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NATs & Firewalls
The General SIP Proxy Firewall
Prepared for: Spring VON 2003
By: Karl Erik Ståhl
President Intertex Data AB
Chairman Ingate Systems AB
© 2003 Intertex Data AB 1
IP PhoneIP Phone
IP Phone
IP Phone
Internet
SOHO LANEnterprise LAN
We have a “new” network
XP
PIM
But do we use it for person to person communication?
Everyone has a connection…
Operator Network
© 2003 Ingate Systems AB© 2003 Intertex Data AB 3
VoIP as we have seen it…
PSTN
But no connectivity between the IP clouds!
Europe
IP
US
VPNTunnel
IP
Gateway
Gateway
Gateway
TollBypass
SOFTSWITCH
MGCP
© 2003 Ingate Systems AB© 2003 Intertex Data AB 4
What about universal connectivity?
Wouldn’t that be fine?
Black Phone
RJ45
LAN Intranet Internet
IP Phone
PSTN
RJ11
IP PhoneIP Phone
IP Phone
IP Phone
PSTN
SIP/PSTNGateway
Internet
SOHO LANBusiness LAN
SIPServer
IAP
XP
PIM
Firewall/NAT problems!
DSLCableMTU
Operator network with NAT
NATFirewall
NAT
Status until recently:SIP is the Protocol for IP Communication Person to Person,BUT IT DOES NOT REACH THE EDGE!
So, why don’t we just connect?
© 2003 Ingate Systems AB© 2003 Intertex Data AB 6
What is the difference?
Typical Internet protocol (SMTP, HTTP…)
Internet
HOSTSERVER
SIP (and H.323…) connects person to person
Internet
PERSONPERSON
Locate the person - Set up a session - Open real time media streams
© 2003 Ingate Systems AB© 2003 Intertex Data AB 7
SIP Firewall Problems
Firewall Problems:
Sessions initiated from outside the firewall
- OK, open port 5060, but…
Media streams on dynamically allocated port numbers
- Ooops… !Even with public IP addresses inside
© 2003 Ingate Systems AB© 2003 Intertex Data AB 8
SIP NAT/PAT Problems
NAT & PAT Problems:Where is the device?
- Registration/location function
Private IP addresses and ports in SIP messages
- Rewrite with globally routable addresses
IP address and port of media stream has to be modified
- NAT engine has to be dynamically controlled
Worse with privateIP addresses inside
© 2003 Ingate Systems AB© 2003 Intertex Data AB 9
Suggested Solutions
Dynamically controlled Firewall/NATs
Midcom: By Firewall Control Proxy (IETF work)
uPnP: By the client (Windows)
SIP aware Firewall/NATs (SIP Proxy + Registrar)
General, handles complex scenarios
[Intertex (SOHO), Ingate (enterprise), …]
SIP aware Firewall/NATs (SIP ALG – non Proxy)
TLS not possible
STUN - Can cope with certain types of existing NATs
SIP clients need to get STUN into their SIP stacks
Requires STUN servers on the net, RTCP is lost
Tunnelling - Connects SIP clients to an operator or a corporate LAN
Requires ALG for each client with NATed address
Tunnels by IPSec or proprietary
© 2003 Ingate Systems AB© 2003 Intertex Data AB 10
Adding General SIP Traversal to a Firewall
Important components:Firewall & NAT
Dynamic Firewall Engine
SIPProxy
SIP Proxy Server, controlling the firewall
UserLocation
SIP Registrar, user location information
FirewallControl
Protocol Communication between
SIP Proxy and firewall
Firewall/NAT problems!
Firewall/NAT SIP transparency!
Office or home LAN
IP PhoneIP Phone
IP Phone
IP Phone
SIPServer PSTN
SIP/PSTNGateway
Operator network with NAT
Internet
NATFirewall
NAT
Enterprise LAN
DSLCableMTU
DMZinGateSIParator
SIP Enabling the Private Networks
inGateFirewall
IP Phone IP Phone
IP Phone
SELECT
SET ALT CFG E T 1
A I
R
U S B
E T 2
W A N
T X D
R X D
ADR CFG DHP RST LQ
TX RX
SC IX66
IAP
© 2003 Ingate Systems AB© 2003 Intertex Data AB 12
What have we got?
Important components:Firewall & NAT
Dynamic Firewall Engine
SIPProxy
SIP Proxy Server, controlling the firewall
UserLocation
SIP Registrar, user location information
FirewallControl
Protocol Communication between
SIP Proxy and firewall
In the Ingate and Intertex products:
You’ve got a SIP server!Use it just for firewall traversalAND/OR as your
- SIP Server - Outgoing proxy- Inbound proxy
InternetJust Another Internet Service…
Enterprise LAN
XP
inGateFirewall
PSTNSIP/PSTNGateway
DNSSRV
DMZinGateSIParator
XP
Ingate Linköping LAN
IX66
Intertex Stockholm LAN
Sweden
IX66
FWD Booth #301
IX66SIP Forum Booth #210 USA
Sweden
IX66
Home Office UsersSOHO LAN
IX66
XP
San Jose
Booth#520
14
IP Communications Using IP NetworksIP Communications Using IP Networks
• Intranet IP VPN with IP communications• Domestic and global IP communications• PBX and PSTN – E.164 resolution
Customer Customer PremisesPremises
PBX PSTN Phone
ManagedServices
Router
Vmail OSS
SIP Phone
WorldComPSTN
DialingPlans
Network GWY
Conf
PSTN Phone
IM
IN
EnterpriseGateway
SIP Routing
Firewall
SIP Server
IP VPN
Global IP Comm
Intranet IP Comm
…other…
Many call routing options:• Private/Public IP address• DNS and DNS SRV records• SIP aware NAT/PAT servers
Henry Sinnreich 4/10/2002
WorldComPublic
IP Network
15
IP Communications Using IP NetworksIP Communications Using IP Networks
PBX PSTN Phone
ManagedServices
Router
Vmail OSS
SIP Phone
WorldComPSTN
DialingPlans
Network GWY
Conf
PSTN Phone
IM
IN
EnterpriseGateway
SIP Routing
Firewall
SIP Server
IP VPN
Global IP Comm
Intranet IP Comm
…other…
Integration with existing phones
SIP Capable FirewallIngate and IntertexFirst through SIT
Customer Customer PremisesPremises
No IP PBX Needed!
Enhanced Functionality
Enterprise LAN
WorldComPublic
IP Network
Firewall
PresenceIM
GreenwichEdge Proxy
DMZMicrosoft GreenwichHome Server:PresenceIMAudioVideoData Col.
TLS
© 2003 Ingate Systems AB© 2003 Intertex Data AB 17
Product Examples – Ingate Systems AB
Complete Firewalls Add-on to Existing Firewalls
Firewall & NAT/PAT SIP Proxy SIP Registrar
Enterprise Products
DMZ
Existing Firewall
SIParator
© 2003 Ingate Systems AB© 2003 Intertex Data AB 18
Product Examples – Intertex Data AB
IX66 Internet Gate with or withoutADSL modem built-in
OEM as: Telia SurfinBird Gate PowerBit SafeGateReview at: www.adslguide.org.uk/hardware/reviews/2002/q1/intertex_ix66-edflc.asp
SOHO Products
© 2003 Ingate Systems AB© 2003 Intertex Data AB 19
The Intertex IX66 Internet Gate
A closer look
Firewall & NAT/PAT Router SIP Proxy and Registrar DHCP Server and Client WEB Server for configuration Smart Card Reader for security applications Optional 802.11b Wireless Lan SIP Appliance Control, LAC via expansion port
SELECT
SET ALT CFG E T 1
A I
R
U S B
E T 2
W A N
T X D
R X D
ADR CFG DHP RST LQ
TX RX
SC
Optional ADSLand Splitter Built-in
© 2003 Ingate Systems AB© 2003 Intertex Data AB 20
SIP Capable Firewalls!
Ingate Systems ABwww.ingate.comBox 10013, Slakthusplan 4 SE-121 26 Stockholm, SwedenCEO Olle [email protected] Tel +46 8 6007750
Intertex Data ABwww.intertex.seRissneleden 45 SE-174 44 Sundbyberg, SwedenPresident Karl Erik Stå[email protected] Tel +46 8 6282828
