Roles of Session Border Controllers in IMS Networks

1
Roles of Session Border Controllers in IMS
Networks

• CANTO - June 2006

2
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?
• SBCs in IMS Networks
• What functions do they provide in the IMS
  Network?
• How will SBCs evolve within the IMS
  architecture?
• Conclusions
• Summary
• References

3
SBC Role Today - Session Aware
SIP Normalization IPv6 / VLAN Topology
Hiding DoS Prevention Firewall/NAT Load
Balancing Session QoS
Session Border Controller
Core SIP Infrastructure
Simplify, Protect and Offload
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Firewall/NAT Traversal

• SIP Services
• SIP Proxy
• Application Server
• Media Server

Access Networks
Firewalls/ NATs
SIP Endpoints
Session Controller
Simplify Offload

• 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

5
DoS Attack Prevention
SIP Services
Access Network
Core Network
Session Controller
Protect

• 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 -gt Maintaining QoS for
  other users

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Topology Hiding
SIP Services
Session Controller
Peering Network
17.3.x.x
200.2.x.x
110.5.x.x
Access Network
Protect

• Provides protection against Denial of Service
  (DoS) by hiding internal IP addressing
• Removes sensitive IP addressing and domain names
  from SIP headers and SDP

7
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

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Catalyst for IMS Deployment
9
Who gains from Fixed/Mobile Convergence?

• Service Providers
• Optimized all IP network reduces OPEX
• Opens the fixed markets 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 (Metcalfes Law)

10
IMS Basics
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IMS Network Characteristics
Mobile Network
Peering IMS Network
IMS Network
Scalable Architecture

• 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

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SBC Features
Simplify and Protect
PSTN Equivalence

• NAT/Firewall Traversal
• Protocol Normalization
• Protocol Interworking
• VLANs
• Geographic Resilience

• Policy Enforcement
• Policing
• Session Admission Control
• Legal Intercept
• Emergency Call Handling

IMS/TISPAN Requirement
Management
Security

• DoS Protection
• Rate Limiting
• Topology Hiding
• Encryption

• Call Detail Records
• EMS
• SNMP

Within IMS Scope
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IMS Architecture with SBCs

• Directs Users to Home Network
• NAT/FW Traversal
• Emergency Call Handling

Home Network (Originator)
Home Network (Terminating)

• HSS service lookup to select S-CSCF

Visited Network (Terminating)
Visited Network (Originator)
S-CSCF
S-CSCF
I-CSCF
THIG
P-CSCF
I-CSCF
I-CSCF
P-CSCF
BGCF
BGCF
MGCF
P-CSCF
IP-CAN
MGCF
SG
IP-CAN
SG
IP-CAN
UE
MG
MG
UE
UE
PSTN Switches
PSTN Switches
Registration
Session Set up
GSTN
GSTN
SBC
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TISPAN architecture SBC MediaDSL access, WLAN
etc
Home Network (Originator)

• DSCP QoS Re-mapping
• Topology Hiding

Media path
S-CSCF
Registration
I-CSCF
Session Set up
I BCF
SBC
I-BGF
P-CSCF
BGCF
C-BGF
IP-CAN
MGCF
MG
UE
PSTN Switches

• Session Policing
• Legal Intercept
• IPv4 to IPv6
• Session Admission Control

GSTN
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SBC Migration to IMS

• 1N and N1 models
• SCTP (standardized signalling transport)
• Signalling compression

• Physically separate the product architecture
• Signalling encryption IPSec/TLS

• Separate signalling media functions
• Independently scale signalling and media

Signalling SBC
Signalling Functions
Signalling Functions
SIP
MEGACO/H.248
H.248
H.248
MEGACO/H.248
Control Plane
Media Plane
MediaFunctions
RTP/RTCP
MediaFunctions
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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

Media
Signalling
H.248
H.248
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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

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Conclusions

• Service Providers are moving to IMS/TISPAN
  architectures
• Service Providers should invest in SBCs that
  are forward compatible with IMS
• SBC architecture that supports signaling and
  media separation is required
• Today, SBCs provide a greater set of features,
  than IMS requirements define

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Terminology

• 3GPP 3rd Generation Partnership Project
• A-RACF Access Resource Admission Control Function
• AUC Authentication Centre
• BGCF Breakout Gateway Control Function
• C-BGF Access/Core Border Gateway Function
• GSTN Global Switched Telephony Network
• HSS Home Subscriber Server
• IBCF Interconnect Border Control Function
• I-BGF Interconnection Border Gateway Function
• I-CSCF Interrogating Call Session Control
  Function
• IP-CAN IP Connectivity Access Network
• IMS IP Multimedia Subsystem
• MGCF Media Gateway Control Function
• NAPT Network Address and Port Translation
• P-CSCF Proxy Call Session Control Function
• PDF Policy Decision Function
• QoS Quality of Service
• RCEF Resource Control Enforcement Function
• SBC Session Border Controller

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Thank you

• www.newport-networks.com

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SBC Signalling Functions
Diameter / XML to external policy databases

• In 3GPP wireless networks the SBC Signalling
  requirements are
• Proxy Call Session Control Function P-CSCF
  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
• 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)

IBCF
P CSCF
I CSCF
THIG
H.248 Control of Media Plane
SBC Signalling Functions
3GPP defined function
TISPAN defined function
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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
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TISPAN architecture with SBCs
Home Network (Terminator)
Home Network (Originator)
Visited Network (Terminating)
Visited Network (Originator)
S-CSCF
THIG
S-CSCF
THIG
I-CSCF
P-CSCF
I-CSCF
I BCF
I BCF
I BCF
P-CSCF
BGCF
I BCF
I BCF
BGCF
MGCF
P-CSCF
IP-CAN
MGCF
SIP-I
IP-CAN
MG
IP-CAN
UE
MG
UE
UE
PSTN Switches
PSTN Switches
Registration
Session Set up
GSTN
GSTN
SBC