Core Session Controllers

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Core Session Controller
Sridhar Ramachandran Chief Technology
Officer sri_at_nextone.com
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NexTone Customers
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What is a Session Controller?

• Point of control for multimedia signaling and
  media
• Service protection
• Network isolation and insulation
• Other names
• IP-IP Gateway
• Back to back gateway
• Session Border Control
• Border Session Control

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Problems where VoIP has proven effective

• Transport
• Switching
• Interconnect
• Carrier Carrier
• Enterprise Carrier
• Applications

• Top and bottom line enhancing
• Flexibility and enforceability are key
• Control points

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Growth in VoIP Peering
ITXC Carries Record Voice Call Volumes for
Holidayshttp//www.itxc.com/pages/press/release22
9.html In past years, our carrier customers
used ITXC to complete their subscribers calls
because our VoIP technology allowed us to provide
them high quality at low prices. Usually, the
only VoIP involved was within our network. Now
carriers also choose ITXC for interconnection
because they themselves are deploying VoIP
equipment in their own networks or even at their
subscribers premises. Our technology allows
these carriers to connect their VoIP networks to
ours at much less cost than a legacy PSTN
interconnect and with much greater flexibility.
In the fourth quarter of 2003, over one third
of ITXC's traffic was originated or terminated
through a direct VoIP interconnect between
ITXC.net and the network of another carrier.
ITXC has VoIP interconnects with over 140
carriers or service providers in 60 countries and
supports VoIP traffic exchange with a wide
variety of network equipment vendor platforms
based on either Session Initiation Protocol (SIP)
or H.323 call control protocol. iBasis Posts
Record VoIP Call Volume During New Year's
Day http//www.ibasis.com/news/PR2004/pr01072004.h
tm "In addition to setting an overall record for
traffic, we are experiencing a record volume of
traffic that enters or exits the iBasis Network
as IP traffic," said Ofer Gneezy, president and
CEO of iBasis. "Major carriers have been
deploying VoIP infrastructure to support both
retail services and direct VoIP carrier
interconnects. At the same time, new service
providers are delivering VoIP services directly
to residential and business consumers. Both can
realize significant cost efficiencies by
establishing direct VoIP interconnections with
our proven global VoIP infrastructure. "More
than 70 of iBasis traffic either originates or
terminates through our direct VoIP interconnects
with service providers. Direct VoIP interconnects
require significantly less capital expense in the
iBasis network than legacy TDM interconnects. In
addition, we are enabling our customers to more
fully benefit from the efficiencies of VoIP and
the public Internet for global telecommunications.
"
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VoIP Peering Requirements

• Flexibility
• Media and Signaling Routing based on trust
  boundaries
• Any-to-any interworking SIP, H.323, multiple
  vendor interoperability
• High Performance and Scale
• On-demand Media Processing
• Leverage and enforce existing peering agreements
• Call Admission Control
• Prevent Denial of Service attacks and service
  abuse/theft
• Call accounting
• Call Detail Record (CDR) generation and reporting
• Topology Hiding
• Go across address boundaries
• Control Points
• Segmentation/classification of traffic

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What are Carriers session control needs?

• Call routing with multiple business models
• Wholesale
• Transit
• Pre-paid
• Post-paid/retail
• Service brokerage
• Special applications
• Permissive dialing

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Session Controller Placement
Core SC
Softswitch
CarrierPeering
Edge SC
Edge SC
Edge SC
PSTNOrig/Term
EnterprisePeering
BroadbandNAT Traversal
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Aggregation
Edge SC
Carrier IP Network
Partner Carrier IP Network
Core SC
Edge SC

• Multiple interconnects between same carriers
• Multi-stage and hierarchical call admission
  control
• Core SC maintains notion of aggregate capacity

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Merits of this Approach

• No control protocol
• Call admission control based on network egress
  policies
• Ability to add other service selection logic
• Applications
• Quality of Service demanded or provisioned
• Call routing with mixed business models
• Wholesale
• Pre-paid or post-paid
• Transit
• Normalized and vendor independent call routing
• SIP only

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Other Advantages

• Implementation flexibility
• Redirect server
• Stateful SIP proxy
• B2BUA
• Core SC function can be integrated into Edge SC
• Leverage TRIP (rfc 3219) and TGREP
• View Edge SCs and Gateways as originators and
  terminators of sessions

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What about the Softswitch?

• Control paradigm has limited effectiveness
• Gateway control
• Call control
• Softswitch designed for a closed network
• MGCP/MEGACO to provide total control of internal
  network
• How does one build a fabric of softswitches?

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Summary

• Session Controllers are essential for VoIP
  peering
• Core Session Controllers provide higher level
  functionality, based on SIP signaling

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Thank You. sri_at_nextone.com 1-240-912-1301
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What about the Softswitch?

• Control paradigm has not proven effective
• Softswitch designed for a closed network
• MGCP/MEGACO to provide total control of internal
  network
• VoIP interconnects challenge the Softswitch
  control paradigm
• Interconnects carrier peering, and MGCP/MEGACO
  control of 3rd party networks not viable
• SIP/H323 typically added as after-thought to
  interwork trusted devices Softswitch domains (and
  VoIP interconnects should never be trusted)
• VoIP Interconnect Solution
• Keep SS7 and MGs at the edge of the VoIP network,
  Softswitch as cluster controller to help handle
  SS7/C7
• Introduce Session Controllers to manage VoIP
  peering and interconnects between carriers and
  enterprises
• Overcome lower layer (Layer 2/3) IP issues
  call-by-call NAT/PAT, security, VLANs etc

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Core Session Controller

• Introduction
• What is a session controller?
• Growth in VoIP peering
• Need for more control at the core
• View of softswitch
• Core session controller fabric