GEOPRIVNetwork Working Group H. SchulzrinneInternet-DraftRequest for Comments: 4745 Columbia U.Intended status:Category: Standards Track H. TschofenigExpires: February 11, 2007Siemens Networks GmbH & Co KG J. Morris CDT J. Cuellar Siemens J. PolkCiscoJ. Rosenberg CiscoSystems August 10, 2006February 2007 Common Policy: A Document Format for Expressing Privacy Preferencesdraft-ietf-geopriv-common-policy-11.txtStatus ofthisThis MemoBy submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents ofThis document specifies an Internet standards track protocol for the InternetEngineering Task Force (IETF), its areas,community, andits working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents validrequests discussion and suggestions fora maximumimprovements. Please refer to the current edition ofsix monthsthe "Internet Official Protocol Standards" (STD 1) for the standardization state andmay 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." The liststatus ofcurrent Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The listthis protocol. Distribution ofInternet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on February 11, 2007.this memo is unlimited. Copyright Notice Copyright (C) TheInternet Society (2006).IETF Trust (2007). Abstract This document defines a framework for authorization policies controlling access toapplication specificapplication-specific data. This framework combines common location- and presence-specific authorization aspects. An XML schema specifies the language in which common policy rules are represented. The common policy framework can be extended to other application domains. Table of Contents 1. Introduction. . . . . . . . . . . . . . . . . . . . . . . . . 4....................................................3 2. Terminology. . . . . . . . . . . . . . . . . . . . . . . . . 6.....................................................4 3. Modes of Operation. . . . . . . . . . . . . . . . . . . . . . 7..............................................4 3.1. Passive Request-Response - PS as Server (Responder). . . 7........5 3.2. Active Request-Response - PS as Client (Initiator). . . . 7.........5 3.3. Event Notification. . . . . . . . . . . . . . . . . . . . 7.........................................5 4. Goals and Assumptions. . . . . . . . . . . . . . . . . . . . 9...........................................6 5. Non-Goals. . . . . . . . . . . . . . . . . . . . . . . . . . 11.......................................................7 6. Basic Data Model and Processing. . . . . . . . . . . . . . . 12.................................8 6.1. Identification of Rules. . . . . . . . . . . . . . . . . 13....................................9 6.2. Extensions. . . . . . . . . . . . . . . . . . . . . . . . 13.................................................9 7. Conditions. . . . . . . . . . . . . . . . . . . . . . . . . . 14.....................................................10 7.1. Identity Condition. . . . . . . . . . . . . . . . . . . . 14........................................10 7.1.1. Overview. . . . . . . . . . . . . . . . . . . . . . . 14...........................................10 7.1.2. Matching One Entity. . . . . . . . . . . . . . . . . 14................................11 7.1.3. Matching Multiple Entities. . . . . . . . . . . . . . 15.........................11 7.2. Single Entity. . . . . . . . . . . . . . . . . . . . . . 19.............................................14 7.3. Sphere. . . . . . . . . . . . . . . . . . . . . . . . . . 19....................................................15 7.4. Validity. . . . . . . . . . . . . . . . . . . . . . . . . 21..................................................16 8. Actions. . . . . . . . . . . . . . . . . . . . . . . . . . . 23........................................................17 9. Transformations. . . . . . . . . . . . . . . . . . . . . . . 24................................................18 10. Procedure for Combining Permissions. . . . . . . . . . . . . 25...........................18 10.1. Introduction. . . . . . . . . . . . . . . . . . . . . . . 25.............................................18 10.2.Algorithm . . . . . . . . . . . . . . . . . . . . . . . . 25Combining Rules (CRs) ....................................18 10.3. Example. . . . . . . . . . . . . . . . . . . . . . . . . 26..................................................19 11. Meta Policies. . . . . . . . . . . . . . . . . . . . . . . . 29.................................................21 12. Example. . . . . . . . . . . . . . . . . . . . . . . . . . . 30.......................................................21 13. XML Schema Definition. . . . . . . . . . . . . . . . . . . . 31.........................................22 14. Security Considerations. . . . . . . . . . . . . . . . . . . 34.......................................25 15. IANA Considerations. . . . . . . . . . . . . . . . . . . . . 35...........................................25 15.1. Common Policy Namespace Registration. . . . . . . . . . . 35.....................25 15.2. Content-typeregistrationRegistration for 'application/auth-policy+xml'. . . . . . . . . . . . . . 35............................26 15.3. Common Policy Schema Registration. . . . . . . . . . . . 37........................27 16. References. . . . . . . . . . . . . . . . . . . . . . . . . . 38....................................................28 16.1. Normative References. . . . . . . . . . . . . . . . . . . 38.....................................28 16.2. Informative References. . . . . . . . . . . . . . . . . . 38...................................28 Appendix A. Contributors. . . . . . . . . . . . . . . . . . . . 39..........................................29 Appendix B. Acknowledgments. . . . . . . . . . . . . . . . . . . 40 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 41 Intellectual Property and Copyright Statements . . . . . . . . . . 43.......................................29 1. Introduction This document defines a framework for creating authorization policies for access toapplication specificapplication-specific data. This framework is the result of combining the common aspects of single authorization systems that more specifically control access to presence and location information and that previously had been developed separately. The benefit of combining these two authorization systems is two-fold. First, it allowsto buildbuilding a systemwhichthat enhances the value of presence with location information in a natural way and reuses the same underlying authorization mechanism. Second, it encourages a more generic authorization framework with mechanisms for extensibility. The applicability of the framework specified in this document is not limited to policiescontrolingcontrolling access to presence and location information data, but can be extended to other application domains. The general framework defined in this document is intended to be accompanied and enhanced by application-specific policies specified elsewhere. The common policy framework described here is enhanced bydomain-speificdomain-specific policy documents, including presence [7] and location [8]. This relationship is shown in Figure 1. +-----------------+ | | | Common | | Policy | | | +---+---------+---+ /|\ /|\ | | +-------------------+ | | +-------------------+ | | | enhance | | | | Location-specific | | | | Presence-specific | | Policy |----+ +----| Policy | | | | | +-------------------+ +-------------------+ Figure 1: Common Policy Enhancements This document starts with an introduction to the terminology in Section 2, an illustration of basic modes of operation in Section 3, a description of goals (see Section 4) and non-goals (see Section 5) of the policy framework, followed by the data model in Section 6. The structure of a rule,namelynamely, conditions,actionsactions, and transformations,areis described inSectionSections 7,in Section 88, andin Section9. The procedure for combining permissions is explained in Section 10 and used when conditions for more than one rulefires.are satisfied. A short description of meta policies is given in Section 11. An example is provided in Section 12. The XML schema will be discussed in Section 13. IANA considerations in Section 15 follow security considerations in Section 14. 2. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT","RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [1]. This document introduces the following terms: PT - Presentity / Target: The PT is the entity about whom information has been requested. RM - Rule Maker: The RM is an entitywhichthat creates the authorization ruleswhichthat restrict access to data items. PS - (Authorization) Policy Server: This entity has access to both the authorization policies andtothe data items. In location- specific applications, the entity PS is labeled as location server (LS). WR - Watcher / Recipient: This entity requests access to data items of the PT. An access operation might beeither bea read,writea write, orbeany other operation.In case of access to location information it might be a read operation.A policy is given by a 'rule set' that contains an unordered list of 'rules'. A 'rule' has a 'conditions', an'actions''actions', and a 'transformations' part. The term 'permission' indicates the action and transformation components of a 'rule'. The term 'using protocol' is defined in [9]. It refers to the protocolwhich isused to request access to and to returnprivacy sensitiveprivacy-sensitive data items. 3. Modes of Operation The abstract sequence of operations can roughly be described as follows. The PS receives a query for data items for a particular PT, via the using protocol. The using protocol (or morepreciselyprecisely, the authentication protocol) provides the identity of the requestor, either at the time of the query or at the subscription time. The authenticated identity of the WR, together with other information provided by the using protocol or generally available to the server, is then used for searching through the rule set. All matching rules are combined according to a permission combining algorithm described in Section 10. The combined rules are applied to the application data, resulting in the application of privacy based on the transformation policies. The resulting application data is returned to the WR. Three different modes of operation can be distinguished: 3.1. Passive Request-Response - PS as Server (Responder) In a passive request-response mode, the WR queries the PS for data items about the PT. Examples of protocols following this mode of operation include HTTP, FTP, LDAP,finger orfinger, and variousRPCremote procedure call (RPC) protocols, including Sun RPC,DCE, DCOM, Corba and SOAP.Distributed Computing Environment (DCE), Distributed Component Object Model (DCOM), common object request broker architecture (Corba), and Simple Object Access Protocol (SOAP). The PS uses therulesetrule set to determine whether the WR is authorized to access thePTsPT's information, refusing the request if necessary. Furthermore, the PS might filter information by removing elements or by reducing the resolution of elements. 3.2. Active Request-Response - PS as Client (Initiator) Alternatively, the PS may contact the WR and convey data items. Examples include HTTP, SIP session setup (INVITE request), H.323 session setup or SMTP. 3.3. Event Notification Event notification adds a subscription phase to the "Active Request- Response - PS as Client (Initiator)" mode of operation. A watcher or subscriber asks to be added to the notification list for a particular presentity or event. When the presentity changes state or the event occurs, the PS sends a message to the WR containing the updated state. (Presence is a special case of event notification; thus, we often use the term interchangeably.) In addition, the subscriber may itself add a filter to the subscription, limiting the rate or content of the notifications. If an event, after filtering by therulemaker-providedrule-maker-provided rules and by the subscriber-provided rules, only produces the same notification content that was sent previously, no event notification is sent. A single PS may authorize access to data items in more than one mode. Rather than having different rule sets for different modes all three modes are supported with a one rule set schema. Specific instances of the rule set can omit elements that are only applicable to the subscription model. 4. Goals and Assumptions Below, we summarize our design goals and constraints. Table representation: Each rule must be representable as a row in a relational database. This design goal should allow efficient policy implementation by utilizing standard database optimization techniques. Permit only: Rules only provide permissions rather than denying them. Removing a rule can never increase permissions.Allowing both 'permit' and 'deny' actions would require some rule ordering which had implicationsDepending on the interpretation of 'deny' and 'permit' rules, the ordering of rules might matter, making updating rule sets more complicated since such updateoperations executed on these rules.mechanisms would have to support insertion at specific locations in the rule set. Additionally, it would make distributed rule sets more complicated. Hence, only 'permit' actions are allowedwhichthat result in more efficient rule processing. This also implies that rule ordering is not important. Consequently, to make a policy decision requires processing all rules. Additive permissions: A query for access to data items is matched against the rules in the rule database. If several rules match, then the overall permissions granted to the WR are the union of those permissions. A more detailed discussion is providedinSectionin Section 10. Upgradeable: It should be possible to add additional rules later, without breaking PSs that have not been upgraded. Any such upgrades must not degrade privacy constraints, but PSs not yet upgraded may reveal less information than therulemakerrule maker would have chosen. Capability support: In addition to the previous goal, a RM should be able to determine which extensions are supported by the PS. The mechanism used to determine the capability of a PS is outside the scope of this specification. Protocol-independent: The rule set supports constraints on both notifications or queries as well as subscriptions for event-based systems such as presence systems. No false assurance: It appears more dangerous to give the user the impression that the system will prevent disclosure automatically, but fail to do so with a significant probability of operator error or misunderstanding, than to force the user to explicitly invoke simpler rules. For example, rules based on weekday and time-of- day ranges seem particularly subject to misinterpretation and false assumptions on part of the RM. (For example, a non- technical RM would probably assume that the rules are based on thetimezonetime zone of his current location, which may not be known to other components of the system.) 5. Non-Goals We explicitly decided that a number of possibly worthwhile capabilities are beyond the scope of this first version. Future versions may include these capabilities, using the extension mechanism described in this document. Non-goals include: No external references: Attributes within specific rules cannot refer to external rule sets, databases,directoriesdirectories, or other network elements. Any such external reference would make simple database implementation difficult and hence they are not supported in this version. No regularexpression:expressions: Conditions are matched on equality or 'greater-than'-style comparisons, not regular expressions, partial matches such as the SQL LIKE operator (e.g., LIKE"%foo%")"%foo%"), or glob-style matches ("*@example.com"). Most of these are better expressed as explicit elements. No repeat times: Repeat times (e.g., every day from9am9 am to4pm)4 pm) are difficult to make work correctly, due to the different time zones that PT, WR,PSPS, and RM may occupy. It appears that suggestions for including time intervals are often based on supporting work/non-work distinctions, which unfortunately are difficult to capture by time alone. Note that this feature must not be confused with the 'Validity' element that provides a mechanism to restrict the lifetime of a rule. 6. Basic Data Model and Processing A rule set (or synonymously, a policy) consists of zero or more rules. The ordering of these rules is irrelevant. The rule set can be stored at the PS and conveyed from RM to PS as a single document, in subsets or as individual rules. A rule consists of threeparts -parts: conditions (see Section 7), actions (see Section 8), and transformations (see Section 9). The conditions part is a set of expressions, each of which evaluates to either TRUE orFALSE, i.e. each of which is equipped with a value of either TRUE or FALSE by the PS.FALSE. When a WR asks for information about a PT, the PS goes through each rule in the rule set. For each rule, it evaluates the expressions in the conditions part. If all of the expressions evaluate to TRUE, then the rule is applicable to this request. Generally, each expression specifies a condition based on some variable that is associated with the context of the request. These variables can include the identity of the WR, the domain of the WR, the time of day, or even external variables, such as the temperature or the mood of the PT. Assuming that the rule is applicable to the request, the actions and transformations (commonly referred to as permissions) in the rule specify how the PS is supposed to handle this request. If the request is to view the location of the PT, or to view its presence, the typical action is "permit", which allows the request to proceed. Assuming the action allows the request to proceed, the transformations part of the rule specifies how the information about the PT--- their location information, their presence, etc.--- is modified before being presented to the WR. These transformations are in the form of positive permissions. That is, they always specify a piece of informationwhichthat is allowed to be seen by the WR. When a PS processes a request, it takes the transformations specified across all rules that match, and creates the union of them. For computing thisunionunion, the data type, such as Integer, Boolean, Set, or the Undef data type, plays a role. The details of the algorithm for combining permissions is described in Section 10. The resulting union effectively represents a "mask"--- it defines what information is exposed to the WR. This mask is applied to the actual location or presence data for the PT, and the datawhichthat is permitted by the mask is shown to the WR. If the WRrequestrequests a subset of information only (such as city-levelcivilcivic location data only, instead of the fullcivilcivic location information), the information delivered to the WR MUST be the intersection of the permissions granted to the WR and the data requested by the WR.In accordance to this document, rulesRules are encoded in XML. To this end, Section 13 contains an XML schema defining the Common Policy Markup Language. This, however, is purely an exchange format between RM and PS. The format does not imply that the RM or the PS use this format internally, e.g., in matching a query with the policy rules. The rules are designed so that a PS can translate the rules into a relational database table, with each rule represented by one row in the database. The database representation is by no means mandatory; we will use it as a convenient and widely-understood example of an internal representation. The database model has the advantage that operations on rows have tightly defined meanings. In addition, it appears plausible that larger-scale implementations will employ a backend database to store and query rules, as they can then benefit from existing optimized indexing, access control,scalingscaling, and integrity constraint mechanisms. Smaller-scale implementations may well choose different implementations, e.g., a simple traversal of the set of rules. 6.1. Identification of Rules Each rule is equipped with a parameter that identifies the rule. This rule identifier is an opaque token chosen by the RM. A RM MUST NOT use the same identifier for two rules that are available to the PS at the same time for a given PT. If more than one RM modifies the same rulesetset, then it needs to be ensured that a unique identifier is chosen for each rule. A RM can accomplish this goal by retrieving the already specifiedrulesetrule set andto choosechoosing a new identifier for a rule that is different from the existing rule set. 6.2. Extensions The policy framework defined in this document is meant to be extensible towards specific application domains. Such an extension is accomplished by defining conditions,actionsactions, and transformations that are specific to the desired application domain. Each extension MUST define its own namespace. Extensions cannot change the schema defined in this document, and this schema is not expected to changeexcepting aexcept via revision to thisspecification, and thatspecification. Therefore, no versioning procedures for this schema or namespace aretherforeprovided. 7. Conditions The access to data items needs to be matched with the rule set stored at the PS. Each instance of a request has different attributes (e.g., the identity of the requestor) that are used for authorization. A rule in a rule set might have a number of conditions that need to be met before executing the remaining parts of a rule (i.e., actions and transformations). Details about rule matching are described in Section 10. This document specifies only a few conditions (i.e., identity, sphere, and validity). Further condition elements can be added via extensions to this document. If a child element of the <conditions> element is in a namespace that is not known or not supported, then this child element evaluates to FALSE. As noted in Section 5, conditions are matched on equality or "greater than" style comparisons, rather than regular expressions. Equality is determined according to the rules for the data type associated with the element in the schema given in Section 13, unless explicit comparison steps are included in this document. For xs:anyURI types, readers may wish to consult [2] for its discussion xs:anyURI, as well as the text in Section 13. 7.1. Identity Condition 7.1.1. Overview The identity condition restricts matching of a rule either to a single entity or a group ofentitites.entities. Only authenticated entities can be matched; acceptable means of authentication are defined in protocol-specific documents. If the <identity> element is absent,or it is present but is empty (meaning that there are no child elements),identities are not considered, and thus, other conditions in the rule apply to any user, authenticated or not. The <identity> condition is considered TRUE if any of its child elements (e.g., the <one/> and the <many/> elements defined in this document) evaluate to TRUE, i.e., the results of the individual child element are combined using a logical OR. If a child element of the <identity> element is in a namespace that is not known or not supported,it can be ignored.then this child element evaluates to FALSE. 7.1.2. Matching One Entity The <one> element matches the authenticated identity (as contained in the 'id' attribute) of exactly one entity or user. For considerations regarding the 'id'attributeattribute, refer to Section 7.2. An example is shown below: <?xml version="1.0" encoding="UTF-8"?> <ruleset xmlns="urn:ietf:params:xml:ns:common-policy"> <rule id="f3g44r1"> <conditions> <identity> <one id="sip:alice@example.com"/> <one id="tel:+1-212-555-1234" /> <one id="mailto:bob@example.net" /> </identity> </conditions> <actions/> <transformations/> </rule> </ruleset> This example matches if the authenticated identity of the WR is either sip:alice@example.com,tel:+1-212-555-1234tel:+1-212-555-1234, or mailto:bob@example.net. 7.1.3. Matching Multiple Entities The <many> element is a mechanism to perform authorization decisions based on the domain part of the authenticated identity. As such, it allowsto matchmatching a large and possibly unknown number of users within a domain. Furthermore, it is possible to include one or multiple <except> elements to exclude either individual users or users belonging to a specific domain. Excluding individual entities is implemented using a <except id="..."/> statement. The semantic of the 'id' attribute of the <except> element has the same meaning as the 'id' attribute of the <one> element (see Section 7.2). Excluding users belonging to a specific domain is implemented using the <except domain="..."/> element that excludes any user from the indicated domain. If multiple <except> elements are listed as child elements of the <many>elementelement, then the result of each <except> element is combined using a logical OR. Common policy MUST either use UTF-8 or UTF-16 to store domain names in the 'domain' attribute. Fornon-IDNs, lower-casenon-IDNs (Internationalized Domain Names), lowercase ASCII SHOULD be used. For the comparison operation between the value stored in the 'domain' attribute and the domain value provided via the using protocol (referred to as "protocol domainidentifier")identifier"), the following rules are applicable: 1. Translate percent-encoding for either string. 2. Convert both domain strings using thetoASCIIToASCII operation described in RFC 3490 [3]. 3. Compare the two domain strings for ASCII equality, for each label. If the string comparison for each label indicates equality, the comparison succeeds. Otherwise, the domains are not equal. If the conversion fails in step (2), the domains are not equal. 7.1.3.1. Matching Any Authenticated Identity The <many/> element without any child elements or attributes matches any authenticated user. The following example shows such a rule that matches any authenticated user: <?xml version="1.0" encoding="UTF-8"?> <ruleset xmlns="urn:ietf:params:xml:ns:common-policy"> <rule id="f3g44r5"> <conditions> <identity> <many/> </identity> </conditions> <actions/> <transformations/> </rule> </ruleset>The following rule, in comparison, would match any user, authenticated and unauthenticated: <?xml version="1.0" encoding="UTF-8"?> <ruleset xmlns="urn:ietf:params:xml:ns:common-policy"> <rule id="f3g44r5"> <conditions> <identity/> </conditions> <actions/> <transformations/> </rule> </ruleset>7.1.3.2. Matching Any Authenticated IdentityExceptingExcept Enumerated Domains/Identities The <many> element enclosing one or more <except domain="..."/> elements matches any user from any domain except those enumerated. The <except id="..."/> element excludes particular users. Thesemanticsemantics of the 'id' attribute of the <except> element is described in Section 7.2. The results of the child elements of the <many> element are combined using a logical OR. An example is shown below: <?xml version="1.0" encoding="UTF-8"?> <ruleset xmlns="urn:ietf:params:xml:ns:common-policy"> <rule id="f3g44r1"> <conditions> <sphere value="work"/> <identity> <many> <except domain="example.com"/> <except domain="example.org"/> <except id="sip:alice@bad.example.net"/> <except id="sip:bob@good.example.net"/> <except id="tel:+1-212-555-1234" /> <except id="sip:alice@example.com"/> </many> </identity> <validity> <from>2003-12-24T17:00:00+01:00</from> <until>2003-12-24T19:00:00+01:00</until> </validity> </conditions> <actions/> <transformations/> </rule> </ruleset> This example matches all users except any user in example.com, or any user in example.org or the particular users alice@bad.example.net,bob@good.example.netbob@good.example.net, and the user with the telephone number 'tel:+1-212-555-1234'. The last 'except' element is redundant since alice@example.com is already excluded through the first line. 7.1.3.3. Matching Any Authenticated IdentityWithinwithin a DomainExceptingExcept Enumerated Identities The <many> element with a 'domain' attribute and zero or more <except id="..."/> elements matches any authenticated user from the indicated domain except those explicitly enumerated. Thesemanticsemantics of the 'id' attribute of the <except> element is described in Section 7.2. It is nonsensical to have domains in the 'id' attribute that do not match the value of the 'domain' attribute in the enclosing <many> element. An example is shown below: <?xml version="1.0" encoding="UTF-8"?> <ruleset xmlns="urn:ietf:params:xml:ns:common-policy"> <rule id="f3g44r1"> <conditions> <identity> <many domain="example.com"> <except id="sip:alice@example.com"/> <except id="sip:bob@example.com"/> </many> </identity> </conditions> <actions/> <transformations/> </rule> </ruleset> This example matches any user within example.com (such as carol@example.com) exceptalice@examplealice@example.com and bob@example.com. 7.2. Single Entity The 'id' attribute used in the <one> and in the <except> element refers to a single entity. In the subsequenttexttext, we use the term'single-user' entity'single-user entity' as a placeholder for the <one> and the <except> element. The <except> element fulfills the purpose of excluding elements from the solution set. A single-user entity matches the authenticated identity (as contained in the 'id' attribute) of exactly one entity or user. If there is a match, the single-user entity is considered TRUE. Thesingle- usersingle-user entity MUST NOT contain a 'domain' attribute. The 'id' attribute contains an identity that MUST first be expressed as a URI. Applications using this framework must describe how the identities they are using can be expressed asaURIs. 7.3. Sphere The <sphere> element belongs to the group of condition elements. It can be used to indicate a state (e.g., 'work', 'home', 'meeting', 'travel') the PT is currently in. A sphere condition matches only if the PT is currently in the state indicated. The state may be conveyed by manual configuration or by some protocol. For example, RPID [10] provides the ability to inform the PS of its current sphere. The application domain needs to describe in more detail how the sphere state is determined. Switching from one sphere to another causes a switch between different modes of visibility. As aresultresult, different subsets of rules might be applicable. The content of the 'value' attribute of the <sphere> element MAY contain more than one token. The individual tokens MUST be separated by a blank character. A logical OR is used for the matching the tokens against the sphere settings of the PT. As an example, if thethecontent of the 'value' attribute in the sphere attribute contains two tokens 'work' and 'home' then this part of the rule matches if the sphere for a particular PT is either 'work' OR 'home'. To compare the content of the 'value' attribute in the <sphere> element with the stored state information about the PT's sphere setting acase insensitivecase-insensitive string comparison MUST be used for each individual token. There isnoneither a registry for these values nor alanguagelanguage- specific indication of the sphere content. As such, the tokens are treated as opaque strings. <?xml version="1.0" encoding="UTF-8"?> <ruleset xmlns="urn:ietf:params:xml:ns:common-policy"> <rule id="f3g44r2"> <conditions> <sphere value="work"/> <identity> <one id="sip:andrew@example.com"/> </identity> </conditions> <actions/> <transformations/> </rule> <rule id="y6y55r2"> <conditions> <sphere value="home"/> <identity> <one id="sip:allison@example.com"/> </identity> </conditions> <actions/> <transformations/> </rule> <rule id="z6y55r2"> <conditions> <identity> <one id="sip:john@doe.example.com"/> </identity> <sphere value="home work"/> </conditions> <actions/> <transformations/> </rule> </ruleset> The rule example above illustrates that the rule with the entity andrew@example.com matches if the sphere is been set to 'work'. In the secondrule withrule, the entity allison@example.com matches if the sphere is set to 'home'. The third rule also matches since thethevalue in the sphere element also contains the token 'home'. 7.4. Validity The <validity> element is the third condition element specified in this document. It expresses the rule validity period by two attributes, a starting andaan ending time. The validity condition is TRUE if the current time is greater than or equal to at least one <from> child, but less than the <until> child after it. This represents a logical OR operation across each <from> and <until> pair. Times are expressed in XML dateTime format. A rule maker might nothavealways have access to the PS to invalidate some ruleswhichthat grant permissions.HenceHence, this mechanism allowsto invalidateinvalidating granted permissions automatically without further interaction between the rule maker and the PS. The PS does not remove therulesrules; instead the rule maker has to clean them up. An example of a rule fragment is shown below: <?xml version="1.0" encoding="UTF-8"?> <ruleset xmlns="urn:ietf:params:xml:ns:common-policy"> <rule id="f3g44r3"> <conditions> <validity> <from>2003-08-15T10:20:00.000-05:00</from> <until>2003-09-15T10:20:00.000-05:00</until> </validity> </conditions> <actions/> <transformations/> </rule> </ruleset> The <validity> element MUST have the <from> and <until> subelements in pairs. Multiple <from> and <until> elements might appear in pairs (i.e., without nesting of <from> and <until> elements). Using multiple <validity> elements as subelements of the <conditions> element is not useful since all subelements of the <conditions> element are combined as a logical AND. 8. Actions While conditions are the 'if'-part of rules, actions and transformationsbuild the 'then'-part of them.form their 'then'-part. The actions and transformations parts of a rule determine which operations the PS MUST execute after having received from a WR a data access request that matches all conditions of this rule. Actions and transformations only permit certain operations; there is no 'deny' functionality. Transformations exclusively specify PS-side operations that lead to a modification of the data items requested by the WR. Regarding location data items, for instance, a transformation could force the PS to lower the precision of the location informationwhichthat is returned to the WR. Actions, on the other hand, specify all remaining types of operations the PS is obliged to execute, i.e., all operations that are not of transformation type. Actions are defined byapplication specificapplication-specific usages of this framework. The reader is referred to the corresponding extensions to see examples of such elements. 9. Transformations Two sub-parts follow the conditions part of a rule: transformations and actions. As defined in Section 8, transformations specify operations that the PS MUST execute and that modify the resultwhichthat is returned to the WR. This functionality is particularly helpful in reducing the granularity of information provided to the WR,asas, forexampleexample, required for location privacy. Transformations are defined byapplication specificapplication-specific usages of this framework. A simple transformation example is provided in Section 10. 10. Procedure for Combining Permissions 10.1. Introduction This section describesthe mechanismhow rules are selected and how actions and permissions are determined. When a PS receives a request for access toevaluateprivacy-sensitive data, thefinal result of a rule evaluation. The resultrequest isreflectedmatched against the rule set. A rule matches if all conditions contained as child elements in theaction and transformation part<conditions> element of arule. This procedurerule evaluate to TRUE. Each type of condition defines when it issometimes referred as conflict resolution. We use the following terminology (which in parts has already been introduced in previous sections): The term 'permission' stands for an action or a transformation. The notion 'attribute' terms a condition, an action, or a transformation. An attribute has a name, and a certain data type. A value may be assigned to an attribute or it may be undefined, in case it does not have a value associated with the attribute. For example, the name of the <sphere> attribute discussed in Section 7 is 'sphere', its data type is 'string', and its value may be set to 'home'. To evaluate a condition means to associate either TRUE or FALSE to the condition. Please note that the <identity> element is a condition whereas the <id> element is a parameter of that condition. A rule matches if all conditions contained inTRUE. All rules where the conditionspart of a rule evaluate to TRUE. Whenmatch thePS receives arequestfor access to privacy-sensitive data then it needs to be matched against aform the matching rule set. Theconditions part of each individual rule is evaluated and as a result one or more rules might match. If only a single rule matches then the result is determined by executing the actions and the transformations part following the conditions part of a rule. However, it can also bepermissions in thecase that two or morematchingrules contain a permission of the same name (e.g., two rules contain a permission named 'precision of geospatial location information'), but do not specify the same value for that permission (e.g., the tworulemight specify values of '10 km' and '200 km', respectively, for the permission named 'precision of geospatial location information'). This section describes the procedure for combining permissions in such cases. 10.2. Algorithm The combining rulesset aresimple and depend on the data types of the values of permissions: Let P becombined using apolicy. Let M be the subset of P consistingset of combining rulesr in P that match with respect to a given request. Let n be a name of a permission contained in a rule r(CRs) described inM, and let M(n) be the subset of M consistingSection 10.2. 10.2. Combining Rules (CRs) Each type ofrules r in M that have apermissionof name n. For each rule r in M(n), let v(r,n) and d(r,n) be the value and the data type, respectively, of the attribute of r with name n. Finally, let V(n) be theis combinedvalueacross all matching rules. Each type ofall the permissions values v(r,n), r in M(n).action or transformation is combined separately and independently. The combining rulesthat lead to the resulting value V(n) aregenerate a combined permission. The combining rules depend only on thefollowing: CR 1: If d(r,n)=Boolean for all r in M(n), then V(n) is given as follows:data type of permission. Ifthere isar in M(n) with v(r,n)=TRUE, then V(n)=TRUE. Otherwise, V(n)=FALSE. CR 2: If d(r,n)=Integer for all rparticular permission type has no value inM(n), then V(n) is given as follows: If v(r,n)=undefineda rule, it assumes the lowest possible value forall r in M(n), then V(n) is not specified by this specification. Otherwise, V(n)=max{v(r,n) | r in M(n)}. CR 3: If d(r,n)=Setthat permission forall r in M(n), then V(n)the purpose of computing the combined permission. That value is givenas follows: V(n)=union of all v(r,n),by theunion todata type for booleans (FALSE) and sets (empty set), and MUST becomputed over all r in M(n) with v(r,n)!=undefined. The combining operation will result indefined by any extension to thelargest valueCommon Policy foran Integral type,other data types. For boolean permissions, theOR operation for boolean,resulting permission is TRUE if andunion for set. Asonly if at least one permission in the matching rule set has aresult, applications should define values such that, for integers,value of TRUE and FALSE otherwise. For integer, real-valued and date-time permissions, thelowestresulting permission is the maximum valuecorresponds toacross themost privacy, for booleans, false corresponds topermission values in themost privacy, and formatching set of rules. For sets, it is theempty set corresponds tounion of values across themost privacy.permissions in the matching rule set. 10.3. Example In the following example we illustrate the process of combining permissions. We will consider three conditions for our purpose, namely those of nameidentity,identity (WR-ID), sphere, andvalidity.validity (from,until). The ID column is used as a rule identifier. For editorial reasonsthe rule set in this example is represented in a table. Furthermore,we omit the domain part of theidentity of the WR is omitted. For actions weWR's identity. We use twopermissions with namesactions in our example, namely X and Y. The values of X and Y are of data types Boolean and Integer, respectively.Permission X might, for example, represent the <sub-handling> action. For transformations we use the attribute with the name Z whose valueThe transformation, referred to as Z, uses values that can be set either to'+'(or 1),'+' (or 3), 'o' (or 2) or '-' (or3).1). Permission Z allows us to show the granularity reduction whereby a value of '+' shows the corresponding informationunrestrictedunrestricted, and '-' shows nothing. This permission might be related to location information or other presence attributes like mood.InternallyInternally, we use the data type Integer for computing the permission of this attribute. The label 'NULL' in the table indicates that no value is available for a particular cell. Conditions Actions/Transformations +---------------------------------+---------------------+ | Id WR-ID sphere from until | X Y Z | +---------------------------------+---------------------+ | 1 bob home A1 A2 | TRUE 10 o | | 2 alice work A1 A2 | FALSE 5 + | | 3 bob work A1 A2 | TRUE 3 - | | 4 tom work A1 A2 | TRUE 5 + | | 5 bob work A1 A3 |undefNULL 12 o | | 6 bob work B1 B2 | FALSE 10 - | +---------------------------------+---------------------+ Again for editorial reasons, we use the following abbreviations for the two <validity> attributes 'from' and 'until': A1=2003-12-24T17:00:00+01:00 A2=2003-12-24T21:00:00+01:00 A3=2003-12-24T23:30:00+01:00 B1=2003-12-22T17:00:00+01:00 B2=2003-12-23T17:00:00+01:00 Note that B1 < B2 < A1 < A2 < A3. The entity 'bob' acts as a WR and requests data items. Thepolicy Prule set consists of the six rules shown in the table and identified by the values 1 to 6 in the 'Id' column. The PS receives the query at2003- 12-24T17:15:00+01:002003-12-24T17:15:00+01:00, which falls between A1 and A2.TheIn our example, we assume that the sphere value of theattribute with name 'sphere' indicating the state thePT is currentlyin isset to 'work'. As a first step, it is necessary to determine which rules fire by evaluating the conditions part of each of them. Rule 1 does not match since the sphere condition does not match. Rule 2 does not match as the identity of the WR (here 'alice') does not equal 'bob'. Rule 3 matches since all conditions evaluate to TRUE. Rule 4 does not match as the identity of the WR (here 'tom') does not equal 'bob'. Rule 5 matches. Rule 6 does not match since the rule is not valid anymore.Therefore, the set M of matching rules consists of theOnly rules 3 and5. These5 fire. We use the actions and transformations part of these two rulesare usedtocomputedetermine the combinedpermission V(X), V(Y), and V(Z) for each of the permissions X, Y, and Z:permission, as shown below. Actions/Transformations +-----+-----------------------+ | Id | X Y Z | +-----+-----------------------+ | 3 | TRUE 3 - | | 5 |undefNULL 12 o | +-----+-----------------------+The results of the permission combining algorithmEach column isshown below.treated independently. The combined valueV(X) regarding the permission with nameof Xequalsis set to TRUE since the NULL value equals FALSE according to thefirst combining rule listed above. Thedescription in Section 10.2. For the column with the name Y, we apply the maximum of 3 and12 is12, so thatV(Y)=12. Fortheattribute Z in this examplecombined value of Y is 12. For column Z, we again compute the maximumbetweenof 'o' and '-' (i.e.,between2 and3)1) which is 'o' (2). The combined permission for all three columns is'-'.therefore: Actions/Transformations+-----+-----------------------+ | Id+-----------------------+ | X Y Z |+-----+-----------------------+ | 5+-----------------------+ | TRUE 12-o |+-----+-----------------------++-----------------------+ 11. Meta Policies Meta policies authorize arulemakerrule maker to insert,updateupdate, or delete a particular rule or an entire rule set. Some authorization policies are required to prevent unauthorized modification of rule sets. Meta policies are outside the scope of this document. A simple implementation could restrict access to the rule set only to the PT but more sophisticated mechanisms could be useful. As an example of suchpoliciespolicies, one could think of parents configuring the policies for their children. 12. Example This section gives an example of an XML document valid with respect to the XML schema defined in Section 13. Semantically richer examples can be found in documentswhichthat extend this schema withapplication domain specificapplication-domain-specific data (e.g., location or presence information). Below a rule is shown with a condition that matches for a given authenticated identity (bob@example.com) and within a given time period. Additionally, the rule matches only if the target has set its sphere to 'work'. <?xml version="1.0" encoding="UTF-8"?> <ruleset xmlns="urn:ietf:params:xml:ns:common-policy"> <rule id="f3g44r1"> <conditions> <identity> <one id="sip:bob@example.com"/> </identity> <sphere value="work"/> <validity> <from>2003-12-24T17:00:00+01:00</from> <until>2003-12-24T19:00:00+01:00</until> </validity> </conditions> <actions/> <transformations/> </rule> </ruleset> 13. XML Schema Definition This section provides the XML schema definition for the common policy markup language described in this document. <?xml version="1.0" encoding="UTF-8"?> <xs:schema targetNamespace="urn:ietf:params:xml:ns:common-policy" xmlns:cp="urn:ietf:params:xml:ns:common-policy" xmlns:xs="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified" attributeFormDefault="unqualified"> <!-- /ruleset --> <xs:element name="ruleset"> <xs:complexType> <xs:complexContent> <xs:restriction base="xs:anyType"> <xs:sequence> <xs:element name="rule" type="cp:ruleType" minOccurs="0" maxOccurs="unbounded"/> </xs:sequence> </xs:restriction> </xs:complexContent> </xs:complexType> </xs:element> <!-- /ruleset/rule --> <xs:complexType name="ruleType"> <xs:complexContent> <xs:restriction base="xs:anyType"> <xs:sequence> <xs:element name="conditions" type="cp:conditionsType" minOccurs="0"/> <xs:element name="actions" type="cp:extensibleType" minOccurs="0"/> <xs:element name="transformations" type="cp:extensibleType" minOccurs="0"/> </xs:sequence> <xs:attribute name="id" type="xs:ID" use="required"/> </xs:restriction> </xs:complexContent> </xs:complexType> <!-- //rule/conditions --> <xs:complexType name="conditionsType"> <xs:complexContent> <xs:restriction base="xs:anyType"> <xs:choice maxOccurs="unbounded"> <xs:element name="identity" type="cp:identityType" minOccurs="0"/> <xs:element name="sphere" type="cp:sphereType" minOccurs="0"/> <xs:element name="validity" type="cp:validityType" minOccurs="0"/> <xs:any namespace="##other" processContents="lax" minOccurs="0" maxOccurs="unbounded"/> </xs:choice> </xs:restriction> </xs:complexContent> </xs:complexType> <!-- //conditions/identity --> <xs:complexType name="identityType"> <xs:complexContent> <xs:restriction base="xs:anyType"> <xs:choiceminOccurs="0"minOccurs="1" maxOccurs="unbounded"> <xs:element name="one" type="cp:oneType"/> <xs:element name="many" type="cp:manyType"/> <xs:any namespace="##other" processContents="lax"/> </xs:choice> </xs:restriction> </xs:complexContent> </xs:complexType> <!-- //identity/one --> <xs:complexType name="oneType"> <xs:complexContent> <xs:restriction base="xs:anyType"> <xs:sequence> <xs:any namespace="##other" minOccurs="0" processContents="lax"/> </xs:sequence> <xs:attribute name="id" type="xs:anyURI" use="required"/> </xs:restriction> </xs:complexContent> </xs:complexType> <!-- //identity/many --> <xs:complexType name="manyType"> <xs:complexContent> <xs:restriction base="xs:anyType"> <xs:choice minOccurs="0" maxOccurs="unbounded"> <xs:element name="except" type="cp:exceptType"/> <xs:any namespace="##other" minOccurs="0" processContents="lax"/> </xs:choice> <xs:attribute name="domain" use="optional" type="xs:string"/> </xs:restriction> </xs:complexContent> </xs:complexType> <!-- //many/except --> <xs:complexType name="exceptType"> <xs:attribute name="domain" type="xs:string" use="optional"/> <xs:attribute name="id" type="xs:anyURI" use="optional"/> </xs:complexType> <!-- //conditions/sphere --> <xs:complexType name="sphereType"> <xs:complexContent> <xs:restriction base="xs:anyType"> <xs:attribute name="value" type="xs:string" use="required"/> </xs:restriction> </xs:complexContent> </xs:complexType> <!-- //conditions/validity --> <xs:complexType name="validityType"> <xs:complexContent> <xs:restriction base="xs:anyType"> <xs:sequenceminOccurs="0"minOccurs="1" maxOccurs="unbounded"> <xs:element name="from" type="xs:dateTime"/> <xs:element name="until" type="xs:dateTime"/> </xs:sequence> </xs:restriction> </xs:complexContent> </xs:complexType> <!-- //rule/actions or //rule/transformations --> <xs:complexType name="extensibleType"> <xs:complexContent> <xs:restriction base="xs:anyType"> <xs:sequence> <xs:any namespace="##other" processContents="lax" minOccurs="0" maxOccurs="unbounded"/> </xs:sequence> </xs:restriction> </xs:complexContent> </xs:complexType> </xs:schema> 14. Security Considerations This document describes a framework for policies. This framework is intended to be enhanced elsewheretowards application domain specificby application-domain-specific data. Security considerations are to a great extentapplication dataapplication-data dependent, and therefore need to be covered by documents that extend the framework defined in this specification. However, new action and transformation permissions along with their allowed values must be defined in a way so that the usage of the permissions combining rules of Section 10 does not lower the level of privacy protection. See Section 10 for more details on this privacy issue. 15. IANA Considerations This section registers a new XML namespace, a new XMLschemaschema, and a newMIME-type.MIME type. This section registers a new XML namespace per the procedures in [4]. 15.1. Common Policy Namespace Registration URI: urn:ietf:params:xml:ns:common-policy Registrant Contact: IETFGeopriv Working Group,GEOPRIV working group, Henning Schulzrinne (hgs+geopriv@cs.columbia.edu). XML: BEGIN <?xml version="1.0"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN" "http://www.w3.org/TR/xhtml-basic/xhtml-basic10.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="content-type" content="text/html;charset=iso-8859-1"/> <title>Common Policy Namespace</title> </head> <body> <h1>Namespace for Common Authorization Policies</h1> <h2>urn:ietf:params:xml:ns:common-policy</h2> <p>See <ahref="[URL of published RFC]">RFCXXXX [NOTE TO IANA/RFC-EDITOR: Please replace XXXX with thehref="ftp://ftp.rfc-editor.org/in-notes/rfc4745.txt"> RFCnumber of this specification.]</a>.</p>4745</a>.</p> </body> </html> END 15.2. Content-typeregistrationRegistration for 'application/auth-policy+xml' This specification requests the registration of a new MIME type according to the procedures of RFC 4288 [5] and guidelines in RFC 3023 [6]. MIME media type name: application MIME subtype name: auth-policy+xml Mandatory parameters: none Optional parameters: charset Indicates the character encoding of enclosed XML. Encoding considerations: Uses XML, which can employ 8-bit characters, depending on the character encoding used. See RFC 3023 [6], Section 3.2. Security considerations: This content type is designed to carry authorization policies. Appropriate precautions should be adopted to limit disclosure of this information. Please refer to Section 14 ofRFCXXXX [NOTE TO IANA/RFC-EDITOR: Please replace XXXX with theRFCnumber of this specification.]4745 and to the security considerations described in Section 10 of RFC 3023 [6] for more information. Interoperability considerations: None Published specification:RFCXXXX [NOTE TO IANA/RFC-EDITOR: Please replace XXXX with theRFCnumber of this specification.] this document4745 Applications which use this media type: Presence- and location-based systems Additional information: Magic Number: None File Extension: .apxml Macintosh file type code: 'TEXT' Personal and email address for further information: Hannes Tschofenig, Hannes.Tschofenig@siemens.com Intended usage: LIMITED USE Author: This specification is a work item of the IETF GEOPRIV working group, with mailing list address <geopriv@ietf.org>. Change controller: The IESG <iesg@ietf.org> 15.3. Common Policy Schema Registration URI: urn:ietf:params:xml:schema:common-policy Registrant Contact: IETFGeopriv Working Group,GEOPRIV working group, Henning Schulzrinne (hgs+geopriv@cs.columbia.edu). XML: The XML schema to be registered is contained in Section 13. Its first line is <?xml version="1.0" encoding="UTF-8"?> and its last line is </xs:schema> 16. References 16.1. Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [2] Duerst, M. and M. Suignard, "Internationalized Resource Identifiers (IRIs)", RFC 3987, January 2005. [3] Faltstrom, P., Hoffman, P., and A. Costello, "Internationalizing Domain Names in Applications (IDNA)", RFC 3490, March 2003. [4] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, January 2004. [5] Freed, N. and J. Klensin, "Media Type Specifications and Registration Procedures", BCP 13, RFC 4288, December 2005. [6] Murata, M., St. Laurent, S., and D. Kohn, "XML Media Types", RFC 3023, January 2001. 16.2. Informative References [7] Rosenberg, J., "Presence Authorization Rules",draft-ietf-simple-presence-rules-07 (workWork inprogress),Progress, June 2006. [8] Schulzrinne, H., Tschofenig, H., Morris, J., Cuellar, J., and J. Polk, "A Document Format for Expressing Privacy Preferences for Location Information",draft-ietf-geopriv-policy-08 (workWork inprogress),Progress, February 2006. [9] Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and J. Polk, "Geopriv Requirements", RFC 3693, February 2004. [10] Schulzrinne, H., Gurbani, V., Kyzivat, P., and J. Rosenberg, "RPID: Rich Presence Extensions to the Presence Information Data Format (PIDF)", RFC 4480, July 2006. Appendix A. Contributors We would like to thank Christian Guenther for his help with initial versions of this document. Appendix B. Acknowledgments This document is partially based on the discussions within the IETF GEOPRIV working group. Discussions at the Geopriv Interim Meeting 2003 in Washington, D.C., helped the working group to make progress on the authorization policies based on the discussions among the participants. We particularly want to thank Allison Mankin <mankin@psg.com>, Randall Gellens <rg+ietf@qualcomm.com>, Andrew Newton <anewton@ecotroph.net>, Ted Hardie<hardie@qualcomm.com><hardie@qualcomm.com>, and Jon Peterson <jon.peterson@neustar.biz> for discussing a number of details with us. They helped us to improve the quality of this document. Allison,TedTed, and Andrew also helped us to make good progress with the internationalization support of the identifier/ domain attributes. Furthermore, we would like to thank the IETF SIMPLE working group for their discussions of J. Rosenberg's draft on presence authorization policies. We would also like to thank Stefan Berg, Murugaraj Shanmugam, Christian Schmidt, Martin Thomson, Markus Isomaki, Aki Niemi, Eva MariaLeppanenLeppanen, Josip Matanovic, and Mark Baker for their comments. Martin Thomson helped us with the XML schema. Mark Baker provided a review of the media type. Scott Brim provided a review on behalf of the General Area Review Team. Authors' Addresses Henning Schulzrinne Columbia University Department of Computer Science 450 Computer Science Building New York, NY 10027 USA Phone: +1 212 939 7042Email:EMail: schulzrinne@cs.columbia.edu URI: http://www.cs.columbia.edu/~hgs Hannes Tschofenig Siemens Networks GmbH & Co KG Otto-Hahn-Ring 6 Munich, Bavaria 81739 GermanyEmail:EMail: Hannes.Tschofenig@siemens.com URI: http://www.tschofenig.com John B. Morris, Jr. Center for Democracy and Technology 1634 I Street NW, Suite 1100 Washington, DC 20006 USAEmail:EMail: jmorris@cdt.org URI: http://www.cdt.org Jorge R. Cuellar Siemens Otto-Hahn-Ring 6 Munich, Bavaria 81739 GermanyEmail:EMail: Jorge.Cuellar@siemens.com James Polk Cisco 2200 East President George Bush Turnpike Richardson, Texas 75082 USAEmail:EMail: jmpolk@cisco.com Jonathan Rosenberg Cisco Systems 600 Lanidex Plaza Parsippany, New York 07054 USAEmail:EMail: jdrosen@cisco.com URI: http://www.jdrosen.net Full Copyright Statement Copyright (C) TheInternet Society (2006).IETF Trust (2007). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. 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