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--------------------------------------------------------------------------------
2 Network Working Group M.T. Rose
3 Internet-Draft Invisible Worlds, Inc.
4 Expires: August 26, 2001 G. Klyne
5 Content Technologies Limited
6 D.H. Crocker
7 Brandenburg Consulting
8 February 25, 2001
10 The Application Exchange Core
11 draft-mrose-apex-core-03
13 Status of this Memo
15 This document is an Internet-Draft and is in full conformance with
16 all provisions of Section 10 of RFC2026.
18 Internet-Drafts are working documents of the Internet Engineering
19 Task Force (IETF), its areas, and its working groups. Note that other
20 groups may also distribute working documents as Internet-Drafts.
22 Internet-Drafts are draft documents valid for a maximum of six months
23 and may be updated, replaced, or obsoleted by other documents at any
24 time. It is inappropriate to use Internet-Drafts as reference
25 material or to cite them other than as "work in progress."
27 The list of current Internet-Drafts can be accessed at
28 http://www.ietf.org/ietf/1id-abstracts.txt.
30 The list of Internet-Draft Shadow Directories can be accessed at
31 http://www.ietf.org/shadow.html.
33 This Internet-Draft will expire on August 26, 2001.
35 Copyright Notice
37 Copyright (C) The Internet Society (2001). All Rights Reserved.
39 Abstract
41 This memo describes APEX, an extensible, asynchronous message
42 relaying service for application layer programs.
44 Table of Contents
46 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 4
47 1.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . 5
48 1.2 Architecture at a Glance . . . . . . . . . . . . . . . . . 6
49 2. Service Principles . . . . . . . . . . . . . . . . . . . . 8
50 2.1 Modes of Operation . . . . . . . . . . . . . . . . . . . . 8
51 2.2 Naming of Entities . . . . . . . . . . . . . . . . . . . . 9
52 3. Service Provisioning . . . . . . . . . . . . . . . . . . . 10
53 3.1 Connection Establishment . . . . . . . . . . . . . . . . . 10
54 3.2 Authentication . . . . . . . . . . . . . . . . . . . . . . 10
55 3.3 Authorization . . . . . . . . . . . . . . . . . . . . . . 10
56 3.4 Confidentiality . . . . . . . . . . . . . . . . . . . . . 10
57 3.5 Relaying Integrity . . . . . . . . . . . . . . . . . . . . 11
58 3.6 Traffic Analysis . . . . . . . . . . . . . . . . . . . . . 11
59 4. The APEX . . . . . . . . . . . . . . . . . . . . . . . . . 12
60 4.1 Use of XML and MIME . . . . . . . . . . . . . . . . . . . 12
61 4.2 Profile Identification and Initialization . . . . . . . . 14
62 4.3 Message Syntax . . . . . . . . . . . . . . . . . . . . . . 14
63 4.4 Message Semantics . . . . . . . . . . . . . . . . . . . . 15
64 4.4.1 The Attach Operation . . . . . . . . . . . . . . . . . . . 15
65 4.4.2 The Bind Operation . . . . . . . . . . . . . . . . . . . . 17
66 4.4.3 The Terminate Operation . . . . . . . . . . . . . . . . . 19
67 4.4.4 The Data Operation . . . . . . . . . . . . . . . . . . . . 20
68 4.4.4.1 Relay Processing of Data . . . . . . . . . . . . . . . . . 22
69 4.4.4.2 Application Processing of Data . . . . . . . . . . . . . . 23
70 4.5 APEX Access Policies . . . . . . . . . . . . . . . . . . . 24
71 4.5.1 Access Policies in the Endpoint-Relay Mode . . . . . . . . 25
72 4.5.2 Access Policies in the Relay-Relay Mode . . . . . . . . . 26
73 5. APEX Options . . . . . . . . . . . . . . . . . . . . . . . 27
74 5.1 The statusRequest Option . . . . . . . . . . . . . . . . . 29
75 6. APEX Services . . . . . . . . . . . . . . . . . . . . . . 34
76 6.1 Use of the APEX Core DTD . . . . . . . . . . . . . . . . . 35
77 6.1.1 Transaction-Identifiers . . . . . . . . . . . . . . . . . 35
78 6.1.2 The Reply Operation . . . . . . . . . . . . . . . . . . . 36
79 6.2 The Report Service . . . . . . . . . . . . . . . . . . . . 37
80 7. Registration Templates . . . . . . . . . . . . . . . . . . 38
81 7.1 APEX Option Registration Template . . . . . . . . . . . . 38
82 7.2 APEX Service Registration Template . . . . . . . . . . . . 38
83 8. Initial Registrations . . . . . . . . . . . . . . . . . . 39
84 8.1 Registration: The APEX Profile . . . . . . . . . . . . . . 39
85 8.2 Registration: The APEX Service-Selector for GSTN . . . . . 39
86 8.3 Registration: The statusRequest Option . . . . . . . . . . 40
87 8.4 Registration: The Report Service . . . . . . . . . . . . . 40
88 9. DTDs . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
89 9.1 The APEX Core DTD . . . . . . . . . . . . . . . . . . . . 41
90 9.2 The Report Service DTD . . . . . . . . . . . . . . . . . . 44
91 10. Reply Codes . . . . . . . . . . . . . . . . . . . . . . . 45
92 11. Security Considerations . . . . . . . . . . . . . . . . . 46
93 References . . . . . . . . . . . . . . . . . . . . . . . . 47
94 Authors' Addresses . . . . . . . . . . . . . . . . . . . . 47
95 A. Acknowledgements . . . . . . . . . . . . . . . . . . . . . 49
96 B. IANA Considerations . . . . . . . . . . . . . . . . . . . 50
97 C. Changes from IMXP . . . . . . . . . . . . . . . . . . . . 51
98 Full Copyright Statement . . . . . . . . . . . . . . . . . 52
100 1. Introduction
102 Network applications can be broadly distinguished by five operational
103 characteristics:
105 o server push or client pull;
107 o synchronous (interactive) or asynchronous (batch);
109 o time-assured or time-insensitive;
111 o best-effort or reliable; and,
113 o stateful or stateless.
115 For example:
117 o the world-wide web is a pull, synchronous, time-insensitive,
118 reliable, stateless service; whilst
120 o Internet mail is a push, asynchronous, time-insensitive, best-
121 effort (without DSN), stateless service.
123 Messaging applications vary considerably in their operational
124 requirements. For example, some messaging applications require
125 assurance of timeliness and reliability, whilst others do not.
127 These features come at a cost, in terms of both infrastructural and
128 configuration complexity. Accordingly, the underlying service must be
129 extensible to support different requirements in a consistent manner.
131 This memo defines a core messaging service that supports a range of
132 operational characteristics. The core service supports a variety of
133 tailored services for both user-based and programmatic exchanges.
135 1.1 Overview
137 APEX provides an extensible, asynchronous message relaying service
138 for application layer programs.
140 APEX, at its core, provides a best-effort datagram service. Each
141 datagram, simply termed "data", is originated and received by APEX
142 "endpoints" -- applications that dynamically attach to the APEX
143 "relaying mesh".
145 The data transmitted specifies:
147 o an originating endpoint;
149 o an opaque content (via a URI-reference);
151 o one or more recipient endpoints; and,
153 o zero or more options.
155 Options are used to alter the semantics of the the service, may occur
156 on a per-recipient or per-data basis, and may be processed by either
157 a single or multiple relays.
159 Additional APEX services are provided on top of the relaying mesh;
160 e.g., access control and presence information.
162 APEX is specified, in part, as a BEEP[1] "profile". Accordingly, many
163 aspects of APEX (e.g., authentication) are provided within the BEEP
164 core. Throughout this memo, the terms "peer", "initiator",
165 "listener", "client", and "server" are used in the context of BEEP.
166 In particular, Section 2.1 of the BEEP core memo discusses the roles
167 that a BEEP peer may perform.
169 When reading this memo, note that the terms "endpoint" and "relay"
170 are specific to APEX, they do not exist in the context of BEEP.
172 1.2 Architecture at a Glance
174 The APEX stack:
176 +-------------+
177 | APEX | an APEX process is either:
178 | process |
179 +-------------+ - an application attached as an APEX
180 | | endpoint; or,
181 | APEX |
182 | | - an APEX relay
183 +-------------+
184 | | APEX services are realized as applications
185 | BEEP | having a special relationship with the APEX
186 | | relays in their administrative domain
187 +-------------+
188 | TCP/IP |
189 +-------------+
190 | ... |
191 +-------------+
193 The APEX entities:
195 administrative domain #1 administrative domain #2
196 +----------------------------+ +----------------------------+
197 | +------+ | | +------+ |
198 | | | | | | | |
199 | | appl | | | | appl | |
200 | | | | | | | |
201 | +......+ +------+ | | +------+ +......+ |
202 | | | | | | | | | | | |
203 | |end- | |relay | | | |relay | |end- | |
204 | | point| | | | | | | | point| |
205 | +------+ +------+ | | +------+ +------+ |
206 | | | | | | | | | | | |
207 | | APEX | | APEX | | | | APEX | | APEX | |
208 | | | | | | | | | | | |
209 | +------+ +------+ | | +------+ +------+ |
210 | || || || | | || || || |
211 | ============= ================ ============= |
212 +----------------------------+ +----------------------------+
214 | <---- APEX relaying mesh ----> |
216 Note: relaying between administrative domains is configured
217 using SRV RRs. Accordingly, the actual number of
218 relays between two endpoints is not fixed.
220 2. Service Principles
222 2.1 Modes of Operation
224 APEX is used in two modes:
226 endpoint-relay: in which the endpoint is always the BEEP initiator of
227 the service, whilst relays are always the BEEP listeners. In this
228 context, applications attach as endpoints, and then the
229 transmission of data occurs.
231 relay-relay: in which relays typically, though not necessarily,
232 reside in different administrative domains. In this context,
233 applications bind as relays, and then the transmission of data
234 occurs.
236 In the endpoint-relay mode, an endpoint (BEEP initiator) may:
238 o attach as one or more endpoints;
240 o send data to other endpoints;
242 o receive data from other endpoints; and,
244 o terminate any of its attachments.
246 A relay (BEEP listener), in addition to servicing requests from a
247 BEEP initiator, may:
249 o terminate any of the endpoint's attachments;
251 o deliver data from other endpoints; and,
253 o indicate the delivery status of data sent earlier by the endpoint.
255 In the relay-relay mode, a relay (BEEP listener or initiator) may:
257 o bind as one or more administrative domains;
259 o send data;
261 o receive data; and,
263 o terminate any bindings.
265 2.2 Naming of Entities
267 Endpoints are named using the "addr-spec" syntax specified in Section
268 3.4.1 of [2], i.e., the familiar "local@domain" syntax.
270 Using the service-selector convention of RFC 2846[3], all endpoint
271 identities having a local-part starting with "apex=" are reserved for
272 use by APEX services registered with the IANA.
274 Relays, although not named, serve of behalf of administrative
275 domains, as identified by a FQDN, e.g., "example.com".
277 In APEX, "endpoints" and "relays" are the fundamental entities. APEX
278 is carried over BEEP, which has the "peer" as its fundamental entity.
279 The relationship between BEEP peer entities and APEX endpoint and
280 relay entities are defined by APEX's Access Policies (Section 4.5).
282 3. Service Provisioning
284 3.1 Connection Establishment
286 The SRV algorithm[4] is used to determine the IP/TCP addressing
287 information assigned to the relays for an administrative domain:
289 service: "apex-edge" (for the endpoint-relay mode), or "apex-mesh"
290 (for the relay-relay mode);
292 protocol: "tcp"; and,
294 domain: the administrative domain.
296 3.2 Authentication
298 Authentication is a matter of provisioning for each BEEP peer (c.f.,
299 Section 4.5).
301 An APEX relay might be provisioned to allow a BEEP peer identity to
302 coincide with a given endpoint identity. For example, a relay in the
303 "example.com" administrative domain may be configured to allow a BEEP
304 peer identified as "fred@example.com" to be authorized to attach as
305 the APEX endpoint "fred@example.com".
307 3.3 Authorization
309 Authorization is a matter of provisioning for each BEEP peer (c.f.,
310 Section 4.5).
312 Typically, a relay requires that its BEEP peer authenticate as a
313 prelude to authorization, but an endpoint usually does not require
314 the same of its BEEP peer.
316 3.4 Confidentiality
318 Confidentiality is a matter of provisioning for each BEEP peer.
320 Typically, any data considered sensitive by an originating endpoint
321 will have its content encrypted for the intended recipient
322 endpoint(s), rather than relying on hop-by-hop encryption. Similarly,
323 an originating endpoint will sign the content if end-to-end
324 authentication is desired.
326 3.5 Relaying Integrity
328 Data are relayed according to SRV entries in the DNS. Accordingly,
329 relaying integrity is a function of the DNS and the applications
330 making use of the DNS. Additional assurance is provided if the BEEP
331 initiator requires that the BEEP listener authenticate itself.
333 3.6 Traffic Analysis
335 Hop-by-hop protection of data transmitted through the relaying mesh
336 (endpoint identities and content) is afforded at the BEEP level
337 through the use of a transport security profile. Other traffic
338 characteristics, e.g., volume and timing of transmissions, is not
339 protected from third-party analysis.
341 4. The APEX
343 Section 8.1 contains the BEEP profile registration for APEX.
345 4.1 Use of XML and MIME
347 Each BEEP payload exchanged via APEX consists of an XML document and
348 possibly an arbitrary MIME content.
350 If only an XML document is sent in the BEEP payload, then the mapping
351 to a BEEP payload is straight-forward, e.g.,
353 C: MSG 1 2 . 111 39
354 C: Content-Type: application/beep+xml
355 C:
356 C:
357 C: END
359 Otherwise, if an arbitrary MIME content is present, it is indicated
360 by a URI-reference[5] in the XML control document. The URI-reference
361 may contain an absolute-URI (and possibly a fragment-identifier), or
362 it may be a relative-URI consisting only of a fragment-identifier.
363 Arbitrary MIME content is included in the BEEP payload by using a
364 "multipart/related"[6], identified using a "cid" URL[7], and the XML
365 control document occurs as the start of the "multipart/related",
366 e.g.,
368 C: MSG 1 1 . 42 1234
369 C: Content-Type: multipart/related; boundary="boundary";
370 C: start="<1@example.com>";
371 C: type="application/beep+xml"
372 C:
373 C: --boundary
374 C: Content-Type: application/beep+xml
375 C: Content-ID: <1@example.com>
376 C:
377 C:
378 C:
379 C:
380 C:
381 C: --boundary
382 C: Content-Type: image/gif
383 C: Content-Transfer-Encoding: binary
384 C: Content-ID: <2@example.com>
385 C:
386 C: ...
387 C: --boundary--
388 C: END
390 Because BEEP provides an 8bit-wide path, a "transformative" Content-
391 Transfer-Encoding (e.g., "base64" or "quoted-printable") should not
392 be used. Further, note that MIME[8] requires that the value of the
393 "Content-ID" header be globally unique.
395 If the arbitrary MIME content is itself an XML document, it may be
396 contained with the control document directly, and identified using a
397 URI-reference consisting of only a fragment-identifier, e.g.,
399 C: MSG 1 1 . 42 295
400 C: Content-Type: application/beep+xml
401 C:
402 C:
403 C:
404 C:
405 C:
406 C:
407 C:
408 C:
409 C:
410 C:
411 C:
412 C:
413 C: END
415 4.2 Profile Identification and Initialization
417 The APEX is identified as
419 http://xml.resource.org/profiles/APEX
421 in the BEEP "profile" element during channel creation.
423 No elements are required to be exchanged during channel creation;
424 however, in the endpoint-relay mode, the BEEP initiator will
425 typically include an "attach" element during channel creation, e.g.,
427
428
429 ]]>
431
432
434 Similarly, in the relay-relay mode, the BEEP initiator will typically
435 include an "bind" element during channel creation, e.g.,
437
438
439 ]]>
441
442
444 4.3 Message Syntax
446 Section 9.1 defines the BEEP payloads that are used in the APEX.
448 4.4 Message Semantics
450 4.4.1 The Attach Operation
452 When an application wants to attach to the relaying mesh as a given
453 endpoint, it sends an "attach" element to a relay, e.g.,
455 +-------+ +-------+
456 | | -- attach -----> | |
457 | appl. | | relay |
458 | | <--------- ok -- | |
459 +-------+ +-------+
461 C:
462 S:
464 or
466 +-------+ +-------+
467 | | -- attach -----> | |
468 | | | |
469 | | <--------- ok -- | |
470 | appl. | | relay |
471 | | -- attach -----> | |
472 | | | |
473 | | <--------- ok -- | |
474 +-------+ +-------+
476 C:
477 S:
478 C:
479 S:
481 or
483 +-------+ +-------+
484 | | -- attach -----> | |
485 | appl. | | relay |
486 | | <------ error -- | |
487 +-------+ +-------+
489 C:
490 S: access denied
492 The "attach" element has an "endpoint" attribute, a "transID"
493 attribute, and contains zero or more "option" elements:
495 o the "endpoint" attribute specifies the endpoint that the
496 application wants to attach as;
498 o the "transID" attribute specifies the transaction-identifier
499 associated with this operation; and,
501 o the "option" elements, if any, specify additional processing
502 options (Section 5).
504 When a relay receives an "attach" element, it performs these steps:
506 1. If the transaction-identifier refers to a previous, non-
507 terminated operation on this BEEP channel, an "error" element
508 having code 555 is returned.
510 2. If the relay is in a different administrative domain than this
511 endpoint, an "error" element having code 553 is returned.
513 3. If the application is not authorized to attach as this endpoint
514 (c.f., Section 4.5.1), an "error" element having code 537 is
515 returned.
517 4. If any options are present, they are processed.
519 5. If another application has already attached as this endpoint, an
520 "error" element having code 554 is returned.
522 6. Otherwise, the application is bound as this endpoint, and an "ok"
523 element is returned.
525 4.4.2 The Bind Operation
527 When an application wants to identify itself as a relay, it sends a
528 "bind" element to another relay, e.g.,
530 +-------+ +-------+
531 | | -- bind -------> | |
532 | relay | | relay |
533 | #1 | <--------- ok -- | #2 |
534 +-------+ +-------+
536 C:
537 S:
539 or
541 +-------+ +-------+
542 | | -- bind -------> | |
543 | | | |
544 | | <--------- ok -- | |
545 | relay | | relay |
546 | #1 | -- bind -------> | #2 |
547 | | | |
548 | | <--------- ok -- | |
549 +-------+ +-------+
551 C:
552 S:
553 C:
554 S:
556 or
558 +-------+ +-------+
559 | | -- bind -------> | |
560 | relay | | relay |
561 | #1 | <------ error -- | #2 |
562 +-------+ +-------+
564 C:
565 S: access denied
567 The "bind" element has a "relay" attribute, a "transID" attribute,
568 and contains zero or more "option" elements:
570 o the "relay" attribute specifies the administrative domain on whose
571 behalf the application wants to serve;
573 o the "transID" attribute specifies the transaction-identifier
574 associated with this operation; and,
576 o the "option" elements, if any, specify additional processing
577 options (Section 5).
579 When a relay receives an "bind" element, it performs these steps:
581 1. If the transaction-identifier refers to a previous, non-
582 terminated operation on this BEEP channel, an "error" element
583 having code 555 is returned.
585 2. The relay performs the SRV algorithm[4] for the desired
586 administrative domain (i.e., using a service of "apex-mesh" and a
587 protocol of "tcp"). For each domain name returned by the
588 algorithm, the corresponding IP address(es) are retrieved using
589 the DNS. The relay compares the application's IP address and TCP
590 port number to the corresponding IP addresses and TCP port
591 numbers found using the SRV algorithm. If none match, an "error"
592 element having code 537 is returned.
594 3. If the application is not authorized to bind on behalf of this
595 administrative domain (c.f., Section 4.5.2), an "error" element
596 having code 537 is returned.
598 4. If any options are present, they are processed.
600 5. Otherwise, the application is accepted as serving this
601 administrative domain, and an "ok" element is returned.
603 4.4.3 The Terminate Operation
605 When an application or relay wants to release an attachment or
606 binding, it sends a "terminate" element, e.g.,
608 +-------+ +-------+
609 | | -- terminate --> | |
610 | appl. | | relay |
611 | | <--------- ok -- | |
612 +-------+ +-------+
614 C:
615 S:
617 or
619 +-------+ +-------+
620 | | -- terminate --> | |
621 | appl. | | relay |
622 | | <------ error -- | |
623 +-------+ +-------+
625 C:
626 S: unknown transaction-identifier
628 or
630 +-------+ +-------+
631 | | <-- terminate -- | |
632 | appl. | | relay |
633 | | -- ok ---------> | |
634 +-------+ +-------+
636 C:
637 S:
639 The "terminate" element has a "transID" attribute and no content.
641 When an application or relay receives a "terminate" element, it
642 performs these steps:
644 1. If the transaction-identifier does not refer to a previous
645 unterminated operation on this BEEP channel, an "error" element
646 having code 550 is returned.
648 2. Otherwise, the application is no longer bound as an endpoint or a
649 relay, and an "ok" element is returned.
651 4.4.4 The Data Operation
653 When an application or relay wants to transmit data over the relaying
654 mesh, it sends a "data" element, e.g.,
656 +-------+ +-------+
657 | | -- data -------> | |
658 | appl. | | relay |
659 | #1 | <--------- ok -- | |
660 +-------+ +-------+
662 C:
663
664
665
666 S:
668 or
670 +-------+ +-------+
671 | | -- data -------> | |
672 | appl. | | relay |
673 | #1 | <------ error -- | |
674 +-------+ +-------+
676 C:
677
678
679
680 S: access denied
682 or
684 +-------+ +-------+
685 | | -- data -------> | |
686 | relay | | appl. |
687 | | <--------- ok -- | #2 |
688 +-------+ +-------+
690 C:
691
692
693
694 S:
696 The "data" element has a "content" attribute, and contains an
697 "originator" element, one or more "recipient" elements, zero or more
698 "option" elements, and, optionally, a "data-content" element:
700 o the "content" attribute is a URI-reference that specifies the
701 contents of the data (c.f., Section 4.1);
703 o the "originator" element refers to the endpoint sending the data;
705 o each "recipient" element refers to an endpoint destination for the
706 data;
708 o the "option" elements, if any, specify additional processing
709 options (Section 5), termed per-data options; and,
711 o the "data-content" element, if present, specifies a nested XML
712 entity using a URI fragment-identifier as the value of the
713 "content" attribute.
715 The "originator" element has an "identity" attribute, and contains
716 zero or more option elements:
718 o the "identity" attribute specifies the sending endpoint; and
720 o the "option" elements, if any, specify additional processing
721 options for the originator, termed per-originator options.
723 Each "recipient" element has an "identity" attribute, and contains
724 zero or more option elements:
726 o the "identity" attribute specifies the destination endpoint; and
728 o the "option" elements, if any, specify additional processing
729 options for this recipient, termed per-recipient options.
731 4.4.4.1 Relay Processing of Data
733 When a relay receives a "data" element, it performs these steps:
735 1. If the BEEP client is not authorized to originate or relay data
736 on behalf of the "originator" endpoint (c.f., Section 4.5), an
737 "error" element having code 537 is returned.
739 2. If any per-data options are present, they are processed.
741 3. An "ok" element is returned.
743 4. If any per-originator options are present, they are processed.
745 5. For each recipient:
747 1. If any per-recipient options are present, they are processed.
749 2. If the recipient endpoint is not in the administrative domain
750 associated with the relay, then an APEX session is
751 established to a relay that accepts data for the recipient's
752 administrative domain, and a new "data" element, containing
753 that "recipient" element and all applicable options, is sent
754 to that relay.
756 If no errors (e.g., an APEX session can not be established)
757 occur during processing, and if the recipient's relay returns
758 an "ok" element, then the recipient is considered to be
759 successfully processed.
761 3. Otherwise, if the recipient endpoint is in the same
762 administrative domain as the relay, the APEX access service
763 must check that the originator endpoint is allowed to
764 communicate with the recipient endpoint (the recipient's
765 access entry[9] must contain a "core:data" token for the
766 originator), and the recipient endpoint must be currently
767 attached.
769 If so, a new "data" element, containing only that "recipient"
770 element, is sent to the corresponding application. If the
771 recipient's endpoint returns an "ok" element, then the
772 recipient is considered to be successfully processed.
774 Note that an implementation may choose to optimize its behavior by
775 grouping multiple recipients in a single "data" element that is
776 subsequently transmitted. It may do so providing that the
777 optimization retains these semantics and any other semantics related
778 to per-data and per-recipient options.
780 Finally, note that a relay receiving a "data" element from an
781 application may be configured to add domain-specific options.
783 4.4.4.2 Application Processing of Data
785 When an application receives a "data" element, it performs these
786 steps:
788 1. If any per-data or per-originator options are present, they are
789 not processed (but may be noted).
791 2. For each recipient:
793 1. If any per-recipient options are present, they are not
794 processed (but may be noted).
796 2. If the application is not attached as the recipient endpoint,
797 then an error in processing has occurred.
799 3. Otherwise, the "data" element is further processed in an
800 application-specific manner, and the recipient is considered
801 to be successfully processed.
803 3. If no recipients could be successfully processed, an "error"
804 element is returned; otherwise, an "ok" element is returned.
806 4.5 APEX Access Policies
808 Access to APEX is provided by the juxtaposition of:
810 o authenticating as a BEEP peer;
812 o attaching as an APEX endpoint or binding as an APEX relay; and,
814 o being listed as an actor by the APEX access service (c.f., [9]).
816 Each of these activities occurs according to the policies of the
817 relevant administrative domain:
819 o each administrative domain is responsible for keeping its own
820 house in order through "local provisioning"; and,
822 o each administrative domain decides the level of trust to associate
823 with other administrative domains.
825 4.5.1 Access Policies in the Endpoint-Relay Mode
827 o When an application wants to attach to the relaying mesh, local
828 provisioning maps BEEP peer identities to allowed APEX endpoints
829 (c.f., Step 3 of Section 4.4.1).
831 Typically, the identity function is used, e.g., if an application
832 authenticates itself as the BEEP peer named as "fred@example.com",
833 it is allowed to attach as the APEX endpoint named as
834 "fred@example.com".
836 Using the subaddress-specification convention of RFC 2846[3], an
837 application authorized to attach as a given APEX endpoint is also
838 authorized to attach as any sub-address of that APEX endpoint,
839 e.g., an application authorized to attach as the APEX endpoint
840 "fred@example.com" is also authorized to attach as the APEX
841 endpoint "fred/appl=wb@example.com".
843 o When an application wants to send data, local provisioning maps
844 attached endpoints to allowed originators (c.f., Step 1 of Section
845 4.4.4.1).
847 Typically, the identity function is used, e.g., if an application
848 attaches as the APEX endpoint named as "fred@example.com", it is
849 allowed to send data originating from the same APEX endpoint.
850 However, other policies are permissible, for example, the
851 administrative domain may allow the application attached as the
852 APEX endpoint named as "wilma@example.com" to send data
853 originating as either "wilma@example.com" or "fred@example.com".
855 o Finally, when a relay is delivering to an endpoint within its own
856 administrative domain, it consults the recipient's access entry
857 looking for an entry having the originator as an actor (c.f., Step
858 5.3 of Section 4.4.4.1).
860 4.5.2 Access Policies in the Relay-Relay Mode
862 o When an application wants to bind as a relay on behalf of an
863 administrative domain, in addition to Step 2 of Section 4.4.2,
864 local provisioning may map BEEP peer identities to allowed APEX
865 relays (c.f., Step 3).
867 If so, then typically the identity function is used. e.g., if an
868 application authenticates itself as the BEEP peer named as
869 "example.com", it is allowed to bind as a relay on behalf of the
870 administrative domain "example.com".
872 o When a relay is sending data, no access policies, per se, are
873 applied.
875 o When a relay is receiving data, local provisioning maps BEEP peer
876 identities to allowed originators (c.f., Step 1 of Section
877 4.4.4.1).
879 Typically, the identity function is used, e.g., if a relay
880 authenticates itself as being from the same administrative domain
881 as the originator of the data, then the data is accepted.
883 In addition, some relays may also be configured as "trusted"
884 intermediaries, so that if a BEEP peer authenticates itself as
885 being from such a relay, then the data is accepted.
887 5. APEX Options
889 APEX, at its core, provides a best-effort datagram service. Options
890 are used to alter the semantics of the core service.
892 The semantics of the APEX "option" element are context-specific.
893 Accordingly, the specification of an APEX option must define:
895 o the identity of the option;
897 o the context in which the option may appear;
899 o what content, if any, is contained within the option; and,
901 o the processing rules for the option.
903 An option registration template (Section 7.1) organizes this
904 information.
906 An "option" element is contained within either a "data",
907 "originator", or "recipient" element, all of which are termed the
908 "containing" element. The "option" element has several attributes and
909 contains arbitrary content:
911 o the "internal" and the "external" attributes, exactly one of which
912 is present, uniquely identify the option;
914 o the "targetHop" attribute specifies which relays should process
915 the option;
917 o the "seeNoEvil" attribute specifies whether the option, if
918 unrecognized, may be safely ignored;
920 o the "transID" attribute specifies a transaction-identifier for the
921 option; and,
923 o the "localize" attribute, if present, specifies one or more
924 language tokens, each identifying a desirable language tag to be
925 used if textual diagnostics are returned to the originator.
927 The value of the "internal" attribute is the IANA-registered name for
928 the option. If the "internal" attribute is not present, then the
929 value of the "external" attribute is a URI or URI with a fragment-
930 identifier. Note that a relative-URI value is not allowed.
932 The "targetHop" attribute specifies which relay(s) should process the
933 option:
935 this: the option applies to this relay, and must be removed prior
936 to transmitting the containing element.
938 final: the option applies to this relay, only if the the relay is
939 able to transmit the containing element directly to the recipient.
941 all: the option applies to this relay and is retained for the
942 next.
944 Note that a final relay does not remove any options as it transmits
945 the containing element directly to the recipient.
947 The "seeNoEvil" attribute specifies whether the relay may ignore the
948 option if it is unrecognized, and is consulted only if the
949 "targetHop" attribute indicates that the option applies to that
950 relay. If the option applies, and if the value of the "seeNoEvil"
951 attribute is "false", and if the relay does not "understand" the
952 option, then this is considered a processing error.
954 5.1 The statusRequest Option
956 Section 8.3 contains the APEX option registration for the
957 "statusRequest" option.
959 If this option is present, then each applicable relay sends a
960 "statusResponse" message to the originator. This is done by issuing a
961 data operation whose originator is the report service associated with
962 the issuing relay, whose recipient is the endpoint address of the
963 "statusRequest" originator, and whose content is a "statusResponse"
964 element.
966 A "statusRequest" option MUST NOT be present in any data operation
967 containing a "statusResponse" element.
969 Consider these examples:
971 +-------+ +-------+
972 | | -- data -------> | |
973 | appl. | | relay |
974 | #1 | <--------- ok -- | |
975 +-------+ +-------+
977 C:
978
979
980
982
983 S:
985 +-------+ +-------+
986 | | -- data -------> | |
987 | relay | | appl. |
988 | | <--------- ok -- | #2 |
989 +-------+ +-------+
991 C:
992
993
994
996
997 S:
999 +-------+ +-------+
1000 | | <------- data -- | |
1001 | appl. | | relay |
1002 | #1 | -- ok ---------> | |
1003 +-------+ +-------+
1005 C:
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016 S:
1018 or
1020 +-------+ +-------+
1021 | | -- data -------> | |
1022 | appl. | | relay |
1023 | #1 | <--------- ok -- | |
1024 +-------+ +-------+
1026 C:
1027
1028
1029
1031
1032 S:
1034 +-------+ +-------+
1035 | | <------- data -- | |
1036 | appl. | | relay |
1037 | #1 | -- ok ---------> | |
1038 +-------+ +-------+
1040 C:
1041
1042
1043
1044
1045
1046 unknown endpoint
1047 identity
1048
1049
1050
1051
1052 S:
1054 or
1056 +-------+ +-------+
1057 | | -- data -------> | |
1058 | appl. | | relay |
1059 | #1 | <--------- ok -- | #1 |
1060 +-------+ +-------+
1062 C:
1063
1064
1065
1067
1068 S:
1069 +-------+ +-------+
1070 | | -- data -------> | |
1071 | relay | | relay |
1072 | #1 | <--------- ok -- | #2 |
1073 +-------+ +-------+
1075 C:
1076
1077
1078
1080
1081 S:
1083 +-------+ +-------+
1084 | | -- data -------> | |
1085 | relay | | appl. |
1086 | #2 | <--------- ok -- | #2 |
1087 +-------+ +-------+
1089 C:
1090
1091
1092
1094
1095 S:
1096 +-------+ +-------+
1097 | | <------- data -- | |
1098 | relay | | relay |
1099 | #1 | -- ok ---------> | #2 |
1100 +-------+ +-------+
1102 C:
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113 S:
1115 +-------+ +-------+
1116 | | <------- data -- | |
1117 | appl. | | relay |
1118 | #1 | -- ok ---------> | #1 |
1119 +-------+ +-------+
1121 C:
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132 S:
1134 Note that a trace of a data's passage through the relaying mesh can
1135 be achieved by setting the "targetHop" attribute to "all".
1137 6. APEX Services
1139 APEX, at its core, provides a best-effort datagram service. Within an
1140 administrative domain, all relays must be able to handle messages for
1141 any endpoint within that domain. APEX services are logically defined
1142 as endpoints but given their ubiquitous semantics they do not
1143 necessarily need to be associated with a single physical endpoint. As
1144 such, they may be provisioned co-resident with each relay within an
1145 administrative domain, even though they are logically provided on top
1146 of the relaying mesh, i.e.,
1148 +----------+ +----------+ +----------+ +---------+
1149 | APEX | | APEX | | APEX | | |
1150 | access | | presence | | report | | ... |
1151 | service | | service | | service | | |
1152 +----------+ +----------+ +----------+ +---------+
1153 | | | |
1154 | | | |
1155 +----------------------------------------------------------------+
1156 | |
1157 | APEX core |
1158 | |
1159 +----------------------------------------------------------------+
1161 That is, applications communicate with an APEX service by exchanging
1162 data with a "well-known endpoint" (WKE).
1164 For example, APEX applications communicate with the report service by
1165 exchanging data with the well-known endpoint "apex=report" in the
1166 corresponding administrative domain, e.g., "apex=report@example.com"
1167 is the endpoint associated with the report service in the
1168 "example.com" administrative domain.
1170 The specification of an APEX service must define:
1172 o the WKE of the service;
1174 o the syntax and sequence of messages exchanged with the service;
1176 o what access control tokens are consulted by the service.
1178 A service registration template (Section 7.2) organizes this
1179 information.
1181 Finally, note that within a single administrative domain, the
1182 relaying mesh makes use of the APEX access service in order to
1183 determine if an originator is allowed to transmit data to a recipient
1184 (c.f., Step 5.3 of Section 4.4.4.1)
1186 6.1 Use of the APEX Core DTD
1188 The specification of an APEX service may use definitions found in the
1189 APEX core DTD (Section 9.1). For example, the reply operation
1190 (Section 6.1.2) is defined to provide a common format for responses.
1192 6.1.1 Transaction-Identifiers
1194 In using APEX's transaction-identifiers, note the following:
1196 o In the endpoint-relay and relay-relay modes, transaction-
1197 identifiers are meaningful only during the lifetime of a BEEP
1198 channel.
1200 For example, when an application issues the attach operation, the
1201 associated transaction-identifier has meaning only within the
1202 context of the BEEP channel used for the attach operation. When
1203 the BEEP connection is released, the channel no longer exists and
1204 the application is no longer attached to the relaying mesh.
1206 o In contrast, when an application communicates with an APEX
1207 service, transaction-identifiers are often embedded in the data
1208 that is sent. This means that transaction-identifiers are
1209 potentially long-lived.
1211 For example, an application may attach as an endpoint, send data
1212 (containing an embedded transaction-identifier) to a service, and,
1213 some time later, detach from the relaying mesh. Later on, a second
1214 application may attach as the same endpoint, and send data of its
1215 own (also containing embedded transaction-identifiers).
1216 Subsequently, the second application may receive data from the
1217 service responding to the first application's request and
1218 containing the transaction-identifier used by the first
1219 application.
1221 To minimize the likelihood of ambiguities with long-lived
1222 transaction-identifiers, the values of transaction-identifiers
1223 generated by applications should appear to be unpredictable.
1225 6.1.2 The Reply Operation
1227 Many APEX services make use of a reply operation. Accordingly,
1228 Section 9.1 contains a definition of a "reply" element that can be
1229 used for this purpose.
1231 The "reply" element has a "code" attribute, a "transID" attribute, an
1232 optional "xml:lang" attribute, and may contain arbitrary textual
1233 content:
1235 o the "code" element specifies a three-digit reply code (c.f.,
1236 Section 10);
1238 o the "transID" attribute specifies the transaction-identifier
1239 corresponding to this reply;
1241 o the "xml:lang" attribute, if present, specifies the language that
1242 the element's content is written in; and,
1244 o the textual content is a diagnostic (possibly multiline) which is
1245 meaningful to implementers, perhaps administrators, and possibly
1246 even users.
1248 6.2 The Report Service
1250 Section 8.4 contains the APEX service registration for the report
1251 service:
1253 o Within an administrative domain, the service is addressed using
1254 the well-known endpoint of "apex=report".
1256 o Section 9.2 defines the syntax of the operations exchanged with
1257 the service.
1259 o A consumer of the service does not initiate communications with
1260 the service.
1262 o The service initiates communications by sending data containing
1263 the "statusResponse" operation.
1265 If a relay processes a "statusRequest" option (Section 5.1), then it
1266 sends data to the originator containing a "statusResponse" element
1267 (Section 9.2).
1269 The "statusResponse" element has a "transID" attribute and contains
1270 one or more "destination" elements:
1272 o the "transID" attribute specifies the value contained in the
1273 "statusRequest" option; and,
1275 o each "destination" element has an "identity" attribute and
1276 contains a "reply" element:
1278 * the "identity" attribute specifies the recipient endpoint that
1279 is being reported on; and,
1281 * the "reply" element (Section 6.1.2) specifies the delivery
1282 status of that recipient.
1284 7. Registration Templates
1286 7.1 APEX Option Registration Template
1288 When an APEX option is registered, the following information is
1289 supplied:
1291 Option Identification: specify the NMTOKEN or the URI that
1292 authoritatively identifies this option.
1294 Present in: specify the APEX elements in which the option may appear.
1296 Contains: specify the XML content that is contained within the
1297 "option" element.
1299 Processing Rules: specify the processing rules associated with the
1300 option.
1302 Contact Information: specify the postal and electronic contact
1303 information for the author of the profile.
1305 7.2 APEX Service Registration Template
1307 When an APEX service is registered, the following information is
1308 supplied:
1310 Well-Known Endpoint: specify the local-part of an endpoint identity,
1311 starting with "apex=".
1313 Syntax of Messages Exchanged: specify the elements exchanged with the
1314 service.
1316 Sequence of Messages Exchanged: specify the order in which data is
1317 exchanged with the service.
1319 Access Control Tokens: specify the token(s) used to control access to
1320 the service (c.f., [9]).
1322 Contact Information: specify the postal and electronic contact
1323 information for the author of the profile.
1325 8. Initial Registrations
1327 8.1 Registration: The APEX Profile
1329 Profile Identification: http://xml.resource.org/profiles/APEX
1331 Messages exchanged during Channel Creation: "attach", "bind"
1333 Messages starting one-to-one exchanges: "attach", "bind",
1334 "terminate", or "data"
1336 Messages in positive replies: "ok"
1338 Messages in negative replies: "error"
1340 Messages in one-to-many exchanges: none
1342 Message Syntax: c.f., Section 9.1
1344 Message Semantics: c.f., Section 4.4
1346 Contact Information: c.f., the "Authors' Addresses" section of this
1347 memo
1349 8.2 Registration: The APEX Service-Selector for GSTN
1351 Service-Selector Name: APEX
1353 Description of Use: Specifies endpoints for registered APEX services
1354 on the host indicated by the address' domain name, c.f., Section 6
1356 Security Considerations: The definition of a service-related endpoint
1357 does not introduce security concerns, per se; however, because the
1358 defined endpoints are service control points, the nature of
1359 messages sent to them may introduce security concerns
1361 Contact Information: c.f., the "Authors' Addresses" section of this
1362 memo
1364 8.3 Registration: The statusRequest Option
1366 Option Identification: statusRequest
1368 Present in: APEX's "data" and "recipient" elements
1370 Contains: nothing
1372 Processing Rules: c.f., Section 5.1
1374 Contact Information: c.f., the "Authors' Addresses" section of this
1375 memo
1377 8.4 Registration: The Report Service
1379 Well-Known Endpoint: apex=report
1381 Syntax of Messages Exchanged: c.f., Section 9.2
1383 Sequence of Messages Exchanged: c.f., Section 6.2
1385 Access Control Tokens: none
1387 Contact Information: c.f., the "Authors' Addresses" section of this
1388 memo
1390 9. DTDs
1392 9.1 The APEX Core DTD
1394
1404
1406 %BEEP;
1408
1427
1428
1429
1430
1431
1445
1446
1450
1451
1455
1456
1459
1460
1463
1464
1467
1468
1471
1473
1474
1476
1477
1481
1482
1487
1490
1491
1499 9.2 The Report Service DTD
1501
1511
1513 %APEXCORE;
1515
1529
1531
1534
1535
1538 10. Reply Codes
1540 code meaning
1541 ==== =======
1542 250 transaction successful
1544 421 service not available
1546 450 requested action not taken
1548 451 requested action aborted
1550 454 temporary authentication failure
1552 500 general syntax error (e.g., poorly-formed XML)
1554 501 syntax error in parameters (e.g., non-valid XML)
1556 504 parameter not implemented
1558 530 authentication required
1560 534 authentication mechanism insufficient
1562 535 authentication failure
1564 537 action not authorized for user
1566 538 authentication mechanism requires encryption
1568 550 requested action not taken
1570 553 parameter invalid
1572 554 transaction failed (e.g., policy violation)
1574 555 transaction already in progress
1576 11. Security Considerations
1578 Consult Section 3 and Section 4.5 for a discussion of security
1579 issues, e.g., relaying integrity. In addition, since APEX is a
1580 profile of the BEEP, consult [1]'s Section 9 for a discussion of
1581 BEEP-specific security issues.
1583 In addition, the statusRequest option (Section 5.1) may be used to
1584 expose private network topology. Accordingly, administrators may wish
1585 to choose to disable this option except at the ingress/egress points
1586 for their domain.
1588 References
1590 [1] Rose, M.T., "The Blocks Extensible Exchange Protocol Core",
1591 draft-ietf-beep-framework-11 (work in progress), January 2001.
1593 [2] Resnick, P., "Internet Message Format", draft-drums-msg-fmt-09
1594 (work in progress), September 2000.
1596 [3] Allocchio, C., "GSTN Address Element Extensions in E-mail
1597 Services", RFC 2846, June 2000.
1599 [4] Gulbrandsen, A., Vixie, P. and L. Esibov, "A DNS RR for
1600 specifying the location of services (DNS SRV)", RFC 2782,
1601 February 2000.
1603 [5] Berners-Lee, T., Fielding, R.T. and L. Masinter, "Uniform
1604 Resource Identifiers (URI): Generic Syntax", RFC 2396, August
1605 1998.
1607 [6] Levinson, E., "The MIME Multipart/Related Content-type", RFC
1608 2387, August 1998.
1610 [7] Levinson, E., "Content-ID and Message-ID Uniform Resource
1611 Locators", RFC 2392, August 1998.
1613 [8] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
1614 Extensions (MIME) Part One: Format of Internet Message Bodies",
1615 RFC 2045, November 1996.
1617 [9] Rose, M.T., Klyne, G. and D.H. Crocker, "The APEX Access
1618 Service", draft-mrose-apex-access-02 (work in progress),
1619 December 2000.
1621 [10] Rose, M.T., Klyne, G. and D.H. Crocker, "The APEX Presence
1622 Service", draft-mrose-apex-presence-03 (work in progress),
1623 February 2001.
1625 Authors' Addresses
1627 Marshall T. Rose
1628 Invisible Worlds, Inc.
1629 1179 North McDowell Boulevard
1630 Petaluma, CA 94954-6559
1631 US
1633 Phone: +1 707 789 3700
1634 EMail: mrose@invisible.net
1635 URI: http://invisible.net/
1637 Graham Klyne
1638 Content Technologies Limited
1639 1220 Parkview
1640 Arlington Business Park
1641 Theale, Reading RG7 4SA
1642 UK
1644 Phone: +44 118 930 1300
1645 EMail: gk@acm.org
1647 David H. Crocker
1648 Brandenburg Consulting
1649 675 Spruce Drive
1650 Sunnyvale, CA 94086
1651 US
1653 Phone: +1 408 246 8253
1654 EMail: dcrocker@brandenburg.com
1655 URI: http://www.brandenburg.com/
1657 Appendix A. Acknowledgements
1659 The authors gratefully acknowledge the contributions of: Harald
1660 Alvestrand, Eric Dixon, Darren New, Chris Newman, and Scott Pead.
1662 Appendix B. IANA Considerations
1664 The IANA registers "APEX" as a standards-track BEEP profile, as
1665 specified in Section 8.1.
1667 The IANA registers "apex" as a GSTN service-selector, as specified in
1668 Section 8.2.
1670 The IANA maintains a list of:
1672 o APEX options, c.f., Section 7.1; and,
1674 o APEX services, c.f., Section 7.2.
1676 For each list, the IESG is responsible for assigning a designated
1677 expert to review the specification prior to the IANA making the
1678 assignment. As a courtesy to developers of non-standards track APEX
1679 options and services, the mailing list apexwg@invisible.net may be
1680 used to solicit commentary.
1682 The IANA makes the registrations specified in Section 8.3 and Section
1683 8.4.
1685 Appendix C. Changes from IMXP
1687 o s/IMXP/APEX/g
1689 o Clarify the notion of co-residence for APEX services.
1691 o Change data's originator from an attribute to an element.
1693 o Change addr-spec reference from RFC 822 to [2].
1695 o Move the section on "IANA Considerations" to an appendix.
1697 Full Copyright Statement
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