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Evaluation of Alcatel-Lucent IP/MPLSMobile Backhaul Solution

Areas of Evaluation:

GSM/UMTS/HSPA Mobile Backhaul and RAN AggregationCDMA/EVDO Mobile Backhaul and RAN AggregationCircuit Emulation Services over Packet NetworkNetwork Synchronization over Packet NetworkResiliency and Redundancy

Isocore Internetworking LabIsocore Technical DocumentReference: ITD-13016v1.4Version (v1.4): 06/23/2008

I S O C O R E T E C H N I C A L R E P O R T

EXECUTIVE SUMMARY

OverviewIn April 2008 Isocore was commissioned to carry out an independent, comprehensive evaluation and testingof Alcatel-Lucent’s IP/MPLS portfolio for mobile backhaul — a part of the Alcatel-Lucent Mobile EvolutionTransport Architecture (META).

Isocore set forth stringent test requirements for IP/MPLS Mobile Backhaul (MBH). The test requirements werebased on information provided by Isocore’s service provider members. The tests were designed to address theactual mobile backhaul needs and real-life requirements of the mobile service providers.

We evaluated and tested Alcatel-Lucent IP/MPLS products – focusing on the Alcatel-Lucent 7750 Service Routerand the Alcatel-Lucent 7705 Service Aggregation Router as Systems Under Test (SUT) - for CDMA/EVDO andGSM/UMTS/HSPA backhaul, as well as for transport of Circuit Emulated Services (CES) and timing distributionover IP/MPLS.

This report summarizes the key findings of the tests conducted.

Special focus was placed on resiliency — the ability to recover — as a key theme for this event. For this reason,numerous failure and recovery scenarios were evaluated and tested.

In addition, emphasis was placed on evaluating and testing of the ability to support growing bandwidth demandsfrom the radio access network (RAN). For this purpose, RAN scalability was introduced through scaling of thelinks carrying base station traffic (multiclass MLPPPfor CDMA/EVDO and ATM/IMA for GSM/UMTS/HSPA).

Isocore validates the tested Alcatel-Lucent IP/MPLS architectures, related platforms and features a flexible,reliable and deployable end-to-end complete solution for mobile backhaul (MBH) for CDMA/EVDO andGSM/UMTS/HSPA. With successful testing of Circuit Emulation Services, adaptive timing recovery anddifferential timing distribution over packet switched network (PSN), Isocore also finds the Alcatel-LucentIP/MPLS solution a reliable and deployable solution for transport of Circuit Emulation Services in realnetworks and the implementation of timing distribution over IP/MPLS stable and reliable.

These tests certify that today’s Alcatel-Lucent IP/MPLS solutions to the cell site fully support all 2G and 3Gtechnologies and that the solution satisfies and exceeds the requirements for resilient voice services, networktiming, and general high availability mobile transport. The tests also verify and highlight the readiness of theIP/MPLS mobile backhaul solution to support tomorrow’s 4G, LTE, and enhanced packet core solutions as theymove to complete end to end IP.

2 Isocore Internetworking Lab

3Isocore Internetworking Lab

TECHNICAL OVERVIEW

For the purpose of this testing, a simulated RAN environment — for CDMA/EVDO and GSM/UMTS/HSPA—was created to impose significant stress on the system under test. To verify the stability of the tested platformsand consistency of the results, multiple iterations of each test were conducted, with extended traffic tests run ona nightly basis across all CMDA/EVDO and GSM/UMTS/HSPAMBH interfaces and services. The informationbelow captures the test bed overview and key results.

T E S T O V E R V I E W :• 1,650 base stations aggregated across a shared CDMA/EVDO and GSM/UMTS/HSPA environment:– Over 1550 base stations supported redundant MBH connections using multilink bundles(MLPPP and ATM/IMA), dual homed with multi-chassis automatic protections switching or both– Averaged 2.8 DS1/E1 circuits for MBH per base station

• 113 channelized OC3 and OC12 ports (using Any Service Any Port cards)• Total of 4,874 active DS1 and E1 circuits in the network

K E Y R E S U L T S :• All CDMA/EVDO and GSM/UMTS/HSPAMBH tests were performed successfully.• All resiliency tests were performed successfully and demonstrated the following failover times(worst cases numbers reported):– 2.7 ms - intra-chassis HA SF/CPM switchover with stateful MLPPP for CDMA/EVDO– 810 ms - inter-chassis (MC-APS) switchover for MLPPP, with stateful MLPPPfor CDMA/EVDO

– 1.2 ms - intra-chassis HA SF/CPM switchover for CES and ATM/IMA for GSM/UMTS/HSPA– 154 ms - inter-chassis (MC-APS) switchover for CES and ATM/IMA

• All Circuit Emulation Services (CES) tests were performed successfully:– Tests included multiple extended-duration hitless traffic runs with no traffic loss.– 24-hour wander measurements of adaptive and differential timing for CES.

• Measured MTIE and TDEV results stayed well under the ANSI/T1.101 defined mask

Isocore confirms that Alcatel-Lucent passed all tests and fulfilled all requirements assembled for this evaluationand testing event. Testing of resiliency mechanisms and features provides assurance that voice calls can bemaintained even in catastrophic node failure scenarios, as the recovery mechanisms and features were able tosuccessfully preserve integrity of these calls. The tested systems exhibited stability throughout the testing eventand delivered consistent results.

CONTENTS

EXECUTIVE SUMMARY .......................................................................................................................................................................................................................... 2

TECHNICAL OVERVIEW .......................................................................................................................................................................................................................... 3

1 INTRODUCTION.................................................................................................................................................................................................................. 5

2 CDMA/EVDO IP MOBILE BACKHAUL EVALUATION ................................................................................................................................................................ 6

2.1 VALIDATING A DEPLOYABLE COLLAPSED CDMA IPBH ARCHITECTURE .................................................................................................................................... 6

2.1.1 Verification of stateful MLPPP resiliency with multichassis APS (MC-APS) in case of link, card and node failures ................................................................ 8

2.1.2 Verification of stateful MLPPP resiliency with multichassis APS (MC-APS) in case of switching fabric/control processing module failures (high availability)...................................................................................................................................................... 11

2.1.3 Multiclass MLPPP with 4 QoS (MC-4)................................................................................................................................................................................ 11

3 GSM/UMTS/HSPA IP/MPLS MOBILE BACKHAUL EVALUATION ............................................................................................................................................ 13

3.1 VALIDATING IP/MPLS BACKHAUL FOR GSM/UMTS/HSPA ENVIRONMENTS ........................................................................................................................ 13

3.1.1 Resiliency of GSM/UMTS/HSPA IP/MPLS MBH ................................................................................................................................................................ 16

3.2 EVALUATION OF NETWORK SYNCHRONIZATION TECHNIQUES.............................................................................................................................................. 17

3.3 SIMULATION OF BASE STATIONS (BTS, NODE-B) AND RADIO CONTROLLERS BSC/RNC ........................................................................................................ 20

4 CONCLUSION .................................................................................................................................................................................................................. 22

5 LIST OF ACRONYMS USED ................................................................................................................................................................................................ 23



1 Introduction

This report provides a summary of Isocore’s independent evaluation of Alcatel-Lucent’s IP/MPLS mobilebackhaul (MBH) solutions for CMDA/EVDO and GSM/UMTS/HSPA environments. In order to optimize theavailable hardware resources, a single testbed was used to evaluate the two mobile technologies simultaneously.All testing was conducted under conditions that emulated large-scale real-world radio access network (RAN)environments. Under all conditions, all services were operational simultaneously.The key areas of evaluation included:• Basic tests of MBH for CDMA/EVDO and GSM/UMTS/HSPA• MBH scalability tests:– Large scale RAN IP/MPLS backhaul for GSM/UMTS/HSPA deployments– Large scale RAN IP backhaul with MLPPP for CDMA and EVDO deployments– Large scale aggregation of base station traffic using multilink bundles(ATM/IMA for UMTS/HSPA and MLPPP for CDMA/EVDO)

• MBH resiliency tests:– Inter-nodal failover with multichassis APS for CES, ATM (IP/MPLS) and MLPPP (IP)

• Included multiple link, card and node fault convergence scenarios– Intra-nodal high availability SF/CPM failover for all active services– Pseudowire redundancy protection for IP/MPLS MBH

• CES, ATM and ATM/IMA over redundant pseudowires (RPW)– Protection of MLPPP states across different nodes using MC-APS for IP BH

• Evaluation of MBH architectures related to IP and IP/MPLS MBH• Evaluation of synchronization options and timing distribution over packet-based network– Adaptive clock recovery (ACR) with extended wander measurements for CES– Differential timing with extended wander measurements for CES

• MBH latency and impact on the services MBH quality of service (QoS)– Testing of multiple QoS classes with multi-class 4 and MLPPP for CDMA/EVDO

Isocore placed emphasis on evaluating the end-to-end network availability of the MBH solutions presentedby Alcatel-Lucent. Numerous test cases were conducted on the end-to-end resiliency of the platforms andarchitecture. Multiple iterations of each case were executed to assure consistency of the measurements.

Another key requirement in MBH deployments is the ability to support the increased bandwidth requirementsimposed Åon the mobile aggregation layer by the traffic (new, bandwidth-intensive mobile services). MultipleDS1/E1 circuits are bound together using MLPPP or ATM/IMA to support the bandwidth requirements of nextgeneration MBH deployments. The ability to support large scale aggregation of multilink bundles was considereda key requirement for this event.

The architectures evaluated in this evaluation and testing event were those presented by Alcatel-Lucent for theirIP and IP/MPLS MBH deployments. The primary systems under test (SUT) were the 7750 Service Router and the7705 Service Aggregation Router. The following variants for these product lines were used: the 7750 SR-12, the 7750SR-7 and the 7705 SAR-8.

A single 7750 SR-12 was used to emulate all BTS and Node-B sites as well as Base Station Controller/RadioNetwork Controller (BSC/RNC) functionality for GSM/UMTS/HSPA. To emulate mobile subscriber traffic and togenerate multi-class traffic flows for high/low priority data, voice, and control traffic, Isocore utilized the AgilentN2X multi-service test solution. Agilent N2X offered comprehensive measurements of individual streams (latency,jitter, packet loss), which were critical for the validation of the Alcatel-Lucent IP/MPLS MBH solution.


2 CDMA/EVDO IP MOBILE BACKHAUL EVALUATION

This section provides details of Isocore’s evaluation and testing of Alcatel-Lucent’s RAN backhaul architecturefor CDMA and EVDO for IP mobile backhaul (IP MBH). Typically, CDMA deployments involve use of IPdirectly from the base station (BTS). The use of legacy transport options has resulted in a requirement to sendIP using PPP (over SONET type of transport), and MLPPP has been used in order to increase the bandwidth ofthis mode of transport – by bundling several member DS1 links into the aggregated MLPPP group. This approachcalls for the deployment of separate aggregation routers (AR), which aggregate the traffic from a base transceiverstation (BTS), and multilayer switches (MLS) – a Layer 2 switch – used to connect to the essential sub-elementsof a CDMAMobile Switching Center (MSC) – Radio Network Controller (RNC), Mobility Manager (MM) andpacket switch (PS). As CDMAmobile technology has evolved towards EVDO, the aggregation devices havealso varied, requiring multiple devices used for aggregation and switching.

The architecture Alcatel-Lucent presented for evaluation and testing used a simplified CDMA RAN architecturein which one element – the 7750 Service Router – performs the combined functionality of the aggregation router(AR) and Multi-Layer Switch (MLS). Typically, aggregation routers and multilayer switches are deployed inredundant pairs, and for the same reason the 7750 SR routers were deployed in a redundant pair. In this report,we will be referring to this architecture as “collapsed AR+MLS architecture” or “collapsed CDMA/EVDO IPBHarchitecture”.

Isocore placed emphasis on evaluating the deployability (applicability in real-life deployments) of this collapsedCDMA/EVDO IPBH architecture, the involved platforms and their related feature set. Considerable time wasspent evaluating the resiliency of the architecture and platforms in simulated large scale RAN environment.

2 .1 VA L I D A T I N G A D E P L O YA B L E C O L L A P S E D C D M A I P B H A R C H I T E C T U R E

Figure 1 shows the detailed setup used to evaluate Alcatel-Lucent’s collapsed CDMA/EVDO IPBH architecture.The primary systems under test (SUTs) were two 7750 SR-7s. The SUT aggregated the traffic coming from 604fully protected base stations (BTS). Each BTS was configured to use MLPPP bundling and the MLPPP sessionswere terminated on L3 routed interfaces on the aggregation router (7750 SR-7). A total of 2600 DS1s coming fromBTS sites were configured as member links to MLPPP bundles. The 604 MLPPP groups were configured withone, two, four or eight DS1 member links per bundle. On the aggregation routers a total of 32 OC3 ports wereconfigured for the CDMA/EVDO test environment. Multichassis APS (MC-APS) protection was enabled in orderto achieve stateful preservation of the MLPPP groups and member links between two adjacent aggregation routers.

Alcatel-Lucent defines the stateful protection of the MLPPP groups as follows: in the case of a failure of thephysical link carrying the traffic with active MLPPP sessions, the mechanism of protection (which involvesAPS or MC-APS) is such that it ensures end integrity of MLPPP groups (terminated on the aggregation routerpair), so it is not required to re-initiate MLPPP sessions (allocation of member links to MLPPP groups andsynchronization between endpoints). This implementation results in much shorter convergence times andpreservation of voice calls in progress. This stateful protection covers multiple failure scenarios such as: link,card, port and Switching Fabric / Central Processing Module (SF/CPM) failures.

For these tests, working (protected) and protection links were equally split across the two SUTs. This setuprepresented a large-scale real-world deployment for CDMA and EVDO IP MBH.


In our tests, a 7750 SR-12, shown on the left side in figure 1 was used to simulate the combined functionalityof large numbers of base stations (BTSs) and a digital cross-connect system (DACS). This 7750 SR-12terminated all 32 working and protection OC3 channelized circuits, carrying 1208 combined active andstandby MLPPP bundles, with 2600 DS1 member links.

ARP mediation was required between the 10 Gigabit Ethernet attached N2X test solution and each of theprotected MLPPP bundle pairs. In order to perform this functionality, 604 local ARP-mediation pseudowireswere configured on the 7750 SR-12 and verified per draft-ietf-l2vpn-arp-mediation.

Figure 1: Testing Alcatel-Lucent collapsed CDMA/EVDO IPBH architecture

The QoS requirements can differ for CDMA and EVDO IPBH. For this test all 1208 (604 fully protectedpairs) CDMA/EVDO MLPPP BH terminations were configured with support of multi-class MLPPP, (MC-4),allowing each MLPPP bundle to have four (4) unique traffic classes (from now on referred to as forwardingclasses (FCs). Separate FCs were used for control traffic, voice, high-priority data and low-priority data. EachFC had a separate queue and scheduling rate. Alcatel-Lucent’s MC-4 implementation can dynamically adjustthe bandwidth (BW) allocation across FCs when a member link(s) (DS1s) is lost.


The setup included evaluation of basic functionality – proper termination of MLPPP sessions. The tests wereconducted and latency for different types of traffic was measured. During these basic tests – with allCDMA/EVDO and GSM/UMTS/HSPA traffic running concurrently — the voice latency averaged 2.0 ms andeven latency of low-priority best effort (BE) data traffic stayed below 3 ms in an uncongested state. Latencymeasurements for the CDMA/EVDO were measured across a cascaded setup involving three nodes: the 7750SR12 (used for BTS emulation), a 7750 SR-7 (deployed as RAN aggregation router), and a 7450 Ethernet ServiceSwitch (ESS-1) – which was used to simulate the MSC environment — MM, PS and RNC, which are typicallyconnected in Layer 2 switched environment (to an MLS). During these tests, obtained latency measurements wereconsistent and even under severe congestion voice latency remained below the required 5 ms range for criticalvoice and control traffic. Latency under congested states is covered in the next sections (see under MC-4 QoStesting).

Throughout the event, numerous iterations of link, card, SF/CPM and catastrophic node-level failures wereconducted. Throughout the test event all traffic (CDMA/EVDO and GSM/UMTS/HSPA) was run overnight tovalidate the stability of the deployment. Traffic was run for these long durations without loss. Even with theconsiderable traffic stress, all systems remained stable throughout the event. Table 1 summarizes the scalingnumbers used for the CDMA/EVDO IP BH test.

Table 1: Summary of CDMA and EVDO IP MBH configuration

DETAILS OF NETWORK AND NODAL ELEMENTS VERIFIED FOR CDMA IP MBH

CDMA Network Details:

• 604 MLPPP protected bundles on each 7750 SR-7 (AR) (with MC-APS )

• A mix of MLPPP groups (bundles) – using 1, 2, 4 and 8 DS1s member links

• 1300 total DS1 member links configured per 7750 SR-7 (AR)

• 1208 MLPPP bundles terminated on 7750 SR12 (BTS)

• 2600 DS1s member links terminated on 7750 SR12 (BTS)

• 604 L3 Interfaces per 7750 SR-7 (AR) used for MLPPP aggregation from BTS

• 604 multiclass MLPPP (MC-4) QoS profiles per 7750 SR-7 (AR)

• 32 total OC3 links supported with MC-APS on the 7750 SRs

• Traffic integrity verification of voice, control traffic, high-priority data and low-priority data

2.1.1 VERIFICATION OF STATEFUL MLPPP RESILIENCY WITH MULTICHASSIS APS (MC- APS) IN CASE OF LINK, CARD AND NODE FAILURES

The tested Alcatel-Lucent CDMA/EVDO IP MBH architecture provides protection against link, card, SF/CPM,and node failures. In accordance with explanation made to Isocore by Alcatel-Lucent, it was expected thatregardless of the network fault, the BTS would not require renegotiation of MLPPP sessions. Also, in order toassure that voice calls are not being dropped by the Mobile Switching Center (MSC), traffic interruption (or loss)should never exceed 5 seconds.

All failure scenarios were carried out using a large scale of concurrent MLPPP sessions (i.e., the tests were notdone on one individual MLPPP sessions running at the time). To validate the functionality and performance ofAlcatel-Lucent stateful MLPPP with MC-APS implementation, the following tests were conducted:•Link-layer fault (fiber cut and port shutdown scenarios)•Multiple port shutdowns•Card-level failures (card pull)•Catastrophic node failures (bringing down the whole node)•High availability validation of SF/CPM (switching fabric/central processing module) failures.


Figure 2 illustrates the setup that was used for failing the working (protected) multilink groups from one aggre-gation router (7750 SR-7) to another. The logical MC-APS link included a working (protected) SONET link onone node and a protection link on the adjacent neighbor AR. The working and protection links were equally splitacross the SUTs. Each of the 604 protected MLPPP bundle pairs were protected by MC-APS. The MC-APS wasconfigured to revert back to the working facility link one minute after a fault was cleared. Revert was used for thisevent to maintain the location of the 32 OC3 working and protect circuits throughout the event and to demonstratethe recovery times associated with revertive behavior.

During all failure scenarios the MLPPP states representing the BTS sites were monitored on the 7750 SR-12(BTS) to verify if they remained up and active. The traffic flows originating from the Agilent N2X platform usedthe same traffic profiles as the basic setup. Traffic loss was measured separately from the aggregation networktowards the BTS and from the BTS towards the aggregation network.

Figure 2: Verification of 7750 SR stateful MLPPP and MC-APS implementation

Table 2 shows the results of failure scenarios executed by command line interface (CLI), and table 3 shows resultsof physical interruptions caused by fiber cuts or card pulls.

As expected, traffic from the MSC to the BTS exhibits a higher loss due to the higher number of “in-flight”packets impacted in the outbound direction (towards BTS). Multiple iterations of each test case were conductedto validate consistency of the measurements and worst case numbers are presented in the respective tables. Basictraffic flows of control traffic, voice, high-priority data and low-priority data were used for all measurements.


Table 2: Results summarizing the stateful MLPPP link recovery through MC-APS (case of link failures)

RECOVERY TIMES FOR ADMINISTRATIVELY INDUCED FAILURES (USING MC-APS)

• Single port failure with MC-APS – Failing link between AR and BTS with 21 MLPPP bundles

•Recovery times from MSC to BTS – 810ms

•Recovery times from BTS to MSC – 80ms

• Single port failure with MC-APS – Recovering link between AR and BTS with 21 MLPPP bundles

•Revert times from MSC to BTS – 403ms

•Revert times from BTS to MSC – 130ms

• Four port failure with MC-APS – Failing link on RAN side (towards BTS) with 176 MLPPP bundles

•Recovery times from MSC to BTS – 917ms

•Recovery times from BTS to MSC – 210ms

• Four port failure with MC-APS – Recovering link between AR and BTS with 176 MLPPP bundles

•Revert times from MSC to BTS – 967ms

•Revert times from BTS to MSC – 640ms

Multiple fiber cuts were performed by scripting the CLI shutdown of multiple ports simultaneously. Card failuresconsisted of pulling out the 4-port OC3 Any Service Any Port (ASAP) MDAs which failed multiple ports simul-taneously. The results show that regardless of the number of ports failed – during port and card level failovers —the worst-case traffic loss was below 1 second.

Node-level failure scenarios of the aggregation routers were also conducted. The AR (7750 SR-7) was rebootedwhile the MLPPP states were monitored at the BTS (7750 SR-12), and traffic loss was measured in each direction.

During the node-level failures, 16 OC3 SONET links were interrupted, including 8 working OC3 MC-APS linkscarrying traffic from 302 base stations (MLPPP bundles) with 750 DS1 member links in total.

It is important to note that during all node-level failures, the entire end-to-end IP BH architecture was being tested,including the L2 switch (7450 ESS-12), configured with spanning tree protocol (STP), which simulated the MSCenvironment.

The worst-case node-level failure resulted in traffic loss for 2.07 seconds, which was well below the targetof 5 seconds — a requirement set forth by Isocore based on input from mobile providers.

Table 3: Results summarizing the MLPPP link recovery through MC-APS (case of fiber cuts)

RECOVERY TIMES FOR PHYSICAL DISRUPTIONS INCLUDING FIBER CUTS AND CARD PULL-OUTS (USING MC-APS)

• Single fiber pull-out with MC-APS – failing link between AR and BTS with 21 MLPPP bundles

•Recovery times towards BTS – 576ms

•Recovery times towards MSC – 100ms

• Single fiber insertion (link up) with MC-APS – recovering link between AR and BTS with 21 MLPPP bundles

•Revert times towards BTS – 576ms

•Revert times towards MSC – 100ms

• Four (4) fiber pull-outs (MDA pull-out) with MC-APS – failing link between AR and BTS with 176 MLPPP bundles



• MDA insertion with MC-APS – recovering link between AR and BTS with 176 MLPPP bundles

•Revert times towards BTS – 588ms

•Revert times towards MSC – 270ms

• Node failure on AR 1 (reboot) – 302 MLPPP bundles




Administratively-induced and physical failures were repeatedly executed in order to stress the configuredprotection in form of MC-APS. During all these repeated tests no instance of MLPPP sessions was lost.The tests confirmed that traffic which is sent from the MSC to all wireless subscribers was minimally impacted.The MC-APS recovery time was consistent for each of the failure scenarios and at no point was any systeminstability detected.

Based on the results presented in table 2 and 3, Isocore confirms the Alcatel-Lucent implementation of MC-APSsupports the stateful protection of the MLPPP sessions and that this implementation is robust and scalable.

2 .1. 2 V E R I F I C A T I O N O F S T A T E F U L M L P P P R E S I L I E N C Y W I T H M U LT I C H A S S I S A P S ( M C - A P S )I N C A S E O F S W I T C H I N G F A B R I C / C O N T R O L P R O C E S S I N G M O D U L E F A I L U R E S ( H I G H AVA I L A B I L I T Y )

Our assessment also included the evaluation and testing of Alcatel-Lucent 7750 SR high availability (HA) featureset – full redundancy of the control complex which supports non-stop routing and non-stop services, includingstateful MLPPP sessions and MC-APS functionality. The HA feature set was verified during the tests by failingthe SF/CPM and measuring the impact to forwarded traffic while monitoring the active MLPPP states. The testsincluded failing the SF/CPM on the aggregation routers (7750 SR-7) and also on the BTS (7750 SR-12) node.

The tests were performed with all CDMA/EVDO traffic being simultaneously active. To measure HAperformance, the same basic traffic flows were exercised to all 604 BTS. Similarly, all HA tests performedon 7750 SR12 (simulating a large number of BTSs) included the combined case of concurrently activeCDMA/EVDO and GSM/UMTS/HSPA traffic.

Isocore confirmed that during HA failovers, the MLPPP sessions stayed active and no transitions were noted onany of the MC-APS ports or member DS1 links. The impact to traffic was minimal, with worst case of 2.7 ms fortraffic loss. The tests confirmed that stateful MLPPP implementation by Alcatel-Lucent is fully supported by theobservations of this test. Table 4 summarizes the test results of the HA testing.

Table 4: Results summarizing the recovery times for HA MLPPP failover

RECOVERY TIMES FOR HIGH AVAILABILITY FAILURE SCENARIOS (FAILURE OF SF/CPM WHEN USING MC-APS)

• MC-APS with MLPPP high availability on 7750 SR-12 (SF/CPM card pull-out)

•Worst case traffic loss after multiple SF/CPM failovers — 3.5µs

•No loss of MLPPP bundles observed

• MC-APS with MLPPP high availability on 7750 SR-7 Aggregation Router 1 (SF/CPM pull-out)

•Worst case traffic loss — 2.7ms

•No loss of MLPPP bundles observed

2 .1. 3 M U LT I C L A S S M L P P P W I T H 4 Q O S ( M C - 4 )

As presented in the basic setup in section 2.1.1, all of the CDMA/EVDO MLPPP bundles were configured withMC-4 QoS to support multiple classes of traffic (forwarding classes). This section provides an overview of theevaluation testing of the Alcatel-Lucent MC-4 implementation under conditions of traffic congestion and alsothe evaluation and testing of the ability to dynamically adjust the bandwidth (BW) allocation if a DS1 memberlink in an MLPPP bundle is lost.

The test focused on ten (10) MLPPP bundles, each configured with four (4) DS1 member links. The MLPPPbundles carried voice, control traffic, high-priority data and low-priority data. Table 5 shows the forwardingclasses defined for each of the forwarding classes. The bandwidth percentage shown in the table represents thebandwidth allocated to a specific forwarding class, and is expressed as maximum allowed. Under congestion,voice and control traffic are scheduled with a strict priority over the data classes. The allocation of bandwidth to

four classes stayed in effect in cases of failures — the stated percentages were also supposed to stay in effectfor the adjusted bandwidth (after DS1 member links were lost), and this is shown in table 6.

The data rates shown represent the total bandwidth transmitted by the Agilent N2X in the egress direction to driveeach forwarding class across all 10 MLPPP bundles. The table also shows the latency measured with traffic levelsnear saturation for the 4xDS1 member links.

Table 5: Traffic types (forwarding classes) used for the multiclass QoS evaluation

TRAFFIC TYPE FORWARDING CLASS PERCENTAGE OF BW DATA RATE LATENCY

Network control Network Control max 200 Kbps 2.66 ms

Voice Expedited Forwarding 85% 1.5 Mbps 2.46 ms

High-priority data Assured Forwarding 66% 1.5 Mbps 2.67 ms

Low-priority data Best Effort 33% 3 Mbps 2.74 ms

Table 6 summarizes the results for three different test cases:

Test case 1 introduced congestion by increasing the BE low-priority data from 3 Mbps to 4.5 Mbps.

Test case 2 used the same traffic profiles but introduced a shutdown of a single DS1 member link on each of the10 MLPPP bundles, reducing the bandwidth available to each bundle.

Test case 3 shut down a second DS1 member link on each MLPPP bundle, further reducing the availablebandwidth to each MLPPP bundle.

The table shows worst case latency values. In all three cases, the latency of critical-priority voice traffic remainedwell below 5 ms. Test case 3 represented a case of severe network traffic congestion, and both high-priority andlow-priority data traffic was lost. However, high-priority data had significantly more throughput even in the caseof this severe traffic congestion.

Table 6: MC-4 test case results

TEST CASE 1 TEST CASE 2 TEST CASE 3BE CONGESTION SINGLE DS1 DOWN TWO DS1S DOWN

WITH BE CONGESTION WITH BE CONGESTION

Total traffic 7.7 Mbps 7.7 Mbps 7.7 Mbps

BW available 6.144 Mbps 4.608 Mbps 3.072 Mbps

Traffic loss Latency Traffic loss Latency Traffic loss Latency

Network control No 4.28 ms No 4.26 No 4.40 ms

Voice No 4.08 ms No 4.23 No 4.36 ms

High-priority data No 4.36 ms No 4.58 5.8% 94 ms

Low-priority data 32% high high high high high


3 GSM/UMTS/HSPA IP/MPLS MOBILE BACKHAUL EVALUATIONThis section presents the results of the evaluation and testing of Alcatel-Lucent’s architecture, platforms andrelated feature set for IP/MPLS MBH for GSM/UMTS/HSPA mobile services. The GSM/UMTS/HSPA IP/MPLSBH was tested simultaneously with the CDMA and EV-DO IP MBH (i.e. common test equipment was used forMBH for both GSM/UMTS/HSPA and CDMA/EVDO and all the tests were done with GSM/UMTS/HSPA andCDMA/EVDO simultaneously present). Emphasis in these tests was placed on the deployability of thearchitecture, platforms and related features specific to GSM/UMTS/HSPA, as well as to MBH resiliency.

3 .1 VA L I D A T I N G I P / M P L S B A C K H A U L F O R G S M / U M T S / H S PA E N V I R O N M E N T S

Figure 3 shows the physical topology of the network used for the evaluation and testing of Alcatel-LucentIP/MPLS MBH solution for GSM/UMTS/HSPA. The testbed was composed of base station simulation layer,mobile aggregation layer, MPLS transport layer and the base station controller/radio network controller(BSC/RNC) layer. The base station simulation included the Agilent N2X multi-service test solution attached to the7750 SR-12 using 10 Gigabit Ethernet interfaces. The radio access network (RAN) aggregation layer aggregatedthe simulated base stations (Node-B sites) carrying ATM VCs, ATM IMA bundles and CES services. The MPLStransport used LDP MPLS signaling and transported ATM/IMA and CES based services over redundantpseudowires (RPWs). The BSC/RNC layer was configured with multichassis APS protection. All CES, ATM/IMAand ATM VCs MBH services originating on the 7750 SRs in the aggregation layer were protected with RPWs.

Figure 3: Test architecture for Alcatel-Lucent IP/MPLS backhaul for GSM/UMTS



The ATM/IMA bundles provided redundancy to the Node-B site with two E1 or DS1 member links per IMAbundle. The ATM VCs were dual homed to both aggregation routers (ARs) and protected by MC-APS and RPWsat the RAN AR. This provided two ATM E1 terminations for the redundant Node-B aggregation.

All CES, ATM-VC and ATM/IMAMBH services originating on the 7750 SRs were protected within the MPLSnetwork and at the BSC/RNC by RPWs and MC-APS. The RPWs were configured to track the MC-APS edgeprotection across the RAN AR and BSC/RNC nodes respectively.

Since the GSM/UMTS/HSPA architecture focused on IP/MPLS BH with RPWs, CES was also tested in thisenvironment. CES transport is not unique to GSM/UMTS/HSPAMBH and can also be deployed in CDMA/EVDOenvironments. An OC3 CES port was configured on AR 1 (with 84 DS1 CES services per OC3). To stayconsistent with MBH applications, structured transport of TDM DS1 circuits was used, implemented as per RFC5086. 56 of the CES DS1 based services originating on AR1 were transported to the BSC/RNC edge, where theywere protected by MC-APS and RPWs. The remaining 28 CES DS1s were transported over pseudowires to thetwo 7705 SAR deployed as ARs (14 to the each 7705 SAR). The CES services on the 7750 SR-7s used theexternal Stratum 1 primary reference clock (PRC) applied to the system’s BITS input. The 7705 SARs derivedtheir timing from the adaptive clock received on the CES circuit. To further stress the adaptive clock recovery, theCES services destined to the 7705 SARs were routed within the packet-switched network (PSN) using multiplehops.

The handoff from the MPLS transport to the BSC/RNC used a pair of 7750 SR-7 routers. Typically, these edgerouters support many ARs using an MPLS transport. For this reason, these 7750 SR nodes were lightly equipped –with a mix of clear-channel OC12 ATM ports and OC3 channelized ASAP ports, and OC3 CES ports. Inter-noderedundancy was provided by MC-APS and RPWs for the CES, ATM and ATM IMAMBH services.

Figure 3 shows the logical representation where the 7750 SR-12 was used to simulate the Node-B (base station)sites (shown on the left) and also the BSC/RNC functionality (as shown on the right). The 7750 SR-12 wasconfigured with thousands of local ATM-to-Ethernet interworking pseudowires to support the Ethernet-to-ATMhandoff between the 10 Gigabit Ethernet attached Agilent N2X tester and the ATM based GSM/UMTS/HSPAenvironment. The 7750 SR-12 had a total of 2274 E1 and DS1 terminations from the combined AR and BSC/RNChandoffs related to the GSM/UMTS/HSPA setup. Table 7 summarizes the scaling numbers verified during the testfor the GSM/UMTS/HSPA environment.


Table 7: Baseline scaling setup for GSM/UMTS/HSPA IP/MPLS backhaul and aggregation

NETWORK AND NODE TOTALS VERIFIED FOR UMTS RAN AGGREGATION

GSM/UMTS/HSPA — Network Overview

•1046 combined Node-B IP/MPLS MBH sites

•646 IMA-based IP/MPLS MBH sites

• 316 ATM VC IP/MPLS MBH sites

• 84 CES IP/MPLS MBH sits

• 2274 E1 and DS1 terminations used for GSM/UMTS/HSPA MBH

GSM/UMTS/HSPA — 7750 SR-7 Aggregation Router Overview:

•630 protected ATM/IMA based IIP/MPLS MBH sites

• 252 7750 SR-7 AR 1

• 378 7750 SR-7 AR 2

• All ATM/IMA MBHs protected by RPWs and MC-APS at the BSC/RNC

• 252 protected ATM VCs IP/MPLS MBH sites

• 252 protected ATM VC dual homed to both ARs using MC-APS

• Protected at RAN and BSC/RNC by MC-APS and RPW

• 84 CES IP/MPLS MBH sites on AR 1

• 56 CES IP/MPLS BHs protected RPWs and MC-APS at the BSC/RNC

• 28 CES IP/MPLS BHs transported to 7705 SARs ARs

GSM/UMTS/HSPA – 7705 SAR-8 Aggregation Router Overview:

• 28 CES DS1s based IP/MPLS BH

• 16 ATM IMA IP/MPLS BH

• 64 ATM VC IP/MPLS BH

Traffic verification of all services included voice, control, high-priority data and low-priority data traffic

Overnight traffic runs were conducted across all GSM/UMTS/HSPA and CDMA/EVDO services simultaneously.The traffic was active for all traffic types (and forwarding classes configured), including voice, control traffic,high-priority data and low-priority data traffic. Repeated overnight runs were executed without traffic loss orany other signs of performance degradation. Latency measurements were made across four nodes for theGSM/UMTS/HSPA environment — this included two hops across the 7750 SR12 for BTS and BSC/RNC simu-lation, one hop for the RAN AR and one hop for the BSC/RNC router. Voice averaged 3 ms of latency for theATM-based GSM/UMTS/HSPA traffic. Latency remained consistent and low across the network regardless ofthe test cases.

All CES services showed stability throughout the event, and CES tests included multiple overnight runs withoutany detected/recorded traffic loss. All of the ATM VC, ATM/IMA and CES traffic on the 7705 SARs used theadaptive clock recovery using CES throughout the event. The tests were conducted over the course of multipleextended traffic runs, totaling more than 50 hours and no packet loss was encountered on the 7705 SARs. This isa good indication that the adaptive clock recovery implementation on the 7705 SAR is stable. Further evaluationof the CES timing implementation is covered below (see dedicated section).

Throughout the event considerable stress was placed on the nodes by repeatedly failing different elements suchas links, cards and central processing modules, and also by starting and stopping traffic randomly. At no pointduring the tests was there any sign of instability on any of the systems tested. Isocore is comfortable stating theAlcatel-Lucent GSM/UMTS/HSPA IP/MPLS MBH was successfully evaluated and tested during this event.

3 .1.1 R E S I L I E N C Y O F G S M / U M T S / H S PA I P / M P L S M B HMultiple resiliency test cases were conducted on the GSM/UMTS/HSPA setup including link, node, and highavailability SF/CPM test cases. All test cases except the HA SF/CPM test case were focused on inter-nodeconvergence scenarios where traffic converged to the adjacent node. Figure 4 shows the redundancy verificationsetup for the GSM/UMTS/HSPA tests.The GSM/UMTS/HSPA test cases included the use of redundant pseudowires in the IP/MPLS transport layer.When the MC-APS becomes engaged, failure of the node results in the fail-over switching to the protection circuiton the adjacent node, and the RPW converges with the edge. LDP was used as the MPLS signaling protocol todemonstrate that there was no influence on the RPWs by RSVP fast reroute (FRR) protection. Traffic loss wasmeasured in each direction and all services were tested. Table 8 provides the results of the various resiliency testcases.

Figure 4: GSM/UMTS/HSPA redundancy for PWs for CES, ATM-VC and ATM IMA

Isocore exercised the resiliency of the each component in this setup to ensure that end-to-end resiliency is func-tional and consistent, and that the RPW protection tracks the edge convergence. The access redundancy was verifiedby failing the working MC-APS circuit and ensuring the functionality of the PW redundancy. It’s important tonote that the CES services were also supported by MC-APS and RPWs. In the case of APS failovers the worstcase loss was 154 ms core to edge, measured at the BSC/RNC for CES. Table 8 summarizes the results for theGSMUMTS/HSPA resiliency test cases. In all cases multiple iterations were conducted and worst case numbersare shown.



Table 8: Resiliency and PW redundancy failure recovery measures

RECOVERY TIMES WITH PW REDUNDANCY AND MC-APS FOR ATM VCS AND IMA

RAN AR protection link failure of MC-APS carrying 252 ATM VC each with RPWs

•Single port fiber pull: Failing APS link carrying ATM traffic between AR 1 and Node-B

• Traffic loss from Node-B edge to MPLS core — 52ms

• Traffic loss from MPLS core to Node-B edge — 220ms

BSC/RNC protection link failure of MC-APS carrying 56 DS1 based CES each with RPWs

•Single port shutdown: Failing APS link carrying ATM traffic at the BSC/RNC

• Traffic loss from BSC/RNC towards MPLS core — 100ms

• Traffic loss from MPLS core to BSC/RNC — 154ms

BSC/RNC protection link failure of MC-APS carrying 252 ATM VC each with RPWs

•Single port fiber pull: Failing APS link carrying ATM traffic at the BSC/RNC edge

• Traffic loss from BSC/RNC to MPLS core — 60ms

• Traffic loss from MPLS core to BSC/RNC — 188ms

BSC/RNC protection link failure of MC-APS carrying 384 ATM IMA each with RPWs

•Single port shutdown: Failing APS link carrying ATM traffic at the BSC/RNC

• Traffic loss from MPLS core to BSC/RNC - 105ms

• Traffic loss from BSC/RNC to MPLS core- 100ms

BSC/RNC node failure for UMTS/GSM MBH 636 ATM/IMA, 252 ATM VC and 56 CES each with RPWs

• Traffic loss from MPLS core to BSC/RNC – 1.24 sec

• Traffic loss from BSC/RNC towards MPLS core – 0.42 sec

HA SF/CPM failover for UMTS/GSM RAN AR ATM/IMA, ATM VC and CES

• Worst case traffic loss – 1.2ms

3 . 2 E VA L U AT I O N O F N E T W O R K S Y N C H R O N I Z A T I O N T E C H N I Q U E S

This section describes the evaluation of Alcatel-Lucent’s adaptive clock recovery and differential timing imple-mentation for CES services. Using the CES setup as a part of the GSM/UMTS/HSPA evaluation described asabove, a JDSU ANT-20 advanced network tester was used to perform 24 hour wander measurements on separateadaptive and differential timing setups.

The setup for the adaptive timing test is shown in figure 5. A Stratum 1 clock was used as a reference clock intoSUT-A for CES packet generation and into the ANT-20 for comparison to the adaptive CES clock. SUT-B wasconfigured to use the adaptive clock recovered from the CES for the as its central clock reference. The networkincluded four IP/MPLS hops across the PSN. The ANT-20 tester was set to run a wander measurement of theadaptive timing at SUT-B. The adaptive clock wander test measurements included time interval error (TIE), max-imum time interval error (MTIE), and time deviation (TDEV), as defined by the ITU-T G.810 recommendation.


Figure 5: Multi-hop CESoPSN PWs setup used for adaptive clocking wander measurements

Figure 6 below shows the results of the wander measurements on the adaptive recovered timing (clock). In orderto pass the test, the MTIE and TDEV measurements are expected to stay below the respective MTIE and TDEVmask shown in the chart. The actual test results showed that the measured MTIE and TDEV results stayed wellunder the ANSI/T1.101 mask. This comprehensive performance measure assures proper clock recovery andsynchronization of the network when deploying for adaptive clock recovery using CES across a packet-switchednetwork (PSN).

Figure 6: MTIE analysis for recovered adaptive clock


The setup for the wander measurements of differential clocking is shown in figure 7. For this test a TDMmultiplexer was added to provide an offset between the STM1 and embedded E1 as is expected in realSDH/SONET networks. The differential test included a 7710 SR-c12 as SUT A and a 7750 SR7 as SUT B.Each node was configured with an OC3/STM1 CES port with SDH framing and E1 channelization. The MUX,SUT A and SUT B used an external Stratum 1 reference clock and ANT20 used an offset from this Stratum 1reference clock. SUT A extracts the embedded E1 from the STM1 and applies a timestamp to the RTP headerwhich includes the difference between the reference clock (GPS) and the received E1 clock (GPS+offset). SUT Bretrieves the timestamp from the RTP header and, using the offset and its local reference clock (GPS) regeneratesthe original clocking from the ANT-20.

Figure 7: Setup used for the differential clock wander measurement

The differential wander test was run for 24 hours and MTIE was measured. The results graph in figure 8 showsthat the MTIE stayed well below the mask and successfully passed the ITU-T G.8261 criteria. This comprehensiveperformance measure verifies that the differential timing implementation using CES was able to adjust thedifferential clock source to match the reference clock at SUT-B. This is essential for CES services to be supportacross endpoints with different timing references.


Figure 8: MTIE plot against ITU-T G.8261 Case 1

3 . 3 S I M U L AT I O N O F B A S E S T A T I O N S ( B T S , N O D E - B ) A N D R A D I O C O N T R O L L E R S B S C / R N CThe Alcatel-Lucent 7750 SR-12 and Agilent N2X were used to simulate all of the Node-B and BTS equipment,DACS equipment, BSC/RNC functional blocks and all related traffic load and analysis for this event. Figure 9represents the setup of these platforms and presents the scaling numbers that were applied to the 7750 SR-12.Although references to the mobile elements (base stations, controllers, switches) were used throughout the report,Isocore feels it is important to present the details of what was involved to perform the simulation for thisevaluation. Although the 7750 SR-12 was not considered a primary SUT and the same can be said about the7450 ESS, their performance was vital to the success of the tests.

The 7750 SR-12 was a part of every convergence and performance measurement made during the evaluationand testing. The scalability and performance of the system was nothing less than impressive.

The Agilent N2X was a critical tool used to support the analysis requirements for this event. It wasn’t enough justto spot-measure the latency or packet loss on a subset of streams — this event required being able to monitor andmeasure latency and packet loss for any of the more than 10,000 traffic streams instantaneously present during thetesting. The ability to sort them all by peak latency or loss was critical to the extensive real-time analysisperformed during this event.


Figure 9: Alcatel-Lucent 7750 SR-12 simulation node and Agilent N2X


4 CONCLUSION

Isocore’s evaluation of Alcatel-Lucent’s IP/MPLS MBH solution is the first of its kind in the industry andthe most comprehensive third party validation of IP/MPLS mobile backhaul technologies ever conducted.The event is significant in the scope and breadth of technologies that Alcatel-Lucent was able to support ona single test bed. The platforms under test supported two highly-scaled MBH environments – CDMA/EVDOand GSM/UMTS/HSPA – concurrently. The fact that the evaluation considered many technologies includingpseudowire redundancy, multilink bundles, ATM/IMA, ATM/VC, QoS for MLPPP bundles, in parallel to scaledIP MBH, IP/MPLS MBH and CES MBH on a single product set is commendable. Isocore put the entire test envi-ronment and the many technologies tested under considerable scrutiny to ensure the accuracy of observations made.

The high scalability of the Alcatel-Lucent 7750 was confirmed by the system under test successfully aggregatingtraffic from 1650 MBH sites (base stations). But more imperative were the number of DS1/E1 circuits supportedper site. Each of the 1650 emulated base stations had an average of 2.8 DS1/E1s circuits per site. This is signif-icant in the amount of bandwidth that can be allocated per base station in real-world deployments and in meetinga key requirement of next generation MBH networks. Even though the 7750 SR12 was not considered a primarySUT, the scalability of the platform was crucial in simulating the entire Node-B, BTS equipment, and BSC/RNCfunctional blocks. With over 4800 DS1 and E1 terminations on a single 7750 SR12, the performance and stabilityof this node was vital to the success of the test event.

Through the execution of large numbers of failure scenarios and consistently low recovery times Isocore concludesthat Alcatel-Lucent resiliency implementation is comprehensive and is end-to-end. The ability to protect thestateful MLPPP sessions and implementation of pseudowire redundancy supporting the MC-APS for fasterconvergence was distinctive. Similar to the scalability results, the findings of resiliency tests were consistentand passed all the test limits set forth by Isocore.

Throughout the entire test cycle, Isocore placed emphasis on assuring that all executed test cases and the evaluatedfeature-set were relevant to real-world deployments. To fulfill this requirement, many tests were repeatedly carriedout to ensure the consistency of the results. Using the same methodology, many of the multiclass traffic-verificationtests were conducted for long duration, with several overnight runs to monitor the traffic loss and the system sta-bility. In all instances, the observed results were consistent. Concerted effort was placed on verifying deployablecircuit emulation services by extensively evaluating network synchronization using adaptive and differential clockrecovery implementations. There was no observed traffic loss in any of the tests performed for measuring the clock-ing accuracy for adaptive and differential clock recovery. Throughout the tests, the Alcatel-Lucent CES showedstable synchronous, adaptive, and differential timing.

With the consistency of results observed throughout the entire effort, Isocore concludes that the testedAlcatel-Lucent META architecture, related platforms and feature-set is reliable and the solution is deployablefor supporting end-to-end mobile backhaul services for CDMA/EVDO and GSM/UMTS/HSPA. The scope ofthe evaluation and breadth of technologies verified in this validation confirms the readiness of the solution forcarrier-class deployments. Isocore feels confident to say that the Alcatel-Lucent platforms and features relatedto IP/MPLS MBH are complete, scalable and robust.


5 LIST OF ACRONYMS USED

3G1x Third Generation Wireless TechnologyACR Adaptive Clock RecoveryAR Aggregation RouterBSC Base Station ControllerBTS Base Transceiver StationBW BandwidthCDMA Code Division Multiplexed AccessCES Circuit Emulation ServicesDS1 Digital Signal 1DUT Device Under TestEV-DO Evolution – Data OptimizedGSM Global System for Mobile communicationHA High AvailabilityHSPA High Speed Packet AccessIMA Inverse multiplex for ATMIOM InterfaceL2 Layer 2 TechnologiesL3 Network Layer 3 TechnologiesMBH Mobile BackhaulMC-4 Multi Class 4MC-APS Multi-Chassis Automatic Protection SwitchingMLPPP Multilink PPPMLS Multi Layer SwitchMM Mobility ManagerMPLS Multi-Protocol Label SwitchingMSC Mobile Switching CenterMTIE Maximum Time Interval ErrorNode-B BTS in UMTS EnvironmentPPP Point to Point ProtocolPS Packet SwitchRAN Radio Access NetworkRNC Radio Network ControllerSR Service RouterSAR Service Aggregation RouterSF/CPM Switch Fabric/Control Processor ModuleSUT System Under TestTDEV Time DeviationTIE Time Interval ErrorUMTS Universal Mobile Telecommunication SystemsVC Virtual Circuit

I S O C O R E T E C H N I C A L R E P O R T

12359 Sunrise Valley Drive, Suite 100Reston, VA 20190Phone: 703.860.1777Fax: 703.860.1778www.isocore.com

© Isocore. All rights reservedFor more information about the testing capabilities of the Internetworking lab, please email [email protected] document should not be reproduced as a certification or a validation reference from Isocore.Reproduction of this document to a third party requires written approval from Isocore Corporation.

About IsocoreIsocore provides technology validation, certification andproduct evaluation services in emerging and next generationInternet and wireless technologies. Isocore is leadingvalidation and interoperability of novel technologies includingMPLS, Carrier Ethernet, IPv6, IP Optical Integration, wirelessbackhauling and Layer 2/3 Virtual Private Networks (VPNs),IPTV service deployment architecture validation, andcertification of other provider backbone technologies.Major router and switch vendors, Service Providers,and test equipment suppliers participate in Isocore activities.Isocore has major offices in the USA (the Washington DC area),Europe (Paris, France) and Asia (Tokyo, Japan).

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