[IMXPwg] step 2 of section 4.4.2

Marshall Rose mrose@dbc.mtview.ca.us
Wed, 27 Sep 2000 11:18:37 -0700


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thanks. i've made the changes (although slightly differently, e.g., access
policies talks about the BEEP peer stuff for relays and the bind command).

/mtr


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class=3D"header">September 27, 2000</td></tr>
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<div align=3D"right"><font face=3D"monaco, MS Sans Serif" =
color=3D"#990000" size=3D"+3"><b><br><span class=3D"title">The =
IMXP</span></b></font></div>
<div align=3D"right"><font face=3D"monaco, MS Sans Serif" =
color=3D"#666666" size=3D"+2"><b><span =
class=3D"filename">draft-mrose-imxp-core-01</span></b></font></div>
<font face=3D"verdana, helvetica, arial, sans-serif" size=3D"2">

<h3>Status of this Memo</h3>
<p>
This document is an Internet-Draft and is in full conformance with all =
provisions of Section 10 of RFC2026.</p>
<p>
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups.
Note that other groups may also distribute working documents as
Internet-Drafts.</p>
<p>
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any =
time.
It is inappropriate to use Internet-Drafts as reference material or to =
cite
them other than as "work in progress."</p>
<p>
The list of current Internet-Drafts can be accessed at
<a =
href=3D'http://www.ietf.org/ietf/1id-abstracts.txt'>http://www.ietf.org/i=
etf/1id-abstracts.txt</a>.</p>
<p>
The list of Internet-Draft Shadow Directories can be accessed at
<a =
href=3D'http://www.ietf.org/shadow.html'>http://www.ietf.org/shadow.html<=
/a>.</p>
<p>
This Internet-Draft will expire on March 28, 2001.</p>

<h3>Copyright Notice</h3>
<p>
Copyright (C) The Internet Society (2000). All Rights Reserved.</p>

<h3>Abstract</h3>

<p>
This memo describes IMXP,
an extensible,
asynchronous message relaying service for application layer
programs.
</p>
<a name=3D"toc"><br><hr size=3D"1" shade=3D"0"></a>
<table border=3D"0" cellpadding=3D"0" cellspacing=3D"2" width=3D"30" =
height=3D"15" align=3D"right"><tr><td bgcolor=3D"#990000" =
align=3D"center" width=3D"30" height=3D"15"><a href=3D"#toc" =
CLASS=3D"link2"><font face=3D"monaco, MS Sans Serif" color=3D"#ffffff" =
size=3D"1"><b>&nbsp;TOC&nbsp;</b></font></a><br></td></tr></table>
<h3>Table of Contents</h3>
<ul compact class=3D"toc">
<b><a href=3D"#anchor1">1.</a>&nbsp;
Introduction<br></b>
<b><a href=3D"#anchor2">1.1</a>&nbsp;
Overview<br></b>
<b><a href=3D"#anchor3">1.2</a>&nbsp;
Architecture at a Glance<br></b>
<b><a href=3D"#anchor4">2.</a>&nbsp;
Service Principles<br></b>
<b><a href=3D"#anchor5">2.1</a>&nbsp;
Modes of Operation<br></b>
<b><a href=3D"#anchor6">2.2</a>&nbsp;
Naming of Entities<br></b>
<b><a href=3D"#imxp.provisioning">3.</a>&nbsp;
Service Provisioning<br></b>
<b><a href=3D"#anchor7">3.1</a>&nbsp;
Connection Establishment<br></b>
<b><a href=3D"#anchor8">3.2</a>&nbsp;
Authentication<br></b>
<b><a href=3D"#anchor9">3.3</a>&nbsp;
Authorization<br></b>
<b><a href=3D"#anchor10">3.4</a>&nbsp;
Confidentiality<br></b>
<b><a href=3D"#anchor11">3.5</a>&nbsp;
Routing Integrity<br></b>
<b><a href=3D"#anchor12">3.6</a>&nbsp;
Traffic Analysis<br></b>
<b><a href=3D"#imxp.profile">4.</a>&nbsp;
The IMXP<br></b>
<b><a href=3D"#imxp.xml-and-mime">4.1</a>&nbsp;
Use of XML and MIME<br></b>
<b><a href=3D"#anchor13">4.2</a>&nbsp;
Profile Identification and Initialization<br></b>
<b><a href=3D"#anchor14">4.3</a>&nbsp;
Message Syntax<br></b>
<b><a href=3D"#imxp.messages">4.4</a>&nbsp;
Message Semantics<br></b>
<b><a href=3D"#operation.attach">4.4.1</a>&nbsp;
The Attach Operation<br></b>
<b><a href=3D"#operation.bind">4.4.2</a>&nbsp;
The Bind Operation<br></b>
<b><a href=3D"#anchor15">4.4.3</a>&nbsp;
The Terminate Operation<br></b>
<b><a href=3D"#operation.data">4.4.4</a>&nbsp;
The Data Operation<br></b>
<b><a href=3D"#relay.data">4.4.4.1</a>&nbsp;
Relay Processing of Data<br></b>
<b><a href=3D"#appl.data">4.4.4.2</a>&nbsp;
Application Processing of Data<br></b>
<b><a href=3D"#imxp.access">4.5</a>&nbsp;
IMXP Access Policies<br></b>
<b><a href=3D"#anchor16">4.5.1</a>&nbsp;
Use of Access Policies in the Endpoint-Relay Mode<br></b>
<b><a href=3D"#anchor17">4.5.2</a>&nbsp;
Use of Access Policies in the Relay-Relay Mode<br></b>
<b><a href=3D"#imxp.options">5.</a>&nbsp;
IMXP Options<br></b>
<b><a href=3D"#option.statusRequest">5.1</a>&nbsp;
The statusRequest Option<br></b>
<b><a href=3D"#imxp.services">6.</a>&nbsp;
IMXP Services<br></b>
<b><a href=3D"#anchor18">6.1</a>&nbsp;
Use of the IMXP Core DTD<br></b>
<b><a href=3D"#anchor19">6.1.1</a>&nbsp;
Transaction-Identifiers<br></b>
<b><a href=3D"#operation.reply">6.1.2</a>&nbsp;
The Reply Operation<br></b>
<b><a href=3D"#service.report">6.2</a>&nbsp;
The Report Service<br></b>
<b><a href=3D"#anchor20">7.</a>&nbsp;
Registration Templates<br></b>
<b><a href=3D"#option.registration">7.1</a>&nbsp;
IMXP Option Registration Template<br></b>
<b><a href=3D"#service.registration">7.2</a>&nbsp;
IMXP Service Registration Template<br></b>
<b><a href=3D"#anchor21">8.</a>&nbsp;
Initial Registrations<br></b>
<b><a href=3D"#imxp.definition">8.1</a>&nbsp;
Registration: The IMXP Profile<br></b>
<b><a href=3D"#imxp-gstn.definition">8.2</a>&nbsp;
Registration: The IMXP Service-Selector for GSTN<br></b>
<b><a href=3D"#statusRequest.definition">8.3</a>&nbsp;
Registration: The statusRequest Option<br></b>
<b><a href=3D"#report.definition">8.4</a>&nbsp;
Registration: The Report Service<br></b>
<b><a href=3D"#anchor22">9.</a>&nbsp;
DTDs<br></b>
<b><a href=3D"#imxp-core.dtd">9.1</a>&nbsp;
The IMXP Core DTD<br></b>
<b><a href=3D"#imxp-report.dtd">9.2</a>&nbsp;
The Report Service DTD<br></b>
<b><a href=3D"#imxp.reply-codes">10.</a>&nbsp;
Reply Codes<br></b>
<b><a href=3D"#security">11.</a>&nbsp;
Security Considerations<br></b>
<b><a href=3D"#anchor23">12.</a>&nbsp;
IANA Considerations<br></b>
<b><a href=3D"#rfc.references">&#167;</a>&nbsp;
References<br></b>
<b><a href=3D"#rfc.authors">&#167;</a>&nbsp;
Authors' Addresses<br></b>
<b><a href=3D"#anchor24">A.</a>&nbsp;
Changes from draft-mrose-imxp-core-00<br></b>
<b><a href=3D"#anchor25">B.</a>&nbsp;
Acknowledgements<br></b>
<b><a href=3D"#rfc.copyright">&#167;</a>&nbsp;
Full Copyright Statement<br></b>
</ul>
<br clear=3D"all">

<a name=3D"anchor1"><br><hr size=3D"1" shade=3D"0"></a>
<table border=3D"0" cellpadding=3D"0" cellspacing=3D"2" width=3D"30" =
height=3D"15" align=3D"right"><tr><td bgcolor=3D"#990000" =
align=3D"center" width=3D"30" height=3D"15"><a href=3D"#toc" =
CLASS=3D"link2"><font face=3D"monaco, MS Sans Serif" color=3D"#ffffff" =
size=3D"1"><b>&nbsp;TOC&nbsp;</b></font></a><br></td></tr></table>
<h3>1.&nbsp;Introduction</h3>

<p>
Network applications can be broadly distinguished by five
operational characteristics:

<ul class=3D"text">

<li>
server push or client pull;
</li>

<li>
synchronous (interactive)
or asynchronous (batch);
</li>

<li>
time-assured or time-insensitive;
</li>

<li>
best-effort or reliable; and,
</li>

<li>
stateful or stateless.
</li>

</ul>

For example:

<ul class=3D"text">

<li>
the world-wide web is a pull, synchronous, time-insensitive, reliable,
stateless service; whilst
</li>

<li>
Internet mail is a push, asynchronous, time-insensitive,
best-effort (without DSN), stateless service.
</li>

</ul>

</p>

<p>
Messaging applications vary considerably in their operational
requirements.
For example,
some messaging applications require assurance of timeliness and =
reliability,
whilst others do not.
</p>

<p>
These features come at a cost,
in terms of both infrastructural and configuration complexity.
Accordingly,
the underlying service must be extensible to support different
requirements in a consistent manner.
</p>

<p>
This memo defines a core messaging service that supports a range
of operational characteristics.
The core service supports a variety of tailored services for both
user-based and programmatic exchanges.
</p>

<p>

</p>

<h4><a name=3D"anchor2">1.1</a>&nbsp;Overview</h4>

<p>
IMXP provides an extensible,
asynchronous message relaying service for application layer programs.
</p>

<p>
IMXP,
at its core,
provides a best-effort datagram service.
Each datagram,
simply termed "data",
is originated and received by IMXP "endpoints" --
applications that dynamically attach to the IMXP "relaying mesh".
</p>

<p>
The data transmitted specifies:

<ul class=3D"text">

<li>
an originating endpoint;
</li>

<li>
an opaque content (via a URI-reference);
</li>

<li>
one or more recipient endpoints; and,
</li>

<li>
zero or more options.
</li>

</ul>

Options are used to alter the semantics of the the service,
may occur on a per-recipient or per-data basis,
and may be processed by either a single or multiple relays.
</p>

<p>
Additional IMXP services are provided on top of the relaying mesh;
e.g., access control and presence information.
Typically these services are provided by servers that are
co-resident with one or more relays within an administrative domain.
</p>

<p>
IMXP is specified as a <a href=3D"#BEEP-FRAMEWORK">BEEP</a>[1] =
"profile".
Accordingly,
many aspects of IMXP (e.g., authentication) are provided within the
BEEP framework.
Throughout this memo,
the terms "peer", "initiator", "listener", "client", and "server" are
used in the context of BEEP.
In particular,
Section 2.1 of the BEEP framework memo discusses the roles that a BEEP
peer may perform.
</p>

<p>
When reading this memo,
note that the terms "endpoint" and "relay" are specific to IMXP,
they do not exist in the context of BEEP.
</p>

<h4><a name=3D"anchor3">1.2</a>&nbsp;Architecture at a Glance</h4>

<p>
The IMXP stack:
</p>
</font><pre>
   +-------------+
   | IMXP        |        an IMXP process is either:
   |     process |
   +-------------+            - an application attached as an IMXP
   |             |              endpoint; or,
   |    IMXP     |
   |             |            - an IMXP relay
   +-------------+
   |             |        IMXP services are realized as applications
   |    BEEP     |        having a special relationship with the IMXP
   |             |        relays in their administrative domain
   +-------------+
   |   TCP/IP    |
   +-------------+
   |     ...     |
   +-------------+
</pre><font face=3D"verdana, helvetica, arial, sans-serif" size=3D"2">

<p>

</p>

<p>
The IMXP entities:
</p>
</font><pre>
       administrative domain #1          administrative domain #2
    +----------------------------+    +----------------------------+
    |   +------+                 |    |                 +------+   |
    |   |      |                 |    |                 |      |   |
    |   | appl |                 |    |                 | appl |   |
    |   |      |                 |    |                 |      |   |
    |   +......+       +------+  |    |  +------+       +......+   |
    |   |      |       |      |  |    |  |      |       |      |   |
    |   |end-  |       |relay |  |    |  |relay |       |end-  |   |
    |   | point|       |      |  |    |  |      |       | point|   |
    |   +------+       +------+  |    |  +------+       +------+   |
    |   |      |       |      |  |    |  |      |       |      |   |
    |   | IMXP |       | IMXP |  |    |  | IMXP |       | IMXP |   |
    |   |      |       |      |  |    |  |      |       |      |   |
    |   +------+       +------+  |    |  +------+       +------+   |
    |   |      |       |      |  |    |  |      |       |      |   |
    |   | BEEP |       | BEEP |  |    |  | BEEP |       | BEEP |   |
    |   |      |       |      |  |    |  |      |       |      |   |
    |   +------+       +------+  |    |  +------+       +------+   |
    |        ||         ||  ||   |    |   ||  ||         ||        |
    |        =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D  =
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D  =
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D        |
    +----------------------------+    +----------------------------+

                   | &lt;---- IMXP relaying mesh ----> |



        Note: routing between administrative domains is configured
              using SRV RRs.  Accordingly, the actual number of
              relays between two endpoints is not fixed.
</pre><font face=3D"verdana, helvetica, arial, sans-serif" size=3D"2">

<a name=3D"anchor4"><br><hr size=3D"1" shade=3D"0"></a>
<table border=3D"0" cellpadding=3D"0" cellspacing=3D"2" width=3D"30" =
height=3D"15" align=3D"right"><tr><td bgcolor=3D"#990000" =
align=3D"center" width=3D"30" height=3D"15"><a href=3D"#toc" =
CLASS=3D"link2"><font face=3D"monaco, MS Sans Serif" color=3D"#ffffff" =
size=3D"1"><b>&nbsp;TOC&nbsp;</b></font></a><br></td></tr></table>
<h3>2.&nbsp;Service Principles</h3>

<h4><a name=3D"anchor5">2.1</a>&nbsp;Modes of Operation</h4>

<p>
IMXP is used in two modes:

<blockquote class=3D"text"><dl>

<dt>endpoint-relay:</dt>
<dd>

in which the endpoint is always the BEEP initiator of the service,
whilst relays are always the BEEP listeners.
In this context,
applications attach as endpoints,
and then the transmission of data occurs.
</dd>

<dt>relay-relay:</dt>
<dd>

in which relays typically,
though not necessarily,
reside in different administrative domains.
In this context,
applications bind as relays,
and then the transmission of data occurs.
</dd>

</dl></blockquote>

</p>

<p>
In the endpoint-relay mode,
an endpoint (BEEP initiator) may:

<ul class=3D"text">

<li>
attach as one or more endpoints;
</li>

<li>
send data to other endpoints;
</li>

<li>
receive data from other endpoints; and,
</li>

<li>
terminate any of its attachments.
</li>

</ul>

A relay (BEEP listener),
in addition to servicing requests from a BEEP initiator, may:

<ul class=3D"text">

<li>
terminate any of the endpoint's attachments;
</li>

<li>
deliver data from other endpoints; and,
</li>

<li>
indicate the delivery status of data sent earlier by the endpoint.
</li>

</ul>

</p>

<p>
In the relay-relay mode,
a relay (BEEP listener or initiator) may:

<ul class=3D"text">

<li>
bind as one or more administrative domains;
</li>

<li>
send data;
</li>

<li>
receive data; and,
</li>

<li>
terminate any bindings.
</li>

</ul>

</p>

<p>

</p>

<h4><a name=3D"anchor6">2.2</a>&nbsp;Naming of Entities</h4>

<p>
Endpoints are named using the "addr-spec" syntax of
<a href=3D"#RFC0822">RFC 822</a>[2],
i.e., "local@domain".
</p>

<p>
Using the service-selector convention of
<a href=3D"#RFC2846">RFC 2846</a>[3],
all endpoint identities having a local-part starting with "imxp=3D" are
reserved for use by IMXP services registered with the IANA.
</p>

<p>
Relays,
although not named,
serve of behalf of administrative domains,
as identified by a FQDN,
e.g., "example.com".
</p>

<p>
In IMXP,
"endpoints" and "relays" are the fundamental entities.
IMXP is carried over BEEP,
which has the "peer" as its fundamental entity.
The relationship between BEEP peer entities and IMXP endpoint and
relay entities are defined by IMXP's
<a href=3D"#imxp.access">Access Policies</a>.
</p>

<a name=3D"imxp.provisioning"><br><hr size=3D"1" shade=3D"0"></a>
<table border=3D"0" cellpadding=3D"0" cellspacing=3D"2" width=3D"30" =
height=3D"15" align=3D"right"><tr><td bgcolor=3D"#990000" =
align=3D"center" width=3D"30" height=3D"15"><a href=3D"#toc" =
CLASS=3D"link2"><font face=3D"monaco, MS Sans Serif" color=3D"#ffffff" =
size=3D"1"><b>&nbsp;TOC&nbsp;</b></font></a><br></td></tr></table>
<h3>3.&nbsp;Service Provisioning</h3>

<h4><a name=3D"anchor7">3.1</a>&nbsp;Connection Establishment</h4>

<p>
The <a href=3D"#RFC2782">SRV algorithm</a>[4] is used to
determine the IP/TCP addressing information assigned to the relays for =
an
administrative domain:

<blockquote class=3D"text"><dl>

<dt>service:</dt>
<dd>
"imxp-edge" (for the endpoint-relay mode),
or "imxp-mesh" (for the relay-relay mode);
</dd>

<dt>protocol:</dt>
<dd>
"tcp"; and,
</dd>

<dt>domain:</dt>
<dd>
the administrative domain.
</dd>

</dl></blockquote>

</p>

<h4><a name=3D"anchor8">3.2</a>&nbsp;Authentication</h4>

<p>
Authentication is a matter of provisioning for each BEEP peer
(c.f., <a href=3D"#imxp.access">IMXP Access Policies</a>).
</p>

<p>
An IMXP relay might be provisioned to allow a BEEP peer identity to
coincide with a given endpoint identity.
For example,
a relay in the "example.com" administrative domain may be configured
to allow a BEEP peer identified as "fred@example.com" to be authorized
to attach as the IMXP endpoint "fred@example.com".
</p>

<h4><a name=3D"anchor9">3.3</a>&nbsp;Authorization</h4>

<p>
Authorization is a matter of provisioning for each BEEP peer
(c.f., <a href=3D"#imxp.access">IMXP Access Policies</a>).
</p>

<p>
Typically,
a relay requires that its BEEP peer authenticate as a prelude to
authorization,
but an endpoint usually does not require the same of its BEEP peer.
</p>

<h4><a name=3D"anchor10">3.4</a>&nbsp;Confidentiality</h4>

<p>
Confidentiality is a matter of provisioning for each BEEP peer.
</p>

<p>
Typically,
any data considered sensitive by an originating endpoint will have its
content encrypted for the intended recipient endpoint(s),
rather than relying on hop-by-hop encryption.
Similarly,
an originating endpoint will sign the content if end-to-end
authentication is desired.
</p>

<p>

</p>

<h4><a name=3D"anchor11">3.5</a>&nbsp;Routing Integrity</h4>

<p>
Data are routed according to SRV entries in the DNS.
Accordingly,
routing integrity is a function of the DNS and the applications making
use of the DNS.
Additional assurance is provided if the BEEP initiator requires that
the BEEP listener authenticate itself.
</p>

<h4><a name=3D"anchor12">3.6</a>&nbsp;Traffic Analysis</h4>

<p>
Hop-by-hop protection of data transmitted through the relaying mesh
(endpoint identities and content) is afforded at the BEEP level
through the use of a transport security profile.
Other traffic characteristics,
e.g., volume and timing of transmissions,
is not protected from third-party analysis.
</p>

<a name=3D"imxp.profile"><br><hr size=3D"1" shade=3D"0"></a>
<table border=3D"0" cellpadding=3D"0" cellspacing=3D"2" width=3D"30" =
height=3D"15" align=3D"right"><tr><td bgcolor=3D"#990000" =
align=3D"center" width=3D"30" height=3D"15"><a href=3D"#toc" =
CLASS=3D"link2"><font face=3D"monaco, MS Sans Serif" color=3D"#ffffff" =
size=3D"1"><b>&nbsp;TOC&nbsp;</b></font></a><br></td></tr></table>
<h3>4.&nbsp;The IMXP</h3>

<p>
<a href=3D"#imxp.definition">Registration: The IMXP Profile</a> contains =
the BEEP profile
registration for IMXP.
</p>

<h4><a name=3D"imxp.xml-and-mime">4.1</a>&nbsp;Use of XML and MIME</h4>

<p>
Each BEEP payload exchanged via IMXP consists of an XML document and
possibly an arbitrary MIME content.
</p>

<p>
If only an XML document is sent in the BEEP payload,
then the mapping to a BEEP payload is straight-forward,
e.g.,
</p>
</font><pre>
    C: MSG 1 2 . 111 27
    C: Content-Type: text/xml
    C:=20
    C: &lt;terminate transID=3D'1' />
    C: END
</pre><font face=3D"verdana, helvetica, arial, sans-serif" size=3D"2">

<p>
Otherwise,
if an arbitrary MIME content is present,
it is indicated by a <a href=3D"#RFC2396">URI-reference</a>[5]
in the XML control document.
The URI-reference may contain an absolute-URI
(and possibly a fragment-identifier),
or it may be a relative-URI consisting only of a fragment-identifier.
Arbitrary MIME content is included in the BEEP payload by using a
<a href=3D"#RFC2387">"multipart/related"</a>[6],
identified using a <a href=3D"#RFC2392">"cid" URL</a>[7],
and the XML control document occurs as the start of the =
"multipart/related",
e.g.,
</p>
</font><pre>   =20
    C: MSG 1 1 . 42 1234
    C: Content-Type: multipart/related; boundary=3D"boundary";
    C:               start=3D"&lt;1@example.com>";
    C:               type=3D"text/xml"
    C:=20
    C: --boundary
    C: Content-Type: text/xml
    C: Content-ID: &lt;1@example.com>
    C:=20
    C: &lt;data originator=3D'fred@example.com'
    C:       content=3D'cid:2@example.com'>
    C:     &lt;recipient identity=3D'barney@example.com' />
    C: &lt;/data>
    C: --boundary
    C: Content-Type: image/gif
    C: Content-Transfer-Encoding: binary
    C: Content-ID: &lt;2@example.com>
    C:=20
    C: ...
    C: --boundary--
    C: END
</pre><font face=3D"verdana, helvetica, arial, sans-serif" size=3D"2">

<p>
Because BEEP provides an 8bit-wide path, a "transformative"
Content-Transfer-Encoding
(e.g., "base64" or "quoted-printable")
should not be used.
Further,
note that <a href=3D"#RFC2045">MIME</a>[8] requires that the value
of the "Content-ID" header be globally unique.
</p>

<p>
If the arbitrary MIME content is itself an XML document,
it may be contained with the control document directly,
and identified using a URI-reference consisting of only a
fragment-identifier,
e.g.,
</p>
</font><pre>   =20
    C: MSG 1 1 . 42 283
    C: Content-Type: text/xml
    C:=20
    C: &lt;data originator=3D'fred@example.com' content=3D'#Content'>
    C:     &lt;recipient identity=3D'barney@example.com' />
    C:     &lt;data-content Name=3D'Content'>
    C:         &lt;statusResponse transID=3D'86'>
    C:             &lt;destination identity=3D'barney@example.com'>
    C:                 &lt;reply code=3D'250' />
    C:             &lt;/destination>
    C:         &lt;statusResponse>
    C:     &lt;/data-content>
    C: &lt;/data>
    C: END
</pre><font face=3D"verdana, helvetica, arial, sans-serif" size=3D"2">

<p>

</p>

<h4><a name=3D"anchor13">4.2</a>&nbsp;Profile Identification and =
Initialization</h4>

<p>
The IMXP is identified as
</p>
</font><pre>
    http://xml.resource.org/profiles/IMXP
</pre><font face=3D"verdana, helvetica, arial, sans-serif" size=3D"2">

<p>
in the BEEP "profile" element during channel creation.
</p>

<p>
No elements are required to be exchanged during channel creation;
however, in the endpoint-relay mode,
the BEEP initiator will typically include an "attach" element during
channel creation, e.g.,
</p>
</font><pre>
    &lt;start number=3D'1'>
        &lt;profile uri=3D'http://xml.resource.org/profiles/IMXP'>
            &lt;![CDATA[&lt;attach endpoint=3D'fred@example.com'
                             transID=3D'1' />]]&gt;
        &lt;/profile>
    &lt;/start>
</pre><font face=3D"verdana, helvetica, arial, sans-serif" size=3D"2">

<p>
Similarly,
in the relay-relay mode,
the BEEP initiator will typically include an "bind" element during
channel creation, e.g.,
</p>
</font><pre>
    &lt;start number=3D'1'>
        &lt;profile uri=3D'http://xml.resource.org/profiles/IMXP'>
            &lt;![CDATA[&lt;bind relay=3D'example.com'
                           transID=3D'1' />]]&gt;
        &lt;/profile>
    &lt;/start>
</pre><font face=3D"verdana, helvetica, arial, sans-serif" size=3D"2">

<h4><a name=3D"anchor14">4.3</a>&nbsp;Message Syntax</h4>

<p>
<a href=3D"#imxp-core.dtd">The IMXP Core DTD</a> defines the BEEP =
payloads that are
used in the IMXP.
</p>

<p>

</p>

<h4><a name=3D"imxp.messages">4.4</a>&nbsp;Message Semantics</h4>

<h4><a name=3D"operation.attach">4.4.1</a>&nbsp;The Attach =
Operation</h4>

<p>
When an application wants to attach to the relaying mesh as a given
endpoint,
it sends an "attach" element to a relay,
e.g.,
</p>
</font><pre>
    +-------+                  +-------+
    |       | -- attach -----> |       |
    | appl. |                  | relay |
    |       | &lt;--------- ok -- |       |
    +-------+                  +-------+

  C: &lt;attach endpoint=3D'fred@example.com' transID=3D'1' />
  S: &lt;ok />

or

    +-------+                  +-------+
    |       | -- attach -----> |       |
    |       |                  |       |
    |       | &lt;--------- ok -- |       |
    | appl. |                  | relay |
    |       | -- attach -----> |       |
    |       |                  |       |
    |       | &lt;--------- ok -- |       |
    +-------+                  +-------+

  C: &lt;attach endpoint=3D'fred@example.com' transID=3D'1' />
  S: &lt;ok />
  C: &lt;attach endpoint=3D'wilma@example.com' transID=3D'2' />
  S: &lt;ok />

or

    +-------+                  +-------+
    |       | -- attach -----> |       |
    | appl. |                  | relay |
    |       | &lt;------ error -- |       |
    +-------+                  +-------+

  C: &lt;attach endpoint=3D'fred@example.com' transID=3D'1' />
  S: &lt;error code=3D'537'>access denied&lt;/error>
</pre><font face=3D"verdana, helvetica, arial, sans-serif" size=3D"2">

<p>

</p>

<p>
The "attach" element has an "endpoint" attribute,
a "transID" attribute,
and contains zero or more "option" elements:

<ul class=3D"text">

<li>
the "endpoint" attribute specifies the endpoint that the
application wants to attach as;
</li>

<li>
the "transID" attribute specifies the transaction-identifier
associated with this operation; and,
</li>

<li>
the "option" elements,
if any,
specify additional processing options
(<a href=3D"#imxp.options">IMXP Options</a>).
</li>

</ul>

</p>

<p>
When a relay receives an "attach" element,
it performs these steps:

<ol class=3D"text">

<li>
If the transaction-identifier refers to a previous,
non-terminated operation on this BEEP channel,
an "error" element having code 555 is returned.
</li>

<li>
If the relay is in a different administrative domain than this endpoint,
an "error" element having code 553 is returned.
</li>

<li>
If the application is not authorized to attach as this endpoint,
an "error" element having code 537 is returned.
</li>

<li>
If any options are present,
they are examined.
</li>

<li>
If another application has already attached as this endpoint,
an "error" element having code 554 is returned.
</li>

<li>
Otherwise,
the application is bound as this endpoint,
and an "ok" element is returned.
</li>

</ol>

</p>

<p>

</p>

<h4><a name=3D"operation.bind">4.4.2</a>&nbsp;The Bind Operation</h4>

<p>
When an application wants to identify itself as a relay,
it sends a "bind" element to another relay,
e.g.,
</p>
</font><pre>
    +-------+                  +-------+
    |       | -- bind -------> |       |
    | relay |                  | relay |
    |   #1  | &lt;--------- ok -- |   #2  |
    +-------+                  +-------+

  C: &lt;bind relay=3D'example.com' transID=3D'1' />
  S: &lt;ok />

or

    +-------+                  +-------+
    |       | -- bind -------> |       |
    |       |                  |       |
    |       | &lt;--------- ok -- |       |
    | relay |                  | relay |
    |   #1  | -- bind -------> |   #2  |
    |       |                  |       |
    |       | &lt;--------- ok -- |       |
    +-------+                  +-------+

  C: &lt;bind relay=3D'example.com' transID=3D'1' />
  S: &lt;ok />
  C: &lt;bind relay=3D'rubble.com' transID=3D'1' />
  S: &lt;ok />

or

    +-------+                  +-------+
    |       | -- bind -------> |       |
    | relay |                  | relay |
    |   #1  | &lt;------ error -- |   #2  |
    +-------+                  +-------+

  C: &lt;bind relay=3D'example.com' transID=3D'1' />
  S: &lt;error code=3D'537'>access denied&lt;/error>
</pre><font face=3D"verdana, helvetica, arial, sans-serif" size=3D"2">

<p>

</p>

<p>
The "bind" element has a "relay" attribute,
a "transID" attribute,
and contains zero or more "option" elements:

<ul class=3D"text">

<li>
the "relay" attribute specifies the administrative domain on whose
behalf the application wants to serve;
</li>

<li>
the "transID" attribute specifies the transaction-identifier
associated with this operation; and,
</li>

<li>
the "option" elements,
if any,
specify additional processing options
(<a href=3D"#imxp.options">IMXP Options</a>).
</li>

</ul>

</p>

<p>
When a relay receives an "bind" element,
it performs these steps:

<ol class=3D"text">

<li>
If the transaction-identifier refers to a previous,
non-terminated operation on this BEEP channel,
an "error" element having code 555 is returned.
</li>

<li>
The relay performs an inverse DNS lookup on the application's IP
address,
yielding a PTR RR containing a domain name.
The relay then performs a DNS lookup on the resulting domain name,
yielding one or more A RRs.
If none of the IP addresses in the A RRs match the application's IP =
address,
an "error" element having code 553 is returned.
</li>

<li>
The relay performs the <a href=3D"#RFC2782">SRV
algorithm</a>[4] algorithm for the desired administrative domain
(i.e., using a service of "imxp-mesh" and a protocol of "tcp").
The relay compares the domain name in the PTR RR and the application's
TCP port number to the pairs of domain names and TCP port numbers
found using the SRV algorithm.
If none match,
an "error" element having code 537 is returned.
</li>

<li>
If the application is not authorized to bind on behalf of this
administrative domain,
an "error" element having code 537 is returned.
</li>

<li>
If any options are present,
they are examined.
</li>

<li>
Otherwise,
the application is accepted as serving this administrative domain,
and an "ok" element is returned.
</li>

</ol>

</p>

<p>

</p>

<h4><a name=3D"anchor15">4.4.3</a>&nbsp;The Terminate Operation</h4>

<p>
When an application or relay wants to release an attachment
or binding,
it sends a "terminate" element,
e.g.,
</p>
</font><pre>   =20
    +-------+                  +-------+
    |       | -- terminate --> |       |
    | appl. |                  | relay |
    |       | &lt;--------- ok -- |       |
    +-------+                  +-------+

  C: &lt;terminate transID=3D'1' />
  S: &lt;ok />

or

    +-------+                  +-------+
    |       | -- terminate --> |       |
    | appl. |                  | relay |
    |       | &lt;------ error -- |       |
    +-------+                  +-------+

  C: &lt;terminate transID=3D'13' />
  S: &lt;error code=3D'550'>unknown transaction-identifier&lt;/error>

or

    +-------+                  +-------+
    |       | &lt;-- terminate -- |       |
    | appl. |                  | relay |
    |       | -- ok ---------> |       |
    +-------+                  +-------+

  C: &lt;terminate transID=3D'1' />
  S: &lt;ok />
</pre><font face=3D"verdana, helvetica, arial, sans-serif" size=3D"2">

<p>
The "terminate" element has a "transID" attribute
that specifies the transaction-identifier associated a previous
attach or bind operation, and has no content.
</p>

<p>
When an application or relay receives a "terminate" element,
it performs these steps:

<ol class=3D"text">

<li>
If the transaction-identifier does not refer to a previous
unterminated operation on this BEEP channel,
an "error" element having code 550 is returned.
</li>

<li>
Otherwise,
the application is no longer bound as an endpoint or a relay,
and an "ok" element is returned.
</li>

</ol>

</p>

<h4><a name=3D"operation.data">4.4.4</a>&nbsp;The Data Operation</h4>

<p>
When an application or relay wants to transmit data over the
relaying mesh,
it sends a "data" element,
e.g.,
</p>
</font><pre>
    +-------+                  +-------+
    |       | -- data -------> |       |
    | appl. |                  | relay |
    |   #1  | &lt;--------- ok -- |       |
    +-------+                  +-------+

  C: &lt;data originator=3D'fred@example.com' =
content=3D'cid:1@example.com'>
         &lt;recipient identity=3D'barney@example.com' />
     &lt;/data>
  S: &lt;ok />

or

    +-------+                  +-------+
    |       | -- data -------> |       |
    | appl. |                  | relay |
    |   #1  | &lt;------ error -- |       |
    +-------+                  +-------+

  C: &lt;data originator=3D'fred@example.com' =
content=3D'cid:1@example.com'>
         &lt;recipient identity=3D'barney@example.com' />
     &lt;/data>
  S: &lt;error code=3D'450'>barney@example.com not attached&lt;/error>

or

                               +-------+                  +-------+
                               |       | -- data -------> |       |
                               | relay |                  | appl. |
                               |       | &lt;--------- ok -- |   #2  |
                               +-------+                  +-------+
   =20
  C: &lt;data originator=3D'fred@example.com' =
content=3D'cid:1@example.com'>
         &lt;recipient identity=3D'barney@example.com' />
     &lt;/data>
  S: &lt;ok />
</pre><font face=3D"verdana, helvetica, arial, sans-serif" size=3D"2">

<p>

</p>

<p>
The "data" element has an "originator" and a "content" attribute,
and contains one or more "recipient" elements,
zero or more "option" elements,
and, optionally, a "data-content" element:

<ul class=3D"text">

<li>
the "originator" attribute specifies the endpoint sending the
data;
</li>

<li>
the "content" attribute is a URI-reference that specifies the
contents of the data
(c.f., <a href=3D"#imxp.xml-and-mime">Use of XML and MIME</a>);
</li>

<li>
each "recipient" element refers to an endpoint destination for the
data;
</li>

<li>
the "option" elements,
if any,
specify additional processing options
(<a href=3D"#imxp.options">IMXP Options</a>),
termed per-data options; and,
</li>

<li>
the "data-content" element,
if present,
specifies a nested XML entity using a URI fragment-identifier as the
value of the "content" attribute.
</li>

</ul>

Each "recipient" element has an "identity" attribute,
and contains zero or more option elements:

<ul class=3D"text">

<li>
the "identity" attribute specifies the destination endpoint;
and
</li>

<li>
the "option" elements,
if any,
specify additional processing options for this recipient,
termed per-recipient options.
</li>

</ul>

</p>

<p>

</p>

<h4><a name=3D"relay.data">4.4.4.1</a>&nbsp;Relay Processing of =
Data</h4>

<p>
When a relay receives a "data" element,
it performs these steps:

<ol class=3D"text">

<li>
If the BEEP client is not authorized to originate or relay data on
behalf of the "originator" endpoint,
an "error" element having code 537 is returned.
</li>

<li>
If any per-data options are present,
they are examined.
</li>

<li>
For each recipient:

<ol class=3D"text">

<li>
If any per-recipient options are present,
they are examined.
</li>

<li>
If the recipient endpoint is not in the administrative domain
associated with the relay,
then an IMXP session is established to a relay that accepts data for
the recipient's administrative domain,=20
and a new "data" element,
containing only that "recipient" element (and all applicable options),
is sent to that relay.
<br>
<br>

If no errors
(e.g., an IMXP session can not be established)
occur during processing,
and if the recipient's relay returns an "ok" element,
then the recipient is considered to be successfully processed.
</li>

<li>
Otherwise,
the IMXP access service must check that the originator endpoint is
allowed to communicate with the recipient endpoint
(the recipient's <a href=3D"#IMXP-ACCESS">access entry</a>[9] must =
contain
a "core:data" token for the originator),
and the recipient endpoint must be currently attached.
<br>
<br>

If so,
a new "data" element
(containing only that "recipient" element)
is sent to the corresponding application,
and the recipient is considered to be successfully processed.
</li>

</ol>

</li>

<li>
If no recipients could be successfully processed,
an "error" element is returned;
otherwise,
an "ok" element is returned.
</li>

</ol>

Note that an implementation may choose to optimize its behavior by
grouping multiple recipients in a single "data" element that is
subsequently transmitted.
It may do so providing that the optimization retains these semantics
and any other semantics related to per-data and per-recipient options.
</p>

<p>
Finally,
note that a relay receiving a "data" element from an application may
be configured to add domain-specific options.
</p>

<p>

</p>

<h4><a name=3D"appl.data">4.4.4.2</a>&nbsp;Application Processing of =
Data</h4>

<p>
When an application receives a "data" element,
it performs these steps:

<ol class=3D"text">

<li>
If any per-data options are present,
they are not processed (but may be noted).
</li>

<li>
For each recipient:

<ol class=3D"text">

<li>
If any per-recipient options are present,
they are not processed (but may be noted).
</li>

<li>
If the application is not attached as the recipient endpoint,
then an error in processing has occurred.
</li>

<li>
Otherwise,
the "data" element is further processed in an application-specific =
manner,
and the recipient is considered to be successfully processed.
</li>

</ol>

</li>

<li>
If no recipients could be successfully processed,
an "error" element is returned;
otherwise,
an "ok" element is returned.
</li>

</ol>

</p>

<p>

</p>

<h4><a name=3D"imxp.access">4.5</a>&nbsp;IMXP Access Policies</h4>

<p>
Access to IMXP is provided by the juxtaposition of:

<ul class=3D"text">

<li>
authenticating as a BEEP peer;
</li>

<li>
attaching as an IMXP endpoint or binding as an IMXP relay; and,
</li>

<li>
being listed as an actor by the IMXP access service
(c.f., <a href=3D"#IMXP-ACCESS">[9]</a>).
</li>

</ul>

Each of these activities occurs according to the policies of the
relevant administrative domain:

<ul class=3D"text">

<li>
each administrative domain is responsible for keeping its own house in
order through "local provisioning"; and,
</li>

<li>
each administrative domain decides the level of trust to associate
with other administrative domains.
</li>

</ul>

</p>

<p>

</p>

<h4><a name=3D"anchor16">4.5.1</a>&nbsp;Use of Access Policies in the =
Endpoint-Relay Mode</h4>

<p>

<ul class=3D"text">

<li>
When an application wants to attach to the relaying mesh,
local provisioning maps BEEP peer identities to allowed IMXP endpoints
(c.f., Step 3 of <a href=3D"#operation.attach">The Attach =
Operation</a>).
<br>
<br>

Typically,
the identity function is used,
e.g.,
if an application authenticates itself
as the BEEP peer named as "fred@example.com",
it is allowed to attach
as the IMXP endpoint named as "fred@example.com".
<br>
<br>

Using the subaddress-specification convention of <a =
href=3D"#RFC2846">RFC 2846</a>[3],
an application authorized to attach as a given IMXP endpoint is also
authorized to attach as any sub-address of that IMXP endpoint,
e.g., an application authorized to attach as the IMXP endpoint
"fred@example.com" is also authorized to attach as the IMXP endpoint
"fred/wb@example.com".
</li>

<li>
When an application wants to send data,
local provisioning maps attached endpoints to allowed originators
(c.f., Step 1 of <a href=3D"#relay.data">Relay Processing of Data</a>).
<br>
<br>

Typically,
the identity function is used,
e.g.,
if an application attaches as the IMXP endpoint named as =
"fred@example.com",
it is allowed to send data originating from the same IMXP endpoint.
However,
other policies are permissible,
for example,
the administrative domain may allow the application attached as the
IMXP endpoint named as "wilma@example.com" to send data originating
as either "wilma@example.com" or "fred@example.com".
</li>

<li>
Finally,
when a relay is delivering to an endpoint within its own
administrative domain,
it consults the recipient's access entry looking for an entry having
the originator as an actor
(c.f., Step 3.3 of <a href=3D"#relay.data">Relay Processing of =
Data</a>).
</li>

</ul>

</p>

<p>

</p>

<h4><a name=3D"anchor17">4.5.2</a>&nbsp;Use of Access Policies in the =
Relay-Relay Mode</h4>

<p>

<ul class=3D"text">

<li>
When an application wants to bind as a relay on behalf of an
administrative domain,
in addition to Steps 2 and 3 of <a href=3D"#operation.bind">The Bind =
Operation</a>,
local provisioning may map BEEP peer identities to allowed IMXP relays
(c.f., Step 4).
<br>
<br>

If so,
then typically the identity function is used.
e.g.,
if an application authenticates itself as the BEEP peer named as =
"example.com",
it is allowed to bind as a relay on behalf of the administrative
domain "example.com".
</li>

<li>
When a relay is sending data,
no access policies, per se, are applied.
</li>

<li>
When a relay is receiving data,
local provisioning maps BEEP peer identities to allowed originators
(c.f., Step 1 of <a href=3D"#relay.data">Relay Processing of Data</a>).
<br>
<br>

Typically,
the identity function is used,
e.g.,
if a relay authenticates itself as being from the same
administrative domain as the originator of the data,
then the data is accepted.
<br>
<br>

In addition,
some relays may also be configured as "trusted" intermediaries,
so that if a BEEP peer authenticates itself as being from such a relay,
then the data is accepted.
</li>

</ul>

</p>

<a name=3D"imxp.options"><br><hr size=3D"1" shade=3D"0"></a>
<table border=3D"0" cellpadding=3D"0" cellspacing=3D"2" width=3D"30" =
height=3D"15" align=3D"right"><tr><td bgcolor=3D"#990000" =
align=3D"center" width=3D"30" height=3D"15"><a href=3D"#toc" =
CLASS=3D"link2"><font face=3D"monaco, MS Sans Serif" color=3D"#ffffff" =
size=3D"1"><b>&nbsp;TOC&nbsp;</b></font></a><br></td></tr></table>
<h3>5.&nbsp;IMXP Options</h3>

<p>
IMXP,
at its core,
provides a best-effort datagram service.
Options are used to alter the semantics of the core service.
</p>

<p>
The semantics of the IMXP "option" element are context-specific.
Accordingly,
the specification of an IMXP option must define:

<ul class=3D"text">

<li>
the identity of the option;
</li>

<li>
the context in which the option may appear;
</li>

<li>
what content, if any, is contained within the option; and,
</li>

<li>
the processing rules for the option.
</li>

</ul>

An <a href=3D"#option.registration">option registration template</a>
organizes this information.
</p>

<p>
An "option" element is contained within either a "data" element or
a "recipient" element,
either of which is termed the "containing element".
The "option" element has several attributes and contains arbitrary =
content:

<ul class=3D"text">

<li>
the "internal" and the "external" attributes,
exactly one of which is present,
uniquely identify the option;
</li>

<li>
the "targetHop" attribute specifies which relays should process the
option;
</li>

<li>
the "seeNoEvil" attribute specifies whether the option,
if unrecognized, may be safely ignored;
</li>

<li>
the "transID" attribute specifies a transaction-identifier for the
option; and,
</li>

<li>
the "localize" attribute,
if present,
specifies one or more language tokens,
each identifying a desirable language tag to be used if textual
diagnostics are returned to the originator.
</li>

</ul>

The value of the "internal" attribute is the IANA-registered name for
the option.
If the "internal" attribute is not present,
then the value of the "external" attribute is a URI or URI with a
fragment-identifier.
Note that a relative-URI value is not allowed.
</p>

<p>

</p>

<p>
The "targetHop" attribute specifies which relay(s) should
process the option:

<blockquote class=3D"text"><dl>

<dt>   this:</dt>
<dd>
the option applies to this relay,
and must be removed prior to transmitting the containing element.
</dd>

<dt>   final:</dt>
<dd>
the option applies to this relay,
only if the the relay is able to transmit the containing element
directly to the recipient.
</dd>

<dt>   all:</dt>
<dd>
the option applies to this relay and is
retained for the next.
</dd>

</dl></blockquote>

Note that a final relay does not remove any options as it transmits
the containing element directly to the recipient.
</p>

<p>
The "seeNoEvil" attribute specifies whether the relay
may ignore the option if it is unrecognized,
and is consulted only if the "targetHop" attribute indicates that the
option applies to that relay.
If the option applies,
and if the value of the "seeNoEvil" attribute is "false",
and if the relay does not "understand" the option,
then this is considered a processing error.
</p>

<p>

</p>

<h4><a name=3D"option.statusRequest">5.1</a>&nbsp;The statusRequest =
Option</h4>

<p>
<a href=3D"#statusRequest.definition">Registration: The statusRequest =
Option</a> contains the IMXP option
registration for the "statusRequest" option.
</p>

<p>
If this option is present,
then each applicable relay sends a "statusResponse" message to the
originator.
This is done by issuing a data operation
whose originator is the report service associated with the issuing =
relay,
whose recipient is the endpoint address of the "statusRequest"
originator,
and whose content is a "statusResponse" element.
</p>

<p>
A "statusRequest" option MUST NOT be present in any data operation
containing a "statusResponse" element.
</p>

<p>

</p>

<p>
Consider these examples:
</p>
</font><pre>
    +-------+                  +-------+
    |       | -- data -------> |       |
    | appl. |                  | relay |
    |   #1  | &lt;--------- ok -- |       |
    +-------+                  +-------+

  C: &lt;data originator=3D'fred@example.com' =
content=3D'cid:1@example.com'>
         &lt;recipient identity=3D'barney@example.com' />
         &lt;option internal=3D'statusRequest' targetHop=3D'final'
                 seeNoEvil=3D'false' transID=3D'86' />
     &lt;/data>
  S: &lt;ok />

                               +-------+                  +-------+
                               |       | -- data -------> |       |
                               | relay |                  | appl. |
                               |       | &lt;--------- ok -- |   #2  |
                               +-------+                  +-------+

  C: &lt;data originator=3D'fred@example.com' =
content=3D'cid:1@example.com'>
         &lt;recipient identity=3D'barney@example.com' />
     &lt;/data>
  S: &lt;ok />

    +-------+                  +-------+
    |       | &lt;------- data -- |       |
    | appl. |                  | relay |
    |   #1  | -- ok ---------> |       |
    +-------+                  +-------+

  C: &lt;data originator=3D'imxp=3Dreport@example.com' =
content=3D'#Content'>
         &lt;recipient identity=3D'fred@example.com' />
         &lt;data-content Name=3D'Content'>
             &lt;statusResponse transID=3D'86'>
                 &lt;destination identity=3D'barney@example.com'>
                     &lt;reply code=3D'250' />
                 &lt;/destination>
             &lt;statusResponse>
         &lt;/data-content>   =20
     &lt;/data>
  S: &lt;ok />






or

    +-------+                  +-------+
    |       | -- data -------> |       |
    | appl. |                  | relay |
    |       | &lt;--------- ok -- |   #1  |
    +-------+                  +-------+

  C: &lt;data originator=3D'fred@example.com' =
content=3D'cid:1@example.com'>
         &lt;recipient identity=3D'barney@rubble.com' />
         &lt;option internal=3D'statusRequest' targetHop=3D'final'
                 seeNoEvil=3D'false' transID=3D'86' />
     &lt;/data>
  S: &lt;ok />
                               +-------+                  +-------+
                               |       | -- data -------> |       |
                               | relay |                  | relay |
                               |   #1  | &lt;------ error -- |   #2  |
                               +-------+                  +-------+

  C: &lt;data originator=3D'fred@example.com' =
content=3D'cid:1@example.com'>
         &lt;recipient identity=3D'barney@rubble.com' />
         &lt;option internal=3D'statusRequest' targetHop=3D'final'
                 seeNoEvil=3D'false' transID=3D'86' />
     &lt;/data>
  S: &lt;error code=3D'550'>unknown endpoint identity&lt;/error>
 =20
    +-------+                  +-------+
    |       | &lt;------- data -- |       |
    | appl. |                  | relay |
    |       | -- ok ---------> |   #1  |
    +-------+                  +-------+

  C: &lt;data originator=3D'imxp=3Dreport@example.com' =
content=3D'#Content'>
         &lt;recipient identity=3D'fred@example.com' />
         &lt;data-content Name=3D'Content'>
             &lt;statusResponse transID=3D'86'>
                 &lt;destination identity=3D'barney@example.com'>
                     &lt;reply code=3D'550'>unknown endpoint
                                       identity&lt;/reply>
                 &lt;/destination>
             &lt;statusResponse>
         &lt;/data-content>
     &lt;/data>
  S: &lt;ok />







or   =20

    +-------+                  +-------+
    |       | -- data -------> |       |
    | appl. |                  | relay |
    |       | &lt;--------- ok -- |   #1  |
    +-------+                  +-------+

  C: &lt;data originator=3D'fred@example.com' =
content=3D'cid:1@example.com'>
         &lt;recipient identity=3D'barney@rubble.com' />
         &lt;option internal=3D'statusRequest' targetHop=3D'final'
                 seeNoEvil=3D'false' transID=3D'86' />
     &lt;/data>
  S: &lt;ok />
                               +-------+                  +-------+
                               |       | -- data -------> |       |
                               | relay |                  | relay |
                               |   #1  | &lt;--------- ok -- |   #2  |
                               +-------+                  +-------+

  C: &lt;data originator=3D'fred@example.com' =
content=3D'cid:1@example.com'>
         &lt;recipient identity=3D'barney@rubble.com' />
         &lt;option internal=3D'statusRequest' targetHop=3D'final'
                 seeNoEvil=3D'false' transID=3D'86' />
     &lt;/data>
  S: &lt;ok />
 =20
                               +-------+                  +-------+
                               |       | &lt;------- data -- |       |
                               | relay |                  | relay |
                               |   #1  | -- ok ---------> |   #2  |
                               +-------+                  +-------+

  C: &lt;data originator=3D'imxp=3Dreport@rubble.com' =
content=3D'#Content'>
          &lt;recipient identity=3D'fred@example.com' />
          &lt;data-content Name=3D'Content'>
              &lt;statusResponse transID=3D'86'>
              &lt;destination identity=3D'barney@rubble.com'>
                  &lt;reply code=3D'250' />
              &lt;/destination>
              &lt;statusResponse>
          &lt;/data-content>
      &lt;/data>
  S: &lt;ok />





    +-------+                  +-------+
    |       | -- data -------> |       |
    | appl. |                  | relay |
    |       | &lt;--------- ok -- |   #1  |
    +-------+                  +-------+
   =20
  C: &lt;data originator=3D'imxp=3Dreport@rubble.com' =
content=3D'#Content'>
         &lt;recipient identity=3D'fred@example.com' />
         &lt;data-content Name=3D'Content'>
             &lt;statusResponse transID=3D'86'>
                 &lt;destination identity=3D'barney@rubble.com'>
                     &lt;reply code=3D'250' />
                 &lt;/destination>
             &lt;statusResponse>
         &lt;/data-content>
     &lt;/data>
  S: &lt;ok />
</pre><font face=3D"verdana, helvetica, arial, sans-serif" size=3D"2">

<p>
Note that a trace of a data's passage through the relaying mesh
can be achieved by setting the "targetHop" attribute to "all".
</p>

<a name=3D"imxp.services"><br><hr size=3D"1" shade=3D"0"></a>
<table border=3D"0" cellpadding=3D"0" cellspacing=3D"2" width=3D"30" =
height=3D"15" align=3D"right"><tr><td bgcolor=3D"#990000" =
align=3D"center" width=3D"30" height=3D"15"><a href=3D"#toc" =
CLASS=3D"link2"><font face=3D"monaco, MS Sans Serif" color=3D"#ffffff" =
size=3D"1"><b>&nbsp;TOC&nbsp;</b></font></a><br></td></tr></table>
<h3>6.&nbsp;IMXP Services</h3>

<p>
IMXP,
at its core,
provides a best-effort datagram service.
Errors are reported through the use of a co-resident IMXP report =
service.
All other IMXP services are provided on top of the relaying mesh,
e.g.,
</p>
</font><pre>
   +----------+     +----------+    +----------+
   |   IMXP   |     |   IMXP   |    |          |
   |  access  |     | presence |    |   ...    |=20
   | service  |     | service  |    |          |=20
   +----------+     +----------+    +----------+
        |                |               |
        |                |               |
+------------------------------------------------+---------+
|                                                |  IMXP   |
|                    IMXP core                   |  report |
|                                                | service |
+------------------------------------------------+---------+
</pre><font face=3D"verdana, helvetica, arial, sans-serif" size=3D"2">

<p>
Applications communicate with IMXP services by sending data to a
"well-known endpoint" (WKE).
</p>

<p>
The specification of an IMXP service must define:

<ul class=3D"text">

<li>
the WKE of the service;
</li>

<li>
the syntax of messages exchanged with the service;
</li>

<li>
the sequence of messages exchanged with the service; and,
</li>

<li>
what access control tokens are consulted by the service.
</li>

</ul>

A <a href=3D"#service.registration">service registration template</a>
organizes this information.
</p>

<p>
Note that both the IMXP <a href=3D"#IMXP-ACCESS">access</a>[9] and
<a href=3D"#IMXP-PRESENCE">presence</a>[10] services are logically
layered above the IMXP core;
however,
implementers may choose to physically co-reside these services with
IMXP relay software.
</p>

<p>
Finally,
note that within a single administrative domain,
the relaying mesh makes use of the IMXP access service in order to
determine if an originator is allowed to transmit data to a recipient
(c.f., Step 3.3 of <a href=3D"#relay.data">Relay Processing of Data</a>)

</p>

<p>

</p>

<h4><a name=3D"anchor18">6.1</a>&nbsp;Use of the IMXP Core DTD</h4>

<p>
The specification of an IMXP service may use definitions found in the
IMXP <a href=3D"#imxp-core.dtd">core DTD</a>.
For example,
the <a href=3D"#operation.reply">reply operation</a> is defined
to provide a common format for responses.
</p>

<h4><a name=3D"anchor19">6.1.1</a>&nbsp;Transaction-Identifiers</h4>

<p>
In using IMXP's transaction-identifiers,
note the following:

<ul class=3D"text">

<li>
In the endpoint-relay and relay-relay modes,
transaction-identifiers are meaningful only during the lifetime of a
BEEP channel.
<br>
<br>

For example,
when an application issues the attach operation,
the associated transaction-identifier has meaning only within the
context of the BEEP channel used for the attach operation.
When the BEEP connection is released,
the channel no longer exists and the application is no longer attached
to the relaying mesh.
</li>

<li>
In contrast,
when an application communicates with an IMXP service,
transaction-identifiers are often embedded in the data that is sent.
This means that transaction-identifiers are potentially long-lived.
<br>
<br>

For example,
an application may attach as an endpoint,
send data (containing an embedded transaction-identifier) to a service,
and,
some time later,
detach from the relaying mesh.
Later on,
a second application may attach as the same endpoint,
and send data of its own (also containing embedded =
transaction-identifiers).
Subsequently,
the second application may receive data from the service responding to
the first application's request and containing the
transaction-identifier used by the first application.
</li>

</ul>

To minimize the likelihood of ambiguities with long-lived
transaction-identifiers,
the values of transaction-identifiers generated by applications should
appear to be unpredictable.
</p>

<p>

</p>

<h4><a name=3D"operation.reply">6.1.2</a>&nbsp;The Reply Operation</h4>

<p>
Many IMXP services make use of a reply operation.
Accordingly,
<a href=3D"#imxp-core.dtd">The IMXP Core DTD</a> contains a definition =
of a "reply" element
that can be used for this purpose.
</p>

<p>
The "reply" element has a "code" attribute,
a "transID" attribute,
an optional "xml:lang" attribute,
and may contain arbitrary textual content:

<ul class=3D"text">

<li>
the "code" element specifies a three-digit reply code
(c.f., <a href=3D"#imxp.reply-codes">Reply Codes</a>);
</li>

<li>
the "transID" attribute specifies the transaction-identifier
corresponding to this reply;
</li>

<li>
the "xml:lang" attribute,
if present,
specifies the language that the element's content is written in; and,
</li>

<li>
the textual content is a diagnostic (possibly multiline) which is
meaningful to implementers,
perhaps administrators,
and possibly even users.
</li>

</ul>

</p>

<p>

</p>

<h4><a name=3D"service.report">6.2</a>&nbsp;The Report Service</h4>

<p>
<a href=3D"#report.definition">Registration: The Report Service</a> =
contains the IMXP service
registration for the report service:

<ul class=3D"text">

<li>
Within an administrative domain,
the service is addressed using the well-known endpoint of
"imxp=3Dreport".
</li>

<li>
<a href=3D"#imxp-report.dtd">The Report Service DTD</a> defines the =
syntax of the
operations exchanged with the service.
</li>

<li>
A consumer of the service does not initiate communications with the
service.
</li>

<li>
The service initiates communications by sending data containing the
"statusResponse" operation.
</li>

</ul>

</p>

<p>
Unlike other IMXP services,
the report service is co-resident with the IMXP core -- the report =
service is
provided by each and every relay.
</p>

<p>
If a relay processes a
<a href=3D"#option.statusRequest">"statusRequest" option</a>,
then it sends data to the originator containing a
<a href=3D"#imxp-report.dtd">"statusResponse" element</a>.
</p>

<p>
The "statusResponse" element has a "transID" attribute and contains
one or more "destination" elements:

<ul class=3D"text">

<li>
the "transID" attribute specifies the value contained in the
"statusRequest" option; and,
</li>

<li>
each "destination" element has an "identity" attribute and contains
a "reply" element:

<ul class=3D"text">

<li>
the "identity" attribute specifies the recipient endpoint that is
being reported on; and,
</li>

<li>
the <a href=3D"#operation.reply">"reply" element</a>
specifies the delivery status of that recipient.
</li>

</ul>

</li>

</ul>

</p>

<a name=3D"anchor20"><br><hr size=3D"1" shade=3D"0"></a>
<table border=3D"0" cellpadding=3D"0" cellspacing=3D"2" width=3D"30" =
height=3D"15" align=3D"right"><tr><td bgcolor=3D"#990000" =
align=3D"center" width=3D"30" height=3D"15"><a href=3D"#toc" =
CLASS=3D"link2"><font face=3D"monaco, MS Sans Serif" color=3D"#ffffff" =
size=3D"1"><b>&nbsp;TOC&nbsp;</b></font></a><br></td></tr></table>
<h3>7.&nbsp;Registration Templates</h3>

<h4><a name=3D"option.registration">7.1</a>&nbsp;IMXP Option =
Registration Template</h4>

<p>
When an IMXP option is registered,
the following information is supplied:

<blockquote class=3D"text"><dl>

<dt>Option Identification:</dt>
<dd>
specify the NMTOKEN or the URI
that authoritatively identifies this option.
</dd>

<dt>Present in:</dt>
<dd>
specify the IMXP elements in which the
option may appear.
</dd>

<dt>Contains:</dt>
<dd>
specify the XML content that is contained
within the "option" element.
</dd>

<dt>Processing Rules:</dt>
<dd>
specify the processing rules
associated with the option.
</dd>

<dt>Contact Information:</dt>
<dd>
specify the postal and electronic
contact information for the author of the profile.
</dd>

</dl></blockquote>

</p>

<h4><a name=3D"service.registration">7.2</a>&nbsp;IMXP Service =
Registration Template</h4>

<p>
When an IMXP service is registered,
the following information is supplied:

<blockquote class=3D"text"><dl>

<dt>Well-Known Endpoint:</dt>
<dd>
specify the local-part of an
endpoint identity,
starting with "imxp=3D".
</dd>

<dt>Syntax of Messages Exchanged:</dt>
<dd>
specify the elements
exchanged with the service.
</dd>

<dt>Sequence of Messages Exchanged:</dt>
<dd>
specify the order in
which data is exchanged with the service.
</dd>

<dt>Access Control Tokens:</dt>
<dd>
specify the token(s) used to
control access to the service (c.f., <a href=3D"#IMXP-ACCESS">[9]</a>).
</dd>

<dt>Contact Information:</dt>
<dd>
specify the postal and electronic
contact information for the author of the profile.
</dd>

</dl></blockquote>

</p>

<a name=3D"anchor21"><br><hr size=3D"1" shade=3D"0"></a>
<table border=3D"0" cellpadding=3D"0" cellspacing=3D"2" width=3D"30" =
height=3D"15" align=3D"right"><tr><td bgcolor=3D"#990000" =
align=3D"center" width=3D"30" height=3D"15"><a href=3D"#toc" =
CLASS=3D"link2"><font face=3D"monaco, MS Sans Serif" color=3D"#ffffff" =
size=3D"1"><b>&nbsp;TOC&nbsp;</b></font></a><br></td></tr></table>
<h3>8.&nbsp;Initial Registrations</h3>

<h4><a name=3D"imxp.definition">8.1</a>&nbsp;Registration: The IMXP =
Profile</h4>

<p>

<blockquote class=3D"text"><dl>

<dt>Profile Identification:</dt>
<dd>
<a =
href=3D"http://xml.resource.org/profiles/IMXP">http://xml.resource.org/pr=
ofiles/IMXP</a>
</dd>

<dt>Messages exchanged during Channel Creation:</dt>
<dd>
"attach", "bind"
</dd>

<dt>Messages starting one-to-one exchanges:</dt>
<dd>
"attach",
"bind", "terminate", or "data"
</dd>

<dt>Messages in positive replies:</dt>
<dd>
"ok"
</dd>

<dt>Messages in negative replies:</dt>
<dd>
"error"
</dd>

<dt>Messages in one-to-many exchanges:</dt>
<dd>
none
</dd>

<dt>Message Syntax:</dt>
<dd>
c.f., <a href=3D"#imxp-core.dtd">The IMXP Core DTD</a>
</dd>

<dt>Message Semantics:</dt>
<dd>
c.f., <a href=3D"#imxp.messages">Message Semantics</a>
</dd>

<dt>Contact Information:</dt>
<dd>
c.f., the "Authors' Addresses"
section of this memo
</dd>

</dl></blockquote>

</p>

<h4><a name=3D"imxp-gstn.definition">8.2</a>&nbsp;Registration: The IMXP =
Service-Selector for GSTN</h4>

<p>

<blockquote class=3D"text"><dl>

<dt>Service-Selector Name:</dt>
<dd>
IMXP
</dd>

<dt>Description of Use:</dt>
<dd>
Specifies endpoints for registered
IMXP services on the host indicated by the address' domain name,
c.f., <a href=3D"#imxp.services">IMXP Services</a>
</dd>

<dt>Security Considerations:</dt>
<dd>
The definition of a
service-related endpoint does not introduce security concerns, per se;
however,
because the defined endpoints are service control points,
the nature of messages sent to them may introduce security concerns
</dd>

<dt>Contact Information:</dt>
<dd>
c.f., the "Authors' Addresses"
section of this memo
</dd>

</dl></blockquote>

</p>

<p>

</p>

<h4><a name=3D"statusRequest.definition">8.3</a>&nbsp;Registration: The =
statusRequest Option</h4>

<p>

<blockquote class=3D"text"><dl>

<dt>Option Identification:</dt>
<dd>
statusRequest
</dd>

<dt>Present in:</dt>
<dd>
IMXP's "data" and "recipient" elements
</dd>

<dt>Contains:</dt>
<dd>
nothing
</dd>

<dt>Processing Rules:</dt>
<dd>
c.f.,
<a href=3D"#option.statusRequest">The statusRequest Option</a>
</dd>

<dt>Contact Information:</dt>
<dd>
c.f., the "Authors' Addresses"
section of this memo
</dd>

</dl></blockquote>

</p>

<h4><a name=3D"report.definition">8.4</a>&nbsp;Registration: The Report =
Service</h4>

<p>

<blockquote class=3D"text"><dl>

<dt>Well-Known Endpoint:</dt>
<dd>
imxp=3Dreport
</dd>

<dt>Syntax of Messages Exchanged:</dt>
<dd>
c.f.,
<a href=3D"#imxp-report.dtd">The Report Service DTD</a>
</dd>

<dt>Sequence of Messages Exchanged:</dt>
<dd>
c.f.,
<a href=3D"#service.report">The Report Service</a>
</dd>

<dt>Access Control Tokens:</dt>
<dd>
none
</dd>

<dt>Contact Information:</dt>
<dd>
c.f., the "Authors' Addresses"
section of this memo
</dd>

</dl></blockquote>

</p>

<a name=3D"anchor22"><br><hr size=3D"1" shade=3D"0"></a>
<table border=3D"0" cellpadding=3D"0" cellspacing=3D"2" width=3D"30" =
height=3D"15" align=3D"right"><tr><td bgcolor=3D"#990000" =
align=3D"center" width=3D"30" height=3D"15"><a href=3D"#toc" =
CLASS=3D"link2"><font face=3D"monaco, MS Sans Serif" color=3D"#ffffff" =
size=3D"1"><b>&nbsp;TOC&nbsp;</b></font></a><br></td></tr></table>
<h3>9.&nbsp;DTDs</h3>

<p>
The IM COMMON DTD is defined in Section 6 of
<a href=3D"#IM-COMMON">[11]</a>.
</p>

<h4><a name=3D"imxp-core.dtd">9.1</a>&nbsp;The IMXP Core DTD</h4>
</font><pre>
&lt;!--
  DTD for the IMXP core, as of 2000-09-19


  Refer to this DTD as:

    &lt;!ENTITY % IMXPCORE PUBLIC "-//Blocks//DTD IMXP CORE//EN"
               "http://xml.resource.org/profiles/IMXP/imxp-core.dtd">
    %IMXPCORE;
  -->=20


&lt;!ENTITY % IMCOMMON PUBLIC "-//Blocks//DTD IM COMMON//EN"
           "http://xml.resource.org/syntaxes/IM/im-common.dtd">
%IMCOMMON;


&lt;!--
  DTD data types:

       entity        syntax/reference     example
       =3D=3D=3D=3D=3D=3D        =
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D     =
=3D=3D=3D=3D=3D=3D=3D
    IMXP endpoint
       ENDPOINT      addr-spec,            fred@example.com
                     c.f., [RFC-0822]    =20

    fully-qualified domain-name
        FQDN         c.f., [RFC-1034]      example.com

    zero or more language tags
        LOCS         NMTOKENS              "en-US"

    a 3-digit reply code
        XYZ           [1-5][1-9][1-9]      500
  -->

&lt;!ENTITY  % ENDPOINT  "CDATA">
&lt;!ENTITY  % FQDN      "NMTOKEN">
&lt;!ENTITY  % LOCS      "NMTOKEN">
&lt;!ENTITY  % XYZ       "CDATA">
   =20






&lt;!--
  BEEP profile http://xml.resource.org/profiles/IMXP
 =20
     role       MSG         RSP         ERR
    =3D=3D=3D=3D=3D=3D      =3D=3D=3D         =3D=3D=3D         =
=3D=3D=3D
      I         attach      ok          error=20

    I or L      bind        ok          error=20

    I or L      terminate   ok          error=20

    I or L      data        ok          error=20
  -->


&lt;!ELEMENT attach      (option*)>
&lt;!ATTLIST attach
          endpoint    %ENDPOINT;        #REQUIRED
          transID     %UNIQID;          #REQUIRED>


&lt;!ELEMENT bind        (option*)>
&lt;!ATTLIST bind
          relay       %FQDN;            #REQUIRED
          transID     %UNIQID;          #REQUIRED>


&lt;!ELEMENT terminate   EMPTY>
&lt;!ATTLIST terminate
          transID     %UNIQID;          #REQUIRED>


&lt;!ELEMENT data        (recipient+,option*,data-content?)>
&lt;!ATTLIST data
          originator  %ENDPOINT;        #REQUIRED
          content     %URI;             #REQUIRED>
   =20
&lt;!ELEMENT recipient   (option*)>
&lt;!ATTLIST recipient
          identity    %ENDPOINT;        #REQUIRED>

&lt;!ELEMENT data-content
                      ANY>
&lt;!ATTLIST Name        ID                #REQUIRED>





&lt;!ELEMENT ok          EMPTY>

&lt;!ELEMENT error       (#PCDATA)>
&lt;!ATTLIST error
          code        %XYZ;              #REQUIRED
          xml:lang    %LANG;             #IMPLIED>

&lt;!ELEMENT reply       (#PCDATA)>
&lt;!ATTLIST reply
          code        %XYZ;             #REQUIRED
          transID     %UNIQID;          #REQUIRED
          xml:lang    %LANG;            #IMPLIED>


&lt;!-- either the "internal" or the "external" attribute is present in
     an option -->

&lt;!ELEMENT option      ANY>
&lt;!ATTLIST option
          internal    NMTOKEN           ""
          external    %URI;             ""
          targetHop   (this|final|all)  "final"
          seeNoEvil   (true|false)      "true"
          transID     %UNIQID;          #REQUIRED
          localize    %LOCS;            "i-default">

</pre><font face=3D"verdana, helvetica, arial, sans-serif" size=3D"2">

<p>

</p>

<h4><a name=3D"imxp-report.dtd">9.2</a>&nbsp;The Report Service DTD</h4>
</font><pre>
&lt;!--
  DTD for the IMXP report service, as of 2000-06-11


  Refer to this DTD as:

    &lt;!ENTITY % IMXPREPORT PUBLIC "-//Blocks//DTD IMXP REPORT//EN"
             "http://xml.resource.org/profiles/IMXP/imxp-report.dtd">
    %IMXPREPORT;
  -->=20


&lt;!ENTITY % IMXPCORE PUBLIC "-//Blocks//DTD IMXP CORE//EN"
           "http://xml.resource.org/profiles/IMXP/imxp-core.dtd">
%IMXPCORE;


&lt;!--
  Synopsis of the IMXP report service

    service WKE: imxp=3Dreport

    message exchanges:

        service initiates    consumer replies
        =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D    =
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
        statusResponse       (nothing)

    access control tokens: none
  -->


&lt;!ELEMENT statusResponse
                      (destination+)>
&lt;!ATTLIST statusResponse
          transID     %TRANSID;         #REQUIRED>

&lt;!ELEMENT destination (reply)>
&lt;!ATTLIST destination
          identity    %ENDPOINT;        #REQUIRED>

</pre><font face=3D"verdana, helvetica, arial, sans-serif" size=3D"2">

<a name=3D"imxp.reply-codes"><br><hr size=3D"1" shade=3D"0"></a>
<table border=3D"0" cellpadding=3D"0" cellspacing=3D"2" width=3D"30" =
height=3D"15" align=3D"right"><tr><td bgcolor=3D"#990000" =
align=3D"center" width=3D"30" height=3D"15"><a href=3D"#toc" =
CLASS=3D"link2"><font face=3D"monaco, MS Sans Serif" color=3D"#ffffff" =
size=3D"1"><b>&nbsp;TOC&nbsp;</b></font></a><br></td></tr></table>
<h3>10.&nbsp;Reply Codes</h3>
</font><pre>
code    meaning
=3D=3D=3D=3D    =3D=3D=3D=3D=3D=3D=3D
250     transaction successful

421     service not available

450     requested action not taken

451     requested action aborted

454     temporary authentication failure

500     general syntax error (e.g., poorly-formed XML)

501     syntax error in parameters (e.g., non-valid XML)=20

504     parameter not implemented

530     authentication required

534     authentication mechanism insufficient

535     authentication failure

537     action not authorized for user

538     authentication mechanism requires encryption

550     requested action not taken

553     parameter invalid

554     transaction failed (e.g., policy violation)

555     transaction already in progress
</pre><font face=3D"verdana, helvetica, arial, sans-serif" size=3D"2">

<a name=3D"security"><br><hr size=3D"1" shade=3D"0"></a>
<table border=3D"0" cellpadding=3D"0" cellspacing=3D"2" width=3D"30" =
height=3D"15" align=3D"right"><tr><td bgcolor=3D"#990000" =
align=3D"center" width=3D"30" height=3D"15"><a href=3D"#toc" =
CLASS=3D"link2"><font face=3D"monaco, MS Sans Serif" color=3D"#ffffff" =
size=3D"1"><b>&nbsp;TOC&nbsp;</b></font></a><br></td></tr></table>
<h3>11.&nbsp;Security Considerations</h3>

<p>
Consult <a href=3D"#imxp.provisioning">Service Provisioning</a> and
<a href=3D"#imxp.access">IMXP Access Policies</a> for a discussion of =
security issues,
e.g., routing integrity.
In addition,
since IMXP is a profile of the BEEP,
consult <a href=3D"#BEEP-FRAMEWORK">[1]</a>'s Section 8 for a discussion =
of
BEEP-specific security issues.
</p>

<p>
In addition,
the <a href=3D"#option.statusRequest">statusRequest option</a>
may be used to expose private network topology.
Accordingly,
administrators may wish to choose to disable this option except at the
ingress/egress points for their domain.
</p>

<a name=3D"anchor23"><br><hr size=3D"1" shade=3D"0"></a>
<table border=3D"0" cellpadding=3D"0" cellspacing=3D"2" width=3D"30" =
height=3D"15" align=3D"right"><tr><td bgcolor=3D"#990000" =
align=3D"center" width=3D"30" height=3D"15"><a href=3D"#toc" =
CLASS=3D"link2"><font face=3D"monaco, MS Sans Serif" color=3D"#ffffff" =
size=3D"1"><b>&nbsp;TOC&nbsp;</b></font></a><br></td></tr></table>
<h3>12.&nbsp;IANA Considerations</h3>

<p>
The IANA maintains a list of:

<ul class=3D"text">

<li>
IMXP options,
c.f., <a href=3D"#imxp.options">IMXP Options</a> and <a =
href=3D"#option.registration">IMXP Option Registration Template</a>;
and,
</li>

<li>
IMXP services,
c.f., <a href=3D"#imxp.services">IMXP Services</a> and
<a href=3D"#service.registration">IMXP Service Registration =
Template</a>.
</li>

</ul>

</p>

<p>
The IANA makes the registrations specified in=20
<a href=3D"#imxp.definition">Registration: The IMXP Profile</a>,
<a href=3D"#imxp-gstn.definition">Registration: The IMXP =
Service-Selector for GSTN</a>,
<a href=3D"#statusRequest.definition">Registration: The statusRequest =
Option</a>,
and
<a href=3D"#report.definition">Registration: The Report Service</a>.
</p>
<a name=3D"rfc.references"><br><hr size=3D"1" shade=3D"0"></a>
<table border=3D"0" cellpadding=3D"0" cellspacing=3D"2" width=3D"30" =
height=3D"15" align=3D"right"><tr><td bgcolor=3D"#990000" =
align=3D"center" width=3D"30" height=3D"15"><a href=3D"#toc" =
CLASS=3D"link2"><font face=3D"monaco, MS Sans Serif" color=3D"#ffffff" =
size=3D"1"><b>&nbsp;TOC&nbsp;</b></font></a><br></td></tr></table>
<h3>
References</h3>
<table width=3D"99%" border=3D"0">
<tr><td class=3D"author-text" valign=3D"top"><b><a =
name=3D"BEEP-FRAMEWORK">[1]</a></b></td>
<td class=3D"author-text"><a href=3D"mailto:mrose@invisible.net">Rose, =
M.T.</a>, "<a =
href=3D"http://www.ietf.org/internet-drafts/draft-ietf-beep-framework-02.=
txt">The Blocks Extensible Exchange Protocol Framework</a>", =
draft-ietf-beep-framework-02 (work in progress), September =
2000.</td></tr>
<tr><td class=3D"author-text" valign=3D"top"><b><a =
name=3D"RFC0822">[2]</a></b></td>
<td class=3D"author-text">Crocker, D., "<a =
href=3D"ftp://ftp.isi.edu/in-notes/rfc822.txt">Standard for the format =
of ARPA Internet text messages</a>", RFC 822, STD 11, Aug =
1982.</td></tr>
<tr><td class=3D"author-text" valign=3D"top"><b><a =
name=3D"RFC2846">[3]</a></b></td>
<td class=3D"author-text">Allocchio, C., "<a =
href=3D"ftp://ftp.isi.edu/in-notes/rfc2846.txt">GSTN Address Element =
Extensions in E-mail Services</a>", RFC 2846, June 2000.</td></tr>
<tr><td class=3D"author-text" valign=3D"top"><b><a =
name=3D"RFC2782">[4]</a></b></td>
<td class=3D"author-text"><a href=3D"mailto:arnt@troll.no">Gulbrandsen, =
A.</a>, <a href=3D"mailto:">Vixie, P.</a> and <a =
href=3D"mailto:levone@microsoft.com">L. Esibov</a>, "<a =
href=3D"ftp://ftp.isi.edu/in-notes/rfc2782.txt">A DNS RR for specifying =
the location of services (DNS SRV)</a>", RFC 2782, February =
2000.</td></tr>
<tr><td class=3D"author-text" valign=3D"top"><b><a =
name=3D"RFC2396">[5]</a></b></td>
<td class=3D"author-text"><a href=3D"mailto:timbl@w3.org">Berners-Lee, =
T.</a>, <a href=3D"mailto:fielding@ics.uci.edu">Fielding, R.T.</a> and =
<a href=3D"mailto:masinter@parc.xerox.com">L. Masinter</a>, "<a =
href=3D"ftp://ftp.isi.edu/in-notes/rfc2396.txt">Uniform Resource =
Identifiers (URI): Generic Syntax</a>", RFC 2396, August 1998.</td></tr>
<tr><td class=3D"author-text" valign=3D"top"><b><a =
name=3D"RFC2387">[6]</a></b></td>
<td class=3D"author-text"><a =
href=3D"mailto:XIson@cnj.digex.com">Levinson, E.</a>, "<a =
href=3D"ftp://ftp.isi.edu/in-notes/rfc2387.txt">The MIME =
Multipart/Related Content-type</a>", RFC 2387, August 1998.</td></tr>
<tr><td class=3D"author-text" valign=3D"top"><b><a =
name=3D"RFC2392">[7]</a></b></td>
<td class=3D"author-text"><a =
href=3D"mailto:XIson@cnj.digex.net">Levinson, E.</a>, "<a =
href=3D"ftp://ftp.isi.edu/in-notes/rfc2392.txt">Content-ID and =
Message-ID Uniform Resource Locators</a>", RFC 2392, August =
1998.</td></tr>
<tr><td class=3D"author-text" valign=3D"top"><b><a =
name=3D"RFC2045">[8]</a></b></td>
<td class=3D"author-text"><a href=3D"mailto:ned@innosoft.com">Freed, =
N.</a> and <a href=3D"mailto:nsb@nsb.fv.com">N. Borenstein</a>, "<a =
href=3D"ftp://ftp.isi.edu/in-notes/rfc2045.txt">Multipurpose Internet =
Mail Extensions (MIME) Part One: Format of Internet Message Bodies</a>", =
RFC 2045, November 1996.</td></tr>
<tr><td class=3D"author-text" valign=3D"top"><b><a =
name=3D"IMXP-ACCESS">[9]</a></b></td>
<td class=3D"author-text"><a href=3D"mailto:mrose@invisible.net">Rose, =
M.T.</a>, <a href=3D"mailto:gk@acm.org">Klyne, G.</a> and <a =
href=3D"mailto:dcrocker@brandenburg.com">D.H. Crocker</a>, "<a =
href=3D"http://www.ietf.org/internet-drafts/draft-mrose-imxp-access-01.tx=
t">The IMXP Access Service</a>", draft-mrose-imxp-access-01 (work in =
progress), September 2000.</td></tr>
<tr><td class=3D"author-text" valign=3D"top"><b><a =
name=3D"IMXP-PRESENCE">[10]</a></b></td>
<td class=3D"author-text"><a href=3D"mailto:mrose@invisible.net">Rose, =
M.T.</a>, <a href=3D"mailto:gk@acm.org">Klyne, G.</a> and <a =
href=3D"mailto:dcrocker@brandenburg.com">D.H. Crocker</a>, "<a =
href=3D"http://www.ietf.org/internet-drafts/draft-mrose-imxp-presence-01.=
txt">The IMXP Presence Service</a>", draft-mrose-imxp-presence-01 (work =
in progress), September 2000.</td></tr>
<tr><td class=3D"author-text" valign=3D"top"><b><a =
name=3D"IM-COMMON">[11]</a></b></td>
<td class=3D"author-text"><a =
href=3D"mailto:dcrocker@brandenburg.com">Crocker, D.H.</a>, <a =
href=3D"mailto:thanos@networkprojects.com">Diacakis, A.</a>, <a =
href=3D"mailto:flo@networkprojects.com">Mazzoldi, F.</a>, <a =
href=3D"mailto:huitema@microsoft.com">Huitema, C.</a>, <a =
href=3D"mailto:gk@acm.org">Klyne, G.</a>, <a =
href=3D"mailto:mrose@invisible.net">Rose, M.T.</a>, <a =
href=3D"mailto:jdrosen@dynamicsoft.com">Rosenberg, J.</a>, <a =
href=3D"mailto:rsparks@dynamicsoft.com">Sparks, R.</a> and <a =
href=3D"mailto:suga@flab.fujitsu.co.jp">H. Sugano</a>, "<a =
href=3D"http://www.ietf.org/internet-drafts/draft-mrose-impp-common-00.tx=
t">A Common Profile for Instant Messaging (CPIM)</a>", =
draft-mrose-impp-common-00 (work in progress), August 2000.</td></tr>
</table>

<a name=3D"rfc.authors"><br><hr size=3D"1" shade=3D"0"></a>
<table border=3D"0" cellpadding=3D"0" cellspacing=3D"2" width=3D"30" =
height=3D"15" align=3D"right"><tr><td bgcolor=3D"#990000" =
align=3D"center" width=3D"30" height=3D"15"><a href=3D"#toc" =
CLASS=3D"link2"><font face=3D"monaco, MS Sans Serif" color=3D"#ffffff" =
size=3D"1"><b>&nbsp;TOC&nbsp;</b></font></a><br></td></tr></table>
<h3>Authors' Addresses</h3>
<table width=3D"99%" border=3D"0" cellpadding=3D"0" cellspacing=3D"0">
<tr><td class=3D"author-text">&nbsp;</td>
<td class=3D"author-text">Marshall T. Rose</td></tr>
<tr><td class=3D"author-text">&nbsp;</td>
<td class=3D"author-text">Invisible Worlds, Inc.</td></tr>
<tr><td class=3D"author-text">&nbsp;</td>
<td class=3D"author-text">1179 North McDowell Boulevard</td></tr>
<tr><td class=3D"author-text">&nbsp;</td>
<td class=3D"author-text">Petaluma, CA  94954-6559</td></tr>
<tr><td class=3D"author-text">&nbsp;</td>
<td class=3D"author-text">US</td></tr>
<tr><td class=3D"author" align=3D"right">Phone:&nbsp;</td>
<td class=3D"author-text">+1 707 789 3700</td></tr>
<tr><td class=3D"author" align=3D"right">EMail:&nbsp;</td>
<td class=3D"author-text"><a =
href=3D"mailto:mrose@invisible.net">mrose@invisible.net</a></td></tr>
<tr><td class=3D"author" align=3D"right">URI:&nbsp;</td>
<td class=3D"author-text"><a =
href=3D"http://invisible.net/">http://invisible.net/</a></td></tr>
<tr cellpadding=3D"3"><td>&nbsp;</td><td>&nbsp;</td></tr>
<tr><td class=3D"author-text">&nbsp;</td>
<td class=3D"author-text">Graham Klyne</td></tr>
<tr><td class=3D"author-text">&nbsp;</td>
<td class=3D"author-text">Content Technologies Limited</td></tr>
<tr><td class=3D"author-text">&nbsp;</td>
<td class=3D"author-text">1220 Parkview</td></tr>
<tr><td class=3D"author-text">&nbsp;</td>
<td class=3D"author-text">Arlington Business Park</td></tr>
<tr><td class=3D"author-text">&nbsp;</td>
<td class=3D"author-text">Theale, Reading  RG7 4SA</td></tr>
<tr><td class=3D"author-text">&nbsp;</td>
<td class=3D"author-text">UK</td></tr>
<tr><td class=3D"author" align=3D"right">Phone:&nbsp;</td>
<td class=3D"author-text">+44 118 930 1300</td></tr>
<tr><td class=3D"author" align=3D"right">EMail:&nbsp;</td>
<td class=3D"author-text"><a =
href=3D"mailto:gk@acm.org">gk@acm.org</a></td></tr>
<tr cellpadding=3D"3"><td>&nbsp;</td><td>&nbsp;</td></tr>
<tr><td class=3D"author-text">&nbsp;</td>
<td class=3D"author-text">David H. Crocker</td></tr>
<tr><td class=3D"author-text">&nbsp;</td>
<td class=3D"author-text">Brandenburg Consulting</td></tr>
<tr><td class=3D"author-text">&nbsp;</td>
<td class=3D"author-text">675 Spruce Drive</td></tr>
<tr><td class=3D"author-text">&nbsp;</td>
<td class=3D"author-text">Sunnyvale, CA  94086</td></tr>
<tr><td class=3D"author-text">&nbsp;</td>
<td class=3D"author-text">US</td></tr>
<tr><td class=3D"author" align=3D"right">Phone:&nbsp;</td>
<td class=3D"author-text">+1 408 246 8253</td></tr>
<tr><td class=3D"author" align=3D"right">EMail:&nbsp;</td>
<td class=3D"author-text"><a =
href=3D"mailto:dcrocker@brandenburg.com">dcrocker@brandenburg.com</a></td=
></tr>
<tr><td class=3D"author" align=3D"right">URI:&nbsp;</td>
<td class=3D"author-text"><a =
href=3D"http://www.brandenburg.com/">http://www.brandenburg.com/</a></td>=
</tr>
</table>

<a name=3D"anchor24"><br><hr size=3D"1" shade=3D"0"></a>
<table border=3D"0" cellpadding=3D"0" cellspacing=3D"2" width=3D"30" =
height=3D"15" align=3D"right"><tr><td bgcolor=3D"#990000" =
align=3D"center" width=3D"30" height=3D"15"><a href=3D"#toc" =
CLASS=3D"link2"><font face=3D"monaco, MS Sans Serif" color=3D"#ffffff" =
size=3D"1"><b>&nbsp;TOC&nbsp;</b></font></a><br></td></tr></table>
<h3>Appendix A.&nbsp;Changes from draft-mrose-imxp-core-00</h3>

<p>

<ul class=3D"text">

<li>
Updated to reflect the current
<a href=3D"#BEEP-FRAMEWORK">BEEP framework</a>[1].
</li>

<li>
Relaying options passed to,
but not interpreted by,
endpoints.
</li>

<li>
The <a href=3D"#operation.bind">The Bind Operation</a> is introduced =
along with
authorization via reverse/forward DNS lookups.
</li>

<li>
<a href=3D"#imxp.access">IMXP Access Policies</a> includes an explicit =
discussion of
sub-addreses.
</li>

</ul>

</p>

<a name=3D"anchor25"><br><hr size=3D"1" shade=3D"0"></a>
<table border=3D"0" cellpadding=3D"0" cellspacing=3D"2" width=3D"30" =
height=3D"15" align=3D"right"><tr><td bgcolor=3D"#990000" =
align=3D"center" width=3D"30" height=3D"15"><a href=3D"#toc" =
CLASS=3D"link2"><font face=3D"monaco, MS Sans Serif" color=3D"#ffffff" =
size=3D"1"><b>&nbsp;TOC&nbsp;</b></font></a><br></td></tr></table>
<h3>Appendix B.&nbsp;Acknowledgements</h3>

<p>
The authors gratefully acknowledge the contributions of:
Darren New
and
Scott Pead.
</p>
<a name=3D"rfc.copyright"><br><hr size=3D"1" shade=3D"0"></a>
<table border=3D"0" cellpadding=3D"0" cellspacing=3D"2" width=3D"30" =
height=3D"15" align=3D"right"><tr><td bgcolor=3D"#990000" =
align=3D"center" width=3D"30" height=3D"15"><a href=3D"#toc" =
CLASS=3D"link2"><font face=3D"monaco, MS Sans Serif" color=3D"#ffffff" =
size=3D"1"><b>&nbsp;TOC&nbsp;</b></font></a><br></td></tr></table>
<h3>Full Copyright Statement</h3>
<p class=3D'copyright'>
Copyright (C) The Internet Society (2000). All Rights Reserved.</p>
<p class=3D'copyright'>
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published and
distributed, in whole or in part, without restriction of any kind,
provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.</p>
<p class=3D'copyright'>
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.</p>
<p class=3D'copyright'>
This document and the information contained herein is provided on an
&quot;AS IS&quot; basis and THE INTERNET SOCIETY AND THE INTERNET =
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TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.</p>
<h3>Acknowledgement</h3>
<p class=3D'copyright'>
Funding for the RFC editor function is currently provided by the
Internet Society.</p>
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