Awesome

SGs

Minimal MSS SGs Server

This is a MSS SGs SCTP Server written in python3 that can be used with a MME to test some SGs features, like IMSI Attach, Location Update, SMS (Sending/Receiving/Alerting) or Paging (for SMS or CS-Fallback).

It is suitable to be used with one MME (only accepts the first SCTP connection) and one user (one IMSI/MSISDN). It can be easily changed to become a more functional MSS SGs server handling multiple SCTP connections and multiple users at the same time, but that is not currently supported.

I built this application to use it with my eNB app (that only supports one user) and an MME (which has the SGs configured to this SGs server).

In case of multiple users, the application will handle all messages initiated by the MME without any limitation. The only issue is the MSS SGs initiated procedures, in which there is a need to use an IMSI or TMSI. In those scenarios, the last received IMSI/TMSI will be used.

These are all the current SGs messages defined in 3GPP 29.118 specification: (not all of these messages are supported by the application)

#   SGs Messages Codes (29.118):
#
#1 SGsAP-PAGING-REQUEST               - from MSS to MME: Request <<<<<< ------------------- Can by sent by this app
#2 SGsAP-PAGING-REJECT                - from MME to MSS: Answer to 1 (no success)
#6 SGsAP-SERVICE-REQUEST              - from MME to MSS: Answer to 1 (success)
#7 SGsAP-DOWNLINK-UNITDATA            - from MSS to MME  <<<<<< --------------------------- Can by sent by this app
#8 SGsAP-UPLINK-UNITDATA              - from MME to MSS  >>>>>> --------------------------- Processed by this app
#9 SGsAP-LOCATION-UPDATE-REQUEST      - from MME to MSS: Request -------------------------- Processed by this app
#10 SGsAP-LOCATION-UPDATE-ACCEPT      - from MSS to MME: Answer to 9 (success)
#11 SGsAP-LOCATION-UPDATE-REJECT      - from MSS to MME: Answer to 9 (no success)
#12 SGsAP-TMSI-REALLOCATION-COMPLETE  - from MME to MSS: Answer to 10 (confirm new tmsi)
#13 SGsAP-ALERT-REQUEST..             - from MSS to MME: Request <<<<<< ------------------- Can by sent by this app
#14 SGsAP-ALERT-ACK                   - from MME to MSS: Answer to 13 (success)
#15 SGsAP-ALERT-REJECT                - from MME to MSS: Answer to 13 (no success)
#16 SGsAP-UE-ACTIVITY-INDICATION      - from MME to MSS: 
#17 SGsAP-EPS-DETACH-INDICATION       - from MME to MSS: Request >>>>>>
#18 SGsAP-EPS-DETACH-ACK              - from MSS to MME: Answer to 17
#19 SGsAP-IMSI-DETACH-INDICATION      - from MME to MSS: Request >>>>>>
#20 SGsAP-IMSI-DETACH-ACK             - from MSS to MME: Answer to 19
#21 SGsAP-RESET-INDICATION            - from MSS to MME: Request <<<<<< ------------------- Can by sent by this app
#22 SGsAP-RESET-ACK                   - from MME to MSS: Answer to 21
#23 SGsAP-SERVICE-ABORT-REQUEST       - from MSS to MME: 
#24 SGsAP-MO-CSFB-INDICATION          - from MME to MSS: 
#26 SGsAP-MM-INFORMATION-REQUEST      - from MMS to MME: Request <<<<<< ------------------- Can by sent by this app (sent in Location-Update procedure)
#27 SGsAP-RELEASE-REQUEST             - from MSS to MME
#29 SGsAP-STATUS                      - from MSS to MME:
#31 SGsAP-UE-UNREACHABLE              - from MME to MSS:

To start the application the only option we need to specify is the server IP:

root@ubuntu# python3 sctp_sgs.py -h
Usage: sctp_sgs.py [options]

Options:
  -h, --help            show this help message and exit
  -i MSS_IP, --ip=MSS_IP
                        MSS Local IP Address
root@ubuntu# 

When the application is started, these are the options available (as soon the MME establishes the SCTP connection with the server):

Choose one of the options:

	1. SMS Paging
	2. CS Paging
	3. Send SMS
	4. Send Alert
	5. Send Reset


	q. Quit

There are two variables in the code where we can define the MSS name and the operator name that is sent in the MM-INFORMATION-REQUEST.

This application only used modules from the python standard library.