case, the "mms" URI scheme is used to represent an
MMS message on the MM1 interface, as defined by [3GPP22140].
Accordingly, the "mms" URI scheme should be supported by user agents
by sending an MMS message without user composition.
The goal of this memo is to specify the "mmsto" and "mms" URI schemes
so that user agents (such as Web browsers, MMS clients, and email
clients) could start to support it.
As with the "mailto" URI scheme, because interaction with some
resources may require message headers or message bodies to be
specified as well as the MMS address, both the "mmsto" and "mms" URI
schemes may optionally include MMS header fields and the message
body.
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3. The mmsto URI Scheme
Syntax definitions are given using the Augmented BNF for Syntax
Specifications [RFC2234].
3.1 Applicability
The "mmsto" URI scheme is intended for addressing an MMS message to
certain recipients. The functionality is quite similar to that of
the "mailto" URL scheme [RFC2368], that can be used with a
comma-separated list of email addresses. In both cases, additional
message parameters (such as the subject and message body) can be
provided.
How the MMS message is composed and subsequently sent to the MMS
Relay/Server is outside the scope of this memo. MMS messages can be
sent over the GSM air interface, by using a modem and a suitable
protocol, or by accessing services over other protocols, such as a
Web service for sending MMS messages.
3.2 Formal Definition
The "mmsto" URI is case-insensitive. The syntax of an "mmsto" URI is
formally described as follows, where the base syntax is taken from
[RFC2396]:
mmsto-uri = mmsto-scheme ":" scheme-specific-part
mmsto-scheme = "mmsto"
scheme-specific-part = [ to ] [ headers ]
to = 1*( mms-recipient )
headers = "?" header *( "&" header )
header = hname "=" hvalue
hname = *urlc
hvalue = *urlc
The "mms-recipient" is defined by the MM1 interface as specified in
[3GPP23140]. A valid MMS recipient address can be either an E.164
(MSISDN) or RFC822 address [RFC2822].
The "hname" and "hvalue" are encodings of an MMS informational
element name and value, unless a mapping already exists to RFC2822
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[RFC2822], as specified in [3GPP23140].
3.3 The MMS Recipient
The requirements for the MMS recipient address are defined by the MM1
interface as specified in [3GPP23140]. A valid MMS recipient address
can be a user address or a short code. A user address is either a
E.164 (MSISDN) or RFC822 address.
mms-recipient = plmn-addr / rfc822-addr / asc-addr [","
mms-recipient]
plmn-addr = gstn-phone ["/TYPE=PLMN"]
rfc822-addr = mailbox ["/TYPE=rfc822"]
asc-addr = *urlc
The "gstn-phone" is as specified in [RFC3601], allowing global as
well as local telephone numbers.
The "mailbox" is as specified in [RFC2822]. This means that it
consists of zero or more comma-separated mail addresses, possibly
including "phrase" and "comment" components.
The "asc-addr" is a alphanumeric short code that is interpreted by
the MMS infrastructure as specified in [3GPP23140].
All URI reserved characters in "to" must be encoded: in particular
parentheses, commas, and the percent sign ("%"), which commonly occur
in "mailbox" syntax.
3.4 The MMS Headers
MMS messages may contain a variety of headers as specified in
[3GPP23140]. The "hvalue" and "hvalue" are encodings of MMS
information element name and values, where the information element
name has been hyphenated.
In addition to the "body" hname, the following headers SHOULD be
supported:
Message-class = "Message-Class" "=" ( Class-identifier |
quoted-string )
Class-identifier = "Personal" | "Advertisement" | "Informational"
| "Auto"
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Expiry-value = "Expiry" "=" ( HTTP-date | delta-seconds )
Delivery-report = "Delivery-Report" "=" ( "Yes" | "No" )
Priority = "Priority" "=" ( "Low" | "Normal" | "High" )
Sender-visibility = "Sender-Visibility" "=" ( "Hide" | "Show" )
Read-reply = "Read-Reply" "=" ( "Yes" | "No" )
To-header = "to" "=" 1*( mms-recipient )
Cc-header = "cc" "=" 1*( mms-recipient )
Subject-header = "subject" "=" unstructured
All URI reserved characters MUST be encoded. 8-bit characters in
mailto URLs are forbidden. MIME encoded words (as defined in
[RFC2047]) are permitted in header values, but not for any part of a
"body" hname.
Within "mmsto" URIs, the characters "?", "=", "&" are reserved.
Because the "&" (ampersand) character is reserved in HTML, any
"mmsto" URI that contains an ampersand must be spelled differently in
HTML than in other contexts. An "mmsto" URI that appears in an HTML
document must use & instead of "&".
Also note that it is legal to specify both "to" and an "hname" whose
value is "to". That is,
mmsto:addr1%2C%20addr2
is equivalent to
mmsto:?to=addr1%2C%20addr2
is equivalent to
mmsto:addr1?to=addr2
8-bit characters in "mmsto" URLs are forbidden. MIME encoded words
(as defined in [RFC2047] ) are permitted in header values, but not
for any part of a "body" hname.
3.5 Parsing the mmsto URI
An "mmsto" URI identifies an "internet resource" corresponding to the
MMS mailbox specified in the address. When additional headers are
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supplied, the resource designated is the same address, but with an
additional profile for accessing the resource.
In current practice, resolving URIs and URLs such as those in the
"http" scheme causes an immediate interaction between user agents and
a host running an interactive server. In contrast, the "mmsto" URI
has similar semantics as the "mailto" URL -- resolving the "mmsto"
URI does not cause an immediate interaction. Rather, the user agent
creates a message to the designated address with the various header
fields set as default. The user can edit the message, send this
message unedited, or choose not to send the message.
The following list describes the steps for processing an "mmsto" URI:
1. The user agent MUST extract the plmn-addr, rfc822-addr, or short
code of each "mms-recipient". The user agent SHOULD ignore
recipients with invalid syntax.
2. The user agent MUST extract each header ("hname" and "hvalue"
pair) in order.
3. The user agent SHOULD NOT create the message if any of the
headers are considered dangerous. The user agent MAY also choose
to create a message with only a subset of the headers given in
the URI. Only the headers specified in this memo are considered
safe.
The creator of an "mmsto" URI cannot expect the resolver of a URI
to understand more than the "subject" and "body" headers. Clients
that resolve "mmsto" URIs into multimedia messages MUST be able
to correctly create MMS-compliant messages using the "subject"
and "body" headers.
4. The user agent MUST provide some means of message composition,
either by implementing this itself, or accessing a service or
application providing message composition.
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4. The mms URI Scheme
Syntax definitions are given using the Augmented BNF for Syntax
Specifications [RFC2234].
4.1 Applicability
The "mms" URI scheme is intended for addressing an MMS message to
certain recipients. The functionality is quite similar to that of
the "mmsto" URI with one significant exception.
Unlike the "mmsto" URI scheme, resolving an "mms" URI causes an
immediate attempt to interact with a host running an interactive
server -- much like the "http" scheme.
4.2 Formal Definition
The "mms" URI is case-insensitive. The syntax of an "mms" URI is
formally described as follows, where the base syntax is taken
[RFC2396]:
mms-uri = mms-scheme ":" scheme-specific-part
mms-scheme = "mms"
As with the "mmsto" URI scheme, the "mms" URI scheme supports the
inclusion of headers. The following headers SHOULD be supported:
Expiry-value = "Expiry" "=" ( HTTP-date | delta-seconds )
To-header = "to" "=" 1*( mms-recipient )
Subject-header = "subject" "=" unstructured
The "mms" URI scheme supports fewer headers than the "mmsto" URI
scheme because the user may not be able to view the result of
resolving the "mms" URI before the message is sent, and thus the
"mms" URI scheme is more amenable to abuse.
In all other respects, the "mms" URI formal definition is the same as
the "mmsto" formal definition defined above.
4.3 Parsing the mms URI
An "mms" URI identifies an "internet resource" corresponding to the
MMS mailbox specified in the address. When additional headers are
supplied, the resource designated is the same address, but with an
additional profile for accessing the resource.
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Resolving an "mms" URI causes an immediate interaction between the
user agent and a host running an interactive server -- much like the
"http" scheme. The user agent creates and attempts to send a message
to the designated address.
The following list describes the steps for processing an "mms" URI:
1. The user agent MUST extract the plmn-addr, rfc822-addr, or short
code of each "mms-recipient". The user agent SHOULD ignore
recipients with invalid syntax
2. The user agent MUST extract each header ("hname" and "hvalue"
pair) in order.
3. The user agent SHOULD NOT create the message if any of the
headers are considered dangerous. The user agent MAY also choose
to create a message with only a subset of the headers given in
the URI. Only the headers specified in this memo are considered
safe.
The creator of an "mmsto" URI cannot expect the resolver of a URI
to understand more than the "subject" and "body" headers. Clients
that resolve "mmsto" URIs into multimedia messages MUST be able
to correctly create MMS-compliant messages using the "subject"
and "body" headers.
4. The user agent MUST attempt to send the message.
5. If the message cannot be sent, the user agent SHOULD provide a
mechanism for the user to resend the message. Additionally, the
user agent MAY provide some means of message composition, either
by implementing this itself, or accessing a service or
application providing message composition.
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5. Security Considerations
The "mmsto" and "mms" URI schemes can be used to send a multimedia
message from one user to another, and thus can introduce many
security concerns. MMS messages can be logged at the originating
site, the recipient site, and intermediary sites along the delivery
path. If the messages are not encoded, they can also be read at any
of those sites.
An "mmsto" URI provides a template for a message that can be sent by
a user agent. The contents of that template may be opaque or
difficult to read by the user at the time of specifying the URI.
Thus, a user agent should never send a message based on an "mmsto"
URI without first showing the user the full message that will be sent
(including all headers that were specified by the "mmsto" URI), fully
decoded, and asking the user for approval to send the message. The
user agent should also make it clear that the user is about to send
an MMS message, since the user may not be aware that this is the
result of a "mmsto" URL.
The "mms" URI scheme provides a similiar capability for creating and
sending opaque MMS messages. Since the "mms" URI scheme requires an
immediate attempt to send the message to the recipient, the user is
not normally given the opportunity to review the message. However,
if any of the headers in an MMS message based on the "mms" URI scheme
are deemed unsafe, the user must be made aware of this and be able to
review prior to sending the message. The user agent should also make
it clear that the user is about to send an MMS message, since the
user may not be aware that this is the result of a "mms" URL. This
is especially true when sending an MMS message generates a charging
event (i.e., the user is going to have to pay for it).
An MMS user agent should provide mechanisms that allow complete
disclosure to the user of what is or will be sent; it should disclose
not only the message destination, but also any headers. Unrecognized
headers, or headers with values inconsistent with those the MMS
client would normally send should be especially suspect, especially
in the case of messages based on the "mms" URI scheme. MIME headers
(MIME- Version, Content-*) are most likely inappropriate, as are
those relating to routing (From, Bcc, etc.)
Note that some headers are inherently unsafe to include in a message
generated from a URI. For example, headers such as "From:", "Bcc:",
and so on, should never be interpreted from a URI. In general, the
fewer headers interpreted from the URI, the less likely it is that a
sending agent will create an unsafe message.
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6. IANA Considerations
There are no IANA considerations.
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References
[3GPP22140]
3GPP, "Multimedia Messaging Service; Stage 1", 3GPP
22.140-610, March 2003.
[3GPP23140]
3GPP, "Multimedia Messaging Service; Stage 2", 3GPP
23.140-610, March 2003.
[RFC2047] Moore, K., "MIME (Multipurpose Internet Mail Extensions)
Part Three: Message Header Extensions for Non-ASCII Text",
RFC 2047, November 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, March 1997.
[RFC2234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.
[RFC2368] Hoffman, P., Masinter, L. and J. Zawinski, "The mailto URL
scheme", RFC 2368, July 1998.
[RFC2396] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform
Resource Identifiers (URI): Generic Syntax", RFC 2396,
August 1998.
[RFC2806] Vaha-Sipila, A., "URLs for Telephone Calls", RFC 2806,
April 2000.
[RFC2822] Resnick, P., "Internet Message Format", RFC 2822, April
2001.
[RFC2838] Zigmond, D. and M. Vickers, "Uniform Resource Identifiers
for Television Broadcasts", RFC 2838, May 2000.
[RFC3601] Allocchio, C., "Text String Notation for Dial Sequences
and Global Switched Telephone Network (GSTN) / E.164
Addresses", RFC 3601, September 2003.
[W3C-URI] W3C/IETF URI Planning Interest Group, "URIs, URLs, and
URNs: Clarifications and Recommendations 1.0", W3C Note
21, September 2001.
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Author's Address
Ted Wugofski
Openwave Systems, Inc.
1400 Seaport Boulevard
Redwood City, CA 94063
US
Phone: +1 817 737 4533
EMail: ted.wugofski@openwave.com
URI: http://www.openwave.com/
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