Roles of Session Border Controllers in IMS Networks
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Transcript of Roles of Session Border Controllers in IMS Networks
June 2006
Roles of Session Border Roles of Session Border Controllers in IMS NetworksControllers in IMS Networks
CANTO - June 2006
Agenda
Session Border ControllersWhat is an SBC?Why are Service Providers using them today?
IP Multimedia Subsystem (IMS)What is IMS?Why are Service Providers evolving to IMS?
SBC’s in IMS NetworksWhat functions do they provide in the IMS Network?How will SBC’s evolve within the IMS architecture?
ConclusionsSummaryReferences
SBC Role Today - ‘Session Aware’
Core SIPInfrastructure
SessionBorder
Controller
SIP NormalizationIPv6 / VLAN
Topology Hiding
DoS Prevention
Firewall/NATLoad Balancing
Session QoSSimplify, Protect and Offload
AccessNetwork
PeeringNetwork
Firewall/NAT Traversal
Firewalls/NATs
SIP Services:• SIP Proxy• Application Server• Media Server
SessionController
SIPEndpoints
Solves Firewall/NAT traversal from within the service provider network – Do not have to replace existing firewalls/NATs Offloads SIP Proxy – up to 20,000 re-registers a second
AccessNetworks
Sim
plify
& O
ffloa
d
DoS Attack Prevention
Provides protection against Denial of Service (DoS) attacks in the form of SIP signallingProvides policing of individual media sessions
Example – Users Signal G.711 (voice) call, but transmit video RTP session -> Maintaining QoS for other users
AccessNetwork
CoreNetwork
SIPServices
SessionController
Prot
ect
Topology Hiding
Provides protection against Denial of Service (DoS) by hiding internal IP addressingRemoves sensitive IP addressing and domain names from SIP headers and SDP
AccessNetwork
SIPServices
SessionController
Prot
ect
PeeringNetwork
200.2.x.x17.3.x.x
110.5.x.x
What is IMS?IMS = IP Multimedia SubsystemIMS is a network architecture that uses SIP to provide multimedia services over IPIMS is a technology which provides fixed/mobile network convergenceLayered architecture that separates transport (media), control (signalling) and application functions
What is TISPAN?Telecoms and Internet converged Services & Protocols for Advanced Networks)Standardize the migration of PSTN networks to a converged network using IMS as the core architecture
Who gains from Fixed/Mobile Convergence?
Service ProvidersOptimized ‘all IP’ network reduces OPEXOpens the fixed market’s customers to mobile operators and vice versa. New revenue streams – ability to charge for services
End UsersCommon service set available regardless of the device, the location the access mediumNew services available – location basedApplications become more appealing with large subscriber base (Metcalfe’s Law)
Logical separationof applications & network elements• Rapid application development• No vertical silo solutions
IMS Basics…
IMS bringsEnhancements to…
User profiles
Security Roaming
QoS policycontrol
CallControl
SessionDetail
Records
IMS architecture• Functional separation• Open Interfaces
SIP
Based on SIP
IMS Network Characteristics
Access Independent – SIP over IP (Extensions for Mobile)Open Architecture - Functional Elements Integrated through Open InterfacesSecurity at Network Boundaries – Protect IMS InfrastructureRoaming – User gets same apps in Home or Visited Network
Scal
able
Arc
hite
ctur
e IMSNetworkAccess
Network
AccessNetwork
Peering IMS
Network
IP
MobileNetwork HSS HSS
SBC Features
NAT/Firewall TraversalProtocol NormalizationProtocol InterworkingVLANsGeographic Resilience
DoS ProtectionRate LimitingTopology HidingEncryption
Policy EnforcementPolicingSession Admission ControlLegal InterceptEmergency Call Handling
Call Detail RecordsEMSSNMP
ManagementSecurity
Simplify and Protect PSTN Equivalence
IMS/TISPANRequirement
Within IMS Scope
IMS Architecture with SBC’s
I-CSCF *
P-CSCF
S-CSCF
HSS
BGCF
MGCF
VisitedNetwork
(Originator)
HomeNetwork
(Originator)
GSTN
MG
I-CSCFS-CSCF
HSS
BGCF
MGCF
MG
GSTN
IP-CAN
UE
P-CSCF
HomeNetwork
(Terminating)
PSTN Switches
PSTN Switches
P-CSCF
IP-CAN
UE
IP-CAN
Registration
I-CSCF
Session Set up
THIG
SGSG
UE
VisitedNetwork
(Terminating)
• Directs Users to Home Network
•NAT/FW Traversal
•Emergency Call Handling
• HSS service lookup to
select S-CSCF
= SBC
TISPAN architecture – SBC MediaDSL access, WLAN etc
I-CSCF
S-CSCF
HSS
BGCF
MGCF
I BCF
HomeNetwork
(Originator)
GSTN
MG
PSTN Switches
UE
IP-CAN C-BGF
P-CSCF I-BGF
RegistrationSession Set up= SBC
Media path
• Session Policing• Legal Intercept
• IPv4 to IPv6• Session Admission Control
• DSCP QoS Re-mapping• Topology Hiding
SBC Migration to IMS
SignallingFunctionsSIP
MediaFunctions
ME
GA
CO
/H.2
48
RTP/RTCP
Control Plane
Media Plane
SignallingSBC
MediaSBCMedia
Functions
SignallingFunctions
ME
GA
CO
/H.2
48
MediaSBC
H.2
48
H.248
1:N and N:1 models SCTP (standardized signalling transport)Signalling compression
Separate signalling & media functionsIndependently scale signalling and media
Physically separate the product architectureSignalling encryption IPSec/TLS
Benefits of Split Signalling & MediaEmerging standards for converged networks (IMS, TISPAN, etc) dictate that separation is requiredMedia functions can be deployed at the network edge, saving $$ required to backhaul the media traffic to a central locationPhysical locations can scale their signalling and media independently – Allows for flexible deploymentIntegrated SBC deployments can be upgraded to Distributed configurations at any time with total reuse of hardware
SignallingSBC
MediaSBC
MediaSBC
H.248 H.2
48
Signalling
Media
H.2
48 SignallingMedia
Standards Organizations3GPP - Defined IP Multimedia Subsystem (IMS)
http://www.3gpp.org/
ETSI TISPAN - Defining migration to IMS for Wireline networks
http://www.etsi.org/
3GPP 2 - IMS for CDMAhttp://www.3gpp2.org/
MultiService Forum (MSF)http://www.msforum.org/
Open Mobile Alliance (OMA)http://www.openmobilealliance.org/
Internet Engineering Task Force (IETF)http://www.ietf.org
Conclusions
Service Providers are moving to IMS/TISPAN architectures Service Providers should invest in SBC’s that are forward compatible with IMS
SBC architecture that supports signaling and media separation is required
Today, SBC’s provide a greater set of features, than IMS requirements define
Terminology3GPP 3rd Generation Partnership ProjectA-RACF Access Resource Admission Control FunctionAUC Authentication CentreBGCF Breakout Gateway Control FunctionC-BGF Access/Core Border Gateway FunctionGSTN Global Switched Telephony NetworkHSS Home Subscriber ServerIBCF Interconnect Border Control FunctionI-BGF Interconnection Border Gateway FunctionI-CSCF Interrogating Call Session Control FunctionIP-CAN IP Connectivity Access NetworkIMS IP Multimedia SubsystemMGCF Media Gateway Control FunctionNAPT Network Address and Port TranslationP-CSCF Proxy Call Session Control FunctionPDF Policy Decision FunctionQoS Quality of ServiceRCEF Resource Control Enforcement FunctionSBC Session Border ControllerS-CSCF Serving Call Session Control FunctionSPDF Service Based Policy Decision FunctionTHIG Topology Hiding Inter Network GatewayUE User Element
SBC Signalling Functions
In 3GPP wireless networks the SBC Signalling requirements are:
Proxy Call Session Control Function P-CSCF functionInterrogating Call Session Control Function (I-CSCF)Can perform Topology Hiding Interconnect Gateway (THIG) functions where requiredContains a Policy Decision Function which can be externalized if required
In TISPAN Converged networks the SBC Signalling requirements are:
An Interconnect Border Control Function when interconnecting networksIn TISPAN the PDF is defined as SPDF (Service based Policy Decision Function)
P CSCFPDF
IBCF
SBC Signalling Functions
THIG
H.248 Control of Media Plane
Diameter / XML to external policy databases
= 3GPP defined function
= TISPAN defined function
I CSCF
SBC Media Functions
Currently Null function in 3GPPIn TISPAN architectures performs
Access to Core Border Gateway Function (CBGF)Interconnect Border Gateway Function (IBGF)
I / C BGF
SBC Media Functions
H.248 Control of Media Plane
= 3GPP defined function
= TISPAN defined function
TISPAN architecture with SBC’s
UE
I-CSCF*
I BCF I BCFP-CSCF
S-CSCF
HSS
BGCF
MGCF
I BCF
Home Network(Originator)
GSTN
MG
THIG I-CSCF*S-CSCF
HSS
BGCF
MGCF
MG
THIG
I BCF
GSTN
IP-CAN
UE
P-CSCFI BCF
Home Network(Terminator)
PSTN Switches
PSTN Switches
P-CSCF
IP-CAN
UE
IP-CAN
VisitedNetwork
(Originator)
VisitedNetwork
(Terminating)
RegistrationSession Set up= SBC
SIP-I