To Rent or Buy the IP PBX?Maybe it’s Both….

Building a VoIP Solution That Enables Both

Topics• To Rent or Buy the IP PBX?• Barriers to Both• Session Controllers• Enterprise Applications• Carrier Services

To Rent or Buy?• Both improve user experience, reduce OPEX and offer

similar features• IP Centrex farms hassles of ownership to service providers

and also has a better disaster/survivability story• IP PBXs can be used with a range of service providers and

can migrated to gradually.• Hedge your bets – use IP Centrex to provide services to

SOHO while you IP enable existing PBXs or deploy IP PBX in larger offices.

Barriers to Both• Using VoIP interconnects creates some challenges -- TDM

is an implicit firewall and normalizes VoIP traffic.• Security

– How do calls traverse existing firewalls and NATs?

• Interoperability– How do calls go off-net?– How can other SIP applications be leveraged?– What are the pain points?

Corporate PBX

Broadband

SOHO

VoIP Security • Firewall implementations are a barrier to real-time services

– Security policies prevent promiscuous and ad hoc connectivity– Lack protocol awareness for H.323 and SIP

• IP PBX– Firewall traversal needed to reach the corporate PBX

• IP Centrex– Multiple NAT traversals required to reach SOHO users– Firewall traversal needed to reach corporate users

VoIP Incompatibilities • Applications are SIP based while network infrastructure

and IP PBXs continue to be H.323 dominated– 90% of VoIP Networks are H.323; 90% of VoIP Apps are SIP– Prevents enterprises from leveraging SIP apps from carriers.

• Standards are subject to interpretation– Problem areas: message formats, message order, timing

• Other problem areas arise because of endpoint limitations– Codec mismatch– Mismatch of DTMF transport methods– T.38 fax

Doing Both• Session Controllers enable carriers and the enterprise to

control, route and manage VOIP traffic in a secure and seamless manner

• Needed for IP Centrex since IP is the delivery mechanism– Overcome security issues to reach end-user– Simplify off-net connectivity to PSTN gateways

• Provides greater ROI for IP PBX deployments since IP can be used to connect with the user and the network.– Convert trunks to VoIP by replacing TDM gateways and reduce

access charges by converging voice and data.

What is a Session Controller?• AKA Border Controller or Session Border Controller• New breed of networking technology that provides layer 5

routing and control to manage real-time traffic flows in IP networks

• Technology addresses issues of:– Session routing– Network security – Call admission control– Signaling interoperability– Service quality

ESC

Session Controller ArchitectureSIP Softswitch

Network

EnterprisePeering

PSTN

BroadbandH.323 Network

CarrierPeering

BroadbandNAT Traversal

PSTNOrig/Term

ESCSoftswitch

CSC

ESC

ESC

ASP

Core SC vs. Edge SC• Core Session Controller (CSC)

– Signaling only platform deployed in the network core – Programmable route engine– Centralized CDR collection – Call Admission Control on a network basis

• Edge Session Controller (ESC)– Edge Session Controller deployed at the network edge to

manage interconnects (both media and signaling)– NAT and Media Routing for network security– Signaling Interoperability and interworking (abstraction layer)– Call Admission Control on a local basis– Media processing for specialized applications such as

transcoding

How Does a Session Controller Work?

SIP Ingress Leg

H.323 Ingress Leg

Call Bridge (IWF)SIP Egress Leg

H.323 Egress Leg

Routing and CAC Logic

INVITE

ARQ, LRQ, Q.931

INVITE, REGISTER

ARQ, LRQ, Q.931 FCP Dynamic

Media Routing Fabric

NAT/PATStatic

H.323

SIP

Unauthorized MediaAuthorized Media

Media

Databases

Signaling • Complex because VoIP technologies are

incompatible– H.323-SIP, H.323-H.323, SIP-SIP, etc.

• Abstracts signaling from routing providing any-to-any calls

• Multi-service: Video and Voice

Media Routing• Selective – media flow may be off-net or between

trusted endpoints• NAT/PAT of media and signaling enables topology

hiding• Dynamic “pinholes” for media prevents unauthorized

access• NAT traversal provided for subscribers using

broadband network access

Media Processing• Media translation applications:

– Normalize media codecs – DTMF processing

• Selective use limits the number of DSPs needed and optimizes platform costs

Enterprise VoIP Applications

HQ

PBX

VoIP Enabled Router

Public Network(PSTN)

ISP

Data VPNH.323

CSC

Unified Messaging System

IP Telephone

IP PBXDesktop

Client

IP Telephone

IP PBXDesktop

Client

ITSP

H.323

SIP

SIP

H.323

IP Telephone

IP PBXDesktop

Client

ASP

SIP

H.323

ESC

ESC

Hosted PBX

SOHO

International Sites

Domestic Sites

Campus PBX

ESC

Local & LD

UntrustedTrusted

Let Service Providers Simplify the Problem

CSC

TDM CarrierBackbone ESC

TDM Termination

SS7

SS7SS7

LegacyPBX

IP PBX

Hosted PBX

ESC performs local CAC,signaling adaptation(e.g. H.323/SIP), NAT and Media Firewalling

CSCserves asa route enginebetween IPplatforms andservice based CAC

PBX Tieline

Media GWPBX

Tieline

Carrier Services• Offering managed PBX services• Hosted PBX or IP Centrex• Bundle those services with long distance and other valued

added services like teleconferencing• Early providers: Level3, Masergy, GoBeam• Trials: SBC, Verizon

Enabling Enterprise VoIP• Session controllers enables the enterprise to hedge their

bets on IP Centrex and the IP PBX• Session controllers simplify VoIP deployment by

overcoming issues of VoIP security and incompatibility• Session controller position the enterprise for the future by

providing a foundation for other real-time IP application

Dan DearingVice President of Marketing

ddearing@nextone.com