01b-qos in telecommunications networks module 1

1QOS IN TELECOMMUNICATIONS NETWORKSMODULE 1

1Property of Neotelis

Outline Warm up Quiz Introduction to QoS QoS issues in existing networks NGN concepts & IP technology QoS issues raised by NGN and IP ITU-T Recommendations (to date)


2Outline Warm up Quiz Introduction to QoS QoS issues in existing networks NGN concepts & IP technology QoS issues raised by NGN and IP ITU-T Recommendations (to date)


A Warm up Quiz Self-assessment quiz to test your knowledge For each question mark the Self-assessment

Check List as followsCheck List as followsa. You understand the question and know the answerb. You may understand the question but are unsure of the

answerc. You do not understand the question or you have no idea

what the answer may be Add up your a, b and c scores and save for


comparison later Quiz answers at the end of the week!

3Outline Warm up Quiz Introduction to QoS QoS issues in existing networks NGN concepts & IP technology QoS issues raised by NGN and IP ITU-T Recommendations (to date)


Introduction to QoS The networks of today are composed of a multiplicity

of elements both for the core transport and the distribution networks.

Complexity is the name of the game for operators, simplicity for the end-users! (Norman Rae, 2009)

To succeed in todays competitive environment, telecom operators must focus on price, reliability and quality of service. These elements are essential to provide customer satisfaction


This is a quick technology recap to put a context to Quality of Service (QoS)

4Introduction to QoS Public Switched Telephone Network (PSTN)

originally based on copper wires & analog technology

today based on digital technologies, such as ISDN (Integrated Services Digital Network) and more recently on IP technology

includes the set of all the traditional telephone lines and associated infrastructure

includes switching systems, transmission lines for both local and long distance and multiplexing


g p gequipment

must include numbering plans, back-office systems, customer support, etc.

Introduction to QoS The circuit switched wired network

Transit switch Transit switchInter switch

Local switches

Local switches

switch trunks

Transit switch


Telephone networks use telephone numbers to enable one party to connect to another, whether it is local, national or international . Area codes and country codes are included as required as well as numbers that indicate whether a call is local or long distance. E.164 is the ITU standard that regulates this, with NANP being the exception applying to the USA, Canada and the Caribbean.

5Introduction to QoS The circuit switched mobile network

CO Local switch

MSC

MSC

switch

MS

MS BSS

BSC Fixed network


Mobile networks for the PSTN are essentially similar except: they have Mobile Switching Centers (MSCs) connection to the mobile subscriber (MS) is wireless trunks are required to interconnect to the fixed network COs

Introduction to QoS Typical PSTN or circuit switched services

End-to-end callCall set up call cleared call waiting voice mail etc Call set-up, call cleared, call waiting, voice mail, etc

Facsimile Connectivity to Internet Connectivity to mobile Long distance call Conferencing


g Video Payphone

etc.

6Introduction to QoS Public Switched Data Network (PSDN)

Data networks existed either as telegraphy (point to point at first) and then evolved to Telex and TWX (circuit switched public networks for the purpose of transmittingswitched public networks for the purpose of transmitting the written word) and eventually FAX (their replacement)

Packet switching A communications method in which packets (discrete

blocks of data) are routed between nodes over data links shared with other traffic

In each network node, packets are queued or buffered, l bl d l


resulting in variable delay As opposed to circuit switching, there are no fixed and

dedicated hard connections between nodes for their exclusive use of the communicating parties

Introduction to QoS Packet switching 1st generation

This first generation was connection oriented and emerged from the ITU in the mid 1970s under the Xemerged from the ITU in the mid 1970 s under the X series of protocols including the well known is X.25

These networks provided guaranteed packet delivery with built in error detection, retransmission etc. and were process intensive and lacked the speed that we know today

X.25 networks were modified to increase efficiency &


throughput with FRAME RELAY

7Introduction to QoS Packet switching 2nd generation

This is what we know mostly today (based on the Internet Protocol or IP); it evolved from the IETF efforts with practically a complete connectionless approach

IP networks do not provide guaranteed packet nor error detection, retransmission etc. in the sense of the first generation

The principle is one of the datagram that carries its own destination address (like a letter)

Includes a virtual connection mode which requires call


establishment for setting-up virtual paths for specific communicating parties requirements

Introduction to QoS Packet switching

Packets are sent independently and may or may not follow the same route which create the need for proper sequencing,delay and quality issues

1

2

34


Packet network

8Introduction to QoSComparison of switching techniques

Circuit switching Packet switchingDesigned for voice originally and hence for real-time traffic Difficult to adapt to any type of trafficPhysical connections established and used

Designed for data and not for real-time traffic (voice and video) Capable of transporting any type of trafficAny connections that may exist are logical


Physical connections established and used whether idle or not until call releasedUtilization of network resources not very efficientSecurity and quality are not real issues

Any connections that may exist are logicalMuch better utilization of network resourcesPackets may be delayed to varying degrees or even get lost (discarded)Special measures are required to address issues of Quality of Service (QoS) and security

Introduction to QoS Asynchronous Transfer Mode (ATM) is a high

speed packet switching system based on fixed packets (cells) also known as Cell Relay servicep y

ATM objective was to transport with high reliability and quality guarantees, on a single network, real-time video conference and audio as well as image files, text and email

It is an advanced connection-oriented packet-like switching for high-speed multiplexing and switching with improved error control & simplified flow control


2 groups, the International Telecommunications Union and the ATM Forum were involved in the creation of the standards

9Introduction to QoS ATM Cell Relay advantages

High capacity support for voice, video, data and images Supports fixed and variable throughputs Provides bandwidth-on-demand Supports current technologies, independently of the

application Enables a large number of users to share applications

such as: Teleconferencing, telemedicine, real-time collaboration,

video-on-demand and HDTV, distance learning,


high-speed data transfer Because of high costs, ATM is now slowly giving way to

IP/MPLS based networks

Introduction to QoS Private networks and Customer Premise

Equipment (CPE) have an influence on QoSphysically located on the customer site physically located on the customer site

may be simple terminal equipment or may constitute networks that may be privately owned and operated by the customer or owned and operated by the service provider; e.g.

Telephones; switches; routersVid f t


Videoconference systems Computers; facsimile

- etc.

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Introduction to QoS Typical private networks

Local Area Network (LAN)

S i h

AZ


Switch

Introduction to QoS Typical private networks

Private Branch eXchange (PBX)

PBX PSTN

In-House Lines

Outside Lines (trunk to CO)


11

Introduction to QoS Private networks that are part of the public

networksThese networks dedicated and designed to These networks dedicated and designed to satisfy the specific needs of the organization e.g. Virtual Private Networks (VPN)

Company site A

Company site B

Public Network


Company site C

Public Network

Introduction to QoS Transmission & distribution

The traditional copper line is no longer a telcos bottleneck to service evolution as a result of Digital Subscriber Line or DSL (major competition is fibre and coaxial cable high speed access) and is implemented worldwide

Limitation of bit-rate a function of distance Several services can share the same access :

data, video, voice (fixed or mobile) Access traffic increase pushes demand for higher

speeds


speeds Note that the demand for broadband capacity is

also true for mobile on account of multimedia services

12

Introduction to QoS Transmission & distribution : DSL

Voice switch

C i

Voice switchPSTN

Voice trunk

ClientEntry filter

FilterS i ModemCopper pair PC10/100BT

switch switchATM

network DSLAMMicro-filter

Micro-filters are usedinstead of entry filters

Service Provider

Modem

Service Provider


instead of entry filtersfor residential clients

router routerIP/MPLSnetwork

IP DSLAM

Service Provider

Introduction to QoS Transmission & distribution

Illustration of typical maximum ranges for speed and distance from C O for ISDN ADSL

ISDN: 128 Kbps 5 5 km

ADSL: 8 Mbps / 800 kbps 3 to 4.5 km

VDSL: 13/1 Mbps

13

Introduction to QoS Fiber technology in the access

Point-to-point (expensive) Active Optical Network (AON)

PON using WDMPON using TDM


PON = Passive Optical Network

Introduction to QoS Wireless Transmission: Point-to-point

microwave Considerations

E th t Earths curvature Antenna height Obstacles in path Fresnel zone clearance

Antenna Obstacle clearance

Fresnel Zone Clearance Antenna height Antenna

height


The Fresnel zone is a three-dimensional ellipsoidal volume between transmit and receive antennas within which diffraction (due to

obstacles) will significantly impact transmission

Earth Curvature

g

14

Introduction to QoS Satellite communications

Wide area coverage but issues due to propagation delayp p g y

Space Segment

Satellite

Earth Stations

Coverage Region


Ground Station

Customer Premises

NationalNetwork Regional

Network

Introduction to QoS Mobile or Cellular: the principle

Wireless base stations distribute the signal to subscribers and are linked to Mobile Switching Centers (MSCs)Th b t ti tit t ll d h d The base stations constitute cells and a handover mechanism is key to handle calls to mobile subscribers

The mobile networks are interconnected to the fixed PSTN and other mobile networks


MSCPSTN

Control Equipment

Control Equipment

15

Introduction to QoS First generation technology (1G)

AMPS, TACS (analog)Second generation technology (2G)

Increasing speeds of

transmission

Second generation technology (2G) TDMA , CDMA , GSM (digital) Packet technology (2.5G): GPRS, EDGE

Third generation technology (3G) UMTS (WCDMA )


CDMA 2000 etc. Super 3G, 3.5G, 3.75G

Fourth generation technology (4G) ?

Circuit Switched PLMN Core

MSC

MSC

Introduction to QoS

BSCBTSPSTN or PLMN

GGSN

IP transport

MGW

MGW

IP MPLS Packet Switched Core

Evolution of mobile with packet technology


HLRMSC Server

SGSN IP Networkpacket technology

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Introduction to QoS Fixed wireless: Wi-Fi

Used for wireless hotspots linked to the Internet via broadband; each individual hotspotInternet via broadband; each individual hotspot covers up to about 100m

Internet

Cross Roads

Airport

University


SME

Cafe

SOHO

Introduction to QoS Fixed wireless: WiMAX

Broadband wireless distribution over wide areas Hotzones: area of coverage of tens ofHotzones : area of coverage of tens of

kilometres radius

Cross Roads

Airport

University

InternetWiMAX

equipped


SME

Cafe

SOHO

Airport

WiMAX

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ARPANET SNAX.25

ETHERNET FRAMERELAY

INTERNET Rightsreleased; WWW

Introduction to QoS Technology evolution

1960

1970

1980

1990

2000

ETHERNET RELAY

1ST ATM NETWORK

FASTETHERNET

GIGABITETHERNETPC

Summary ti li f k

MOBILE


ETHERNET

SONETFiber OpticsDIGITAL

SWITCHINGISDN

timeline of key developments

Introduction to QoS The need for QoS

Todays networks support an increasing number of applications and transport all types of information:applications and transport all types of information:

Voice, audio Videoconferencing, video on demand Gaming and interactive applications E-mail, SMS E-commerce, online banking FTP, web browsing, etc.


Mechanisms are required to manage network resources in order to ensure suitable Quality of Service for each application

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Introduction to QoS Definitions

Service: A pre-defined type of treatment during transmission p e de ed type o t eat e t du g t a s ss o

across a network, usually quantitative:- Delay- Delay variation- Information loss probability- Throughput- Maximum transfer unit (MTU)- Priority

Q lit f i i l Q S


Quality of service now simply: QoS A defined level of performance for a given service

Class of service A grouping of one or more qualities of service

Quality of Service (QoS) Definition in telephony

ITU standard X.902 is A set of quality requirements on the collective behaviour of one qor more objects. It comprises requirements on many aspects of a connection, i.e.

Service response time Service loss Signal-to-noise ratio Crosstalk


Echo Interrupts Frequency response Loudness levels

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Quality of Service (QoS) Definition for packet switching

QoS refers to resource reservation control mechanisms rather than the achieved service quality

The ability to provide different priority to different applications, users or data flows

To guarantee a certain level of performance to a data flow in terms of:

Bit rate Delay Jitter


Packet dropping probability Bit error rate

Important if network capacity is insufficient; irrelevant in the absence of congestion

Quality of Service (QoS) Definition subject to discussion

Business metric that reflects or predicts quality that is subjectively experiencedthat is subjectively experienced

Quality of Experience (QoE) User perceived performance Degree of satisfaction Number of happy customers Mean Opinion Score (MOS)

Cumulative effect on subscriber satisfaction of


Cumulative effect on subscriber satisfaction of all imperfections affecting the service

20

Introduction to QoS Various perceptions


Introduction to QoS Probably the best definition is the

following, since what counts is the customers perception of being satisfied:custo e s pe cept o o be g sat s ed

Quality of service (or simply QoS) is the level of performance for a given service

From the viewpoint of service providers network, QoS is the ability to service an application efficiently, without affecting its function or performance and provide


function or performance and provide predictable quality of service

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QoS issues in existing networks Several factors to consider

Human Factors Individual perception of audio/video quality, lack of

t i i t th t ff ti ltraining to use the system effectively, Important factors are: service availability & stability,

promptness to answer customer queries, accuracy of information, etc.

Technical factors involve Reliability, Scalability, Effectiveness, Maintainability

Network Factors includeD l jitt k t l th h t


Delay, jitter, packet loss, throughput, Device Factors include such items as

endpoints, gateways, routers, firewalls, network address translation, processor, memory,

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QoS issues in existing networks

Basic problems that have existed from day one in telephony with respect to quality in

l t kanalog networks Echo Singing Delay Distortion

Noise


Noise

QoS issues in existing networks

In Digital networks, the basic telephony problems that affect QoS are generally

l Delay Jitter BER (Bit Error Rate) The problems of echo and distortion are also still

present The big advantage of digital technology is


g g g gythe ability to eliminate noise as well as detect and correct errors through a variety of techniques

23

QoS issues in existing networks QoS considerations for IP real-time traffic

involve many elements which are most often a result of insufficiency of resourcesoften a result of insufficiency of resources and queuing, e.g.

Throughput Delay (latency) Loss (of packet) Jitter (variation of delay)

Error rate


Error rate Sequence errors Echo Blocking

QoS issues in existing networks Networking devices and queuing

General switching architecture


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Introduction to QoS Input functions

Given a packet (datagram) destination, lookup output port using forwarding table in input port memory, with the goal to complete input port processing at line speedcomplete input port processing at line speed

Other processing: classification, marking, shaping Queuing becomes necessary if packets arrive faster than

forwarding rate into switch fabric


Physical layer:bit-level reception

Data link layer:e.g. Ethernet

Queuing determination

Introduction to QoS Output functions

Buffering required when packets arrive from switch fabric faster than the transmission rateQueue management needed e g how to manage overflow

Data linkprocessing(protocol,

Queue management needed, e.g. how to manage overflow Scheduling needed e.g. how to order transmissions based on

traffic classification, marking, etc.


Physical layer:bit-level encoding

Data link layer:e.g. Ethernet

encapsulation,fragmentation)

Queuing management

25

QoS issues in existing networks Networking devices (blocking)


QoS issues in existing networks Packet loss and delay (in routers)

Often the packet arrival rate exceeds the output capacity Packets are placed in output queues and wait to be sent

f h f ll k b d d

B

Router

If the queue is full, packets may be dropped (this is called the tail drop)

Packet being sent (delay) Next router


A Packets in queue (delay)Output queue: packets may be dropped (loss) if queue is full

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1. Processing delay Check bit errors

2. Queuing Time spent in the output

Sources of packet delayQoS issues in existing networks

Check bit errors Reassembly Forwarding table lookup Move to output link

p pqueue waiting to be sent

Depends on queue depth, link speed, queue service

Serialization

B


PropagationProcessing Queuing

A

3. Serialization delayTime required to put

4. Propagation delay:Time required to move

Sources of packet delayQoS issues in existing networks

Time required to put bits on the wire

Depends on link speed

Time required to move signal from one end to the other

Depends on distance

Serialization

Bt1 t2


PropagationProcessing Queuing

ADelay

= t1 + t2

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QoS issues in existing networks Processing delay

Usually negligible e.g. a few microseconds Queuing delay Queuing delay

Significant when networks are congested e.g. up to tens of milliseconds

Serialization delay e.g. 10 ms but significant on slow links

Propagation delay


Propagation delay Significant on international and satellite links

e.g. up to 50 milliseconds (200 milliseconds or more for satellite)



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NGN concepts

Legacy networks and the services they provided were Analog

PBXDigital Phones

ptightly linked

Key System

Analog Telephone

Analog FAX

Class 4/5

Switch

Voice Network

Router ServersATM

Switches

Little or no flexibility


PC Client

Ethernet Switches

Frame Relay Switches

Router

Data NetworkLittle or no flexibility

existed to carry services other than those for which the

network was designed

NGN concepts & IP technology Still today:

Convergence of services and applications is often difficult where networks use inherently different technologies

Telephone, cable, mobile, wireless, satellite and now Wi-Fi and WiMAX

There is complexity, lack of integrated mobility features and lack of seamless inter-working between various end-user communication devices

The capital intensive nature of building or expanding networks, especially in areas of low population density

h b d i il d i f


cause these areas to become underprivileged in terms of service availability

29

NGN concepts & IP technology IP architecture evolution

Legacy networks: separate networks for different services

PSTN (POTS)(TDM-based)

Interconnection

SS7PSDN (DATA)

(TDM-based, dedicated, message or packet

switched)


Narrowband access Broadband access

xDSL

POTS/ISDNDial-up H.323/SIP

Enterprise customers LAN

3G


Mobile networks only made things more difficult

PLMN (mobile)

3G (cellular)

PSTN (POTS)(TDM-based)

Interconnections

SS7 PSDN (DATA)(TDM-based, dedicated,

message or packet switched)

Interconnection


Narrowband access Broadband access

xDSL

POTS/ISDNDial-up H.323/SIP

Enterprise customers LAN

?

30

NGN concepts & IP technology NGN is a generic wording created in 1998 by

telecom-minded people in the US to designate a multi-service network architecture somehow differentiated from what the Internet was at that time

An Internet Protocol (IP) based infrastructure similar to Internet but not limited to best effort use of IP

An architecture and the necessary control devices


An architecture and the necessary control devices to enable valuable real-time communication services over the network(s)

NGN concepts & IP technology The following characterize NGNs:

1. A common transport architecture: based on high speed transparent digital technologyhigh speed, transparent, digital technology

2. A distributed architecture (as opposed to the tightly linked nature of legacy networks)

3. A layered structure with open standards: essentially all NGNs tend to have different planes addressing the transport and access, the media (the actual information) the control


the media (the actual information), the control (signalling etc.) and the services

31

Softswitch Service LayerApplications Servers

NGN concepts & IP technology NGN Architecture

Access & Transport Layer

Media Layer

Control Layer

PSTN/PLMN

IMS UMTS

AGW

TGW

IPX

RGW

Softswitch Service Layer Servers

Media Server

AGW


Enterprise customersRemote office/SOHO

Residentialusers

Access

LAN3G mobileusers

Broadband access

NGN concepts & IP technology ITU-T definition of NGN (Y.2001)

A packet-based network able to provide telecommunication services and able to make

f l l b db d bl duse of multiple broadband, QoS-enabled transport technologies and in which service-related functions are independent from underlying transport-related technologies

It enables unfettered access for users to networks and to competing service providers and/or services of their choice


a d/o se ces o t e c o ce It supports generalized mobility which will allow

consistent and ubiquitous provision of services to users

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From tightly linked to distributed architecture!

SwitchingMatrix

Service Delivery & Connection

Control IP or ATMTrunking Gateways

Softswitch

Access Gateways

IP Terminals


Traditional (CS) New (IP)

Elements tightly linked together more often than

not with proprietary methods

Distributed elements working together based on open standards and protocols

NGN concepts & IP technology Softswitches

Next-generation switches are known as softswitches because they are predominantly software driven servers

They are the most flexible platforms available, combining substantial scalability, remote management and diagnostics, and are designed to be highly reliable

They are now replacing the legacy class 4 (transit) and class 5 (local exchange) PSTN switches


These switches have also been replacing traditional mobile switching centres in cellular networks

33

NGN concepts & IP technology Typical Softswitch

Carrier grade system that can scale up to handle large traffic volumes e.g. over a million Busy Hour Call Attempts (BHCA)

Supports a wide range of signalling, transport and control protocols for line gateways and in support of multimedia traffic i.e. classical data as well as digital voice and video

Represents a new breed of switching


systems Often include both circuit and packet

switching to ease network transition

NGN concepts & IP technology Gateway

Gateways carry functional transformations between different networks e gbetween different networks , e.g.

Between circuit & packet networks) Different types of gateways exist as well as

various levels of integration Trunking: telephone to IP networks Residential: analog and VoIP networks Access: analog/digital PBX and VoIP networks


Access: analog/digital PBX and VoIP networks Gateways carry out call processing, e.g.

Signalling to circuit switching IP signalling to IP network (H.323)

34

NGN IP components Media Gateway

Converts digital media streams between disparate telecommunications networks for end-to-end operability between IP-based networks, PSTN, mobile networks, etc.

IP telephony gateway Converts real-time media between circuit and packet

switched networks Ensures inter-working of signalling Initially deployed by long distance operators to extend

Internet telephony for Least-Cost Routing (LCR)


Internet telephony for Least-Cost Routing (LCR) Gateway to place calls on packet networks Realizes efficiency, cost savings and features of packet

switched networks

NGN concepts & IP technology Router

The workhorse of IP networksRouters receive and forward packets Routers receive and forward packets according to their IP destination address

Most of packet delays in an IP network originate from routers processing, output link selection, queuing, etc.

Congestion can cause packet loss


35

NGN concepts & IP technology Router functions

Routers are used to connect LANS through a Wid A N kWide Area Network (WAN) such as an IP network e.g. the Internet

Routers use IP addresses to forward packets to their destinations (do not

IP Network


destinations (do not route on MAC addresses)

Router

NGN concepts & IP technology IP routing

Is based on the final destination e.g. D Packets are forwarded hop by hop i.e. from one router to p y p

the next based on the entries in their routing table Routing tables in routers are filled or updated by routing

protocols e.g. RIP = Routing Internet protocol; OSPF = Open Short Path First (one of the best); Others: EGP, BGP, IGRP etc.

D


IP NetworkD

36

NGN concepts & IP technology Router architecture

Control PlaneExchanges routing information with other routers i.e.

signalling

Forwarding planeDirects outbound

packets to the appropriate interface

Routing Engine

Routing Table

ForwardingTable

The routing logic


NGN concepts & IP technology No unique format in routing

tables As a minimum should contain

Routing Table for R1

Destination address Next Hop Interface

Address of a destination IP address of the next hop router Network interface to be used

A Directly connected 1

B Directly connected 2

C Directly connected 3

D R2 3E R2 3F R2 3


F R2 3

A

F

D

E

BC3

4 3

11

2

2

R2R1

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NGN concepts & IP technology Application Servers

An application server is a software engine that delivers applications to client computers ordelivers applications to client computers or devices, typically through the Internet and using the HyperText Transfer Protocol

Application servers are distinguished from web servers by the extensive use of server-side dynamic content and frequent integration with d b


database engines (Wikipedia definition)

NGN concepts & IP technology Putting the pieces together

H bSMTP server

DNS server

HubHubserver

SwitchDHCP Server


LANLANLANLAN LANLAN

Web server

FTP server

38

NGN concepts & IP technology The Internet has evolved and become more

complex as it has permeated various networks and has been used more extensively by carriers and y yservice providers alike. Private networks have also multiplied in a way parallel to the PSTN with LANs as opposed to PBXs. Here we have a look at

Tier-1 Internet Service Providers (ISPs) Tier-2 ISPs Tier-3 ISPs


Typical packet path

Roughly hierarchical with tiers i.e. sizes Tier-1 ISPs have national and international coverage (e.g.

AT&T, Sprint, BT, France Telecom)

NGN concepts & IP technology

Tier-1 ISPs interconnect

privately Tier-1 ISP

NAPTier-1 ISPs

interconnect at public Network Access Points

(NAPs)


Tier-1 ISP Tier-1 ISP

39

Tier-2 ISPs: Smaller (often regional) ISPs Connect to one or more Tier-1 ISPs & other Tier-2 ISPs

Ti 2 ISPTier-2 ISPs


Tier-1 ISPTier-2 ISPTier-2 ISP

Tier-2 ISP pays Tier-1

ISP for connectivity

to rest of Internet

Tier-2 ISP is a customer of Tier-1 ISP

peer privately with each

other, interconnect at NAPs and

P-NAPs


Tier-1 ISP

Tier-2 ISP

Tier-2 ISPTier-1 ISP Tier-1 ISP

Tier-2 ISP

localISP Tier 3

NGN concepts & IP technology Tier-3 ISPs and local ISPs

Last hop (access) network (closest to end systems/users)

local

Ti 1 ISP

Tier-1 ISP

Tier 1 ISP

Tier-2 ISPTier-2 ISP

ISP Tier-3ISPLocal and

Tier-3 ISPs are clients ofhigher Tier ISPs that

connect them to the rest of

Internet

ocaISP Tier-3

ISP




Tier-2 ISP

Tier-3ISP local

ISPTier-3

ISP localISP

Tier-3ISP local

ISP

40

local

NGN concepts & IP technology A packet will be transported through many networks

Tier-1 ISPTier-2 ISPTier-2 ISP

localISP Tier-3

ISPlocalISP Tier-3

ISP

Tier-3ISP

localISP

Inherent to the structure, technical

issues arise for Quality of Service (QoS) and Security




Tier-2 ISP

Tier-3ISP local

ISP

Tier-3ISP local

ISP

NGN concepts & IP technology In view of the above, the need for QoS is

evident:Networks are converging bringing together transport Networks are converging bringing together transport facilities serving numerous applications with varied requirements

Networks are multi-layered and heterogeneous The unifying technology is IP but it was not designed

originally for isochronous traffic QoS therefore has to be implemented in and by the


QoS therefore has to be implemented in and by the various levels of IP protocols

41

NGN concepts & IP technology Standards

(Set of rules) govern data transmissions and telecommunications between computers ortelecommunications between computers, or between computers and other computer-related devices

Protocols Ensure that the sending end and receiving

end are, in effect, speaking the same l i h l


language or using the same language rules

NGN concepts & IP technology The world of telecommunications is complex and

to make it work, many organizations work on standards thus ensuring that networks and gservices function properly. Main ones:

ITU (International Telecommunications Union) ISO (International Organization for Standardization) IETF (Internet Engineering Task Force) IEEE (Institute for Electrical and Electronics Engineers) ETSI (European Telecommunications Standards Institute)


TISPAN (Telecoms & Internet converged Services & Protocols for Advanced Networks)

TIA (Telecommunications Industry Association)

42

NGN concepts & IP technology ISO Model: the need

The multiplicity of networks and the arrival of IP software driven technology and the abundance of new protocols have caused increased complexity in every network element

The boundaries between core, edge and access networks are sometimes blurred

As a result it became imperative to have a common reference for a wide variety of networks and is an essential framework for interoperability (networks and

i )


equipment) ISO started on this in the mid-seventies basing

themselves on a model by IBM (SNA)

NGN concepts & IP technology Three important elements of the model

Services (functions): what a layer does Interfaces: how each layer provides a set of functions to y p

the layer above and how it relies on the functions of the layer below

Protocols: the rules by which each layer communicates with its peer layer on another node by sending messages back and forth

System A System B


Layer n+1 Layer n+1

Layer n Layer nInterface Protocol

43

NGN concepts & IP technology Standards and protocols

OSI 7-layer model TCP/IP modelApplication Voice, video and data services such as VoIP, IPTV video streaming e mail file transfer and ApplicationIPTV, video streaming, e-mail, file transfer and

facsimile

Presentation Data formatting and encryption

Session Establishment and maintenance of sessions (e.g. SIP)Transport End-to-end delivery (e.g. TCP, UDP)

Network Routing and switching of packets (e.g. IP), establishment of source to destination path

(groups layers 5,6,7)

Transport

Network


establishment of source to destination path

Data link Transfer of units of information, framing and error checking, multiplexing and multiple access

Physical Modulation of binary data over the medium, definition of electrical and mechanical standards

Data link

Physical

NGN concepts & IP technology TCP/IP ensemble of protocols

Application: supporting network applications

FTP SMTP STTP application FTP, SMTP, STTP Transport: host-host data

transfer TCP, UDP

Network: routing of datagramsfrom source to destination

IP, routing protocols Data link: data transfer between

application

transport

network

data link


neighbouring network elements PPP, Ethernet

Physical: bits on the wirephysical

44

NGN concepts & IP technology TCP/IP architecture

The TCP/IP architecture includes a number of protocols (here the wireline version is shown)

Others SMTP TELNET FTP NFS TFTP SNMP BOOTP Others

TCP UDP

BGP EGP ICMP RIP OSPFEGP IGP

application

transport

network

Many protocols have been added since real-time traffic is transported today


ARP RARP IP

802.2 PPP SLIP

802.3 802.5Ethernet FDDI Serial Link

network

data link

physical

NGN concepts & IP technology Layers implementation

Devices implement layer functions Devices perform actions,

exchange messages with peersEach layer has its roleapplication Each layer has its roleapplication

transportnetwork

linkphysical

applicationtransportnetwork

networklink

physical


linkphysical application

transportnetwork

linkphysical


linkphysical

45

TCP/IP Model


Client for Microsoft Networks

D-Link DFE-530TX PCI Fast Ethernet Adapter

TCP/IP

File and printer sharing for Microsoft Networks

Layers 1 and 2Layers 3 and 4

Every device (PC, mobile handset etc.) that works with IP will contain the

appropriate TCP/IP


appropriate TCP/IP protocol layers

NGN concepts & IP technology Transport Layer

Takes data from layer above Adds addressing, reliability check

information to form datagram Sends datagram to layer belowapplication

dataSends datagram to layer below

Waits for feedback (e.g. acknowledgement)transportnetwork

linkphysical


networklink

physicaldata

transport

ack


linkphysical application

transportnetwork

linkphysical


linkphysical

data

transport

46

NGN concepts & IP technology Sending a message (in a packet)

Each layer takes data from aboveAdds its own information (e g header)

applicationtransport

t k

applicationtransport

t k

Source DestinationMMM

H tHH

MMM

H tHH

messagesegmentdatagram

Adds its own information (e.g. header) Passes the new data unit to the layer below


networklink

physical

networklink

physical

MM

H tHnH tHnH l

MM

H tHnH tHnH l

datagramframe

packetsegment

datagramframe

Sourceapplicationtransportnetwork

linkHtHnHl MHtHn MHt M

M

Switch


Packet (Message) Handling

physical

linkphysical

HH M

HtHnHl M HtHnHl M


Destinationapplicationtransportnetwork

linkphysical

HtHnHl MHtHn MHt M

Mnetwork

linkphysical

HtHnHl MHtHn M

HtHnHl MHtHn M

Router

47

NGN concepts & IP technology TCP service

Connection-oriented: set-up required between client and server processesReliable transport between sending and receiving process Reliable transport between sending and receiving process

Flow control: sender will not overwhelm receiver Congestion control: throttle sender when network is overloaded Does not provide: timing or minimum bandwidth guarantees

UDP service Unreliable data transfer between sending and receiving

processesDoes not provide: connection set up reliability flow control


Does not provide: connection set-up, reliability, flow control, congestion control, timing or bandwidth guarantee

NGN concepts & IP technology Transport layer

uses same Network layer communication channel between hosts for several applications

Transport Transport

HTTPFTP

multiplexing and demultiplexing is achieved by using sockets:

TCP socket: source IP address, source port, destination IP address, destination port

UDP socket: destination IP address, destination port


Transportlayer

Networklayer

Transportlayer

Networklayer

FTPTELNET

48

ApplicationApplicationlayer protocol

Underlyingtransport protocol

NGN concepts & IP technology Some applications and their transport protocols

Application

e-mailremote terminal access

Web file transfer

streaming multimedia

layer protocol

SMTP [RFC 2821]TELNET [RFC 854]HTTP [RFC 2616]FTP [RFC 959]

e.g. RealPlayer

transport protocol

TCPTCPTCPTCP

UDP or TCP


gInternet telephony

g ye.g. Skype UDP

NGN concepts & IP technology TCP and UDP transport layer protocols

TCP: Transmission Control ProtocolReliable in order delivery Reliable, in-order delivery

Some congestion control Flow control Connection set-up

UDP: User Datagram Protocol Unguaranteed, unordered delivery No-frills extension of best effort IP


No-frills extension of best effort IP Both provide for multiplexing/demultiplexing

between Layer 5 and Layer 3

49

NGN concepts & IP technology VoIP protocols in the TCP/IP modelISO Model Layer Protocols or Standardsy

Presentation Applications / CODECs

Session H.323 and SIP

Transport RTP / UDP / TCP

Network IP Non QoS


Data Link FR, ATM, PPP, Ethernet

NGN concepts & IP technology Voice over IP protocols

SIP Stands for Session Initiation Protocol

Si li t l f i iti ti i d Signaling protocol for initiating, managing and terminating voice and video sessions across packet networks

RTP Stand for Real-time Transport Protocol Provides end-to-end network delivery services for the

transmission of real-time data RTP is network and transport-protocol independent


RTP is network and transport protocol independent, though it is often used over UDP

It is the de facto standard media transport protocol on the Internet

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Location #1 Location #2Traditional networks

QoS issues raised by NGN & IP

PSTN

WAN

Leased line

PABX


Leased lineHost

Controller

51

Location #1 Location #2

Converged networks (NGNs)

QoS issues raised by NGN & IP

WAN

PABX


Host

Packets compete for bandwidthCritical applications need priorityVoice traffic is delay-sensitive

QoS issues raised by NGN & IP Issues in NGN and Packet networks

Although the situation is improving, the public Internet lacks QoS guarantees (primarily due toInternet lacks QoS guarantees (primarily due to limits in router computing power)

Problems encountered as packets travel from origin to destination


52

QoS issues raised by NGN & IP Issues with NGNs (converged networks)

Lack of bandwidthTraffic types compete for limited bandwidth Traffic types compete for limited bandwidth

Total end-to-end delay Data travels through multiple networks, devices and

links, each add an incremental amount of delay Delay jitter

The total amount of delay to traverse the converged network varies according to network congestion


network varies according to network congestion Packet loss

Packets may be discarded when network congestion reaches a certain level

QoS issues in existing networks Dropped packets

The routers fail to deliver some packets Packets arrive when buffers are already full Impossible to determine what will happen in advance The receiving application may ask for this information

to be retransmitted, possibly causing severe delays in the overall transmission

Delay It might take a long time for a packet to reach its

destinationP k t t h ld i l t k l di t


Packet gets held up in long queues or takes a less direct route to avoid congestion

In some cases, excessive delay can render an application, such as VoIP or online gaming, unusable

53

QoS issues raised by NGN & IP This leads to quality issues which show

themselves in different ways depending on the application:the application:

Voice packets may be delayed or dropped Talker overlap Voice gets clipped or disappears

System response is slow Slow screen refreshes Spongy keyboard effect Slow application responses


Video packets may be delayed or dropped Image jerks and unsynchronized voice Black squares in images, etc.

QoS issues raised by NGN & IP In last 5-10 years a lot of effort has been

applied to solve QoS issues that had slowed down deployment of real-time services ondown deployment of real-time services on IP networks

Extensive research was spearheaded by MCI since the 1980s

This research was carried out to look into the factors that affect quality of service of


the factors that affect quality of service of real-time transport on data networks that were primarily not designed for real-time traffic

54



ITU-T Recommendations The ITU and other standards organizations have

been active in pursuing issues of quality both from the traditional networks and the NGns

In the field of telephony, QoS was defined in 1994 by ITU-T Recommendation E.800

Support Operability Accessibility Retainability


Integrity Security

55

ITU-T Recommendations In the field of data networking, ITU

published ITU-T Recommendation X.641Provides concept and terminology Provides concept and terminology

Main QoS related IETF RFCs: RFC 2474: Definition of the Differentiated

Services field RFC 2205: Resource ReSerVation Protocol (RSVP) RFC 2990: Next steps for the IP QoS architecture


RFC 2990: Next steps for the IP QoS architecture RFC 3714: IAB concerns regarding congestion

control for voice traffic in the Internet

ITU-T Recommendations ITU Series E

Overall telephone service, service operation and human factorshuman factors

ITU-T Recommendation E.721 Network grade of service parameters and target values

for circuit-switched services in the evolving ISDN ITU-T Recommendation E.723

Grade-of-service parameters for signaling system no. 7 networks


7 networks

56

ITU-T Recommendations ITU Series G

Transmission systems and media, digital systems and networkssystems and networks

ITU-T Recommendation G.107 The E-model, a computational model for use in

transmission planning ITU-T Recommendation G.108 Amendment 2

Planning examples regarding delay in packet-based networks


networks

ITU-T Recommendations ITU Recommendation G.108

Provides guidance for the transmission planner on how to deal with the delay occurring in packet-based networks in conjunction with VoIP terminals and gateways

For illustration purposes, the following scenario has been investigated:

Two VoIP terminals interconnected via a packet-based network that complies with ITU-T Rec. Y.1541, Class 0 (100 ms)

In addition, two CODECs, G.711 and G.729A have been considered while no other impairments have been


considered, while no other impairments have been considered (proper echo control assumed)

The network delay is composed of the fixed delay and the value of the delay variation (jitter)

57

ITU-T Recommendations For the E-model calculations, three different cases

of terminal delay have been investigated Case 1: IP terminal send delay = 20 ms, IP terminal y ,

receive delay = 30 ms, total delay = 150 ms, R=90: Users very satisfied


ITU-T Recommendations For the E-model calculations, three different cases

of terminal delay have been investigated Case 2: IP terminal send delay = 35 ms, IP terminal y ,

receive delay = 65 ms, total delay = 200 ms, R=86: Users satisfied


58

ITU-T Recommendations For the E-model calculations, three

different cases of terminal delay have been investigatedinvestigated

Case 3: IP terminal send delay = 50 ms, IP terminal receive delay = 100 ms, total delay = 250 ms, R=79: Some users dissatisfied


ITU-T Recommendations Real-time issues for softswitches

Voice service performance standards are described in terms of blocking and delay requirements that apply to the entire switching system regardless of the hardware or software implementation

The key requirements that should be applicable to softswitches as a Class 5 or Tandem replacement:

Dial tone delay (measured during ABSBH) Average dial tone delay < 0.6 s Probability (dial tone delay > 3 s) < 1.5%


Probability of cut-off calls < 0.000125 Probability of ineffective attempts

59

ITU-T Recommendations ITU G.114 - end-to-end delay

Time during which voice signals travel across the network Sum of delays required for a voice signal generated by the y q g g y

speaker's mouth to cross the different network devices and links in order to reach the listener's ear


ITU-T Recommendations Voice quality standards have already been

established by the ITU over and above the MOS scale of perceived quality:

P.861 in an attempt to estimate MOS using quantifiable measurements that can be automated

PSQM (Perceptual Speech Quality Measurement) is primarily for optimizing individual networks and NOT for comparing quality in different networks

PSQM does not map to MOS and does not account for factors encountered in IP networks such as packet loss or


bit errors

01b-qos in telecommunications networks module 1

Documents

qos qos issues

qos typical pstn

quiz introduction

ip itut recommendations

distribution networks

assessment quiz

quick technology recap

telephone numbers