asr5000/5500 platform and support for lte/epc...
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ASR5000/5500 platform and support for LTE/EPC network BRKSPM-2888
Aravind Balakrishnan
Network Consulting Engineer
© 2014 Cisco and/or its affiliates. All rights reserved. BRKSPM-2888 Cisco Public
Agenda
1. Evolution and Requirements for LTE
2. Functionality of E-UTRAN and EPC elements
3. EPS bearers and characteristics
4. End-to-End QoS and Policy Management
5. Call Flows
6. Integration of EPS into GERAN/UMTS
7. Inter-RAT Handovers
8. ASR 5x00 Service Offerings
9. Introduction to VoLTE
10.SaMOG – Accessing EPC via non-3GPP RAN
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What is LTE?
3GPP LTE is the name given to a project within the 3GPP to improve the UMTS mobile phone standard to cope with future technology evolutions
Evolution - LTE
Motivation
– User demand for higher data rates and QoS
– Cost reduction (CAPEX/OPEX)
– Avoid unnecessary fragmentation of technologies for paired and unpaired band operation
– Continuity of competitiveness for the future
Goals:
– Increase peak data rates while lowering costs and improving services
– Improve spectral efficiency and make use of new spectrum opportunities
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– Integration with other open standards
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Low latency
Mobility
Spectrum Flexibility
Coexistence and inter-working with 3GPP RAN
Although an evolution of UMTS, the LTE air interface is a completely new system
The architecture resulting from this work is called EPS and comprises E-UTRAN on the access side and EPC on the core side
Requirements for LTE
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Evolved Packet System
E-UTRAN consists of a collection of eNodeBs
The mobile packet core consists of 3 nodes – MME, SGW and PGW
The core nodes interact with supporting elements – HSS, PCRF, OCS etc.
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E-UTRAN
EPC Network
EPS Network
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E-UTRAN:
– Co-existence and interworking with 3GPP RAT
– E-UTRAN Terminals should be able to support measurement of, and handover from/to, both 3GPP UTRA and 3GPP GERAN systems
– The interruption time during a handover of real-time and non-real time services between E-UTRAN and UTRAN/GERAN be less than 300 msec and 500 msec respectively
EPC:
– Provide higher data rates, lower latency, high level of security and enhanced QoS
– Support a variety of different access systems (existing and future), ensuring mobility & service continuity between them
– Support access system selection based on a combination of operator policies, user preference and access network conditions
– Provide capabilities for co-existence with legacy systems and migration to the EPS
Requirements: E-UTRAN and EPC
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Functionality of E-UTRAN and EPC elements
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Performs ciphering/deciphering of the user plane (UP) data
IP header compression/decompression and encryption of user data stream
Routing of user plane data towards SGW
Scheduling and transmission of ETWS messages (originated from the MME)
Scheduling and transmission of broadcast information (originated from the MME or O&M)
User P
lane
Role of eNodeB
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Contro
l Pla
ne
Radio Resource Management
Measurement and measurement reporting configuration for mobility and scheduling
Scheduling and transmission of paging messages (originated from the MME)
Functionally, eNodeB acts as a layer 2 bridge between UE and the EPC
MME selection and load (re)balancing
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eNodeB: Protocol Stack, Interfaces
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Control Plane User Plane
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Role of MME
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NAS Signaling and security
Authentication and Authorization
Checking UEs against EIR database
Managing Subscription Profile
Mobility Management
Bearer management
Selection of SGW, PGW, MME and SGSN
Allocation of GUTIs to UEs
Roaming
Support for Single Radio VCC and CS Fallback
Support for SMS via SGs interface
Support for PWS message transmission
Lawful Interception of signaling traffic
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MME: Protocol Stack and Interfaces
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Control Plane
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Role of SGW
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Routing and forwarding
– DSCP marking based on bearer QCI
– Idle mode DL packet buffering and initiation of network triggered service request procedure
Bearer Binding & Event Reporting Function (BBERF)
Terminates interface towards the E-UTRAN
S5/S8 interface based on GTP or PMIP
Mobility anchor for Inter-eNodeB handover
Inter-3GPP handover (terminating S4)
Non-3GPP access
Lawful Intercept
Charging
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SGW: Protocol Stack and Interfaces
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Control Plane User Plane
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Per-user based packet filtering/inspection (by e.g. deep packet inspection)
SGi termination
DSCP marking based on QCI of EPS bearer
Lawful Interception
Role of PGW
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IP Anchor point
Accounting
Radius/Diameter based Authentication and Authorization
Act as PCEF
DHCP related functions
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PGW: Protocol Stack and Interfaces
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Control Plane User Plane
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Key LTE Identifiers
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IMSI – International Mobile Subscriber Identity
TAI – Tracing Area Identity
GUTI – Globally Unique Temporary Identity ECGI – E-UTRAN Cell Global Identifier
IMEI – International Mobile Station Equipment Identity
IMEISV – IMEI and Software Version Number
EPS Bearers and Characteristics
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EPS Bearer Service Architecture
There are three kinds of bearers in LTE:
– Radio bearer
– S1 bearer
– S5/S8 bearer
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EPS bearer and Bearer types
EPS bearer is a logical aggregate of one or more IP flows (aka SDF)
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All SDFs within a bearer receive same level of QoS
Bearers can be categorized based on QoS requirements
– Default Bearer
– Dedicated Bearer
TFTs at both UE and PGW are responsible for distributing SDFs between EPC bearers
Dedicated bearers are established when IP flows that require specific packet forwarding treatment are started
Dedicated bearers can be:
– Non-GBR
– GBR
Default bearers are always non-GBR bearers
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Characteristics of bearers
Non-GBR Bearer
– May have a MBR
– Has associated ARP and QCI
– Service must be prepared to experience congestion related packet loss
– Can remain established for long periods of time as transmission resources are not reserved
– Precedence of service dropping over service blocking in congestion situation
– Stay up (no reserved resources)
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GBR Bearer
– Specified GBR and MBR Note: In 3GPP Rel 8, MBR=GBR
– Has associated ARP and QCI
– Service will not experience congestion related packet loss (provided the user traffic is compliant to the agreed GBR QoS)
– GBR bearers are established on demand as transmission resources are allocated and reserved during the admission control function
– Precedence of service blocking over service dropping in congestion situations
– Inactivity timers are used to control air interface and S1 interface to free up resources
QoS and Policy Management
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PCRF: Policy Management
Multiple services, each with a different QoS requirement compete for radio and core resources
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Policy management is critical in three closely-related areas:
– Limiting network congestion
– Enhancing service quality
– Monetizing services
Policy management is carried out on bearers
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PCRF Rules
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QoS Concepts and Parameters
A bearer has 4 QoS parameters
– QCI – QoS Class identifier User Plane treatment
– ARP – Allocation Retention Priority Control Plane treatment
– GBR and MBR for GBR bearers Used for real time services only
– APN-AMBR and UE-AMBR for non-GBR bearers
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ARP is stored in the subscriber profile (HSS) on a per APN basis and consists of:
– Priority Level – Values 1 to 15
– Pre-emption Capability flag: Enable/Disable (applicable to the bearer that is being established)
– Pre-emption Vulnerability flag: Enable/Disable (applicable to bearers that is already established)
AMBR is stored in the HSS
– For non-GBR bearers only
– Used for rate capping
– APN-AMBR defined per subscriber and APN and known only to the gateway
– UE-AMBR defined per subscriber and known to both gateway and RAN
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QoS in Radio and Transport
QoS need to be maintained in Radio and transport domains
RRM QoS
– QoS Class differentiation via QCIs
– Rate capping via UE-AMBR
Transport QoS
– DSCP marking on IP layer
– Ethernet priority bits (IEEE 802.1p) and/or VLAN ID's (IEEE 802.1q) are used on Ethernet layer
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End-to-End QoS
LTE supports “end-to-end” QoS
Traffic Flow Template (TFT) consist of:
– Identifier of the packet filter
– Precedence of the packet filter
– Direction – UL/DL
– Filter (Eg: Pattern matching on IP 5-tuple, optional DPI)
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Standardized QCI characteristics
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Source: 3GPP TS 23.203
LTE Call Flows
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Initial LTE Attach – Slide 1/3
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Establish RRC connection
Initial Attach Request Download Auth vectors
Authentication Procedure
Agree on integrity and ciphering algorithms
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Initial LTE Attach – Slide 2/3
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Download UE subscription profile
Interact with policy control server
Interact with online charging server
Allocate PDN IP address and accept the connection
Based on UE subscription profile and local policy, initiate establishment of PDN connection
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Initial LTE Attach – Slide 3/3
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Allocate GUTI and accept the Attach
Notify SGW of the eNodeb FTEID
Update HSS with the name of the APN, PDN IP and PGW IP
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Detach from LTE
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Integration of EPS into existing GERAN/UMTS
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Initial overlay deployment
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Inter-RAT via Gn/Gp
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Mobility: LTE UTRAN/GERAN
Cell Reselection:
– LTE to UTRAN/GERAN – UE sends RAU
– UTRAN/GERAN to LTE – UE sends TAU
SRNS Relocation and Handover:
– LTE to 3G – Source eNodeB sends HO Required (Target RNC ID) to Source MME
– 3G to LTE – Source RNC sends Relocation Required (Target ID=RNC ID) to Source SGSN
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GUTI to P-TMSI mapping
The mapping of the GUTI shall be done to the combination of RAI of GERAN/UTRAN and the P-TMSI:
– E-UTRAN <MCC> maps to GERAN/UTRAN <MCC>
– E-UTRAN <MNC> maps to GERAN/UTRAN <MNC>
– E-UTRAN <MME Group ID> maps to GERAN/UTRAN <LAC>
– E-UTRAN <MME Code> maps to GERAN/UTRAN <RAC> and is also copied into the 8 most significant bits of the NRI field within the P-TMSI
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P-TMSI to GUTI mapping
The mapping of P-TMSI (TLLI) and RAI in GERAN/UTRAN to GUTI in E-UTRAN shall be performed as follows:
– GERAN/UTRAN <MCC> maps to E-UTRAN <MCC>
– GERAN/UTRAN <MNC> maps to E-UTRAN <MNC>
– GERAN/UTRAN <LAC> maps to E-UTRAN <MME Group ID>
– GERAN/UTRAN <RAC> maps into bit 23 and down to bit 16 of the M-TMSI
– The 8 most significant bits of GERAN/UTRAN <NRI> map to the MME code
– The P-TMSI signature is sent intact to the MME E-UTRAN <MNC> maps to GERAN/UTRAN <MNC>
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LTE to UMTS Handover – Slide 1/2
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Target SGSN retrieves the context of UE from source MME
Lets MSC know that the UE is no longer attached to this MME
Notifies the policy server of new RAT
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LTE to UMTS Handover – Slide 2/2
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Downloads the UE credentials
Accept the RAU Update the PDN connection with UMTS QoS
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UMTS to LTE Handover – Slide 1/2
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Target MME retrieves the context of UE from source SGSN
OI=0 and new PGW TEID makes SGW send MBR to PGW
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UMTS to LTE Handover – Slide 2/2
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Download UE LTE subscription
Update MSS that the UE is Attached to LTE
Update the bearer with LTE QoS
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Inter-RAT via S3/S4
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Cisco ASR 5x00 Service Offerings
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ASR 5x00 Series Product Evolution
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Services/Functionality Supported On ASR 5x00
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Cisco MME differentiation
Heuristic Paging
Signaling – Congestion Control, Load Rebalancing, Attach Rate Throttling, Diameter throttling on S6a
MSC selection using DNS and fallback to alternate MSC on failure to reach selected MSC
Operator CLI command to place one or more MSC servers in maintenance mode (from an Sv perspective)
Support for MSC server pooling for Sv interface
Dynamic GTP echo
Adaptive TAI
MME Restoration
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Cisco SGW differentiation
Intelligent paging for ISR
DDN throttling for Pre-Rel 10 MMEs
LIPA optimizations
Traffic policing
802.1p marking in addition to DSCP marking
ICSR – Inter-Chassis Session Recovery
Dynamic GTP echo
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Cisco PGW differentiation
Virtual APN
Local policy for Gx and Gy
Modular P2P detection, DPI, NAT and Firewall
Throttling – GTP, Gx and Gy
Overcharging protection for 3G and 4G
SAE-GW – Collocated SGW/PGW with increased capacity
802.1p and MPLS experimental bits marking
ICSR – Inter-Chassis Session Redundancy
ICSR/SR enhancements for VoLTE
GTP based S2a and S2b
NEMO support
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ASR 5000 EPC Service Configuration
MME+SGW+PGW
MME+SGW and PGW
MME and SAE-GW
MME, SGW and PGW
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MME
+
SGW
+
PGW
MME
+
SGW
PGW
SAE-GW MME PGW MME SGW
VoLTE
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Methods to deliver Voice and SMS
VoLGA – Voice over LTE Generic Access
CSFB – Circuit Switch Fall Back
VoLTE – Voice over LTE
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VoLTE – Voice over LTE
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SIP Call Origination and Setup
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SIP Call Disconnect
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Mobile Offloading
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Mobile Offloading
Mobile data offloading is the use of complementary, cheaper and more localized network technologies for delivering data originally targeted for cellular networks
Offloading reflects the carriers desire to strike a balance between encouraging more data usage, while easing traffic from airwaves
WiFi and femtocell technologies are the primary technologies used by the industry
EPS supports the use of non-3GPP IP access networks to access the EPC
WiFi could be trusted or untrusted
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SaMOG – S2a Mobility Over GTPv2
SaMOG provides EPC Access over trusted WLAN
Why SaMOG?
– Efficient use of spectrum
– Network based mobility
– Seamless mobility between 3GPP and WLAN for EPS services with IP address preservation
– Non-seamless WLAN offload
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SaMOG Components and Reference Model
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SaMOG Components SaMOG Reference Model
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STa Reference Point
TWAN provides the following information to 3GPP AAA server:
– An indication on whether the TWAN supports S2a, non-seamless offload or both
– The SSID selected by the UE to access the TWAN
3GPP AAA server provides TWAN with:
– Whether access to EPC is allowed for the UE on the TWAN
– Default APN used for EPC access
– Subscriber MSISDN
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TWAN: Protocol Stack
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Control Plane for Tunnel Mgmt. User Plane
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Network Architecture
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SaMOG: 3GPP Rel 11
The key requirement of 3GPP Rel 11 SaMOG is to keep standard Rel 11 UEs unmodified with respect to Rel 10 or Pre-Rel 10 UEs
The above requirement leads to several limitations:
– Lack of IP address preservation (no IP mobility)
– Terminal cannot indicate an APN when connecting to the WLAN (the terminal is connected to default APN pre-configured on the TWAG or in the service profile on AAA/HSS)
– Terminal cannot establish multiple connections to multiple PDNs
– Terminal cannot access simultaneously resources in the WLAN and the EPC
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SaMOG: 3GPP Rel 12
The restriction on modification to the UE imposed by 3GPP Rel 12 of SaMOG definition has been removed
With the removal of the above restriction the following additional functionalities becomes possible:
– Multiple simultaneous PDN connections including concurrent connections via 3GPP access and over WLAN
– PDN Connectivity to EPC over Trusted WLAN concurrent with non-seamless WLAN offload (NWSO)
– IP address preservation for a single PDN connection
– UE is capable of signaling the requested APN over Trusted WLAN
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Initial Attach in WLAN on GTP S2a – Slide 1/2
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Initial Attach in WLAN on GTP S2a – Slide 2/2 Scenario A
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Initial Attach in WLAN on GTP S2a – Slide 2/2 Scenario B
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Reference
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Call to Action…
Get hands-on experience with the following Walk-in Labs
MIL1413745: ASR5K/ASR5500 CLI and Tools
Meet the Engineer
Jan 29, 2014 – 4:30 pm to 6:00 pm
Jan 30, 2014 – 4:00 pm to 6:00 pm…
Discuss your project’s challenges at the Technical Solutions Clinics
Attend one of the Lunch Time Table Topics, held in the main Catering Hall
Recommended Reading: For reading material and further resources for this session, please visit www.pearson-books.com/CLMilan2014
CL365 -Visit us online after the event for updated PDFs and on-demand session videos. www.CiscoLiveEU.com
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Call to Action…
Visit the World of Solutions:-
Cisco Campus
Walk-in Labs MIL1413745: ASR5K/ASR5500 CLI and Tools
Technical Solutions Clinics
Meet the Engineer Jan 29, 2014 – 4:30 pm to 6:00 pm
Jan 30, 2014 – 4:00 pm to 6:00 pm…
Lunch Time Table Topics, held in the main Catering Hall
Recommended Reading: For reading material and further resources for this session, please visit www.pearson-books.com/CLMilan2014
72
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