Network Working Group M. Rose
Internet-Draft Invisible Worlds, Inc.
Expires: June 1, 2001 G. Klyne
Baltimore Technologies
D. Crocker
Brandenburg Consulting
December 2000
The APEX Access Service
draft-ietf-apex-access-00
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
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Copyright Notice
Copyright (C) The Internet Society (2000). All Rights Reserved.
Abstract
This memo describes the APEX access service, addressed as the well-
known endpoint "apex=access". The access service is used to control
use of both the APEX "relaying mesh" and other APEX services.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Management of Access Information . . . . . . . . . . . . . . . 4
2.1 Retrieval of Access Information . . . . . . . . . . . . . . . 5
2.2 Update of Access Information . . . . . . . . . . . . . . . . . 6
3. Format of Access Entries . . . . . . . . . . . . . . . . . . . 7
4. The Access Service . . . . . . . . . . . . . . . . . . . . . . 9
4.1 Use of XML and MIME . . . . . . . . . . . . . . . . . . . . . 10
4.2 The Get Operation . . . . . . . . . . . . . . . . . . . . . . 11
4.3 The Set Operation . . . . . . . . . . . . . . . . . . . . . . 12
4.4 The Reply Operation . . . . . . . . . . . . . . . . . . . . . 14
5. Registration: The Access Service . . . . . . . . . . . . . . . 15
6. The Access Service DTD . . . . . . . . . . . . . . . . . . . . 16
7. Security Considerations . . . . . . . . . . . . . . . . . . . 18
References . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 19
A. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 20
B. Changes from IMXP . . . . . . . . . . . . . . . . . . . . . . 21
Full Copyright Statement . . . . . . . . . . . . . . . . . . . 22
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1. Introduction
This memo describes a access service that is built upon the APEX [1]
"relaying mesh". The APEX access service is used to control use of
both the relaying mesh and other APEX services.
APEX, at its core, provides a best-effort datagram service. Within
an administrative domain, all relays must be able to handle messages
for any endpoint within that domain. APEX services are logically
defined as endpoints but given their ubiquitous semantics they do not
necessarily need to be associated with a single physical endpoint.
As such, they may be provisioned co-resident with each relay within
an administrative domain, even though they are logically provided on
top of the relaying mesh, i.e.,
+----------+ +----------+ +----------+ +---------+
| APEX | | APEX | | APEX | | |
| access | | presence | | report | | ... |
| service | | service | | service | | |
+----------+ +----------+ +----------+ +---------+
| | | |
| | | |
+----------------------------------------------------------------+
| |
| APEX core |
| |
+----------------------------------------------------------------+
That is, applications communicate with an APEX service by exchanging
data with a "well-known endpoint" (WKE).
APEX applications communicate with the access service by exchanging
data with the well-known endpoint "apex=access" in the corresponding
administrative domain, e.g., "apex=access@example.com" is the
endpoint associated with the access service in the "example.com"
administrative domain.
Note that within a single administrative domain, the relaying mesh
makes use of the APEX access service in order to determine if an
originator is allowed to transmit data to a recipient (c.f., Step 5.3
of Section 4.4.4.1 of [1]).
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2. Management of Access Information
Management of access information falls into two categories:
o applications may retrieve the access entry associated with an
endpoint; and,
o applications may modify the access entry associated with an
endpoint.
Each is now described in turn.
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2.1 Retrieval of Access Information
When an application wants to retrieve the access entry associated
with an endpoint, it sends a "get" element to the service, e.g.,
+-------+ +-------+
| | -- data -------> | |
| appl. | | relay |
| | <--------- ok -- | |
+-------+ +-------+
C: <data content='#Content'>
<originator identity='fred@example.com' />
<recipient identity='apex=access@example.com' />
<data-content Name='Content'>
<get owner='fred@example.com' transID='1' />
</data-content>
</data>
S: <ok />
The service immediately responds with a set operation containing the
access entry and the same transaction-identifier, e.g.,
+-------+ +-------+
| | <------- data -- | |
| relay | |access |
| | -- ok ---------> | svc. |
+-------+ +-------+
C: <data content='#Content'>
<originator identity='apex=access@example.com' />
<recipient identity='fred@example.com' />
<data-content Name='Content'>
<set owner='fred@example.com' transID='1'
timeStamp='14 May 2000 13:32:00 -0800'>
<access owner='fred@example.com'
lastUpdate='14 May 2000 13:02:00 -0800'>
<entry actor='*@example.com'
actions='core:data presence:subscribe' />
<entry actor='*@*' actions='core:data' />
</access>
</set>
</data-content>
</data>
S: <ok />
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2.2 Update of Access Information
When an application wants to modify the access entry associated with
an endpoint, it sends a "set" element to the service, e.g.,
+-------+ +-------+
| | -- data -------> | |
| appl. | | relay |
| | <--------- ok -- | |
+-------+ +-------+
C: <data content='#Content'>
<originator identity='fred@example.com' />
<recipient identity='apex=access@example.com' />
<data-content Name='Content'>
<set owner='fred@example.com' transID='1'
timeStamp='14 May 2000 13:32:00 -0800'> ... </set>
</data-content>
</data>
S: <ok />
The service immediately responds with a reply operation containing
the same transaction-identifier, e.g.,
+-------+ +-------+
| | <------- data -- | |
| relay | |access |
| | -- ok ---------> | svc. |
+-------+ +-------+
C: <data content='#Content'>
<originator identity='apex=access@example.com' />
<recipient identity='fred@example.com' />
<data-content Name='Content'>
<reply code='250' transID='1' />
</data-content>
</data>
S: <ok />
Note that Step 5 of Section 4.3 requires that the "lastUpdate"
attribute of an access entry be supplied in order to update that
entry; accordingly, applications must successfully retrieve an access
entry prior to trying to update that entry.
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3. Format of Access Entries
Each administrative domain is responsible for maintaining an "access
entry" for each of its endpoints (regardless of whether those
endpoints are currently attached to the relaying mesh).
Section 6 defines the syntax for access entries. Each access entry
has an "owner" attribute, a "lastUpdate" attribute, and contains one
or more "entry" elements:
o the "owner" attribute specifies the endpoint associated with the
access entry;
o the "lastUpdate" attribute specifies the date and time that the
service last updated the access entry; and,
o each "entry" element specifies, with respect to the owner's
endpoint, an actor and zero or more allowed actions for that
actor.
Within an entry, actions are specified as service/operation pairs,
(e.g., "presence:publish" refers to the "publish" operation of the
"presence" service). To refer to all services and/or all operations,
the reserved value "all" is used (e.g., "all:data", "presence:all",
and so on). Note that the service specified as "core" is reserved
for use by the relaying mesh, e.g., the "core:data" action is
consulted by the relaying mesh (c.f., Step 3.3 of Section 4.4.3.1 of
[1]).
An actor is an APEX endpoint and is specified using the "addr-spec"
syntax specified in Section 3.4.1 of [2], i.e., the familiar
"local@domain" syntax. However, both the "local" and "domain" parts
may contain limited wildcarding:
o The "local" part is either:
* a literal string (e.g., "fred"); or,
* the value "apex=*", specifying all APEX services; or,
* the value "*", specifying any endpoint other than an APEX
service.
o The "domain" part is either:
* a FQDN (e.g., "example.com"); or,
* the value "*", specifying all administrative domains.
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Regardless of the "entry" elements present in an access entry, four
additional elements are always considered to exist at the end of the
access entry:
<entry actor='apex=*@domain' actions='all:all' />
<entry actor='apex=*@*' actions='core:data' />
<entry actor='local@domain' actions='all:all' />
<entry actor='*@*' actions='' />
where "local@domain" specifies the endpoint associated with the
access entry.
Ordering of "entry" elements within an access element is significant:
a process examining an access element selects the first "entry"
element that matches the actor in question. For example, consider
this access entry:
<access owner='fred@example.com'
lastUpdate='14 May 2000 13:02:00 -0800'>
<entry actor='wilma@example.com' actions='all:all' />
<entry actor='mr.slate@example.com' actions='core:data' />
<entry actor='*@example.com'
actions='core:data presence:subscribe presence:watch' />
<entry actor='*@*' actions='core:data' />
</access>
Briefly:
o For endpoints within the "example.com" administrative domain:
* "fred", "wilma", and all APEX services, are allowed access to
all operations for all APEX services;
* "mr.slate" is allowed access only to send data through the
relaying mesh; and,
* any other endpoint is allowed access to send data and invoke
the "subscribe" and "watch" operations of the APEX presence
service.
o For any endpoint outside the "example.com" administrative domain,
the endpoint is allowed access to send data, regardless of whether
it is an APEX service.
Note that although the four additional elements are always present,
the ordering semantics cause the final element to be unused.
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4. The Access Service
Section 5 contains the APEX service registration for the access
service:
o Within an administrative domain, the service is addressed using
the well-known endpoint of "apex=access".
o Section 6 defines the syntax of the operations exchanged with the
service.
o A consumer of the service initiates communications by sending data
containing either the get or set operation.
o The service replies to these operations, and does not initiate
communications.
An implementation of the service must maintain information about
access entries in persistent storage.
Consult Section 6.1.1 of [1] for a discussion on the properties of
long-lived transaction-identifiers.
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4.1 Use of XML and MIME
Section 4.1 of [1] describes how arbitrary MIME content is exchanged
as a BEEP [3] payload. For example, to transmit:
<data content='...'>
<originator identity='fred@example.com' />
<recipient identity='apex=access@example.com' />
</data>
where "..." refers to: <get owner='fred@example.com' transID='1' />
then the corresponding BEEP message might look like this:
C: MSG 1 2 . 42 1234
C: Content-Type: multipart/related; boundary="boundary";
C: start="<1@example.com>";
C: type="application/beep+xml"
C:
C: --boundary
C: Content-Type: application/beep+xml
C: Content-ID: <1@example.com>
C:
C: <data content='cid:2@example.com'>
C: <originator identity='fred@example.com' />
C: <recipient identity='apex=access@example.com' />
C: </data>
C: --boundary
C: Content-Type: application/beep+xml
C: Content-ID: <2@example.com>
C:
C: <get owner='fred@example.com' transID='1' />
C: --boundary--
C: END
or this:
C: MSG 1 1 . 42 267
C: Content-Type: application/beep+xml
C:
C: <data content='#Content'>
C: <originator identity='fred@example.com' />
C: <recipient identity='apex=access@example.com' />
C: <data-content Name='Content'>
C: <get owner='fred@example.com' transID='1' />
C: </data-content>
C: </data>
C: END
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4.2 The Get Operation
When an application wants to retrieve the access entry associated
with an endpoint, it sends a "get" element to the service.
The "get" element has an "owner" attribute, a "transID" attribute,
and no content:
o the "owner" attribute specifies the endpoint associated with the
access entry; and,
o the "transID" attribute specifies the transaction-identifier
associated with this operation.
When the service receives a "get" element, we refer to the "owner"
attribute of that element as the "subject", and the service performs
these steps:
1. If the subject is outside of this administrative domain, a
"reply" element having code 553 is sent to the originator.
2. If the subject does not refer to a valid endpoint, a "reply"
element having code 550 is sent to the originator.
3. If the subject's access entry does not contain a "access:get"
token for the originator, a "reply" element having code 537 is
sent to the originator.
4. Otherwise, a "set" element, corresponding to the subject's access
entry, is sent to the originator.
Regardless of whether a "set" or "reply" element is sent to the
originator, the "transID" attribute is identical to the value found
in the "get" element sent by the originator.
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4.3 The Set Operation
When an application wants to modify the access entry associated with
an endpoint, it sends a "set" element to the service.
The "set" element has an "owner" attribute, a "transID" attribute, a
"timeStamp" attribute, and contains an "access" element:
o the "owner" attribute specifies the endpoint to be associated with
the access entry;
o the "transID" attribute specifies the transaction-identifier
associated with this operation;
o the "timeStamp" attribute specifies the application's notion of
the current date and time; and,
o the "access" element contains the desired access entry for the
endpoint.
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When the service receives a "set" element, we refer to the "owner"
attribute of that element as the "subject", and the service performs
these steps:
1. If the "owner" attribute of the "set" element doesn't match the
"owner" attribute of the "access" element contained in the "set"
element, a "reply" element having code 503 is sent to the
originator.
2. If the subject is outside of this administrative domain, a
"reply" element having code 553 is sent to the originator.
3. If the subject does not refer to a valid endpoint, a "reply"
element having code 550 is sent to the originator.
4. If the subject's access entry does not contain a "access:set"
token for the originator, a "reply" element having code 537 is
sent to the originator.
5. If the "lastUpdate" attribute of the "set" element is not
semantically identical to the "lastUpdate" attribute of the
subject's access entry, a "reply" element having code 555 is sent
to the originator. (This allows a basic mechanism for atomic
updates.)
6. Otherwise:
1. The subject's access entry is updated from the "set" element.
2. The "lastUpdate" attribute of the access entry is set to the
service's notion of the current date time.
3. A "reply" element having code 250 is sent to the originator.
When sending the "reply" element, the "transID" attribute is
identical to the value found in the "set" element sent by the
originator.
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4.4 The Reply Operation
While processing operations, the service may respond with a "reply"
element. Consult Sections 10.2 and 6.1.2 of [1], respectively, for
the syntax and semantics of the reply operation.
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5. Registration: The Access Service
Well-Known Endpoint: apex=access
Syntax of Messages Exchanged: c.f., Section 6
Sequence of Messages Exchanged: c.f., Section 4
Access Control Tokens: access:get, access:set
Contact Information: c.f., the "Authors' Addresses" section of this
memo
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6. The Access Service DTD
<!--
DTD for the APEX access service, as of 2000-12-12
Refer to this DTD as:
<!ENTITY % APEXACCESS PUBLIC "-//IETF//DTD APEX ACCESS//EN"
"http://xml.resource.org/profiles/APEX/apex-access.dtd">
%APEXACCESS;
-->
<!ENTITY % APEXCORE PUBLIC "-//IETF//DTD APEX CORE//EN"
"http://xml.resource.org/profiles/APEX/apex-core.dtd">
%APEXCORE;
<!--
DTD data types:
entity syntax/reference example
====== ================ =======
access actor
ACTOR an ENDPOINT or a *@example.com
wildcard
-->
<!ENTITY % ACTOR "CDATA">
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<!--
Synopsis of the APEX access service
service WKE: apex=access
message exchanges:
consumer initiates service replies
================== ================
get set or reply
set reply
access control:
token target
========== ======
access:get for "owner" of "access" element
access:set for "owner" of "access" element
-->
<!ELEMENT get EMPTY>
<!ATTLIST get
owner %ENDPOINT; #REQUIRED
transID %UNIQID; #REQUIRED>
<!-- owner attributes must match in set and access -->
<!ELEMENT set (access)>
<!ATTLIST set
owner %ENDPOINT; #REQUIRED
transID %UNIQID; #REQUIRED
timeStamp %TIMESTAMP; #REQUIRED>
<!--
access entries
-->
<!ELEMENT access (entry+)>
<!ATTLIST access
owner %ENDPOINT; #REQUIRED
lastUpdate %TIMESTAMP; #REQUIRED>
<!ELEMENT entry EMPTY>
<!ATTLIST entry
actor %ACTOR; #REQUIRED
actions NMTOKENS "">
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7. Security Considerations
Consult Section [1]'s Section 11 for a discussion of security issues.
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References
[1] Rose, M., Klyne, G. and D. Crocker, "The Application Exchange
Core", draft-ietf-apex-core-00 (work in progress), February
2001.
[2] Resnick, P., "Internet Message Format", draft-drums-msg-fmt-09
(work in progress), September 2000.
[3] Rose, M., "The Blocks Extensible Exchange Protocol Core", RFC
3080, March 2001.
Authors' Addresses
Marshall T. Rose
Invisible Worlds, Inc.
131 Stony Circle
Suite 500
Santa Rosa, CA 95401
US
Phone: +1 707 578 2350
EMail: mrose@invisible.net
URI: http://invisible.net/
Graham Klyne
Baltimore Technologies
1220 Parkview
Arlington Business Park
Theale, Reading RG7 4SA
UK
Phone: +44 118 930 1300
EMail: gk@acm.org
David H. Crocker
Brandenburg Consulting
675 Spruce Drive
Sunnyvale, CA 94086
US
Phone: +1 408 246 8253
EMail: dcrocker@brandenburg.com
URI: http://www.brandenburg.com/
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Appendix A. Acknowledgements
The authors gratefully acknowledge the contributions of: Neil Cook,
Darren New, Chris Newman, and Scott Pead.
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Appendix B. Changes from IMXP
o s/IMXP/APEX/g
o Clarify the notion of co-residence for APEX services.
o Change data's originator from an attribute to an element.
o Change addr-spec reference from RFC 822 to [2].
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Full Copyright Statement
Copyright (C) The Internet Society (2000). All Rights Reserved.
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