E2T Multiple Instances

Abbreviation

General

The RIC contains several E2T Instances, each one of them manages several RANs. E2M is the one which manages them. It means:

• When E2T Instance starts running and finished its Initialization, it sends RMR message (E2 Initialization) to E2M. E2M Inform to RM and Registers it in the E2M DB.

• When a new RAN is sends the RIC Setup Request, E2M Inform to RM the association and associate this RAN to this  E2T Instance in DB

• When RAN Lost connection, E2M Inform to RM the disassociation and disassociate this RAN to this  E2T Instance in DB

• E2M Handle Keep Alive (KA) RMR handshake with the E2M Instances. When an Instance doesn’t respond for period of time to KA Request from E2M, E2M kills (Through K8S) this instance, signs all the RANs associated with it as Disconnected, delete the E2T address from DB  and inform RM the disassociation.

• For any new or dead E2M Instance, and for any RAN Association / disassociation, E2M informs RM. RM updates the Routing tables and publish an updated RMR to all RIC. 

• When existing E2T Instance restarts and sends RMR message (E2 Initialization) to E2M. E2M Inform to RM the disassociation of all its RANs and disassociate them in DB
• If the RM isn't accessible, "positive" scenario (New E2T Address, new RAN Setup) are not executed, waiting for additional E2T will sends its Address or the RAN renew its Setup. But "negative" scenario (Like Lost connection, KA kills E2T, Existing E2T restarts) are executed. When RM will restarts and query E2M, it will sync with the E2T and RANs association and publish RMR to all RIC.

Keep Alive

• Each Configurable time (100 Milliseconds) E2M sends broadcast KA Request to all living E2T Instances through the RMR.

• Every E2T Instance which gets it, responds with KA Response.

• If any E2T Instance doesn’t respond for a configurable time (400 Milliseconds) - E2M “kills” it:

  • E2M asks the K8S to kill the E2T Instance.

  • E2M disassociate the RANs associated with this “dying” instance, signs them as disconnected and Updates the RM about the disassociation of the RANs and about the deletion of the dead E2T Instance.

• There is some logic how to sync between parallel flows - Killing an E2T Instance parallel to E2 Initialize arrives. See below.

E2 Initialization

• As described, when E2T Instance starts running and finished its Initialization, it sends RMR message (E2 Initialization) to E2M.

• If this is a new address (IP) then -

  • E2M updates the Routing Manager there is new E2T Instance

  • If success - E2M Registers it in the E2M DB. If fail - E2M does nothing. E2T will sends another time E2 Initialize to E2M if no KA Request arrives during the 500 Milliseconds after the previous E2 Initialize.

• If this is an existing E2T Instance, then

  • E2M disassociate the RANs associated with this "restart" instance, signs them as disconnected and Updates the RM about the disassociation of the RANs

• There is some logic how to sync between parallel flows - Killing an E2T Instance parallel to E2 Initialize arrives.

Sync between KA Killing, E2 Initialize arrives and KA Response

E2M manages States that E2T Instance can be in the DB:

• Active (normal state). Selector mechanism can choose it.

• To be deleted - KA moves it to this state in DB the moment is understand it is dead. Selector mechanism can’t choose it. It is stay in this state until Routing manager success (in this case the entire entry is deleted) or failure, which is moved to the next step

In case E2T initialize arrives and this E2T is in “To be Deleted” state - Don’t do anything. E2T will send another E2T initialize in case no KA during 300 milliseconds after E2 Initialize.

Association RAN to Instance

• There are 2 places where E2M search for a living E2T Instance to associate it with RAN:

  1. When a Setup Request from Dashboard arrives. This is for New RAN or for existing RAN which isn’t associated with any E2T Instance

  2. When KA kills an E2T Instance and divides its RANs to other living E2T Instances

• E2M chooses the E2T Instance with the least # of RANs.

• Anyhow, until the Routing Manager isn’t synced with this association, it isn’t stored in E2M DB

• Setup Request from Dashboard which fails either in choosing any E2T Instance or updating the Routing Manager, either for New RAN or existing which isn’t associate with any E2T Instance , returns special rejection error is telling the Dashboard to try later.

• In case KA failure in choosing the E2T to the RAN, the RANs are inserted to Orphan List. See below how E2M handle with Orphan List. It is usually when the last E2T Instance fails.

Dissociation RAN

• RAN which is already associated with E2T Instance, stays with this association, even if it lost connection. E2M will try to re-new the Setup until Max Retries (Configurable) reached.

• There are 2 places where E2M dissociate RAN:

  1. When the Max Retries of sending Setup arrives, as a result of Lost Connection. The RAN is disassociate.

  2. When a request to Red Button arrives (See below)

Interface to Routing Manager

• Routing Manager updates the Routing Table in the following ways:

  1. Add or Delete E2T Instance - There are 2 RMR messages that are “Broadcast”:

     1. KA Request

     2. Clear all Connection (“Red Button”)

  2. Associate RAN(s) to E2T Instance (it can overrides previous association)

  3. Delete RAN association

• E2M updates the Routing Manager in the following flows:

  1. When a new E2T Instance Initialized.

  2. When a new RAN is added and associated to existing E2T Instance

  3. When KA kills existing E2T Instance - in this update it also associates list of RANs to other existing E2T Instance (Or dissociate list of RANs since it was the last E2T Instance) and also delete E2T Instance

  4. When RAN lost connection and it exceed the Max Retry.

  5. When a Red Button is requested - E2M dissociate all RANs

  6. When E2T Instance initialized, it is the first, and list of Orphans “are waiting” for it - E2M associates list of RANs to this E2T Instance

• There are 4 REST APIs Routing Manager published. U can read their Swagger at Routing Manager Swagger

Red Button

• When Red Button request from Dashboard arrives, E2M inform Routing Manager to disassociate all RANs

• E2M sends “broadcast” the Close all connections to all E2T Instances.

Orphans

• As described above, when last E2T Instance fails, its RAN are entering the Orphan List.

• The KA Job, after sending the KA request and after checking there is no any E2T which doesn’t respond and need to be killed. examines the Orphan List is not empty and there is a E2T Instance to associate them. If yes, it is updating the Routing Manager and if OK - sends Setup on each RAN

• Also, on Red Button, we empty the Orphan List.

RAN State, Association and Orphan

To summarize, RAN can be in the following:

Associated with E2 Instance

RAN can be in the following state:

• Connected

• Connected Failure

• Disconnect, but with Count of Retry less then Max, Usually this is in case RMR Failure

Associated with the Orphan List

RAN should be in a Disconnect State, while Count of Retry is 0.

Disassociated

RAN can be in the following state:

• Shut Down

• Disconnect, but with Count of Retry equal to Max