Juniper Mobile Backhaul

REFERENCE ARCHITECTURE

Copyright © 2009, Juniper Networks, Inc.

Mobile backhaul RefeRence aRchitectuRe

2 Copyright © 2009, Juniper Networks, Inc.

RefeRence aRchitectuRe - Mobile backhaul Reference architecture

Table of Contentsintroduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

framework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

High-Level Overview of Mobile Technologies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Solution Profile overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

What Constitutes a Mobile Radio Access Network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

BTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

BSC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Mobile Core: PDSN/GGSN/SGSN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

What is a Mobile Backhaul. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

What are the Available Types of Backhaul . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Flat IP Network Architectures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Requirements from an IP Backhaul Network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

CoS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Transport and Services. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Synchronization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Reliability and Fault Detection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Network Configuration and Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Key Performance Indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Legacy Backhaul Networks to Carrier Ethernet Migration Strategy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Scenario B: BS Supports Ethernet in Addition to Legacy Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Solution Profile overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Reference Solution Architecture Types. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Solution A: Umbrella Solution—Migration Strategy from 2/2.5 and 3G Legacy Networks + Greenfield 3G/4G Deployments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Solution B: 3G/4G Backhaul Greenfield Deployment Subset. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Solution-Required Devices. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Design considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

VLAN Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

CoS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

MPLS LSPs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Timing Synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Failure Recovery and Reliability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Solution-type Profiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Solution A: Umbrella Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Solution B: Greenfield Deployment Subset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Routing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

CoS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

VPN Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Copyright © 2009, Juniper Networks, Inc. 3


Table of Figuresfigure 1: overview of a mobile backhaul network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

figure 2: 3GPP2 technology family . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

figure 3: 3GPP technology family . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

figure 4: overview of a generic mobile backhaul . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

figure 5: Subcomponents of mobile backhaul network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

figure 6: atM backhaul . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

figure 7: iP/ethernet backhaul . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

figure 8: Services to be transported over carrier ethernet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

figure 9: components of iP Ran transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

figure 10: iP Ran QoS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

figure 11: MPlS-based transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

figure 12: Migrating to carrier ethernet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

figure 13: co-existence of legacy technologies and ethernet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

figure 14: legacy technologies carried over ethernet network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

figure 15: Dual support for ethernet and legacy technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

figure 16: all iP-/ethernet-based backhaul . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

figure 17: high-level overview of solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

figure 18: Simplified view of mobile backhaul network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

figure 19: tDM-pseudowire-based technology migration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

figure 20: tDM and ethernet coexistence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

figure 21: iP-/ethernet-based mobile backhaul . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

figure 22: aggregation device internal to bGP domain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

figure 23: aggregation device external to bGP domain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

figure 24: example—bX7000 specific design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

figure 25: Mobile backhaul test network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

figure 26: logical view of mobile backhaul network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

figure 27: Vlan tags at cell site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

figure 28: layer 2-based coS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

figure 29: layer 3 VPn-based coS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

figure 30: VPlS view of mobile backhaul network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

figure 31: l3VPn view of mobile backhaul network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

figure 32: J Series as an access device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

figure 33: ctP Series as an access device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

appendixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Examples of Deployment Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

J Series as an Access Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

CTP Series as an Access Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

about Juniper networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38



IntroductionMobile backhaul networks have been gaining a lot of attention lately. There have been advancements in cellular technologies and the proliferation of consumer mobile devices such as smartphones and laptops capable of mobile broadband access. The newer cellular technologies have resulted in significant increases in connection speeds over the air both on the uplink and downlink—that is, to and from the user device. Needless to state, there have been a lot of improvements on the wired core network side. However, today, mobile backhaul networks that connect the access or RF side to the core of the mobile network have to catch up with all these changes and thus tend to counterbalance the enhancements on the rest of the network.

At present, a large number of the existing backhaul networks are hierarchical and based on legacy technologies that are incapable of supporting higher speeds or service requirements. Most of these networks are based on traditional T1 circuit switching and used to transmit voice traffic. The introduction of the Apple iPhone in 2007 heralded the first tolerable use of the Internet on a mobile handheld device. The subsequent smart mobile devices and unlimited data/voice services have led to the development of technologies supporting higher bandwidth and faster download rates. This has fueled the demand for higher backhaul network capacity and intelligence. Another important factor to bear in mind is that the cost of a T1-/E1-based backhaul increases with the bandwidth. Hence, there is a critical requirement to migrate the mobile backhaul network to technologies that can support quality of service (QoS) to separate traffic streams, timing synchronization, lower packet loss, and high availability (HA).

The key drivers behind the demand for a new or reengineered mobile backhaul include:

Increase in data traffic and number of subscribers•

Dynamically changing usage patterns•

Variation in type of traffic transported across the network•

Requirement for QoS-based prioritization of traffic•

Timing synchronization•

Juniper Networks® offers mobile backhaul solutions that can be either purely IP/Ethernet-MPLS based or a hybrid of Ethernet and other Layer 2 technologies such as ATM/T1-E1/Frame Relay. Juniper Networks products are suited for a wide range of mobile backhaul solutions that span migration strategies from legacy technologies to greenfield deployments that meet the requirements of the latest technologies.

The primary focus of this document is on mobile backhaul architecture based on an Ethernet/MPLS solution1. This solution aims to describe the following concepts:

There can be multiple migration paths from the existing legacy technology-based backhaul networks. Some •of these options can provide a migration strategy that fits with the long-term plan to move to the latest technologies such as LTE.

The functionality of the mobile backhaul network is independent and not influenced by the type of traffic that is •transported across the network.

Services such as class of service (CoS), MPLS, and VPLS—coupled with features such as HA, OAM, and •Reliability—can be leveraged for mobile traffic.

Mobile network operators that are already familiar with Juniper Networks JUNOS• ® Software can implement all the IP and Carrier Ethernet2 features with considerable ease.

Figure 1 illustrates a mobile backhaul network that serves multiple generations of mobile technologies. There can be a device acting as the access gateway from the cell sites—the access type is dependent on the mobile technology generation. Thus the access gateway can service legacy TDM/ATM or IP/Ethernet technologies. Cell sites based on newer technologies can directly participate in the IP/Ethernet network. A variety of VPN services and CoS offerings are available on the Metro Ethernet network. MPLS serves as the transport mechanism for the data belonging to all these services. An aggregation device links the backhaul network to the network controller that interfaces with the mobile core. All the devices in the mobile backhaul need to be managed, provisioned, and monitored at node, service, transport, and network levels.

1The Ethernet/MPLS solution references both the MEF22 (Mobile Backhaul Implementation Agreement) and the IP/MPLS Forum 20.0.0 standard. 2 When referring to Carrier Ethernet, this paper does not include transport services such as PBB, PBT, and connection-oriented Ethernet.



figure 1: overview of a mobile backhaul network

Highlights of the mobile backhaul solution discussed here include:

A main or unified scenario that offers migration strategies from legacy technologies such as TDM and ATM, IP-/•Ethernet-based design for greenfield and newer technologies such as WiMAX/LTE backhaul—This solution can be split into subsets based on the implementation applicability. One of the subsets that is described in addition to the umbrella solution is the greenfield deployment that is based on IP/Carrier Ethernet.

Flexibility of using a combined Layer 2- and Layer 3-based network—The requirement to use a Layer 2- or Layer •3-based network that can offer services is dependent on the level of operator familiarity, existing infrastructure, and applications.

Aggregation performed closer to the BTS—Aggregation and Metro network functionality is pushed closer to •the access.

VPN-based services across metro ring (E-Line• 3 and emulated LAN [ELAN]4 services)—These VPNs can offer either unicast or multicast services at Layer 2 or Layer 3 level.

Use of MPLS LSPs as transport mechanism in the metro ring.•

User traffic prioritization and CoS.•

ScopeThis document is intended to be a reference guide to those involved in planning and designing mobile backhaul networks.The mobile backhaul scenarios described here are based on products such as Juniper Networks BX7000 Multi-Access Gateway, EX Series Ethernet Switches, M Series Multiservice Edge Routers, and MX Series Ethernet Services Routers. RSVP-based MPLS is used as the transport mechanism for L3VPN and BGP-VPLS services within the Metro ring network.

4G SAE GW

WirelineMSC

MetroNetwork

PE Router/P Device

IP/EthernetATM/TDM

Metro NetworkPE Router/

P Device and/orAggregation Device

ATM/TDMCapable

IP/EthernetCapable

Network Provisioning/Monitoring Fault Detection

Ethernet Backhaul Network(L2/L3), IP/MPLS (with PWE) +VPN Services (L2VPN/L3VPN/

VPLS/NG-MVPN) + CoS 3G RNC

2G BSC

Wireline

Access GatewayDevices2G-GSM/CDMA

3G-UMTS/CDMA/

EVDO/EDGE

4G-LTE/WiMax

3E-Line is an MEF definition for different types of VPN connectivity. Please refer to the MEF standards for more details. 4ELAN is an MEF definition for different types of VPN connectivity. Please refer to the MEF standards for more details.



FrameworkPrior to launching into the discussion on the suggested backhaul scenarios, it is important to get familiar with the terms and concepts of mobile networks, available backhaul network options, and requirements of a next-generation backhaul network at a high level. This section helps provide such an understanding. The solution details are discussed later in the document.

High-Level Overview of Mobile TechnologiesMobile technologies are classified into different generations referred to as 2G/2.5G/3G/4G. Each generation of mobile technologies provides users with enhanced services, higher speeds, and better network capacity. Different bodies and forums such as 3GPP/3GPP2/ETSI/ITU recommend, approve standards, and advance the various technologies under each generation. Figure 1 and Figure 2 provides a brief summary of the different technology streams under each generation.

Solution Profile Overview

figure 2: 3GPP2 technology family

figure 3: 3GPP technology family

What Constitutes a Mobile Radio Access NetworkThe main components of a Radio Access Network (RAN) are described briefly in the following sections. The terminology used for these components differs based on the technology that is used. Table 1 lists the different naming conventions used in the case of each technology.

3GPP2

2G – CDMAOne

3G – CDMA2000 EVDO

3GPP

2G – GSM

3G – UMTS

4G – LTE

W-CDMA

HSPA

GPRS

EDGE

TD-CDMA/TD-SCDMA

3GPP Rel8

E-UTRAN



BTS A BTS is a device that can provide communication between mobile user equipment and a mobile network. The BTS communicates with the mobile user devices over the air interface. There can typically be as many as 50 BTS devices controlled by one BSC. (This document uses the generic term BS or RAN BS to refer to a cell tower/BTS.)

BSC The main function of a BSC is to communicate and control multiple BTS devices over either the Abis or Iub interface. The BSC also controls handoffs that occur as a result of mobile devices moving between cell sites and communicates with the mobile core (The type of communication depends on interface to core that in turn depends on technology). A single 2G BSC can typically control as many as 50 BTS devices while a 3G RNC can control 200 NodeBs and up to 800 base stations per BSC/RNC in a 2.5G/3G network. (This document uses the generic term RNC or RAN NC to refer to a BSC.)

Mobile Core: PDSN/GGSN/SGSNThe mobile core network can consist of a PDSN or GGSN/SGSN that acts as a gateway to the external packet data network.

Table 1: RAN Components for Different Mobile Technologies

MOBILE TECHNOLOGY GENERATION

TYPE OF TECHNOLOGY

RAN COMPONENTS

EXAMPLE OF ROLE

Generation

2G GSM BTS

BSC

MSC

•CommunicationbetweenairinterfaceandBSC

•ControlsmultipleBS

•HandlesvoicecallsandSMS

2 .5G GPRS BTS

SGSN

GGSN

BSC + PCU

•CommunicationbetweenairinterfaceandBSC

•Mobilitymanagement,datadeliverytoandfrom mobile user devices

•Gatewaytoexternaldatanetwork

•ControlsmultipleBSandprocessesdatapackets

3G EVDO BTS

RNC

PDSN

•CommunicationbetweenairinterfaceandRNC

•Callprocessingandhandoffs, communication with PDSN

•Gatewaytoexternalnetwork

UTRAN NodeB

RNC

MSC

•PerformsfunctionssimilartoBTS

•PerformsfunctionssimilartoBSC

•HandlesvoicecallsandSMS

4G LTE eNodeB

SGW (Serving Gateway)

MME (Mobility Management Entity)

PDN Gateway

•PerformsfunctionssimilartoBTSandradioresource management

•Routingandforwardingofuserdata,mobilityanchoring

•Trackingidleuserdevices,handoffmanagement

•Gatewaytoexternaldatanetwork

WiMAX BS

ASN GW

CSN GW

•DHCP,QoSpolicyenforcement,trafficclassification

•Layer2trafficaggregationpointASN

•ConnectivitytotheInternet,externalpublicor private networks



What is a Mobile BackhaulIn a nutshell, the backhaul can be considered to be the portion of the network that connects the BS (and air interface) to the BSCs and mobile core network. The backhaul can consist of a group of cell sites that are aggregated at a series of hub sites. (A cell site or cell tower consists of antennas, transmitting and receiving equipment mounted on a tower.) Figure 4 gives a high-level representation of the mobile backhaul. The cell site may either consist of a single BS that is connected to the aggregation device or a collection of BSs that are aggregated.

figure 4: overview of a generic mobile backhaul

The generic model for the newer backhaul networks consists of a cell, hub sites, or both connected to aggregation devices that in turn can either belong or be connected to a Metro network. Figure 5 shows the different subcomponents of the mobile backhaul network. The most commonly proposed metro network for 3G/4G technologies is an Ethernet-based services network. This network should be capable of providing multiaccess to different Layer 2 technologies such as FR/ATM/TDM and IP.

Another perspective of the mobile backhaul could lead to following classification of functionality:

Multiaccess gateway—This can consist of devices that can support •TDM/ATM or Ethernet connectivity at the cell/hub sites.

Transport—The data from the different cell sites is carried over •pseudowires that support circuit emulation.

Timing Synchronization—Clocking for the TDM data needs to be •synchronized across the network.

Aggregation—An aggregation device performs aggregation of all the •incoming connections before they reach the mobile core.

The functionality and requirements of a mobile backhaul network are discussed in later sections.

What are the Available Types of BackhaulThe connectivity type offered by the backhaul network is influenced by the technology used in the RAN and factors such as geographical location of the cell site, bandwidth requirements, and local regulations. For instance, remote cell sites that cannot be connected via physical links instead use a microwave backhaul to connect to the BSC and mobile core network. The amount of available frequency spectrum and spectral efficiency of the air interface influence the bandwidth requirements of a cell site. Hence, the backhaul network can consist of either one or a combination of different physical media and transport mechanisms. Selecting between the different options available depends upon the type of radio technology, applications that are expected to be used, and transport mechanism. Table 2 lists the different technologies and the corresponding base station support.

Table 2: Mobile Technologies and Base Station Support

Generation Technology Base Station Interface

Base Station Support

Backhaul Network Support

2/2 .5G GPRS/TDMA/CDMA Abis Channelized TDM PDH/SDH

3G (Rel99) UMTS Iub ATM ATM

3G/4G EVDO, UMTS (Rel5), WiMAX , LTE

Iub/Abis Ethernet/IP IP/MPLS/Ethernet

Mobile Backhaul

BSCBS

Mobile Backhaul

Cell Site Devices

Hub/AggregationSite Devices

Metro Network

figure 5: Subcomponents of mobile backhaul network



2/2.5G technologies were designed for voice services, which are ideal for that purpose, but not efficient for data and video services. As of now, 8 to 12 T1s service a cell site (BTS). The requirement for T1s is directly proportional to the cost. Added to that, scalability is an issue due to the lack of support for reuse of bandwidth and bundling of links.

RANs belonging to the 3G technology family aim to solve this problem by using either ATM or IP between the BTS and BSC instead of TDM. This approach—combined with other enhancements on the air interface and between RNCs—provides better scalability since it allows bandwidth reuse.

ATM is used in case of a UMTS Rel99-based 3G network while EVDO, UMTS (3GPP Rel5) and WiMAX use IP. LTE uses completely IP-based RAN architecture. When using ATM (3GPP Rel99), T1/E1 or T3/E3/OC3 links can be used for low and high population density areas, respectively. AAL5 and AAL2 PDUs are carried at Layer 2. Figure 6 shows an ATM backhaul network.

figure 6: atM backhaul

3GPP Rel5 uses IP as the transport bearer. The IP packets, in cases of higher density cell sites, are carried over Ethernet—and MLPPP links are used for lower density sites. (MLPPP is used with T1/E1 links.) Figure 7 shows an IP/Ethernet-based backhaul.

figure 7: iP/ethernet backhaul

Flat IP Network Architectures The move to using IP in the backhaul is driven by the requirements imposed by 3G/4G technologies. The term flat IP architecture can be applied to a network where all the nodes can reach each other via IP connectivity. A flat IP architecture can be applied to a network where the radio and routing functionality is pushed to the edge of the network. The end-to-end connectivity is achieved through a packet-based core network. Technologies such as LTE are based on a flat IP architecture.

note: The term “Packet core” is used in conjunction with technologies such as EVDO and GPRS. In this case, a tunnel needs to be created to carry and process native IP packets. In contrast, an IP core refers to an Internet-based model that can support native IP.

One of the main advantages of using IP-based networks is the capability to transport different traffic types over a common IP-/MPLS-based infrastructure in addition to providing QoS guarantees and security requirements. For example, circuit- based voice, and 2G- or 3G-based voice and data can all be carried over a common IP/MPLS network. The main objectives driving the usage of IP-based architecture are the following:

Requirement for lower latency (serialization of data on a TDM network adds to latency delay.)•

Requirement for lower cost•

Reducing the total volume of equipment that is used (This objective can be achieved when equipment has •integrated capability of BTS, RNC, Mobile core, or all three.)

ATM Backhaul

ATM-IMA

AAL5 AAL2

lub lub

BSC

EthernetBackhaul

IP/UDP over Ethernet

lub lub

BSC



Requirements from an IP Backhaul NetworkAs expected, transport forms the crux of the RAN—it needs to be able to scale in terms of capacity and demands of higher bandwidth, be reliable and efficient. Hence, the selection of the most suitable type of backhaul network needs to be made with the understanding of the end-to-end requirements of the mobile network.

A solution that combines IP in the RAN with Carrier Ethernet in the metro aggregation network has the advantage of being cost effective, easy to use and manage; supporting various services; and maintaining performance requirements. The IP/Carrier Ethernet solution offers reliability, HA, and CoS in the backhaul space. Carrier Ethernet has the advantage of being a tried and tested carrier-class technology that is reliable. It is flexible enough to provide underlying infrastructure to higher level services and applications. Carrier Ethernet can thus be leveraged to bring the IP and MPLS capabilities available on the core side to the backhaul network. Figure 8 shows the different services that can be transported over Carrier Ethernet.

figure 8: Services to be transported over carrier ethernet

Figure 9 shows the key components that need to be transported over an IP-based RAN. All the devices in the RAN need to be manageable either through in-band or out-of-band management. Network timing synchronization is required when transporting technologies such as TDM over the IP network. RAN signaling messages need to be carried with proper encapsulation applied to the IP packets. QoS needs to be applied on the user (and RAN signaling) traffic.

figure 9: components of iP Ran transport

Detailed requirements of an IP-/Ethernet-based mobile backhaul network are discussed in detail in the following sections.

CoSServices are offered on the mobile network end to end between the user mobile devices. The mobile network, including the backhaul, serves as a bearer infrastructure for these services. Each service can be assigned to a particular traffic class and prioritized. In general, services signaling, user plane transport, and management traffic can be classified, prioritized, and scheduled using CoS. The mobile backhaul network needs to be capable of recognizing the CoS settings, doing any re-marking of packets if required, prioritizing between the packets, and applying CoS rules to the different traffic streams. Figure 10 shows the different types of CoS marking that can be done to differentiate between the traffic streams.

figure 10: iP Ran QoS

IP Routing

MPLS

PWE

L2/L3 VPNCarr

ier

Ethe

rnet

IP Transport over RAN

Management TimingSynchronization Signaling User Generated

Traffic

IP RAN QoS Scenarios

VLAN Servicebased (Layer 2) 802.1p (Layer 2) DSCP (IP) EXP (MPLS)



Backhaul networks need to be able to support the main traffic types—voice, video, network signaling/management, and best-effort data. The network should also be able to provide low packet loss. For this, CoS definitions need to be determined and maintained at each node in the backhaul such that the different traffic types can be prioritized through the network accordingly.

The mobile technology standards define classes that can be used for the traffic classification but do not mandate how many of these classes are actually to be used. This number will depend on the network implementation and traffic profile. In general, differentiation between the traffic types is done by marking and prioritizing packets as “High,” “Medium,” or “Low.” The prioritization depends on the traffic type.

There are four classes of traffic defined in case of the 3GPP-based technologies such as UMTS. These traffic classes can be shared between the wired and mobile traffic streams and are all prioritized based on their CoS marking. The different classes may either be spilt or aggregated at each node in the backhaul or core network. Each hop in the network can classify the packet based on 802.1p or DSCP or EXP classifiers. Additional levels of granularity can be added by prioritizing different traffic streams within a traffic class. The level of granularity will depend on the type of CoS guarantees, network spanning multiple domains, complexity of implementation, and the capability of the network interfaces and equipment.

Table 3 provides a summary of the different traffic classes defined in the mobile backhaul solution test network and the corresponding DSCP/802.1p/EXP marking.

Table 3: CoS Mapping

CoS TRAFFIC CLASS

CoS SERVICE CLASS DIFFSERV TRAFFIC CLASS (WIRED-/ PACKET-SWITCHED NETWORK)

TYPICAL APPLICATIONS

background Low (non-real-time traffic)

Best Effort (BE) Wired/Mobile IP data/email

interactive Low (non-real-time traffic)

Assured Forwarding (AF12)

TCP-based services—HTTP/Telnet

Streaming Medium (real-time traffic)

Assured Forwarding (AF11)

UDP/RTP—Streaming video

conversational High(real-timetraffic) Expedited Forwarding (EF)

Voice—VoIP/Video conferencing

Bidirectional traffic such as VoIP and video conferencing that require low latency is assigned to the Conversational class. Unidirectional traffic such as streaming video (UDP/RTP streams) is classified into the Streaming class. The Interactive class can be used for applications that use TCP-based transactions such as HTTP and Telnet. The Background traffic class can contain a combination of both low-priority traffic from mobile or wired applications and background data from mobile applications. The traffic streams will carry different CoS markings based on their origins.

Transport and ServicesMPLS and pseudowires are used as the transport mechanism in both the IP/Ethernet and hybrid types of mobile backhaul networks. The pseudowires themselves can be transported over the MPLS LSPs. The advantage of using MPLS for transporting pseudowires is that it is agnostic to the transport media and more scalable than pure Layer 2 networks. While Layer 2 networks are cheaper and easier to implement, on the other hand, they are neither scalable nor easily manageable. For example, one major issue with pure Layer 2 networks is the scalability with respect to the number of MAC addresses that can be learned and stored. Also, Layer 2 communication is based on the forwarding table information that cannot be entirely controlled under circumstances such as duplicate MAC address learning that results in loops and flooding. A Layer 3 network can solve such an issue since the routing information is obtained from the control plane, thus making it more deterministic.

Layer 3 networks offer reliability, convergence of services (2G/3G traffic), QoS, OAM, inherent security (when using VPNs), and synchronization. MPLS (and pseudowires) can support transport of multiple technologies such as ATM, TDM, and Ethernet over the same physical links. MPLS protection schemes ensure faster convergence and failure detection times



Implementing MPLS in conjunction with VPN services in the metro provides mobile network carriers with new revenue opportunities. The VPN services could be either Layer 2 (L2VPN/VPLS) or Layer 3 (L3VPN/MVPN) based. The traffic belonging to different VPNs can be transported over pseudowire (and thus over MPLS LSPs). Figure 11 shows two nodes, PE1 and PE2, which are a part of the Metro network. The provider edge (PE) routers are configured to offer two VPN services (VPN-A and VPN-B).

Traffic belonging to each of these VPNs is carried over a separate set of pseudowires. There can be several such sets of pseudowires carried within an MPLS LSP tunnel.

The connectivity offered by the MPLS LSPs to the VPN service can either be point-to-point, point-to-multipoint, or multipoint-to-multipoint. Based on the MEF definitions, the services offered would be either E-Line/Ethernet Virtual Private Line; ELAN/Ethernet Virtual Private LAN, or E-Tree. Typically, E-Line connectivity delivers unicast traffic while ELAN can be used either for unicast or multicast traffic. Mapping connectivity to services results in typically L2/L3VPNs using E-line connectivity while VPLS/MVPN use the ELAN or E-Tree connectivity based on the topology and requirements.

The CoS requirements of the traffic streams being transported across the MPLS LSP can be achieved using the EXP classifiers. Granular prioritization of streams belonging to different VPN services can also be done using a combination of behavior aggregate (BA) and multifield (MF) classifiers.

figure 11: MPlS-based transport

SynchronizationThe continuity of a circuit clock is lost when the circuit is transported over an IP- or packet-based network. The fundamental difference between the two is that the circuit is synchronous while the IP network is asynchronous. Clock synchronization in a mobile backhaul network is an essential requirement for handoff support, voice quality, and low interference. Loss of timing synchronization can result in poor user experience, service disruptions, and wastage of frequency spectrum. Hence, timing in a mobile network can be distributed by one of the following methods to maintain the clock synchronization:

Using GPS or a legacy TDM network that is external to the IP-packet based network•

Packet-based dedicated streams (IEEE1588- or NTP-based ) •

Using Synchronous Ethernet over the physical layer •

Adaptive clocking•

DSL clocking•

The accuracy for timing delivered at the BS should be at least 50 ppb according to G.8261.

Reliability and Fault DetectionFault detection mechanisms need to be in place at different levels of the network. For example, OAM can be used to detect failures at both Ethernet physical and link layers. Various MPLS protection schemes offer options such as make-before-break, and link- and node-level failure detection while protocols such as Bidirectional Forwarding Detection (BFD) enable better route convergence times. All these schemes enable faster detection, notification, and recovery from failures—thus increasing the reliability of the network.

Network Configuration and MonitoringIt is essential to use software tools that provide ease of network provisioning, management, and monitoring. The tools need to be able to maintain a database of the network node information in order to support configuration and monitoring. There may not be a single software tool that performs all the functions. In such a case, provisioning and monitoring can be split between a combination of different tools that are capable of providing essential chassis, node, routing, transport, and services related to configuration and statistics.

PE-1VPN-A

VPN-BPE-2MPLS Transport Tunnel

Pseudowire



Key Performance IndicatorsThe following is a list of metrics that can be used to quantify the performance of the mobile backhaul network:

Per CoS traffic class.•

Delay—Both Maximum and Average delay need to be measured. When performing TDM circuit emulation, delay, •latency, and bandwidth efficiency impact each other significantly.

Jitter—Jitter plays a major role when doing TDM circuit emulation. The jitter introduced in the network will •depend upon the jitter buffer.

Packet Loss—The rate of packet loss depends on the service that is supported and the underlying technology •that is used.

Latency, Availability—The availability of the network has to compare to the requirements from a carrier. •

Legacy Backhaul Networks to Carrier Ethernet Migration StrategyThis section describes two main scenarios when migrating from existing legacy networks to Carrier Ethernet. The type of scenario encountered mainly depends upon the extent of Ethernet support available on the BS. Irrespective of the level of Ethernet support, the migration path involves an intermediate step of a TDM/ATM/Packet hybrid backhaul. This is shown in Figure 12. The hybrid nature of the backhaul will depend upon either using an interworking function between the BS and BSC or running a dual TDM/Ethernet stack on the BS and BSC.

figure 12: Migrating to carrier ethernet

The two main scenarios include:

Scenario a: bS with no ethernet Support

In this scenario, both the BS and RAN NC in the mobile core do not have native Ethernet interface support and so cannot be directly connected to the Carrier Ethernet network. An interworking capability is required to be able to connect the TDM/ATM interfaces on the BS and NC to the Ethernet network. This scenario mainly pertains to the migration step where both legacy and Ethernet technologies need to be supported.

option 1: Run iP/carrier ethernet in Parallel to tDM/atM backhaul•

In this scenario, low-priority high-bandwidth traffic can be offloaded from the legacy TDM/ATM network to the Carrier Ethernet IP network for scalability purposes. For example, the IP packet portion of the network can be used for data transport while 2G/3G voice traffic can be sent over the TDM portion of the backhaul. In this case, an interworking function between the legacy technology on the BS, such as TDM/ATM, and the Carrier Ethernet is required in the RAN. Figure 13 shows the BS and RAN NC connected to the Ethernet backhaul that includes an interworking functionality.

Step 1 – TDM/ATM Legacy Backhaul

Step 2 – Packet + ATM Hybrid Backhaul

Step 3 – Packet Carrier Ethernet Backhaul



figure 13: co-existence of legacy technologies and ethernet

option 2: emulate native Service over ethernet using PWe•

This option requires the use of an interworking function but all the traffic between the BS and RAN NC is carried over the Carrier Ethernet network. (Here, Ethernet replaces the legacy technology.) The native TDM/ATM service can be carried over Ethernet using pseudowires for circuit emulation. Figure 14 shows a logical representation of the TDM/ATM traffic and Ethernet traffic being carried over the Ethernet backhaul.

figure 14: legacy technologies carried over ethernet network

Scenario B: BS Supports Ethernet in Addition to Legacy TechnologyIn this scenario, the BS and Ran NC are capable of supporting both Ethernet and the legacy technology. This leads to the options of either using the legacy network in conjunction with Ethernet or just the latter.

option 3: using both Packet/ethernet and legacy technologies•

In this case, the RAN nodes are equipped with dual stacks to support TDM/ATM and packet traffic. The legacy technology is use alongside with the Ethernet network. Figure 15 illustrates this option. Low-priority high-bandwidth traffic can be offloaded from the legacy TDM/ATM network to the Carrier Ethernet network for scalability purposes.

Mobile CoreNetwork

RAN NCRAN BS

Backhaul NetworkEthernet + IP/MPLS +

Services

Interworking –TDM/ATM - Ethernet

TDM/ATM

Ethernet


TDM/ATM

Ethernet

Mobile CoreNetwork

RAN NCRAN BS


Services

Legacy BackhaulNetwork – TDM/ATM



TDM/ATM TDM/ATM



figure 15: Dual support for ethernet and legacy technology

option 4: use Packet/ethernet all through backhaul•

In this case, the BS and RAN NC can support Ethernet and are directly connected to the Carrier Ethernet network. All traffic is carried over the Ethernet network. Figure 16 shows this option.

figure 16: all iP-/ethernet-based backhaul

Solution Profile OverviewAs discussed in the earlier sections, it is imperative for mobile backhaul networks to be able to support the requirements for growing bandwidth, scalability, and classification or prioritization of services. IP-/Carrier Ethernet-based mobile networks support all these requirements and are hence ideally suited for use in mobile backhaul networks. Greenfield and upcoming 3G-/4G-based networks can use IP/Carrier Ethernet as the backhaul without any migration issues. However, existing 2/2.5 and some of the 3G networks need to migrate to IP/Carrier Ethernet while still continuing to support legacy technologies such as TDM/ATM.

Juniper products can be used in either of these scenarios to provide a scalable, reliable backhaul network that is capable of offering VPN services, CoS, and MPLS-based transport. This document describes a main umbrella solution that can be used either for migration from legacy technologies or for newer deployments. It addresses the issue of migration, coexistence of legacy technologies such as TDM with an IP/Ethernet backhaul, and addresses new deployments. A subset of this umbrella solution that focuses on greenfield deployments based on newer 3G/4G technologies is also explained in detail.

Reference Solution Architecture TypesThere are two aspects to the main mobile backhaul architecture discussed in this document. The first is a pseudowire-based aspect that can be used to implement a hybrid of a legacy and IP/Ethernet backhaul network. The second is a pure Carrier Ethernet-based aspect using IP/MPLS, L3VPN, and VPLS. Both these aspects are explained to illustrate the design and planning of migration strategies and greenfield deployments.

Mobile CoreNetwork

RAN NCSupports Legacy andEthenet Technology

RAN BSSupports Legacy and

Ethernet Technologies


Services

Legacy BackhaulNetwork – TDM/ATM

TDM/ATM TDM/ATM

Ethernet Ethernet

Mobile CoreNetwork

RAN NCRAN BS


VPNs

Ethernet Ethernet



Solution A: Umbrella Solution—Migration Strategy from 2/2.5 and 3G Legacy Networks + Greenfield 3G/4G DeploymentsThis solution addresses the following requirements:

Migration and coexistence of TDM and Ethernet in the backhaul by using pseudowires and circuit emulation•

Purely IP/Ethernet-based greenfield deployment that can deliver CoS, MPLS transport, and VPN services •

The first requirement is described under Solution A while details on the second can be found under Solution B.

As listed in Table 5, the BX7000 can serve as a multi-access gateway in combination with the M Series routers (with circuit emulation PICs) in a hybrid environment. Such a hybrid scenario involves either migration or coexistence between IP/Ethernet and legacy technologies. In case of the pure IP/Ethernet scenarios, the BX7000, Juniper Networks J Series Services Routers, or EX Series can act as the cell or hub site devices. In all the possible scenarios, MX Series or M Series routers can be used in the Metro network that supports services such as VPNs, CoS, and IP/MPLS. Juniper Networks JUNOScope Software can be used to manage the different network elements.

Figure 17 shows a high-level overview of the mobile backhaul network solution.

figure 17: high-level overview of solution

Figure 18 shows a simplified view of the backhaul solution with the BX7000 and EX Series acting as the cell site devices. The connections from these devices to the Metro network can be either Layer 2 or Layer 3 based. The BX7000 sets up a pseudowire across the Metro network to the M Series router (M120-PE) that has the circuit emulation PICs. CoS can be applied across all the nodes including the EX Series in the 3G/4G scenario. As mentioned earlier, the Metro network offers transport and services in all scenarios.

4G SAE GW

MX Series M Series

BX Series

IP/Ethernet

TDM/ATM

J Series

EX Series

IP/EthernetATM/TDM

Ethernet BackhaulNetwork (L2/L3)

IP/MPLS (with PWE) +VPN Services (L2VPN/L3VPN/

VPLS/NG-MVPN) + CoS

JUNOScope + IBM ITNM

NetworksProvisioning/Monitoring Fault Detection

3G RNC

2G BSC

2G-GSM/CDMA

3G-UMTS/EDGE CDMA/

EVDO

4G-LTE/WiMax

Psuedowire over MPLS LSP



figure 18: Simplified view of mobile backhaul network

For better understanding, the umbrella solution has been described based on the migration, coexistence, and greenfield deployment aspects:

tDM-Pseudowire-based technology Migration•

Figure 19 shows a TDM-Ethernet-based backhaul network. Here, the BS and RAN NC are only capable of supporting TDM. A BX7000 is used as the cell/hub site device and has incoming T1/DS3/SDH links. It is connected to an IP/Ethernet-based metro network that can deliver CoS, VPN services, and MPLS transport. The TDM traffic is carried over the metro network using circuit emulation over pseudowires. As described earlier, pseudowires involve the use of MPLS LSPs across the metro network. The pseudowires terminate on an M Series router that acts as an aggregation device and consists of circuit emulation PICs (4-port channelized STM1/OC3 or 12-port T1/E1) that achieve the translation from Ethernet to TDM. The RAN NC (BSC) then receives the TDM stream from the M Series router. The Metro network can consist of a combination of M Series routers, MX series routers, or both.

figure 19: tDM-pseudowire-based technology migration

Mobile CoreNetwork

RAN NCRAN BS

Ethernet MetroNetwork

Ethernet TDMTDM

AggregationDevicePseudowire – TDM Emulation

IP/MPLS LSP

Cell HubSite Device

2G

CELL SITE DEVICES METRO NETWORKNG-MVPN/VPLS/L3VPN/L2VPN

+ IP/MPLS + CoS

L2/L3 EthernetPseudowire Circuit

Emulation

L2/L3 Ethernet

MX Series-2-PE

M120

MX Series-1-PE

EX Series-CSD

BX Series-CSD

3G

4G

2G-RAN NC

3G RANNC/4G GW

Ethernet LinksTDM/ATM LinksBackup Links



Dual Stack-based technology Migration•

Figure 20 depicts the case where the BS and RAN NC have the dual stack capability and can thus support both TDM and Ethernet. The BX7000 is used as a multi-access gateway at the cell/hub site. The Metro Ethernet network provides connectivity between both the TDM and Ethernet interfaces of the BS and RAN NC. The TDM traffic is carried over the metro network using pseudowires and MPLS LSPs as described earlier. The Ethernet traffic also uses the IP/MPLS LSPs.

note: It is possible to reuse the same MPLS LSPs for both TDM and Ethernet traffic based on the design and implementation.

The M Series router acts as the aggregation device for both types of connections. The circuit emulation PICs perform the Ethernet to TDM conversion function. The Metro network can consist of a combination of M Series routers, MX Series routers, or both. The dual stack that enables TDM and Ethernet support on the BX7000 device provides the required flexibility for it to be used either in a hybrid, pure IP/Ethernet or migration scenario.

figure 20: tDM and ethernet coexistence

Solution B: 3G/4G Backhaul Greenfield Deployment SubsetAn all IP/Carrier Ethernet solution is depicted in Figure 21. The BS and RAN NC support native Ethernet connections into a Juniper Networks EX4200 Ethernet Switch that is used as a cell/hub site device. The Metro network is an all IP/Ethernet services-based one that can support MPLS LSPs for data transport, VPN services, CoS, and reliability requirements. The MX Series device is used as an aggregation device in this case. This solution is well-suited for either greenfield 3G or 4G deployments.

figure 21: iP-/ethernet-based mobile backhaul

Table 4 lists the various VPN services and MPLS transport implementation options offered by Juniper. These services and transport options can be implemented in the Metro network.

Ethernet

TDMMobile Core

Network

RAN NCRAN BS

EthernetMetro Network

Ethernet

TDM

AggregationDeviceIP/MPLS LSP

Pseudowire – TDM Emulation

Cell HubSite Device

Mobile CoreNetwork

RAN NCRAN BS

Ethernet L2/L3Metro Network

IP/MPLS + VPNServices CoS

Ethernet Ethernet

Cell HubSite Device



Table 4: Transport and Services Implementation Options

FEATURE IMPLEMENTATION OPTION UNICAST AND MULTICAST SUPPORTMPlS lSP RSVP

LDP

PW setup BGP

LDP

nG-MVPn BGP

VPlS BGP-VPLS

LDP-VPLS

H-VPLS BGP-LDP Interworking

Unicast (Multicast using point-to-point LSP)

Layer 2 Multicast—point to multipoint

l3VPn BGP Unicast (Multicast using point-to-point LSP)

l2VPn BGP Unicast (Multicast using point-to-point LSP)

l2circuits LDP Unicast

Solution-Required DevicesTable 5 shows the list of devices used in case of the migration and greenfield deployment scenarios.

Table 5: List of Devices Used

SCENARIO TYPE DEVICE USED FUNCTION TECHNOLOGIES SUPPORTEDMigration strategy from 2/2 .5 and 3G legacy networks

BX7000 Multi-access gateway TDM/ATM/Ethernet

Pseudowires

CTP Series Cell/hub site gateway device

TDM/Ethernet

M Series routers

Circuit emulation PICs (OC3/T1/E1)

Aggregation devices Ethernet

TDM/ATM

Pseudowires

MPLS LSP

OAM

M Series/MX Series routers

IP/Ethernet metro network

Ethernet

Pseudowires

MPLS LSP

VPN Services

OAM

coexistence of legacy 2G/2 .5G/3G and newer 3G/4G technologies

BX7000 Multiaccess gateway TDM/ATM/Ethernet

Pseudowires

M Series routers

Circuit emulation PICs (OC3/T1/E1)


TDM/ATM

Pseudowires

MPLS LSP

OAM

M Series/MX Series routers


Ethernet

Pseudowires

MPLS LSP

VPN Services

OAM



Table 5: List of Devices Used (continued)

SCENARIO TYPE DEVICE USED FUNCTION TECHNOLOGIES SUPPORTED3G/4G backhaul greenfield deployment

EX3200

EX4200

Cell site gateway device

Hub site gateway device

Ethernet

BX Series Multiaccess gateway Ethernet

MPLS LSP

J Series Cell/hub site gateway device

Ethernet

MPLS LSP

VPN Services

MX Series/M Series routers


MPLS LSP

VPN Services

OAM

MX Series/M Series routers


Ethernet

MPLS LSP

VPN Services

OAM

Design ConsiderationsCertain Layer 2 or Layer 3 capabilities of the BS, RAN NC, or the backhaul equipment determine the design of the network. Some of these factors to consider when designing a mobile backhaul network include:

VLAN Models The VLAN tagging function may not be available on BS in case of the IP/Ethernet solution. The backhaul network design can change depending on whether the BS can perform VLAN tagging.

A location-based VLAN can be considered to be analogous to a Layer 2 ATM or Frame Relay circuit. Packets are tagged with the location-based VLAN information based on the site from where they originated. This location-based VLAN tag is present all through the backhaul network and packets are handed off into the mobile core with the tag information.

A service VLAN tag identifies the service that is being provided on the particular VLAN. The backhaul network could be designed in such a way that each service is offered on a separate VLAN or all the services are bundled into a single pipe that uses one VLAN—that is, one VLAN for all services versus VLAN per service. The service tag may get popped at some point in the backhaul network and does not need to be preserved and sent to the mobile core.

The traffic in the backhaul can thus be separated either based on services or location. There are two scenarios based on whether the frames from the cell tower are VLAN tagged:

tagged frames •

Location and Service tags (Q-in-Q)—The frames coming in from the cell tower are tagged with both location 1. and service information. The location tag is stripped from the frames at the cell site device. The frames are then sent with only the service tags that are recognized all through the network into the core.

Only Location-based tags—The frames coming in from the cell tower are only tagged with the location 2. information. The service tags can be added at the cell site depending on the type of services available at the particular site. Location-based VLAN tags are usually necessary when using a combination of Carrier Ethernet and a legacy Layer 2 network.

untagged frames•

The BS is not capable of tagging the frames with the appropriate location or service information. The frames come in untagged into the cell site device. The appropriate location and service VLAN tags are added on the cell site device. The location VLAN tag information is determined based on the port that the untagged frames were received.



CoS The following factors need to be considered when designing the CoS rules:

The traffic profile and requirement of the granular classification of the traffic streams within a forwarding class •using of MF classifiers—that is, combination of BA and MF classifiers

Type of CoS marking—that is, DSCP versus 802.1p will depend on whether the incoming frames are VLAN tagged.•

Assigning EXP classifiers to traffic based on the VPN routing instances•

MPLS LSPs There can be either a single LSP or multiple LSPs assigned to carry the traffic within the backhaul network. The same MPLS LSP can be used to carry different traffic streams originating and destined to the same VPN instance.

The alternative is to use multiple LSPs—either one per VPN offering or one for each traffic type.

Timing SynchronizationAs mentioned earlier, there are multiple ways of distributing the timing information across the mobile backhaul network— traditional TDM-based timing distribution, packet network-based timing distribution using Adaptive Clock Recovery, 1588v2, and Sync-E and NTPv3/v4. When applying CoS rules, packets carrying adaptive clock recovery timing information need to be classified into the high-priority, low-latency queue. Juniper Networks supports multiple timing synchronization options since a single timing solution does not fit all network types or requirements. 1588v2 is a versatile fit for the IP/Ethernet-based mobile backhaul since it is topology agnostic and supports both frequency and phase.

Failure Recovery and ReliabilityAt the very least, two types of failures need to be considered when designing mobile backhaul networks—link failures and node failures. Juniper Networks products offer protection schemes against failures at both levels. The various failure detection and recovery options include:

oaM•

OAM can provide Carrier Ethernet failure detection at the physical and link levels. Hence it is possible to provide either link or connectivity fault management with this scheme. It also notifies higher layers of failures, thus enabling BFD and fast reroute to repair and provide better recovery times.

lSP link and node Protection•

Enabling MPLS LSP link protection allows the LSP to be rerouted to a different interface on the same affected node through a bypass LSP.

The MPLS LSP node-link protection scheme allows the LSP to be rerouted through a bypass LSP that traverses a different node—that is, the node where the failure occurred is bypassed in favor of a different node.

Another method of providing redundancy could be achieved by dual homing links. In such a case, the following options can be used:

Routing Metrics•

Metrics associated with routing protocol such as link cost can be used to manage active paths over which the traffic is received. Configuring the cumulative cost of say one path to be much lower than the other results in all data traffic and LSPs using the path of least cost. One of the issues with using cost to select the active path is that if there is a failure anywhere along the active path, the LSPs and traffic can get rerouted through an available least cost path, which might not be the preferred path. To avoid this, metrics need to be set at optimal values such that the network administrators can predict the path chosen after every single failure.

Dual homing •

In case of VPLS, the routing instance supports the dual-homing feature. Enabling dual homing within the VPLS instance allows only one link to be active while the other link is in standby or passive mode.

note: Although Routing Trunk Group (RTG) can be used at the Layer 2 level, it is well-suited for enterprise environment rather than service provider networks.



Solution-Type Profiles Solution A: Umbrella SolutionThis section provides the configuration snippets that support the 2G/2.5G legacy technology migration solution information that was discussed in the earlier sections. Figure 24 shows an example of a mobile backhaul network where the BX7000 acts as a multiaccess gateway device for legacy and Ethernet-based technologies. The connections from the BS to the BX7000 device could be either TDM/ATM or Ethernet depending on the type of mobile network. The BX7000 device has outgoing primary and backup Gigabit Ethernet connections to the Metro network. In case of TDM/ATM, it sets up pseudowires to perform circuit emulation across the Metro network. These pseudowires terminate on the M Series device that has a circuit emulation PIC. The PE and P nodes of the Metro network can be interconnected by either Gigabit Ethernet or 10G links. MPLS LSPs can be used as a means to transport all data within the Metro. VPN services such as Layer 2/Layer 3 VPNs can deliver unicast services while VPLS and NG-MVPN can be used for multicast services.

note: Please refer to Table 4 for unicast and multicast service options.

note: When using BGP-based L2VPNs in the Metro network, the BX7000 device can perform LDP-based pseudowire stitching. Here, LDP-based pseudowire is created from the BX7000 to the ingress PE router that is the entry point to the BGP L2VPN domain on the Metro network. The requisite MPLS to BGP L2VPN label translation is performed on this ingress PE. A converse action occurs on the egress PE router that is the exit point of the BGP L2VPN domain. If the aggregation device is a part of this domain, no additional step needs to occur. Figure 22 shows this scenario.

figure 22: aggregation device internal to bGP domain

Also, LDP-based pseudowire should be created from the egress PE router to the aggregation device as shown in Figure 23.

figure 23: aggregation device external to bGP domain

The BX7000 also signals static MPLS LSPs to the M Series aggregation router to transport all pseudowires.

This option leverages the BGP L2 VPN mechanism to provide a solution for the issues previously explained. An LDP- based pseudowire is created from the MAG to the BGP L2 VPN ingress PE, which translates the MPLS outer label into a BGP L2 VPN label. The egress PE router then swaps the labels at the egress of the BGP L2 VPN domain. If it is not part of the BGP L2 VPN domain, the ASG also has an LDP based pseudowire to the egress PE.

Mobile CoreNetwork

RAN NCRAN BS


BGP – L2VPN/VPLS

TDM TDM

Cell HubSite Device Ingress

PE Router Egress

PE Router +Aggregation

Device

IP/MPLS LSP

LDP-basedPseudowire

Mobile CoreNetwork

RAN NCRAN BS


BGP – L2VPN/VPLS

TDM TDM

Cell HubSite Device Ingress

PE Router Egress

PE Router AggregationDevice

IP/MPLS LSP

LDP-basedPseudowire

LDP-basedPseudowire



This scenario has the following benefits:

Scaling: it is not necessary to monitor a large number of pseudowires end to end within the network cloud—•the BGP L2 VPN network provides the control plane and hides the underlying complexity. No provisioning of pseudowires is necessary within the network cloud.

Redundancy: The MAG may just have a “local” redundancy mechanism using a backup pseudowire to the •ingress PE,

Failure detection: The mechanism to detect failure is not end to end but “local” to the ingress PE, matching RAN •backhaul requirements for fast restoration of pseudowires. Detection and restoration within the network cloud is ensured using BGP L2 VPN standard mechanisms. Moreover, BGP L2 VPN dual-homing capabilities may be leveraged to ensure dynamic and transparent protection of the local segment.

figure 24: example—bX7000 specific design

Table 6 lists the configuration snippets of the legacy migration solution using BX7000 and M Series routers that was described in the previous sections. (Please refer to the simplified mobile backhaul view depicted in Figure 18 and Figure 24).

The snippets show the sample configuration to set up E1 interfaces and pseudowires on the BX7000 and E1 interfaces and LSPs on the M Series router. In this example, a 12 port-Channelized T1/E1 PIC provides the circuit emulation capability on the M Series router.

2G

CELL SITE DEVICES METRO NETWORKNG-MVPN/VPLS/L3VPN/L2VPN

+ IP/MPLS + CoS

L2/L3 EthernetPseudowire Circuit

Emulation

MX Series-2-PE

M120-PE

MX Series-1-PE

EX Series-CSD

BX Series-CSD

3G

4G

2G-RAN NC

3G RAN NC/4G GW

Ethernet LinksTDM/ATM LinksBackup Links



Table 6: Code Snippet of BX7000 and M Series Solution

CONFIGURATION SNIPPET EXPLANATIONbX7000—cell Site Device

l2circuit p2 {

admin-state enable;

neighbor-address 31.1.1.1 {

tunnel tnnl2;

interface e1-0/0/1 {

payload 256;

jitter-buffer 5000;

idle-pattern 10;

dummy-pattern 255;

lossy-state-entry 12;

remote-vc-id 2;

}

}

}

}

Pseudowire set up between M Series router and BX7000

e1-0/0/1 {

admin-state enable;

encapsulation trans;

framing unframed;

clock-source ces;

}

E1 interface connected to BS

M Series Router with circuit emulation Pic (aggregation Device) mpls {

label-switch-path tnnl2 {

to-address 31.1.1.1;

from-address 13.1.1.1;

primary tnnl2 {

priority 7 0;

}

}

MPlS lSP tunnel on the aggregation device that can transport the pseudowire from the bX7000

e1-1/2/0 {

satop-options payload-size 256;

clocking external;

encapsulation satop;

e1-options {

framing unframed;

}

unit 0;

}

E1interfaceconfiguredforexternalclocking



Solution B: Greenfield Deployment SubsetThe mobile backhaul subset solution discussed in this section uses a network that can deliver both Layer 2 and Layer 3 services. EX Series or J Series devices are used at the cell or hub site devices while the aggregation is done on an M Series or MX Series router that is a part of the Metro Ethernet network. This Metro network also consists of other MX Series and M Series routers. The BS is connected to the EX Series/J Series devices while the Metro network connects to the RAN NC and mobile core.

Figure 25 shows a sample mobile backhaul network that can be used for greenfield deployments. Gigabit Ethernet connections serve as links between the simulated BS and the EX4200 line of cell site devices (EX Series-1, EX Series-2, and EX Series-3). EX-4 acts as a hub site device to EX Series-1 and EX Series-2. A Juniper Networks MX240 Ethernet Services Router (MX Series-1-PE) that is a part of the Metro Ethernet network aggregates the connections from EX Series-4 and EX Series-3. Another MX240 (MX Series-2-PE) and a Juniper Networks M120 Multiservice Edge Router (M120-PE) complete the Metro network. All the nodes within the Metro network are connected by 10 Gigabit Ethernet links. Redundant links are provided between the node pairs EX Series-4/EX Series-3 and MX Series-1-PE/MX Series-2-PE.

figure 25: Mobile backhaul test network

Figure 26 shows a logical view of the same mobile backhaul network. When using a Q-in-Q VLAN model, the frames coming into the EX4200 devices are double tagged with the location and service tags. The cell site devices strip the location tag and maintained the service tag. In Figure 26, the frames received at the cell site devices contain location tags of 175, 180, and 33, respectively. The service tags 550, 600, and 650 are carried through the network into the core. The Multicast VLAN 1000 is used to deliver multicast streaming video to all the sites.

note: The multicast streaming video is distributed using point-to-point LSPs as opposed to using point-to-multipoint or multipoint-to-multipoint optimization and PIM/IP Multicast.

CELL SITE DEVICES METRO NETWORKVPLS/L3VPN + MPLS + CoS

MX Series-2-PE

M120-PE

MX Series-1-PE

EX Series-34G

Layer 2 LinkLayer 3 LinkCoon Links

EX Series-4

EX Series-23G

EX Series-12G

RAN NC



figure 26: logical view of mobile backhaul network

Figure 27 illustrates the handling of the VLAN tags at the cell site.

figure 27: Vlan tags at cell site

Connections from Site175 and Site180 are Layer 2 Ethernet based while that from Site33 is Layer 3 IP based. As a result the Metro network offers Layer 2-based VPLS and Layer 3-based VPN services to these sites. VPN services in the Metro network introduce the concept of separate routing instances within the Metro network. This concept is based on the logical partitioning of the physical nodes in the Metro network between different services. The network implementation details are discussed in the following sections.

RoutingOSPF or ISIS can be used as the IGP to achieve network connectivity on all IP interfaces. In most cases, these interfaces belong to a single backbone area or level. BGP is required to support the VPLS and L3VPN signaling messages in the Metro network. Enabling BFD on both the IGP routing protocol and BGP results in better fault detection times.

CoSThe CoS scenarios change based on the type of connectivity (that is, Layer 2/3) and services offered. Figure 28 shows the classifiers used in the Layer 2 portion of the network. 802.1p classifiers are used when applying CoS to tagged frames. The cell and hub site devices perform queuing, scheduling, and prioritization based on the 802.1p bit marking. When the frames need to be transported across the Metro network using MPLS LSPs, EXP classifiers are used. Hence, the 802.1p CoS values need to be rewritten into EXP classifiers and transported over the LSPs.

CELL SITEDEVICES

HUB SITEDEVICE

AGGREGATIONDEVICES

METRONETWORK

VPLS + L3VPNRSVP BASED

MPLS

MX240

MX240

MX240

EX3200Cell Site

33 VLAN550VLAN600VLAN650

EX3200

VLAN600

VLAN550

VLAN650

Multicast VLAN1000

EX3200Cell Site

180

EX3200Cell Site

175

VLAN550 (backup)VLAN600 (backup)VLAN650 (backup)

10G Links in Metro (Trunk)

Mobile CoreNetwork

Tag1 – Site175 Tag2 – Service550 Tag2 – Service550



The aggregation device does this in the VPLS instance on the Metro network. A rewrite back from EXP to 802.1p classifiers is done when handing the frames from the Metro in the RAN NC. The converse actions take place on frames destined to the cell site and BS. The CoS classifiers can be applied if necessary on each routing instance.

If the frames received from the BS are untagged, the cell site device can rewrite the DSCP value of the incoming frames to 802.1.p. From there the frames would be rewritten with the EXP value in the Metro and back to DSCP when sending to the RAN NC.

Typically BA classifiers are used to achieve the required CoS guarantees in a network. However, using a combination of BA and MF classifiers introduces an extra level of granularity. Traffic streams within a particular class can be prioritized—for example, prioritizing Web browsing over Telnet traffic within the Interactive queue. In cases where the BS does not mark the incoming packets, the cell site gateway needs to be able to identify the traffic streams, for example, based on port number or IP address and then perform the classification.

note: Default Cos classifiers need to be used to classify traffic in a VPLS instance. In addition to the BA classifiers, MF-based firewall filters can be applied to the CE-facing interfaces on the metro ring nodes to ensure that the packets are classified based on the default EXP into the appropriate queues. The same CoS rules are applied to all core-facing VPLS interfaces.

figure 28: layer 2-based coS

Layer 3 VPN-based CoS involves the use of DSCP or IP precedence marking being rewritten to EXP classifiers at the aggregation device. Figure 29 shows the different classifiers used for the Layer 3-based traffic.

figure 29: layer 3 VPn-based coS

RAN NCBS

802.1p 802.1p 802.1p

802.1p to EXP Rewrite

EXP 802.1p

802.1p 802.1p 802.1p EXP 802.1p

RAN NCBS

IP Precedence IP Precedence IP Precedence EXP IP Precedence

IP Precedence IP Precedence IP Precedence EXP IP Precedence

IP Precedence to EXP Rewrite



Table 7 shows salient CoS configuration steps on the EX Series cell site and MX Series aggregation devices.

Table 7: CoS Config Snippets on EX Series and MX Series Devices

CONFIGURATION SNIPPET EXPLANATIONcell Site Device - eX4200classifiers {

ieee-802.1 DOTP-CLASSIFIER {

forwarding-class CONVERSATIONAL {

loss-priority low code-points ef;

}

forwarding-class INTERACTIVE {

loss-priority low code-points af12;

}

forwarding-class STREAMING {

loss-priority low code-points af11;

}

forwarding-class BACKGROUND {

loss-priority high code-points be;

}

}

}

Definitionof802.1pClassifierstobeappliedonincoming tagged frames. Therearefourqueuesdefined:

CONVERSATIONAL (EF) - Voice

INTERACTIVE – (AF12) – HTTP/Telnet

STREAMING (AF11) – Streaming Video

BACKGROUND (BE) – Email

forwarding-classes {

queue 0 BACKGROUND;

queue 3 CONVERSATIONAL;

queue 2 INTERACTIVE;

queue 1 STREAMING;

}

Forwarding classes are assigned to the respective queues.

rewrite-rules {

ieee-802.1 DOTP-RW {

forwarding-class CONVERSATIONAL {

loss-priority low code-point ef;

}

forwarding-class INTERACTIVE {

loss-priority low code-point af12;

}

forwarding-class STREAMING {

loss-priority low code-point af11;

}

forwarding-class BACKGROUND {

loss-priority high code-point be;

}

}

}

Definestherulestobeappliedwhenarewrite is required.



Table 7: CoS Config Snippets on EX Series and MX Series Devices (continued)

CONFIGURATION SNIPPET EXPLANATIONschedulers {

CONVERSATIONAL-SCHED {

transmit-rate remainder;

buffer-size percent 80;

priority strict-high;

}

INTERACTIVE-SCHED;

STREAMING-SCHED {

transmit-rate percent 20;

}

BACKGROUND-SCHED {

transmit-rate remainder;

priority low;

}

}

Schedulersdefinethebuffersizeandprioritization.

MX Series aggregation Devicerouting-instances {

VPLS-AGG1 {

classifiers {

exp EXP-CLASSIFIER;

}

}

}

EXPclassifiersappliedtotheVPLSroutinginstance.

drop-profiles {

BACKGROUND-DROP {

interpolate {

fill-level [ 20 40 60 80 ];

drop-probability [ 0 50 75 100 ];

}

}

CONVERSATIONAL-DROP {

interpolate {

fill-level [ 90 100 ];

drop-probability [ 0 100 ];

}

}

INTERACTIVE-DROP {

interpolate {

fill-level [ 35 55 75 95 100 ];

drop-probability [ 0 35 55 75 95 ];

}

}

STREAMING-DROP {

interpolate {

fill-level [ 5 25 50 75 ];

drop-probability [ 40 60 80 95 ];

}

}

}

Handling of each queue based on a separate Random EarlyDetection(RED)drop-profile.Additionallevelsof granularity to distinguish between streams of a particulartrafficqueuecanbeaddedbydefiningdifferentdropprofilesforlow,mediumandhighprioritytraffic.



Table 7: CoS Config Snippets on EX Series and MX Series Devices (continued)

CONFIGURATION SNIPPET EXPLANATIONfirewall {

family vpls {

filter MF-CLASSIFIER {

term VOICE {

from {

source-port 5060;

}

then {

count VOICE-CNT;

loss-priority low;

forwarding-class CONVERSATIONAL;

accept;

}

}

term INTER-STREAM-TELNET {

from {

source-port 23;

}

then {

count INTER-STREAM-CNT;

loss-priority medium-low

forwarding-class INTERACTIVE;

accept;

}

}

term INTER-STREAM-SQL {

from {

source-port 3306;

}

then {

count INTER-STREAM-CNT1;

loss-priority medium-high

forwarding-class INTERACTIVE;

accept;

}

}

}

}

}

MFbasedfirewallclassifierisappliedtotheVPLSinstance.

HeretheclassifierlooksfortrafficfromUDPport5060(SIPpackets)andclassifiesthemintotheCONVERSATIONAL class.

Packets destined for UDP port 23 (Telnet) are assigned to the INTERACTIVE forwarding class and marked with a medium-low priority.

Packets destined for UDP port 3306 (SQL) are assigned to the INTERACTIVE forwarding class but marked with a medium-high priority.



VPN ServicesThe VPN services are offered in the Metro network that consists of Juniper Networks MX480 Ethernet Services Router devices (MX Series-PE1 and MX Series-PE2 ) and an M120 (M120-PE3) shown in Figure 25. 10 Gigabit links connect all the three nodes. The metro network highlighted by this solution offers VPLS and L3VPN services. This illustrates the flexibility of service offerings possible when using a Carrier Ethernet- based mobile backhaul network. Both the services use BGP as the underlying mechanism for exchange of signaling information. The routing and MPLS information is contained in separate tables for each instance. Each of these services is discussed in the following section.

VPlS•

VPLS offers a Layer 2-based VPN service that can be used for either unicast or multicast purposes. When using multicast, IGMP snooping and point-to-multipoint LSPs provide optimization. Both unicast and multicast traffic can be carried using point-to-point LSPs across the VPLS network. This example highlights the latter scenario. Figure 30 depicts the VPLS-based logical view of the backhaul network used in the discussion. Please refer to Table 4 for other service implementation options.

One BGP-based VPLS routing instance (VPLS-AGG1) is configured on the three nodes of the metro ring. The VPLS-AGG1 instance is associated with the Layer2 connections from the hub site EX4. This single routing instance can support connections from multiple VLANs (location- or service-based depending on the frames arriving tagged at the cell site). As shown in Figure 30, there are two separate VLANs, 550 and 600, which offer services to the sites 175 and 180, respectively. A third VLAN 1000, termed as a multicast VLAN, offers streaming video to both sites. The hub site device EX4 is dual- homed to the two MX Series PE routers. Dual homing is enabled within the VPLS instance to ensure that only one link is active at a given time.

Point-to-point MPLS LSPs serve as the transport mechanism between all the PE routers in the metro network. EXP-based CoS classifiers are applied to the VPLS instance as discussed in the CoS section. In this scenario, multicast and point to multipoint do not offer much optimization and so the point-to-point LSPs are used to transport both unicast traffic and the multicast streaming video.

Implementation Notes:

A tunnel PIC need not be identified on an MX Series router if point-to-multipoint/IGMP snooping and other •multicast services are not enabled on the network. The “no-tunnel-services” command can be enabled instead.

VPLS only supports the use of default EXP values to classify any VPLS traffic.•

In addition to the BA classifiers, MF-based firewall filters can be applied to the CE-facing interfaces on the •metro ring nodes to ensure that the packets are classified based on the default EXP into the appropriate queues. The same CoS rules are applied to all core-facing VPLS interfaces.



figure 30: VPlS view of mobile backhaul network

Table 8: VPLS Code Snippet

CONFIGURATION SNIPPET EXPLANATIONMX Series-Pe2 - aggregation Router

VPLS-AGG1 { instance-type vpls;

vlan-id all;

interface xe-3/1/0.550;



route-distinguisher 1:500;

vrf-target target:900:500;

protocols {

vpls {

site-range 15;




no-tunnel-services;

site 1 {

site-identifier 1;

multi-homing;

site-preference backup;



interface xe-3/1/0.1000; }

}

}

}

Define instance type, interfaces routing instance information and allow all vlan-ids through the instance . enable dual homing and specify the backup site .

CELL SITE DEVICES METRO NETWORKVPLS + MPLS + CoS

MX Series-2-PE

M120-PE

MX Series-1-PE

EX Series-4

EX Series-2STE 180-600


RAN NC

Multicast VLAN1000

VLANs600

VLANs550

VLANs550 and

600



• l3VPn

L3VPN offers a Layer 3-based VPN service that is typically used for unicast purposes. (When using multicast, PIM and point-to-multipoint LSPs can be used in an NG-MVPN instance.) Figure 31 shows the L3VPN view of the mobile backhaul network under discussion.

One BGP-based L3VPN routing instance (L3VPN-AGG1) is configured on the three nodes of the metro ring. The L3VPN-AGG1 instance is associated with the Layer 3 IP connections from the cell site EX Series-1. This single routing instance can support connections from multiple VLANs (location- or service-based depending on the frames arriving tagged at the cell site). As shown in Figure 31, there is one VLAN 650 that offers services to the site 33 while VLAN 1000 offers streaming video to the sites. The cell site device EX Series-1 is dual homed to the two MX Series PE routers. The OSPF metrics are configured in such a way that the traffic is received only from one of the links.

Point-to-point MPLS LSPs serve as the transport mechanism between all the PE routers in the metro network. EXP-based CoS classifiers are applied to the traffic belonging to the L3VPN instance as discussed in the CoS section. In this scenario, multicast and point to multipoint do not offer much optimization and so the point-to-point LSPs are used to transport both L3 unicast traffic and the multicast streaming video.

figure 31: l3VPn view of mobile backhaul network

CELL SITE DEVICES METRO NETWORKL3VPN + MPLS + CoS

MX Series-2-PE

M120-PE

MX Series-1-PE


VLAN650

VLAN650

RAN NC

Multicast VLAN1000



Table 9 provides a sample L3VPN configuration snippet.

Table 9: L3VPN Code Snippet

CONFIGURATION SNIPPET EXPLANATIONL3VPN-AGG1 {

instance-type vrf;

interface ge-0/1/0.600;

route-distinguisher 900:600;

vrf-import L3VPN-IMPORT;

vrf-export L3VPN-EXPORT;

vrf-target {

target:900:600;

import target:900:600;

export target:900:600;

}

vrf-table-label;

protocols {

bgp {

import L3VPN-IMPORT;

export L3VPN-EXPORT;

graceful-restart;

group L3VPN {

neighbor 11.1.1.9 {

local-address 12.1.1.131;

peer-as 500;

local-as 500;

}

neighbor 12.1.1.3 {


peer-as 500;

local-as 500;

}

}

}

ospf {

domain-id disable;

domain-vpn-tag 0;

export [ L3VPN-EXPORT export ];

import [ L3VPN-IMPORT export ];

area 0.0.0.0 {

interface ge-0/1/0.600 {

bfd-liveness-detection {

minimum-interval 50;

multiplier 3;

}

}

}

}

}

Defineinstancetype,interfacesroutinginstanceinformation and allow appropriate import and export of routes between the PEs.



oaM•

Ethernet Link management OAM is configured to offer reliability and fault detection. The table below gives a sample configuration snippet.

Table 10: OAM Configuration Snippet

CONFIGURATION SNIPPET EXPLANATION ethernet {

link-fault-management {

interface xe-3/1/0 {

pdu-interval 100;

link-discovery active;

remote-loopback;

}


pdu-interval 100;

remote-loopback;

}


pdu-interval 100;

remote-loopback;

}

}

}

configure link fault management on interfaces .

Table 11: BFD

CONFIGURATION SNIPPET EXPLANATION bgp {

group MBHL {

type internal;


family inet {

unicast;

any;

}

peer-as 500;

local-as 500;

bfd-liveness-detection {

minimum-interval 10;

}

BFD enabled on BGP group.

MPlS transport•

RSVP-based LSPs transport the data belonging to different services across the Metro network. Either link protection or fast reroute can be enabled on RSVP and MPLS to provide faster failure recovery. The table below gives a sample configuration of RSVP and MPLS.



Table 12: MPLS Configuration Snippet

CONFIGURATION SNIPPET EXPLANATIONlabel-switched-path MX480-L3-to-M120-L3 {

from 15.1.1.1;

to 17.1.1.1;

fast-reroute;

}

MPLS LSP with fast reroute enabled.

fast-reroute optimize-timer 1;

interface all {

link-protection;

}

RSVP with fast reroute enabled.

network Provisioning, Monitoring, and Diagnostics•

JUNOScope can be used to provision infrastructure such as interfaces, VPN services, CoS, MPLS LSP, and routing—and maintains a database of all this information. History of essential parameters such as Jitter, Delay, Packet loss, and Clock variation needs to be made available to the network operator. Bulk statistics and real-time performance monitoring (RPM) support provide an additional layer of network monitoring and performance measurement. Third-party software such as IBM ITNM can be used to monitor the status of the network and services.

Table 12 shows a sample SNMP configuration snippet on the MX Series router that can send alarms, traps, and events to the network management system.

Table 13: SNMP Configuration Snippet

CONFIGURATION SNIPPET EXPLANATIONsnmp {

view mpls {

oid mplsLspEntry.2 include;

}

view general {

oid jnxOperatingTemp;

oid .1.3.6.1.1.3;

oid ip.12;

}

view jnxRedundancySwitchoverCount {

oid jnxRedundancyEntry.8;

}

view jnxCosIfqTailDropPktRate {

oid jnxCosIfqStatsEntry.12;

}

view jnxPowerSupplyFailure {

oid 1.3.6.1.4.1.2636.4.1.1 include;

}

view jnxCmCfgChange {

oid 1.3.6.1.4.1.2636.4.5.0.1;

}

view jnxCmRescueChange {

oid 1.3.6.1.4.1.2636.4.5.0.2;

}

Configuretrapandeventrelatedinformation, specify community



Table 13: SNMP Configuration Snippet (continued)

CONFIGURATION SNIPPET EXPLANATION(continued)

community public;

trap-options {

source-address 172.28.113.131;

}

trap-group MBHL {

categories {

authentication;

chassis;

link;

remote-operations;

routing;

startup;

rmon-alarm;

vrrp-events;

configuration;

}

targets {

172.28.113.48;

}

}

routing-instance-access;

rmon {

event 1 {

type snmptrap;

}

}

}

(continued)

ConclusionJuniper products offer mobile network operators a wide range of backhaul options. The comprehensive solutions based on the BX7000, EX4200, and M Series/MX Series routers address both the needs of green field/new 4G technology deployments or migration from legacy technologies such as TDM or ATM to IP-/Ethernet- and MPLS-based networks.

AppendixesExamples of Deployment ScenariosJ Series as an Access DeviceFigure 32 shows a J Series device used as the access gateway for a 4G pure IP/Ethernet scenario. The J Series device is capable of applying CoS, delivering VPN services and setting up MPLS LSPs. The LSPs from the J Series can either terminate on the ingress or egress PE router of the Metro network. Similarly, the J Series device can also participate in the VPN service based on the network design and requirements.


38

corporate and Sales headquarters Juniper Networks, Inc. 1194 North Mathilda Avenue Sunnyvale, CA 94089 USA Phone: 888.JUNIPER (888.586.4737) or 408.745.2000 Fax: 408.745.2100

aPac headquartersJuniper Networks (Hong Kong) 26/F, Cityplaza One 1111 King’s Road Taikoo Shing, Hong Kong Phone: 852.2332.3636 Fax: 852.2574.7803

eMea headquartersJuniper Networks Ireland Airside Business Park Swords, County Dublin, Ireland Phone: 35.31.8903.600 Fax: 35.31.8903.601

Copyright 2009 Juniper Networks, Inc. All rights reserved. Juniper Networks, the Juniper Networks logo, JUNOS, NetScreen, and ScreenOS are registered trademarks of Juniper Networks, Inc. in the United States and other countries. JUNOSe is a trademark of Juniper Networks, Inc. All other trademarks, service marks, registered marks, or registered service marks are the property of their respective owners. Juniper Networks assumes no responsibility for any inaccuracies in this document. Juniper Networks reserves the right to change, modify, transfer, or otherwise revise this publication without notice.

8030008-001-EN Jun 2009 Printed on recycled paper.

To purchase Juniper Networks solutions, pleasecontact your Juniper Networks representative

at 1-866-298-6428 or authorized reseller.

figure 32: J Series as an access device

CTP Series as an Access DeviceFigure 33 shows Juniper Networks CTP Series Circuit to Packet Platforms used as an access device in a legacy TDM network. The CTP Series platform performs the requisite TDM to Ethernet conversion and vice versa.

figure 33: ctP Series as an access device

About Juniper NetworksJuniper Networks, Inc. is the leader in high-performance networking. Juniper offers a high-performance network infrastructure that creates a responsive and trusted environment for accelerating the deployment of services and applications over a single network. This fuels high-performance businesses. Additional information can be found at www .juniper .net.

Mobile CoreNetwork

RAN NCRAN BS


VPN + CoS+ MPLS

Ethernet Ethernet

J SeriesCell/Hub Site DeviceCoS + MPLS + VPN

M Series/MX SeriesEgress PE

Router

M Series/MX SeriesIngress PE Router +Aggregation Device

IP/MPLS LSP

Mobile CoreNetwork

RAN NCRAN BS


VPN + CoS+ MPLS

TDM TDM

CTP SeriesCell/Hub

Site DeviceM Series/MX Series

IngressPE Router

M Series/MX Series Egress

PE Router +Aggregation Device

IP/MPLS LSP

Ethernet

Documents

Juniper Mobile Backhaul