Calendaring Extensions R. Stepanek Internet-Draft Fastmail Updates: 6350 (if approved) M. Loffredo Intended status: Standards Track IIT-CNR Expires: 4 December 2023 2 June 2023 vCard Format Extension for JSContact draft-ietf-calext-vcard-jscontact-extensions-07 Abstract This document defines a set of new properties for vCard and extends the use of existing ones. Their primary purpose is to align the same set of features between the JSContact and vCard formats, but the new definitions also aim to be useful within just the vCard format. This document updates RFC 6350 (vCard). Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on 4 December 2023. Copyright Notice Copyright (c) 2023 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/ license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Stepanek & Loffredo Expires 4 December 2023 [Page 1] Internet-Draft vCard JSContact Extensions June 2023 This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Notational Conventions . . . . . . . . . . . . . . . . . 3 1.2. ABNF Notations . . . . . . . . . . . . . . . . . . . . . 3 2. New Properties . . . . . . . . . . . . . . . . . . . . . . . 3 2.1. CONTACT-BY Property . . . . . . . . . . . . . . . . . . . 3 2.2. CREATED Property . . . . . . . . . . . . . . . . . . . . 4 2.3. DEFLANGUAGE Property . . . . . . . . . . . . . . . . . . 5 2.4. GRAMGENDER Property . . . . . . . . . . . . . . . . . . . 6 2.5. PRONOUNS Property . . . . . . . . . . . . . . . . . . . . 7 2.6. SOCIALPROFILE Property . . . . . . . . . . . . . . . . . 8 3. New Parameters . . . . . . . . . . . . . . . . . . . . . . . 9 3.1. AUTHOR Parameter . . . . . . . . . . . . . . . . . . . . 9 3.2. AUTHOR-NAME Parameter . . . . . . . . . . . . . . . . . . 10 3.3. CREATED Parameter . . . . . . . . . . . . . . . . . . . . 10 3.4. DERIVED Parameter . . . . . . . . . . . . . . . . . . . . 10 3.5. RANKS Parameter . . . . . . . . . . . . . . . . . . . . . 11 3.6. PROP-ID Parameter . . . . . . . . . . . . . . . . . . . . 12 3.7. SERVICE-TYPE Parameter . . . . . . . . . . . . . . . . . 13 3.8. USERNAME Parameter . . . . . . . . . . . . . . . . . . . 13 4. New Values . . . . . . . . . . . . . . . . . . . . . . . . . 14 4.1. Billing Address Type Value . . . . . . . . . . . . . . . 14 4.2. Delivery Address Type Value . . . . . . . . . . . . . . . 14 5. Security Considerations . . . . . . . . . . . . . . . . . . . 14 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 16 7.1. Normative References . . . . . . . . . . . . . . . . . . 16 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17 Stepanek & Loffredo Expires 4 December 2023 [Page 2] Internet-Draft vCard JSContact Extensions June 2023 1. Introduction The JSContact [I-D.ietf-calext-jscontact] format aims to be an alternative to the vCard [RFC6350] format for representation of contact and address book data. As such, it introduces new semantics that are not covered in the current definition of vCard and its various extensions. Converting contact data between the two formats is defined in [I-D.ietf-calext-jscontact-vcard] with the goal of not losing any semantics during conversion. In order to do so, this document defines a new set of properties for vCard and extends existing definitions. 1.1. Notational Conventions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. 1.2. ABNF Notations The ABNF definitions in this document use the notations of [RFC5234]. ABNF rules not defined in this document either are defined in [RFC5234] (such as the ABNF for CRLF, WSP, DQUOTE, VCHAR, ALPHA, and DIGIT) or [RFC6350]. 2. New Properties 2.1. CONTACT-BY Property Property name: CONTACT-BY Purpose: This property defines which contact channels the entity associated with this vCard prefers to be contacted with. Value type: A single text value, restricted to an enumerated list of allowed values. Cardinality: * Property parameters: The PREF parameter defines the preference of this contact channel in relation to other contact channels. The TYPE parameter defines when to use this preference. Description: This defines an order of preferences for contact Stepanek & Loffredo Expires 4 December 2023 [Page 3] Internet-Draft vCard JSContact Extensions June 2023 channels. The contact channels supported in this specification are phone numbers, email, instant messaging and postal delivery. They are identified by the name of the respective vCard property. Format definition: This property is defined by the following notation: contactby = "CONTACT-BY" *(";" contactby-param ) ":" contactby-value contactby-param = type-param / pref-param / any-param contactby-value = "ADR" / "EMAIL" / "IMPP" / "TEL" / x-name Example(s): CONTACT-BY;TYPE=work;PREF=1:EMAIL CONTACT-BY;TYPE=work;PREF=2:TEL CONTACT-BY;TYPE=home:TEL 2.2. CREATED Property Property name: CREATED Purpose: This property defines the date and time when the vCard was created Value type: A single timestamp value. Cardinality: *1 Property parameters: VALUE Description: This is the time stamp when the vCard was created. Copying the vCard across systems does not count as a new creation, nor does a new revision. Instead, the time stamp value typically stays unchanged for the existence of the vCard. Format definition: This property is defined by the following notation: Stepanek & Loffredo Expires 4 December 2023 [Page 4] Internet-Draft vCard JSContact Extensions June 2023 created = "CREATED" createdparam ":" timestamp createdparam = *( ; ; The following are OPTIONAL, ; but MUST NOT occur more than once. ; (";" "VALUE" "=" "timestamp") / ; ; The following are OPTIONAL, ; and MAY occur more than once. ; (";" any-param) ; ) Example(s): CREATED:20220705093412Z CREATED;VALUE=TIMESTAMP:20211022T140000-05 2.3. DEFLANGUAGE Property Property name: DEFLANGUAGE Purpose: This property defines the default language that human- readable text values in this vCard should be assumed written in. Value type: A single Language-Tag value as defined in Section 4 of [RFC6350]. Cardinality: *1 Property parameters: The LANGUAGE parameter MUST NOT be assigned to this property. Description: This property defines the language in which property values of type TEXT shall be assumed to be written for this vCard. If a vCard property includes the LANGUAGE parameter, then the parameter value has higher precedence than the DEFLANGUAGE property value. Format definition: This property is defined by the following notation: deflanguage = "DEFLANGUAGE" any-param ":" Language-Tag ; Language-Tag is defined in RFC6350, Section 4. Stepanek & Loffredo Expires 4 December 2023 [Page 5] Internet-Draft vCard JSContact Extensions June 2023 Example(s): DEFLANGUAGE:de-AT 2.4. GRAMGENDER Property Property name: GRAMGENDER Purpose: This property defines which grammatical gender to use in salutations and other grammatical constructs. Value type: A single text value, restricted to an enumerated list of allowed values. Cardinality: * Property parameters: LANG Description: This property defines the grammatical gender that the contact prefers to be addressed by or referred at in written or spoken form. For example, the German language distinguishes by grammatical gender in salutations such as "Sehr geehrte" (feminine) and "Sehr geehrter" (masculine). Multiple occurrences of this property MUST be distinguished by the LANG parameter. Format definition: This property is defined by the following notation: Stepanek & Loffredo Expires 4 December 2023 [Page 6] Internet-Draft vCard JSContact Extensions June 2023 gramgender = "GRAMGENDER" gramgender-param ":" gramgender-value gramgender-param = *( ; ; The following are OPTIONAL, ; but MUST NOT occur more than once. ; (";" language-param) / ; ; The following are OPTIONAL, ; and MAY occur more than once. ; (";" any-param) ; ) gramgender-value = "animate" / "common" / "feminine" / "inanimate" / "masculine" / "neuter" / iana-token / x-name Example(s): GRAMGENDER:neuter 2.5. PRONOUNS Property Property name: PRONOUNS Purpose: This property defines the pronouns that shall be used to refer to the entity represented by this vCard. Value type: A single text value. Cardinality: * Property parameters: LANG, PREF, TYPE Description: This property contains the pronouns that the contact chooses to use for themselves. The value is free-form text. These pronouns shall be used when addressing or referring to the contact. Multiple occurrences of this property MAY define pronouns for multiple languages, preferences and contexts. Stepanek & Loffredo Expires 4 December 2023 [Page 7] Internet-Draft vCard JSContact Extensions June 2023 Multiple pronouns in the same language SHOULD use the PREF parameter, otherwise the order of preference is implementation- specific. Format definition: This property is defined by the following notation: pronouns = "PRONOUNS" pronouns-param ":" text pronouns-param = *( ; ; The following are OPTIONAL, ; but MUST NOT occur more than once. ; (";" language-param) / (";" pref-param) / (";" type-param) / (";" altid-param) / ; ; The following are OPTIONAL, ; and MAY occur more than once. ; (";" any-param) ; ) Example(s): PRONOUNS;LANG=en;PREF=1:xe/xir PRONOUNS;LANG=en;PREF=2:they/them 2.6. SOCIALPROFILE Property Property name: SOCIALPROFILE Purpose: To specify the URI or username for social media profiles associated with the object the vCard represents. Value type: A single URI or TEXT value. The default value type is URI. Cardinality: * Property parameters: The SERVICE-TYPE parameter MUST be assigned to this property if the value type is TEXT, it MAY be assigned if the value type is URI. In either case, it MUST NOT be assigned more than once. Stepanek & Loffredo Expires 4 December 2023 [Page 8] Internet-Draft vCard JSContact Extensions June 2023 Description: Several vCard address book implementations currently use an experimental X-SOCIALPROFILE property to store social media profiles for contacts. This specification provides an IANA- registered property for the same purpose. In addition to the typical use of this property with URI values, it also allows setting usernames for social media services as free-text TEXT values, in which case the service name MUST be provided as a parameter. Names MUST be considered equal if they match case- insensitively. Format definition: This property is defined by the following notation: socialpr = "SOCIALPROFILE" socialpr-param ":" socialpr-value socialpr-param = "VALUE=uri" / "VALUE=text" / service-type-param / any-param socialpr-value = URI / text Example(s): SOCIALPROFILE;SERVICE-TYPE=Mastodon:https://example.com/@foo SOCIALPROFILE:https://example.com/ietf SOCIALPROFILE;SERVICE-TYPE=SomeSite;VALUE=text:peter94 3. New Parameters 3.1. AUTHOR Parameter Parameter name: AUTHOR Purpose: This parameter identifies the author of the associated property value. Description: This parameter MAY be set on any property where conveying authorship is desired. It identifies the author as a URI [RFC3986]. Since every valid URI includes the COLON (U+003A) character, the parameter value MUST be quoted. Note that as an alternative or in addition to this parameter, the AUTHOR-NAME parameter allows naming an author as free-text value (see Section 3.2). Format definition: author-param = "AUTHOR" "=" DQUOTE URI DQUOTE Example(s): NOTE;AUTHOR="mailto:john@example.com":This is some note. Stepanek & Loffredo Expires 4 December 2023 [Page 9] Internet-Draft vCard JSContact Extensions June 2023 3.2. AUTHOR-NAME Parameter Parameter name: AUTHOR-NAME Purpose: This parameter names the author of the associated property value. Description: This parameter MAY be set on any property where conveying authorship is desired. It names the author as a free- text value. The parameter value MUST NOT be empty. Implementations MUST take care to quote the name part, if otherwise the part would not be a valid param-value (see Section 3.3 of [RFC6350]). Note that as an alternative or in addition to this parameter, the AUTHOR parameter allows identifying an author by URI (see Section 3.1). Format definition: author-name-param = "AUTHOR-NAME" "=" param-value ; not empty Example(s): NOTE;AUTHOR-NAME=John Doe:This is some note. NOTE;AUTHOR-NAME="_:l33tHckr:_":A note by an unusual author name. 3.3. CREATED Parameter Parameter name: CREATED Purpose: This parameter defines the date and time when a property was created in a vCard. Description: This parameter MAY be set on any property to define the point in time when the property was created. The value MUST be a valid TIMESTAMP value as defined in Section 4.3.5 of [RFC6350]. Generally, updating a property value SHOULD NOT change the creation timestamp. Format definition: created-param = "CREATED" "=" param-value ; ; a valid TIMESTAMP of Section 4.3.5 of [RFC6350] Example(s): NOTE;CREATED=20221122T151823Z:This is some note. 3.4. DERIVED Parameter Parameter name: DERIVED Purpose: This parameter specifies that the value of the associated Stepanek & Loffredo Expires 4 December 2023 [Page 10] Internet-Draft vCard JSContact Extensions June 2023 property is derived from some other property value or values. Description: This property parameter MAY be specified on any property when the value is derived from some other property or properties. When present with a value of true, clients MUST NOT update the property. For an example, an implementation may derive the value of the FN property from the name components of the N property. It indicates this by setting the DERIVED parameter on the FN property to true. Format definition: derived-param = "DERIVED" "=" ("true" / "false") ; Default is false Example(s): N:;John;Quinlan;Mr.; FN;DERIVED=TRUE:Mr. John Quinlan 3.5. RANKS Parameter Parameter name: RANKS Purpose: This parameter specifies a ranking among the name components of a vCard N property value. Description: The RANKS parameter on an N property assigns a rank among the same-typed name components of an N property value. Some cultures assign ranks to name components, such as a _first_ and a _second_ surname, or people might prefer to go by their second given name. But the N property value does not allow inferring a culturally or otherwise significant rank from the order in which same-typed name components are stored in it. The parameter value is structurally equivalent to the multivalued N property value: ranks of different name component types are separated by semicolon, ranks among the same-typed name components are separated by comma. The rank is an integer number larger than or equal to 1 and indicates the first or nth rank. Its location within the RANKS parameter value ranks the name component value at that same position within the N property value. An empty or absent rank indicates that the rank of its related name component value is undefined. If the RANKS parameter is set, its value MUST NOT be the empty string. Format definition: NONZERO-DIGIT = %x31-39 ; "1" to "9" Stepanek & Loffredo Expires 4 December 2023 [Page 11] Internet-Draft vCard JSContact Extensions June 2023 ranks-param = ranks-component *4(";" ranks-component) ranks-component = rank *("," rank) rank = (NONZERO-DIGIT *DIGIT) / "" Example(s): This example assigns ranks to two surnames. The culturally first surname is Rodriguez but it appears at the second position in the N property. Accordingly the RANKS parameter assigns rank 1 to the second entry in the surname name component. It also assigns rank 2 to the first entry in the same name component. It does not assign any rank to the personal name or any other name components. N;RANKS="2,1":Gómez,Rodriguez;Pablo;;; Example(s): This example assigns ranks to both the surname and personal name components. The writer "Dame Mary Barbara Hamilton Cartland" published most of her work under the "Barbara Cartland" and this is reflected in the ranks. The RANKS parameter assigns rank 1 to the second entry in the surname name component. It leaves the rank of "Hamilton" undefined. Similarly, it assigns rank 1 to the second entry in the personal name component and leaves "Mary" unranked. There is no rank assigned to the honorific prefix "Dame". N;RANKS=",1;,1":Hamilton,Cartland;Mary,Barbara;;Dame; 3.6. PROP-ID Parameter Parameter name: PROP-ID Purpose: This parameter identifies a property among all its siblings of the same property name. Description: This parameter uniquely identifies a property among all of its siblings with the same name within a vCard. A valid PROP- ID value must be of 1 and a maximum of 255 octets in size, and it MUST only contain the ASCII alphanumeric characters (A-Za-z0-9), hyphen (-), and underscore (_). The identifier only has the purpose to uniquely identify siblings, its value has no other meaning. If an application makes use of PROP-ID it SHOULD assign a unique identifier to each sibling property of the same name within their embedding component. The same identifier MAY be used for properties of a different name, and it MAY also be assigned to a same-named property that is not a sibling. Resolving duplicate identifier conflicts is specific to the application. Similarly, handling properties where some but not all siblings have a PROP-ID is assigned, is application-specific. Stepanek & Loffredo Expires 4 December 2023 [Page 12] Internet-Draft vCard JSContact Extensions June 2023 Format definition: prop-id-param = "PROP-ID" "=" 1*255(ALPHA / DIGIT / "-"/ "_") Example(s): PHOTO;PROP-ID=p827:data:image/jpeg;base64,MIICajCCAdOgAwIBAg <...remainder of base64-encoded data...> 3.7. SERVICE-TYPE Parameter Parameter name: SERVICE-TYPE Purpose: To define the online service name associated with a messaging or social media profile. Description: This parameter MAY be specified on a IMPP or SOCIALPROFILE property to name the online service associated with that property value. Its value is case-sensitive, its letter cases MUST be preserved. Several vCard address book implementations currently use an experimental X-SERVICE-TYPE parameter. This specification provides an IANA-registered parameter for the same purpose. Format definition: service-type-param = "SERVICE-TYPE" "=" param-value Example(s): SOCIALPROFILE;SERVICE-TYPE=Mastodon:https://example.com/@foo 3.8. USERNAME Parameter Parameter name: USERNAME Purpose: To define a user name, such as the user of a messaging or social media service. Description: This parameter MAY be specified on a IMPP or SOCIALPROFILE property to name the user with that property value. Its value is case-sensitive, its letter cases MUST be preserved. The IMPP or SOCIALPROFILE value type MUST be URI. Format definition: username-param = "USERNAME" "=" param-value Example(s): SOCIALPROFILE;USERNAME="The Foo":https://example.com/@foo Stepanek & Loffredo Expires 4 December 2023 [Page 13] Internet-Draft vCard JSContact Extensions June 2023 4. New Values 4.1. Billing Address Type Value Value: billing Purpose: This indicates to use this address for billing, e.g. to send invoices to. Conformance: This value can be used with the "TYPE" parameter applied on the "ADR" property. Example(s): ADR;TYPE=billing:;;123 Main Street;Any Town;CA;91921-1234;U.S.A. 4.2. Delivery Address Type Value Value: delivery Purpose: This indicates to use this address for delivery, e.g. to send packages to. Conformance: This value can be used with the "TYPE" parameter applied on the "ADR" property. Example(s): ADR;TYPE=delivery:;;123 Main Street;Any Town;CA;91921-1234;U.S.A. 5. Security Considerations This specification extends the vCard Format Specification. The same security considerations as outlined in Section 9 of [RFC6350] apply. 6. IANA Considerations IANA is requested to add the following entries to the "vCard Properties" registry, defined in Section 10.3.1. of [RFC6350]. Stepanek & Loffredo Expires 4 December 2023 [Page 14] Internet-Draft vCard JSContact Extensions June 2023 +===========+===============+============================+ | Namespace | Property | Reference | +===========+===============+============================+ | | CONTACT-BY | This document, Section 2.1 | +-----------+---------------+----------------------------+ | | CREATED | This document, Section 2.2 | +-----------+---------------+----------------------------+ | | DEFLANGUAGE | This document, Section 2.3 | +-----------+---------------+----------------------------+ | | GRAMGENDER | This document, Section 2.4 | +-----------+---------------+----------------------------+ | | PRONOUNS | This document, Section 2.5 | +-----------+---------------+----------------------------+ | | SOCIALPROFILE | This document, Section 2.6 | +-----------+---------------+----------------------------+ Table 1: New VCARD Properties IANA is requested to add the following entries to the "vCard Parameters" registry, defined in Section 10.3.2. of [RFC6350]. +===========+==============+============================+ | Namespace | Parameter | Reference | +===========+==============+============================+ | | AUTHOR | This document, Section 3.1 | +-----------+--------------+----------------------------+ | | AUTHOR-NAME | This document, Section 3.2 | +-----------+--------------+----------------------------+ | | CREATED | This document, Section 3.3 | +-----------+--------------+----------------------------+ | | DERIVED | This document, Section 3.4 | +-----------+--------------+----------------------------+ | | PROP-ID | This document, Section 3.6 | +-----------+--------------+----------------------------+ | | RANKS | This document, Section 3.5 | +-----------+--------------+----------------------------+ | | SERVICE-TYPE | This document, Section 3.7 | +-----------+--------------+----------------------------+ | | USERNAME | This document, Section 3.8 | +-----------+--------------+----------------------------+ Table 2: New VCARD Parameters IANA is requested to add the following entries to the "vCard Property Values" registry, defined in Section 10.3.4. of [RFC6350]. Stepanek & Loffredo Expires 4 December 2023 [Page 15] Internet-Draft vCard JSContact Extensions June 2023 +============+===========+============================+ | Property | Value | Reference | +============+===========+============================+ | GRAMGENDER | animate | This document, Section 2.4 | +------------+-----------+----------------------------+ | GRAMGENDER | common | This document, Section 2.4 | +------------+-----------+----------------------------+ | GRAMGENDER | feminine | This document, Section 2.4 | +------------+-----------+----------------------------+ | GRAMGENDER | inanimate | This document, Section 2.4 | +------------+-----------+----------------------------+ | GRAMGENDER | masculine | This document, Section 2.4 | +------------+-----------+----------------------------+ | GRAMGENDER | neuter | This document, Section 2.4 | +------------+-----------+----------------------------+ Table 3: New VCARD Property Values IANA is requested to add the following entries to the "vCard Parameter Values" registry, defined in Section 10.3.4. of [RFC6350]. +==========+===========+==========+============================+ | Property | Parameter | Value | Reference | +==========+===========+==========+============================+ | ADR | TYPE | billing | This document, Section 4.1 | +----------+-----------+----------+----------------------------+ | ADR | TYPE | delivery | This document, Section 4.2 | +----------+-----------+----------+----------------------------+ Table 4: New VCARD Property Values 7. References 7.1. Normative References [I-D.ietf-calext-jscontact] Stepanek, R. and M. Loffredo, "JSContact: A JSON representation of contact data", Work in Progress, Internet-Draft, draft-ietf-calext-jscontact-10, 19 April 2023, . [I-D.ietf-calext-jscontact-vcard] Loffredo, M. and R. Stepanek, "JSContact: Converting from and to vCard", Work in Progress, Internet-Draft, draft- ietf-calext-jscontact-vcard-08, 19 April 2023, . Stepanek & Loffredo Expires 4 December 2023 [Page 16] Internet-Draft vCard JSContact Extensions June 2023 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, DOI 10.17487/RFC3986, January 2005, . [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, DOI 10.17487/RFC5234, January 2008, . [RFC6350] Perreault, S., "vCard Format Specification", RFC 6350, DOI 10.17487/RFC6350, August 2011, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . Authors' Addresses Robert Stepanek Fastmail PO Box 234, Collins St West Melbourne VIC 8007 Australia Email: rsto@fastmailteam.com Mario Loffredo IIT-CNR Via Moruzzi,1 56124 Pisa Italy Email: mario.loffredo@iit.cnr.it Stepanek & Loffredo Expires 4 December 2023 [Page 17]