Ngn

Existing Network Infrastructure
•
•
•
•
•

Today’s network is divided into:
The Public Switched Telephone Network,
The Packet Switched Networks and
The Mobile networks (PLMN).
Convergence is the process of
interconnection of traditional switched
circuit networks (PSTN and PLMN) and
packet-switched networks based on the
Internet Protocol (IP) for routing.
10th Annual Conference of Computer Society of Iran, CSICC'2005
2

Key drivers of NGN development
One network for everything
Today

Tomorrow

Internet

Telephone
network

Mobile radio
network

IP-Network

Multimedia Access - Advantages:
• easy to handle
• reliable
• mobile

3

NGN


Outline

•
•
•
•
•
•
•

NGN Architecture
NGN Layers
NGN Main Components
SG (Signaling Gateway)
MG (Media Gateway)
MGC (Media Gateway Controller)
Servers
4

NGN
 Outline (cont.)
•
•
•
•
•
•

NGN and Protocols
Call Control & Signaling Protocols
Gateway Control Protocols
Media Transfer Protocols
NGN Migration
Conclusion
5

NGN
 Outline
•
•
•
•
•
•
•

NGN Architecture
NGN Layers
NGN Main Components
MG (Media Gateway)
Servers

6

NGN Architecture
• The architecture basically comprises of :
– Network Elements needed for the provision of
traditional Telephony services.

• NGN has a layered architecture.
• The layers of NGN :
– Access layer,
– Core layer,
– Control layer and
– Service layer.
7

NGN Architecture
• Each element :
– has distinct roles within the network,
– designed to integrate :
• horizontally with other elements in the same layer,
• vertically with the function-based elements of the
other layers.

8

NGN Architecture
Management system

Management
Applications

Application
Servers
Softswitches

Control

Core

Edge
Access

Mobile
W
AN

UTRAN

Enterprise Customers

Packet Network
Content

Broadband
DSL

Cable

Remote Office/SOHO

Media
Gateway

PSTN
CO

W
LL

Residential
Users

Mobile
Users

9

What is NGN?

H.323Network

SIP /
SIP-T

H.323

Appl.
Server
ENUM
Server

BIND
H.323
/ SIP

SIP

SIP
SIP
Proxy

Firewall

SIP
SIP

Media
Server

SIP-T / BICC

MGC

MGC

SIP
DSS1 over SCTP /
SIGTRAN

SS7 over
SCTP / SIGTRAN

MEGACO/
H.248
BBRAS

AG
DSS1

Packet
Network

MG
TDM

SG
SS7

MG

SG

TDM

PSTN

SS7

PLMN

PABX

NGN protocols
SIP
Telephone

Soft
Phone

10

GSM

NGN architecture, IP-oriented NGN model
Softswitch
Content server

Services

NOC

PSTN, GSM, ATM, ...

Gateway

IP network

Transit gateway

Transport

11

NGN
 Outline
•
•
•
•
•
•
•

NGN Architecture
NGN Layers
NGN Main Components
MG (Media Gateway)
Servers

12

NGN Layers
• Characters of Layers :
– Open Architecture;
• open Interface and
• Open Protocols between layers.

13

NGN layers
•

The Next Generation Networks
architecture is based on four
layers:
 Access

layer,
 Core layer,
 Control layer and
 Application & Service layer.
14

NGN layers
1. Access layer includes :
– Traditional networks;
•

PSTN, ISDN, PLMN, …

– Specialized packet networks.


Access layer elements include different
Media Gateways that support connection to
and from the access network with the core
network.
15

NGN layers
2. Core layer is the network handling
converged services based on IP.
– Includes high capacity switches and routers,
in addition high capacity links.

3. Control layer is the Call Server that
provides:
– Call Control functions and
– The Control of the Media Gateway.
16

NGN Control Layer
• Provide capabilities of:
–
–
–
–

Call Control,
Connection Control,
Protocol Handling and
Other management issues

• The primary part of this layer is:
Softswitch.
17

NGN Ctrl Layer


Softswitch

•
•
•

Is the core of NGN,
Independent of Transport Layer.
Main functions are included:
–
–
–
–
–
–

Call control
Resource distribution
Protocol handling
Routing
Authentication and
Charging
18

NGN Ctrl Layer
• handles signaling and management
entities.
• Never concerns with detailed routing
procedures and controlling network
partial components.
• its other tasks are:
– Providing Security for connections and
– Network Management.
19

NGN layers
4. Application & Service layer :
– plays the role of an IN-SCE (Intelligent Network
Service Creation Environment) extending their
functionality in order to cover the new network
scenarios.

20

NGN App. & Service Layer
Application Creation Environment

Application
Server

Call
Server

Access
Network

Media
Gateway

Call
Server

Packet
Network

Media
Gateway

Access
Network

21

NGN
 Outline
•
•
•
•
•
•
•

NGN Architecture
NGN Layers
NGN Main Components
MG (Media Gateway)
Servers

22

NGN main components
Network
controller

SOFTSWITCH
Gatekeeper

SS7

NOC

H.323
MGCP

АDSL
POTS
ISDN
PRI
V5.x

P
GC
M

(VoIP)

Multiservice access

Gateway

23

Softswitch combines the
advantages of both networks
PSTN
Switch
Switch

Data networks
Switch
Switch

Flexible
bandwidth

QoS

Effective transmission

Services

SOFTSWITCH

Voiceservices for IP-users
VoIP
24

Media Server in a Softswitch
Architecture
Basic Services

Enhanced Services
Application
Server

Softswitch
H.323/SIP
H.323/SIP/MGC
P

IP Phone

MGCP/Megaco

MGCP/
Megaco

MGCP,Megaco,
SIP,VoiceXML

RTP

RTP
VoATM

Traditional
Phone

Media Gateway
(xDSL, cable, PSTN,
wireless)

Media Server

25

NGN Components
•
•
•
•
•
•
•

The Softswitch
The Packet core Network
The Access Networks
The Media & signaling Gateways
The Call Server
The application Server
The Application Creation Environment
26

NGN
 Outline
•
•
•
•
•
•
•

NGN Architecture
NGN Layers
NGN Main Components
MG (Media Gateway)
Servers

27

SG, Signaling Gateway
SS7 over IP
SIGTRAN / TALI / Q.2111

SS7
Network

Signaling
Gateway

IP/ATM

IP Telephony
Application

SS7
Device
SS7 - > IP protocol Translation

Protocol

Protocol
MTP3

MTP3

Protocols

Protocols

MTP2

MTP2

UDP
IP

UDP
IP

28

NGN
 Outline
•
•
•
•
•
•
•

NGN Architecture
NGN Layers
NGN Main Components
MG (Media Gateway)
Servers

29

NGN Media Gateway





Provides Translations between
circuit switched networks and packet
switched networks.
Sends notification to the call agent
about endpoint events.
Execute commands from the call
agents.

30

NGN Media Gateway
 Media Gateway Functionality
• Bearer Interworking Function
– Interworking Between Multiple Interface
Protocols: ATM,TDM, Frame Based (IP, FR)
– QoS, Traffic and Congestion Management

• Congestion Management
– Using Priorities based on Traffic Parameters
31

NGN Media Gateway
• Different QoS For Different Services
• Traffic Policing per Connection
• Traffic Shaping per Connection
– Flat Shaping
– Hierarchical Shaping (shaped VCs in
shaped VPs)

32

Media Gateway Architecture

33

MG Types
According to capacity and access level to
the core network, Media Gateway is
categorized to 3 groups:
• Trunking Gateway
• Access Gateway
• Residential Gateway

34

NGN
 Outline
•
•
•
•
•
•
•

NGN Architecture
NGN Layers
NGN Main Components
MG (Media Gateway)
Servers

35

NGN MGC


Media Gateway Controller Functionality

• Provides End-to-End Call Control
• Supports Call Control Signaling (ISUP,
BICC, IN/TCAP, ISDN)
• Supports Signaling Interworking Between
Different Signaling Protocols (e.g., ISDNISUP-BICC)
36

NGN MGC
• Correlates Between Call Control Signaling
and Bearer Control Signaling (BICC)
• Communicates With Feature Servers to
Determine Service and Some Call
Parameters (TCAP)
• Coordinates Call Progress and Resources
Management with the Bearer Control
Function (H.248/MEGACO)
37

Media Gateway Controller
Media
Gateway
Controller

SIGTRAN

SIP-BCP-T
Control Switch
Call Agent
Media Gateway Controller (MGC)
H.323

TALI

PSTN Switch

SIP

MGCP

MEGACO

Media Gateway Controller

Signaling Gateway
Call
Handling

Call
Handling
Protocol Translation
and addressing

ISUP

ISUP

MTP3

MTP3

MTP2

MTP2

Protocol
SIGTRAN
UDP
IP

Protocol
SIGTRAN
UDP
IP

38

NGN
 Outline
•
•
•
•
•
•
•

NGN Architecture
NGN Layers
NGN Main Components
MG (Media Gateway)
Servers

39

Servers
• Application Server
• Media Server
• Call Server
• Feature Server
40

Application Server
App. Server functionality :
•
•
•
•
•
•

No. 800 service
No. 900 service
Billing services
VPN
Calling Card services
IN services
41

Media Server
Media Server functionality :
•
•
•
•
•
•
•

Voice Mail services
Fax Mail Box
Voice Recognition
Video Conferencing
Voice to Text
Unified Messaging
Fax over IP by means of T.38
42

NGN
 Outline (cont.)
•
•
•
•
•
•

NGN and Protocols
NGN Migration
Conclusion

43

NGN and Protocols
NGN requires new protocols to support
converged networks.
 Requirements
• Support for
– Legacy PSTN interworking,
– Migration Plan from legacy to NGN,
– High Availability,
– Lifeline services and
– Scalability
44

NGN and Protocols
• With so many protocols, which one to
choose?
– H.323,
– SIP (Session Initiation Protocol),
– MGCP,
– H.248/MEGAco and
– SIGTRAN

45

NGN Protocols

46

NGN
 Outline (cont.)
•
•
•
•
•
•

NGN and Protocols
NGN Migration
Conclusion

47

SIP, H.323 and MGCP
Call Control and Signaling

Signaling and
Gateway Control

Media
Audio/
Video

H.323
H.225
H.245

Q.931

RAS

SIP

MGCP

TCP

RTP

RTCP

RTSP

UDP
IP

H.323 Version 1 and 2 supports H.245 over TCP, Q.931 over TCP and RAS over UDP.

H.323 Version 3 and 4 supports H.245 and Q.931 over UDP/TCP and RAS over UDP.

SIP supports TCP and UDP.

48

NGN Signaling Protocols

Session Initiation Protocol
SIP

49

What is SIP?

“

An application layer signaling protocol that
defines
• Initiation,
• Modification and
• Termination
of interactive, multimedia communication
sessions between users.

”

IETF RFC 2543 Session Initiation
Protocol
50

SIP components
• User Agent Client (UAC)
– End systems
– Send SIP requests

• User Agent Server (UAS)
– Listens for call requests
– Prompts user or executes program to
determine response

• User Agent
– UAC plus UAS
51

SIP components

(cont.)

• Redirect Server
– Network server - redirects users to try other
server

• Proxy Server
– Network server - a proxy request to another
server can “fork” request to multiple servers,
creating a search tree

• Registrar
– Receives registrations regarding current user
locations
52

User Agents
• An application that initiates, receives and
terminates calls.
– User Agent Clients (UAC) – An entity that
initiates a call.
– User Agent Server (UAS) – An entity that
receives a call.
– Both UAC and UAS can terminate a call.
53

Proxy Server
– An intermediary program that acts as both a
server and a client to make requests on
behalf of other clients.
– Requests are serviced internally or by passing
them on, possibly after translation, to other
servers.
– Interprets, rewrites or translates a request
message before forwarding it.

54

Location Server
• A location server is used by :
– Redirect Server or
– Proxy Server

• To obtain information about a called
party’s possible location(s).

55

Redirect Server
• A server that :
– Accepts a SIP request,
– maps the address into zero or more new addresses
and
– Returns these addresses to the client.

• Unlike a proxy server, the redirect server does not
initiate its own SIP request.
• Unlike a user agent server, the redirect server
does not accept or terminate calls.
56

Registrar Server
– A server that accepts REGISTER requests.
– The register server may support authentication.
– A registrar server is typically co-located with a
proxy or redirect server and may offer location
services.

57

SIP architecture
Registrar
SQL/LDAP/?

RE
GI
ST
ER

• On Startup, SIP UA Sends
REGISTER to Registrar
• Registration Data Provides
Addresses to Reach User
• Registration Database
Forms a Dynamic Routing
Database of Users
• Centralized Store is Desired
for Scalability

DB

Proxy Farm

INVITE

58

SIP Distributed Architecture
SIP Components

Location
Server

Redirect
Server

Registrar
Server

PSTN
User Agent

Gateway
Proxy
Server

Proxy
Server

59

SIP Addressing
• The SIP address is identified by a SIP
URL, in the format: user@host.
– Examples of SIP URLs:
• sip:hostname@vovida.org
• sip:hostname@192.168.10.1
• sip:14083831088@vovida.org

60

SIP Messages
Methods and Responses

SIP components communicate by exchanging SIP messages:
•

SIP Methods:
– INVITE – Initiates a call by inviting
user to participate in session.
– ACK - Confirms that the client has
received a final response to an
INVITE request.
– BYE - Indicates termination of the
call.
– CANCEL - Cancels a pending
request.
– REGISTER – Registers the user
agent.
– OPTIONS – Used to query the
capabilities of a server.
– INFO – Used to carry out-of-bound
information, such as DTMF digits.

• SIP Responses:
– 1xx - Informational
Messages.
– 2xx - Successful
Responses.
– 3xx - Redirection
Responses.
– 4xx - Request Failure
Responses.
– 5xx - Server Failure
Responses.
– 6xx - Global Failures
Responses.

61

Process for Establishing
Communication
Establishing communication using SIP usually occurs in six
steps:
1. Registering, initiating and locating the user.
2. Determine the media to use – involves delivering a
description of the session that the user is invited to.
3. Determine the willingness of the called party to
communicate – the called party must send a response
message to indicate willingness to communicate –
accept or reject.
4. Call setup.
5. Call modification or handling – example, call transfer
(optional).
6. Call termination.
62

SIP

Protocols related to SIP

63

Session Description Protocol
(SDP)
• Used to specify client capabilities
• Example: (client can support MPEG-1
video codec, and MP3 codecs)

64

Session Announcement Protocol
(SAP)
• Originated around same time as SIP
• Used to announce multimedia sessions
– Announcement goes to users in a multicast
group
– Announcements can contain :
• Start Time of session,
• Duration of session, etc.
65

SIP Framework
– Session initiation.
– Multiple users.
– Interactive
multimedia
applications.

66

SIP – Design Framework
• SIP was designed for:
– Integration with existing IETF
protocols.
– Scalability,
– Simplicity,
– Mobility and
– Easy feature and service creation.
67

Integration with IETF Protocols
(1)
• Other IETF protocol standards can be used to
build a SIP based application. SIP can works
with existing IETF protocols, for example:
– RSVP - to reserve network resources.
– RTP Real Time Protocol -to transport real
time data and provide QOS feedback.
– RTSP Real Time Streaming Protocol - for
controlling delivery of streaming media.
– SAP Session Advertisement Protocol - for
advertising multimedia session via multicast.
68

Integration with IETF Protocols
(2)
– SDP Session Description Protocol – for
describing multimedia sessions.
– MIME – Multipurpose Internet Mail
Extension – defacto standard for describing
content on the Internet.
– HTTP – Hypertext Transfer Protocol - HTTP
is the standard protocol used for serving
web pages over the Internet.
– COPS – Common Open Policy Service.
– OSP – Open Settlement Protocol.
69

Scalability
• The SIP architecture is scalable, flexible
and distributed.
– Functionality such as proxying,
redirection, location, or registration can
reside in different physical servers.
– Distributed functionality allows new
processes to be added without affecting
other components.
70

Simplicity
• SIP is designed to be:
– “Fast and simple in the core.”
– “Smarter with less volume at the edge.”
– Text based for :
• Easy implementation and
• Debugging.

71

Mobility
• SIP supports user mobility by proxying and redirecting
requests to a user’s current location.
• The user can be using a :
–
–
–
–
–

PC at work,
PC at home,
Wireless phone,
IP phone or
Regular phone.

• The user must register their current location.
• The proxy server will forward calls to the user’s current
location.
• Example mobility applications include presence and call
forking.
72

Feature Creation
• A SIP based system can support rapid
feature and service creations.
• Features and services can be created
using:
– Call Processing Language (CPL).
– Common Gateway Interface (CGI).

73

Feature Creation
• SIP can support these features and applications:
– Basic call features
• Call waiting,
• Call forwarding,
• Call blocking.

–
–
–
–
–
–

Unified messaging.
Call forking.
Click to talk.
Presence.
Instant messaging.
Find me / Follow me.
74

NGN Signaling Protocols

H.323

75

What is H.323?

“

• H.323 is a standard that specifies
– Protocols,
– Components and
– Procedures

• That provide multimedia communication services, realtime audio, video, and data communications over
packet networks, including IP based networks.
• H.323 is part of a family of ITU-T recommendations
called H.32x that provides multimedia communication
services over a variety of networks.

,
,

76

H.323 Framework
H.323 defines:
– Call establishment and termination.
– Audio visual or multimedia conferencing.

77

H.323 Components
Terminals
Gateways

Gatekeeper

Gatekeepers

Multipoint
Control
Unit

Multipoint
Control

Units

(MCUs)

Circuit
Switched

Packet Based

Networks

Networks
Terminal

Gateway

78

H.323 Terminals
H.323 terminals are client endpoints that
must support:
–
–
–
–

H.225 call control signaling.
H.245 control channel signaling.
RTP/RTCP protocols for media packets.
Audio codecs.

 Video codecs support is optional.
79

H.323 Gateway
A gateway provides translation:
– Gateway translates the messages that
belongs to the two different networks with
different protocol stacks.
– Gateways can also provide :
•
•
•
•

Transmission formats translation,
Communication procedures translation,
H.323 and non-H.323 endpoints translations or
Codec translation.

80

H.323 Gatekeepers
• Gatekeepers provide these functions:
– Address translation.
– Admission control.
– Bandwidth control.
– Zone management.
– Call control signaling (optional).
– Call authorization (optional).
– Bandwidth management (optional).
– Call management (optional).
• Gatekeepers are optional but if present in a H.323
system, all H.323 endpoints must register with the
gatekeeper and receive permission before making a call.
81

H.323 Multipoint Control Unit
(MCU)
• MCU provide support for conferences of
three or more endpoints.
• An MCU consist of:
– Multipoint Controller (MC) – provides control
functions.
– Multipoint Processor (MP) – receives and
processes audio, video and/or data streams.

82

H.323 is an “Umbrella”
Specification

Media
H.261 and H.263 – Video codecs.
G.711, G.723, G.729 – Audio codecs.
RTP/RTCP – Media.
Data/Fax
T.120 – Data conferencing.
T.38 – Fax.
Call Control and Signaling
H.245 - Capabilities advertisement,
media channel establishment, and
conference control.
H.225
Q.931 - call signaling and call setup.
RAS - registration and other admission
control with a gatekeeper.

H.323
Media

Data/Fax Call Control and
Signaling

Audio
Codec
G.711
G.723
G.729

Video
Codec
H.261

RTCP

T.120 T.38

H.263

H.225 H.225
Q.931 RAS

H.245

RTP
UDP

TCP

TCP

UDP

IP

83

TCP

H.323 – H.245
• Establishes logical channels for
transmission of H.323 data
– Negotiates:
• channel usage
• master/slave configuration
• flow control
• Codec used (capability exchange)

84

H.323 – H.245 Messages
• Master/Slave Determination
– Determines which terminal will be master which will
be slave in the call

• Terminal Capability Set
– Contains information on a terminal’s ability to send
and receive multimedia streams

• Open Logical Channel
– Opens logical channel for transport of multimedia
data

• Close Logic Channel
– Closes the logical channel between two endpoints
85

• Request Mode
– Receive terminal requests type of
transportation from a transmit terminal
– Types of Modes:
•
•
•
•

Video
Audio
Data
Encryption

86

• Send Terminal Capacity Set
– Instructs far-end terminal to send transmit and
receive capabilities

• End Session Command
– Indicates the end of the H.245 session

87

Other ITU H. Recommendation
that work with H.323
Protocol

Description

H.235

Specifies security and encryption for H.323 and H.245 based terminals.

H.450.N

H.450.1 specifies framework for supplementary services. H.450.N
recommendation specifies supplementary services such as call
transfer, call diversion, call hold, call park, call waiting, message waiting
indication, name identification, call completion, call offer, and call
intrusion.

H.246

Specifies internetworking of H Series terminals with circuit switched
terminals.

88

NGN Signaling protocols

Comparing
SIP and H.323

89

Comparing SIP and H.323
Similarities

• Functionally, SIP and H.323 are similar.
Both SIP and H.323 provide:
– Call control, call setup and teardown.
– Basic call features such as :
– Call waiting,
– Call hold,
– Call transfer,
– Call forwarding,
– Call return,
– Call identification or
– Call park.
– Capabilities exchange.

90

Comparing SIP and H.323
Strengths
•

H.323 – Defines sophisticated multimedia
conferencing. H.323 multimedia conferencing can
support applications such as:
–
–
–

•

•

Whiteboarding,
Data Collaboration and
Video Conferencing.

SIP – Supports flexible and intuitive feature creation
with SIP using SIP-CGI (SIP-Common Gateway
Interface) and CPL (Call Processing Language).
SIP – Third party call control is currently only
available in SIP. Work is in progress to add this
functionality to H.323.
91

NGN
 Outline (cont.)
•
•
•
•
•
•

NGN and Protocols
NGN Migration
Conclusion

92



MGCP (Media Gateway Control Protocol)



H.248/MEGAco

93

MGCP
• RFC 2705
• Controlling VoIP Gateways from External Call Control
Elements
• History:
– Simple Gateway Control Protocol (SGCP): Bell
core / Cisco
– IP Device Control (IPDC): extended work of XCOM,
Ascend & others.
– Media Gateway Control Protocol (MGCP): Merged
IPDC + SGCP
– Media Device Control Protocol (MDCP): Lucent
– H.GCP: ITU SG16 Functional Decomposition
Control Protocol
94

What is MGCP?

“

•Media Gateway Control Protocol – A
protocol for :
– Controlling Telephony gateways from
external call control elements called
media gateway controllers or call agents.
IETF RFC 2705 Media Gateway Control
Protocol
95

”

MGCP
• Decompose gateway into :
– A controlling signalling component and
– A controlled media component.

• Can be used in phones or gateways in
conjunction with SIP

96

MGCP


Call agent or media gateway
controller
– Provides call signaling,
control and processing
intelligence to the gateway.
– Sends and receives
commands to/from the
gateway.

Call Agent or
Media Gateway
Controller
(MGC)

Call Agent or

SIP Media Gateway
H.323
Controller
(MGC)

MGCP

MGCP

Media Gateway
(MG)

Media Gateway
(MG)

97

MGCP Commands
• Call Agent
Commands:

• Gateway Commands:
– Notify
– EndpointConfiguration – DeleteConnection
– NotificationRequest
– RestartInProgress
– CreateConnection
– ModifyConnection
– DeleteConnection
– AuditEndpoint
– AuditConnection
98

Characteristics of MGCP


MGCP
– A master/slave protocol.
• Assumes limited intelligence at the edge
(endpoints) and intelligence at the core (call
agent).
• Used between call agents and media gateways.
• Differs from SIP and H.323 which are peer-to-peer
protocols.

– Interoperates with SIP and H.323.
99

MGCP, SIP and H.323
– MGCP divides call setup/control
and media establishment
functions.
– MGCP does not replace SIP or
H.323. SIP and H.323 provide
symmetrical or peer-to-peer call
setup/control.
– MGCP interoperates with H.323
and SIP. For example,
• A call agent accepts SIP or H.323 call
setup requests.
• The call agent uses MGCP to control
the media gateway.
• The media gateway establishes media
sessions with other H.323 or SIP
endpoints.

In this example, an H.323 gateway is
“decomposed” into:
–A call agent that provides signaling.
–A gateway that handles media.
MGCP protocol is used to control
the gateway.
H.323 Gateway
H.323
Call
Agent/
Media
Gateway
Controller

H.323
Gateway

MGCP
Media RTP/RTCP

Media
Gateway

100

Example Comparison
H.323
1.

A user picks up analog phone and
dials a number.

2.

The gateway determines how to
route the call.

3.

The two gateways exchange
capabilities information.

4.

The terminating gateway rings the
phone.

5.

The two gateways establish
RTP/RTCP session with each other.

MGCP
1.

A user picks up analog phone and dials
a number.

2.

The gateway notifies call agent of the
phone (endpoint) event.

3.

The Call agent determines capabilities,
routing information, and issues a
command to the gateways to establish
RTP/RTCP session with other end.

3
1

2

5.RTP
/RTCP
H.323
Gateway

Analog
Phone

H.323
Gateway

4

Call Agent/
Media
Gateway
Controller

1
Analog
Phone

Gateway A
Analog
Phone

RTP/
RTC Gateway B
P

Analog
Phone

101

What is Megaco?
• A protocol that is evolving from MGCP and
developed jointly by ITU and IETF:

– Megaco - IETF.
– H.248 or H.GCP - ITU.

102

MEGAco

103

Summary
• SIP and H.323 are comparable protocols that provide
–
–
–
–
–

Call Setup,
Call Teardown,
Call Control,
Capabilities Exchange and
Supplementary features.

• MGCP is a protocol for controlling media gateways from
call agents. In a VoIP system, MGCP can be used with
SIP or H.323.
• SIP or H.323 will provide the call control functionality and
MGCP can be used to manage media establishment in
media gateways.
104

NGN
 Outline (cont.)
•
•
•
•
•
•

NGN and Protocols
NGN Migration
Conclusion

105

Real-Time Transport Protocol
(RTP)
IETF standard: RFC 3550
• Provides end-to-end delivery services for
data with real-time characteristics, such as
interactive audio and video
• Specifies a packet structure for packets
carrying audio and video data
• RTP packet provides
– payload type identification
– packet sequence numbering
– time stamping
106

RTP (2)
• RTP runs in the end
systems
• RTP packets are
encapsulated in UDP
segments
• Provides a transportlayer interface
(“OSI-Layer 4b”)
• Attempts to avoid
jitter

107

RTP (3)
• RTP does not provide:
– Any mechanism to ensure timely delivery of data
– Any quality of service guarantees
• RTP encapsulation is only seen at the end systems
– Not recognized by routers as a special kind of
datagram
– Routers providing best-effort service do not make any
special effort to ensure that RTP packets arrive at the
destination in a timely matter
• Allows for each voice or video device to have its own
RTP stream
• Supports unicast as well as multicast applications
108

Real-Time Control Protocol
(RTCP)
• Works in conjunction with RTP
• It’s Main function is Echo Cancellation
• Each participant in RTP session
periodically transmits RTCP control
packets to all other participants
• Transfers necessary information to
synchronize transmitter & receiver
109

RTCP
• Each RTCP packet contains sender and/or
receiver reports
– Report statistics useful to application
• Statistics include :
– Number of packets sent,
– Number of packets lost,
– Interarrival jitter, etc.

• Feedback can be used to control performance
– Sender may modify its transmissions based
on feedback (incl. Bandwidth scaling)
110

RTCP (2)
• For an RTP session there is
typically a single multicast
address; all RTP and RTCP
packets belonging to the
session use it
• RTP and RTCP packets are
distinguished from each other
through the use of distinct port
numbers (RTCP port = RTP
port + 1)
• To limit traffic, each participant
reduces its RTCP traffic as the
number of conference
participants increases
111

NGN
 Outline (cont.)
•
•
•
•
•
•

NGN and Protocols
NGN Migration
Conclusion

112

Migration Strategies
•
•
•
•
•

EUROSCOM
SIEMENS
ALCATEL
LUCENT
ZTE
113

EUROSCOM Migration Scenario
One of the migration scenarios which breaks the
problem into smaller part.
The following network diagrams represent how the
architectural model may be instantiated for some
scenarios of interest to a network operator. Each
figure displays the functions and interfaces
required of each network scenario. For each
interface, suggestions are provided as examples of
typical inter-working protocols.
114


PSTN to IP network

interface scenario

115


GSM PLMN (Mobile) to IP network
116

Alcatel Migration Scenario
• Alcatel presents a step-by-step
migration scenario from a TDM-based
public switched telephone network to
a packet based next generation
network. Six steps consolidation and
expansion scenario is elaborated.

117

Alcatel Migration Scenario
1.
2.
3.
4.

PSTN for Voice and Internet Access.
PSTN Consolidation.
Voice over Packet Trunking (IP or ATM).
Voice over Packet Access (ADSL, LMDS
or cable)
5. Introduction of Multimedia
6. Migration to Full NGN
118

Alcatel Full NGN

119

Siemens Migration Scenario

• Siemens proposed a Next Generation Network
migration Strategy based on class 4 and 5
softswitch replacement.
First: migrate the transit level

120

Then, introduce IP-based services

121

Finally, replace local switches

122

Lucent Migration Scenarios
•First Scenario: Focus on Voice over BroadBand and
minimize risk
Step 1:
–Start with VoBB solutions based on voice gateway
–Reuse existing TDM network and OAM infrastructure
–QoS is manageable, avoid risks of softswitch technology
–Get experience with various customer premises
equipment (CPE)
–Get experience with commercial packaging and market
acceptance

Step2:
–Migrate to full NGN solution Get cost advantages of endto-end VoIP solution Introduce more advanced NGN
applications (SIP, application severs).
123

Lucent Migration Scenario
• Second scenario: Focus on traffic offload
and cost-effective gateways
Step1:
– Start with LSS-based ICD application for internet
offload
– Reuse dial-in gateways also for VoIP
– Introduce VoIP backbone network

Step2:
– Add VoIP endpoint support for Voice over
Broadband
– Introduce more advanced NGN applications (SIP,
application servers)
124

ZTE Migration Scenario
• ZTE produced two strategies for PSTN evolution
based on softswitch network solutions.
– Strategy 1: Softswitch device together with Trunking
Gateway carries out the functions of legacy tandem
and toll exchanges whilst the Class 5 terminal
exchange remains the same .
– Strategy 2: Softswitch devices together with Access
Gateway carries out the functions of legacy terminal
exchange while twisted pair user interface remains
the same.
125


ZTE Evolution Strategy 1 of existing PSTN/ISDN
126


ZTE Evolution Strategy 2 of Existing PSTN/ISDN
127

NGN
 Outline (cont.)
•
•
•
•
•
•

NGN and Protocols
NGN Migration
Conclusion

128

Conclusion
• The ultimate requirement of the NGN is to
handle packetized voice and data in a
converged manner.
• Next generation networks are not just a PSTN
replacement but at a minimum they must
provide the equivalent voice quality and
reliability of today’s PSTN.
• The NGN will be the foundation for the creation
of a new range of multimedia applications that
take full advantage of the characteristics of the
broadband network and the “always on”
capability.
129

Conclusion
The users that are most ready to embrace
the new opportunity will be the first to be
migrated to the NGN model, this will then be
a commercial migration with the emphasis
being placed on new revenue opportunities.
The creation of the NGN is no overnight
transformation, but it is an evolution that is
already underway and gathering pace.
130

Thanks
for your

Attention
131

Ngn

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