upgrading the ngn - part 1
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WHITE PAPER
Upgrading the Next-GenerationNetworkPart I A Signaling Perspective
This document is for informational purposes only, and Tekelec reserves the right to change anyaspect of the products, features or functionality described in this document without notice. Pleasecontact Tekelec for additional information and updates. Solutions and examples are provided forillustration only. Actual implementation of these solutions may vary based on individual needsand circumstances.
2007 Tekelec. All rights reserved. The EAGLE and Tekelec logos are registered trademarks ofTekelec. TekCore is a trademark of Tekelec. All other trademarks are the property of theirrespective owners. TKLC-WP-007-NA-10-2007
The first paper in this
multi-part series provides
an overview of Tekelecs
solution for SIP signalingand session control in
next-generation networks.
5200 Paramount ParkwayMorrisville, NC 27560 (USA)
1-919.460.5500 or 1-888.628.5527
www.tekelec.com
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Table of ContentsIntroduction.............................................................................................................................................1Current VoIP Network Infrastructure.....................................................................................................2Expanding the NGN Network.................................................................................................................3Introducing the SIP Signaling Router (SSR) Function to the NGN .......................................................4Bridging the TDM, NGN and IMS Domains............................................................................................6
Interworking Between the TDM and NGN Domains......................................................................................... 7Seamless NGN Integration and Evolution to IMS.............................................................................................. 7
Summary..................................................................................................................................................9About Tekelec........................................................................................................................................10
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Upgrading the Next-Generation Network
Part I. A Signaling Perspective1
IntroductionThere is no denying the excitement and momentum generated by Voice over Internet Protocol (VoIP) services.
Although it is considered to be a disruptive technology, VoIP offers many outstanding attributes such as integration
with web-based applications, simplicity in call routing and enhanced voice services. In a relatively short time period,
VoIP has gained strong acceptance as an overlay or even a replacement to existing TDM technologies in both operator
and enterprise telecommunications networks. The popularity of VoIP is evident in a recent report published by aleading industry analyst firm, which indicates the number of VoIP subscribers will more than double over the next two
years. This trend is being seen in all regions of the world.
SOURCE: Frost & Sullivan, 2006
0
5
10
15
20
25
30
Subscribers
(Millions)
2004 2005 2006 2007 2008
Year
Europe
North America
0
5
10
15
20
25
30
Subscribers
(Millions)
2004 2005 2006 2007 2008
Year
Europe
North America
Figure 1. Growth in VoIP Subscribers
Why have operators been deploying VoIP technology and services? Operators first deployed VoIP technology in the
core of their networks for cost reduction purposes. VoIP services then gradually expanded into the enterprise and
residential markets. The introduction of VoIP services based on SIP application servers enabled operators to accelerate
the deployment of VoIP services to their customers. In 2003, wireless operators adopted 3G Release 4, which resulted
in the migration of their circuit-switched voice networks to an ATM or IP core network using softswitch technology.
As the adoption of VoIP service increases, so do the requirements placed on the network infrastructure to support the
service. Currently, the next-generation network (NGN) softswitch infrastructure provides VoIP services. However, in
order to support the expected increases in VoIP subscribers, the NGN network must grow in both signaling and bearer
capacity to handle the additional traffic.
This first paper, in a multi-part series, covers the benefits of adding a SIP signaling and session control layer to
upgrade the NGN. It provides an overview of the issues that are impacting the growth of the NGN, and how
operators can benefit by adding SIP signaling and session control to next-generation networks.
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Current Vo IP Network InfrastructureA closer examination of NGN implementations reveals a loose collection of VoIP network elements such as
softswitches, session initiation protocol (SIP) application servers, media servers, and SIP-capable endpoints. Unlike its
public switched telephone network (PSTN) counterpart, there is no separate signaling infrastructure at the core of the
NGN to facilitate signaling between these NGN network elements. Rather, the NGN elements utilize direct signaling
connections to each other, forming a mesh-like network architecture, as illustrated in Figure 2.
Figure 2. Logical-mesh Signaling Architecture in Current NGN Implementations
Within a typical NGN architecture, there is no stand-alone session layer to assist NGN elements with signaling/session
activities. Each network element must handle any session-related tasks such as routing, traffic management,
redundancy and service implementation, as shown in Figure 3.
E n d p o i n ts P e r f o rm
S I P S e s s i o n T a s k s- R o u t e / s e s s io n m a n a g e m e n t
- S e r v i c e o r c h e s t r a ti o n- B i l l i n g
- T r a f f ic e n f o r c e m e n t- R e d u n d a n c y / h i g h a v a i l a b il it y
I P R o u t i n g N e t w o r k- P a c k e t - b a se d r o u t i n g- I P a d d r es s i n g a n d m a n a g e m e n t
- I P r o u t in g p r o t o c o l s O S P F , I S - IS e t c .
- Q o S
S B C
O t h e r
V o I PN e t w o r k
P S T N
P L M N
M e d i a
S e r v e r M S C
S e r v e r
3 rd P a r t y
S I P A p p s
Bi l l ing
R o u t i n g
S ubD a t a
B i l l ing
R o u t i n g
Su b
D a t a
RTP
RTP
RTP
RTP
S IP S IP S IP S IP S IP
S o f t s w i t c h
Figure 3. NGN Without a Signaling/Session Framework
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Upgrading the Next-Generation Network
Part I. A Signaling Perspective3
Implementing the NGN without a signaling/session framework may appear to be sufficient at first. As the network
grows, however, various issues associated with not having a capable session framework are exposed, such as:
User data management -- Since NGN elements are capable of making both routing and service decisions, usersubscription data is required at the network element level. As a result, user data is scattered throughout thenetwork, causing potential problems with provisioning and data synchronization.
Scalability -- Due to the fact that NGN elements make session-level routing decisions, routing data isprovisioned on the network element. This routing data must be updated to reflect the changes in the
network topology (such as the addition of new nodes). Frequent updates of routing data combined with anincreasing number of nodes can cause provisioning errors, routing table exhaustion and an increase in thecost of operations.
Billing data scattered across the network -- Since there is no centralized signaling/session framework, eachNGN element generates its own billing data. The bill ing data format may not be consistent across all of thenetwork elements, especially in a multi-vendor environment. Therefore, extensive billing mediation may berequired, potentially causing billing errors and lost revenue.
Traffic management -- Traffic management is impossible in the current NGN architecture since each elementonly has local visibility to the traffic it manages. Traffic flow controls and other traffic management-relatedtasks cannot be efficiently implemented, which could lead to network congestion thus impacting servicelevel agreements (SLAs).
Voice-centric -- The current softswitch-based architecture ties SIP signaling very closely to voice call setup. It is
not well suited for setting up non-voice sessions such as video or text messaging. Interoperability testing -- Since each NGN element interacts directly with every other element, interoperabilitytests (IOTs) must be performed to ensure proper communication between the elements. As the number ofNGN elements as well as vendors increases, so does the testing complexity. For example, introduction of anew NGN element into an existing 10-node network requires up to 10 IOTs to be performed.
Number portability -- There is currently no consistent method for supporting PSTN-based number portabilitywithin the voice over IP (VoIP) environment. Since the NGN element makes routing decisions on its own, it isdifficult to implement a consistent number portability scheme across the entire NGN network.
Inter-carrier VoIP peering issues There is no single approach for NGN elements to handle trafficmanagement, inter-carrier billing, call admission and control, etc.
No clear migration path to the IP multimedia subsystem (IMS) architecture.
Expanding the NGN NetworkThe NGN cannot be properly expanded without the implementation of a suitable framework that is capable of off-
loading various signaling and session tasks from the edge NGN elements. With a capable session layer, session-related
tasks are moved from the edge NGN node to a centralized core session framework. The resulting architecture, shown
in Figure 4, allows the NGN network to grow systematically in response to increasing demand for VoIP services, while
avoiding the various limitations previously mentioned.
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Figure 4. NGN with Core Signaling/Session Framework
A session framework also offers an excellent opportunity to introduce IMS technology and services into the NGN
environment. In fact, the IMS session management technology is a perfect candidate for implementing a signaling
layer in the NGN. 3GPP has foreseen the need for a session control layer within the IP multimedia service network and
defined the call session control function (CSCF) to provide various signaling and session services. The session routing,
service orchestration, billing, charging and other functions defined by 3GPP for the IMS CSCF can be directly applied
to and be benefited by the NGN today!
Tekelecs vast experience in SS7 signaling provides the basis for its strong belief in the importance of a mediaindependent session control layer, and for bringing IMS CSCF technology to the NGN community. However, the
3GPP IMS CSCF cannot simply be deployed within the NGN without adapting its protocols and procedures. Therefore,
Tekelec offers a unique session management solution for the NGN environment that adheres to 3GPP IMS CSCF
definitions, but is adaptable to the changing environment of the NGN. Called the TekCore Session Manager, it
provides SIP signaling router (SSR) functionality for the NGN, and is introduced in the next section.
Introducing the SIP Signaling Router (SSR) Function to the NGNTekelecs TekCore Session Manager supports 3GPP-defined IMS session control functionality to handle various session
management and control tasks needed within the NGN. TekCore maintains compliance with 3GPP IMS S/I-CSCF
specifications, while offering adaptations for interworking with non-3GPP compliant IP environments. TekCores SIP
signaling router (SSR) function introduces a session control framework, plus the latest in IMS technology to the NGN.
IMS compatibility provides seamless interworking and facilitates the evolution to an IMS architecture in the future.
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Part I. A Signaling Perspective5
TekCoreSession Manager
Session Framework
- Robust/ redundant/ highly available
- Route/ session management- Service orchestration
- Billing
- Traffic enforcement
Media IP Routing Network
- Packet-based routing- Jitter and delay sensitive
- IP routing protocols: OSPF, IS-IS, etc.
- Media handling: RTP, RTSP, etc.
Signaling
(i.e. SIP)
Bearer
(Packetized Voice,Video etc.)
Signaling
POP
Media
POP
OtherVoIP
NetworkMedia
Server
SLA
Policy
3rd party
SIP Apps
OSS Interworking
Single Point Provisioning
IMS
Standard
3GPP/3GPP2
IMS interfaces
EAGLE 5
Integration
SS7 INServices
SubscriberProfile
Routing
Data
Multimedia
Billing
Softswitch
PSTN
PLMNMSC
Server
IADSIP UASBC
Figure 5. Tekelecs TekCore SIP Signaling Router (SSR) Function
When deployed in an NGN, Tekelecs TekCore Session Manager provides the following functionality and benefits
(Table 1):
Table 1: TekCore Session Manager features and benefits
Technical Issue TekCore Solution Benefits
User Data ManagementData scattered across the network
User profile information iscentralized
Reduced provisioning cost andcomplexity
Scalability/Manageability Routing
complexity increases as the number
of route-aware edge devices
increases
Route management is
centralized to off-load it from
the edge
Improved manageability provides
ability to scale network cost-
effectively and quickly
Billing
Data scattered across the network
Billing data is centralized Reduced need for billing mediation
and associated costs
Traffic Management Traffic flow is managed
between NGN elements andintegrated monitoring is
provided as well
Visibility into the network assists
with network design, trafficengineering and troubleshooting
Voice-centric Deals with signaling only
and is completely bearer
independent
Reduced infrastructure and operations
costs via a single core signaling
framework for all media types
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Technical Issue TekCore Solution Benefits
Interoperability
Degree of connectivity makes
multi-vendor environment
problematic
Provides a single point for
SIP protocol interworking
Reduced IOT costs when expanding or
adding new network nodes
Number Portability Supports seamless number
portability routing of SIP
sessions using ENUM,
redirection-proxy or service
bureau models
Ability to adapt to various number
portability schemes allows operators
to choose the most cost effective NP
method and provides flexibility to
make modifications as needs change
Inter-carrier VoIP Peering Signaling/ session framework
consolidates inter-carrier traffic
Operators can better manage inter-
carrier traffic by implementing a well-
managed signaling POP
IMS Migration
No clear migration path
Establishes a session control
layer that forms the basis for
evolution to IMS
Solves today's problems by integrating
with existing NGN assets and has clear
migration path to IMS
Bridging the TDM , NGN and IMS Dom ainsTekCore can be deployed in both NGN and IMS networks serving as a SIP signaling router when deployed in the
NGN and as a CSCF in the IMS environment. TekCore is designed to interwork seamlessly with Tekelecs EAGLE
5
Integrated Signaling System (ISS), providing the signaling/session bridge between SS7 TDM, NGN and future IMS
networks, as illustrated in Figure 6. The TekCore SSR function interworks with SS7 networks through integration with
the EAGLE 5 ISS, as well as directly with the IMS session management layer over an Mw interface. The bridging
capabilities provide additional revenue opportunities as the NGN operator benefits from the ability to offer both
traditional and IMS services to customers in either domain.
T D M/SS7
TekCore Session
Mana ger Functions
T ekC o re
S- C SC F
T ekC o re
I -CSCF
TekCore
P- C SC F
TekCore
S SR
IM S
N G N
Migra t ion Pa th
IMS session
Se s s i o n mg r
Integrat ion with
EAG L E 5 I SS
Figure 6. TekCore SSR Function Bridges Services Across Network Boundaries
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Part I. A Signaling Perspective7
Interworking Between the TDM and NGN Domains
As previously mentioned, TekCores SSR function supports interworking with existing SS7 networks through
integration with Tekelecs EAGLE 5 ISS platform. The EAGLE 5 ISS and TekCore together create a bridge between the
SS7 and NGN at the signaling and session control layer, allowing the sharing of applications (IN and SIP) and data
across network boundaries (Figure 7). Using this bridge, the routing of a session can now be influenced by events and
applications in the SS7 domain. For example, outages in one part of the SS7 network can be reported to TekCore,
which may decide to route the session to a backup SIP server that interworks with the non-affected part of the SS7
network. Another example might be to use the number portability database to influence the routing of ported-in /
ported-out subscribers.
SS R
SS R
SS R
SS R
EAGLE 5ISS
IN
ININ
IN
SS7 S ignaling
SIP NGN
Sessio n Ro u tin g
Engine
Sessio n Ro utin g
Engine
Sessio n Ro utin gEngine
Sessio n Ro utin gEngine
Sessio n Ro utingEngine
Sessio n Ro utingEngine
Sessio n Ro u tin gEngine
Sessio n Ro utin gEngine
Figure 7. Next-generation Network and Service Interworking with the TDM Domain
Seamless NGN Integration and Evolution to IMS
While many vendors are pushing a greenfield IMS deployment approach, Tekelec believes that IMS will be deployed
incrementally. Therefore, interworking between the NGN and IMS network will be required in order to facilitate
communications between subscribers in both domains. Additionally, interworking between IMS and NGN facilitates
the ability to bridge services (Figure 8). NGN subscribers can benefit from future IMS domain services, while the IMS
subscribers can enjoy existing NGN services saving operators from replicating existing services in the IMS domain.
Operators benefit from the ability to leverage existing investments while capitalizing on the revenue-generating
opportunities of IMS services.
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NGN
IMS
Inter-domain
session setup
An NGN subscriber
uses IMS services
An IMS subscriber
uses NGN services
Figure 8. NGN-IMS Interworking at the Network and Service Level
Tekelecs TekCore Session Manager supports 3GPP-defined, IMS session control functionality, to handle various
session management and control tasks needed within the NGN. TekCore is capable of supporting non-3GPP-
compliant as well as 3GPP-compliant interfaces a unique capability that allows it to bridge the NGN with IMS.
From an IMS network point of view, the TekCore SSR looks like a specialized CSCF function, offering services to NGN
subscribers. Therefore, sessions can be setup between non-3GPP-compliant NGN network elements and 3GPP IMS-
compliant elements over an Mw interface.
As shown in Figure 9, TekCores SSR function also supports the IMS ISC interface, enabling it to communicate with
IMS-compliant SIP application servers. IMS services can be applied to an NGN session setup, allowing an NGN
subscriber to access IMS-based services in a seamless manner. As another option, the SSR can access subscriber data
residing on the 3GPP IMS HSS, over Cx and Dx interfaces.
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Upgrading the Next-Generation Network
Part I. A Signaling Perspective9
SS R
S-CSCF
P-CSCF
I-CSCF
Mw
Mw
ISC
IMS
SIP AS
Cx/Dx
NG N
Subscribers
IM S
Subscribers
NGN
IM S
Figure 9. TekCore Supports 3GPP-Compliant and Non-Compliant Services
SummaryThe popularity of VoIP is increasing, driving the need to expand the next-generation network. However, the current
NGN architecture has no core-signaling infrastructure, which greatly limits expansion capabilities. NGN expansion
without core signaling infrastructure causes scalability and availability issues, increases routing and service complexity,
increases IOT and operations costs, limits vendor choice, and does not interwork with or provide a feasible evolution
path to future IMS technologies.
Clearly, the NGN cannot be properly expanded or optimized without implementation of a core SIP signaling andsession framework. This same issue was addressed years ago in TDM networks, when operators overwhelmingly
moved to a separate, distinct SS7 signaling network when they deployed standalone signal transfer points (STPs). The
3GPP IMS architecture confirmed this view by introducing the IMS call session control function (CSCF), which
performs the core signaling and session control function for the IMS network. Rather than re-inventing what has
already been defined by the 3GPP, Tekelec is utilizing IMS session control technology and making it available in the
NGN with the TekCore SIP signaling router (SSR) function.
This paper is the first in a multi-part series that covers the benefits of adding a SIP signaling and session control layer
to upgrade the NGN. This first paper provided an overview of the issues that are impacting the growth of the NGN,
and how operators can benefit by adding a SIP signaling and session control layer in next-generation networks. Parts II,
III and IV of this series, are posted on www.tekelec.com, and cover the following:
Part II Upgrading the Next-generation Network: Layer-5 Core SIP Routing
Part III Upgrading the Next-generation Network: SIP Signaling Router Use Cases
Part IV SIP Signaling and Session Control: The Missing Layer in the Next-generation Network (NGN)
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About TekelecTekelec is a high-performance network applications company that is accelerating the transition to IP multimedia
subsystem (IMS) networks for service providers around the globe. With its experience at the intersection of network
applications and session control, Tekelec creates highly efficient platforms for managing media and delivering
network solutions. Corporate headquarters are located near Research Triangle Park in Morrisville, N.C., U.S.A., with
research and development facilities and sales offices throughout the world.
Tekelec is the worldwide leader in SS7 signaling solutions, with a global market share more than twice that of its
nearest competitor (SOURCE: VDC, May 2006). Tekelecs next-generation solutions enable operators to migrate from
circuit-switched technology to IP-based multimedia networks at their own pace, without major network overhauls.
Operators can build the foundation for an IMS network without interrupting revenue streams from existing services
and applications.
For additional information on the TekCore Session Manager product, CSCF or SSR functions, contact your local
Tekelec sales representative or visit www.tekelec.com.