sata voip workshop ngn-concepts

8/8/2019 SATA VoIP Workshop NGN-Concepts

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VoIPVoIP and Broadband Technologiesand Broadband Technologies

Southern Africa Development CommunitySouthern Africa Development CommunityLuanda, AngolaLuanda, Angola , October 2005, October 2005

Oscar González Soto

ITU Consultant Expert

Strategic Planning and Assessment

NGN Concepts and Elements



October, 2005 ITU- BDT NGN Introduction slide 2


• Motivation and concept

• NGN Architecture

• Network Elements

• Performance and Status




MotivationMotivation

PremisesPremises• Strategic Trends

– data traffic (bandwidth) will become 2 to 5 times higher than the voice

traffic. – IP is becoming the universal transport protocol used by all services

• How PSTN should evolve ?

– as before, with its dedicated optimised technology (TDM) ?

– or move to packet IP networks, telephony being a service amongothers ?

• Background reasons to evolve

– service merge and new services – DSL and other broadband access penetration

– cost of ownership: unique instead of separated networks





PremisesPremises• Packet technology for voice is emerging

– rapid evolution in its performance, features, and costs (CAPEX)

– addresses evolution to multimedia services

• However, Not yet in a large scale deployment

– focused applications (dialup offload, long distance bypass)

– many trials

– few strategic decisions of operators to move part of their PSTN network

to NGN

– gradual transition, just starting.

• General feeling / agreement that it will take time

– for technological reasons

– for economical reasons





NGN concept

•A multi-service network able to support voice, data and video

•A network with a control plane (signaling, control) separated from

the transport/switching plane

•A network with open interfaces between transport, control and

applications

•A network using packet mode technology to transport of all kind

of information

•A network with guaranteed QoS for different traffic types and SLAs





WhyWhy

• Flexibility for service building and offering

• Expectation of cost reductions by sharing infrastructure and

systems

• Simplification of O&M, thus lowering OPEX.

• Use of open interfaces leads for:

- quick deployment of services and applications- new services (third parties)




Network Architecture towardsNetwork Architecture towards NGNNGN

Existing networks and architectureExisting networks and architecture

• 5 different network types to handletelecom services

• TDM for fixed and mobile networksworking in circuit mode with end to

end reserved paths• SS7 and IN network working withmessage switching mode

• Data network working with leased

lines and packet mode with differentand conventional IP protocols

SCP

TDM

POTS ISDN

RSU

LEX/TEX

LEX

PCM

DataATM/IP

MUX/DSLAM

NMC

SS7

HDSL/XDSL

NAS

Mob

IN




Network ArchitectureNetwork Architecture towardstowards NGNNGN

Existing networks and architectureExisting networks and architecture

TRANSIT NETWORKTRANSIT NETWORK

NATIONAL LAYERNATIONAL LAYER

REGIONAL LAYERREGIONAL LAYER

RULAYER

LEXLAYER

customersLAYER

• Hierarchical topology with 4 to5 layers, connectivity to the

upper next layer and within eachlayer as a function of economicaloptimization

• Number of nodes as a function

of O/D traffic and nodes capacity

• Service handling for media,signaling and control at allexchange nodes

•Carrier grade quality with welldefined QoS criteria andstandardized engineering rules




NGNNGN NetworkNetwork ArchitectureArchitecture

NGN Layers for all servicesNGN Layers for all services

NetworkIndependent

Services

Legacy Network

Signaling/Service

Legacy NetworkMedia




NGNNGN NetworkNetwork ArchitectureArchitecture

TargetTarget architecturearchitecture

Other

Networks

DLC

Control

Transport/Media Distributed Switching

DSL

Trunk gateway

Access gateway

Wireless gateway

Access gateway

Access gateway

Softswitch

OSS Services

PacketNetwork




NGN Architecture andNGN Architecture and

Network ElementsNetwork Elements

PBX

SoftswitchMedia Gateway

Controller

IP/XXNetwork

Intelligent NetworkAppl. Servers

Access Gateway

Access Gateway

N7 Signalling

PSTN

Access Gateway

TrunkingGateway

H.248

H.248H.248

H.248




NGN Network ElementsNGN Network Elements

• Packet networks

–Information is packetized in variable packet sizes with control headers to allow

appropriate routing and delivery – trend is to use IP based networks over various transport possibilities (ATM,SDH, WDM…)

– IP networks must offer guarantees of Quality of Service (QoS) regarding thereal time characteristics of voice

• IPv4

– Internet Protocol at network level that insert headers for each packet in orderto allow end to end packet flows: v4 is the first widely used version with 20 octetheader

• IPv6 – Internet Protocol at network level that insert headers for each packet in orderto allow end to end packet flows: v6 is the latest version with 40 octet headerand adding capabilities for current requirements in addressing and routing





• Access Gateways

– allows the connection of subscriber lines to the packet network

– converts the traffic flows of analogue access (Pots) or 2 Mb/s access

devices into packets

– provides subscriber access to NGN network and services

• Trunking Gateways

– allows interworking between classical TDM telephony network and

Packet-based NGN networks,

– converts TDM circuits/ trunks (64kbps) flows into data packets, and vice

versa




NGNNGN Network ElementsNetwork Elements

• Softswitch/MGC

– referred to as the Call Agent or Media Gateway Controller (MGC).

– provides the “service delivery control” within the network

– in charge of Call Control and handling of Media Gateways control (Access

and/or Trunking) via H.248 protocol

– performs signalling gateway functionality or uses a signalling gateway for

interworking with PSTN N7 signalling network

– provides connection to Intelligent Network /applications servers to offer the

same services as those available to TDM subscribers

• Application Server (AS): – A unit that supports service execution, e.g. to control Call Servers andNGN special resources (e.g. media server, message server).





• H.248 Protocol – Known also as MEGACO: standard protocol, defined by ITU-T, for

signalling and session management needed during a communicationbetween a media gateway, and the media gateway controller managingit

– H.248/MEGACO allows to set up, keep, and terminate calls betweenmultiple endpoints as between telephone subscribers using the TDM

• SIP – Session Initiation Protocol in order to handle communicationsignalling and negotiation like call establishment, maintenance andtermination from packet mode terminals. Has a distributed peer to peerimplementation





• Signaling Gateway (SG):

– A unit that provides signaling conversion between the NGN and theother networks (e.g. STP in SS7).

• ENUM

– Electronic NUMbering: Protocol that allows to establish acorrespondence between the traditional telephone numbering (E.164 )

and the network addresses related to the packet mode networks ( RFC

2916 "E.164 number and DNS" IETF).





• MPLS

– Multiprotocol Label Switch or protocol that assigns labels to information

packets in order to allow the node routers to treat and route flows in the

network paths according to established priority for each category. Establishes

a tunnel for an end to end forwarding. A label is a short, fixed length, locally

significant identifier which is used to identify a "Forwarding Equivalence Class"

(FEC ) to which that packet is assigned."

• LSP

– Label-switched paths: An LSP is a specific path traffic path through anMPLS network that using convenient protocols will establish a path through

an MPLS network and will reserve necessary resources to meet pre-defined

service requirements for the data path.





• OSPF

– Open Shortest Path First: A routing protocol that determines the best pathfor routing IP traffic over a TCP/IP network based on distance between nodes

and several quality parameters. OSPF is an interior gateway protocol (IGP),

which is designed to work within an autonomous system

• BGP

– Border Gateway Protocol: performs inter-domain routing in TCP/IP

networks, handling routing between multiple autonomous domains. Routers

use BGP to maintain a consistent view of the internetwork topology





Performance Issues: Scope• Quality of Service (QoS): Characterization of the service

accessibility and quality both with quantitative and qualitative (userperception) parameters and values

• Domains for QoS evaluation:

- Service accessibility: capability to access a service

- Connection establishment: Capability to get connection

- Information transfer: Quality of information delivery

- Reliability: Failure probability

- Availability: Probability of system being active

- Survivability: Capability to provide service in abnormal conditions

- Security: Information and systems protection level

- Qualitative: Intelligibility, audibility, visualization ... of information

content as derived from user perception





Performance Issues: Example ParametersTypical QoS parameter classes organized in 6 main types:

- Service accessibility: Waiting time to get service for a customer

request, measured in days or weeks (average, STD, distribution)

- Connection establishment: Loss of calls or information in a

connection measured in probability (average, STD, distribution)

- Information transfer: End to end delay, transfer delay, jitter,measured in msec. (average, STD, distribution)

- Reliability measured in failure probability

- Security measured in protection probability

- Qualitative: Intelligibility, audibility, visualization ... of information

content as derived from user perception, measured in Mean Score

of Opinion (MOS)





Performance Issues: Example Values

• Some example values

• Voice calls in circuit mode

• Call loss probability less than 0.5%, 1% or 2% per class type• Ring tone in less than 3 sec with 99% probability

• Packets• Packet loss ratio less than 10e-3

• Packet transfer delay less than 150/400/1000 msec per class type• Round-trip delay less than 400 msec• Packet jitter (delay variation) less than 10 ms

• Availability:• System or path or service available more than 99.999% of time

• Most parameters have a statistical meaning and are modeled with knownstatistical distributions like: Poisson, negative exponential,hyperexponential, self-similar, etc.

• Measured values given in: Average, STD, Percentile





Performance Issues: Application requirements

Variety of Sensitivity per application to combination of delay and loss of data(ITU Rec. G.1010)

Requirements per service/application type are a function of theapplication sensitivity to each parameter





Performance Issues. Measurements procedures

PESQ - (Perceptual Evaluation of Speech Quality). The ITU standard P.862.

It measures speech quality in the ultimate terms - customer perception.

• PESQ is the most accurate speech quality standard against which many other

speech quality algorithms are compared. It measures the effects of distortions

such as noise and delay to model and predict subjective quality. It produces voice

quality measurement scores based on the ITU Mean Opinion Score P.800.1

(MOS) scale which is representative of customers’ perceptions of quality. PESQ

has been proven to be extremely accurate and correlates highly with subjective

test results.

• PESQ measures end to end voice quality by comparing an input test signal withthe signal output, and is effective across a range of network types, including

PSTN, mobile, and VoIP.





Performance Issues: Measurement proceduresPerformance Issues: Measurement procedures

Process to quantify perceived speech quality as compared to reference signal






Perceived Quality of Service for different codecs as a function of packetloss probability (19th International Teletraffic Congress September 2005,

Beijing)





Performance Issues: Application requirementsPerceived Quality of Service for different codecs as a function of packet delay (19th

International Teletraffic Congress September 2005, Beijing)






Iso-quality curves as a function of packet delay and packet lossprobability for G.729 (19th International Teletraffic Congress

September 2005, Beijing)






Perceived Quality of Service as a function of the number of crossed domains for

the G.711+PLC coding with ppp = .01 and gold /silver SLA (19th

International Teletraffic Congress September 2005, Beijing)





Performance related issues

• Availability for all the functionalities within a public environment and

carrier-grade service still needing “some time”

• QoS guarantee for high priority flows subject to evolution and

standardization

• Security and Survivability being studied and needing more explicit and

generic solutions

• Implementation of CAC mechanisms and inter-domain negotiations with

design differences and in evolution

• VoIP across domains not standardized and very sensitive to number of

crossed domains and QoS in each one





Status today

• Available today for application in multiservice private

networks

• Optional for alternative operators that emerge with dominant

data services and starting with multiservices

• Careful planning needed for operators with existing

infrastructure and operation (migration, profitability, QoS and

survivability)





Summary of main factors

• Main advantage of NGN based on IP is the flexibility for many

services

• NGN for all services with required quality is not just IP or

internet

• Most NGN elements available today for private and small

networks

• Functionalities and performance for large public networksand multidomain interoperation requiring

agreements and some time

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