Upload
abojabl
View
223
Download
2
Tags:
Embed Size (px)
DESCRIPTION
Qos in Telecomm
Citation preview
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)
2Property of Neotelis
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)
3Property of Neotelis
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
4Property of Neotelis
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)
5Property of Neotelis
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
6Property of Neotelis
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
7Property of Neotelis
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
8Property of Neotelis
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
9Property of Neotelis
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
10Property of Neotelis
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
11Property of Neotelis
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 &
12Property of Neotelis
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
13Property of Neotelis
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
14Property of Neotelis
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
15Property of Neotelis
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
16Property of Neotelis
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,
17Property of Neotelis
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
18Property of Neotelis
Videoconference systems Computers; facsimile
- etc.
10
Introduction to QoS Typical private networks
Local Area Network (LAN)
S i h
AZ
19Property of Neotelis
Switch
Introduction to QoS Typical private networks
Private Branch eXchange (PBX)
PBX PSTN
In-House Lines
Outside Lines (trunk to CO)
20Property of Neotelis
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
21Property of Neotelis
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
22Property of Neotelis
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
23Property of Neotelis
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
25Property of Neotelis
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
26Property of Neotelis
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
27Property of Neotelis
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
28Property of Neotelis
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 )
29Property of Neotelis
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
30Property of Neotelis
HLRMSC Server
SGSN IP Networkpacket technology
16
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
31Property of Neotelis
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
32Property of Neotelis
SME
Cafe
SOHO
Airport
WiMAX
17
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
33Property of Neotelis
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.
34Property of Neotelis
Mechanisms are required to manage network resources in order to ensure suitable Quality of Service for each application
18
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
35Property of Neotelis
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
36Property of Neotelis
Echo Interrupts Frequency response Loudness levels
19
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
37Property of Neotelis
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
38Property of Neotelis
Cumulative effect on subscriber satisfaction of all imperfections affecting the service
20
Introduction to QoS Various perceptions
39Property of Neotelis
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
40Property of Neotelis
function or performance and provide predictable quality of service
21
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)
41Property of Neotelis
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
42Property of Neotelis
Delay, jitter, packet loss, throughput, Device Factors include such items as
endpoints, gateways, routers, firewalls, network address translation, processor, memory,
22
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
43Property of Neotelis
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
44Property of Neotelis
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
45Property of Neotelis
Error rate Sequence errors Echo Blocking
QoS issues in existing networks Networking devices and queuing
General switching architecture
46Property of Neotelis
24
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
47Property of Neotelis
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.
48Property of Neotelis
Physical layer:bit-level encoding
Data link layer:e.g. Ethernet
encapsulation,fragmentation)
Queuing management
25
QoS issues in existing networks Networking devices (blocking)
49Property of Neotelis
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
50Property of Neotelis
A Packets in queue (delay)Output queue: packets may be dropped (loss) if queue is full
26
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
51Property of Neotelis
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
52Property of Neotelis
PropagationProcessing Queuing
ADelay
= t1 + t2
27
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
53Property of Neotelis
Propagation delay Significant on international and satellite links
e.g. up to 50 milliseconds (200 milliseconds or more for satellite)
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)
54Property of Neotelis
28
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
55Property of Neotelis
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
56Property of Neotelis
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)
57Property of Neotelis
Narrowband access Broadband access
xDSL
POTS/ISDNDial-up H.323/SIP
Enterprise customers LAN
3G
NGN concepts & IP technology IP architecture evolution
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
58Property of Neotelis
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
59Property of Neotelis
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
60Property of Neotelis
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
61Property of Neotelis
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
62Property of Neotelis
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
32
NGN concepts & IP technology IP architecture evolution
From tightly linked to distributed architecture!
SwitchingMatrix
Service Delivery & Connection
Control IP or ATMTrunking Gateways
Softswitch
Access Gateways
IP Terminals
63Property of Neotelis
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
64Property of Neotelis
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
65Property of Neotelis
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
66Property of Neotelis
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)
67Property of Neotelis
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
68Property of Neotelis
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
69Property of Neotelis
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
70Property of Neotelis
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
71Property of Neotelis
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
72Property of Neotelis
F R2 3
A
F
D
E
BC3
4 3
11
2
2
R2R1
37
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
73Property of Neotelis
database engines (Wikipedia definition)
NGN concepts & IP technology Putting the pieces together
H bSMTP server
DNS server
HubHubserver
SwitchDHCP Server
74Property of Neotelis
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
75Property of Neotelis
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)
76Property of Neotelis
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
NGN concepts & IP technology
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
77Property of Neotelis
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
78Property of Neotelis
Tier-1 ISP Tier-1 ISP
Tier-2 ISP Tier-2 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
79Property of Neotelis
Tier-1 ISP Tier-1 ISP
Tier-2 ISP Tier-2 ISP
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
80Property of Neotelis
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
81Property of Neotelis
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)
82Property of Neotelis
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 )
83Property of Neotelis
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
84Property of Neotelis
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
85Property of Neotelis
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
86Property of Neotelis
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
87Property of Neotelis
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
88Property of Neotelis
linkphysical application
transportnetwork
linkphysical
applicationtransportnetwork
linkphysical
45
TCP/IP Model
NGN concepts & IP technology
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
89Property of Neotelis
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
applicationtransportnetwork
networklink
physicaldata
transport
ack
90Property of Neotelis
linkphysical application
transportnetwork
linkphysical
applicationtransportnetwork
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
91Property of Neotelis
networklink
physical
networklink
physical
MM
H tHnH tHnH l
MM
H tHnH tHnH l
datagramframe
packetsegment
datagramframe
Sourceapplicationtransportnetwork
linkHtHnHl MHtHn MHt M
M
Switch
NGN concepts & IP technology
Packet (Message) Handling
physical
linkphysical
HH M
HtHnHl M HtHnHl M
92Property of Neotelis
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
93Property of Neotelis
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
94Property of Neotelis
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
95Property of Neotelis
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
96Property of Neotelis
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
97Property of Neotelis
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
98Property of Neotelis
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
50
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)
99Property of Neotelis
Location #1 Location #2Traditional networks
QoS issues raised by NGN & IP
PSTN
WAN
Leased line
PABX
100Property of Neotelis
Leased lineHost
Controller
51
Location #1 Location #2
Converged networks (NGNs)
QoS issues raised by NGN & IP
WAN
PABX
101Property of Neotelis
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
102Property of Neotelis
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
103Property of Neotelis
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
104Property of Neotelis
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
105Property of Neotelis
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
106Property of Neotelis
the factors that affect quality of service of real-time transport on data networks that were primarily not designed for real-time traffic
54
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)
107Property of Neotelis
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
108Property of Neotelis
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
109Property of Neotelis
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
110Property of Neotelis
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
111Property of Neotelis
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
112Property of Neotelis
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
113Property of Neotelis
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
114Property of Neotelis
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
115Property of Neotelis
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%
116Property of Neotelis
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
117Property of Neotelis
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
118Property of Neotelis
bit errors