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Integrating 3G and WLAN Services in

NTP SIP-based VoIP Platform

Dr. Quincy Wu

National Telecommunications Program Office

Email: solomon@ipv6.club.tw

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Outline

• Introduction to NTP • NTP SIP-based VoIP Platform• NAT Traversal• Integrating WLAN and GPRS

network• Future Work

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NTP• National Telecommunications Development

Program– Established by the National Science Council (NSC) in

May, 1998. – Phase I: from 1998 to 2003.– Total budget: 350 million US$ in 5 years.

• Program Focuses– Wireless Communication – Broadband Internet– Application Services

• Mission– To conduct R&D in advanced telecommunication

technologies, for the promotion and development of telecommunication industry.

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NTP VoIP Platform

NTU PBX

Phone31842

Phone31924

Phone59237

Phone59238

SIP Phone0944003005SIP Phone

0944003004

PSTN Gateway

SIP Phone0944002002

Phone3213

Phone4100

Phone4454

Phone6818

Phone02-87730600

StationInterface

StationInterface

StationInterface

StationInterface

Phone03-5912312

Admin Console

SIP Phone0944003003

SIP Phone0944002003

Hsinchu

Taipei

TrunkInterface

03-5712121

02-23630231

TrunkInterface

Call Server

TANet

NCTU

PSTN

NTUEdge Router

Edge Router

NCTU PBX

SoftphoneWLANAP

Call Server PSTN GatewayWGSN

•IPTel SER•CCL Call Server

•Cisco 2621GW•CCL PSTN GW

•Pingtel•Snom•Cisco

•Siemens•Microsoft•CCL

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Academic Researches

Support academic researches on NTP VoIP Platform

• NTU: SIP Signaling Performance Evaluation on SCTP

• NTHU: Secure RTP and Location Privacy on VoIP System

• NDHU: Voice over IP study on All IP networks

• NCKU: DNS/ENUM Automatic Updating Mechanism

• NCTU: NAT Traversal & WGSN Project for Integrated Wireless VoIP Services

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Simple Traversal of UDP Through Network Address

Translators (STUN)

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Common Scenario in VoIP• UA1, UA3: User Agent behind NAT.

• UA2: SIP device outside NAT.

0944021401

sip.ipv6.club.tw

NAT

UA1

UA2IPv6 only

Proxy Server

0944021021

0944021403 UA3

IPv6 only

IPv6 only

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Network Address TranslatorComputer AIP: 10.0.0.1

Port: 80

Computer BIP: 10.0.0.2

Port: 80

NATPublic Internet

IP: 200.200.200.200Port: 10080

IP: 200.200.200.200Port: 20080

Mapping Table10.0.0.1:80 <-> 1008010.0.0.2:80 <-> 20080

DHCP Server

DHCP ClientPPPoE Client

Private NIC

Public NIC

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The Problem (1/2)• Because of its private address, the Via

header and Contact address in SIP messages sent by UA1 are incorrect.– With incorrect Via header, responses of

messages sent by UA1 cannot be routed back.

– With incorrect Contact address in REGISTER messages, call server cannot inform UA1 the incoming calls.

• UA1 can only act as a calling party.

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Incorrect REGISTER Message

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The Problem (2/2)• When UA1 initiate a call, the connection

information for media establishment in SDP are also incorrect.– The IP address in SDP is the private IP

address on UA1.– UA2 gets a private peer address, the RTP

packets from UA2 cannot be routed to UA1.– Media can only be sent from UA1 to UA2.

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Incorrect Fields in SDP of INVITE Message

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STUN (RFC 3489)• A mechanism for a socket behind NAT(s) to get its mapp

ed (IP,port) on Internet.• We build a STUN Server from Vovida’s open source cod

e to answer the queries from STUN clients.– Vovida STUN server 0.8RC

• Our server is stun.ipv6.club.tw

– We also implemented the “Binding Lifetime Discovery” algorithm in RFC 3489 so that a STUN client can determine how frequently it needs to refresh the binding.

• STUN mechanism in our SIP UA is developed from scratch, instead of the open source code.

• In addition to calling out, our SIP UA can also receives incoming calls.

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STUN Server• Allow clients to discover if it is behind a NAT,

what type of NAT it is, and the public address & port NAT will use.

• A Very Simple Protocol. Easy to implement. Little computing load.

ClientIP: 10.0.0.1Port: 5060

IP: 200.200.200.200Port: 12345 STUN Server

Port: 3478

NAT

Client wants to receive packets at port 5060

Send a query to STUN server from port 5060

STUN Server receives a packet from 200.200.200.200

port 12345

STUN Server sends a response to client, telling him that his public address

is 200.200.200.200 port 12345

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Use STUN for SIP Registration• Use port 5060 to send a packet to STUN Server• Receive public address & port mapped to client:5060

from STUN Server• Fill the SIP register message with client’s public address

& port, send to proxy server

IP: 140.113.131.72Port: 56540 STUN Server

Port: 3478

NAT

Proxy ServerPort: 5060

REGISTER sip:proxy.club.tw SIP/2.0Via: SIP/2.0/UDP 140.113.131.72:56540 From: Solomon <sip:solomon@proxy.club.tw:5060>To: Solomon <sip:solomon@proxy.club.tw:5060> …Contact: Solomon <sip:solomon@140.113.131.72:56540>…

ClientIP: 10.0.0.1Port: 5060

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Corrected SIP Message

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Use STUN for RTP

• Send two STUN queries from RTP port (9000 & 9002) to STUN Server

• Use replied public address & port in SDP

IP: 140.113.131.72Port: 56539Port: 56541

STUN ServerPort: 3478

NAT

Proxy ServerPort: 5060

INVITE ……Content-Type: application/sdp

c=IN IP4 140.113.131.72m=audio 56539 RTP/AVP 0 8 3 18m=video 56541 RTP/AVP 34 96

ClientIP: 10.0.0.1

RTP Port: 9000RTP Port: 9002

UARTP Port: 9000RTP Port: 9002

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Corrected SDP

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WLAN-based GPRS Support Node (WGSN)

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WGSN (WLAN-based GPRS Support Node) Architecture

HLR

GGSNSGSN WGSN

MS

PDN

ChargingGateway

BillingSystem

GaGa

Ga

Gr

GcGr

AP

AP

Node B Node B

Node B

Gi

Gi

UMTS

WLANCore Network

UTRAN

RNC

Gn

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WGSN Features• Service aspects

– SIP-based VoIP

• Access control and security aspects– SIM-based authentication

• Roaming aspects– Utilizing the standard UMTS mobility management

• Terminal aspects– A Windows laptop equipped with a smart card reader

• Naming and address aspects– International Mobile Subscriber Identity (IMSI)

• Charging and billing aspects– Offline charging and online charging based on Call Detail

Record (CDR)

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WGSN Protocol Stack

MS WGSN Node CN

Application

Transport

IP

802.11 802.11 Ethernet Ethernet

Application

Transport

IP

L2

AP

L2

L1 L1

IP

(a) WGSN Control Plane

(b) WGSN User Plane

IP

EAP-GMM

EAP

EAP-OL

802.11

EAP-OL

802.11L1

Ethernet

IP

UDP

RADIUS

L1

Ethernet

UDP

RADIUS

EAP

L1

MTP2

MTP3

SCCP

TCAP

MAP

L1

MTP2

MTP3

SCCP

TCAP

MAP

MS AP WGSN HLR

EAP-GMM

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The MS Architecture

I/O and Communication Modules

WGSN Client

SIM Module

User Interface

WLANModule

Smart CardReader Module

UICC

MS

NICModule

GPRSNetwork

Wireless LAN

GPRSModule

SIPUserAgent

GMM Module

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The WGSN Node Architecture

External Ethernet Module

MIB

LogHandler

SNMPAgent

AuthenticationCenter

WGSN Node

OA&M

iSMSAS SIP

Redirect

RASServer

SIP-basedPush Center

GMMHandler

GrHandlerBilling

Handler

SS7Module

NetworkController

DHCP Server

Firewall

GPRSModule

HLR

GPRSNetwork

Wireless LAN

SS7Network

Internal Ethernet Module

ExternalPDN

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Future Work

• OSA – Open Service Architecture

• IMS – IP Multimedia Subsystem

• IPv6 – IP Version 6

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Application Service Development Platform in Next Year

— Open Service Architecture

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CSCF

OSAHLR(HSS)

GPRS/3G

IP Multimedia Subsystem (IMS)

Phase I (now)

Phase II

Supported by other projects

Roaming NCTU PBX

NTU PBX

Phone31842

Phone31924

Phone59237

Phone59238

Call Server Media Gateway

SIP Phone0980355429SIP Phone

937250

Media Gateway

SIP Phone62002

Phone3213

Phone4100

Phone4454

Phone6818

Phone02-87730600

StationInterface

StationInterface

StationInterface

StationInterface

Phone03-5912312

Admin Console

Edge Route

Edge Route

SIP Phone937203

SIP Phone62003

Hsinchu

Taipei

TrunkInterface

03-5712121

02-23630231TrunkInterface

Call Server

NBEN

NBEN /SIP Network

PSTN

NBEN /SIP Network

ENUM

Campus WLAN

WLAN + Cellular IMS Architecture

WGSN

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Conclusion• By establishing a nation-wide VoIP testbed, NTP wish

es to promote the convergence of voice and data services and encourage advanced researches in Taiwan.

• SIP coverage in this year is approximately 50,000 users. NTP plans to double the coverage in 2004, and hopefully extend the connectivity with SIP.edu project in Internet2.

• STUN proves to be a good solution for non-symmetric NAT. We are still surveying mechanisms for traversing symmetric NAT.

• WGSN can be plugged in any 3G core network as being considered as a separate GPRS network. With the adoption of WGSN, it can help mobile operators facilitating the provisioning of WLAN and VoIP services.