pcn juniper networks14

7/28/2019 PCN Juniper Networks14

1/21


2/21

2

Building Next-Generation Mobile Packet Core Networks

Copyright 2007, Juniper Networks, Inc.

Table of Contents

Executive Summary ................................................................................................3

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

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

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

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

Generalized View o the Mobile Network Inrastructure .....................................7

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

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

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

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

Overview o the CDMA Network Architecture ..................................................10

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

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

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

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

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

Perormance Expectations or Mobile Packet Backbone Networks ............... .........13

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

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

QoS and Trac Management Features ............. .............. ............. .............. .......14

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

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

Migrating Legacy ATM Trac 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

Reerences and Further Reading ...........................................................................19

Complete List o Acronyms and Terms .............. ............. .............. .............. ...........20

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


3/21



Executive Summary

The mobile industry has witnessed explosive growth in number o subscribers, particularly

over the past ew years. As this paper is being written, there are more than 2.5 billion total

subscribers o 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 o the number owireless minutes is increasing, the price per minute or these services is alling. This means that

average revenue per user (APRU) is shrinking. Running a protable business with stagnant or

even declining ARPU is one o the undamental challenges mobile carriers are acing today.

The industry is addressing this challenge in two ways:

By adding new services or new user experiences or which mobile subscribers are willing

to pay. For example, applications driven by the Third-Generation Partnership Projects

(3GPP) IP Multimedia Subsystem (IMS) architectural ramework all into this category.

By reducing operating expenses (OPEX). At the top o the list is the wireline inrastructure

that mobile operators have to maintain regardless o whether they own or lease lines.

This includes their core networks, since, or example, Mobile Switching Centers (MSCs)

are connected through the Time-division multiplexing (TDM) inrastructure.

Moving to IP-based core networks is a way to leverage both o these approaches. The benets

o 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 or building next- generation networks. An

IP/MPLS mobile packet backbone network is an ideal way to reduce OPEX while paving the way

or the addition o new services.

Juniper has industry-leading IP expertise that has led to a great deal o success with both

wireline and wireless carriers. As illustrated in Figure 1, eleven out o twelve o the worlds 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-eective, fexible, and scalable networks and gives them the

ability to leverage a common IP inrastructure in order to increase protability. Juniper Networks

is the market leader in building fexible, service-oriented packet networks. An intelligent, secure,

and open IP/MPLS inrastructure with products rom Juniper Networks enables service providers

to adapt easily as technologies evolve. This fexibility allows service providers to deliver a

sustainable set o innovative and secure services both today and into the uture.

Leading Mobile Carriers by Equity Connections

MillionsofSubscribers

300

250

200

150

100

50

China

Mob

ile

Voda

fone

China

Unic

om

America

Mov

il

Deut

sche

Telek

om

Tele

fonic

aGr

oup

France

Telec

omGro

up

Telec

omItali

aAT

&T

Veriz

on

NTT

Grou

p

Sing

Tel

-

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


4/21

4



Introduction: Global Perspective on the Mobile Market

Today, over a third o the worlds population depends on mobile devices. By the end o 2006,

wireless revenues accounted or approximately 49% o all telecommunications services revenue

and are expected to grow to 55% o all industry revenue by 2010.

There are two primary ecosystems in the wireless industry: Global System or 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 or the majority o overall cellular trac, with wireless data exceeding

more than 10 percent o mobile operator ARPU. Mobile operator ARPU is under pressure due to

price and technology competition rom both wireline (or example, voice over IP) and emerging

services (or example, voice over Wi-Fi). Although mobile operator ARPU or voice services is

declining, the ARPU or data revenues is growing at a healthy rate. In the U.S., during 2006,

Verizon Wireless and Cingular both reported data ARPU gures in the range o $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 o

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 oer new applications and an improved

user experience (or example: SMS; rapid download o video clips, music tracks, and large

high-resolution les; gaming; email; IM; Push-to-talk over cellular). With the availability o

these technologies, it is possible to oer simultaneous voice and data services using the same

spectrum allocation.

To urther their investments in HSPA networks, various operators are intensiying their work

with standards bodies such as 3GPP in driving the development o enhanced HSPA (also

called HSPA+). This is expected to lead to development o Long Term Evolution (LTE), which

aims to achieve peak rates comparable to ast 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 o 3G

development, specically driven in the Chinese market. It uses the same core network as UMTS.

Worldwide Interoperability or Microwave Access (WiMAX) is a amily o interoperable

technologies being developed by IEEE and the WiMAX Forum. Higher data rates, wider

coverage, and cost-eective wireless broadband service are some o the key drivers or 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 beore large scale deployment is possibleor example, uniormity and

availability o the spectrum across the globe.

Regardless o the various options, overall mobile architectures are are becoming more data-

riendly. Juniper has developed strategic working relationships with leading radio vendors. Our

use o open interaces and our work with partners to develop joint, end-to-end solutions are

essential to Junipers current and continued success in enabling mobile operators to build highly

ecient converged IP/MPLS next-generation core networks.

2HSPA is a 3G mobile broadband data technology based on UMTS. The term HSPA is oten used to reer to a combination o

two technologies: HSDPA (high speed downlink packet access) and HSUPA (high speed uplink packet access).


5/21

Copyright 2007, Juniper Networks, Inc. 5


1G to 3G and Beyond

Standards bodies such as 3GPP (or GSM networks) and 3GPP2 (or CMDA networks) are actively

involved in driving the development o a next-generation wireless system. The high level

objective is to create high-speed broadband and IP-based mobile systems eaturing network-to-

network interconnection, eature/service transparency, global roaming, and seamless servicesindependent o location.

3G (third-generation) mobile systems are dened by International Telecommunications Union

(ITU) specication IMT-2000 (International Mobile Telecommunications-2000), a radio and

network access specication. 3G is the successor o 2Gthe existing and hugely deployed digital

mobile system. 2G is the successor o 1G, the original analogue mobile system. GSM is the most

predominant choice or 2G deployments.

As highlighted in Figure 2, though voice remains the primary method o mobile communication,

a new generation o wireless technologies is now oering higher speed data and multimedia

capabilities.

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

For easy reerence, Table 1 summarizes all o the major technology trends, speeds, and services

oered by 1G, 2G, 3G, and beyond.

Generation Mobile Technology/Switching Method

DeployedSystem

Examples

Data Band-width Offered(Upper Bound)

ServicesOffered

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 packetdata introduced

3G Digital Cellular /Circuit Switched-

voice (later VoIP) andPacket Switched Data

CDMA2000,WCDMA/

UMTS, HSPA,EV-DO

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

4G Digital Cellular /Packet Data

Enable Packet-basedVoice

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 Shit

Architectural Evolution

3G User

Mobile Broadband

EVDO, HSPA

2.5 G

GPRS/GSM

2G

Digital Voice

1G

Analog

Voice

3G Network

MSC-MGW Separation

Voice/Signaling

on Packet Core

IMS

3G + 4G

LTE

UMB

WiMAX

OFDM/MIMO


6/21



The GSM air interace is a Time Division Multiple Access (TDMA) technology developed as a

digital 2G successor to the European analog systems o the 1980s. Improvements over GSM

include General Packet Radio Service (GPRS) and Enhanced Data Rates or GSM Evolution

(EDGE)each leveraging the existing GSM inrastructure and spectrum, each promising spectral

eciencies and improved data perormance (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 oers peak data rates up to 14

Mbps, with high-speed uplink packet access (HSUPA) improving uplink perormance beyond

5 Mbps or better perormance on interactive services. LTE, UMB and WiMAX are essentially

based on Orthogonal Frequency Division Multiple Access (OFDMA) technology or 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 or 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 thecase in North America. This is one catalyst or the mobile network evolution to support data-

riendly, multimedia applications. Mobile operators are nding 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 or 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

uture fexibility in the network. In the IP realm, specic 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 o the proven mottos o IPwhich also ts well with evolving data-centric

mobile networksis the mantra o IP over everything. Asynchronous Transer Mode (ATM),

Point-to-Point Protocol (PPP), Ethernet, Synchronous Digital Hierarchy (SDH), Optical ber and

even 3G can be thought o 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 o the network (or example, the mobile switching center). To scale the network to

support many more users, much more demanding applications, and much more data, some o

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 or years with end-to-end

thinking. In todays wired packet core networks, edge nodes perorm complex unctions such

as deep packet inspection, security, and trac compliance actions, while leaving the core to

perorm very ast packet switching (or example, core P routers perorming label switching in

IP/MPLS core networks).

To enable rich applications such as mobile TV, ollow-me TV, location-based services, and voice

over IP (VoIP), these applications need to be supported on an end-to-end mobile inrastructure.

Reliable and assured transport is essential to achieving the required user experience.


7/21



Mobile Architectures and the 3G Evolution

Beore discussing the details o how the packet core inrastructure provides mobile solutions,

it is important to rst understand a ew things about the mobile network architecture and the

evolution towards 3G networks. Though the ocus o this paper is on the mobile packet backbone

network, the end-to-end mobile architecture is relevant and essential in terms o understandingthe 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 urther in the

second hal o this document.

Generalized View o the Mobile Network Inrastructure

As illustrated in Figure 3, any mobile network inrastructure can be generalized into two main

parts: the Radio Access Network (RAN) and the Core Network (CN).

Figure 3: Mobile Network Inrastructure Generalized View

The RAN consists o a Base Station Transceiver and Base Station Controllers (also known as

Radio Network Controllers, or RNCs, according to the terminology o 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 o network elements that

provide IP-based multimedia-related services like text, audio, and video. The data related to

these services is urther 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 or the duration o the connection. In contrast, in a PS-type connection

the inormation is typically transported in packets and each packet is routed in a distinct and

autonomous ashion.

The ollowing sections discuss specic details about GSM, UMTS, and CDMA networks.

Radio Access

Network

Radio Access

Network

BSC

BSC

BSC

PSTN

Internet

AAA

Circuit Core

Core NetworkRadio AccessNetwork

Packet Core

Base Station

ControllerBase

Station

SIP

Air

Interface

Base Station

Controller

IP Multimedia

Subsystem

AAA


8/21


9/21



On the circuit-switched side, the MSC / Visitor Location Register (VLR) handles circuit management

unctions 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 identiy which MSC is the serving MSC to set up the call.

UMTS R4 and R5 NetworksStarting rom the UMTS R4 architecture dened 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 or perorming bearer control and transmission switching unctions, when they are

required. The MSC server is the element controlling the MGW and supports all the control and

signaling unctions. 3GPP has specied two instances o 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 networksor 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 urther out in the network closer to

radio nodes or ecient use o network transport resources. This keeps the local trac out o the

core and saves on backhauling costs. Communications between the MSC servers and the MGW

or 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 acilitate rapid

creation o 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: Useul TerminologyGSM / UMTS Networks

Jointly Developed GGSN

Juniper Networks and its strategic partner Ericsson have jointly developed a GGSN (Gateway

GPRS Support Node) platorm that has been deployed by mobile operators worldwide

in their mobile packet transport. The current generation GGSN platorm is based on the

Juniper M20 router product and supports an industry-leading scalability and perormance.

It is capable o handling a signicant increase in data subscribers as well as growth in the

always-on GPRS-type product such as Blackberry, and the growing popularity o services

like MMS.


10/21

10



Overview o the CDMA Network Architecture

The CDMA2000 is another track o 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 trac up to 2.4 Mbps. The next revision o EV-DO (known as RevA) oers 3.1 Mbps downlink while increasing uplink capacity rom 192 Kbps to 1.8 Mbps.

As shown in Figure 5, the CDMA network includes the RAN and Core Network inrastructure.

Like GSM, CDMA oers voice and data mobile services using the licensed Radio Frequency

(RF) spectrum.

Figure 5: CDMA2000 System Architecture

CDMA RAN

The RAN portion o the CDMA network consists o the Base Transceiver Station (BTS) and Base

Station Controller (BSC). Architecturally, the BTS sits on the edge o a wireless network and

provides RF connectivity to end user terminals. Essentially it controls the interace between the

CDMA2000 network and the subscriber unit. BSCs manage and aggregate BTS trac and MSCs

groom this trac onto the PSTN while managing handos.

CDMA Core Networks

CDMA Core network gear includes MSCs, packet data gateways, and core routing platorms.

Voice as well as data transport within the mobile network is provided by multi-service switches

and IP routers, while subscriber trac 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 o packet data service. It is a node that maintains contact withmobile subscribers as they move though the network, inorming the network how the subscriber

can be reached via the PDSNs IP interaces. The PDSN establishes, maintains, and terminates

point-to-point protocol (PPP) sessions with subscribers.

Public

Telephone

Network

Internet

Private/Public

Data Network

BSCHLR

BTS

BTS

Base

Station

Controller

Base

Station

Controller

MSC

BSC

SMS-SC

Firewall

PDSN

AAA

Home Agent


11/21



Communicating with the packet control unction (PCF) o a BSC, the PDSN terminates PPP

sessions or subscribers. I subscribers roam using mobile IP, the PDSN provides the oreign

agent (FA) unction to register them and receive data rom the subscribers Home Agent. The

PDSN also aids with the AAA unction or mobile devices through AAA server(s).

IP routers in the CDMA2000 core route the packets to and rom the various elements such as the

PDSN, AAA, Home Agent, Internet / Private data networks, and others. For the purpose o this

paper, the primary ocus will be on the applicability and usability o packet technologies (IP/

MPLS) in the core portion o 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: Useul Terminology CDMA Networks

Understanding the Drivers and Requirements for the Mobile Packet Core

The mobile packet backbone network is also subject to evolutionary pressures somewhat similar

to those experienced by wired operators when they moved rom 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: Transormation rom TDM World to Packet World

TDM ATM

Transport

IP RAN

Cost-effective

IP/MPLS Backbone

(Voice, Data and

Signaling Traffic)Transformation


12/21

12



Also, many operators need to upgrade their best-eort packet-switched cores as dierentiated

quality o 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) inrastructure or the support o end-to-endIP-based services.

Applicability o IP/MPLS to Mobile Architecture

The packet-switched IP backbone was rst introduced with 2.5G GPRS networks, and since

then most packet-based data services have been built on the underlying assumption o IP. Even

today, many o the applications are best-eort in nature (such as text, multimedia messages, and

ringtone downloads) and are being served by typical best-eort IP backbones.

However, best-eort is just not good enough or NGN networks, which introduce packet voice

trac, rich Service Level Agreement (SLA)-driven applications, and elevated user expectations or

service quality, as mobile broadband oers bigger pipes.

Figure 8: Common IP/MPLS Backbone

MMS

SMS/MMS

$$

Location-based

Services

Corporate

Intranet & Email

eCommerce

Gaming and

Entertainment

Data Services and

Wireline Displacement

Packet

Voice

Circuit

Voice

PSTNIP/ATM/TDM

IP/MPLS

Mobile Backbone

Other

PLMN/GRX

RVC/BSC

IuNetwork

GnNetwork

Ga

NetworkGp

ISP

Corporate

Site

Charging/

Billing OSS

GiNetwork

IP/MPLS

Convergence

GGSN

RNC/BSC SGSN

SGSN

MSC

MSC

Gateway

Voice

Gateway

Voice


13/21



As shown in the GSM / UMTS example in Figure 8, instead o operating separate networks or

specic interaces, all o these logical networks can be supported on a common converged core,

and the eature-rich IP/MPLS packet core is an obvious choice.

Supporting Trafc and Applications Mix on the Same Network

Mobile architectures are evolving to support voice and data on the same inrastructure. They

are also combining voice signaling (traditional SS7 out-o-band trac, in many cases carried on

a separate network rom bearer trac) on a converged mobile packet backbone. This mobile

backbone must support several types o trac and services:

User plane trac, such as delay-sensitive voice trac between media gateways and

packet data trac

Signaling plane trac, such as between MSC servers and Media Gateways, and other

SIGTRAN trac

Additional operations, administration, and maintenance trac such as network

congurations, bulk statistics, and sotware upgrades

A variety o new services, ranging rom best-eort, location-based IMS services to mission

critical business applications

Seamless transport o ATM (AAL2/AAL5) trac over the MPLS core, which can mean

inter-RNC trac as well as trac going rom one MSC site to another

The variety o trac and services delivery demands placed on the network mean that it must

provide highly reliable transport and powerul QoS and perormance guarantees.

Performance Expectations for Mobile Packet Backbone Networks

The ollowing table presents some rough guidelines or mobile operator perormance

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 Perormance Requirements

Meeting Mobile Packet Core Requirements

As discussed above, the NGN packet backbone must shed the best eort mentality, as it has

many new requirements to meet. This new set o requirements can be divided into the ollowingcategories:

High degree o robustness, reliability and availability

Better network resource management (guaranteed QoS, trac engineering)

Powerul operational tools

Scalability

Security

Ability to enable new applications

Future-proo investment (or example, support or evolving standards such as IMS / MMD)


14/21

14



The ollowing sections will cover these requirements in detail and discuss how Junipers mobile

packet backbone solutions address them.

Highly Reliable Networks

IP/MPLS networks have reached maturity, having now been deployed by many wireline carriersglobally. The traditional perception that IP-based networks lack ATM/TDM-like reliability has

generally been reuted. But true carrier-grade availability is still only achieved i it is supported at

the individual network element level (at each link ailure) as well as at the network level.

Juniper Networks routers support a ull MPLS eature set or highly reliable, carrier-grade IP-

MPLS networks. At each network element level, Juniper routers achieve high availability by

supporting eatures such as non-stop routing, which maintains routing during Routing Engine

(RE) switchover and provides a sel-contained mechanism that, unlike Graceul Restart, does

not require participation rom neighboring nodes. Juniper also supports RE redundancy, where

the backup routing engine oers redundancy and takes over the role o primary RE without

interrupting the orwarding o packets within the router. This is possible because Juniper

inherently supports separation o control and orwarding in the routing architecture. Additionally,

Graceul Restart is supported or OSPF, BGP, LDP, RSVP, ISIS, RIP, and other protocols. ThisInternet Engineering Task Force (IETF) standards-based solution allows recovery rom control

plane ailures in a deterministic way and without interrupting packet orwarding.

To handle link ailures between the various mobile core elements, Juniper routers use interrupt-

driven link-down notication, which can trigger locally attached systems to declare the interace

down within a ew milliseconds o ailure. Operators can move trac onto an alternative path

in one o two ways, depending on the sense o urgency in the network and the willingness to

pay an additional price or 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 o careully

engineered primary and secondary Label Switched Paths (LSPs) and the FRR capability allow

restoration targets to be achieved in only tens o milliseconds. Other Juniper eatures such as

ISSU (In Service Sotware Upgrade) are also planned. This eature will be particularly important

in mobile carrier environments where maintenance windows become dicult or impossible to

schedule. ISSU will be essential to achieving ve 9s availability. With ISSU, a complete JUNOS

package can be upgraded with minimal disruption to packet orwarding.

QoS and Trafc Management Features

Mobile networks require strict priority queuing and low latency, particularly or mobile

backbones that carry voice trac and video as well as some o the new IMS-based services.

These requirements demand a service-oriented approach to routing rather than just best-eort

orwarding.

Junipers purpose-built, ASIC-based architecture, powerul JUNOS, and trac management

eatures handle voice quality trac through low latency and strict-priority queuing. Trac

engineering urnishes critical capabilities or SLA enorcement. Constraint-based routing helpscarriers exert much greater control over how to route trac through the network. It enables

them to be very specic in selecting the most ecient pathor example, they can base their

decision on more than simple source and destination inormation and instead pinpoint precisely

which LSP trac should travel. This ensures that delay-sensitive voice, or example, wont 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 or Layer 2 and Layer 3 environments allows carriers to dene the

amount o bandwidth assigned per class o service (CoS). In essence, this enables the network to

make use o dierent bandwidth pools to ensure that there is always sucient bandwidth or the


15/21



trac that needs it the most. There is also overbooking per class, which permits extra bandwidth

to be assigned to a specic 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 doesnt exceed the allocation its received.

Juniper routers also classiy packets at the ingress port and, based on multiple elds, can

determine CoS and priority. Classication is based on the IETF Dierentiated Services (DiServ)

standard and classications are honored (or potentially changed by policy) on a per-hop basisacross the mobile backbone.

Juniper queuing and scheduling techniques oer deterministic delay and help operators meet

tight jitter perormance bounds. In tests conducted to assess the latency and jitter perormance

o Junipers M320 router (widely deployed in many mobile packet cores), high priority trac

(simulating real-time voice) o 40 byte packets was sent to an output interace loaded at 90

percent o the interace bandwidth. Best-eort trac was also sent to the same interace to

signicantly oversubscribe the interace bandwidth. The result was that no high priority packets

were dropped and the latency o 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 rom complex

troubleshooting as a major barrier to the deployment o converged services over IP/MPLS. Partly,

this concern has to do with a lack o sophisticated operations, administration, and management

(OA&M) tools in the IP/MPLS inrastructure. Juniper oers many powerul, standards-based and

easy to deploy OA&M eatures 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 deect-ree LSP

and locate deects. In addition, Juniper routers support Bidirectional Forwarding Detection (BFD)

mechanisms (Figure 9) or the detection o orwarding-plane-to-orwarding-plane connectivity.

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

BDF is essentially a liveliness mechanism to ensure that the orwarding state is intact along the

end-to-end MPLS LSP, since it is possible that even i all seems well rom the control plane point

o view, there could be an issue in the orwarding 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. I more

than a certain consecutive number o BFD packets are lost, a warning message is generated or

higher levels to take appropriate action.

TunnelMPLS Psuedowire

ATM/FR

Access

ATM/FR

Access

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


16/21

1



MPLS Auto Bandwidth

With the help o auto bandwidth support, mobile operators can automatically adjust the LSP

bandwidth based on the actual trac fowing 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 trac fow and adjusts its bandwidth every adjust-interval period. In thisprocess, the trac fow is not interrupted, as the LSP ollows the make-beore-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% o the current LSP bandwidth.

Migrating Legacy ATM Trafc to MPLS

Traditionally, many o the deployed GSM/UMTS (R99) wireless core networks have been

ATM transport networks owned by the wireless carriers. As in the wireline world, simplied

operations, greater service fexibility, 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 or migrating ATM,rame relay, and other legacy services to MPLS. In the midst o so much activity, the challenge

or mobile operators is to determine which migration strategy best suits their current customers

and applications, as well as their uture service strategies. There are three primary options rom

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/rame 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 o 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 o end-to-end

pseudowires to enable carriers to introduce MPLS seamlessly within existing ATM networks.

Pseudowires combine MPLS orwarding and IP routing to emulate ATM services and to transport

the trac while preserving ATM-like user experiences.

PSTN

Internet

Corporate

Common MPLS

Network

AAL2 ATM

3G MSC

AAL2 ATM AAL2 ATM

IP/AAL5

ATM STM-1

Radio Network

Controller

IP

lu b lu cs

Gn Gi

lu r

lu ps

RNC

RNC

HLR

USIM

Node B

AuC

SCP

GGSN

SGSN

MSC MSC

GGSN


17/21



Figure 11: Layer 2 VPN in the Mobile CoreCarrying ATM over MPLS

As illustrated in Figure 11, traditional ATM interaces 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 specications that handlecontrol plane interworking between ATM/Frame Relay and MPLS networks. Juniper, along with

our strategic partners, has been involved in developing these specications 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 Junipers 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, dierent VPNs oer easy grouping

and logical separation or various services and/or interaces. Examples or separate VPNs are

created or SIGTRAN trac, charging/billing trac (Ga), GPRS user trac between SGSN and

GGSN (Gn interace), and mobile operator internal IT and network management trac. VPNs

also enable virtual business models, where dierent branded mobile operators can use the same

basic inrastructure 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 oer new services as

business connectivity to their enterprise customers and in this way stay competitive with

wireline operators.

Security

Moving to an IP-based inrastructure does bring some additional security concerns, such as

Denial o Service (DoS) and Distributed Denial o Service (DDoS) attacks, which can potentially

interrupt thousands o voice calls and other high revenue and critical services. Juniper routingplatorms have hardware-based packet orwarding and ltering ASICs so that trac can be

controlled through line-rate lters on packets passing through the routing platorm. This provides

protocol-based rewalls that prevent DDoS and DoS attacks, alsication o source addresses, and

implement trac shaping and policing.

MPLSTunn

el

RNC SGSN

MSC

MPLS Tunnel

M

PLSTunnel

BGP or LDP

ATM VC

ATM VCATM VC

Virtual

Routing

Forwarding

VRFVRFRadio Network

Controller

Mobile Core


18/21

18



Juniper rewalls (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 rom attacks. Juniper IDP solutions use Multi-Method Detection

techniques with eight dierent detection methods, including protocol anomaly detection and

trac 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 or mobile operators, who are generally accustomed to managing circuit-switched

networks. The JUNOScope IP service manager provides a ramework that consists o tools

or managing IP services or the M- and T-Series routing platorms, providing conguration

management, inventory management, and system administration. Communication between

JUNOScope and the managed routers is based on the NETCONF specication running over

Extensible Markup Language (XML). Also, Juniper and its Operations Support System (OSS)

alliance partners support a complete set o eld-proven FCAPS (ault-management, conguration,

accounting, perormance, and security) productsor example, Redcell EMS, Net cool

perormance management systems, and others.

Juniper routers also support eatures to ease monitoring o the network. For example, port

monitoring eatures enable operators to gain visibility into trac traversing the network without

impacting line perormance. They do so by replicating the entire packet and sending it to the

ofine tool or monitoring.

As IP is being pushed urther away rom 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 ofine 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 unctionality o

Junipers products to deliver robust and fexible 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 inrastructure by providing industry-leading routing and security equipment and

by working closely with strategic partners to integrate our products into end-to-end solutions.

Junipers mobile packet backbone network solutions do more than just build an inrastructure or

the current needs o mobile operators, they also create a uture-proo inrastructure that supports

seamless migration to emerging xed mobile convergence (FMC) based on the IP Multimedia

Subsystem (IMS). Our solutions are ully 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 o the key challenges aced by

mobile operators in their migration rom circuit-switched technologiesrom the introduction

o mobile sotswitching through the deployment o IP transport and the evolution to IMS-

based FMC networks. Our mobile packet backbone solutions eature necessary openness and

scalability to enable successul carrier transition to an IP/MPLS backbone and preparation or the

evolution to IMS-FMC.


19/21



Conclusion

Regardless o whether a mobile carrier is deploying 3G or thinking o 4G, or whether they are

deploying UMTS or CDMA, they will be aced 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-classtrac engineering, reliability and scalability eatures. It must keep up with the current mobile

standards and be designed to support the planned evolution o these standards.

Juniper products deliver carrier-grade reliability, oer a smooth migration path or mobile

providers transitioning rom TDM-like inrastructures to packet-switched inrastructures, and

provide unmatched perormance and eatures in the IP inrastructure. We enable mobile

carriers to build more cost eective, fexible, and scalable networks, leveraging a common IP

inrastructure that increases protability in the ollowing ways:

By allowing new higher-margin services to be introduced more economically, rapidly, and

fexibly than beore

By reducing operating expenses associated with managing multiple networks that each

depend on dierent technologies

By leveraging existing carrier investments to create bundled services

By maintaining a single Authentication, Authorization, and Accounting (AAA) system or

all users, regardless o which network resources they use

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

networks.

References and Further Reading

Introducing MPLS Layer 3 VPNs in Mobile Operator Networks

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

The Use o Virtual Trunks or ATM/MPLS Control Plane Interworking Specication,

by Peter Busschbach and Nikhil Shah

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

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

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


20/21

20



Complete List of Acronyms and Terms

3GPP: 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 or 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 or Mobile communications

GTP: GPRS Tunneling Protocol

HLR: Home Location Register

Stores subscriber data relating to services and eatures in addition to location area

inormation.

HSS: Home Subscriber Server

Master database or the PLMN, made up o several physical databases depending on the

number o subscribers and the supported services. Holds variables and identities or thesupport, establishment and maintenance o 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

SotSwitch element that provides a gateway to support both bearer and signaling trac.

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 unctionality.

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


21/21


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 or Advanced Networks

(Standards Body)

Formed rom the previous ETSI working groups o TIPHON and SPAN.

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

UMTS: Universal Mobile Telecommunications System

VRF: Virtual routing orwarding

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 certication encompasses numerous dierent 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 or Microwave Access

Another name or the 802.16 wireless networking specication used or long-haul and backhaul

connections.

WLAN: Wireless LAN

About Juniper Networks

Juniper Networks develops purpose-built, high-perormance IP platorms that enable customers

to support a wide variety o services and applications at scale. Service providers, enterprises,

governments and research and education institutions rely on Juniper to deliver a portolio o

proven networking, security and application acceleration solutions that solve highly complex,

ast-changing problems in the worlds most demanding networks. Additional inormation can be

ound at www.juniper.net. For comments or questions, please email mobile-convergence-team@

jnpr.net.

Copyright 2007, Juniper Networks, Inc. All rights reserved. Juniper Networks and the Juniper Networks logo are registered trademarks o 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 o

Juniper Networks or their respective owners. All specications are subject to change without notice. Juniper Networks assumes no responsibility or any inaccuracies

in this document or or any obligation to update inormation in this document. Juniper Networks reserves the right to change, modiy, transer, or otherwise revise this

publication without notice.

pcn juniper networks14

Documents