2 .. Copyright (c) 2019 AT&T Intellectual Property.
3 .. Copyright (c) 2019 Nokia.
5 .. Licensed under the Creative Commons Attribution 4.0 International
6 .. Public License (the "License"); you may not use this file except
7 .. in compliance with the License. You may obtain a copy of the License at
9 .. https://creativecommons.org/licenses/by/4.0/
11 .. Unless required by applicable law or agreed to in writing, documentation
12 .. distributed under the License is distributed on an "AS IS" BASIS,
13 .. WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15 .. See the License for the specific language governing permissions and
16 .. limitations under the License.
28 Subscription Manager is a basic platform service in RIC. It is responsible for managing E2 subscriptions from xApps to the
29 Radio Access Network (RAN).
31 xApp can subscribe and unsubscribe messages from gNodeB through Subscription Manager. Subscription Manager manages the subscriptions
32 and message routing of the subscribed messages between E2 Termination and xApps. If one xApp has already made a subscription and then
33 another xApp initiates identical subscription, Subscription Manager does not forward the subscription to gNodeB but merges the
34 subscriptions internally. In merge case Subscription Manager just updates the message routing information to Routing Manager and
35 sends response to xApp.
37 There can be only one ongoing RIC Subscription or RIC Subscription Delete procedure towards RAN at any time. That is because Subscription
38 Manager is able to merge new subscriptions only which those it has already received successful response from RAN. Subscriptions
39 and delete subscriptions are therefore queued in Subscription Manager. Subscription Manager may need to do reties during subscribe or
40 unsubscribe procedure. This needs to be considered when retries are implemented in xApp side, as it can increase completion time of the
41 procedure. xApp's retry delay should not be too short.
43 .. image:: images/PlaceInRICSoftwareArchitecture.png
45 :alt: Place in RIC's software architecture picture
52 Subscribed messages from RAN are transported to RIC inside RIC Indication message. RIC Indication message is transported to xApp
53 inside RMR message, in Payload field of the RMR message. RMR message is routed to xApp based on SubId field (subscription id) in
54 the RMR header. Same routing mechanism is used also for response messages from Subscription Manager to xApp. Subscription Manager is
55 not able to respond to xApp if route for subscription has not been created.
57 When xApp sends message to Subscription Manager it sets -1 in SubId field in the RMR header. It means that messages are routed based
58 on message type (Mtype filed in RMR header). RIC Subscription Request and RIC Subscription delete Request messages are pre configured
59 to be routed to Subscription Manager.
61 Subscription Manager allocates unique RIC Request Sequence Number for every subscription during Subscription procedure. Subscription
62 Manager replaces existing ASN.1 decoded RIC Request Sequence Number in the RIC Subscription Request message allocated by the xApp.
63 That sequence number (subscription id) is then used for the subscription in RIC and RAN as long the subscription lives. xApp gets
64 the sequence number in RIC Subscription Response message from Subscription manager based on the message types.
66 Subscribed messages are routed to xApps based on sequence number. Sequence number is placed in the SubId field of the RMR message
67 header when E2 Termination sends the subscribed message to xApp. When xApp wants to delete the subscription, the same sequence number
68 must be included in the ASN.1 encoded RIC Subscription Delete Request message sent to Subscription Manager.
70 Subscription Manager allocates and substitutes RIC Requestor ID for E2 interface communication. Currently the ID value is always 123.
71 RAN gets the Request of the xApp who makes the first subscription. RAN uses Subscription Manager allocated Requestor ID in all RIC
72 Indication messages it sends to RIC for the subscription. Subscription Manager returns the same RIC Requestor ID in response message
73 to xApp as was in the request. In merge case subscription is created only for the first requestor.
75 TransactionId (Xid) in RMR message header is used to track messages between xApp and Subscription Manager. xApp allocates it. Subscription
76 Manager returns TransactionId received from xApp in response message to xApp. xApp uses it to map response messages to request messages
79 * Subscription procedure
83 xApp sends RIC Subscription Request message to Subscription Manager. Subscription Manager validates request types in the message and sends
84 route create to Routing Manager over REST interface. When route is created successfully Subscription Manager forwards request to E2
85 Termination. When RIC Subscription Response arrives from E2 Termination Subscription Manager forwards it to xApp.
87 Subscription Manager supervises route create and RIC Subscription Request with a timer.
89 RIC Indication messages which are used to transport subscribed messages from RAN are routed from E2 Termination to xApps
90 directly using the routes created during Subscription procedure.
92 Subscription Manager supports REPORT, POLICY and INSERT type subscriptions (RICActionTypes). CONTROL is not supported. POLICY type
93 subscription can be updated. In update case signaling sequence is the same as above, except route is not created to Routing manager.
94 xApp uses initially allocated TransactionId and RIC Request Sequence Number in update case. Route in POLICY type subscription case is needed
95 only that Subscription Manager can send response messages to xApp. RIC Subscription Request message contains list of RICaction-ToBeSetup-ItemIEs.
96 The list cannot have REPORT, POLICY, INSERT action types at the same time. Subscription Manager checks actions types in the message.
97 If both action types is found the message is dropped.
100 .. image:: images/Successful_Subscription.png
102 :alt: Successful subscription picture
107 In failure case Subscription Manager checks the failure cause and acts based on that. If failure cause is "duplicate" Subscription
108 Manager sends delete to RAN and then resends the same subscription. If failure cause is such that Subscription manager cannot do
109 anything to fix the problem, it sends delete to RAN and sends RIC Subscription Failure to xApp. Subscription Manager may retry RIC
110 Subscription Request and RIC Subscription Delete messages also in this case before it responds to xApp.
112 .. image:: images/Subscription_Failure.png
114 :alt: Subscription failure picture
116 * Timeout in Subscription Manager
118 In case of timeout in Subscription Manager, Subscription Manager may resend the RIC Subscription Request to RAN. If there is no response
119 after retry, Subscription Manager shall NOT send any response to xApp. xApp may retry RIC Subscription Request, if it wishes to do so.
120 Subscription Manager does no handle the retry if Subscription Manager has ongoing subscription procedure for the same subscription.
121 Subscription just drops the request.
125 xApp may resend the same request if there is no response in expected time. If xApp resends the same request while processing of previous
126 request has not been completed in Subscription Manager then Subscription Manager drops the new request, makes a log writing and continues
127 processing previous request.
129 .. image:: images/Subscription_Timeout.png
131 :alt: Subscription timeout picture
133 * Subscription delete procedure
137 xApp sends RIC Subscription Delete Request message to Subscription Manager. xApp must use the same RIC Request Sequence Number which
138 it received in RIC Subscription Response message when subscription is deleted. When Subscription Manager receives RIC Subscription
139 Delete Request message, Subscription Manager first forwards the request to E2 Termination. When RIC Subscription Delete Response arrives
140 from E2 Termination to Subscription Manager, Subscription Manager forwards it to xApp and then request route deletion from Routing Manager.
142 Subscription Manager supervises RIC Subscription Deletion Request and route delete with a timer.
144 .. image:: images/Successful_Subscription_Delete.png
146 :alt: Successful subscription delete picture
150 Delete procedure cannot fail from xApp point of view. Subscription Manager always responds with RIC Subscription Delete Response to xApp.
152 .. image:: images/Subscription_Delete_Failure.png
154 :alt: Subscription delete failure picture
156 * Timeout in Subscription Manager
158 In case of timeout in Subscription Manager, Subscription Manager may resend the RIC Subscription Delete Request to RAN. If there is no
159 response after retry, Subscription Manager responds to xApp with RIC Subscription Delete Response.
163 xApp may resend the same request if there is no response in expected time. If xApp resends the same request while processing of previous
164 request has not been completed in Subscription Manager then Subscription Manager drops the new request, makes a log writing and continues
165 processing previous request.
167 .. image:: images/Subscription_Delete_Timeout.png
169 :alt: Subscription delete timeout picture
171 * Unknown subscription
173 If Subscription Manager receives RIC Subscription Delete Request for a subscription which does not exist, Subscription Manager cannot respond
174 to xApp as there is no route for the subscription.
176 * Subscription merge procedure
180 xApp sends RIC Subscription Request message to Subscription Manager. Subscription Manager checks is the Subscription mergeable. If not,
181 Subscription Manager continues with normal Subscription procedure. If Subscription is mergeable, Subscription Manager sends route create
182 to Routing Manager and then responds with RIC Subscription Response to xApp.
184 Route create is supervised with a timer.
186 Merge for REPORT type subscription is possible if Action Type and Event Trigger Definition of subscriptions are equal.
188 ``Only REPORT type subscriptions can be be merged.``
190 .. image:: images/Successful_Subscription_Merge.png
192 :alt: Successful subscription merge picture
196 Failure case is basically the same as in normal subscription procedure. Failure can come only from RAN when merge is not yet done.
197 If error happens during route create Subscription Manager drops the RIC Subscription Request message and xApp does not get any response.
199 * Timeout in Subscription Manager
201 Timeout case is basically the same as in normal subscription procedure but timeout can come only in route create during merge operation.
202 If error happens during route create, Subscription Manager drops the RIC Subscription Request message and xApp does not get any response.
206 xApp may resend the same request if there is no response in expected time. If xApp resends the same request while processing of previous
207 request has not been completed in Subscription Manager then Subscription Manager drops the new request, makes a log writing and continues
208 processing previous request.
210 * Subscription delete merge procedure
214 xApp sends RIC Subscription Delete Request message to Subscription Manager. If delete concerns merged subscription, Subscription Manager
215 responds with RIC Subscription Delete Response to xApp and then sends route delete request to Routing manager.
217 Subscription Manager supervises route delete with a timer.
219 .. image:: images/Successful_Subscription_Delete_Merge.png
221 :alt: Successful subscription delete merge picture
225 Delete procedure cannot fail from xApp point of view. Subscription Manager responds with RIC Subscription Delete Response message to xApp.
227 * Timeout in Subscription Manager
229 Timeout can only happen in route delete to Routing manager. Subscription Manager responds with RIC Subscription Delete Response message to xApp.
233 xApp may resend the same request if there is no response in expected time. If xApp resends the same request while processing of previous
234 request has not been completed in Subscription Manager then Subscription Manager drops the new request, makes a log writing and continues
235 processing previous request.
239 If Subscription Manager receives unknown message, Subscription Manager drops the message.
243 When xApp is restarted for any reason it may resend subscription requests for subscriptions which have already been subscribed. If REPORT or INSERT type
244 subscription already exists and RMR endpoint of requesting xApp is attached to subscription then successful response is sent to xApp directly without
245 updating Routing Manager and BTS. If POLICY type subscription already exists, request is forwarded to BTS and successful response is sent to xApp.
246 BTS is expected to accept duplicate POLICY type requests. In restart IP address of the xApp may change but domain service address name does not.
247 RMR message routing uses domain service address name.
249 * Subscription Manager restart
251 Subscription Manager stores successfully described subscriptions from db (SDL). Subscriptions are restored from db in restart. For subscriptions which
252 were not successfully completed, Subscription Manager sends delete request to BTS and removes routes created for those. Restoring subscriptions from
253 db can be disable via submgr-config.yaml file by setting "readSubsFromDb": "false".
257 Subscription Manager adds following statistic counters:
259 Subscription create counters:
260 - SubReqFromXapp: The total number of SubscriptionRequest messages received from xApp
261 - SubRespToXapp: The total number of SubscriptionResponse messages sent to xApp
262 - SubFailToXapp: The total number of SubscriptionFailure messages sent to xApp
263 - SubReqToE2: The total number of SubscriptionRequest messages sent to E2Term
264 - SubReReqToE2: The total number of SubscriptionRequest messages resent to E2Term
265 - SubRespFromE2: The total number of SubscriptionResponse messages from E2Term
266 - SubFailFromE2: The total number of SubscriptionFailure messages from E2Term
267 - SubReqTimerExpiry: The total number of SubscriptionRequest timer expires
268 - RouteCreateFail: The total number of subscription route create failure
269 - RouteCreateUpdateFail: The total number of subscription route create update failure
270 - MergedSubscriptions: The total number of merged Subscriptions
272 Subscription delete counters:
273 - SubDelReqFromXapp: The total number of SubscriptionDeleteResponse messages received from xApp
274 - SubDelRespToXapp: The total number of SubscriptionDeleteResponse messages sent to xApp
275 - SubDelReqToE2: The total number of SubscriptionDeleteRequest messages sent to E2Term
276 - SubDelReReqToE2: The total number of SubscriptionDeleteRequest messages resent to E2Term
277 - SubDelRespFromE2: The total number of SubscriptionDeleteResponse messages from E2Term
278 - SubDelFailFromE2: The total number of SubscriptionDeleteFailure messages from E2Term
279 - SubDelReqTimerExpiry: The total number of SubscriptionDeleteRequest timer expires
280 - RouteDeleteFail: The total number of subscription route delete failure
281 - RouteDeleteUpdateFail: The total number of subscription route delete update failure
282 - UnmergedSubscriptions: The total number of unmerged Subscriptions
284 SDL failure counters:
285 - SDLWriteFailure: The total number of SDL write failures
286 - SDLReadFailure: The total number of SDL read failures
287 - SDLRemoveFailure: The total number of SDL read failures
289 Configurable parameters
290 -----------------------
291 Subscription Manager has following configurable parameters.
292 - Retry timeout for RIC Subscription Request message
293 - e2tSubReqTimeout_ms: 2000 is the default value
295 - Retry timeout for RIC Subscription Delete Request message
296 - e2tSubDelReqTime_ms: 2000 is the default value
298 - Waiting time for RIC Subscription Response and RIC Subscription Delete Response messages
299 - e2tRecvMsgTimeout_ms: 2000 is the default value
301 - Try count for RIC Subscription Request message
302 - e2tMaxSubReqTryCount: 2 is the default value
304 - Try count for RIC Subscription Delete Request message
305 - e2tMaxSubDelReqTryCount: 2 is the default value
307 - Are subscriptions read from database in Subscription Manager startup
308 - readSubsFromDb: "true" is the default value
310 The parameters can be changed on the fly via Kubernetes Configmap. Default parameters values are defined in Helm chart
312 Use following command to open Subscription Manager's Configmap in Nano editor. Firts change parameter and then store the
313 change by pressing first Ctrl + o. Close editor by pressing the Ctrl + x. The change is visible in Subscription Manager's
314 log after some 20 - 30 seconds.
318 KUBE_EDITOR="nano" kubectl edit cm configmap-ricplt-submgr-submgrcfg -n ricplt
320 REST interface for debugging and testing
321 ----------------------------------------
322 Give following commands to get Subscription Manager pod's IP address
326 kubectl get pods -A | grep submgr
328 ricplt submgr-75bccb84b6-n9vnt 1/1 Running 0 81m
330 Syntax: kubectl exec -t -n ricplt <add-submgr-pod-name> -- cat /etc/hosts | grep submgr | awk '{print $1}'
332 Example: kubectl exec -t -n ricplt submgr-75bccb84b6-n9vnt -- cat /etc/hosts | grep submgr | awk '{print $1}'
340 Example: curl -s GET "http://10.244.0.181:8080/ric/v1/metrics"
346 Example: curl -X GET "http://10.244.0.181:8088/ric/v1/subscriptions"
348 Delete single subscription from db
352 Syntax: curl -X POST "http://10.244.0.181:8080/ric/v1/test/deletesubid={SubscriptionId}"
354 Example: curl -X POST "http://10.244.0.181:8080/ric/v1/test/deletesubid=1"
356 Remove all subscriptions from db
360 Example: curl -X POST "http://10.244.0.181:8080/ric/v1/test/emptydb"
362 Make Subscription Manager restart
366 Example: curl -X POST "http://10.244.0.181:8080/ric/v1/test/restart"
368 Use this command to get Subscription Manager's log writings
372 Example: kubectl logs -n ricplt submgr-75bccb84b6-n9vnt
374 Logger level in configmap.yaml file in Helm chart is by default 2. It means that only info logs are printed.
375 To see debug log writings it has to be changed to 4.
382 RAN services explained
383 ----------------------
384 RIC hosted xApps may use the following RAN services from a RAN node:
386 * REPORT: RIC requests that RAN sends a REPORT message to RIC and continues further call processing in RAN after each occurrence of a defined SUBSCRIPTION
387 * INSERT: RIC requests that RAN sends an INSERT message to RIC and suspends further call processing in RAN after each occurrence of a defined SUBSCRIPTION
388 * CONTROL: RIC sends a Control message to RAN to initiate or resume call processing in RAN
389 * POLICY: RIC requests that RAN executes a specific POLICY during call processing in RAN after each occurrence of a defined SUBSCRIPTION
391 Supported E2 procedures and RAN services
392 ----------------------------------------
393 * RIC Subscription procedure with following RIC action types:
399 * RIC Subscription Delete procedure
401 * Merge and delete of equal REPORT type subscriptions.
403 Recommendations for xApps
404 -------------------------
406 * Recommended retry delay in xApp
408 Recommended retry delay for xApp is >= 5 seconds. Length of supervising timers in Subscription Manager for the requests it sends to BTS is by default 2
409 seconds. Subscription Manager makes one retry by default. There can be only one ongoing request towards per RAN other requests are queued in Subscription