VoLTE and the IMS

Agenda

IMS Architecture & SIP Proxies

• Understanding the 3GPP
• 3rd Generation Partnership Project
• The Network Operators Strike Back: ETSI TISPAN NGN, 3GPP2, & Cablelabs
• IETF & RFCs
• VoLTE Introduction
• VoLTE + IMS Advantages
• Legacy vs. IMS
• Traditional User Database Management
• Why VoIP Central Control Can Not Compete with IMS
• The 3GPP IMS Architecture
• VoLTE and IMS Architecture Analysis

IMS Building Blocks

• The IMS Core (IP Multimedia Subsystem)
• IMS Core Components
• IBCF and TrGW
• The HSS (Home Subscriber Server)
• The SLF (Subscription Locator Function)
• The EPC (Evolved Packet Core)
• The E-UTRAN (Evolved UMTS Radio Access Network)
• The UTRAN (UMTS Terrestrial Radio Access Network)
• PCRF
• PCRF and its Interfaces

Call Control Paths

• The SERVICE PATH = The Half Call – AS Formed by the SIP REGISTRATION
• An IMS to IMS Call Analysis
• Call Control and Media Paths
• The IMS Half Call Concept
• Application Servers (AS)
• Serving Call Session Function (S-CSCF)

Roaming and Visited

• Visited Network vs. Home Network
• Proxy Call Session Function (P-CSCF)
• S5 (Local Breakout) and Registration
• S8 Access and Registration

VoLTE Access

• Intro to Bearers & APNs
• The Evolved Packet Core Component Analysis
• PDCP, RLC, MAC, PHY, and the LTE Grid

Call Flow

• Intra Domain Service Path Originating
• Intra Domain Service Path Terminating
• Intra Domain Call
• Intra Domain Routing
• Intra Domain Routing Decision
• Intra Domain Call End to End
• Inter-domain Call, Intra-domain Service Paths
• Inter-domain Call Routing
• Cross Domain Routing Decision
• IMS Border Control Function and Transition Gateway
• Inter-domain Roaming
• Inter-domain Call While Roaming
• Both UEs Roaming Plus Inter-Domain Call
• Both UEs Roaming Plus Inter-Domain Call Control Path

IMS Identifiers

• UML Model of the Data Downloaded over Cx Interface
• UICC (Universal Integrated Circuit Card)
• IMSI – International Mobile Subscriber Identity [im-zee]
• IMS Specific Numbering, Addressing and ID
• Home Network Domain Name

VoLTE and IMS Architecture

• The HSS (Home Subscriber Server)
• The SLF (Subscription Locator Function)
• CSCF (Call/Session Control Function)
• P-CSCF (Proxy-Call/Session Control Function)
• I-CSCF (Interrogating-Call/Session Control Function)
• S-CSCF (Serving-Call/Session Control Function )
• Breakout Gateway Control Function (BGCF)
• AS (Application Server)
• MRF - MRFC / MRFP (Media Resource Function Controller / Processor)
• Policy and Charging Rules Function and the EPC
• Mobility Management Entity (MME)
• Serving Gateway (S-GW)
• PDN Gateway (P-GW)

Bearer and APNs

• Bearer Components from the E-UTRAN through the EPC
• VoLTE Bearers from the E-UTRAN through the EPC
• Internet Bearers from E-UTRAN through the EPC
• H.248

Handover Between eNodeBs

• Idle Mode
• Cell Reselection
• Discontinuous Reception (DRX) with Long and Short DRX
• How DRX Timers Apply the LTE Grid
• Idle Mode Within and Beyond the UE
• Active UE
• Intra-frequency Mobility (3GPP TS 23.401)
• Intra MME SGW Handover Using the X2 Interface
• S1-based Handover with S-GW & MME Relocation

Tracking and Paging A UE

• Tracking Area Defined
• Tracking Area Identifiers
• Tracking Area Lists
• Relationship of MME Pool Areas, TA, and S-GW Service Areas
• Tracking Area Update (TAU)
• Idle Mode
• UE Entering Idle Mode
• Paging an Idle UE

SIP Architecture

• Key VoLTE and IMS Protocols
• SIP Message Format
• SIP User Agent (UA)
• SIP Request and Response Format
• IMS SIP Transactions
• SIP Requests (Methods)
• SIP Response Codes
• A SIP Transaction Defined
• PRACK and The 100rel Process (RFC 3262)
• VoLTE to VoLTE SIP Transactions
• SIP Control Path
• Trust Chain

SIP Architecture

• Key VoLTE and IMS Protocols
• SIP Message Format
• SIP User Agent (UA)
• SIP Request and Response Format

IMS SIP Transactions

• SIP Requests (Methods)
• SIP Response Codes
• A SIP Transaction Defined
• PRACK and The 100rel Process (RFC 3262)
• VoLTE to VoLTE SIP Transactions

SIP Control Path

• Trust Chain
• SIP Architecture B2BUA Example: TAS
• Mapping SIP dialogs through an Application Server
• Proxy vs. B2BUA

User Identities

• Address-of-Records and Contact-URIs
• SIP URI
• SIP and SIPS URI Structure Components (RFC 3261)

SIP Via Paths

• The Via Header
• The SIP Transaction
• Impact of Via Path on the SIP Dialog

SIP Route Headers

• The Record-Route and Route Function
• Loop Detection

Basic SIP & IMS Specific Headers

• Start Line
• Via: Via: branch parameter
• From:
• To:
• Call-ID: SIP Dialog ID
• Contact:
• CSeq: (Command Sequence)
• Content-Type:
• Max-Forwards:
• Allow: OPTIONS
• User-Agent:
• Supported:

Advanced Headers and Protocols

• P-Preferred-Identity: and Privacy: RFC 3325
• P-Access-Network-Info: RFC 3455
• Authorization: RFC 3261 Section 22.2
• Path: RFC 3327
• Service-Route: RFC 3608
• Introduction to SigComp

Diameter

• RADIUS vs DIAMETER
• Diameter Protocol
• Diameter Message Structure
• The AVP Chain: Type – Length - Value
• AVPs Encapsulated Inside an AVP
• Diameter Header Structure
• AVP Structure
• Diameter Message as Wireshark Would Display it

Diameter Customization

• IMS's Diameter Cx Command Codes Values
• Diameter AVPs Defined for the Cx Interface
• Diameter AVPs: Rx Interface Codes

Registration

• Call Flow Challenge
• Authorization
• Registration Status
• Registration Termination Request
• Registration Status at the P-CSCF

SCTP

• Traditional Transport Layers (OSI Layer 4)
• Stream Control Transmission Protocol (RFC 4960)
• SCTP High Durability Connections
• Setting Up An Association
• The SCTP Protocol Data Unit
• Head-of-Line-Blocking Avoidance
• Chunking & Bundling

Initial Filter Criteria (iFC)

• iFC Function
• iFC Logic Data Structure
• iFC Logic
• iFC Example Service Profile

Presence

• Presentity and Watcher
• PUBLISH
• SUBSCRIBE
• NOTIFY
• IMS Call Flow
• Cross Domain SUBSCRIBE Example
• PUBLISH presentity and Cross Domain NOTIFY to Watchers

Presence Information

• Basic vs. Rich Presence
• Presence Information Data Format (PIDF) RFC 3863
• Rich Presence Information Data format (RPID) RFC 4480

Session Description Protocol (SDP)

• SDP Establishes ½ the Media Channel
• SDP: RFC 4566
• RTP is "simplex" a=sendonly means what?
• Media Direction's Impact on RTCP

SDP Components

• Version, v=
• Origin, o=
• Session, s=
• Connection, c=
• Time, t=
• Media Description, m=
• Bandwidth, b=

Offer/Answer

• Overview of Offer/Answer
• OFFER/ANSWER Examples
• SDP Offer/Answer Model
• UPDATE RFC 3311

Preconditions

• Preconditions; a=curr and a=des
• Preconditions Call Flow
• Preconditions E2E and Segmented

QoS

• Enforcing QoS
• Linking the IMS Core to the EPC
• PCRF Interfaces
• 3GPP Policy Architecture (Simplified)
• Roaming scenarios: H-PCRF and V-PCRF

Power up Process

• Frequency Scanning and UE Categories
• System Acquisition and RRC Connection Setup
• Primary Synchronization Signal (PSS)
• Cell-ID & Secondary Synchronization Signal (SSS)

Network Attach

• The IMS APN Bearer Establishment
• Attach Request, NAS, Authentication Process
• Encryption and ESM Info
• Location Request and Response
• IMS Call Flow Examples

SIP REGISTER

• Initial IMS REGISTRATION
• IMS SIP Registration and the DIAMETER Query
• IMS SIP Registration REGISTRATION to SCSCF
• IMS SIP Registration aka MD5 CHALLENGE (401)

De-Registration

• UE Initiated De-Registration
• Network Initiated De-Registration

Media Relay

• IMS Call Setup with Media Relay
• Terminal Initiated Session Release

Circuit Switched Fallback

• CSFB Originating
• 3G and 4G Update Message Review
• Combined EPS/IMSI Message
• How SR-VCC Interoperates with the Combined Attach

SR-VCC

• Comparing VCC, ICS, and IMS-SC
• Apply VCC, ICS, and IMS-SC technology to CSFB and SR-VCC
• Mobile Station International Subscriber Directory Number (MSISDN)

The Media Path

• Direct Media
• The Role of the ATCF/ATGW and Media Anchoring
• Interoperation between ATCF/ATGW and MSC

SR-VCC Call Flow

• SR-VCC PS to CS Transfer Message by Message
• SRVCC PS to CS Transfer Control and Media Paths
• SRVCC from E-UTRAN to GERAN without DTM Support

Emergency Call Flow

• 3GPP Emergency Components
• IMS Emergency Sessions
• Topology and Message Flow
• IP Multimedia Subsystem (IMS) Emergency Sessions

Charging in the IMS

• IMS Charging Mechanisms
• Charging Interworking Functions & Reference Points
• Offline Charging Functions
• Online Charging Functions

DNS

• DNS root zone has 13 named authorities
• How a Zone file appears in Linux – Bind9
• How $ORIGIN Impacts the Zone File
• Sample Zone File Organized into a Table
• "SOA" Record – The Start of Authority
• NS-record
• A-record
• SRV-record