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eXpress Federation Architecture
Updated 9 Oct 2026

eXpress Federation Architecture

Corporate and public servers are united in the common eXpress federation:


eXpress Servers Federation

What is the eXpress Federation?

It's a network of regional and corporate eXpress servers. It includes all public regional (
RTS
) and corporate (
Lite
,
CTS
) servers and some enterprise servers (
ETS
,
eCTS
), which have it's own customized version of the app.

What Does the Federation Offer?

Within the federation, users of different organizations can:

  • Exchange messages and files
  • Schedule conferences and calls
  • Interact with users from other companies

Regional Transport Server, RTS

RTS

It is a public cloud server. In eXpress, contacts and RTS servers are marked with green icons.

For Administrators: Purpose & Features of RTS

Purpose of RTS

  • Global routing of messages between all members of the federation (both corporate and external users) in any apps;
  • Initial user registration on
    RTS
    ,
    Lite
    ,
    CTS
    (including working with SMS codes), and guest profiles;
  • Sending push notifications to eXpress client apps for
    RTS
    ,
    Lite
    ,
    CTS
    users.

Features of RTS

  • There are several such servers; they are located in Russia and are managed by the eXpress vendor.
  • You can register on
    RTS
    for free using a personal non-corporate account in eXpress. The app features for such an account are limited.

Who Administrates the RTS?

The server side is administered by eXpress support.

Corporate Transport Server, CTS

Lite
CTS
A corporate server is a server managed by an organization, for example, the one you work for. In eXpress,
CTS
contacts and servers are marked with blue icons.
  • Lite
    corporate server is a
    CTS
    corporate server with limited functionality.
  • A corporate server that follows
    ETS
    instead of
    RTS
    is called
    eCTS
    .
For Administrators: Purpose & Features of CTS/eCTS

Purpose of CTS/eCTS

  • Corporate user authentication
    Lite
    ,
    CTS
    /
    eCTS
    ; guest profiles (if configured);
  • Routing and storing files and messages of corporate users;
  • Corporate phonebook;
  • Direct interaction with other corporate servers (of this organization or a partner organization);
  • Other functions for corporate communications (conferences, bots, etc.).

Features of CTS

  • CTS
    provides basic messaging functions within an isolated, secure corporate network. To communicate with each other, employees of the organization need to register on the corporate server.
  • All
    CTS
    and
    Lite
    servers are connected to
    RTS
    directly and use it for registration and sending push notifications.
  • An organization may have several corporate
    CTS
    servers, and trusted connections (trusts) can be established between them. Users of one trust server can search for users of another. Traffic between trust servers goes directly, bypassing
    RTS
    .

Who Administrates the CTS?

The server side is administered by your organization's support, a partner, or paid eXpress technical support.

Can a Regular CTS Be Disconnected From the Federation?

No.
CTS
cannot work in isolation.

Enterprise Transport Server, ETS

ETS
The enterprise transport server unites the corporate servers of a large interregional enterprise into a “mini-federation”. In it, corporate servers may be designated
eCTS
instead of
CTS
. The server is an analogue of the public
RTS
server, which unites
CTS
servers. The server is managed by an organization, for example, the one you work for. In eXpress,
ETS
contacts and servers are marked with blue icons.
For Administrators: Purpose & Features of ETS

Purpose of ETS

  • ETS
    takes over the functions of the public
    RTS
    server for the branded app;
  • Routing of messages between users: employees of one
    eCTS
    communicate securely with employees of another
    eCTS
    ;
  • Initial registration of users within the organization’s contour (including working with SMS codes);
  • Sending push notifications to branded client apps within the organization.

Features of ETS

  • ETS
    is installed only within the organization's perimeter.
  • The organization independently manages security policies and contour access.
  • Initial user registration takes place within the organization’s perimeter and can be customized.
  • Users connect to
    ETS
    through a special branded app. The organization distributes it. Before publishing in app stores, the code can be checked.
  • Users register on eCTS. Users cannot stay on
    ETS
    .
  • RTS
    users can register on the
    ETS
    client app. If the user was a corporate user in eXpress, a logout is required, otherwise an error is displayed.
  • Users' phonebooks are stored on
    ETS
    .
  • ETS
    is independent of
    RTS
    , but is linked to
    RTS
    by default so that
    ETS
    users can communicate with users of
    RTS
    and other
    CTS
    . New
    eCTS
    are created on
    ETS
    , and
    RTS
    “does not know” about them.
    ETS
    can also work autonomously, in complete isolation.

Who Administrates the ETS?

Server-side administration is handled by your organization support, or by partner, or by paid eXpress technical support.

Server Interaction in the Federation

What Unites Servers in the Federation?

  • Routing of messages, files, and calls.
    RTS
    is a global gateway for all traffic between non-trusted
    CTS
    and for traffic to and from public users.
    ETS
    is the same gateway inside the enterprise’s “mini-federation” for its own
    eCTS
    .
  • End-to-end identification of users by HUID. It is performed by
    RTS
    or
    ETS
    .
  • Trusted connections (trusts). A trust connection can be established between two corporate servers (
    CTS
    /
    eCTS
    ) of the same or different organizations. Trust servers enable direct traffic exchange bypassing
    RTS
    , trust search for users, and extended permissions for invitation links and files from within the corporate network (CDTN).
    For Administrators: How to Manage Trusts
    CTS
    eCTS
     Trusts are managed by the administrator on the Trusts tab in the admin panel.
  • Distributed storage of chats and files. Cross-server chats and channels, cross-server call and conference recordings, and transferred files are replicated to the servers of all participants — see “Storage and Deletion of Chats” and “Files”. This also explains what history a new participant from a “fresh” server sees — see “Chat History”.
  • Isolated
    ETS
     does not participate in the common federation: its users cannot see users from
    RTS
    /
    CTS
    /other
    ETS
    servers, and vice versa — see the definition of “Isolate”.
  • Emergency mode of the corporate server is enabled when the root server is unavailable. It disables trust connections and interaction with external users — see details below.
  • The eXpress global chat is the only system chat common to all users of the federation. It is sent by
    RTS
    . The administrator of the corporate server can disable it on their server — see “Global Chats”.
For Administrators: How to Configure My Server to Operate in the Federation?
CTS
ETS
eCTS
 Details on administering trusts, network perimeter restrictions, and links with public / corporate / trust access levels can be found in the admin panel FAQ.
For Administrators: Corporate Server Emergency Mode When RTS Is Unavailable
Lite
CTS
eCTS
 If
RTS
becomes unavailable, a regular
CTS
/
Lite
server or an
eCTS
server subordinate to a non-isolated
ETS
enters emergency mode. In this state:
App Function
CTS
Lite
eCTS
(non-isolated
ETS
)
Registration and login of new corporate users Not working. Current sessions remain active. Working, but a synchronization queue with the federation builds up
SMS code verification Not working Working
Push notifications Not working Working, except when push notifications are proxied through
RTS
Synchronization of user public keys Not working Working, but a synchronization queue with the federation builds up
Trusted server connections Working as long as authentication tokens are valid Working
Creating chats, calls, and conferences Working as long as authentication tokens are valid, but only with users from this server and trusted servers. Guests must be created on this server — more details. Working, but only with users from this server and trusted servers. Guests must be created on this server — more details.
Server contact directory Working as long as RTS authentication tokens are valid. Over time, the phonebook becomes outdated, and users from other servers start showing as “Unknown User” Working, but becomes outdated over time, and users from other servers start showing as "Unknown User"
In summary:
  • CTS
    /
    Lite
    server does not support fully autonomous operation     without a connection to
    RTS
    — both the corporate server and the client need access to it.
  • eCTS
    server in the federation (under a non-isolated
    ETS
    ) can operate without a connection to
    RTS
    for a certain period of time.
  • eCTS
    server under an isolated
    ETS
    normally operates without a connection to
    RTS
    .

How Does Traffic Flow in an Interserver Chat/Call?

Participant Composition Route
Single server (
CTS
/
eCTS
)		 Local only on the server
Only trusted
CTS
/
eCTS
 Directly between servers, bypassing
RTS
Non-trust corporate servers Via
RTS
At least one public (external) user Via
RTS
The route diagram for a specific chat can be found in the chat properties > “Routing”.

What Is Needed to Communicate With Colleagues on Other Servers?

Typically, no additional steps are required: you can communicate with colleagues on other federation servers immediately. For more details on finding colleagues, see this article. If your organization's or network provider's policy restricts your network connection, contact support or the administrator of your organization, partner, or provider. Ask them to grant network access to your devices.

How to Switch to an Isolated Environment?

To disconnect from the eXpress federation, your organization needs to deploy and configure an
ETS
server and buy a license for it.

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