RFC 3342 |
TOC |
|
This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the “Internet Official Protocol Standards” (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited.
Copyright © The Internet Society (2002). All Rights Reserved.
Application Exchange (APEX), at its core, provides a best-effort application-layer datagram service. Options are used to alter the semantics of the core service. This memo defines various options to change the default behavior of APEX's "relaying mesh".
RFC 3342 |
TOC |
1.
The attachOverride Option
2.
The dataTiming Option
2.1.
Upper-Bounds on Delivery
2.1.1.
Final Hop Report
2.1.2.
Timing Error Report
2.2.
Reporting on Delayed Delivery
2.2.1.
Transient Timing Report
3.
The hold4Endpoint Option
4.
The dataHopping Option
5.
Initial Registrations
5.1.
Registration: The attachOverride Option
5.2.
Registration: The dataTiming Option
5.3.
Registration: The hold4Endpoint Option
5.4.
Registration: The dataHopping Option
6.
The APEX Party Pack DTD
7.
Security Considerations
8.
References
Appendix A.
Acknowledgements
Appendix B.
IANA Considerations
§
Authors' Addresses
§
Intellectual Property and Copyright Statements
TOC |
Section 5.1 (Registration: The attachOverride Option) contains the APEX option registration for the "attachOverride" option.
The default behavior of the APEX relaying mesh, in the absence of processing options, is to allow at most one application to attach as a particular endpoint, on a "first come, first served" basis. The "attachOverride" option provides gives preference to the current application trying to attach.
If this option is present in the "attach" operation (c.f., Section 4.4.1 of [RFC3340] (Rose, M., Klyne, G., and D. Crocker, “The Application Exchange Core,” July 2002.)) and if any application is already attached as the specified endpoint, that endpoint has its attachment terminated (c.f., Section 4.4.3 of [RFC3340] (Rose, M., Klyne, G., and D. Crocker, “The Application Exchange Core,” July 2002.)) concurrently with processing of that "attach" operation. The "code" attribute of the resulting "terminate" operation is set to 556.
Note that any data being expected by the previously-attached application may instead be delivered to the last application to successfully attach. Accordingly, applications should take care to properly deal with incoming data having unrecognized transaction-identifiers (c.f., Section 6.1.1 of [RFC3340] (Rose, M., Klyne, G., and D. Crocker, “The Application Exchange Core,” July 2002.)).
This option provides for a new attachment to automatically terminate any existing attachment for the same endpoint. For example, this might be helpful when a new attachment is required from a different device while a previously-used device is still attached e.g.,
+-------+ +-------+ | | -- attach -----> | | | appl. | | relay | | #1 | <--------- ok -- | | +-------+ +-------+ C: <attach endpoint='fred@example.com' transID='1' /> S: <ok /> ... some time later appl #2 starts on a different computer ... +-------+ +-------+ | | <----- attach -- | | +-------+ | | | appl. | | | <-- terminate -- | relay | -- ok ---------> | #2 | | appl. | | | +-------+ | #1 | -- ok ---------> | | +-------+ +-------+ C: <attach endpoint='fred@example.com' transID='2'> <option internal='attachOverride' transID='3' /> </attach> S: <ok /> C: <terminate transID='1' code='556'>overriden</terminate> S: <ok />
TOC |
Section 5.2 (Registration: The dataTiming Option) contains the APEX option registration for the "dataTiming" option. This option contains a "dataTiming" element (c.f., Section 6 (The APEX Party Pack DTD)).
The default behavior of the APEX relaying mesh is "immediate, best effort", and expects that all relays and endpoints are able to process and transfer data without delay — in the absence of processing options, if a relay is unavailable, then data is silently dropped. The "dataTiming" option provides for controlled queuing delays in processing, whilst providing reasonable deterministic behavior for the originator.
There are two types of delays addressed by the "dataTiming" option:
Accordingly, the "dataTiming" option allows for:
This option does not provide any functionality with respect to the priority of the data. Nor does this option have any effect on other parts of the relaying process.
Further, note that because this option is processed on a per-hop basis, the originator must set the "targetHop" attribute to the value "all" and the "mustUnderstand" attribute to the value "true".
TOC |
The "noLaterThan" attribute of the "dataTiming" option provides for control over delays that may occur in transit through the relaying mesh or to the recipient endpoint.
If this option is present in the "data" operation (c.f., Section 4.4.4 of [RFC3340] (Rose, M., Klyne, G., and D. Crocker, “The Application Exchange Core,” July 2002.)) and the value of the "noLaterThan" attribute is non-zero, then:
Note that in some cases, a relay may be able to predict this outcome without actually connecting to the next relay; if so, a timing error report may be sent without connecting to the next relay.
TOC |
If the APEX report service (c.f., Section 6.2 of [RFC3340] (Rose, M., Klyne, G., and D. Crocker, “The Application Exchange Core,” July 2002.)) is invoked to send a final hop report, it issues a data operation with:
For example:
+-------+ +-------+ | | -- data -------> | | | relay | | appl. | | | <--------- ok -- | #2 | +-------+ +-------+ C: <data content='cid:1@example.com'> <originator identity='fred@example.com' /> <recipient identity='barney@example.com' /> <option internal='dataTiming' targetHop='all' mustUnderstand='true' transID='86'> <dataTiming noLaterThan='10000' returnTrip='20000' /> </option> </data> S: <ok /> +-------+ +-------+ | | <------- data -- | | | appl. | | relay | | #1 | -- ok ---------> | | +-------+ +-------+ C: <data content='#Content'> <originator identity='apex=report@example.com' /> <recipient identity='fred@example.com' /> <option internal='dataTiming' targetHop='all' mustUnderstand='true' transID='99'> <dataTiming noLaterThan='20000' /> </option> <data-content Name='Content'> <statusResponse transID='86'> <destination identity='barney@example.com'> <reply code='250' /> </destination> </statusResponse> </data-content> </data> S: <ok />
TOC |
If the APEX report service (c.f., Section 6.2 of [RFC3340] (Rose, M., Klyne, G., and D. Crocker, “The Application Exchange Core,” July 2002.)) is invoked to send a timing error report, it issues a data operation with:
For example:
+-------+ +-------+ | | -- data -------> | | | appl. | | relay | | | <--------- ok -- | | +-------+ +-------+ C: <data content='cid:1@example.com'> <originator identity='fred@example.com' /> <recipient identity='barney@example.com' /> <option internal='dataTiming' targetHop='all' mustUnderstand='true' transID='86'> <dataTiming noLaterThan='6000' reportErrors='true' /> </option> </data> S: <ok /> ... some time later ... +-------+ +-------+ | | <------- data -- | | | appl. | | relay | | | -- ok ---------> | | +-------+ +-------+ C: <data content='#Content'> <originator identity='apex=report@example.com' /> <recipient identity='fred@example.com' /> <data-content Name='Content'> <statusResponse transID='86'> <destination identity='barney@example.com'> <reply code='550' /> </destination> </statusResponse> </data-content> </data> S: <ok />
TOC |
The "reportAfter" attribute of the "dataTiming" option provides for the originator to be notified if delivery is delayed beyond a specified time. Delivery of the data is not affected. Note that if the value of the "noLaterThan" attribute is non-zero, then it provides the operational upper-bounds for the "reportAfter" attribute.
If this option is present in the "data" operation (c.f., Section 4.4.4 of [RFC3340] (Rose, M., Klyne, G., and D. Crocker, “The Application Exchange Core,” July 2002.)) and the value of the "reportAfter" attribute is non-zero, then:
TOC |
If the APEX report service (c.f., Section 6.2 of [RFC3340] (Rose, M., Klyne, G., and D. Crocker, “The Application Exchange Core,” July 2002.)) is invoked to send a transient timing report, it issues a data operation with:
For example:
+-------+ +-------+ | | -- data -------> | | | appl. | | relay | | #1 | <--------- ok -- | | +-------+ +-------+ C: <data content='cid:1@example.com'> <originator identity='fred@example.com' /> <recipient identity='barney@example.com' /> <option internal='dataTiming' targetHop='all' mustUnderstand='true' transID='86'> <dataTiming reportAfter='60000' /> </option> </data> S: <ok /> ... some time later ... +-------+ +-------+ | | <------- data -- | | | relay | | relay | | #n-1 | -- ok ---------> | #n | +-------+ +-------+ C: <data content='#Content'> <originator identity='apex=report@example.com' /> <recipient identity='fred@example.com' /> <data-content Name='Content'> <statusResponse transID='86'> <destination identity='barney@example.com'> <reply code='350' /> </destination> </statusResponse> </data-content> </data> S: <ok />
TOC |
Section 5.3 (Registration: The hold4Endpoint Option) contains the APEX option registration for the "hold4Endpoint" option.
The default behavior of the APEX relaying mesh, in the absence of processing options, is to silently drop data for a recipient if its endpoint isn't attached. The "hold4Endpoint" option provides for data to be queued if the recipient endpoint is not attached.
If this option is present in the "data" operation (c.f., Section 4.4.4 of [RFC3340] (Rose, M., Klyne, G., and D. Crocker, “The Application Exchange Core,” July 2002.)), and the value of the "hold4Endpoint" attribute is true then:
Note that in the absence of an upper-bounds on delivery, such as limits provided by the dataTiming option (The dataTiming Option), the data will be queued indefinitely for the endpoint.
For example:
+-------+ +-------+ | | -- data -------> | | | appl. | | relay | | #1 | <--------- ok -- | | +-------+ +-------+ C: <data content='cid:1@example.com'> <originator identity='fred@example.com' /> <recipient identity='barney@example.com' /> <option internal='hold4Endpoint' /> <option internal='dataTiming' targetHop='all' mustUnderstand='true' transID='86'> <dataTiming noLaterThan='60000' /> </option> </data> S: <ok /> ... some time later the recipient's endpoint attaches ... +-------+ +-------+ | | <----- attach -- | | | | | | | | -- ok ---------> | | | relay | | appl. | | | -- data -------> | #2 | | | | | | | <--------- ok -- | | +-------+ +-------+ C: <attach endpoint='barney@example.com' transID='2'> <option internal='attachOverride' transID='3' /> </attach> S: <ok /> C: <data content='cid:1@example.com'> <originator identity='fred@example.com' /> <recipient identity='barney@example.com' /> <option internal='hold4Endpoint' /> <option internal='dataTiming' targetHop='all' mustUnderstand='true' transID='86'> <dataTiming noLaterThan='18000' /> </option> </data> S: <ok />
TOC |
To detect misconfigurations that cause forwarding loops in the APEX relaying mesh, the APEX pubsub service re-introduces a mechanism similar to the IP TTL (Postel, J., “Internet Protocol,” September 1981.) [RFC0791] mechanism, in the form of an APEX option. Section 5.4 (Registration: The dataHopping Option) contains the APEX option registration for the "dataHopping" option.
If this option is present in the "data" operation (c.f., Section 4.4.4 of [RFC3340] (Rose, M., Klyne, G., and D. Crocker, “The Application Exchange Core,” July 2002.)) and the value of the "noMoreThan" attribute is non-zero, then:
Further, note that because this option is processed on a per-hop basis, the originator must set the "targetHop" attribute to the value "all" and the "mustUnderstand" attribute to the value "true".
If the APEX report service (c.f., Section 6.2 of [RFC3340] (Rose, M., Klyne, G., and D. Crocker, “The Application Exchange Core,” July 2002.)) is invoked to send an error report, it issues a data operation with:
For example:
+-------+ +-------+ | | -- data -------> | | | appl. | | relay | | | <--------- ok -- | #1 | +-------+ +-------+ C: <data content='cid:1@example.com'> <originator identity='appl=pubsub/topic=fred@example.com' /> <recipient identity='barney@example.com' /> <option internal='dataHopping' targetHop='all' mustUnderstand='true' transID='86'> <dataHopping noMoreThan='2' reportErrors='true' /> </option> </data> S: <ok /> +-------+ +-------+ | | -- data -------> | | | relay | | relay | | #1 | <--------- ok -- | #2 | +-------+ +-------+ C: <data content='cid:1@example.com'> <originator identity='appl=pubsub/topic=fred@example.com' /> <recipient identity='barney@example.com' /> <option internal='dataHopping' targetHop='all' mustUnderstand='true' transID='86'> <dataHopping noMoreThan='1' reportErrors='true' /> </option> </data> S: <ok />
relay #2 determines that further relaying is necessary:
+-------+ +-------+ | | <------- data -- | | | relay | | relay | | #1 | -- ok ---------> | #2 | +-------+ +-------+ C: <data content='#Content'> <originator identity='apex=report@example.com' /> <recipient identity='appl=pubsub/topic=fred@example.com' /> <data-content Name='Content'> <statusResponse transID='86'> <destination identity='barney@example.com'> <reply code='550' /> </destination> </statusResponse> </data-content> </data> S: <ok />
TOC |
The APEX option registration template is defined in Section 7.1 of [RFC3340] (Rose, M., Klyne, G., and D. Crocker, “The Application Exchange Core,” July 2002.).
TOC |
- Option Identification:
- attachOverride
- Present in:
- APEX's "attach" element
- Contains:
- nothing
- Processing Rules:
- c.f., Section 1 (The attachOverride Option)
- Contact Information:
- c.f., the "Authors' Addresses" section of this memo
TOC |
- Option Identification:
- dataTiming
- Present in:
- APEX's "data" element
- Contains:
- dataTiming (c.f., Section 6 (The APEX Party Pack DTD))
- Processing Rules:
- c.f., Section 2 (The dataTiming Option)
- Contact Information:
- c.f., the "Authors' Addresses" section of this memo
TOC |
- Option Identification:
- hold4Endpoint
- Present in:
- APEX's "data" element
- Contains:
- nothing
- Processing Rules:
- c.f., Section 3 (The hold4Endpoint Option)
- Contact Information:
- c.f., the "Authors' Addresses" section of this memo
TOC |
- Option Identification:
- dataHopping
- Present in:
- APEX's "data" element
- Contains:
- dataHopping (c.f., Section 6 (The APEX Party Pack DTD))
- Processing Rules:
- c.f., Section 4 (The dataHopping Option)
- Contact Information:
- c.f., the "Authors' Addresses" section of this memo
TOC |
<!-- DTD for the APEX option party pack, as of 2001-05-14 Refer to this DTD as: <!ENTITY % APEXPARTY PUBLIC "-//IETF//DTD APEX PARTY//EN" ""> %APEXPARTY; --> <!ENTITY % APEXCORE PUBLIC "-//IETF//DTD APEX CORE//EN" %APEXCORE; <!-- DTD data types: entity syntax/reference example ====== ================ ======= hopcount HOPS 0..255 17 milli-seconds MILLISECS 0..2147483647 60000 --> <!ENTITY % HOPS "CDATA"> <!ENTITY % MILLISECS "CDATA"> <!ELEMENT dataHopping EMPTY> <!ATTLIST dataHopping noMoreThan %HOPS; "0" reportErrors (true|false) "false"> <!ELEMENT dataTiming EMPTY> <!ATTLIST dataTiming noLaterThan %MILLISECS; "0" returnTrip %MILLISECS; "0" reportAfter %MILLISECS; "0" reportErrors (true|false) "false">
TOC |
Consult [RFC3340] (Rose, M., Klyne, G., and D. Crocker, “The Application Exchange Core,” July 2002.)'s Section 11 for a discussion of security issues.
In addition:
TOC |
[RFC3340] | Rose, M., Klyne, G., and D. Crocker, “The Application Exchange Core,” RFC 3340, July 2002. |
[RFC0791] | Postel, J., “Internet Protocol,” STD 5, RFC 791, September 1981 (TXT). |
[RFC2852] | Newman, D., “Deliver By SMTP Service Extension,” RFC 2852, June 2000 (TXT). |
TOC |
The authors gratefully acknowledge the contributions of Chris Newman and Bob Wyman. Further, the dataTiming option is similar in function to "Deliver By" SMTP service extension defined by Dan Newman in [RFC2852] (Newman, D., “Deliver By SMTP Service Extension,” June 2000.).
TOC |
The IANA completed the registrations specified in Section 5 (Initial Registrations).
TOC |
Graham Klyne | |
Clearswift Corporation | |
1310 Waterside | |
Arlington Business Park | |
Theale, Reading RG7 4SA | |
UK | |
Phone: | +44 11 8903 8903 |
Email: | Graham.Klyne@MIMEsweeper.com |
Marshall T. Rose | |
Dover Beach Consulting, Inc. | |
POB 255268 | |
Sacramento, CA 95865-5268 | |
US | |
Phone: | +1 916 483 8878 |
Email: | mrose@dbc.mtview.ca.us |
Michael F. Schwartz | |
Code On The Road, LLC | |
Email: | schwartz@CodeOnTheRoad.com |
URI: | http://www.CodeOnTheRoad.com |
Eric Dixon | |
Email: | edixon@myrealbox.com |
Huston Franklin | |
Email: | huston@franklin.ro |
Jay Kint | |
Email: | d20@icosahedron.org |
Darren New | |
5390 Caminito Exquisito | |
San Diego, CA 92130 | |
US | |
Phone: | +1 858 350 9733 |
Email: | dnew@san.rr.com |
Scott Pead | |
Email: | spead@fiber.net |
TOC |
Copyright © The Internet Society (2002). All Rights Reserved.
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.
The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an “AS IS” basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING 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.
The IETF takes no position regarding the validity or scope of any intellectual property or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; neither does it represent that it has made any effort to identify any such rights. Information on the IETF's procedures with respect to rights in standards-track and standards-related documentation can be found in BCP 11. Copies of claims of rights made available for publication and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementors or users of this specification can be obtained from the IETF Secretariat.
The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights which may cover technology that may be required to practice this standard. Please address the information to the IETF Executive Director.
Funding for the RFC Editor function is currently provided by the Internet Society.