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1. RLS (Resource List Server) Vaclav Kubart Iptel/Tekelec <> __________________________________________________________________ 1.1. Dependencies 1.2. RLS and XCAP 1.2.1. Used terms 1.2.2. Processing subscriptions 1.2.3. Global resource lists rls-services document URI Disadvantages 1.2.4. User's resource lists 1.2.5. Standard incompliances 1.3. Parameters 1.4. Functions Resource lists server is a server which allows subscriptions to lists of users. Its behaviour is defined in [rls] and [sip rls]. As described there, it uses XCAP server for storing data about lists of users. These data can be manipulated in any way by user's client software. 1.1. Dependencies Modules * tm * pa * dialog * optionaly database module (mysql, ...) Libraries * libcds (internal) * libxcap (internal) - XCAP queries * libpresence (internal) - used for internal subscriptions ta PA/presence_b2b 1.2. RLS and XCAP 1.2.1. Used terms RLS Resource List Server - server processing subscriptions to special URIs (RL-URIs) which represent more resources than only one like "normal URIs". RL-URI Resource list URI. URI which represents a list of resources instead of a single user. 1.2.2. Processing subscriptions Specification says that each time a SUBSCRIBE request to a RL-URI comes, RLS has to ask XCAP server for coresponding <service> in default rls-services document. The XCAP query in this case is for document like <xcap-root>/rls-services/global/index/~~/rls-services/service[@uri=%22< AOR>%22]. Returned <service> is processed according to specification then and the result of it is flat list of URIs to subscribe to. This processing has its weaknesses. * In case of such processing is one <service> element in rls-services needed for every user who wants to have his "buddies" stored on XCAP server. Such <service> will (for user's records) mostly point into his resource-lists document and thus another XCAP query for result list is needed. * Another problem is, that each user has to modify global rls-services document. This is security problem and there is no client software doing this itself. [Exists something?] These reasons lead to separation of resource lists into "global lists" and "users lists". Global lists are not stored/modified by regular users; they are managed by administrators and they are handled according the draft. Example of such lists may be "technical support", "human resources", ... Resource lists for users are stored only in their resource-lists documents and the <service> element in global rls-services document is ommited (it is "implicit"). In this case RLS reads directly user's resource-lists document instead of trying to find it in global rls-services document. 1.2.3. Global resource lists As said above, resources described in rls-services documents are global resources accessible by all users. No regular user should have acces rights to modify global rls-services document on XCAP server. rls-services document URI The construction of rls-services document URI is described in [rls]. Only in short: the AOR from SIP SUBSCRIBE request is combined with XCAP root given in configuration like this: <xcap-root>/rls-services/global/index/~~/rls-services/service[@uri=%22< AOR>%22]. This URI doesn't not specify namespaces as mentioned in definition, but this is due to problems with XCAP server used for tests (problems querying parts of documents with namespaces). Example 1. rls-services uri example Let us assume * xcap-root = http://localhost/xcap-root * AOR of SUBSCRIBE request = Resulting document describing the list will be get from URI: http://localhost/xcap-root/rls-services/global/index/~~/rls-services/se rvice[@uri=%22<>%22], which means the service element with uri parameter value stored in rls-services document named index. Example 2. rls-services document There is example rls-services document describing resources "", "" and "" which puts previous two into itself. This document should be stored on xcap server in file <xcap-root>/rls-services/global/index. <?xml version="1.0" encoding="UTF-8"?> <rls-services> <service uri=""> <list name="Our technical support"> <entry uri=""> <display-name>Smith</display-name> </entry> <entry uri=""> <display-name>Joe</display-name> </entry> <entry uri=""> <display-name>Agatha</display-name> </entry> </list> <packages> <package>presence</package> </packages> </service> <service uri=""> <list name="Human resources"> <entry uri=""> <display-name>Johny V</display-name> </entry> <entry uri=""> <display-name>Joe</display-name> </entry> </list> <packages> <package>presence</package> </packages> </service> <service uri=""> <list name="Employee resources"> <entry uri=""> <display-name>Technical support</display-name> </entry> <entry uri=""> <display-name>Human resources</display-name> </entry> </list> <packages> <package>presence</package> </packages> </service> </rls-services> Disadvantages Working with URIs presented in this section have one big disadvantage - it needs full XCAP server which is able to work with partial documents and able to process XPointer expressions in XCAP queries. Due to unavailability of free XCAP servers is there a possibility to use SER's RLS server in mode of reduced XCAP server needs (see RLS module parameters). If operating in this mode, RLS requests full rls-service document from uri <xcap-root>/rls-services/global/index, inspects it and finds requested resource list according to URI and AOR by itself. (Only if possible! There can't be links to partial documents in rls-services document.) 1.2.4. User's resource lists Opposite to global resource lists are resource lists of standalone users. As was told above, these lists are stored as resource-lists documents under user's directories. These resource-lists documents are accessed directly without searching for them in rls-services document - they behave like if they have implicit link there. Example 3. User's resource lists Let us assume * xcap root = http://localhost/xcap-root * user smith (sends SUBSCRIBE with smith@... in From URI) * Smith's UUID = smith The document below for user Smith can be stored on XCAP server in http://localhost/xcap-root/resource-lists/users/smith/resource-lists.xm l. It contains two resource lists: "default" and "contacts". <?xml version="1.0" encoding="UTF-8"?> <resource-lists xmlns="urn:ietf:params:xml:ns:resource-lists" > <list name="default"> <display-name>Buddy List</display-name> <entry uri=""> <display-name>Joe</display-name> </entry> <entry uri=""> <display-name>Jan</display-name> </entry> </list> <list name="contacts"> <display-name>Contact List</display-name> <entry uri=""> <display-name>Alois</display-name> </entry> </list> </resource-lists> 1.2.5. Standard incompliances SER's resource lists support is not finished yet, there are some standard incompliances now: * uri canonicalization not done yet according to definition * full status documents only 1.3. Parameters min_expiration (integer) Minimal subscription expiration timeout in seconds. If client supplies value, which is less than value of min_expiration, the server returns response "423 Interval too small" as described in [events]. Default value is 60. max_expiration (integer) Maximal subscription expiration timeout in seconds. If client supplies value, which is more than value of max_expiration, the server shortens this value to value of this variable as described in [events]. Default value is 7200. default_expiration (integer) Default subscription expiration timeout in seconds. If client doesn't supply subscription expiration timeout this value is used. Default value is 3761. auth (string) This variable specifies authorization type for list watchers. Value can be one of: none All watchers are always authorized. This is not recommended because it ignores user's wish. implicit In this case is implicit authorization done. This means, that for list URIs in the form "<username>-list@domain" is subscription allowed only for user with username <username>, rejected for others. If the URI is not in the form presented above, the subscription is marked as pending. Default value is empty. In this case "implict" authorization is used with an error message. reduce_xcap_needs (int) If set to 1 the module tries to do simplify XCAP queries - queries will be done for whole documents, not partial, thus the XCAP server may be simulated using standard web server. It has influence only on querying resource lists and it will work correctly only if there are no links to resource lists containg partial documents URIs (lists should be contained directly in main rls-services document). Default value is 0. db_mode (integer) If set to 1, RLS module stores all subscription data into database and reloads them on startup. Requires db_url to be set. Default value is 0. db_url (integer) Database connection URL. It has to be specified if db_mode is set. Default value is empty. Example 4. db_url settings ... modparam("rls", "db_mode", 1) modparam("rls", "db_url", "mysql://ser:heslo@") ... max_notifications_at_once Max. number of notifications sent within one timer tick (experimental). It might be used to reduce SER's machine load if there are lots of changes in presence status. Default value is 1000000. (Too high number which in praxis means unlimited.) timer_interval Interval in seconds when are processed internal notifications and sent NOTIFYs to subscribers. max_nesting_level Maximum number of nested lists. For example if set to 2, it it possible to use "list nested in list nested in root list". Default value is -1 what means "unlimited". It is possible to use this for speedup - if you know, that you will need only "flat" lists (no nested lists), you can set this to 0. In this case RLS doesn't try to query XCAP server for "possibly netsted list URIs" and directly creates subscription to URIs in list like if they are URIs of standalone users. expiration_timer_period Interval in seconds of timer which removes expired subscriptions. ignore_408_on_notify If set to 1 and 408 response to NOTIFY arrives, the dialog is NOT destroyed like in the case of other non-2xx responses. Use for testing only. Default value is 0. init_timer_delay Delay in seconds of timer which triggers loading data from database after startup. This is needed due to dependencies on other modules (pa/presence_b2b) - we need that these modules will be successfully initialised before reading data from DB and querying these modules. Default value is 3. 1.4. Functions handle_rls_subscription Handle subscription to resource list uri. Parameters: create_error_response (integer) If set to 0 error responses are not sent to the client. This may be useful, if used together with PA module. This function handles resource list subscription. XCAP document containing the list must be loaded before using one of query function (query_rls_services, query_resource_list). Example 5. handling subscription ... if (method=="SUBSCRIBE") { if (!t_newtran()) { sl_reply_error(); }; if (query_rls_services()) { handle_rls_subscription("1"); } else { # no such list exists -> process it with PA module handle_subscription("registrar"); } break; }; ... In this case for every incomming SUBSCRIBE request SER asks for "global resource list". If such list exists, the subscription is processed like resource list subscription. is_simple_rls_target Test uri according to given template. Parameters: template (string) Template to be compared with To URI. Function tries to compare username in To URI with given template. If there are different domains in To and From URIs, the function fails. There can be used "$uid" in template and it is replaced by value returned by get_from_uid. In the future should be this function replaced by AVP operations but I was not able to do it with them now... Example 6. handling subscription ... if (method=="SUBSCRIBE") { if (!t_newtran()) { sl_reply_error(); break; }; if (lookup_domain("From")) { if (lookup_user("From")) { if (is_simple_rls_target("$uid-list")) { # takes From UID and makes XCAP query # for user's list named "default" if (!query_resource_list("default")) { t_reply("500", "XCAP query error"); break; } handle_rls_subscription("1"); break; } } } } ... In this case if SUBSCRIBE request arrives and From is and To is, the function returns true and the subscription is handled like subscription to "user's resource list" (not "global") as written above. query_rls_services Get list from global rls-services document. Function loads "global resource list" from XCAP server. This list is then processed by RLS module using handle_rls_subscription. query_resource_list Get user's resource list. Parameters: list_name (string) Name of the requested list. If empty, it loads whole user's resource-lists document as one list. Function loads "user's resource list" from XCAP server. This list is then processed by RLS module using handle_rls_subscription. have_flat_list Test if a resource list is loaded. Function tests if a list was loaded using one of query functions (query_resource_list or query_rls_services) and returns 1 if yes and -1 otherwise. Bibliography Note There might be new versions of internet drafts and thus links to them my be obsolete. In such case try increment version in link or find the draft on IETF by name. XCAP [xcap] draft-ietf-simple-xcap-12.txt - XCAP specification. [xcap_diff] draft-ietf-simple-xcap-diff-01.txt - XCAP changes notifications format. [xcap_profiles] draft-ietf-sipping-config-framework-07.txt -XCAP user profiles. Presence [events] RFC 3265 - SIP Events. [presence] RFC 3856 - Presence Event package. [pidf] RFC 3863 - Presence Information Data Format. [rpid] RFC 4480 - Rich Presence Extensions to the Presence Information Data Format. [publish] RFC 3903 - Event state publication. [winfo] RFC 3857 - Watcher info event package. [winfo_doc] RFC 3858 - Data Format for watcher info. [reg] RFC 3680 - SIP Reg Events. Authorization [common auth] draft-ietf-geopriv-common-policy-05.txt. [presence auth] draft-ietf-simple-presence-rules-03.txt - presence authorization XML based data format and usage with XCAP. Resource lists [rls] draft-ietf-simple-xcap-list-usage-05.txt - XML formats for representing resource lists. [sip rls] draft-ietf-simple-event-list-07.txt - Event Notification Extension for Resource Lists.