| draft-ietf-extra-imap-fetch-preview-02.txt | draft-ietf-extra-imap-fetch-preview-03.txt | |||
|---|---|---|---|---|
| EXTRA M. Slusarz | EXTRA M. Slusarz | |||
| Internet-Draft Open-Xchange Inc. | Internet-Draft Open-Xchange Inc. | |||
| Intended status: Standards Track February 13, 2019 | Intended status: Standards Track February 16, 2019 | |||
| Expires: August 17, 2019 | Expires: August 20, 2019 | |||
| IMAP4 Extension: Message Preview Generation | IMAP4 Extension: Message Preview Generation | |||
| draft-ietf-extra-imap-fetch-preview-02 | draft-ietf-extra-imap-fetch-preview-03 | |||
| Abstract | Abstract | |||
| This document specifies an IMAP protocol extension which allows a | This document specifies an Internet Message Access Protocol (IMAP) | |||
| client to request that a server provide an abbreviated representation | protocol extension allowing a client to request a server-generated | |||
| of a message that can be used by a client to provide a useful | abbreviated representation of message data useful as a contextual | |||
| contextual preview of the message contents. | preview of the entire message. | |||
| Status of This Memo | Status of This Memo | |||
| This Internet-Draft is submitted in full conformance with the | This Internet-Draft is submitted in full conformance with the | |||
| provisions of BCP 78 and BCP 79. | provisions of BCP 78 and BCP 79. | |||
| Internet-Drafts are working documents of the Internet Engineering | Internet-Drafts are working documents of the Internet Engineering | |||
| Task Force (IETF). Note that other groups may also distribute | Task Force (IETF). Note that other groups may also distribute | |||
| working documents as Internet-Drafts. The list of current Internet- | working documents as Internet-Drafts. The list of current Internet- | |||
| Drafts is at https://datatracker.ietf.org/drafts/current/. | Drafts is at https://datatracker.ietf.org/drafts/current/. | |||
| Internet-Drafts are draft documents valid for a maximum of six months | Internet-Drafts are draft documents valid for a maximum of six months | |||
| and may be updated, replaced, or obsoleted by other documents at any | and may be updated, replaced, or obsoleted by other documents at any | |||
| time. It is inappropriate to use Internet-Drafts as reference | time. It is inappropriate to use Internet-Drafts as reference | |||
| material or to cite them other than as "work in progress." | material or to cite them other than as "work in progress." | |||
| This Internet-Draft will expire on August 17, 2019. | This Internet-Draft will expire on August 20, 2019. | |||
| Copyright Notice | Copyright Notice | |||
| Copyright (c) 2019 IETF Trust and the persons identified as the | Copyright (c) 2019 IETF Trust and the persons identified as the | |||
| document authors. All rights reserved. | document authors. All rights reserved. | |||
| This document is subject to BCP 78 and the IETF Trust's Legal | This document is subject to BCP 78 and the IETF Trust's Legal | |||
| Provisions Relating to IETF Documents | Provisions Relating to IETF Documents | |||
| (https://trustee.ietf.org/license-info) in effect on the date of | (https://trustee.ietf.org/license-info) in effect on the date of | |||
| publication of this document. Please review these documents | publication of this document. Please review these documents | |||
| skipping to change at page 2, line 18 ¶ | skipping to change at page 2, line 18 ¶ | |||
| 2. Conventions Used In This Document . . . . . . . . . . . . . . 3 | 2. Conventions Used In This Document . . . . . . . . . . . . . . 3 | |||
| 3. FETCH Data Item . . . . . . . . . . . . . . . . . . . . . . . 4 | 3. FETCH Data Item . . . . . . . . . . . . . . . . . . . . . . . 4 | |||
| 3.1. Command . . . . . . . . . . . . . . . . . . . . . . . . . 4 | 3.1. Command . . . . . . . . . . . . . . . . . . . . . . . . . 4 | |||
| 3.2. Response . . . . . . . . . . . . . . . . . . . . . . . . 4 | 3.2. Response . . . . . . . . . . . . . . . . . . . . . . . . 4 | |||
| 4. PREVIEW Algorithms . . . . . . . . . . . . . . . . . . . . . 5 | 4. PREVIEW Algorithms . . . . . . . . . . . . . . . . . . . . . 5 | |||
| 4.1. FUZZY . . . . . . . . . . . . . . . . . . . . . . . . . . 5 | 4.1. FUZZY . . . . . . . . . . . . . . . . . . . . . . . . . . 5 | |||
| 5. PREVIEW Priority Modifiers . . . . . . . . . . . . . . . . . 6 | 5. PREVIEW Priority Modifiers . . . . . . . . . . . . . . . . . 6 | |||
| 5.1. LAZY . . . . . . . . . . . . . . . . . . . . . . . . . . 6 | 5.1. LAZY . . . . . . . . . . . . . . . . . . . . . . . . . . 6 | |||
| 6. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 6 | 6. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 6 | |||
| 7. Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . 8 | 7. Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . 8 | |||
| 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9 | 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 | |||
| 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 | 9. Security Considerations . . . . . . . . . . . . . . . . . . . 10 | |||
| 10. Security Considerations . . . . . . . . . . . . . . . . . . . 10 | 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 | |||
| 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 | 10.1. Normative References . . . . . . . . . . . . . . . . . . 10 | |||
| 11.1. Normative References . . . . . . . . . . . . . . . . . . 10 | 10.2. Informative References . . . . . . . . . . . . . . . . . 11 | |||
| 11.2. Informative References . . . . . . . . . . . . . . . . . 11 | ||||
| Appendix A. Change History (To be removed by RFC Editor before | Appendix A. Change History (To be removed by RFC Editor before | |||
| publication) . . . . . . . . . . . . . . . . . . . . 11 | publication) . . . . . . . . . . . . . . . . . . . . 11 | |||
| Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 12 | Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 13 | |||
| Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 13 | ||||
| 1. Introduction | 1. Introduction | |||
| Many modern mail clients display small extracts of the body text as | Many modern mail clients display small extracts of the body text as | |||
| an aid to allow a user to quickly decide whether they are interested | an aid to allow a user to quickly decide whether they are interested | |||
| in viewing the full message contents. Mail clients implementing the | in viewing the full message contents. Mail clients implementing the | |||
| Internet Message Access Protocol [RFC3501] would benefit from a | Internet Message Access Protocol [RFC3501] would benefit from a | |||
| standardized, consistent way to generate these brief previews of | standardized, consistent way to generate these brief previews of | |||
| messages. | messages. | |||
| skipping to change at page 3, line 25 ¶ | skipping to change at page 3, line 25 ¶ | |||
| sufficient data from a previous partial FETCH to display an adequate | sufficient data from a previous partial FETCH to display an adequate | |||
| representation of the preview. | representation of the preview. | |||
| Finally, server generation allows caching in a centralized location. | Finally, server generation allows caching in a centralized location. | |||
| Using server generated previews allows global generation once per | Using server generated previews allows global generation once per | |||
| message, and then cached indefinitely. Retrieval of message data may | message, and then cached indefinitely. Retrieval of message data may | |||
| be expensive within a server, for example, so a server can be | be expensive within a server, for example, so a server can be | |||
| configured to reduce its storage retrieval load by pre-generating | configured to reduce its storage retrieval load by pre-generating | |||
| preview data. | preview data. | |||
| A server that supports the PREVIEW extension indicates this with one | A server indicates support for this extension by listing one or more | |||
| or more capability names consisting of "PREVIEW=" followed by a | capability names consisting of "PREVIEW=" followed by a supported | |||
| supported preview algorithm name. This format provides for future | preview algorithm name. This format provides for future upwards- | |||
| upwards-compatible extensions and/or the ability to use locally- | compatible extensions and/or the ability to use locally-defined | |||
| defined preview algorithms. | preview algorithms and priority modifiers. | |||
| 2. Conventions Used In This Document | 2. Conventions Used In This Document | |||
| The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", | The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", | |||
| "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and | "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and | |||
| "OPTIONAL" in this document are to be interpreted as described in BCP | "OPTIONAL" in this document are to be interpreted as described in BCP | |||
| 14 [RFC2119] [RFC8174] when, and only when, they appear in all | 14 [RFC2119] [RFC8174] when, and only when, they appear in all | |||
| capitals, as shown here. | capitals, as shown here. | |||
| "User" is used to refer to a human user, whereas "client" refers to | "User" is used to refer to a human user, whereas "client" refers to | |||
| skipping to change at page 8, line 42 ¶ | skipping to change at page 8, line 42 ¶ | |||
| S: E1 OK Capability command completed. | S: E1 OK Capability command completed. | |||
| [...a mailbox is SELECTed...] | [...a mailbox is SELECTed...] | |||
| C: E2 SEARCH RETURN (SAVE) FROM "FOO" | C: E2 SEARCH RETURN (SAVE) FROM "FOO" | |||
| C: E3 FETCH $ (UID PREVIEW (LAZY=FUZZY)) | C: E3 FETCH $ (UID PREVIEW (LAZY=FUZZY)) | |||
| S: E2 OK SEARCH completed. | S: E2 OK SEARCH completed. | |||
| S: * 5 FETCH (UID 13 PREVIEW (FUZZY "Preview!")) | S: * 5 FETCH (UID 13 PREVIEW (FUZZY "Preview!")) | |||
| S: * 9 FETCH (UID 23 PREVIEW (FUZZY NIL)) | S: * 9 FETCH (UID 23 PREVIEW (FUZZY NIL)) | |||
| S: E3 OK FETCH completed. | S: E3 OK FETCH completed. | |||
| [...Retrieve message 9 preview in background...] | [...Retrieve message 9 preview in background...] | |||
| C: E4 UID FETCH 23 (PREVIEW (FUZZY)) | C: E4 UID FETCH 23 (PREVIEW (FUZZY)) | |||
| S: * 9 FETCH (PREVIEW (FUZZY "Another preview!")) | S: * 9 FETCH (UID 23 PREVIEW (FUZZY "Another preview!")) | |||
| S: E4 OK FETCH completed. | S: E4 OK FETCH completed. | |||
| 7. Formal Syntax | 7. Formal Syntax | |||
| The following syntax specification uses the augmented Backus-Naur | The following syntax specification uses the augmented Backus-Naur | |||
| Form (BNF) as described in ABNF [RFC5234]. It includes definitions | Form (BNF) as described in ABNF [RFC5234]. It includes definitions | |||
| from IMAP [RFC3501]. | from IMAP [RFC3501]. | |||
| capability =/ "PREVIEW=" (preview-alg / preview-mod-ext) | capability =/ "PREVIEW=" (preview-alg / preview-mod-ext) | |||
| skipping to change at page 9, line 32 ¶ | skipping to change at page 9, line 32 ¶ | |||
| preview-atom = 1*<any ATOM-CHAR except "="> | preview-atom = 1*<any ATOM-CHAR except "="> | |||
| preview-mod = "LAZY" / preview-mod-ext | preview-mod = "LAZY" / preview-mod-ext | |||
| preview-mod-ext = preview-atom ; New priority modifier names | preview-mod-ext = preview-atom ; New priority modifier names | |||
| ; SHOULD be registered with IANA | ; SHOULD be registered with IANA | |||
| ; and MUST conform with the | ; and MUST conform with the | |||
| ; recommendations described in | ; recommendations described in | |||
| ; RFC 6648, Section 3 | ; RFC 6648, Section 3 | |||
| 8. Acknowledgements | 8. IANA Considerations | |||
| The author would like to thank the following people for their | ||||
| comments and contributions to this document: Stephan Bosch, Bron | ||||
| Gondwana, Teemu Huovila, Steffen Lehmann, Alexey Melnikov, Chris | ||||
| Newman, Jeff Sipek, Timo Sirainen, Steffen Templin, and Aki Tuomi. | ||||
| 9. IANA Considerations | ||||
| IMAP4 [RFC3501] capabilities are registered by publishing a standards | IMAP4 [RFC3501] capabilities are registered by publishing a standards | |||
| track or IESG-approved experimental RFC. The registry is currently | track or IESG-approved experimental RFC. The registry is currently | |||
| located at: | located at: | |||
| http://www.iana.org/assignments/imap-capabilities | http://www.iana.org/assignments/imap-capabilities | |||
| This document requests that IANA adds the "PREVIEW=FUZZY" capability | This document requests that IANA adds the "PREVIEW=FUZZY" capability | |||
| to the IMAP4 [RFC3501] capabilities registry. | to the IMAP4 [RFC3501] capabilities registry. | |||
| This document requests that IANA create a new PREVIEW algorithms | This document requests that IANA create a new PREVIEW algorithms | |||
| registry, which registers preview algorithms by publishing a | registry, which registers preview algorithms by publishing a | |||
| standards track or IESG-approved experimental RFC. This document | standards track or IESG-approved experimental RFC. This document | |||
| constitutes registration of the FUZZY algorithm in that registry. | constitutes registration of the FUZZY algorithm in that registry. | |||
| This document requests that IANA create a new PREVIEW modifiers | This document requests that IANA create a new PREVIEW priority | |||
| registry, which registers preview modifiers by publishing a standards | modifiers registry, which registers preview priority modifiers by | |||
| track or IESG-approved experimental RFC. This document constitutes | publishing a standards track or IESG-approved experimental RFC. This | |||
| registration of the LAZY modifier in that registry. | document constitutes registration of the LAZY priority modifier in | |||
| that registry. | ||||
| 10. Security Considerations | 9. Security Considerations | |||
| Implementation of this extension might enable denial-of-service | Implementation of this extension might enable denial-of-service | |||
| attacks against server resources, due to excessive memory or CPU | attacks against server resources, due to excessive memory or CPU | |||
| usage during preview generation or increased storage usage if preview | usage during preview generation or increased storage usage if preview | |||
| results are stored on the server after generation. Servers MAY limit | results are stored on the server after generation. Servers MAY limit | |||
| the resources that preview generation uses. | the resources that preview generation uses. | |||
| 11. References | 10. References | |||
| 11.1. Normative References | 10.1. Normative References | |||
| [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate | [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate | |||
| Requirement Levels", BCP 14, RFC 2119, | Requirement Levels", BCP 14, RFC 2119, | |||
| DOI 10.17487/RFC2119, March 1997, | DOI 10.17487/RFC2119, March 1997, | |||
| <https://www.rfc-editor.org/info/rfc2119>. | <https://www.rfc-editor.org/info/rfc2119>. | |||
| [RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION | [RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION | |||
| 4rev1", RFC 3501, DOI 10.17487/RFC3501, March 2003, | 4rev1", RFC 3501, DOI 10.17487/RFC3501, March 2003, | |||
| <https://www.rfc-editor.org/info/rfc3501>. | <https://www.rfc-editor.org/info/rfc3501>. | |||
| skipping to change at page 11, line 9 ¶ | skipping to change at page 11, line 5 ¶ | |||
| [RFC6648] Saint-Andre, P., Crocker, D., and M. Nottingham, | [RFC6648] Saint-Andre, P., Crocker, D., and M. Nottingham, | |||
| "Deprecating the "X-" Prefix and Similar Constructs in | "Deprecating the "X-" Prefix and Similar Constructs in | |||
| Application Protocols", BCP 178, RFC 6648, | Application Protocols", BCP 178, RFC 6648, | |||
| DOI 10.17487/RFC6648, June 2012, | DOI 10.17487/RFC6648, June 2012, | |||
| <https://www.rfc-editor.org/info/rfc6648>. | <https://www.rfc-editor.org/info/rfc6648>. | |||
| [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC | [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC | |||
| 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, | 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, | |||
| May 2017, <https://www.rfc-editor.org/info/rfc8174>. | May 2017, <https://www.rfc-editor.org/info/rfc8174>. | |||
| 11.2. Informative References | 10.2. Informative References | |||
| [RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail | [RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail | |||
| Extensions (MIME) Part One: Format of Internet Message | Extensions (MIME) Part One: Format of Internet Message | |||
| Bodies", RFC 2045, DOI 10.17487/RFC2045, November 1996, | Bodies", RFC 2045, DOI 10.17487/RFC2045, November 1996, | |||
| <https://www.rfc-editor.org/info/rfc2045>. | <https://www.rfc-editor.org/info/rfc2045>. | |||
| [RFC2854] Connolly, D. and L. Masinter, "The 'text/html' Media | [RFC2854] Connolly, D. and L. Masinter, "The 'text/html' Media | |||
| Type", RFC 2854, DOI 10.17487/RFC2854, June 2000, | Type", RFC 2854, DOI 10.17487/RFC2854, June 2000, | |||
| <https://www.rfc-editor.org/info/rfc2854>. | <https://www.rfc-editor.org/info/rfc2854>. | |||
| skipping to change at page 12, line 42 ¶ | skipping to change at page 12, line 38 ¶ | |||
| o Removed CAPABILITY string for examples where it did not add | o Removed CAPABILITY string for examples where it did not add | |||
| valuable context | valuable context | |||
| o Altered preview data in examples to cover a variety of potential | o Altered preview data in examples to cover a variety of potential | |||
| server return scenarios | server return scenarios | |||
| o Added "SHOULD be registered" language to algorithm names and | o Added "SHOULD be registered" language to algorithm names and | |||
| priority modifiers | priority modifiers | |||
| Changes from draft-ietf-extra-imap-fetch-preview-02: | ||||
| o Move Acknowledgments to un-numbered appendix | ||||
| o Improved abstract text | ||||
| o Consistently use "priority modifiers" instead of "modifiers" | ||||
| o Update example to conform with RFC 3501 UID FETCH requirements | ||||
| Acknowledgments | ||||
| The author would like to thank the following people for their | ||||
| comments and contributions to this document: Stephan Bosch, Bron | ||||
| Gondwana, Teemu Huovila, Steffen Lehmann, Alexey Melnikov, Chris | ||||
| Newman, Jeff Sipek, Timo Sirainen, Steffen Templin, and Aki Tuomi. | ||||
| Author's Address | Author's Address | |||
| Michael M. Slusarz | Michael M. Slusarz | |||
| Open-Xchange Inc. | Open-Xchange Inc. | |||
| 530 Lytton Avenue | 530 Lytton Avenue | |||
| Palo Alto, California 94301 | Palo Alto, California 94301 | |||
| US | US | |||
| Email: michael.slusarz@open-xchange.com | Email: michael.slusarz@open-xchange.com | |||
| End of changes. 15 change blocks. | ||||
| 37 lines changed or deleted | 48 lines changed or added | |||
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