PCN Juniper Networks

White Paper

Juniper Networks, Inc.1194 North Mathilda AvenueSunnyvale, California 94089 USA408.745.20001.888 JUNIPERwww.juniper.net

Building Next-Generation Mobile Packet Core NetworksEnabling Mobile Operators to Build Highly Efficient Converged IP/MPLS Core Networks

Part Number: 200220-001 April 2007

2

Building Next-Generation Mobile Packet Core Networks

Copyright ©2007, Juniper Networks, Inc.

Table of ContentsExecutive Summary ................................................................................................3

Introduction: Global Perspective on the Mobile Market ...........................................4

1G to 3G and Beyond .........................................................................................5

Making the Case: IP for 3G Mobile Networks ....................................................6

Mobile Architectures and the 3G Evolution..............................................................7

Generalized View of the Mobile Network Infrastructure .....................................7

Overview of GSM / UMTS Network Architecture .................................................8

The UMTS R3 Network ..................................................................................8

UMTS R4 and R5 Networks ...........................................................................9

Jointly Developed GGSN ................................................................................9

Overview of the CDMA Network Architecture ..................................................10

CDMA RAN ................................................................................................10

CDMA Core Networks .................................................................................10

Understanding the Drivers and Requirements for the Mobile Packet Core ............. 11

Applicability of IP/MPLS to Mobile Architecture ...............................................12

Supporting Traffic and Applications Mix on the Same Network .......................13

Performance Expectations for Mobile Packet Backbone Networks ........................13

Meeting Mobile Packet Core Requirements ......................................................13

Highly Reliable Networks .................................................................................14

QoS and Traffic Management Features .............................................................14

Operations, Administration, and Management .................................................15

MPLS Auto Bandwidth .....................................................................................16

Migrating Legacy ATM Traffic to MPLS ..............................................................16

Supporting BGP/MPLS Layer 3 VPNs on the Mobile Packet Core ......................17

Security ...........................................................................................................17

Network Management and OSS support .........................................................18

How Juniper Enables Service Provider Evolution to Fixed-Mobile Convergence .....18

Conclusion ............................................................................................................19

References and Further Reading ...........................................................................19

Complete List of Acronyms and Terms ..................................................................20

About Juniper Networks ........................................................................................21

Copyright ©2007, Juniper Networks, Inc. �


Executive SummaryThe mobile industry has witnessed explosive growth in number of subscribers, particularly over the past few years. As this paper is being written, there are more than 2.5 billion total subscribers of various mobile technologies, and it is expected that worldwide mobile subscribers will reach close to 4 billion by 2010. However, while usage measured in terms of the number of wireless minutes is increasing, the price per minute for these services is falling. This means that average revenue per user (APRU) is shrinking. Running a profitable business with stagnant or even declining ARPU is one of the fundamental challenges mobile carriers are facing today.

The industry is addressing this challenge in two ways:

• By adding new services or new user experiences for which mobile subscribers are willing to pay. For example, applications driven by the Third-Generation Partnership Project’s (3GPP) IP Multimedia Subsystem (IMS) architectural framework fall into this category.

• By reducing operating expenses (OPEX). At the top of the list is the wireline infrastructure that mobile operators have to maintain regardless of whether they own or lease lines. This includes their core networks, since, for example, Mobile Switching Centers (MSCs) are connected through the Time-division multiplexing (TDM) infrastructure.

Moving to IP-based core networks is a way to leverage both of these approaches. The benefits of IP/MPLS are well known, having been proven in the wireline world with technology that has matured to the point where it is the clear choice for building next- generation networks. An IP/MPLS mobile packet backbone network is an ideal way to reduce OPEX while paving the way for the addition of new services.

Juniper has industry-leading IP expertise that has led to a great deal of success with both wireline and wireless carriers. As illustrated in Figure 1, eleven out of twelve of the world’s top mobile operators are already using Juniper products in their mobile networks.1

Figure 1: Juniper Success in the Mobile Packet Backbone Network

Juniper enables carriers to build cost-effective, flexible, and scalable networks and gives them the ability to leverage a common IP infrastructure in order to increase profitability. Juniper Networks is the market leader in building flexible, service-oriented packet networks. An intelligent, secure, and open IP/MPLS infrastructure with products from Juniper Networks enables service providers to adapt easily as technologies evolve. This flexibility allows service providers to deliver a sustainable set of innovative and secure services both today and into the future.

Equity connections = number customer * ownership share of mobile operator. Eg. AT&T holds 60% share in Cingular with 54 million customers = 32 million equity customers. Process repeated for holdings of other mobile operators.

Leading Mobile Carriers by Equity Connections

Mill

ions

of Sub

scribe

rs

300

250

200

150

100

50

China

Mob

ile

Voda

fone

China

Unic

om

Amer

ica M

ovil

Deutsch

e Te

lekom

Telef

onica

Gro

up

Franc

e Te

lecom

Gro

up

Telec

om It

alia

AT&T

Veriz

on

NTT G

roup

Sing

Tel

-

1Source – Gartner “Market Share: Mobile Equity Connections, Worldwide, 2005 “, published August 2006.

4



Introduction: Global Perspective on the Mobile MarketToday, over a third of the world’s population depends on mobile devices. By the end of 2006, wireless revenues accounted for approximately 49% of all telecommunications services revenue and are expected to grow to 55% of all industry revenue by 2010.

There are two primary ecosystems in the wireless industry: Global System for Mobile Communications (GSM) / Universal Mobile Telecommunications System (UMTS) and Code Division Multiple Access (CDMA). Although GSM has a much wider adoption worldwide, there are still about 300 million subscribers on various CDMA networks.

Today, voice still accounts for the majority of overall cellular traffic, with wireless data exceeding more than 10 percent of mobile operator ARPU. Mobile operator ARPU is under pressure due to price and technology competition from both wireline (for example, voice over IP) and emerging services (for example, voice over Wi-Fi). Although mobile operator ARPU for voice services is declining, the ARPU for data revenues is growing at a healthy rate. In the U.S., during 2006, Verizon Wireless and Cingular both reported data ARPU figures in the range of $5 to $6 per month with healthy growth rates at around 45% per year.

Globally, more and more mobile operators are deploying mobile broadband data services such as High Speed Packet Access (HSPA)2 in UMTS networks and Evolution Data Optimized (EV-DO) in CDMA networks, and as a result are becoming viable competitors in the wired world of DSL and Cable Broadband. HSPA provides higher data rates (up to 14 Mbps in the downlink and 5.8 Mbps in the uplink) that enable operators to offer new applications and an improved user experience (for example: SMS; rapid download of video clips, music tracks, and large high-resolution files; gaming; email; IM; Push-to-talk over cellular). With the availability of these technologies, it is possible to offer simultaneous voice and data services using the same spectrum allocation.

To further their investments in HSPA networks, various operators are intensifying their work with standards bodies such as 3GPP in driving the development of enhanced HSPA (also called HSPA+). This is expected to lead to development of Long Term Evolution (LTE), which aims to achieve peak rates comparable to fast Ethernet rates in the wireline world. The CDMA (3GPP2) contingent has similar development plans involving a technology known as Ultra mobile broadband (UMB). Time Division-Synchronous CDMA (TD-SCDMA) is other variant of 3G development, specifically driven in the Chinese market. It uses the same core network as UMTS.

Worldwide Interoperability for Microwave Access (WiMAX) is a family of interoperable technologies being developed by IEEE and the WiMAX Forum. Higher data rates, wider coverage, and cost-effective wireless broadband service are some of the key drivers for WiMAX. It is publicly endorsed by various carriers such as Sprint Nextel in US and KT in South Korea. Although WiMAX has a standard development lead as compared to LTE/UMB, it has to resolve some critical issues before large scale deployment is possible—for example, uniformity and availability of the spectrum across the globe.

Regardless of the various options, overall mobile architectures are are becoming more data-friendly. Juniper has developed strategic working relationships with leading radio vendors. Our use of open interfaces and our work with partners to develop joint, end-to-end solutions are essential to Juniper’s current and continued success in enabling mobile operators to build highly efficient converged IP/MPLS next-generation core networks.

2HSPA is a 3G mobile broadband data technology based on UMTS. The term HSPA is often used to refer to a combination of two technologies: HSDPA (high speed downlink packet access) and HSUPA (high speed uplink packet access).

Copyright ©2007, Juniper Networks, Inc. 5


1G to 3G and Beyond

Standards bodies such as 3GPP (for GSM networks) and 3GPP2 (for CMDA networks) are actively involved in driving the development of a next-generation wireless system. The high level objective is to create high-speed broadband and IP-based mobile systems featuring network-to-network interconnection, feature/service transparency, global roaming, and seamless services independent of location.

3G (third-generation) mobile systems are defined by International Telecommunications Union (ITU) specification IMT-2000 (International Mobile Telecommunications-2000), a radio and network access specification. 3G is the successor of 2G—the existing and hugely deployed digital mobile system. 2G is the successor of 1G, the original analogue mobile system. GSM is the most predominant choice for 2G deployments.

As highlighted in Figure 2, though voice remains the primary method of mobile communication, a new generation of wireless technologies is now offering higher speed data and multimedia capabilities.

Figure 2: Evolving Voice and Data Technology from 1G to 4G

For easy reference, Table 1 summarizes all of the major technology trends, speeds, and services offered by 1G, 2G, 3G, and beyond.

Generation Mobile Technology/ Switching Method

Deployed System

Examples

Data Band-width Offered (Upper Bound)

Services Offered

1G Analog Cellular / Circuit Switched

AMPS, TACS, NMT

9.6 Kbps Voice

2G Digital Cellular / Circuit Switched

TDMA, GSM, CDMA

14.4 Kbps Voice (main), SMS

2.5G Digital Cellular / Circuit Switched- Packet Enabled

CDMA, GPRS, EDGE, iMODE

(Japan)

144 Kbps Voice and packet data introduced

3G Digital Cellular / Circuit Switched-

voice (later VoIP) and Packet Switched Data

CDMA2000, WCDMA/

UMTS, HSPA, EV-DO

Up to 14Mbps Packet data on high-speed, voice, IMS-enabled multi-media applications

4G Digital Cellular / Packet Data

Enable Packet-based Voice

HSPA+, LTE, EVDO RevC/

UMB, WiMAX

50 to 100 Mbps Mobile broadband, mobile TV, VoD, location-based

services

Table 1: Wireless Generation Summary –Technology and Services Shift

Architectural Evolution

3G UserMobile Broadband

EVDO, HSPA

2.5 GGPRS/GSM

2GDigital Voice

1GAnalogVoice

3G NetworkMSC-MGW Separation

Voice/Signalingon Packet Core

IMS

3G + 4G

LTEUMB

WiMAX

OFDM/MIMO

�



The GSM air interface is a Time Division Multiple Access (TDMA) technology developed as a digital 2G successor to the European analog systems of the 1980s. Improvements over GSM include General Packet Radio Service (GPRS) and Enhanced Data Rates for GSM Evolution (EDGE)—each leveraging the existing GSM infrastructure and spectrum, each promising spectral efficiencies and improved data performance (GPRS up to 114 Kbps; EDGE up to 384 Kbps). EDGE is commercially deployed in around 100 countries worldwide. UMTS is a Wideband Code Division Multiple Access (WCDMA) technology designed as the 3G successor to GSM. Initial WCDMA launches supported data rates up to 384 Kbps. HSDPA offers peak data rates up to 14 Mbps, with high-speed uplink packet access (HSUPA) improving uplink performance beyond 5 Mbps for better performance on interactive services. LTE, UMB and WiMAX are essentially based on Orthogonal Frequency Division Multiple Access (OFDMA) technology for downlink and innovative antenna technologies such as multiple input/multiple output (MIMO) to achieve larger data rates (50 to 100 Mbps) and lower latency.

Making the Case: IP for 3G Mobile Networks

Mobile operators are increasingly competing with wireline operators. In some cases, even the wireline and wireless divisions within the same carriers are competing with each other, as is the case in North America. This is one catalyst for the mobile network evolution to support data-friendly, multimedia applications. Mobile operators are finding that users expect and are starting to demand higher speeds to match DSL/Cable-like experiences, but now with mobility added to the mix.

There is nothing that IP for 3G will enable that cannot already be done in 3G, but at a price. IP is all about lowering costs while leveraging proven success in the wired world and promoting future flexibility in the network. In the IP realm, specific protocols are designed to solve certain problems and can be combined with other (existing or newly developed) protocols to build end-to-end systems. One of the proven mottos of IP—which also fits well with evolving data-centric mobile networks—is the mantra of “IP over everything.” Asynchronous Transfer Mode (ATM), Point-to-Point Protocol (PPP), Ethernet, Synchronous Digital Hierarchy (SDH), Optical fiber and even 3G can be thought of as Layer 2 networks on which IP runs. And everything runs over IP including Transmission Control Protocol (TCP) / User Datagram Protocol (UDP), Real-time Transport Protocol (RTP), Session Initiation Protocol (SIP), and Domain Name Service (DNS).

By contrast, traditional mobile networks are based on architectures that solve complex problems at the core of the network (for example, the mobile switching center). To scale the network to support many more users, much more demanding applications, and much more data, some of this complexity will need to be pushed out to the edge (such as with SIP-enabled phones). This model is similar to the way IP has helped evolve wireline networks for years with end-to-end thinking. In today’s wired packet core networks, edge nodes perform complex functions such as deep packet inspection, security, and traffic compliance actions, while leaving the core to perform very fast packet switching (for example, core ‘P’ routers performing label switching in IP/MPLS core networks).

To enable rich applications such as mobile TV, follow-me TV, location-based services, and voice over IP (VoIP), these applications need to be supported on an end-to-end mobile infrastructure. Reliable and assured transport is essential to achieving the required user experience.



Mobile Architectures and the 3G EvolutionBefore discussing the details of how the packet core infrastructure provides mobile solutions, it is important to first understand a few things about the mobile network architecture and the evolution towards 3G networks. Though the focus of this paper is on the mobile packet backbone network, the end-to-end mobile architecture is relevant and essential in terms of understanding the core. To this end, this section will introduce a generalized wireless architecture to establish some context. Both GSM / UMTS and CDMA architectures are addressed, as packet core network evolution has similar attributes in both architectures, which will be discussed further in the second half of this document.

Generalized View of the Mobile Network Infrastructure

As illustrated in Figure 3, any mobile network infrastructure can be generalized into two main parts: the Radio Access Network (RAN) and the Core Network (CN).

Figure 3: Mobile Network Infrastructure – Generalized View

The RAN consists of a Base Station Transceiver and Base Station Controllers (also known as Radio Network Controllers, or RNCs, according to the terminology of certain networks such as UMTS).

The Core Network can be divided up into an IP Multimedia Subsystem (IMS), a Circuit Switched (CS) domain, and a Packet Switched (PS) domain. IMS is a collection of network elements that provide IP-based multimedia-related services like text, audio, and video. The data related to these services is further transmitted through the PS domain. In short, the Core Network includes the CS, PS, and IMS domains.

A CS-type connection is a traditional telecommunication-style connection with dedicated resources allocated for the duration of the connection. In contrast, in a PS-type connection the information is typically transported in packets and each packet is routed in a distinct and autonomous fashion.

The following sections discuss specific details about GSM, UMTS, and CDMA networks.

Radio AccessNetwork

Radio AccessNetwork

BSC

BSC

BSC

PSTN

Internet

AAA

Circuit Core

Core NetworkRadio AccessNetwork

Packet Core

Base StationControllerBase

Station

SIP

AirInterface

Base StationController

IP MultimediaSubsystem

AAA

8



Overview of GSM / UMTS Network Architecture

The GSM / UMTS network market consists of RAN and CN infrastructures used by service providers to deploy mobile wireless WAN services using the licensed RF spectrum.

The UMTS R3 Network

Various GSM / UMTS network standards have been developed and deployed. Particularly well known are R99 and R4 to R5. Figure 4 illustrates the UMTS R3 architecture, which is based on R99.

Figure 4: UMTS R3 Architecture (Based on R99)

In the RAN, key components include the Base Transceiver Station (BTS) and Base Station Controller (BSC). The respective RANs for GSM and UMTS networks are GERAN (GSM/EDGE Radio Access Network) and UTRAN (UMTS Radio Access Network). Each RNC controls a number of Node Bs.

Core network gear includes MSCs, packet data gateways, and core routing platforms. Architecturally, the RNC sits on the edge of a wireless network and provides RF connectivity to end user terminals. RNCs (BSCs in GSM) manage and aggregate Node B (BTS in GSM) traffic and MSCs groom this traffic onto the Public Switched Telephone Network (PSTN) while also managing handoffs.

Beyond voice, multi-service switches and IP routers provide data transport within the mobile network, with subscriber traffic linked to external data networks using packet data gateways. In GSM, GPRS, and UMTS networks, Gateway GPRS Support Nodes (GGSNs) perform the gateway function. The GGSN has the responsibility of maintaining contact with a mobile subscriber’s equipment as the subscriber moves in the network. Mobility management provided by the GPRS system lets subscribers send packets to Internet hosts and receive responses back—regardless of radio handoffs—as the user moves across cells. The Serving GPRS Support Nodes (SGSNs) essentially switch data streams and perform tunneling. They are responsible for session management, producing charging information, and lawful interception. They also route packets to correct RNCs. The GGSNs perform roles similar to border routers and Authentication, Authorization, and Accounting (AAA), maintaining some service context information and providing billing as traffic is handed off to an applications environment (such as IMS), to the open Internet, or to some other data service. Both the GGSN and SGSN facilitate interworking with external data networks.

PSTN/ISDN

IP-Based PDNUMTS Core Network

UTRAN

RNC

RNC

IP BackboneNetwork

SS7 Network

RadioNetwork

Controller

Node BVLR

Air Interface

GMSC

HLR

GGSNSGSN

MSC

GGSN



On the circuit-switched side, the MSC / Visitor Location Register (VLR) handles circuit management functions and tasks such as location registration. The Gateway Mobile Switching Center (GMSC), on the other hand, acts as a gateway between external networks like the PSTN. It uses the Home Location Register (HLR) to identify which MSC is the serving MSC to set up the call.

UMTS R4 and R5 Networks

Starting from the UMTS R4 architecture defined by 3GPP, traditional circuit MSCs evolve into two components: MSC servers and Media Gateways (MGW). This architecture is also sometimes known as the distributed MSC architecture. In this architecture, the Media Gateway is the element responsible for performing bearer control and transmission switching functions, when they are required. The MSC server is the element controlling the MGW and supports all the control and signaling functions. 3GPP has specified two instances of a Media Gateway Controller, namely the MSC Server and the Gateway MSC Server. The Gateway MSC Server is an MSC Server that controls the connections to other networks—for example, the PSTN. As R4 supports packet-switched voice (VoIP), the circuit-switched calls are converted to packet-switched calls in the MGW.

With this approach, the overall network architecture scales better because MSC servers centralize control plane resources, while MGW nodes can be placed further out in the network closer to radio nodes for efficient use of network transport resources. This keeps the local traffic out of the core and saves on backhauling costs. Communications between the MSC servers and the MGW for signaling and bearer services are optimized around IP/MPLS.

The IP Multimedia Subsystem (IMS) was introduced as standards evolved to R5, where the entire UTRAN is also assumed to be moving to IP-based protocols. IMS promises to facilitate rapid creation of premium multimedia services such as video, audio/VoIP, and location-based services. SIP has been chosen as the signaling/control protocol.

Component GSM Term UMTS Term

Base Station BTS Node-B

Base Station Controller BSC RNC

Circuit Core Devices MSC MSC Server

Packet Core Devices SGSN, GGSN SGSN, GGSN

Table 2: Useful Terminology—GSM / UMTS Networks

Jointly Developed GGSN

Juniper Networks and its strategic partner Ericsson have jointly developed a GGSN (Gateway GPRS Support Node) platform that has been deployed by mobile operators worldwide in their mobile packet transport. The current generation GGSN platform is based on the Juniper M20 router product and supports an industry-leading scalability and performance. It is capable of handling a significant increase in data subscribers as well as growth in the “always-on” GPRS-type product such as Blackberry, and the growing popularity of services like MMS.

10



Overview of the CDMA Network Architecture

The CDMA2000 is another track of 3G standards and has North American origins. The earlier version was known as CdmaOne (2G cdmaOne) and had very limited data capabilities. CDMA2000 introduced higher data rates with technologies such as 1xEV-DO or EV-DO which support high-speed data-only traffic up to 2.4 Mbps. The next revision of EV-DO (known as Rev A) offers 3.1 Mbps downlink while increasing uplink capacity from 192 Kbps to 1.8 Mbps.

As shown in Figure 5, the CDMA network includes the RAN and Core Network infrastructure. Like GSM, CDMA offers voice and data mobile services using the licensed Radio Frequency (RF) spectrum.

Figure 5: CDMA2000 System Architecture

CDMA RAN

The RAN portion of the CDMA network consists of the Base Transceiver Station (BTS) and Base Station Controller (BSC). Architecturally, the BTS sits on the edge of a wireless network and provides RF connectivity to end user terminals. Essentially it controls the interface between the CDMA2000 network and the subscriber unit. BSCs manage and aggregate BTS traffic and MSCs groom this traffic onto the PSTN while managing handoffs.

CDMA Core Networks

CDMA Core network gear includes MSCs, packet data gateways, and core routing platforms. Voice as well as data transport within the mobile network is provided by multi-service switches and IP routers, while subscriber traffic is linked to external data networks using packet data service nodes (PDSNs). The PDSN was introduced in the CDMA2000 architecture and is an essential element in the treatment of packet data service. It is a node that maintains contact with mobile subscribers as they move though the network, informing the network how the subscriber can be reached via the PDSN’s IP interfaces. The PDSN establishes, maintains, and terminates point-to-point protocol (PPP) sessions with subscribers.

PublicTelephoneNetwork

Internet

Private/PublicData Network

BSCHLR

BTS

BTS

BaseStation

Controller

BaseStation

Controller

MSC

BSC

SMS-SC

Firewall

PDSN

AAA

Home Agent



Communicating with the packet control function (PCF) of a BSC, the PDSN terminates PPP sessions for subscribers. If subscribers roam using mobile IP, the PDSN provides the foreign agent (FA) function to register them and receive data from the subscriber’s Home Agent. The PDSN also aids with the AAA function for mobile devices through AAA server(s).

IP routers in the CDMA2000 core route the packets to and from the various elements such as the PDSN, AAA, Home Agent, Internet / Private data networks, and others. For the purpose of this paper, the primary focus will be on the applicability and usability of packet technologies (IP/MPLS) in the core portion of the CDMA network.

Component CDMA 2000/1x Term

Base Station BTS

Base Station Controller BSC

Circuit Core Devices MSC

Packet Core Devices PDSN

Table 3: Useful Terminology – CDMA Networks

Understanding the Drivers and Requirements for the Mobile Packet CoreThe mobile packet backbone network is also subject to evolutionary pressures somewhat similar to those experienced by wired operators when they moved from TDM to Packet (Figure 6). Operators need to control costs but they also need to modernize their voice networks, as legacy voice switches move nearer to obsolescence.

Figure 6: Transformation from TDM World to Packet World

TDM ATMTransport

IP RAN

Cost-effectiveIP/MPLS Backbone

(Voice, Data andSignaling Traffic)

Transformation

12



Also, many operators need to upgrade their best-effort packet-switched cores as differentiated quality of service (QoS) data services and applications mix rise in importance and volume (Figure 7).

Figure 7: Supporting Application Mix in the NGN Packet Core Network

At the same time, carriers have to think about designing service-aware architectures that are aligned with the IMS Next-Generation Network (NGN) infrastructure for the support of end-to-end IP-based services.

Applicability of IP/MPLS to Mobile Architecture

The packet-switched IP backbone was first introduced with 2.5G GPRS networks, and since then most packet-based data services have been built on the underlying assumption of IP. Even today, many of the applications are best-effort in nature (such as text, multimedia messages, and ringtone downloads) and are being served by typical best-effort IP backbones.

However, best-effort is just not good enough for NGN networks, which introduce packet voice traffic, rich Service Level Agreement (SLA)-driven applications, and elevated user expectations for service quality, as mobile broadband offers bigger pipes.

Figure 8: Common IP/MPLS Backbone

MMS

SMS/MMS

$$

Location-basedServices

CorporateIntranet & Email

eCommerce

Gaming andEntertainment

Data Services andWireline Displacement

PacketVoice

CircuitVoice

PSTNIP/ATM/TDM

IP/MPLSMobile Backbone

OtherPLMN/GRX

RVC/BSC

IuNetwork

GnNetwork

GaNetworkGp

ISP

CorporateSite

Charging/Billing OSS

GiNetwork

IP/MPLS

Convergence

GGSN

RNC/BSCSGSN

SGSN

MSC

MSC

Gateway

Voice

Gateway

Voice

Copyright ©2007, Juniper Networks, Inc. 1�


As shown in the GSM / UMTS example in Figure 8, instead of operating separate networks for specific interfaces, all of these logical networks can be supported on a common converged core, and the feature-rich IP/MPLS packet core is an obvious choice.

Supporting Traffic and Applications Mix on the Same Network

Mobile architectures are evolving to support voice and data on the same infrastructure. They are also combining voice signaling (traditional SS7 out-of-band traffic, in many cases carried on a separate network from bearer traffic) on a converged mobile packet backbone. This mobile backbone must support several types of traffic and services:

• User plane traffic, such as delay-sensitive voice traffic between media gateways and packet data traffic

• Signaling plane traffic, such as between MSC servers and Media Gateways, and other SIGTRAN traffic

• Additional operations, administration, and maintenance traffic such as network configurations, bulk statistics, and software upgrades

• A variety of new services, ranging from best-effort, location-based IMS services to mission critical business applications

• Seamless transport of ATM (AAL2/AAL5) traffic over the MPLS core, which can mean inter-RNC traffic as well as traffic going from one MSC site to another

The variety of traffic and services delivery demands placed on the network mean that it must provide highly reliable transport and powerful QoS and performance guarantees.

Performance Expectations for Mobile Packet Backbone NetworksThe following table presents some rough guidelines for mobile operator performance requirements based on industry deployment scenarios and business needs driven by Service Level Agreements (Table 4):

Requirement Bound

End-to-end Latency <> 50 ms

Service Availability <> 99.999%

Average Packet Loss Allowed <> 10 ^ -5

Delay Variation (Jitter) <> 1 to 5 ms

Packet Reordering None

Max Link Failover Time <> 1s

Table 4: Example Mobile Operator Performance Requirements

Meeting Mobile Packet Core Requirements

As discussed above, the NGN packet backbone must shed the “best effort” mentality, as it has many new requirements to meet. This new set of requirements can be divided into the following categories:

• High degree of robustness, reliability and availability

• Better network resource management (guaranteed QoS, traffic engineering)

• Powerful operational tools

• Scalability

• Security

• Ability to enable new applications

• Future-proof investment (for example, support for evolving standards such as IMS / MMD)

14



The following sections will cover these requirements in detail and discuss how Juniper’s mobile packet backbone solutions address them.

Highly Reliable Networks

IP/MPLS networks have reached maturity, having now been deployed by many wireline carriers globally. The traditional perception that IP-based networks lack ATM/TDM-like reliability has generally been refuted. But true carrier-grade availability is still only achieved if it is supported at the individual network element level (at each link failure) as well as at the network level.

Juniper Networks routers support a full MPLS feature set for highly reliable, carrier-grade IP-MPLS networks. At each network element level, Juniper routers achieve high availability by supporting features such as non-stop routing, which maintains routing during Routing Engine (RE) switchover and provides a self-contained mechanism that, unlike Graceful Restart, does not require participation from neighboring nodes. Juniper also supports RE redundancy, where the backup routing engine offers redundancy and takes over the role of primary RE without interrupting the forwarding of packets within the router. This is possible because Juniper inherently supports separation of control and forwarding in the routing architecture. Additionally, Graceful Restart is supported for OSPF, BGP, LDP, RSVP, ISIS, RIP, and other protocols. This Internet Engineering Task Force (IETF) standards-based solution allows recovery from control plane failures in a deterministic way and without interrupting packet forwarding.

To handle link failures between the various mobile core elements, Juniper routers use interrupt-driven link-down notification, which can trigger locally attached systems to declare the interface down within a few milliseconds of failure. Operators can move traffic onto an alternative path in one of two ways, depending on the sense of urgency in the network and the willingness to pay an additional price for improved restoration time. Operators can rely solely on the Interior Gateway Protocol (IGP), or, alternatively, enhance restoration time by mechanisms such as MPLS Fast Reroute (FRR), which works based on the RSVP-TE mechanism. A combination of carefully engineered primary and secondary Label Switched Paths (LSPs) and the FRR capability allow restoration targets to be achieved in only tens of milliseconds. Other Juniper features such as ISSU (In Service Software Upgrade) are also planned. This feature will be particularly important in mobile carrier environments where maintenance windows become difficult or impossible to schedule. ISSU will be essential to achieving five 9’s availability. With ISSU, a complete JUNOS package can be upgraded with minimal disruption to packet forwarding.

QoS and Traffic Management Features

Mobile networks require strict priority queuing and low latency, particularly for mobile backbones that carry voice traffic and video as well as some of the new IMS-based services. These requirements demand a service-oriented approach to routing rather than just best-effort forwarding.

Juniper’s purpose-built, ASIC-based architecture, powerful JUNOS, and traffic management features handle voice quality traffic through low latency and strict-priority queuing. Traffic engineering furnishes critical capabilities for SLA enforcement. Constraint-based routing helps carriers exert much greater control over how to route traffic through the network. It enables them to be very specific in selecting the most efficient path—for example, they can base their decision on more than simple source and destination information and instead pinpoint precisely which LSP traffic should travel. This ensures that delay-sensitive voice, for example, won’t run over a congested link when other alternatives are available. It also ensures that the bandwidth proportion across links remains constant.

Admission control per class for Layer 2 and Layer 3 environments allows carriers to define the amount of bandwidth assigned per class of service (CoS). In essence, this enables the network to make use of different bandwidth pools to ensure that there is always sufficient bandwidth for the



traffic that needs it the most. There is also overbooking per class, which permits extra bandwidth to be assigned to a specific CoS when it is needed. And policies help carriers keep a close eye on each CoS as it travels through an LSP to make sure it doesn’t exceed the allocation it’s received. Juniper routers also classify packets at the ingress port and, based on multiple fields, can determine CoS and priority. Classification is based on the IETF Differentiated Services (DiffServ) standard and classifications are honored (or potentially changed by policy) on a per-hop basis across the mobile backbone.

Juniper queuing and scheduling techniques offer deterministic delay and help operators meet tight jitter performance bounds. In tests conducted to assess the latency and jitter performance of Juniper’s M320 router (widely deployed in many mobile packet cores), high priority traffic (simulating real-time voice) of 40 byte packets was sent to an output interface loaded at 90 percent of the interface bandwidth. Best-effort traffic was also sent to the same interface to significantly oversubscribe the interface bandwidth. The result was that no high priority packets were dropped and the latency of each high priority packet was easily in the required range. Even with large data packet sizes as big as 4K bytes, the maximum latency observed was less than 50 microseconds and delay variation was below 25 microseconds.

Operations, Administration, and Management

Historically, carriers have viewed high operating expenses resulting from complex troubleshooting as a major barrier to the deployment of converged services over IP/MPLS. Partly, this concern has to do with a lack of sophisticated operations, administration, and management (OA&M) tools in the IP/MPLS infrastructure. Juniper offers many powerful, standards-based and easy to deploy OA&M features that reduce troubleshooting time and make it possible to deliver premium services that require short restoration times.

Juniper routers also support LSP Ping to test LSP connectivity between ingress and egress routers in each direction, and do so in a manner that is transparent to the transit MPLS nodes. These routers support LSP Trace Route, which invokes a hop-by-hop procedure to trace a defect-free LSP and locate defects. In addition, Juniper routers support Bidirectional Forwarding Detection (BFD) mechanisms (Figure 9) for the detection of forwarding-plane-to-forwarding-plane connectivity.

Figure 9: Bidirectional Forwarding Detection (BFD) for MPLS LSPs

BDF is essentially a liveliness mechanism to ensure that the forwarding state is intact along the end-to-end MPLS LSP, since it is possible that even if all seems well from the control plane point of view, there could be an issue in the forwarding plane. In protocol operations, the ingress router generates periodic BDF packets (LSP is unidirectional) that are sent along the LSP. The egress router, upon receiving each BFD packet, sends a corresponding BFD packet in response. If more than a certain consecutive number of BFD packets are lost, a warning message is generated for higher levels to take appropriate action.

TunnelMPLS Psuedowire

ATM/FRAccess

ATM/FRAccess

MPLS Network

Segment ATM OAM LDP/BGP Signaling Session

Periodic BDF Fault Detection on Tunnel LSP and/or MPLS PW

Switch

ATM

Switch

ATM

Switch

ATM

Switch

ATM

1�



MPLS Auto Bandwidth

With the help of auto bandwidth support, mobile operators can automatically adjust the LSP bandwidth based on the actual traffic flowing through the LSP. An LSP can be set up with some arbitrary (or zero) bandwidth value. The network element supporting the LSP automatically monitors the average traffic flow and adjusts its bandwidth every “adjust-interval” period. In this process, the traffic flow is not interrupted, as the LSP follows the “make-before-break” signaling mechanism. As a guideline, some mobile operators have used a 24- hour adjustment interval, and an adjust-threshold value between 5% and 10% of the current LSP bandwidth.

Migrating Legacy ATM Traffic to MPLS

Traditionally, many of the deployed GSM/UMTS (R99) wireless core networks have been ATM transport networks owned by the wireless carriers. As in the wireline world, simplified operations, greater service flexibility, and increased scalability are driving the migration to MPLS.

Several standards organizations including the Internet Engineering Task Force (IETF), the International Telecommunication Union (ITU), and the MFA Forum (MPLS, Frame Relay and ATM Forum) have devoted considerable time and energy to developing solutions for migrating ATM, frame relay, and other legacy services to MPLS. In the midst of so much activity, the challenge for mobile operators is to determine which migration strategy best suits their current customers and applications, as well as their future service strategies. There are three primary options from which mobile operators can choose:

• Creating a separate MPLS core and using standards-based Layer 3 virtual private networks (VPNs) to migrate native ATM / Frame Relay services onto the new MPLS network

• Creating a separate MPLS core and using IETF pseudowires (Layer 2 VPN) to migrate native ATM/frame relay services onto MPLS

• Inserting an MPLS core between existing ATM networks, and tunneling ATM signaling and routing capabilities through MPLS to seamlessly transport Layer 2 services

Juniper supports all of these options.

As discussed earlier in the UMTS overview section and as shown in Figure 10, UMTS R99 architecture is based on ATM.

Figure 10: UMTS R99, ATM-heavy Architecture

Many mobile operators have used Layer 2 VPN technology based on emulation of end-to-end pseudowires to enable carriers to introduce MPLS seamlessly within existing ATM networks. Pseudowires combine MPLS forwarding and IP routing to emulate ATM services and to transport the traffic while preserving ATM-like user experiences.

PSTN

InternetCorporate

Common MPLSNetwork

AAL2 ATM

3G MSC

AAL2 ATM AAL2 ATM

IP/AAL5ATM STM-1

Radio NetworkController

IP

lu b lu cs

Gn Gi

lu r

lu ps

RNC

RNC

HLR

USIM

Node BAuC

SCP

GGSN

SGSN

MSC MSC

GGSN



Figure 11: Layer 2 VPN in the Mobile Core—Carrying ATM over MPLS

As illustrated in Figure 11, traditional ATM interfaces at the RNC, MSC complex, and at the SGSN are still preserved, and MPLS is seamlessly introduced by carrying ATM VC over the MPLS core as pseudowires. Juniper supports LDP-based as well as BGP-based Layer 2 VPNs (also known as Kompella). Standards bodies such as the MFA Forum have developed specifications that handle control plane interworking between ATM/Frame Relay and MPLS networks. Juniper, along with our strategic partners, has been involved in developing these specifications and has pre-standard implementation. This approach decouples ATM and the MPLS control plane and enables them to evolve and be deployed independently.

Supporting BGP/MPLS Layer 3 VPNs on the Mobile Packet Core

Today, many mobile operators are using Juniper’s best-in-class, industry-leading Layer 3 VPN (RFC 4364) technology in their mobile packet backbone networks. This allows them to support manageable, scaleable, and well-isolated VPNs. For example, different VPNs offer easy grouping and logical separation for various services and/or interfaces. Examples for separate VPNs are created for SIGTRAN traffic, charging/billing traffic (Ga), GPRS user traffic between SGSN and GGSN (Gn interface), and mobile operator internal IT and network management traffic. VPNs also enable virtual business models, where different branded mobile operators can use the same basic infrastructure and mobile operators can selectively allow access by their partners to certain assets in their networks.

With an investment in an IP/MPLS packet core, mobile operators can offer new services as business connectivity to their enterprise customers and in this way stay competitive with wireline operators.

Security

Moving to an IP-based infrastructure does bring some additional security concerns, such as Denial of Service (DoS) and Distributed Denial of Service (DDoS) attacks, which can potentially interrupt thousands of voice calls and other high revenue and critical services. Juniper routing platforms have hardware-based packet forwarding and filtering ASICs so that traffic can be controlled through line-rate filters on packets passing through the routing platform. This provides protocol-based firewalls that prevent DDoS and DoS attacks, falsification of source addresses, and implement traffic shaping and policing.

MPLS Tunnel

RNC SGSN

MSC

MPLS Tunnel

MPLS Tunnel

BGP or LDP

ATM VC

ATM VCATM VC

VirtualRouting

Forwarding

VRFVRFRadio NetworkController

Mobile Core

18



Juniper firewalls (such as the ISG 2000) with integrated Intrusion Detection and Protection (IDP) provide protection on both the network and application layers. They can also be used to protect OA&M and billing data from attacks. Juniper IDP solutions use Multi-Method Detection techniques with eight different detection methods, including protocol anomaly detection and traffic anomaly detection. Our IDP solution operates in-line and allows operators to create new and unique signatures.

Network Management and OSS Support

Network elements and resource management tools and mechanisms to manage IP networks are essential for mobile operators, who are generally accustomed to managing circuit-switched networks. The JUNOScope IP service manager provides a framework that consists of tools for managing IP services for the M- and T-Series routing platforms, providing configuration management, inventory management, and system administration. Communication between JUNOScope and the managed routers is based on the NETCONF specification running over Extensible Markup Language (XML). Also, Juniper and its Operations Support System (OSS) alliance partners support a complete set of field-proven FCAPS (fault-management, configuration, accounting, performance, and security) products—for example, Redcell EMS, Net cool performance management systems, and others.

Juniper routers also support features to ease monitoring of the network. For example, port monitoring features enable operators to gain visibility into traffic traversing the network without impacting line performance. They do so by replicating the entire packet and sending it to the offline tool for monitoring.

As IP is being pushed further away from the core, the required IP skill set may not be readily available at all remote locations. In such a transition period, intuitive, service-aware tools are essential. Such tools also work with offline engineering tools that are coupled into the Network Monitoring System (NMS). It is important to note that Juniper Networks operations support systems (NMS-OSS) alliance partners develop applications that extend the functionality of Juniper’s products to deliver robust and flexible network management solutions.

How Juniper Enables Service Provider Evolution to Fixed-Mobile Convergence

For more than 10 years, Juniper Networks has been helping service providers evolve to a secure, converged IP infrastructure by providing industry-leading routing and security equipment and by working closely with strategic partners to integrate our products into end-to-end solutions. Juniper’s mobile packet backbone network solutions do more than just build an infrastructure for the current needs of mobile operators, they also create a future-proof infrastructure that supports seamless migration to emerging fixed mobile convergence (FMC) based on the IP Multimedia Subsystem (IMS). Our solutions are fully compliant with standards issued by major standards organizations and enable carriers to evolve their networks as next-generation architectures continue to develop. These solutions are designed to address all of the key challenges faced by mobile operators in their migration from circuit-switched technologies—from the introduction of mobile softswitching through the deployment of IP transport and the evolution to IMS-based FMC networks. Our mobile packet backbone solutions feature necessary openness and scalability to enable successful carrier transition to an IP/MPLS backbone and preparation for the evolution to IMS-FMC.



ConclusionRegardless of whether a mobile carrier is deploying 3G or thinking of 4G, or whether they are deploying UMTS or CDMA, they will be faced with the reality that mobile core and backhaul architectures are evolving towards all-IP. Mobile technology is moving rapidly towards 2.5G and 3G technologies. Any IP-based architecture that is installed today must demonstrate best-in-class traffic engineering, reliability and scalability features. It must keep up with the current mobile standards and be designed to support the planned evolution of these standards.

Juniper products deliver carrier-grade reliability, offer a smooth migration path for mobile providers transitioning from TDM-like infrastructures to packet-switched infrastructures, and provide unmatched performance and features in the IP infrastructure. We enable mobile carriers to build more cost effective, flexible, and scalable networks, leveraging a common IP infrastructure that increases profitability in the following ways:

• By allowing new higher-margin services to be introduced more economically, rapidly, and flexibly than before

• By reducing operating expenses associated with managing multiple networks that each depend on different technologies

• By leveraging existing carrier investments to create bundled services

• By maintaining a single Authentication, Authorization, and Accounting (AAA) system for all users, regardless of which network resources they use

• By minimizing the security, reliability, and scalability risks associated with traditional IP networks.

References and Further ReadingIntroducing MPLS Layer 3 VPNs in Mobile Operator Networks

http://www.juniper.net/solutions/literature/app_note/350058.pdf

The Use of Virtual Trunks for ATM/MPLS Control Plane Interworking Specification, by Peter Busschbach and Nikhil Shah

http://www.mfaforum.org/tech/mpls_ia.shtml

Using MPLS Auto-bandwidth in MPLS Networks, by Ariff Premji

http://www.juniper.net/solutions/literature/app_note/350080.pdf

20



Complete List of Acronyms and Terms3GPP: 3rd Generation Partnership Project (Standards Body)

AAA: Authentication, Authorization and Accounting

Security system that determines user identity and privilege level and tracks user activities.

ATIS: Alliance for Telecommunications Industry Solutions (North American Standards Body)

BSC: Base Station Controller

BDF: Bi-directional Forwarding Detection

BTS: Base Transceiver Station

CAC: Call Admission Control

CDMA: Code Division Multiple Access

CS: Circuit Switched

FMC: Fixed Mobile Convergence

GGSN: Gateway GPRS Support Node

GPRS: General Packet Radio Service

GRX: GPRS Roaming Exchange

GSM: Global System for Mobile communications

GTP: GPRS Tunneling Protocol

HLR: Home Location Register

Stores subscriber data relating to services and features in addition to location area information.

HSS: Home Subscriber Server

Master database for the PLMN, made up of several physical databases depending on the number of subscribers and the supported services. Holds variables and identities for the support, establishment and maintenance of subscriber initiated sessions and calls.

IDP: Intrusion Detection and Prevention

IETF: Internet Engineering Task Force (Standards Body)

IMS: IP Multimedia Subsystem

ITU-T: International Telecommunications Union (Standards Body)

LTE: Long Term Evolution

MGW: Media Gateway Function

SoftSwitch element that provides a gateway to support both bearer and signaling traffic. Media Gateways enable multimedia communications across NGN (Next Generation Networks) over multiple transport protocols. Multiple Media Gateways are controlled by a Media Gateway Controller, which provides call control and signaling functionality.

MPLS: Multiprotocol Label Switching

MS: Mobile Station

MSC: Mobile Switching Center

MVNO: Mobile Virtual Network Operator

NAT: Network Address Translation

OFDM: Orthogonal Frequency Division Multiple Access



PLMN: Public Land Mobile Network

PSTN: Public Switched Telephone Network

RAN: Radio Access Network

RNC: Radio Network Controller

SGW: Signaling Gateway

SGSN: Serving GPRS Support Node

TISPAN: Telecoms & Internet Converged Services & Protocols for Advanced Networks (Standards Body)

Formed from the previous ETSI working groups of TIPHON and SPAN.

UMB: Ultra mobile broadband (new name adopted for EVDO RevC)

UMTS: Universal Mobile Telecommunications System

VRF: Virtual routing forwarding

WCDMA: Wideband Code Division Multiple Access

WiBro: Wireless Broadband

Wireless broadband internet technology being developed by the Korean telecoms industry. In contrast to WiMAX (an American Wireless technology), WiBro uses licensed radio spectrum.

Wi-Fi: Wireless Fidelity

Wi-Fi certification encompasses numerous different standards, including 802.11a, 802.11b, 802.11g, WPA, and more, and equipment must pass compatibility testing to receive the Wi-Fi mark.

WiMAX: Worldwide Interoperability for Microwave Access

Another name for the 802.16 wireless networking specification used for long-haul and backhaul connections.

WLAN: Wireless LAN

About Juniper NetworksJuniper Networks develops purpose-built, high-performance IP platforms that enable customers to support a wide variety of services and applications at scale. Service providers, enterprises, governments and research and education institutions rely on Juniper to deliver a portfolio of proven networking, security and application acceleration solutions that solve highly complex, fast-changing problems in the world’s most demanding networks. Additional information can be found at www.juniper.net. For comments or questions, please email [email protected].

Copyright 2007, Juniper Networks, Inc. All rights reserved. Juniper Networks and the Juniper Networks logo are registered trademarks of Juniper Networks, Inc. in the United States and other countries. All other trademarks, service marks, registered trademarks, or registered service marks in this document are the property of Juniper Networks or their respective owners. All specifications are subject to change without notice. Juniper Networks assumes no responsibility for any inaccuracies in this document or for any obligation to update information in this document. Juniper Networks reserves the right to change, modify, transfer, or otherwise revise this publication without notice.

PCN Juniper Networks

Documents

Transcript of PCN Juniper Networks