kamailio/misc/obsolete/rls

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

1.2.3.1. rls-services document URI
1.2.3.2. 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 in default
rls-services document. The XCAP query in this case is for document like
/rls-services/global/index/~~/rls-services/service[@uri=%22<
AOR>%22]. Returned 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 element in rls-services
needed for every user who wants to have his "buddies" stored on
XCAP server. Such 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 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.

1.2.3.1. 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:

/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 = sip:[email protected]

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 [email protected]
stored in rls-services document named index.

Example 2. rls-services document

There is example rls-services document describing resources
"[email protected]", "[email protected]" and
"[email protected]" which puts previous two into itself. This
document should be stored on xcap server in file
/rls-services/global/index.






Smith


Joe


Agatha



presence






Johny V


Joe



presence






Technical support


Human resources



presence





1.2.3.2. 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 /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".

xmlns="urn:ietf:params:xml:ns:resource-lists"
>

Buddy List

Joe


Jan




Contact List

Alois





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 "-list@domain" is
subscription allowed only for user with 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:[email protected]:3306/ser")
...

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
[email protected] and To is [email protected], 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.