Transcript Proxy Server

Integrating 3G and WLAN Services
in
NTP SIP-based VoIP Platform
Dr. Quincy Wu
National Telecommunications Program Office
Email: [email protected]
1
Outline
•
•
•
•
Introduction to NTP
NTP SIP-based VoIP Platform
NAT Traversal
Integrating WLAN and GPRS
network
• Future Work
2
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.
3
•Siemens
•Microsoft
•CCL
•Pingtel
•Snom
•Cisco
NTP VoIP Platform
•IPTel SER
•CCL Call Server
•Cisco 2621GW
•CCL PSTN GW
4
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
5
Simple Traversal of UDP
Through Network Address
Translators
(STUN)
6
Common Scenario in VoIP
• UA1, UA3: User Agent behind NAT.
• UA2: SIP device outside NAT.
Proxy Server
0944021403
UA3
sip.ipv6.club.tw
IPv6
only
0944021401
NAT
0944021021
UA1
UA2
IPv6
only
IPv6
only
7
Network Address Translator
Computer A
IP: 10.0.0.1
Port: 80
IP: 200.200.200.200
Port: 10080
NAT
Computer B
IP: 10.0.0.2
Port: 80
Public
Internet
IP: 200.200.200.200
Port: 20080
Public NIC
DHCP Client
PPPoE Client
Mapping Table
10.0.0.1:80 <-> 10080
10.0.0.2:80 <-> 20080
DHCP Server
Private NIC
8
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
10
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.
11
Incorrect Fields in SDP
of INVITE Message
12
STUN (RFC 3489)
• A mechanism for a socket behind NAT(s) to get its
mapped (IP,port) on Internet.
• We build a STUN Server from Vovida’s open source
code 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.
Client wants to receive
packets at port 5060
Send a query to STUN
server from port 5060
Client
IP: 10.0.0.1
Port: 5060
NAT
STUN Server receives a
packet from 200.200.200.200
port 12345
IP: 200.200.200.200
Port: 12345
STUN Server
Port: 3478
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
Client
IP: 10.0.0.1
Port: 5060
NAT
IP: 140.113.131.72
Port: 56540
REGISTER sip:proxy.club.tw SIP/2.0
Via: SIP/2.0/UDP 140.113.131.72:56540
From: Solomon <sip:[email protected]:5060>
To: Solomon <sip:[email protected]:5060>
…
Contact: Solomon
<sip:[email protected]:56540>
…
STUN Server
Port: 3478
Proxy Server
Port: 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
Client
IP: 10.0.0.1
RTP Port: 9000
RTP Port: 9002
NAT
INVITE …
…
Content-Type: application/sdp
c=IN IP4 140.113.131.72
m=audio 56539 RTP/AVP 0 8 3 18
m=video 56541 RTP/AVP 34 96
IP: 140.113.131.72
Port: 56539
Port: 56541
STUN Server
Port: 3478
Proxy Server
Port: 5060
UA
RTP Port: 9000
RTP Port: 9002
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Corrected SDP
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WLAN-based GPRS Support
Node (WGSN)
19
WGSN (WLAN-based GPRS
Support Node) Architecture
PDN
UMTS
Gi
HLR
Gr
Core Network
SGSN
Gn
Gi
Gr
Gc
WLAN
GGSN
WGSN
Ga
Ga
UTRAN
Ga
Charging
Gateway
AP
RNC
Billing
System
Node B
Node B
AP
Node B
MS
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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
EAP-GMM
EAP-GMM
EAP
EAP-OL
802.11
EAP-OL
EAP
MAP
MAP
RADIUS
RADIUS
TCAP
TCAP
UDP
UDP
SCCP
SCCP
IP
IP
MTP3
MTP3
Ethernet
Ethernet
MTP2
MTP2
L1
L1
L1
L1
802.11
AP
MS
HLR
WGSN
(a) WGSN Control Plane
Application
Application
Transport
Transport
IP
802.11
MS
IP
802.11
Ethernet
AP
IP
L2
L2
L1
L1
Ethernet
WGSN Node
(b) WGSN User Plane
CN
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The MS Architecture
MS
WGSN Client
User Interface
NIC
Module
WLAN
Module
GMM Module
SIP
User
Agent
SIM Module
Smart Card
Reader Module
GPRS
Module
UICC
I/O and Communication Modules
Wireless LAN
GPRS
Network
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The WGSN Node Architecture
WGSN Node
SIP-based
Push Center
RAS
iSMS Server
AS
SIP
Redirect
GPRS
Module
GPRS
Network
Network
Controller
OA&M
SNMP
Agent
Billing
Handler
Log
Handler
MIB
External Ethernet Module
Authentication
Center
DHCP Server
Firewall
GMM
Handler
Internal Ethernet Module
External
PDN
Wireless LAN
Gr
Handler
SS7
Module
SS7
Network
HLR
24
Future Work
• OSA – Open Service Architecture
• IMS – IP Multimedia Subsystem
• IPv6 – IP Version 6
25
Application Service Development Platform in Next Year
— Open Service Architecture
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WLAN + Cellular IMS Architecture
HLR
(HSS)
OSA
ENUM
CSCF
WGSN
Roaming
IP Multimedia
Subsystem (IMS)
Campus WLAN
GPRS/3G
Phase I (now)
Phase II
Supported by other projects
27
Conclusion
• By establishing a nation-wide VoIP testbed, NTP
wishes 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 nonsymmetric 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
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services.