RNC Whitepaper

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WHITE PAPER

HSS ProductsEnabling

RNC DevelopmentA White Paper

RNC Development

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COPYRIGHT INFORMATION

© Copyright Hughes Software Systems, 2004

All information included in this document is under a license agreement. This publication and its contentsare proprietary to Hughes Software Systems. No part of this publication may be reproduced in any form orby any means without the written permission of

Hughes Software SystemsPlot 31, Electronic City,Sector 18, Gurgaon 122 015, INDIATel: +91-124-2346666, 2455555Fax: +91-124-2455100, 2455101Website: www.hssworld.comE-mail: [email protected]

TRADEMARKS

All the brand names and other products or services mentioned in this document are identified by thetrademarks or service marks of their respective owners.

DISCLAIMER

The information in this document is subject to change without notice and should not be construed ascommitment by Hughes Software Systems. Hughes Software Systems assumes no responsibility ormakes no warranties for any errors that may appear in this document and disclaims any implied warrantyof merchantability or fitness for a particular purpose.

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C o n t e nt s

1 . I n t r o d u c t i o n 52 . Sys t e m O ve r v i e w 6

2.1. RNC Position in WCDMA Network 62.2. RNC Functions 6RNC Internal View 72.3. RNC Interfaces 82.4. RNC Application 92.5. System Requirements for RNC 9

3 . HSS O f fe r i ngs 1 03.1. Interface Software 103.2. Control Plane Stacks 103.3. User Plane stacks 103.4. Features of HSS Control Plane stacks: 103.5. Features of HSS User Plane stacks: 12

4 . H S S Pr o d u c t s F e a t u r e s 1 44.1. High Performance 144.2. Reliability 144.3. Portable 144.4. Uniform Management Interface 144.5. Compatibility and Interoperability 154.6. Standards Compliance 154.7. HSS Stacks Performance Analysis – A case study 16

5 . Co n c l u s i o n 1 7

RNC Development

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F i g ur es

F i g u r e 1 : WCD MA N e t w o r k A r c h i t e c t u r e . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6F i g u r e 2 - R N C I n t er n a l V i e w f o r A TM Tr an s p o r t . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7F i g u r e 3 : RN C I n t e r n a l V i e w f o r I P Tr an s p o r t . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

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1. Introduction3G technology supports a wide range of

applications with varying quality of service profiles.

The emerging role of Internet in the sphere of

communications has also contributed to the evolutionof 3G network.

3G networks are logically divided into a Radio

Access Network (RAN) and a Core Network (CN),connected via an open interface. The RAN consists of

the physical entities, Radio Network Controller (RNC)

and Node B, which manage the resources of theaccess network. RAN facilitates and supports the

interface between the User and the Core Network.

A carrier-grade switching system such as RNCtypically consists of the following three components:

� A hardware platform

� Interface software to implement the various

control/user plane protocols specified by various

standardization bodies.

� RNC Application

RNC Application

Interface SoftwareProtocol Stacks by 3GPP, ITU-T, IETF etc.

High-end Hardware Platform

The hardware platform typically is a chassis

comprising multiple line cards for terminating network

interfaces. It also consists of processor cards forhosting the various control/user plane stacks and RNC

Application.

This platform is characterized by high data

processing capabilities, which facilitate basic 3G

services such as high-speed data access and high-resolution video.

The Interface software consists of a set ofControl Plane and User Plane protocol stacks. It

handles the syntax and protocol details specified in

various 3GPP, ITU-T, IETF specifications. However,the RNC Application controls the decision-making or

Resource Management.

The RNC Application is responsible formanaging the resources and coordinating the various

interfaces. As it uses the interface software, it does

not have to deal with syntax and protocol details.

This paper presents an overview of the RNC, its

interfaces with various network nodes and typicalsystem requirements of an RNC. It also includes a

brief description of the software components provided

by HSS and their features.

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2. System OverviewThis section describes the network positioning,

basic functions and different interfaces of RNC in a

Wideband Code Division Multiple Access (WCDMA)

network. It also outlines the performance and networkdeployment requirements of a typical carrier grade

RNC. Figure 1 depicts the position of RNC in a typical

WCDMA Network Architecture.

SGSN

Core Network

Iu_PS

GsIu_CS

VLRMSC

B

RNC

Node B

Node BAccess Network

RNCIur

Iub

Iub

U u

U u

Figure 1: WCDMA Network Architecture

2.1. RNC Position in WCDMA NetworkAs depicted in Figure 1, the RNC is connected to

Node B via an Iub interface. A single RNC may beconnected to multiple Node Bs. Unlike the GSM

network, an RNC in the UMTS network is connected to

other RNCs via an Iur interface. The RNC is connectedto Core Network via an Iu interface. The Iu interface

towards the Packet-Switched (PS) domain of the core

network is called Iu-PS, and the Iu interface towardsthe Circuit-Switched (CS) domain is called Iu-CS.

2.2. RNC FunctionsA typical RNC performs the following functions:

� Admission Control

� Handover Control

� Load Control

� Power Control

� Transfer of User Data

� Overall system access control

� Radio channel ciphering and deciphering

� Integrity protection

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� Functions related to mobility such as Handover

and relocation

� Radio Resource Management and control

RNC Internal ViewFigure 2 and Figure 3 below depicts the modular

structure of an RNC for ATM transport and IP

transport respectively and the interaction of various

modules with each other.

RNC

APPLICATION

NBAP

SAAL - UNI

AAL5

ATM

ALCAP

AAL2

IubFP

RLC

PDCP

Iub-FP

MAC

RRC RANAP

SAAL – NNI / SCTP

AAL5 / IPOA

ALCAP

MTP3 – B / M3UA (# 2)

AAL2

Iu UP

GTP(# 1)

AAL2

Iur FP RNSAP

SAAL – NNI / SCTP

AAL5 / IPOA

ALCAP

MTP3 – B / M3UA

SCCP - B

ATM

ATM

AAL5

Iu User Plane

Iu ControlPlane

Uu Control PlaneUu User Plane

Iur User PlaneIur Control Plane

TransportNetwork ControlPlane Iub User PlaneIub Control Plane

IurIub

Uu

#1: GTP will exist in the case of Iu-PS#2: Iu-CS uses MTP3 and SAAL for Signaling Transport Plane

Iu-PS can use either MTP3/SAAL or M3UA/SCTP for Signaling Transport Plane

TransportNetwork ControlPlane

Transport NetworkControl Plane

IPOA

RLC

MAC

BMC

SCCP - B

Iu-PSIu-CS

Figure 2- RNC Internal View for ATM Transport

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Iu Control PlaneIu User Plane

Uu Control PlaneUu User Plane

Iur Control PlaneIur User Plane

Iub Control PlaneTransport NetworkControl Plane

Iub User Plane

DATA LINK

IP

SCTP

M3UA

SCCP

RANAP

UDP

IU UP

RTP/ GTPURTCP

DATA LINK

IP

SCTP

M3UA

SCCP

RNSAP

UDP

IUR FP

DATA LINK

IP

SCTP

NBAP

UDP

IUB FPTBD

Layer 1

MAC

RLC

RRCBMCPDCP

RNC

APPLICATION

RTP/RTCP

IubIur

UuIu-CS Iu-PS

Figure 3: RNC Internal View for IP Transport

Note: Transport Network Control Plane has not been frozen in the specifications.

2.3. RNC Interfaces� Iu Interface

The Iu interface provides protocol termination forthe interface between RNC and the Serving GPRSSupport Node (SGSN) or Mobile Station Controller

(MSC). This functionality is for packet switched/circuitswitched capabilities. The Iu interface facilitates

procedures for services such as Radio Access Bearer

Assignment/Release, Paging, and SRNC Relocation.

It provides a transparent path for the Network AccessServer (NAS) signaling messages between the User

Equipment (UE) and CN. It also transports User data

between CN and RNC.

� Iub Interface

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The Iub interface provides protocol terminationfor the interface between RNC and Node B. It

provides a set of functions, which includes Cell

Configuration Management, Radio LinkManagement/Supervision, System Information

Management and Common Transport Channel

Management. It also relays User data between RNCand Node B.

� Iur Interface

The Iur interface provides protocol terminationfor the interface between Drift RNC and Serving RNC.

It facilitates procedures for services such as Radio

Link Management/Supervision, Physical ChannelReconfiguration, Paging, and Common Transport

Channel Management. It also transports User data

between two RNCs.

� Uu Interface

The Uu interface provides protocol termination forthe interface between UMTS Terrestrial Radio AccessNetwork (UTRAN) and UE. It facilitates procedures for

services such as RRC Connection and Radio BearerManagement, Mobility Management, and

Measurements. It also facilitates procedures for

Paging, Authentication and Ciphering.

2.4. RNC Application

The RNC Application interacts with multiple

interfaces for the overall control of the RNC. It is also

responsible for all decision making. It also performsvarious other control functions such as Admission

control, Power Control, Mobility Management.

2.5. System Requirements for RNC� Performance

Based on market research analysis, it can beconcluded that a typical medium sized field deployable

RNC may support up to 256 Node Bs. It may supportapproximately 64K subscribers.

International standards define six service usage

environments of 3G services. The network planning isaccomplished in such a way so as to facilitate an

equal distribution of these usage sets. The mean

traffic intensity can be statistically estimated as 1.15Busy Hour Call Attempts (BHCA) per user. Therefore,

for an average of 64k subscribers, a typical RNC may

be required to support 74k BHCA. It should alsosupport peek data rate of 20 Mbps for CS domain and

200 Mbps in downlink/700 Mbps in uplink for PS

domain.

� Compatibility and Inter-operability

The RNC should be inter-operable with networknodes and User Equipment compliant with different

UMTS releases.

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3. HSS OfferingsThis section describes the HSS 3G offerings,

which can enable the OEMs to reduce time-to-market

for RNC.

3.1. Interface SoftwareHSS has developed the control plane and user

plane stacks required for building an RNC.

Stacks for various interfaces of RNC - Iu, Iub, Iur and

Uu interface are available as ready-to-use andplatform-independent building blocks.

These interfaces are divided into various planes,

Control Plane and User Plane. A brief description ofHSS Stacks for various planes is given below.

3.2. Control Plane Stacks

� Radio Access Network Application Protocol

(RANAP) – for Iu Interface

� RNSAP – for Iur interface

� Node B Application protocol (NBAP)- for

Iub Interface

� Radio Resource Control (RRC) - for Uu

interface

� Signaling Connections Control part (SCCP)

� Message Transfer Level Part 3 (MTP3)-B

/SAAL-NNI for the ATM transport option

� M3UA/Simple Control Transmission

Protocol (SCTP) for the IP transport option

� ALCAP

� SAAL-UNI(for ATM transport option) – for

Iub Interface

� Radio Link Control (RLC), Media Access

Control (MAC)- for Uu interface

3.3. User Plane stacks

� Iu-UP

� Iub-FP

� Iur-FP

� GTP-U

� PDCP

3.4. Features of HSS Control Planestacks:

� RANAP Stack Features/Functions:

� Supports Release 5, Release 4 and Release

99

� Interacts with both 3G SGSN (PS Domain )

and 3G MSC (CS Domain)

� Provides Iu Signaling Connection

Management, where connections are

maintained on a per domain/per UE

basis.

� Facilitates a set of general UTRAN

procedures from the CN

� Supports Paging Notification where it

also implements Paging Coordination.

� Supports SRNS Relocation in conjunction

with the RNC Application.

� Provides SCCP Connection Management

� Provides Redundancy Support

� RNSAP Stack Features/Functions:


99

� Supports RNSAP Common, Dedicated,

Mobility, and Global procedures for both

SRNC and DRNC

� Provides SCCP Connection Management


11

� NBAP Stack Features/Functions:


99

� Supports NBAP Common and Dedicated

procedures


� RRC Stack Features/Functions:

� Supports Release 4 and Release 99

� Configures RLC/MAC entities

� Performs the mobility functions of the RRC

connection

� Performs paging and notification

� Supports UE measurement reporting and

reporting control

� Controls ciphering configuration of RLC/MAC

� Performs integrity protection and integrity

check of RRC messages

� Supports parallel execution of multiple

transactions between UTRAN and UE

� Broadcasts information related to the access

stratum and non-access stratum. A separate

SIB Encoder Library, which is used at RNC

and Node B, supports this function.

� RLC Stack Features/Functions:


99

� Supports Segmentation and Re-assembly

� Supports Concatenation and Padding

� Supports the transfer of User Data in

AM/UM/TM mode

� Provides Error Correction and In-Sequence

Delivery

� Provides Flow Control

� Provides Ciphering support for AM/UM Mode

RBs

� MAC Stack Features/Functions


99

� Supports mapping logical to transport

channels

� Provides selection of appropriate Transport

Format for each Transport Channel (TFCI

Selection)

� Supports identification of UEs on common

transport channels

� Supports multiplexing / de-multiplexing of

higher layer PDUs into / from transport block

sets

� Provides traffic volume monitoring

� Provides dynamic transport channel type

switching

� Provides Ciphering support for TM Mode RBs

� For message transactions between the RLC,

MAC and FP protocol entities, zero buffer

copy mechanism is used.

� SCCP Stack Features/Functions:

� Class 0, 2 Services

� Segmentation and Re-assembly

� Redundancy Support

� Distribution Support

� MTP3-B Stack Features/Functions:

� Provides Message routing, discrimination and

distribution

� Provides Signaling Link Management

� Supports Load Sharing


� Provides Distribution Support

� M3UA Stack Features/Functions:

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� Transport of SS7 MTP 3 user signaling over

IP using SCTP

� SCTP Stack Features/Functions:

� Reliable transport of signaling on top of an

unreliable routing-based packet network

such as IP.

� SAAL-NNI Stack Features/Functions:

� Supports SAAL connection management

� Provides Link status and remote processor

status mechanisms

� Provides reliable exchange of signaling

information

� Supports signaling link error monitoring

� ALCAP(Q.2630, Q.2150) Stack

Features/Functions:

� Establishing and releasing end-to-end on-

demand AAL2 connections

� Signaling conversion for MTP-3

� SAAL-UNI Stack Features/Functions:

� Establishment and release of SAAL

connections for assured transfer of data

� Signaling link error monitoring

� Flow control

3.5. Features of HSS User Planestacks:

� GTP-U Stack Features/Functions:


99

� Provides user data transmission

� Provides tunneling of multi-protocol data

packets

� Iu-UP Stack Features/Functions:


99

� Provides RNC Flow Control, Error Detection

or Cyclic Redundancy Check (CRC)

� Transport of AMR data streams of various

data bit rates

� Rate matching of AMR data

� Iur FP Stack Features/Functions:


99

� Supports transport of MAC-C/SH SDUs

between SRNC and DRNC every 10ms

� Supports Flow Control of FACH Data Streams

� Multiplexes several UEs on one Transport

Bearer

� Provides CRC Check

� Provides Error Detection (CRC Calculation)

� Provides transport of UL and DL DCH Data

� Supports Set of Coordinated DCHs on the

same Transport Bearer

� Iub FP Stack Features/Functions:


99

� Node Synchronization

� Transport Channel Synchronization

� Transport of TBS across Iub interface in

Uplink and Downlink Transport channels

between Node B- CRNC (for common

channels) and between Node B - SRNC

within each TTI of 10ms/20ms/40ms/80ms

� Error Detection (CRC Calculation)

� Transport of UL and DL DCH Data

� Supports set of Coordinated DCHs on the

same Transport Bearer

� PDCP Stack Features/Functions:

13


99

� Compression of redundant network PDU

header information

� Transfer of packet data protocol user data

using RLC services

� Sequence numbers for radio bearers to

support ‘loss-less’ SRNS relocation

� Flexible internal memory allocation (dynamic

or static) to minimise memory usage

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4. HSS Products FeaturesHSS stacks are platform-independent (ease of

porting) and characterized by high performance, high

throughput and high availability. They also provide

high scalability. This has been made possible bymodular design and porting library.

4.1. High PerformanceThe performance aspect of RNC is related to its

ability to meet the call/session setup delays, timing

requirements for providing the required QoS to the

connected UEs. This requires a high throughput,which has been achieved by implementing the

following design principles.

� Efficient memory management

� Optimized data structures

� Efficient search algorithms

An efficient distribution framework is also

required to facilitate high throughput rates. Trafficmust be distributed across multiple instances, thereby

increasing the traffic handling capacity of nodes and

providing a unified view of the external network andstack users.

HSS has established a strategy for the distribution

of its protocol stacks, which can be tailored accordingto customer needs.

4.2. ReliabilityCarrier grade solutions require very high

availability, of the order of five nines. This is achieved

by ensuring that there are no single points of failure

in the system. HSS has prior experience in developingcarrier grade solutions and has a ‘High Availability

Framework’, which has been used internally for

various HSS products and customer solutions toimplement high availability systems. High Availability

Platform support has been provided for most of the

Application Protocol stacks.

4.3. PortableHSS stacks use a virtual environment known as

the Common Stacks Porting Library (CSPL), which

provide a uniform OS service interface for interactingwith the Operating System. CSPL shields the HSS

stacks from the Operating System function calls and

instead provides consistent function interface,irrespective of the OS used. CSPL maps these function

calls to the OS function calls. Thus, all stack

components become available for a particular OS byporting the CSPL to the OS.

The advantages of using CSPL are:

� Uniform OS Services interface for all stacks

� Standardizes porting to new operating systems

� Readymade ports for popular operating systems:

� Solaris

� Linux

� VxWorks

� Win32

� Facilitates integration of a stack entity with other

entities

� CSPL also provides the following services to the

stacks:

� Memory Management for Contexts and

Messages

� Scheduling

� Timer Management

� Messaging

4.4. Uniform Management InterfaceHSS protocol stacks provide an interface with a

Management Entity. This interface is used for

initialization, provisioning of the stacks, managingtimers, debug trace levels, error levels and statistics

reporting required for the operation, administration

and maintenance of protocol stacks. These areexplained below in detail.

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4.4.1. Provisioning

The protocol stacks are initialized and provisionedthrough the Management Interface. The static

information is provided to the stacks in the

provisioning API. Examples of static information arethe number of nodes connected and the point codes.

Parameters that tune the run-time-memory

requirements of the stack are provided along with thisinformation. For example, the number of UE contexts

supported by the stack is configured through this API.

The operator-specific values for Procedure Retries andTimer Values are also provided.

4.4.2. Debugging and Tracing

The stacks provide for multiple trace levels. Thetracing support is controlled by a compile time option

that excludes/includes tracing facilities. After the

tracing facilities are included through the compile timeoption, the run-time control of tracing is achieved

through:

� Trace flags which specify the

module/functionality/control flow for which the

tracing information is required.

� Trace levels that specify the details of the tracing

information required.

By selecting the right trace levels for varioustrace flags, the operation of the stacks can be

debugged effectively. APIs are provided to set the

trace level of any trace flag and to retrieve the currenttrace level.

4.4.3. Statistics Collection

APIs are provided to collect various statistics in

the RNC protocol stacks. A message-based interface isprovided for the initialization and collection of various

statistics for events occurring in the stack layer such

as reception of peer messages. This facility can beexcluded at compile time.

The following statistics classes are collected:

� Protocol Statistics

� Connection Data Statistics

� Error Statistics

Statistics can be used by the RNC developer to

provide diagnostic for O&M purposes.

4.4.4. Error Handling

This module contains the functions for error

processing. Any occurrence of an error results in a callto a function in this module. This code is organized in

a separate module to allow porting by the user, to

enhance system diagnostics and customize the errorhandling. Error Handling is a compile time option that

can be included or excluded using a compile time flag.

4.5. Compatibility and InteroperabilityHSS has delivered RNC protocol stacks to various

customers, where nodes compliant to different UMTS

releases have inter-operated with each other. TheRNC protocol stacks have been inter-operated with

network nodes of various OEMs and have been tested

against the standard test tools. It reduces the risk ofinter-operability against other vendor equipment.

4.6. Standards ComplianceHSS products conform to the international

standards published by 3GPP, ETSI and ITU-T. HSS is

committed towards the continued conformance of its

products to these standards as they evolve in the nearfuture.

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4.7. HSS Stacks PerformanceAnalysis – A case studyPerformance analysis of HSS control plane stacks

was done on a COTS reference platform. The

reference platform was PowerPC single-processor-

based. It had an:

� OC3/STM1 Communications controller,

� 400 MHz clock,

� 100 MHz system bus

� 1 MB L2 (secondary cache) cache and

� on-chip D/I cache of 32 KB.

The messages used in the calculation covered all

the important messages required in a typical call set-

up scenario.

Uu Interface: RRC Messages at Uu interface

required for Connection Setup

� RRC Connection Request

� RRC Connection Setup

� RRC Connection Setup Complete

� Initial Direct Transfer

� RRC Security Mode

Connection setup/hr (at 10 % CPU) = 115K

Iub Interface: NBAP messages at Iub interfacerequired for Connection Setup

� Radio Link Setup Request

� Radio Link Setup Complete


Iu Interface: RANAP Messages required for

Connection Setup

� Initial UE message

� Security Mode Command

� Direct Transfer

� Radio Access Bearer (RAB) Assignment Request

� RAB Assignment Response


Considering the connection release time and

unsuccessful call attempts, and extrapolating the

afore-mentioned connection setup data, BHCA of150K (from the signaling message-processing

perspective) can be achieved using HSS stacks on a

single processor-based platform.

HSS has also done a study of standard Network

Processors available. Based on this study and

extrapolating the results, it can be said that HSS userplane protocol stacks, when ported on Network

Processor should be able to meet the data throughput

requirements.

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5. ConclusionThe implementation of the HSS Interface

software facilitates the development of the RNCApplication and reduces the time-to-market

considerably. The Interface software handles the

protocol details, thereby allowing the user to focus onthe core functionality of RNC Application.

It meets all the carrier grade requirements suchas high availability, high throughput and

interoperability. The interface software can help

immensely in the development of a typical RNC withina short span of time.

E-mail: [email protected]

HSS USAGermantowTel: +1-240BostonTel: +1-617DallasTel: +1-972

HSS USASan JoseTel: +1-408Los AngeleTel: +1-323

Plot 31, Tel: +91-124

The comprehensive set of software building blocksfrom HSS consists of both protocol stacks andIntegrated Interfaces for the 3G/UMTS Network Nodes

Integrated Interfaces StacksUu RRC,RLC,MAC,FP, PDCPIu-PS RANAP, SIGTRANIu-CS GTPIub NBAP, SAAL, ALCAPIur RNSAP

Mo

Hughes Software SystemsElectronic City, Sector 18, Gurgaon 122 015, India-2346666, 2455555 Fax: +91-124-2455100, 2455101

om

, Ean

-45

-54

-51

, W

-43s

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Hughes Software Systems is a keysupplier of communication

technologies for Voice over Packet,Intelligent Networks and High-speedobile Networks, and is fully focussedn the needs of its customers to build

Next Generation Networks.

www.hssworld.com

st Coast

3-2498

7-6377

7-3345

est Coast

6-4604

1-0032; 571-0114

HSS EuropeMilton Keynes, UKTel: +44-1908-221122GermanyTel: +49-6155-844-274FinlandTel: +358 40 8290977

HSS IndiaGurgaonTel: +91-124-2455555; 2346666BangaloreTel: +91-80-2286390

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