In this detailed study of the MEGACO (H.248) architecture, you will learn what H.248 is, how it works, and how it fits in the IMS through a process of lecture and hands-on experience. The lessons in this course are clear, very technical, and always presented with hands-on examples, so you can investigate and reinforce each lesson.

H.248 plays a critical role in the IMS, even though many systems, including the IMS, use SIP. Outbound calls are routed to MGs leading the TDM-based PSTN.

What You'll Learn

• IMS Architecture
• MEGACO Components in the IMSRTP and RTCP
• Command Application Programming Interface
• Transaction Parameters and Programming Interface
• How to Define Packages and Parameters to Events and Signals
• Binary and Text Encoding of the Protocol
• Media Stream Property Tags
• Transport over IP
• Example Call Flows

Who Needs to Attend

This course is for people who want a vendor-neutral, technical understanding of how H.248 works in the IMS.

Prerequisites

• TCP/IP Networking
• Voice over IP Foundations

Follow-On Courses

• VoIP Protocol Essentials: SIP
• The IP Multimedia Subsystem (IMS)

Course Outline

1. IMS Architecture

• MEGACO (H.248) and SIP
• RTP Introduction
• Proxy-CSCF
• Serving-CSCF
• Interrogating-CSCF
• MRFC and MRFP
• BGCF Function
• MGCF, MGW, and SGW
• HSS
• SIP/H.248 Interworking

2. Connection Model

• Contexts
• Terminations
• Termination Dynamics
• TerminationIDs
• Packages
• Termination Properties and Descriptors
• Root Termination
• Commands

3. Descriptors

• Specifying Parameters
• Modem Descriptor
• Multiplex Descriptor
• Media Descriptor
• TerminationState Descriptor
• Stream Descriptor
• LocalControl Descriptor
• Local and Remote Descriptors
• Events Descriptor
• EventBuffer Descriptor
• Signals Descriptor
• Audit Descriptor
• ServiceChange Descriptor
• DigitMap Descriptor
• Statistics Descriptor
• Packages Descriptor
• ObservedEvents Descriptor
• Topology Descriptor
• Error Descriptor

4. RTP

• RTP and RTCP
• Payload Types
• SDP Essentials
• Time Stamps
• RTCP QoS Reporting and MEGACO QoS Statistics

5. Command Application Programming Interface

• Add
• Modify
• Subtract
• Move
• AuditValue
• AuditCapabilities
• Notify
• ServiceChange
• Manipulating and Auditing Context Attributes
• Generic Command Syntax
• Command Error Codes

6. Transactions

• Common Parameters
  • Transaction Identifiers
  • Context Identifiers
• Transaction Application Programming Interface
  • TransactionRequest
  • TransactionReply
  • TransactionPending
• Messages
• Ordering of Commands
• Protection against Restart Avalanche
• Security Considerations
• Protection of Protocol Connections
• Interim AH Scheme
• Protection of Media Connections
• MG-MGC Control Interface
• Multiple Virtual MGs
• Cold Start
• Negotiation of Protocol Version
• Failure of a MG
• Failure of an MGC
• Package Definition
• Guidelines for Defining Packages
  • Package
  • Properties
  • Events
  • Signals
  • Statistics
  • Procedures
• Guidelines to Defining Parameters to Events and Signals
• Lists
• Identifiers
• Package Registration
  • IANA Considerations
• Packages
• Error Codes
• ServiceChange Reasons

7. ANNEX A: Binary Encoding of the Protocol

• Coding of Wildcards
• ASN Syntax Specification
• Digit Maps and Path Names

8. ANNEX B: Text Encoding of the Protocol

• Coding of Wildcards
• ABNF Specification
• Hexadecimal Octet Coding
• Hexadecimal Octet Sequence

9. ANNEX C: Tags for Media Stream Properties

• General Media Attributes
• Mux Properties
• General Bearer Properties
• General ATM Properties
• Frame Relay
• IP
• ATM AAL
• ATM AAL
• Bearer Capabilities
• AAL Properties
• SDP Equivalents

10. ANNEX D: Transport over IP

• Transport over IP/UDP using Application Level Framing
• Providing At-Most-Once Functionality
• Transaction Identifiers and Three-Way Handshake
• Computing Retransmission Timers
• Provisional Responses
• Repeating Requests, Responses and Acknowledgements
• Using TCP
• Ordering Of Commands

11. ANNEX E: Basic Packages

• Generic
• Base Root Package
• Tone Generator Package
• Tone Detection Package
• Basic DTMF Generator Package
• DTMF Detection Package
• Call Progress Tones Generator Package
• Call Progress Tones Detection Package
• Analog Line Supervision Package
• Basic Continuity Package
• Network Package
• RTP Package
• TDM Circuit Package

12. APPENDIX I: Example Call Flows (Informative)

• A Residential Gateway to Residential Gateway Call
• A Programming Residential GW Analog Line Terminations for Idle Behavior
• A Collecting Originator Digits and Initiating Termination