• Table of contents
• EPDG implementation plan
  • The big picture
  • Control Plane
  • User Plane
  • Authentication
  • 3GPP Interfaces and Procedures
    • ePDG
      • S2b to PGW (GTPv2C) [TS 29.274]
      • SWm to AAA (DIAMETER) [3GPP TS 29.273]
      • SWu to UE (IKEv2, ESP) [3GPP TS 33.402]
      • Gxb to PCRF (not needed?)
    • 3GPP AAA Server
      • SWx to HSS (DIAMETER) [3GPP TS 29.273 sec 8, 3GPP TS 23.402 sec 12]
      • S6b to PGW (DIAMETER) [3GPP TS 29.273 sec 9]
      • SWm to ePDG (DIAMETER)
    • custom Interfaces / Procedures
      • CEAI

EPDG implementation plan¶

The big picture¶

Ideally, we want to reuse existing code whenever possible, rather than reinvent the wheel. Time will tell, if this works out or if we have to rewrite more of it.

• StrongSwan charon for handling IKEv2 and managing the IPsec SAs in the kernel IPsec
• Erlang DIAMETER application for all the related interfaces
• Erlang gtplib for S2b

This means we will have two major "applications" running:

• charon
• ePDG (likely in Erlang)

Between those two we will need some kind of non-standard, custom interface. For now I've called it "CEAI" for (Charon External AKA Interface)

Control Plane¶

• red color indicates elements / interfaces to be implemented.

User Plane¶

• red color indicates elements / interfaces to be implemented.
• blue color indicates control-plane elements controlling the user plane

Authentication¶

3GPP Interfaces and Procedures¶

ePDG¶

S2b to PGW (GTPv2C) [TS 29.274]¶

Create Session Request / Response¶

Delete Session Request / Response¶

Modify Bearer Request / Respone (not needed?)¶

Modify Bearere Command (not needed?)¶

Bearer Resource Command (not needed?)¶

Create Bearer Request / Response¶

Update Bearer Request / Response (not needed?)¶

SWm to AAA (DIAMETER) [3GPP TS 29.273]¶

Diameter-EAP-Request (DER) / Diameter-EAP-Response (DEA)¶

Diameter-AA-Request (AAR) / Diameter-AA-Response (AAA)¶

Session-Termination-Request (STR) / Session-Termination-Answer (STA)¶

Re-Auth-Requst (RAR) / Re-Auth-Answer (RAA)¶

Abort-Session-Request (ASR) / Abort-Session-Answer (ASA)¶

SWu to UE (IKEv2, ESP) [3GPP TS 33.402]¶

• Related: https://fabricioapps.blogspot.com/2017/10/untrusted-non-3gpp-ip-access-swu-ikev2.html

Gxb to PCRF (not needed?)¶

3GPP AAA Server¶

SWx to HSS (DIAMETER) [3GPP TS 29.273 sec 8, 3GPP TS 23.402 sec 12]¶

Push-Profile-Request (PPR) / Push-Profile-Answer (PPA)¶

Registration-Termination-Request (RTR) / Registration-Termination-Answer (RTA)¶

Multimedia-Auth-Request (MAR) / Multimedia-Auth-Answer (MAA)¶

• 3GPP TS 29.273 8.2.2.1
• https://www.etsi.org/deliver/etsi_ts/129200_129299/129273/17.06.00_60/ts_129273v170600p.pdf
• https://dstest.info/DiaDict/Dictionary/Multimedia-Auth-Request_SWx.html

Server-Assignment-Request (SAR) / Server-Assignment-Answer (SAA)¶

S6b to PGW (DIAMETER) [3GPP TS 29.273 sec 9]¶

• https://osmocom.org/issues/6229

SWm to ePDG (DIAMETER)¶

see above.

custom Interfaces / Procedures¶

CEAI¶

FIXME