Experience & Lessons of SKT-CU Packet Data Roaming December, 2003 Bryan Kim (kkh0623@nate)

1. Experience & Lessons of SKT-CU Packet Data Roaming December, 2003 Bryan Kim (kkh0623@nate.com)

2. Outline ■ SKT-CU Packet Data Roaming Summary ■ SKT Outbound on CU ■ Cu Outbound on SKT ■ Lessons ■ Q&A

3. SKT-CU Packet Data Roaming Summary

4. SKT-CU Packet Data Roaming Summary ■ Service Type - WAP Access Service (Home WAP G/W Access only) ; Photo mail, Ring tone download, Stock trading etc - Internet Access Service (with laptop or PDA) ■ IP Network - Direct Connection (IP sec between B/Gs will be set up soon) - Simple IP only - L2TP between SKT and CU for CU customers (Dual Authentication w/o LCP Re-Negotiation) ■ Service launch - SKT O/B on CU : 7th, Nov - CU O/B on SKT : Middle of Dec.(TBD)

5. SKT O/B on CU

6. Requirement ■ China Unicom - PDSN Route authentication/accounting messages to CU Central AAA - Central AAA Authenticate SKT roamers locally (not proxy) Load SKT username/password(WAP, Internet Access, PDA) Proxy accounting messages to SKT proxy AAA based on IMSI(IRM) - Border G/W IPsec with SKT Border G/W (TBD) ■ SK Telecom - Proxy AAA Receive accounting data from CU and transfer to SKT billing center - SKT billing center Charge for data roaming and make settlement data

7. BTS BSC WAP G/W Billing Center Billing Center Authentication WAP Internet Access Service Network Configuration; Public WAP G/W IP address China Unicom SK Telecom Internet Border G/W (IPsec) Border G/W (IPsec) PDSN SKT WAP G/W DNS Query DNS Central AAA Proxy AAA Accounting

8. Home WAP G/W Access; Public WAP G/W IP Address SKT Roamer MS CU PDSN CU DNS CU AAA CU Border G/W SKT Border G/W SKT AAA SKT WAP G/W LCP Conf. Req/Ack (with Auth option) Because SKT using common username/password there is no problem to authenticate subscribers not at the Home but at the serving network. PAP Request (or CHAP Challenge) with NAI Access Request Access Accept PAP Ack IPCP Conf. Req/Ack (Public IP address assignment from CU PDSN) Account Req/Res(start) DNS Query (with wgw.nate.com) SKT WAP G/W Public IP address acquisition Connection LCP Term.Req/Ack Account Req/Res(stop)

9. CU O/B on SKT

10. Requirement ■ SK Telecom - PDSN Because of private WAP G/W IP address in CU handsets SKT PDSN should make L2TP For L2TP, SKT private PDSN IP address should be changed to Public IP address in the SKT F/W - AAA Authenticate CU roamers locally (not proxy) Proxy accounting data to CU central AAA based on IRM (CU username does not have realm, e.g ‘wap’, ‘wap2.0’) ■ China Unicom - Border Gateway : Should work as LNS

11. BTS BSC WAP G/W Network Configuration; Private WAP G/W IP address SK Telecom China Unicom NAT Function PDSN(LAC) LNS Internet L2TP Border G/W Border G/W Proxy AAA UDA Central AAA AAA Billing Center Billing Center Internet Access Service with laptop Accounting WAP UDA(User Data Aggregator) Authentication

12. Home WAP G/W Access; Dual Authentication w/o LCP Re-Negotiation CU Roamer MS SKT PDSN (LAC) SKT AAA CU G/W(LNS) CU AAA CU WAP G/W LCP Conf. Req/Ack (with Auth option) Tunnel attribute Tunnel Type : L2TP LNS IP : 220.xx.xx.x Tunnel Password : CUSKT CU LNS has RADIS client function but authenticates locally PAP Request (or CHAP Challenge) with NAI Access Request Access Accept (with LNS IP address) SCCRQ/SCCRP SCCCN L2TP ICRQ /ICRP ICCN (LCP forwarding) Account Req/Res(start) Account Req/Res(start) PAP Ack SLI Hello IPCP Conf. Req/Ack Connection

13. Lessons

14. Lessons ■ Data roaming concept on packet data platform (handset, G/W, billing system) - UA(User Agent) - MIN-MDN-IRM Mapping ■ WAP G/W IP address ■ Packet volume based flat rate in the data roaming environment ■ L2TP tunneling option : some handsets seem unable to support LCP re-negotiation ■ NAI Format : aaa@bbb.com ■ Roaming location based contents (SID)

15. Questions & Answers Presented by Bryan Kim kkh0623@nate.com