Roaming SMS

http//www.netmanias.com/en/post/techdocs/5902/lte-security/lte-security-i-concept-and-authentication

You see the process involves 4 elements HSS, MME, eNB and UE (skip the details for later study)

The Home Subscriber Server holds the credentials - so this is your entry point. In 3GPP TS 23.002 on page 22 (content page number) you see the HSS holds

Location Information

http//www.etsi.org/deliver/etsi_ts/123000_123099/123002/13.06.00_60/ts_123002v130600p.pdf

Understanding the complete functions of the HSS is crucial -)

http//www.netmanias.com/en/post/techdocs/5902/lte-security/lte-security-i-concept-and-authentication

You see the process involves 4 elements HSS, MME, eNB and UE (skip the details for later study)

The Home Subscriber Server holds the credentials - so this is your entry point. In 3GPP TS 23.002 on page 22 (content page number) you see the HSS holds

Location Information

http//www.etsi.org/deliver/etsi_ts/123000_123099/123002/13.06.00_60/ts_123002v130600p.pdf

Understanding the complete functions of the HSS is crucial -)

Excellent Rolf and I agree with your conclusion.

The document clearly defines triplets are needed. That would be for roaming calls (e.g. MO/MT).

@wotsits - hang in with the HSS and its functions, see the European Telecommunications Standards Institute (ETSI) hosts the Technical Standard (TS) 129 336. From ETSI to 3GPP terminology just drop the '1' and you have the 3GPP classification TS 29.336 (belongs to the '29 series').

As ETSI and 3GPP interchange, 3GPP has the lead. GSM Asssociation (GSMA) plays minor role but in specific areas like eUICC.

Here the HSS in LTE Advanced Pro most accurate version

http//www.etsi.org/deliver/etsi_ts/129300_129399/129336/13.04.00_60/ts_129336v130400p.pdf

Just make sure to ALWAYS check the latest version of these standards. They highly change in detail.

Just found a 31C3 session of Tobias Engel about SS7 and aspects around (he is also a DNS crack)

https://www.youtube.com/watch?v=-wu_pO5Z7Pk

Be aware that nowadays Diameter runs beside SS7 in Core Networks and some issues are fixed -)