digital network lecturer4
TRANSCRIPT
DIT
Dar es Salaam institute of Technology (DIT)
ETU 08102
Digital Networks
Ally, J
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IP Multimedia Subsystem (IMS) Basics
Voice and Video over IP
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Voice and Video over IP After some early resistance, telecom
companies have embraced VoIP The VoIP standards war is over
The winner: Session Initiation Protocol (SIP) What if?
An architecture was designed to support services and multiple networks
The media is not just voice, but multi-media SIP signaling used throughout
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What is IMS? IMS is an architecture, it is not a protocol.
Open-systems architecture that supports a range of IP-based services over both Private and Carrier networks, employing both wireless and fixed access technologies.
IMS is defined by 3GPP.
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IMS Basic Concept IMS is an architecture that solves the continuing demands and
frustrations of users and enterprises. The ultimate goal of the architecture is to define a model that
separates the services offered by fixed-line (traditional telecom), mobile (traditional cellular), and converged service providers (cable companies and others who provide triple-play — voice, video, and data services) from the access networks used to receive those services.
For instance, a classic example would be the ability of a mobile cellular phone to switch to WiFi VoIP (mid-call) when it discovers a valid network to use.
In this scenario, your mobile phone would dynamically move your existing call over the cellular network to a valid WiFi network (for example, your home wireless network) when you came into range, saving your cellular airtime and providing additional bandwidth for data communications.
IMS, when fully deployed, will enable you to choose a Service Provider (SP) not by the quality or ubiquity of their network, but by the services they offer.
The “network,” or how you connect to those services, will become irrelevant.
AccessNetwork
OtherNetworks
Web PortalWeb Portal
ApplicationApplicationServersServers
Session Session ControlControl
CentralizedCentralizedDatabasesDatabases
Media Media Control &Control &GatewaysGateways
MediaMediaServerServer
AccessLayer
Session ControlLayer
Application Layer
Open Industry Standard Support for a Variety of
Applications:• Speed Applications to market
Common Session Control Element to Provide Service Interworking
• Predictable interactions between multiple services
Common Subscriber Database with Open
Interfaces
Service Consistency Across Wireless, Wireline and VoIP Endpoints:
•Retain ownership of the subscriber and their services
•Ability to provide differentiated services
Distributed Session Control• IMS flexibility and scalability reduce OPEX• Support mobility/portability
Common support for CoS, QoS, security,
scalability, reliability, and performance
Common OAM&P Environment• Ease integration into OSS/BSS/NMS
Common Common OAM&P,Billing, OAM&P,Billing,
etc.etc.
Capable of Interworking with the PSTN (i.e. legacy IN-
based services)
IP Multimedia Subsystem (IMS) - Key Attributes
RNCMSC(Server)
SGSNGGSN
CNCNMGW
BSC
UMTS/GPRSUMTS/GPRS
WLANWLAN
CorporateCorporate
P-CSCF
I-CSCFMRF
MGW
MGCF
IMSIMS
S-CSCF
SIP ApplicationServersSIP Application
ServersHSS
CDMA 2000CDMA 2000DSL/Cable ModemDSL/Cable Modem
DSLAM/CMTS
IMS Access Network Independence
Clie
nts
Clie
nts
Dev
ices
Dev
ices
Acc
ess
Acc
ess
Tran
spor
tTr
ansp
ort
Sess
ion
Sess
ion
Con
trol
Con
trol
App
licat
ions
App
licat
ions
Managed Core IP Network Media GWSignaling GW
MRFCMRFCCSCFCSCF
Service BrokerService BrokerHSSHSS
Pres.Data
Loc.Data
SubsData
Micro BillingMicro BillingIntegrated Integrated Pre-paid & Pre-paid & PostpaidPostpaid
AAAGroupLists
MediaServer
POTSphone
GGSNPDSN
MSCCellular
AccessPoint
WiFi/802.11x Local Loop
VoIPhandset
Ckt-PBXIP-PBX
IP-phonesISDN-phones
IP-phones
DSL/CableIP LAN
WirelessRouter Base
Station
5ESS
(IP-Centrex)
Office/Hotel HotspotHome On the Road Home/Office
Dual-modeWiFi phoneSoft-phones
PSTN SS7
SIP Clients
Ckthandset
Multiple user interfaces with common look and feel
Other Clients
IMS Converged Communications Services Vision
LucentLucentPresencePresence
ServerServer
ActiveActivePhonebookPhonebook
ServerServer
BroadSoftBroadSoftTelephonyTelephony
ServerServer
AnyPathAnyPathUnified Unified
Messaging Messaging SvrSvr
OtherOtherApp Servers App Servers (PTT, IM etc.)(PTT, IM etc.)
EBS Web PortalEBS Web Portal
Parlay/OSAParlay/OSAMediationMediation
Gateway (ISG)Gateway (ISG) Network Operations, Applications Mgt, Subscriber registration/
authorization
PresencePresenceServersServers
TelephonyTelephonyServersServers
UnifiedUnifiedMessagingMessaging
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Roles of Standards Bodies for IMS
ServicesServices
Open Mobile AllianceOpen Mobile Alliance Defining IMS services
The Parlay GroupThe Parlay Group Integral to IMS architecture, define standard API frameworks
Mobile Mobile ArchitectureArchitecture
3rd Generation 3rd Generation Partnership ProjectPartnership Project
Define IMS network elements and infrastructure
Architecture Architecture for Wirelinefor Wireline
ETSI TISPAN - Merger of ETSI TISPAN - Merger of TIPHON (VoIP) and SPAN TIPHON (VoIP) and SPAN (Fixed)(Fixed)
Defines SIP, SDP and other protocols underlying IMSIMS is driving some of the work in IETF
CornerstoneCornerstone Internet Engineering Internet Engineering Task ForceTask Force
Agreement on reuse of 3GPP IMS in comprehensive NGN plans
IMS Building Blocks1. An all-IP Core Network (CN)
2. An all-IP Radio Access network (RAN)
3. Multimedia call control based on SIP
4. Quality of Service (QoS) support for IP
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3GPP IMS Network Elements
HSSHSS
I-CSCFI-CSCF S-S-CSCFCSCF
VisitedNetwork
Home Network
SIP
ASASASASASAS
Home Subscriber Server• Centralized DB• HLR successor• User profile• Filter criteria (sent to S-CSCF)
• Which applications• Which conditions
Application Servers• Push-to-talk• Instant messaging• Telephony AS• 3rd party or Lucent
P-P-CSCFCSCF
BackboneBackbonePacketPacket
NetworkNetwork
AccessAccess
MGCFMGCF
MGWMGWPSTNPSTN
H.248ISUP
BGCFBGCF
SIP
SIPSIP
SS7SS7
SIP
SIP
SIP
SIP
SIPSIPSIP
Diameter
RTP TDM
RTPRTP
Call SessionControl Function• SIP registration • SIP session setup
MRFMRF
Media GatewayControl Function• Interfaces to PSTN/PLMN by
• Converting SIP <-> ISUP• Interworking RTP to circuit
• H.248 control of MGW
Breakout Gateway Control Function• Selects network (MGCF or other BGCF) in which PSTN/ PLMN breakout is to occur
Media Resource Function Pooling of Media servers
Proxy CSCF• 1st contact point for UE• QoS• Routes to I-CSCF
Interrogating CSCF• Entry point for incoming calls• Determines S-CSCF for Subscribers• Hides network topology
Serving CSCF• Registrar• Session control• Application Interface
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Brief Explanation IMS Network Elements The Call Session Control Function (CSCF) is a SIP server which processes the IMS signaling traffic in order to control multimedia sessions.There are three types of CSCF:
Proxy CSCF (P-CSCF): The initial point of contact for signaling traffic in to the IMS.
Serving CSCF (S-CSCF): Provides the service coordination logic to invoke the application servers needed to deliver the requested service.
Interrogating CSCF (I-CSCF): A SIP proxy that provides a gateway to other domains, such as other service provider networks.
The Home Subscriber Server (HSS) is a centralized database storing the subscriber profile information.
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Brief Explanation IMS Network Elements (2) An Application Server (AS) hosts and executes services and can run in a number of classical SIP operational modes. The application servers mentioned above are attached to the S-CSCFs to
host and serve IMS services. The Media Resource Function (MRF) comprises two nodes: the
Controller and Processor. The MRFC (controller) is situated in the signaling plane as a SIP User
Agent; and the MRFP (processor) is situated in the media plane and provides media related functions, such as serving voice announcements, voice mixing (for conferencing) and video conferencing.
A Border Gateway Control Function (BGCF) identifies if a session terminates on the PSTN and determines which MGCF should handle it.
The Media Gateway (MGW)/Media Gateway Control Function (MGCF) collectively represent equipment that provides interworking with the legacy PSTN.
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IMS Protocol Session Initiation Protocol (SIP): An application layer protocol
for establishing, terminating and modifying multimedia sessions within an IP network. SIP has been embraced as the specified protocol in support
of session control protocol for IMS which follows a client server model.
Session Description Protocol (SDP): is a text based protocol which describes the multimedia session. For example, when initiating a session the caller and callee
indicate and exchange their media capabilities as well as receive address and port number.
Real-Time Protocol (RTP): provides a mechanism to transport real-time multimedia traffic including video and audio over unreliable transport mediums such as User Datagram Protocol (UDP).
Diameter: The Diameter protocol was chosen for use with IMS as the AAA (Authentication, Authorization and Accounting) protocol.
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SIP Protocol IMS builds on the Session Initiation Protocol (SIP), which
has emerged as the crucial technology for controlling communications in IP -Based Next-Generation Networks (NGNs).
The advantages for adopting the SIP as control layer protocol:
Advantages in convergence and interworking of voice and data services
Supports the development of IN network towards the application and terminal sides
Supports mobility function at the application layer Simple protocol with recognized potential for extension.
A Typical Example of an IMS Call
User B
DSL/Cable ModemDSL/Cable Modem
DSLAM/CMTS
RNC
GGSN
Network Z (UMTS/GPRS)Network Z (UMTS/GPRS)
Network XNetwork X
User A
SGSN
Network YNetwork Y
GRXGRXP-CSCF
P-CSCF
I-CSCFI-CSCF
S-CSCFS-CSCF
HSSHSS
ASAS
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Imagine starting a voice call on you home phone and transferring it seamlessly to your mobile as you drive to work.
Imagine sending a multimedia message from your car that later appears on your TV screen.
Imagine watching a movie on that same TV, pausing it in mid-show and then watching it on a wireless PDA as you relax in the garden.
Imagine having a cell phone conversation with two or three friends and simultaneously sharing a video of the football match you are attending.
Imagine that all of the above can be done with a single account, on a single log-in with multiple devices over any number of access networks
These are only a few examples of seamless multimedia services that IMS will allow users to access “anywhere” at “anytime”
Why all of the excitement?
Who needs IMS?Fixed Network Users wantMultimedia conferencing: With PC or SIP phone user can participate in a video conference with mobile or WLAN users. Voice over IP: Cable providers will become phone providers.Streaming Services: Video on demand, wake-up call with music video or latest news.Mobile Network Users wantPush-to-X: PTtalk, PTVideo.Location Based Services: Which of my friends is nearby? Mobile Gaming: Gaming on your mobile, while you chat with a friend you play against.Network Providers wantFixed Mobile Convergence.A service needs to be implemented only once for all kind of access networks.New business models by offering my services to users from other access networks.
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Why do we need IMS? Challenges in services
Difficulty and slowly delivery of new services Single services experience
Challenges from Internet Internet has been competitor of legacy operator Legacy operator must learn from Internet
Challenges in OPEX/CAPEX More network technologies and more network
deployment Duplicated development and deployment leads to higher
CAPEX and OPEX Challenges in Average Revenue Per User (ARPU)
Voice ARPU is decreasing Difficulty for legacy networks to introduce abundant
services and charge for content and service
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Characteristic of IMS - More Convergence
Network resource sharing greatly reduces CAPEX\OPEX Reduce customer churn and improve loyalty
Unified services deliver any application to any terminal Multimedia experience Single user profile, single sign on
Fixe
d N
etw
ork
Mob
ile N
etw
ork
Mob
ile D
ata
Inte
rnet
Multi-ServiceTraditional Network Converged Network
Convergence
Terminal
IP Connectivity
GSM/UMTS BroadbandWLAN
Services & Content
Session Control
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User-Centric NetworkUser-centric network: One network for all services Single Sign-On
IMSService-centric network: Services provided by different network. Sign-On for each service;
Services
Address book
ProfileBillMy rings
Profile
Address book
Bill
User identity, profile, address book and bill are different by each service; Services can’t be customized, or difficult to be customized.
One user identity, one profile, one address book and one bill for all services Customized services
Benefits of IMS User experience in mobility and multimedia Richer services
Abundant and attractive services will boost ARPU Sustained service revenue
Telecom Operators will generate much more revenue by operators always be on top of IP service value chain
Common shared subscriber data Better investment protection
Common IMS Core infrastructure and service Enablers will remain unchanged when new services and access types are introduced.
Initial network investment on IMS Core will be protected during later stages of network deployment
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Subscribers want access to communications services from many places… Home, office, or on-the-go: mobility
isn’t just wireless voice anymore!
from several devices… Telephones, PCs, mobile phones,
PDAs
without needing separate accounts
Single sign-on, common contacts, and “access-aware” information delivery
Home Office Moving Travel
Convergence Networks
Fixed NetworksMobile
Networks
Benefit of IMS-User Experience: Wider Mobility
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Benefit of IMS-User Experience: MultimediaToday
Limited video introducedYesterday
voice leadingTomorrow
User-centric multimedia experience
1.Hi, I am RobertLet us have a talk about our next film
2.Hi, I am Richard
Rich voice, VoD, internet applications, etc
Still can not flexibly add/drop multiple media types, or switch between them within single session
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IP Backbone
IMS Core
Presence
Chat
Media Push
Game
CALL WHITEBOARDRich Call
Push To Talk
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Video
Music Voice
Enterprise AD
Cartoon
Greeting
Play Your True Color
Multimedia RBT
Benefit of IMS - Richer Services
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Benefits of IMS - Sustained Service Revenue
RAN
SGSNSGSN
GGSNGGSN
RAN
SGSNSGSN
GGSNGGSN
ApplicationsApplicationsHSSHSS
CSCFCSCF
RAN
SGSNSGSN
GGSNGGSN
Internet
ApplicationsApplications
Domain Controlled by OperatorOperator risks itself to be a bit pipe
IMS
PS only
Domain Controlled by OperatorEnd-to-End service control
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Benefits of IMS - Common Shared Subscriber Data
Replicated Data
HSSHSS
Now IMS
SESSION CONTROL
Application 1
Application 2
Application X
Application 1
Application 2
Application X
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NAT controlAuth SigComp
Routing Charging
New EnablerMessaging Conference
Presence Group Mngt
Common Functions
Service Enablers
QOS Control Service Trigger
Broadband WLANGSM/UMTS CDMA2000
Application1 Application2 Application3 More Apps
Benefits of IMS - Better Investment Protection
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V2CC - Seamless Multimedia communication
Single Number for both GSM/UMTS and WLAN/WiMAX Bi-directional smooth handover: less than 200ms, no interruption Excellent voice quality: better than GSM Multi-media service enabled
Application & Service
IMS VCC
IMS core network
Public/PrivateWiFi/WiMAX newtwork
CellularNetwork
Indoors OutdoorsVoice Call Continuity
VCC Application Server
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IMS Terminals
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