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.
26 ``RMR based interface between xApp and Subscription Manager which is explained in this User-Guide``
27 ``is deprecated and will be removed in the future. See second User-Guide which explains new REST``
32 Subscription Manager is a basic platform service in RIC. It is responsible for managing E2 subscriptions from xApps to the
33 Radio Access Network (RAN).
35 xApp can subscribe and unsubscribe messages from gNodeB through Subscription Manager. Subscription Manager manages the subscriptions
36 and message routing of the subscribed messages between E2 Termination and xApps. If one xApp has already made a subscription and then
37 another xApp initiates identical subscription, Subscription Manager does not forward the subscription to gNodeB but merges the
38 subscriptions internally. In merge case Subscription Manager just updates the message routing information to Routing Manager and
39 sends response to xApp.
41 There can be only one ongoing RIC Subscription or RIC Subscription Delete procedure towards RAN at any time. That is because Subscription
42 Manager is able to merge new subscriptions only which those it has already received successful response from RAN. Subscriptions
43 and delete subscriptions are therefore queued in Subscription Manager. Subscription Manager may need to do reties during subscribe or
44 unsubscribe procedure. This needs to be considered when retries are implemented in xApp side, as it can increase completion time of the
45 procedure. xApp's retry delay should not be too short.
47 .. image:: images/PlaceInRICSoftwareArchitecture_RMR.png
49 :alt: Place in RIC's software architecture picture
56 Subscribed messages from RAN are transported to RIC inside RIC Indication message. RIC Indication message is transported to xApp
57 inside RMR message, in Payload field of the RMR message. RMR message is routed to xApp based on SubId field (subscription id) in
58 the RMR header. Same routing mechanism is used also for response messages from Subscription Manager to xApp. Subscription Manager is
59 not able to respond to xApp if route for subscription has not been created.
61 When xApp sends message to Subscription Manager it sets -1 in SubId field in the RMR header. It means that messages are routed based
62 on message type (Mtype filed in RMR header). RIC Subscription Request and RIC Subscription delete Request messages are pre configured
63 to be routed to Subscription Manager.
65 Subscription Manager allocates unique RIC Request Sequence Number for every subscription during Subscription procedure. Subscription
66 Manager replaces existing ASN.1 decoded RIC Request Sequence Number in the RIC Subscription Request message allocated by the xApp.
67 That sequence number (subscription id) is then used for the subscription in RIC and RAN as long the subscription lives. xApp gets
68 the sequence number in RIC Subscription Response message from Subscription manager based on the message types.
70 Subscribed messages are routed to xApps based on sequence number. Sequence number is placed in the SubId field of the RMR message
71 header when E2 Termination sends the subscribed message to xApp. When xApp wants to delete the subscription, the same sequence number
72 must be included in the ASN.1 encoded RIC Subscription Delete Request message sent to Subscription Manager.
74 Subscription Manager allocates and substitutes RIC Requestor ID for E2 interface communication. Currently the ID value is always 123.
75 RAN gets the Request of the xApp who makes the first subscription. RAN uses Subscription Manager allocated Requestor ID in all RIC
76 Indication messages it sends to RIC for the subscription. Subscription Manager returns the same RIC Requestor ID in response message
77 to xApp as was in the request. In merge case subscription is created only for the first requestor.
79 TransactionId (Xid) in RMR message header is used to track messages between xApp and Subscription Manager. xApp allocates it. Subscription
80 Manager returns TransactionId received from xApp in response message to xApp. xApp uses it to map response messages to request messages
83 * Subscription procedure
87 xApp sends RIC Subscription Request message to Subscription Manager. Subscription Manager validates request types in the message and sends
88 route create to Routing Manager over REST interface. When route is created successfully Subscription Manager forwards request to E2
89 Termination. When RIC Subscription Response arrives from E2 Termination Subscription Manager forwards it to xApp.
91 Subscription Manager supervises route create and RIC Subscription Request with a timer.
93 RIC Indication messages which are used to transport subscribed messages from RAN are routed from E2 Termination to xApps
94 directly using the routes created during Subscription procedure.
96 Subscription Manager supports REPORT, POLICY and INSERT type subscriptions (RICActionTypes). CONTROL is not supported. POLICY type
97 subscription can be updated. In update case signaling sequence is the same as above, except route is not created to Routing manager.
98 xApp uses initially allocated TransactionId and RIC Request Sequence Number in update case. Route in POLICY type subscription case is needed
99 only that Subscription Manager can send response messages to xApp. RIC Subscription Request message contains list of RICaction-ToBeSetup-ItemIEs.
100 The list cannot have REPORT, POLICY, INSERT action types at the same time. Subscription Manager checks actions types in the message.
101 If both action types is found the message is dropped.
104 .. image:: images/Successful_Subscription_ASN.1.png
106 :alt: Successful subscription picture
111 In failure case Subscription Manager checks the failure cause and acts based on that. If failure cause is "duplicate" Subscription
112 Manager sends delete to RAN and then resends the same subscription. If failure cause is such that Subscription manager cannot do
113 anything to fix the problem, it sends delete to RAN and sends RIC Subscription Failure to xApp. Subscription Manager may retry RIC
114 Subscription Request and RIC Subscription Delete messages also in this case before it responds to xApp.
116 .. image:: images/Subscription_Failure_ASN.1.png
118 :alt: Subscription failure picture
120 * Timeout in Subscription Manager
122 In case of timeout in Subscription Manager, Subscription Manager may resend the RIC Subscription Request to RAN. If there is no response
123 after retry, Subscription Manager shall NOT send any response to xApp. xApp may retry RIC Subscription Request, if it wishes to do so.
124 Subscription Manager does no handle the retry if Subscription Manager has ongoing subscription procedure for the same subscription.
125 Subscription just drops the request.
129 xApp may resend the same request if there is no response in expected time. If xApp resends the same request while processing of previous
130 request has not been completed in Subscription Manager then Subscription Manager drops the new request, makes a log writing and continues
131 processing previous request.
133 .. image:: images/Subscription_Timeout_ASN.1.png
135 :alt: Subscription timeout picture
137 * Subscription delete procedure
141 xApp sends RIC Subscription Delete Request message to Subscription Manager. xApp must use the same RIC Request Sequence Number which
142 it received in RIC Subscription Response message when subscription is deleted. When Subscription Manager receives RIC Subscription
143 Delete Request message, Subscription Manager first forwards the request to E2 Termination. When RIC Subscription Delete Response arrives
144 from E2 Termination to Subscription Manager, Subscription Manager forwards it to xApp and then request route deletion from Routing Manager.
146 Subscription Manager supervises RIC Subscription Deletion Request and route delete with a timer.
148 .. image:: images/Successful_Subscription_Delete_ASN.1.png
150 :alt: Successful subscription delete picture
154 Delete procedure cannot fail from xApp point of view. Subscription Manager always responds with RIC Subscription Delete Response to xApp.
156 .. image:: images/Subscription_Delete_Failure_ASN.1.png
158 :alt: Subscription delete failure picture
160 * Timeout in Subscription Manager
162 In case of timeout in Subscription Manager, Subscription Manager may resend the RIC Subscription Delete Request to RAN. If there is no
163 response after retry, Subscription Manager responds to xApp with RIC Subscription Delete Response.
167 xApp may resend the same request if there is no response in expected time. If xApp resends the same request while processing of previous
168 request has not been completed in Subscription Manager then Subscription Manager drops the new request, makes a log writing and continues
169 processing previous request.
171 .. image:: images/Subscription_Delete_Timeout_ASN.1.png
173 :alt: Subscription delete timeout picture
175 * Unknown subscription
177 If Subscription Manager receives RIC Subscription Delete Request for a subscription which does not exist, Subscription Manager cannot respond
178 to xApp as there is no route for the subscription.
180 * Subscription merge procedure
184 xApp sends RIC Subscription Request message to Subscription Manager. Subscription Manager checks is the Subscription mergeable. If not,
185 Subscription Manager continues with normal Subscription procedure. If Subscription is mergeable, Subscription Manager sends route create
186 to Routing Manager and then responds with RIC Subscription Response to xApp.
188 Route create is supervised with a timer.
190 Merge for REPORT type subscription is possible if Action Type and Event Trigger Definition of subscriptions are equal.
192 ``Only REPORT type subscriptions can be be merged.``
194 .. image:: images/Successful_Subscription_Merge_ASN.1.png
196 :alt: Successful subscription merge picture
200 Failure case is basically the same as in normal subscription procedure. Failure can come only from RAN when merge is not yet done.
201 If error happens during route create Subscription Manager drops the RIC Subscription Request message and xApp does not get any response.
203 * Timeout in Subscription Manager
205 Timeout case is basically the same as in normal subscription procedure but timeout can come only in route create during merge operation.
206 If error happens during route create, Subscription Manager drops the RIC Subscription Request message and xApp does not get any response.
210 xApp may resend the same request if there is no response in expected time. If xApp resends the same request while processing of previous
211 request has not been completed in Subscription Manager then Subscription Manager drops the new request, makes a log writing and continues
212 processing previous request.
214 * Subscription delete merge procedure
218 xApp sends RIC Subscription Delete Request message to Subscription Manager. If delete concerns merged subscription, Subscription Manager
219 responds with RIC Subscription Delete Response to xApp and then sends route delete request to Routing manager.
221 Subscription Manager supervises route delete with a timer.
223 .. image:: images/Successful_Subscription_Delete_Merge_ASN.1.png
225 :alt: Successful subscription delete merge picture
229 Delete procedure cannot fail from xApp point of view. Subscription Manager responds with RIC Subscription Delete Response message to xApp.
231 * Timeout in Subscription Manager
233 Timeout can only happen in route delete to Routing manager. Subscription Manager responds with RIC Subscription Delete Response message to xApp.
237 xApp may resend the same request if there is no response in expected time. If xApp resends the same request while processing of previous
238 request has not been completed in Subscription Manager then Subscription Manager drops the new request, makes a log writing and continues
239 processing previous request.
243 If Subscription Manager receives unknown message, Subscription Manager drops the message.
247 When xApp is restarted for any reason it may resend subscription requests for subscriptions which have already been subscribed. If REPORT or INSERT type
248 subscription already exists and RMR endpoint of requesting xApp is attached to subscription then successful response is sent to xApp directly without
249 updating Routing Manager and BTS. If POLICY type subscription already exists, request is forwarded to BTS and successful response is sent to xApp.
250 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.
251 RMR message routing uses domain service address name.
253 * Subscription Manager restart
255 Subscription Manager stores successfully described subscriptions from db (SDL). Subscriptions are restored from db in restart. For subscriptions which
256 were not successfully completed, Subscription Manager sends delete request to BTS and removes routes created for those. Restoring subscriptions from
257 db can be disable via submgr-config.yaml file by setting "readSubsFromDb": "false".
261 Subscription Manager adds following statistic counters:
263 Subscription create counters:
264 - SubReqFromXapp: The total number of SubscriptionRequest messages received from xApp
265 - SubRespToXapp: The total number of SubscriptionResponse messages sent to xApp
266 - SubFailToXapp: The total number of SubscriptionFailure messages sent to xApp
267 - SubReqToE2: The total number of SubscriptionRequest messages sent to E2Term
268 - SubReReqToE2: The total number of SubscriptionRequest messages resent to E2Term
269 - SubRespFromE2: The total number of SubscriptionResponse messages from E2Term
270 - SubFailFromE2: The total number of SubscriptionFailure messages from E2Term
271 - SubReqTimerExpiry: The total number of SubscriptionRequest timer expires
272 - RouteCreateFail: The total number of subscription route create failure
273 - RouteCreateUpdateFail: The total number of subscription route create update failure
274 - MergedSubscriptions: The total number of merged Subscriptions
276 Subscription delete counters:
277 - SubDelReqFromXapp: The total number of SubscriptionDeleteResponse messages received from xApp
278 - SubDelRespToXapp: The total number of SubscriptionDeleteResponse messages sent to xApp
279 - SubDelReqToE2: The total number of SubscriptionDeleteRequest messages sent to E2Term
280 - SubDelReReqToE2: The total number of SubscriptionDeleteRequest messages resent to E2Term
281 - SubDelRespFromE2: The total number of SubscriptionDeleteResponse messages from E2Term
282 - SubDelFailFromE2: The total number of SubscriptionDeleteFailure messages from E2Term
283 - SubDelReqTimerExpiry: The total number of SubscriptionDeleteRequest timer expires
284 - RouteDeleteFail: The total number of subscription route delete failure
285 - RouteDeleteUpdateFail: The total number of subscription route delete update failure
286 - UnmergedSubscriptions: The total number of unmerged Subscriptions
288 SDL failure counters:
289 - SDLWriteFailure: The total number of SDL write failures
290 - SDLReadFailure: The total number of SDL read failures
291 - SDLRemoveFailure: The total number of SDL read failures
293 Configurable parameters
294 -----------------------
295 Subscription Manager has following configurable parameters.
296 - Retry timeout for RIC Subscription Request message
297 - e2tSubReqTimeout_ms: 2000 is the default value
299 - Retry timeout for RIC Subscription Delete Request message
300 - e2tSubDelReqTime_ms: 2000 is the default value
302 - Waiting time for RIC Subscription Response and RIC Subscription Delete Response messages
303 - e2tRecvMsgTimeout_ms: 2000 is the default value
305 - Try count for RIC Subscription Request message
306 - e2tMaxSubReqTryCount: 2 is the default value
308 - Try count for RIC Subscription Delete Request message
309 - e2tMaxSubDelReqTryCount: 2 is the default value
311 - Are subscriptions read from database in Subscription Manager startup
312 - readSubsFromDb: "true" is the default value
314 The parameters can be changed on the fly via Kubernetes Configmap. Default parameters values are defined in Helm chart
316 Use following command to open Subscription Manager's Configmap in Nano editor. Firts change parameter and then store the
317 change by pressing first Ctrl + o. Close editor by pressing the Ctrl + x. The change is visible in Subscription Manager's
318 log after some 20 - 30 seconds.
322 KUBE_EDITOR="nano" kubectl edit cm configmap-ricplt-submgr-submgrcfg -n ricplt
324 REST interface for debugging and testing
325 ----------------------------------------
326 Give following commands to get Subscription Manager pod's IP address
330 kubectl get pods -A | grep submgr
332 ricplt submgr-75bccb84b6-n9vnt 1/1 Running 0 81m
334 Syntax: kubectl exec -t -n ricplt <add-submgr-pod-name> -- cat /etc/hosts | grep submgr | awk '{print $1}'
336 Example: kubectl exec -t -n ricplt submgr-75bccb84b6-n9vnt -- cat /etc/hosts | grep submgr | awk '{print $1}'
344 Example: curl -s GET "http://10.244.0.181:8080/ric/v1/metrics"
350 Example: curl -X GET "http://10.244.0.181:8088/ric/v1/subscriptions"
352 Delete single subscription from db
356 Syntax: curl -X POST "http://10.244.0.181:8080/ric/v1/test/deletesubid={SubscriptionId}"
358 Example: curl -X POST "http://10.244.0.181:8080/ric/v1/test/deletesubid=1"
360 Remove all subscriptions from db
364 Example: curl -X POST "http://10.244.0.181:8080/ric/v1/test/emptydb"
366 Make Subscription Manager restart
370 Example: curl -X POST "http://10.244.0.181:8080/ric/v1/test/restart"
372 Use this command to get Subscription Manager's log writings
376 Example: kubectl logs -n ricplt submgr-75bccb84b6-n9vnt
378 Logger level in configmap.yaml file in Helm chart is by default 2. It means that only info logs are printed.
379 To see debug log writings it has to be changed to 4.
386 RAN services explained
387 ----------------------
388 RIC hosted xApps may use the following RAN services from a RAN node:
390 * 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
391 * 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
392 * CONTROL: RIC sends a Control message to RAN to initiate or resume call processing in RAN
393 * POLICY: RIC requests that RAN executes a specific POLICY during call processing in RAN after each occurrence of a defined SUBSCRIPTION
395 Supported E2 procedures and RAN services
396 ----------------------------------------
397 * RIC Subscription procedure with following RIC action types:
403 * RIC Subscription Delete procedure
405 * Merge and delete of equal REPORT type subscriptions.
407 Recommendations for xApps
408 -------------------------
410 * Recommended retry delay in xApp
412 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
413 seconds. Subscription Manager makes one retry by default. There can be only one ongoing request towards per RAN other requests are queued in Subscription