Understanding Call Correlation

Message segments (call legs) of a call event can be distributed and stored on multiple mediation engines. Call correlation is the process of collecting all the distributed message segments of the call event from each mediation engine, merging them in the order of the call, and displaying the call event as a whole.

Mediation Engine Connector allows a user to monitor multiple mediation engines. Because each mediation engine contains its own list of call events, which may contain only call legs of the full call event, Mediation Engine Connector has to decide which of the call events from each mediation engine are from the same call. When passing a call event through a device monitored by multiple mediation engines, the Mediation Engine Controller locates any identical call events and consolidates the data. The consolidated call event data is displayed as one single call event flow in Mediation Engine Connector.

Note:

If any error is encountered while connecting to any of the Mediation Engine, a warning is displayed besides the Mediation Engine node selector drop-down so that the users can check the connection nodes in the Connection test settings option.

About On Demand Correlation

In the Mediation Engine Connection screen, when opening a call from an Mediation Engine node view, the Mediation Engine Connector tries to correlate the call against other calls seen in different Mediation Engines, then it is an On Demand Correlation.

In an On Demand Correlation:

There is no real time in the inter-Mediation Engine call correlation.
The Active Calls Mediation Engine Connector KPI is the sum of the active session from all Mediation Engines, there is no correlation behind and thus the value is higher than the real one.

The key for Mediation Engine Connector correlation is having the platform devices well defined across the Mediation Engines, assigning properly their internal/external role in the Platform Devices settings view. The call segment between an internal and an external device must be seen twice, by two Mediation Engines. There can be more than one segment between two Mediation Engines for the same call.

When a call leg happens between an internal and an external platform device, the Mediation Engine builds a hash that identifies that leg.

Call hash = hash ( INVITE message)

The Mediation Engine Connector relies on the call hashes to find the other related calls across different Mediation Engines. There is no hash between internal vs. internal or external vs external devices. Therefore, platform devices must be correctly configured or Mediation Engine Connector inter-node correlation does not occur. If two Mediation Engines don't see the same call segment the correlation is not possible. For correlation to occur, call segment must be seen twice.

To correlate Mediation Engine Connector:

Find the related call's Mediation Engine:
- When opening a call from a node panel this step is not needed, since we already know the Mediation Engine node.
- When searching for calls from a regional panel, the Mediation Engine Connector queries all the Mediation Engines to find the related Mediation Engine(s).
- The ME where the call was found queries the neighboring nodes to check for additional call legs, using the call hashes. Furthermore, those nodes will check in another nodes, avoiding the nodes they already traversed.

Implementing Call Correlation

Mediation Engine Connector will correlate the call event when call events share a common call leg.

For each call leg that is a candidate for being the common call leg, the mediation engine runs a hash function over the INVITE message and stores it in the database together with a pointer to the call event of the call leg. A candidate call leg is a call leg where one of the two endpoints is a neighbor device. A neighbor device is a device configured on one of the other mediation engines, which is not marked as an External device.

When displaying the call event, each mediation engine is checked for an identical hash in their database. If true, the details of their call event are included in the display.

Note:

In Operations Monitor, the Mediation Engine Connector hash on P-Charging-Vector icid-value parameter and the Mediation Engine Connector hash search on all external legs settings affect the generation of hashes.

For more information on the Mediation Engine Connector hash on P-Charging-Vector icid-value parameter and the Mediation Engine Connector hash search on all external legs settings, see System Settings Summary in Operations Monitor User's Guide.

For example:

You have a device configuration that contains multiple sites containing one mediation engine for each site. Each site also contains several devices and all of the call's event traffic involved in one of these devices is sent to the site's mediation engine.

The call event leaves site A and directly enters site B, such as there is a call leg with one device on site A and one device on site B.
A device is configured as an Internal device on its site's mediation engine.
If there is direct traffic between a device on site A and a device on site B, the device on site B is configured as an External device on the mediation engine of site A. If there is direct traffic between a device on site B and a device on site A, the device on site A is configured as an External device on the mediation engine of site B.
Additional devices on a site can be configured as External devices on other sites mediation engines.

Configuration 1

The call event traverses five devices.

Devices DEV1 and DEV 2 are on site A, devices DEV 3, DEV 4, and DEV 5 are on site B. The following Internal assignments satisfy the requirement in point 2.

     DEV1 <--leg1--> DEV2 <--leg2--> DEV3 <--leg3--> DEV4 <--leg4--> DEV5
ME1  Internal        Internal
ME2                                  Internal        Internal        Internal

Configuration 2

If there is traffic from DEV2 to DEV3, add External devices as follows:

     DEV1 <--leg1--> DEV2 <--leg2--> DEV3 <--leg3--> DEV4 <--leg4--> DEV5
ME1  Internal        Internal        External
ME2                  External        Internal        Internal        Internal

Because leg2 goes from DEV2 to DEV3 the above configuration satisfies the requirement in point 1 for this call event. This is a functioning configuration.

Configuration 3

This can be extended to the following, which satisfies point 4.

     DEV1 <--leg1--> DEV2 <--leg2--> DEV3 <--leg3--> DEV4 <--leg4--> DEV5
ME1  Internal        Internal        External        External        External
ME2  External        External        Internal        Internal        Internal

Configuring Multiple Mediation Engine Nodes for Call Correlation

To configure multiple mediation engine nodes for call correlation, do the following:

Setting the Authentication of a Mediation Engine

Mediation engines communicate with Mediation Engine Connector using the fully qualified host name or IP address of Mediation Engine Connector and an authentication password, which is used by Mediation Engine Connector to verify the authentication of the mediation engines.

To set the authentication of a mediation engine:

In a web browser, log in to Mediation Engine Connector.

The Mediation Engine Connector window appears.
From the user list, select Settings, where user is your login name.

The Settings window appears.
Under Mediation Engines, select ME Connector.

The ME Connector page appears.
In the Hostname or IP of MEC text box, enter the host name of Mediation Engine Connector.
In the Password for Mediation Engine nodes, enter a secure password.
Click Save.

Setting the Authentication of Mediation Engine Connector

Before a connection is made between Mediation Engine Connector and a mediation engine, an authentication token (password) is used to verify the authentication of Mediation Engine Connector.

All mediation engines require their own individual authentication token. Apply the following steps to each mediation engine in your network.

To set the authentication of Mediation Engine Connector:

In a web browser, log in to Operations Monitor.

The Operations Monitor window appears.
From the user list, select Settings, where user is your login name.

The Settings window appears.
Under System Management, select Systems Settings.

The System Settings page appears.
Scroll down to the Authentication token (shared secret between MEC and ME) row.
Double-click the Authentication token (shared secret between MEC and ME) row.

The Update System Setting dialog box appears.
In the Default value text box, enter the mediation engine's authentication secret.
Click Update.
Under Network, select Mediation Engine Connector.

The Mediation Engine Connector page appears.
In the Authentication token (shared secret between MEC and ME) text box, enter the mediation engine's authentication secret.
Click Update.
Click Close, which closes the Settings window

Adding the Mediation Engines to the Mediation Engine Connector Node List

Adding the mediation engines to the Mediation Engine Connector node list makes each mediation engine available as a node in the top menu bar of Mediation Engine Connector.

To add the mediation engines to the Mediation Engine Connector node list:

Verify that the Settings window is still open.
Under Mediation Engines, select ME Management.
The ME Management page appears.
In the ME Management toolbar, click Add.
In the Node Name column, enter a name for the mediation engine's node.
In the Hostname or IP column, enter the host name of the mediation engine.
In the Share secret column, enter the mediation engine's authentication secret.
Repeat step 3 to step 6 for all the mediation engines in your network.
In the ME Management toolbar, click Replicate configuration, which propagates the changes to all your mediation engines.
In the ME Management toolbar, click Save.

Testing the Connection

To test the connection:

Verify the Settings window is open.
Under Mediation Engines, select Connection test.

The Connection test page appears.
In the Connection test toolbar, click Start Connection Test.
Verify that the Status column displays OK, which confirms that the configuration is working and all the machines are reachable.
Click Close, which closes the Settings window.

Setting the Platform Devices for Each Mediation Engine

To set the platform devices for each mediation engine:

In a web browser, log in to Operations Monitor.

The Operations Monitor window appears.
From the user list, select Settings, where user is your login name.

The Settings window appears.
Under Platform, select Platform Devices.

The Platform Devices page appears.
Select the device you wish to set as an External device.

By default, devices are set as Internal devices.
In the Platform Devices toolbar, click Toggle external, which sets the device as an External device and makes it visible to other mediation engines on Mediation Engine Connector.
Click Close, which closes the Settings window.

Applying Configuration Changes

It is important to replicate the configuration after any change related to platform devices on any Mediation Engine node. When you have finished configuring your devices, apply the configuration changes.

To apply configuration changes:

In a web browser, log in to Mediation Engine Connector.

The Mediation Engine Connector window appears.
From the user list, select Settings, where user is your login name.
The Settings window appears.
Under Mediation Engines, select ME Management.
The ME Management page appears.
In the ME Management toolbar, click Replicate configuration, which propagates the changes to all your mediation engines.
In the ME Management toolbar, click Save.
Click Close, which closes the Settings window.

(Optional) Setting the Timeout for Call Searches

When searching for a call event in Mediation Engine Connector, all mediation engine nodes are queried. If a mediation engine node finds a call event, it queries the neighboring nodes to check for additional call legs. Use the Timeout for Mediation Engine querying system setting to set the timeout for these queries on the mediation engine nodes

To set the timeout for call searches:

In a web browser, log in to Operations Monitor.

The Operations Monitor window appears.
From the user list, select Settings, where user is your login name.
Under System Management, select Systems Settings.

The System Settings page appears.
Scroll down the System Settings page until you see the Timeout for Mediation Engine querying row.
Double-click the Timeout for Mediation Engine querying row.

The Update System Setting dialog box appears.
In the Maximum value text box, enter a number between 5 and 120.
Click Update.

Viewing Correlation Calls

A correlated call event is only viewable when a mediation engine is accessed from Mediation Engine Connector. If you access the mediation engine directly from a web browser and not from Mediation Engine Connector, only the call events content found in the mediation engine is displayed.

To view correlation calls:

In a web browser, log in to Mediation Engine Connector.
The Mediation Engine Connector window appears.
In the top menu bar, select a mediation engine from the Select a node list.
The Operations Monitor window appears.
From the Navigation pane under Operations, click Calls.
In the Recent calls table, right-click the row for which to display the correlated call event's message flow.
The Message Flow for Call: caller and callee window appears.
where caller is the number that initiated the call and callee is the call number that received the call.
When you have finished viewing the call event's message flow, press the ESC key, which closes the message flow window.