Evaluation of Alcatel-Lucent IP/MPLS Mobile Backhaul Solution

24 Pages·2008·2.45 MB·English

I S O C O R E T E C H N I C A L R E P O R T
Evaluation of Alcatel-Lucent IP/MPLS
Mobile Backhaul Solution
Areas of Evaluation:
GSM/UMTS/HSPA Mobile Backhaul and RAN Aggregation
CDMA/EVDO Mobile Backhaul and RAN Aggregation
Circuit Emulation Services over Packet Network
Network Synchronization over Packet Network
Resiliency and Redundancy
Isocore Internetworking Lab
Isocore Technical Document
Reference: ITD-13016v1.4
Version (v1.4): 06/23/2008
EXECUTIVE SUMMARY
Overview
InApril 2008 Isocore was commissioned to carry out an independent, comprehensive evaluation and testing
ofAlcatel-Lucent’s IP/MPLS portfolio for mobile backhaul — a part of theAlcatel-Lucent Mobile Evolution
TransportArchitecture (META).
Isocore set forth stringent test requirements for IP/MPLS Mobile Backhaul (MBH).The test requirements were
based on information provided by Isocore’s service provider members.The tests were designed to address the
actual mobile backhaul needs and real-life requirements of the mobile service providers.
We evaluated and testedAlcatel-Lucent IP/MPLS products – focusing on theAlcatel-Lucent 7750 Service Router
and theAlcatel-Lucent 7705 ServiceAggregation Router as Systems UnderTest (SUT) - for CDMA/EVDO and
GSM/UMTS/HSPAbackhaul, as well as for transport of Circuit Emulated Services (CES) and timing distribution
over 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 demands
from the radio access network (RAN). For this purpose, RAN scalability was introduced through scaling of the
links carrying base station traffic (multiclass MLPPP
for CDMA/EVDO andATM/IMAfor GSM/UMTS/HSPA).
Isocore validates the testedAlcatel-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 and
GSM/UMTS/HSPA.With successful testing of Circuit Emulation Services, adaptive timing recovery and
differential timing distribution over packet switched network (PSN), Isocore also finds theAlcatel-Lucent
IP/MPLS solution a reliable and deployable solution for transport of Circuit Emulation Services in real
networks and the implementation of timing distribution over IP/MPLS stable and reliable.
These tests certify that today’sAlcatel-Lucent IP/MPLS solutions to the cell site fully support all 2G and 3G
technologies and that the solution satisfies and exceeds the requirements for resilientvoiceservices,network
timing,andgeneralhighavailabilitymobiletransport.Thetestsalsoverifyandhighlightthereadinessofthe
IP/MPLSmobilebackhaulsolutiontosupporttomorrow’s4G,LTE,andenhancedpacketcoresolutionsasthey
movetocompleteendtoendIP.
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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 platforms
and consistency of the results, multiple iterations of each test were conducted, with extended traffic tests run on
a nightly basis across all CMDA/EVDO and GSM/UMTS/HSPAMBH interfaces and services.The information
below captures the test bed overview and key results.
TEST OVERVIEW:
•1,650 base stations aggregated across a shared CDMA/EVDO and GSM/UMTS/HSPAenvironment:
– Over 1550 base stations supported redundant MBH connections using multilink bundles
(MLPPPandATM/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 (usingAny ServiceAny Port cards)
•Total of 4,874 active DS1 and E1 circuits in the network
KEY RESULTS:
•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 HASF/CPM switchover with stateful MLPPPfor CDMA/EVDO
– 810 ms - inter-chassis (MC-APS) switchover for MLPPP, with stateful MLPPP
for CDMA/EVDO
– 1.2 ms - intra-chassis HASF/CPM switchover for CES andATM/IMAfor GSM/UMTS/HSPA
– 154 ms - inter-chassis (MC-APS) switchover for CES andATM/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 andTDEVresults stayed well under theANSI/T1.101 defined mask
Isocore confirms thatAlcatel-Lucent passed all tests and fulfilled all requirements assembled for this evaluation
and testing event.Testing of resiliency mechanisms and features provides assurance that voice calls can be
maintained even in catastrophic node failure scenarios, as the recovery mechanisms and features were able to
successfully preserve integrity of these calls.The tested systems exhibited stability throughout the testing event
and delivered consistent results.
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CONTENTS
EXECUTIVESUMMARY..........................................................................................................................................................................................................................2
TECHNICALOVERVIEW..........................................................................................................................................................................................................................3
1 INTRODUCTION..................................................................................................................................................................................................................5
2 CDMA/EVDOIPMOBILEBACKHAULEVALUATION................................................................................................................................................................6
2.1 VALIDATINGADEPLOYABLECOLLAPSEDCDMAIPBHARCHITECTURE....................................................................................................................................6
2.1.1 VerificationofstatefulMLPPPresiliencywithmultichassisAPS(MC-APS)incaseoflink,cardandnodefailures................................................................8
2.1.2 VerificationofstatefulMLPPPresiliencywithmultichassisAPS(MC-APS)incaseofswitchingfabric/
controlprocessingmodulefailures(highavailability)......................................................................................................................................................11
2.1.3 MulticlassMLPPPwith4QoS(MC-4)................................................................................................................................................................................11
3 GSM/UMTS/HSPAIP/MPLSMOBILEBACKHAULEVALUATION............................................................................................................................................13
3.1 VALIDATINGIP/MPLSBACKHAULFORGSM/UMTS/HSPAENVIRONMENTS ........................................................................................................................13
3.1.1 ResiliencyofGSM/UMTS/HSPAIP/MPLSMBH................................................................................................................................................................16
3.2 EVALUATIONOFNETWORKSYNCHRONIZATIONTECHNIQUES..............................................................................................................................................17
3.3 SIMULATIONOFBASESTATIONS(BTS,NODE-B)ANDRADIOCONTROLLERSBSC/RNC........................................................................................................20
4 CONCLUSION..................................................................................................................................................................................................................22
5 LISTOFACRONYMSUSED................................................................................................................................................................................................23
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1 Introduction
This report provides a summary of Isocore’s independent evaluation ofAlcatel-Lucent’s IP/MPLS mobile
backhaul (MBH) solutions for CMDA/EVDO and GSM/UMTS/HSPAenvironments. In order to optimize the
available 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/HSPAdeployments
– Large scale RAN IPbackhaul with MLPPPfor CDMAand EVDO deployments
– Large scale aggregation of base station traffic using multilink bundles
(ATM/IMAfor UMTS/HSPAand MLPPPfor CDMA/EVDO)
•
MBH resiliency tests:
– Inter-nodal failover with multichassisAPS 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 andATM/IMAover redundant pseudowires (RPW)
– Protection of MLPPPstates across different nodes using MC-APS for IPBH
•
Evaluation of MBH architectures related to IPand 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 MLPPPfor CDMA/EVDO
Isocore placed emphasis on evaluating the end-to-end network availability of the MBH solutions presented
byAlcatel-Lucent. Numerous test cases were conducted on the end-to-end resiliency of the platforms and
architecture. Multiple iterations of each case were executed to assure consistency of the measurements.
AnotherkeyrequirementinMBHdeploymentsistheabilitytosupporttheincreasedbandwidthrequirements
imposed Åon the mobile aggregation layer by the traffic (new, bandwidth-intensive mobile services). Multiple
DS1/E1 circuits are bound together using MLPPPorATM/IMAto supportthebandwidthrequirementsofnext
generationMBHdeployments.Theabilitytosupportlarge scale aggregation of multilink bundles wasconsidered
akeyrequirementforthisevent.
The architectures evaluated in this evaluation and testing event were those presented byAlcatel-Lucent for their
IPand IP/MPLS MBH deployments.The primary systems under test (SUT) were the 7750 Service Router and the
7705 ServiceAggregation Router.The following variantsfortheseproductlineswereused:the7750SR-12,the7750
SR-7andthe7705SAR-8.
Asingle 7750 SR-12 was used to emulate all BTS and Node-B sites as well as Base Station Controller/Radio
Network Controller (BSC/RNC) functionality for GSM/UMTS/HSPA.To emulate mobile subscriber traffic and to
generate multi-class traffic flows for high/low priority data, voice, and control traffic, Isocore utilized theAgilent
N2X multi-service test solution.Agilent N2X offered comprehensive measurements of individual streams (latency,
jitter, packet loss), which were critical for the validation of theAlcatel-Lucent IP/MPLS MBH solution.
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2 CDMA/EVDO IP MOBILE BACKHAUL EVALUATION
This section provides details of Isocore’s evaluation and testing ofAlcatel-Lucent’s RAN backhaul architecture
for CDMAand EVDO for IPmobile backhaul (IPMBH).Typically, CDMAdeployments involve use of IP
directly from the base station (BTS).The use of legacy transport options has resulted in a requirement to send
IPusing PPP(over SONETtype of transport), and MLPPPhas been used in order to increase the bandwidth of
this mode of transport – by bundling several member DS1 links into the aggregated MLPPPgroup. This approach
calls for the deployment of separate aggregation routers (AR), which aggregate the traffic from a base transceiver
station (BTS), and multilayer switches (MLS) – a Layer 2 switch – used to connect to the essential sub-elements
of a CDMAMobile Switching Center (MSC) – Radio Network Controller (RNC), Mobility Manager (MM) and
packet switch (PS). As CDMAmobile technology has evolved towards EVDO, the aggregation devices have
also varied, requiring multiple devices used for aggregation and switching.
The architectureAlcatel-Lucent presented for evaluation and testing used a simplified CDMARAN architecture
in 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 in
redundant 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 “collapsedAR+MLS architecture” or “collapsed CDMA/EVDO IPBH
architecture”.
Isocore placed emphasis on evaluating the deployability (applicability in real-life deployments) of this collapsed
CDMA/EVDO IPBH architecture, the involved platforms and their related feature set. Considerable time was
spent evaluating the resiliency of the architecture and platforms in simulated large scale RAN environment.
2.1 VALIDATING A DEPLOYABLE COLLAPSED CDMA IPBH ARCHITECTURE
Figure 1 shows the detailed setup used to evaluateAlcatel-Lucent’s collapsed CDMA/EVDO IPBH architecture.
The primary systems under test (SUTs) were two 7750 SR-7s.The SUTaggregated the traffic coming from 604
fully protected base stations (BTS). Each BTS was configured to use MLPPPbundling and the MLPPPsessions
were terminated on L3 routed interfaces on the aggregation router (7750 SR-7).Atotal of 2600 DS1s coming from
BTS sites were configured as member links to MLPPPbundles.The 604 MLPPPgroups were configured with
one, two, four or eight DS1 member links per bundle. On the aggregation routers a total of 32 OC3 ports were
configured for the CDMA/EVDO test environment. MultichassisAPS (MC-APS) protection was enabled in order
to achieve stateful preservation of the MLPPPgroups and member links between two adjacent aggregation routers.
Alcatel-Lucent defines the stateful protection of the MLPPPgroups as follows: in the case of a failure of the
physical link carrying the traffic with active MLPPPsessions, the mechanism of protection (which involves
APS or MC-APS) is such that it ensures end integrity of MLPPPgroups (terminated on the aggregation router
pair), so it is not required to re-initiate MLPPPsessions (allocation of member links to MLPPPgroups and
synchronization between endpoints).This implementation results in much shorter convergence times and
preservation 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.
Forthesetests,working(protected)andprotectionlinkswereequallysplitacrossthetwoSUTs.This setup
represented a large-scale real-world deployment for CDMAand EVDO IPMBH.
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In our tests, a 7750 SR-12, shown on the left side in figure 1 was used to simulate the combined functionality
of large numbers of base stations (BTSs) and a digital cross-connect system (DACS).This 7750 SR-12
terminated all 32 working and protection OC3 channelized circuits, carrying 1208 combined active and
standby MLPPPbundles, with 2600 DS1 member links.
ARPmediation was required between the 10 Gigabit Ethernet attached N2X test solution and each of the
protected MLPPPbundle pairs. In order to perform this functionality, 604 localARP-mediation pseudowires
were configured on the 7750 SR-12 and verified per draft-ietf-l2vpn-arp-mediation.
Figure1:TestingAlcatel-LucentcollapsedCDMA/EVDOIPBHarchitecture
The QoS requirements can differ for CDMAand EVDO IPBH. For this test all 1208 (604 fully protected
pairs) CDMA/EVDO MLPPPBH terminations were configured with support of multi-class MLPPP, (MC-4),
allowing each MLPPPbundle to have four (4) unique traffic classes (from now on referred to as forwarding
classes (FCs). Separate FCs were used for control traffic, voice, high-priority data and low-priority data. Each
FC had a separate queue and scheduling rate.Alcatel-Lucent’s MC-4 implementation can dynamically adjust
the bandwidth (BW) allocation across FCs when a member link(s) (DS1s) is lost.
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The setup included evaluation of basic functionality – proper termination of MLPPPsessions.The tests were
conducted and latency for different types of traffic was measured. During these basic tests – with all
CDMA/EVDO and GSM/UMTS/HSPAtraffic running concurrently — the voice latency averaged 2.0 ms and
even latency of low-priority best effort (BE) data traffic stayed below 3 ms in an uncongested state. Latency
measurements for the CDMA/EVDO were measured across a cascaded setup involving three nodes: the 7750
SR12 (used for BTS emulation), a 7750 SR-7 (deployed as RAN aggregation router), and a 7450 Ethernet Service
Switch (ESS-1) – which was used to simulate the MSC environment — MM, PS and RNC, which are typically
connected in Layer 2 switched environment (to an MLS). During these tests, obtained latency measurements were
consistent and even under severe congestion voice latency remained below the required 5 ms range for critical
voice and control traffic. Latency under congested states is covered in the next sections (see under MC-4 QoS
testing).
Throughout the event, numerous iterations of link, card, SF/CPM and catastrophic node-level failures were
conducted.Throughout the test event all traffic (CDMA/EVDO and GSM/UMTS/HSPA) was run overnight to
validate the stability of the deployment.Traffic was run for these long durations without loss. Even with the
considerable traffic stress, all systems remained stable throughout the event.Table 1 summarizes the scaling
numbers used for the CDMA/EVDO IPBH test.
Table1:SummaryofCDMAandEVDOIPMBHconfiguration
DETAILS OF NETWORK AND NODAL ELEMENTS VERIFIED FOR CDMA IP MBH
CDMANetworkDetails:
•604MLPPPprotectedbundlesoneach7750SR-7(AR)(withMC-APS)
•AmixofMLPPPgroups(bundles) –using1,2,4and8DS1smemberlinks
•1300totalDS1memberlinksconfiguredper7750SR-7(AR)
•1208MLPPPbundlesterminatedon7750SR12(BTS)
•2600DS1smemberlinksterminatedon7750SR12(BTS)
•604L3Interfacesper7750SR-7(AR)usedforMLPPPaggregationfromBTS
•604multiclassMLPPP(MC-4)QoSprofilesper7750SR-7(AR)
•32totalOC3linkssupportedwithMC-APSonthe7750SRs
•Trafficintegrityverificationofvoice,controltraffic,high-prioritydataandlow-prioritydata
2.1.1 VERIFICATION OF STATEFUL MLPPP RESILIENCY WITH MULTICHASSIS APS (MC-APS) IN CASE OF LINK, CARD AND NODE FAILURES
The testedAlcatel-Lucent CDMA/EVDO IPMBH architecture provides protection against link, card, SF/CPM,
and node failures. In accordance with explanation made to Isocore byAlcatel-Lucent, it was expected that
regardless of the network fault, the BTS would not require renegotiation of MLPPPsessions.Also, in order to
assure 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 MLPPPsessions (i.e., the tests were not
done on one individual MLPPPsessions running at the time).To validate the functionality and performance of
Alcatel-Lucent stateful MLPPPwith 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.
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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) SONETlink on
one node and a protection link on the adjacent neighborAR.The working and protection links were equally split
across the SUTs. Each of the 604 protected MLPPPbundle pairs were protected by MC-APS.The MC-APS was
configured to revert back to the working facility link one minute after a fault was cleared. Revert was used for this
event to maintain the location of the 32 OC3 working and protect circuits throughout the event and to demonstrate
the recovery times associated with revertive behavior.
During all failure scenarios the MLPPPstates 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 theAgilent N2X platform used
the same traffic profiles as the basic setup.Traffic loss was measured separately from the aggregation network
towards the BTS and from the BTS towards the aggregation network.
Figure2:Verificationof7750SRstatefulMLPPPandMC-APSimplementation
Table 2 shows the results of failure scenarios executed by command line interface (CLI), and table 3 shows results
of 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 conducted
to validate consistency of the measurements and worst case numbers are presented in the respective tables. Basic
traffic flows of control traffic, voice, high-priority data and low-priority data were used for all measurements.
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Table2:ResultssummarizingthestatefulMLPPPlinkrecoverythroughMC-APS(caseoflinkfailures)
RECOVERY TIMES FOR ADMINISTRATIVELY INDUCED FAILURES (USING MC-APS)
•SingleportfailurewithMC-APS–FailinglinkbetweenARandBTSwith21MLPPPbundles
•RecoverytimesfromMSCtoBTS–810ms
•RecoverytimesfromBTStoMSC–80ms
•SingleportfailurewithMC-APS–RecoveringlinkbetweenARandBTSwith21MLPPPbundles
•ReverttimesfromMSCtoBTS–403ms
•ReverttimesfromBTStoMSC–130ms
•FourportfailurewithMC-APS–FailinglinkonRANside(towardsBTS)with176MLPPPbundles
•RecoverytimesfromMSCtoBTS –917ms
•RecoverytimesfromBTStoMSC–210ms
•FourportfailurewithMC-APS–RecoveringlinkbetweenARandBTSwith176MLPPPbundles
•ReverttimesfromMSCtoBTS–967ms
•ReverttimesfromBTStoMSC–640ms
Multiple fiber cuts were performed by scripting the CLI shutdown of multiple ports simultaneously. Card failures
consisted of pulling out the 4-port OC3Any ServiceAny 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.TheAR (7750 SR-7) was rebooted
while the MLPPPstates were monitored at the BTS (7750 SR-12), and traffic loss was measured in each direction.
During the node-level failures, 16 OC3 SONETlinks were interrupted, including 8 working OC3 MC-APS links
carrying traffic from 302 base stations (MLPPPbundles) with 750 DS1 member links in total.
It is important to note that during all node-level failures, the entire end-to-end IPBH architecture was being tested,
including the L2 switch (7450 ESS-12), configured with spanning tree protocol (STP), which simulated the MSC
environment.
The worst-case node-level failure resulted in traffic loss for 2.07 seconds, which was well below the target
of 5 seconds — a requirement set forth by Isocore based on input from mobile providers.
Table3:ResultssummarizingtheMLPPPlinkrecoverythroughMC-APS(caseoffibercuts)
RECOVERY TIMES FOR PHYSICAL DISRUPTIONS INCLUDING FIBER CUTS AND CARD PULL-OUTS (USING MC-APS)
•Singlefiberpull-outwithMC-APS–failinglinkbetweenARandBTSwith21MLPPPbundles
•RecoverytimestowardsBTS–576ms
•RecoverytimestowardsMSC–100ms
•Singlefiberinsertion(linkup)withMC-APS–recoveringlinkbetweenARandBTSwith21MLPPPbundles
•ReverttimestowardsBTS –576ms
•ReverttimestowardsMSC–100ms
•Four(4)fiberpull-outs(MDApull-out)withMC-APS–failinglinkbetweenARandBTSwith176MLPPPbundles
•RecoverytimestowardsBTS –1800ms
•RecoverytimestowardsMSC–1000ms
•MDAinsertionwithMC-APS–recoveringlinkbetweenARandBTSwith176MLPPPbundles
•ReverttimestowardsBTS–588ms
•ReverttimestowardsMSC–270ms
•NodefailureonAR1(reboot)–302MLPPPbundles
•RecoverytimestowardsBTS –2072ms
•RecoverytimestowardsMSC–1635ms
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