Documentation/Maemo 5 Developer Guide/Architecture/RTCOM

The RTCom domain provides both services and applications for real time Internet communications, such as Voice Over IP / Video calls and Instant Messaging, and also cellular/CS communications on Maemo platform. It also provides and distributes presence information within the system.

The architecture consists of a few major components; connection managers which abstract implementation details of different protocols to a common API, mission control to handle transient events and enforce system policies, and user interfaces to present information to the user. There is also a streaming server to handle actual media streaming communications. It is not conceptually a separate architectural element of the framework, but more like one UI implementation. Farsight interface is used to manage media pipelines.

Contents

[edit] System decomposition view

The diagram below shows the entities of the RTCOM subsystem, dependencies between them, provided interfaces and required external interfaces. The client applications are shown as packages without the fill-color. Different UI components (Messaging, Call, Log Viewer, Desktop Elements, Control Panel Applets) provide user interface layer to the system.

On intermediate layer, there’s a Mission Control package, which handle transient events and enforce system policies, providing application logic services, and libtelepathy-glib component providing GObject-style access to the Telepathy D-Bus interfaces.

On lowest level, there are Streaming Engine to handle actual media streaming communications, and Connection managers that abstract implementation details of different protocols to a common API. The interface is modular and platform includes Jabber (instant messaging) and SIP (voice and video calls).

The Telepathy framework is used to handle real time communication related signaling and abstracting all protocol dependencies to a single D-Bus interface.

Centralized addressbook is provided by the Contacts subsystem and used by the RTcom subsystem for all contact information storage and lookup purposes and it also stores transient contacts/states.

[edit] RTCOM framework

In Fremantle, RTCom framework provides the following functionality:

  • Support for comprehensive logging
  • SSO related components
  • Support for heartbeat
  • Device presence profiles
  • Support for BT HFP
  • Location support for presence

[edit] telepathy-glib

Purpose
Provides GObject abstraction of Telepathy D-Bus interfaces
Source packages
telepathy-glib, librtcom-telepathy-glib
Licenses
LGPL and Nokia Proprietary
Interfaces used
libglib, libdbus, libdbus-glib
Interfaces provided
libtelepathy-glib, librtcom-telepathy-glib

[edit] telepathy-mission-control

Purpose
Provides a way for “end user” applications to abstract some of the details of connection managers to provide a simple way to manipulate a bunch of connection managers at once and remove the need to have in each program the account definitions and credentials.
Source packages
telepathy-glib, librtcom-telepathy-glib
Licenses
LGPL and Nokia Proprietary
Interfaces used
libglib, libdbus, libdbus-glib
Interfaces provided
libtelepathy-glib, librtcom-telepathy-glib

[edit] osso-mission-control

Purpose
Mission control filters
Source packages
telepathy-mission-control
Licenses
Nokia
Interfaces used
libmissioncontrol, libosso, libconic, libebook, libhildon1 (libhildon-desktop), mce, libxml2, librtcom-eventlogger, librtcom-eventlogger-plugins, libsignon-glib
Interfaces provided
None

[edit] osso-accounts

Purpose
Provides a set of libraries, UIs and applets for account management.
Source packages
osso-accounts, osso-accounts-plugin-nokia-chat
Licenses
Nokia
Interfaces used
libgtk2, libhildon1 (libhildon1, libhildonfm2, hildon-control-panel, libhildonmime, libhildonhelp), libosso-abook, libglade2, libconic, libmcclient
Interfaces provided
libaccounts, libaccounts-glade

[edit] rtcom-eventlogger

Purpose
Provides general purpose event log database system.
Source packages
rtcom-eventlogger
Licenses
Nokia
Interfaces used
libglib, libsqlite3, libdbus
Interfaces provided
librtcom-eventlogger

[edit] rtcom-eventlogger-plugins

Purpose
Provides plugins for the event logging system.
Source packages
rtcom-eventlogger-plugins
Licenses
Nokia
Interfaces used
libglib, libsqlite3, librtcom-eventlogger
Interfaces provided
None

[edit] Connection Managers

Connection managers can be thought of as a kind of protocol plugins of the system. They conform to Telepathy D-Bus interface specification and provide D-Bus interface abstraction of some protocol. Each connection manager usually provides support for one protocol. The provided interfaces depend on the capabilities of the connection manager and protocol.

Connection managers only signaling protocols. In case of a media streaming session, SDP or similar negotiation signaling is done in Connection Manager using the signaling protocol, but actual payload streaming is handled by Streaming Engine (Eg: telepathy-stream-engine).

[edit] Functionalities provided

  • Support for Skype integrated into Telepathy framework

[edit] telepathy-ring

Purpose
Connection manager for cellular calls and SMS messaging
Source packages
telepathy-ring
Licenses
Nokia
Interfaces used
libglib, libdbus, libdbus-glib, libtelepathy-glib
Interfaces provided
None

[edit] sofia-sip

Purpose
SIP-stack implementation
Source packages
sofia-sip
Licenses
LGPL
Interfaces used
libglib, libssl
Interfaces provided
libsofia-sip-ua, libsofia-sip-ua-glib

[edit] telepathy-sofiasip

Purpose
SIP connection manager
Source packages
telepathy-sofiasip
Licenses
LGPL
Interfaces used
libglib, libdbus, libdbus-glib, libsofia-sip-ua, libsofia-sip-ua-glib, libtelepathy-glib, libssl
Interfaces provided
None

[edit] loudmouth

Purpose
XMPP-stack implementation
Source packages
loudmouth
Licenses
LGPL
Interfaces used
libglib, libssl, libcertman (libcst)
Interfaces provided
libloudmouth

[edit] telepathy-gabble

Purpose
XMPP connection manager
Source packages
telepathy-gabble
Licenses
LGPL
Interfaces used
libglib, libssl
Interfaces provided
libglib, libdbus, libdbus-glib, libloudmouth, libtelepathy-glib

[edit] Streaming Engines

Media engines handle media streaming needs for multimedia communication methods like voice and video conversation. Generic telepathy-stream-engine provides voice and video streaming capabilities over RTP protocol. If there is a need for other kind of media streaming for some connection manager, it might be reasonable to provide separate media engine for that purpose.

Independent of possible other uses, libjingle is used to provide NAT traversal using STUN, GTalk relay and ICE technologies for the GTalk service. libnice provides fully standards compliant ICE implementation.

[edit] Functionalities provided

  • Support for fully standards compliant ICE through libnice.
  • Support for H.264
  • Support for BT HFP.
  • Support for Skype in Telepathy framework.

[edit] gst-plugins-farsight

Purpose
GStreamer plugins specific to Farsight.
Source packages
gst-plugins-farsight
Licenses
LGPL
Interfaces used
libglib, gstreamer (libgstreamer-pligins-base), libjingle, libgonf2
Interfaces provided
None

[edit] farsight2

Purpose
The Farsight project is an effort to create a framework to deal with all known audio/video conferencing protocols. On one side it offers a generic API that makes it possible to write plugins for different streaming protocols, on the other side it offers an API for clients to use those plugins. This package provides the core Farsight 2 library.
Source packages
farsight2
Licenses
LGPL
Interfaces used
libglib, gstreamer (libgstreamer-plugins-base, libgstreamer-plugins-good, libgstreamer-plugins-bad), libnice, libnice-gstreamer, gupnp
Interfaces provided
libgstfarsight

[edit] telepathy-farsight

Purpose
Glue betweeen Telepathy and Farsight2
Source packages
telepathy-farsight
Licenses
LGPL
Interfaces used
libglib, libdbus (libdbus, libdbus-glib), libgstfarsight, libtelepathy-glib
Interfaces provided
libtelepathy-farsight

[edit] libnice

Purpose
ICE NAT-traversal implementation
Source packages
libnice
Licenses
MPL / LGPL
Interfaces used
libglib, gstreamer (libgstreamer, libgstreamer-plugins-base)
Interfaces provided
libnice, libnice-gstreamer

[edit] telepathy-stream-engine

Purpose
Media streaming engine for Telepathy, mostly used for standard RTP-over-UDP streaming.
Source packages
telepathy-stream-engine
Licenses
LGPL
Interfaces used
libglib, libdbus (libdbus, libdbus-glib), libgstfarsight, gstreamer (libgstreamer-plugins-base), libtelepathy-farsight, libgtk2

[edit] telepathy-glib

Telepathy Library’s role is to provide common GObject-based C-language API for applications. It wraps Telepathy D-Bus interfaces to GObjects and also provides some utility functions for accessing and enumerating D-Bus interfaces. It’s code is mostly autogenerated from D-Bus interface specification.

Purpose
C API for Telepathy D-Bus interfaces.
Responsibilties
Provides GObject based C-language API to the Telepathy D-Bus interfaces along with some utility functions.
Notes
Most of Telepathy’s functionality is distributed as D-Bus objects where the actual functionality doesn’t necessarily reside within any specific component, but as an abstract object in the D-Bus network.
License
LGPL
Interfaces used by libtelepathy-glib
Interface name License Dependency Description
Telepathy LGPL glib, D-Bus RTCom Interface

[edit] Mission Control

Communication system policies are usually dependent on application and environment, thus some method external to framework has to exist for handling those. Mission Control thus enforces communication system policies. It also handles configuration information storage, network connectivity from policy point of view and is thus responsible for starting and stopping connection managers and engines. While starting up connection managers and engines, it provides the configuration information.

In case of network side event like presence subscription or start of communication session, Mission Control handles these transient events based on system policy and possibly starts associated UI components. Misson Control employs plugin methods to provide possibility to add special event handlers called “mission control filters”. These plugins can provide special device or system dependent function handling.


Purpose
Enforces policies, handles startup/connectivity and transient events.
Responsibilities
Enforces system policies. Handles Connection Managers, Engines and UI startups. Also handles transient and network side events. Also responsible for connectivity management.
Packages
curlpp, osso-mission-control, osso-rtcom-oma, telepathy-mission-control
License
LGPL, Nokia Proprietary

[edit] User Interfaces

[edit] Messaging UI

Name
rtcom-messaging-ui
Purpose
Messaging application.
Source Packages
rtcom-messaging-ui
Licenses
Nokia
Interfaces Used
libglib, libosso, libgtk2, libhildon1 (libhildon1, libhildon-mime, libhildonfm2), libgconf2, libtelepathy-glib, librtcom-telepathy-glib, libmcclient, libosso-abook, libebook, mce, maemo-launcher, librtcom-eventlogger, librtcom-eventlogger-ui, librtcom-eventlogger-plugins, browser-neteal

Messaging UI is a user interface component for instant messaging sessions. It handles all kinds of non-media streaming communications like text chat.

[edit] Event logger

Name
rtcom-eventlogger-ui
Purpose
Event logger widgets.
Source Packages
rtcom-eventlogger-ui
Licenses
Nokia
Interfaces Used
libglib, libgtk, libdbus, librtcom-eventlogger, librtcom-eventlogger-plugins, libosso, libosso-abook, libhildon1, libmcclient
Interfaces Provided
librtcom-eventlogger-ui

Logger is a database engine built into a library for logging all kinds of events. It’s particularly powerful for logging messages (optionally with attachments), calls and network events.

[edit] Notification UI

Name
rtcom-notification-ui
Purpose
Notification UI, plugin for the Hildon Status Menu.
Source Packages
rtcom-notification-ui
Licenses
Nokia
Interfaces Used
libglib, libosso, libgtk2, libhildon1 (libhildon1, libhildondesktop1, libhildonmime), mce, libtelepathy-glib, libosso-abook, libebook, librtcom-telepathy-glib

This is a Hildon Status menu plugin for RTCom related notifications.

[edit] Presence UI

Name
rtcom-presence-ui
Purpose
Accounts presence UI.
Source Packages
rtcom-presence-ui
License
Nokia
Interfaces Used
libglib, libosso, libgtk2, libhildon1 (libhildon1, libhildondesktop1), libmcclient, maemo-launcher, liblocation, libnavigation, libcanberra, libosso-abook

This is the presence user interface.

[edit] Single-Sign-On (SSO)

SSO subsystem is a separate subsystem providing credential storage and a client library for applications. This way, user is not requested to login or enter credentials as he’s navigating between different service types within single service provider. In case of wide ticket-based system like OpenID, user can even use the same credential between different service providers as long as service provider accepts tickets from external providers.

Purpose
Provides Single-Sign-On functionality.
Responsibilities
Provides authentication services and tokens for applications.
Name
libsignon-glib
Purpose
GObject interface to SSO functionality.
Source Packages
signon
Licenses
Nokia
Interfaces Used
libglib, libxml2
Interfaces Provided
libsignon-glib


Name
libsignonui
Purpose
UI elements of the SSO functionality.
Source Packages
signon
Licenses
Nokia
Interfaces Used
libglib, libgtk2, libhildon1, libaccounts, libosso-rtcom-accounts, libsignon-glib
Interfaces Provided
libsignonui
Name
signond
Purpose
SSO daemon, handling credential storate and authentication.
Source Packages
signon
Licenses
Nokia
Interfaces Used
libglib, libxml2, libcurl (libcurl3-openssl), libssl (libcrypto)
Interfaces Provided
signond (ipc)

SSO-subsystem consists of server, here called “signond” and application libraries libsignon-glib and libsignonui. Server stores credentials in optionally encrypted database. It is running under different user id than applications. Application library accesses the storage over IPC mechanism.

[edit] Protocol Stack

Realtime communication framework connects to services using protocol plugins. Currently, XMPP/Jabber and SIP are the officially supported protocols. There’s also support for media extension of Jabber called Jingle. As described earlier, each of the protocol plugins create abstraction of some protocol to a common D-Bus protocol.

GoogleTalk uses Jingle protocol to handle voice streaming.

Standard Jabber communication always goes through persistent TCP connection to the server. SIP protocol uses either UDP or TCP protocol for signaling. UDP is older and established method, while TCP is more recommended nowadays, mainly due to some particular message size and NAT traversal problems associated with UDP use. Together with SIP, standard RTP is always used for the media.

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