Upgrading the NGN - Part 1

8/8/2019 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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2 White Paper - 2007 Tekelec, Inc.

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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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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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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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 utingEngine

Sessio n Ro utingEngine

Sessio n Ro u tin 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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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.

Documents

Upgrading the NGN - Part 1