Roles of Session Border
Controllers in IMS Networks
CANTO - June 2006
June 2006
Agenda
Session Border Controllers
What 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 Networks
What functions do they provide in the IMS Network?
How will SBC’s evolve within the IMS architecture?
Conclusions
Summary
References
SBC Role Today - ‘Session Aware’
Access
Network
SIP
Normalization
IPv6 / VLAN
Topology Hiding
DoS Prevention
Peering
Network
Firewall/NAT
Load Balancing
Session
Border
Controller
Core SIP
Infrastructure
Session QoS
Simplify, Protect and Offload
Simplify & Offload
Firewall/NAT Traversal
SIP Services:
Access
Networks
Firewalls/
SIP
Endpoints NATs
Session
Controller
• SIP Proxy
• Application Server
• Media Server
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
DoS Attack Prevention
SIP
Services
Protect
Access
Network
Core
Network
Session
Controller
Provides protection against Denial of Service (DoS)
attacks in the form of SIP signalling
Provides policing of individual media sessions
Example – Users Signal G.711 (voice) call, but transmit
video RTP session -> Maintaining QoS for other users
Topology Hiding
Session
Controller
Peering
Network
SIP
Services
17.3.x.x
Protect
200.2.x.x
Access
Network
110.5.x.x
Provides protection against Denial of Service (DoS)
by hiding internal IP addressing
Removes sensitive IP addressing and domain
names from SIP headers and SDP
What is IMS?
IMS = IP Multimedia Subsystem
IMS is a network architecture that uses SIP to provide
multimedia services over IP
IMS is a technology which provides fixed/mobile
network convergence
Layered 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
Catalyst for IMS Deployment
Who gains from Fixed/Mobile
Convergence?
Service Providers
Optimized ‘all IP’ network reduces OPEX
Opens the fixed market’s customers to mobile
operators and vice versa.
New revenue streams – ability to charge for
services
End Users
Common service set available regardless of
the device, the location the access medium
New services available – location based
Applications become more appealing with
large subscriber base (Metcalfe’s Law)
IMS Basics…
Based on SIP
User profiles
IMS architecture
• Functional separation
Roaming
Security
IMS brings
Enhancements to…
SIP
QoS
policy
control
Call
Control
Session
Detail
Records
• Open Interfaces
Logical separation
of applications &
network elements
• Rapid application
development
• No vertical silo
solutions
IMS Network Characteristics
Scalable Architecture
Mobile
Network
Access
Network
HSS
IP
IMS
Network
HSS
Peering
IMS
Network
Access
Network
Access Independent – SIP over IP (Extensions for Mobile)
Open Architecture - Functional Elements Integrated through
Open Interfaces
Security at Network Boundaries – Protect IMS Infrastructure
Roaming – User gets same apps in Home or Visited Network
SBC Features
Simplify and Protect
NAT/Firewall
Traversal
Protocol
Normalization
PSTN Equivalence
IMS/TISPAN
Requirement
Policy Enforcement
Policing
Session Admission
Control
Protocol Interworking
Legal Intercept
VLANs
Emergency Call
Handling
Geographic Resilience
Security
DoS Protection
Management
Rate Limiting
EMS
Topology Hiding
SNMP
Encryption
Call Detail Records
Within IMS Scope
IMS Architecture with SBC’s
• Directs Users to
Home Network
•NAT/FW Traversal
•Emergency Call
Handling
Home
Network
(Originator)
• HSS service
lookup to select
S-CSCF
S-CSCF
S-CSCF
THIG
P-CSCF
PDF
I-CSCF
P-CSCF
I-CSCF
I-CSCF *
PDF
Visited
Network
(Terminating)
HSS
HSS
Visited
Network
(Originator)
Home
Network
(Terminating)
BGCF
BGCF
P-CSCF
IP-CAN
MGCF
MGCF
SG
IP-CAN
SG
IP-CAN
MG
UE
UE
MG
UE
PSTN
Switches
PSTN
Switches
Registration
Session Set up
= SBC
GSTN
GSTN
TISPAN architecture – SBC Media
DSL access, WLAN etc
Home
Network
(Originator)
• DSCP QoS Re-mapping
• Topology Hiding
HSS
Media path
Registration
Session Set up
S-CSCF
I-CSCF
= SBC
I BCF
I-BGF
P-CSCF
BGCF
IP-CAN
C-BGF
MGCF
MG
UE
• Session Policing
• Legal Intercept
• IPv4 to IPv6
• Session Admission Control
PSTN
Switches
GSTN
SBC Migration to IMS
Media Plane
RTP/RTCP
Media
Functions
Signalling
Functions
Media
Functions
1:N and N:1 models
SCTP (standardized
signalling transport)
Signalling compression
Signalling
SBC
H.248
Control Plane
Signalling
Functions
MEGACO/H.248
SIP
Physically
separate the
product
architecture
Signalling
encryption
IPSec/TLS
MEGACO/H.248
Separate signalling
& media functions
Independently
scale signalling
and media
Media
SBC
Media
SBC
Benefits of Split Signalling & Media
Emerging standards for converged networks (IMS, TISPAN, etc)
dictate that separation is required
Media functions can be deployed at the network edge, saving $$
required to backhaul the media traffic to a central location
Physical locations can scale their signalling and media
independently – Allows for flexible deployment
Integrated SBC deployments can be upgraded to Distributed
configurations at any time with total reuse of hardware
H.248
Signalling
Media
Signalling
Signalling
SBC
Media
Media
SBC
Media
SBC
Standards Organizations
3GPP - 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 CDMA
http://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
Terminology
3GPP
A-RACF
AUC
BGCF
C-BGF
GSTN
HSS
IBCF
I-BGF
I-CSCF
IP-CAN
IMS
MGCF
NAPT
P-CSCF
PDF
QoS
RCEF
SBC
S-CSCF
SPDF
THIG
UE
3rd Generation Partnership Project
Access Resource Admission Control Function
Authentication Centre
Breakout Gateway Control Function
Access/Core Border Gateway Function
Global Switched Telephony Network
Home Subscriber Server
Interconnect Border Control Function
Interconnection Border Gateway Function
Interrogating Call Session Control Function
IP Connectivity Access Network
IP Multimedia Subsystem
Media Gateway Control Function
Network Address and Port Translation
Proxy Call Session Control Function
Policy Decision Function
Quality of Service
Resource Control Enforcement Function
Session Border Controller
Serving Call Session Control Function
Service Based Policy Decision Function
Topology Hiding Inter Network Gateway
User Element
Thank you
www.newport-networks.com
June 2006
SBC Signalling Functions
In 3GPP wireless networks the SBC
Signalling requirements are:
Proxy Call Session Control Function PCSCF function
Interrogating Call Session Control
Function (I-CSCF)
Can perform Topology Hiding
Interconnect Gateway (THIG)
functions where required
Contains a Policy Decision Function
which can be externalized if required
Diameter / XML to external policy databases
PDF
P CSCF
I CSCF
IBCF
THIG
H.248 Control of Media Plane
SBC Signalling Functions
In TISPAN Converged networks the
SBC Signalling requirements are:
An Interconnect Border Control
Function when interconnecting
networks
In TISPAN the PDF is defined as SPDF
(Service based Policy Decision
Function)
= 3GPP defined function
= TISPAN defined function
SBC Media Functions
Currently Null function in 3GPP
In TISPAN architectures performs
Access to Core Border Gateway
Function (CBGF)
Interconnect Border Gateway
Function (IBGF)
H.248 Control of Media Plane
I / C BGF
SBC Media Functions
= 3GPP defined function
= TISPAN defined function
TISPAN architecture with SBC’s
Home Network
(Terminator)
Home Network
(Originator)
S-CSCF
S-CSCF
THIG
I-CSCF*
PDF
P-CSCF
HSS
HSS
Visited
Network
(Originator)
I BCF
I BCF
Visited
Network
(Terminating)
THIG
PDF
I-CSCF*
I BCF
I BCF
I BCF
P-CSCF
BGCF
BGCF
P-CSCF
IP-CAN
MGCF
MGCF
SIP-I
IP-CAN
MG
IP-CAN
UE
MG
UE
UE
Registration
PSTN
Switches
Session Set up
= SBC
GSTN
PSTN
Switches
GSTN