UbiCom Book Slides

1
UbiCom Book Slides

• Chapter 11
• Ubiquitous Communication

Stefan Poslad http//www.eecs.qmul.ac.uk/people/st
efan/ubicom
2
Chapter 11 Overview

• Chapter 11 focuses on
• Internal system properties distributed
• External interaction with ICT environment

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5 Main Properties for UbiCom Systems
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UbiCom System Model Focussing on Interaction in
Virtual Computing Environments
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Related Chapter Links

• Distributed Computing (Chapter 3)
• Mobile Services (Chapter 4)
• Intelligent Interaction (Chapter 9)
• Mobile Distributed Systems (Chapter 4)
• Management of Distributed Systems (Chapter 12)

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Chapter11 Overview

• The slides for this chapter are also expanded and
  split into several parts
• Part A Introduction
• Part B Audio Networks
• Part C Data networks Fixed
• Part D Data networks Wireless
• Part E Video Multi-Content Access Networks
• Part F Ubiquitous Networks PLC, PAN, BAN,
  Mobile
• Part G Network Access Control
• Part H Service-Oriented Networks 1
• Part I Service-Oriented Networks 2

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(No Transcript)
8
Chapter11 Overview

• The slides for this chapter are also expanded and
  split into several parts
• Part A Introduction ?
• Part B Audio Networks
• Part C Data networks Fixed
• Part D Data networks Wireless
• Part E Video Multi-Content Access Networks
• Part F Ubiquitous Networks PLC, PAN, BAN,
  Mobile
• Part G Network Access Control
• Part H Service-Oriented Networks 1
• Part I Service-Oriented Networks 2

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Ex Communication Networks

• Time order the following networks
• Internet (data), radio (audio), television,
  telephone
• Which became established first for mass-use when
  why?

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Introduction

• Ubiquitous applications need to access relevant
  remote external information and tasks, anywhere
  and anytime.
• Different applications require different
  combinations of network functions and services,
  e.g., data streaming, minimal jitter, specific
  media access control etc.
• Different networks support different sets of
  communication functions in different ways.

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Introduction

• Key design issues
• Should comms functions be largely transparent to
  services (network-oriented) versus should comms
  be exposed via some interfaces configured /
  controlled by services (service-oriented).
• Should networked services be accessible from
  anywhere versus selectively accessing networked
  services, e.g., some services may be limited to a
  locality?

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Introduction

• Many general and introductory texts and
  descriptions about networking are specialised
  towards specific types of networks, e.g.,
• ???
• An interpretation of UbiCom
• Ubiquitous Communication
• Any content on any network, anytime, anywhere
• Hence, complete range of different media networks
  is treated holistically here

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Network Communication Functions

• Communication involves the following key
  functions
• Encoding and Modulation
• Signal Distribution
• Channel sharing and efficiency
• Medium Access Control (MAC)
• Logical Link Control (LLC
• Error checking and correction
• Data Transfer Control
• buffered vs. unbuffered.
• Asynchronous vs. synchronous
• Data Routing
• Message security
• Metadata
• Transcoding.

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Network Communication Functions

• Explain all these in detail in next slides

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Digital Communication

• Historically, audio / video content transmitted
  in analogue form although these transmissions
• Gradually being replaced by digital signal
  modulation of analog.
• Signals as digital standards become established
• N.B. Strictly speaking, all physical
  transmissions of signals are analogue, however,
  the modulation of signals may convey digital
  information.

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Benefits of Digital Communication

• Benefits for using digital transmissions?

17
Chapter11 Overview

• The slides for this chapter are also expanded and
  split into several parts
• Part A Introduction
• Part B Audio Networks ?
• Part C Data networks Fixed
• Part D Data networks Wireless
• Part E Video Multi-Content Access Networks
• Part F Ubiquitous Networks PLC, PAN, BAN,
  Mobile
• Part G Network Access Control
• Part H Service-Oriented Networks 1
• Part I Service-Oriented Networks 2

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Types of Audio Networks

• PSTN Voice Networks
• Intelligent Networks (IN)
• IP Multimedia Subsystems (IMS)
• ADLS Broadband
• Telecoms WWAN
• Telecoms WLAN DECT
• Audio Broadcast (Radio Entertainment) Networks

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Audio Networks

• 1st type of pervasive communications network
• Two basic types
• Audio unicast networks (PSTN)
• Audio broadcast (radio) networks

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Public Switched Telephone Network (PSTN)

• PSTN orig. designed to support voice
  communication (not data, video)
• Analogue -gt digital transmissions
• Still use separate networks for voice data
  although convergence of voice, data and
  audio-video progressing
• Phones (fixed mobile) act as PSTN access
  devices

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Public Switched Telephone Network (PSTN)

• Home users
• Single-line local loop to external local
  switching station
• Work users
• Phones connect to a private circuit switched
  network or Private Branch Exchange (PBX) to
  access external networks.
• etc.

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PSTN
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PSTN

• Core network orig. circuit switched not
  packet-switched networks
• Designed to 1st set up dedicated circuit of links
  between switching offices
• Circuit switching used in Telecoms networks used
  hierarchy 5 levels

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PSTN

• PSTNs were designed to be very resilient.
• Circuit switching can enable a higher QoS per
  call but at the expense of non-optimal use of the
  channel,
• Interleaved multiple data streams ? throughput
• E.g.,
• Later digital telecoms networks

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Intelligent Networks (IN)

• Earliest digital telecommunication networks
  designed to support specific services, supported
  using specialised logic contained in specialised
  switching network elements.
• New features / services have to be added and
  implemented directly in core switch systems -gt
  very long development times for new services
• -gt Intelligent Networks (IN) network service
  model,

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Intelligent Networks (IN)

• Supports independent component-based services in
  general purpose computer nodes rather in special
  switching nodes.
• Enables service providers to drive new services
  rather than network providers
• able to use these to form flexible overlay
  networks
• such as toll free calls, e.g., 0800 numbers.

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IP Multimedia Subsystems (IMS)

• Active development in new IN services has
  declined in recent years
• Focus on development of telecom services APIs
  rather than on developing new telecom network
  protocols.
• Although, there seems to be a clear move to IP
  based networks, in shorter term, hybrid IN and
  Internet service architectures for mobile users
  are being proposed such as IP Multimedia
  Subsystems (IMS).

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IMS

• A key challenge is application-layer control
  (signalling) protocol for controlling voice/video
  session, multimedia conference, messaging and
  Presence over IP.
• Control can be performed using the IETF SIP
  (Session Initiation Protocol) replacing ITUs
  earlier H.323 protocol.
• Basic entities in a typical SIP system involve?

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IMS

• SIP can use 3 different types of MCU
• full mesh,
• mixer
• multicast.

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Asynchronous Digital Subscriber Line (ADSL)
Broadband

• ADSL ? transmission capability over existing
  physical
• e.g., copper-wire PSTN type, access networks.
• Audio telephony use 3 kHz bandwidth but
  typical line transmits usable signals up to
  approximately 1MHz.
• High-frequency signals however face more
  transmission challenges such as ..

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Telecoms ADSL
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Telecoms WWAN

• Wireless Wide-Area Networks (WWAN)support
  anywhere access for mobile or cell phone users,
• WWAN differ w.r.t
• Geographic region
• on the Generation (G) of the wireless network
  such as 1G analogue and 2G digital.
• These differ primarily on the way they are
  designed to share access to the wireless network
  amongst different users.

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Telecoms WWAN

• WWAN differ primarily on the way they are
  designed to share access to wireless network
  amongst different users.
• Global System for Mobile Communications (GSM)
• Code Division Multiple Access (CDMA)
• Networks can interoperate via gateways

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Telecoms WWAN

• WWAN transmitters or base stations have a limited
  range
• When a user moves between cells, What happens?

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WLAN DECT (Digital Enhanced Cordless
Telecommunications)

• Deployed gt 100 countries worldwide
• Access control
• Frequencies

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Audio Broadcast (Radio Entertainment) Networks

• Several benefits in using audio broadcasting or
  radio?

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DAB

• For digital radio, the Eureka 147 Digital Audio
  Broadcast (DAB) standard is most commonly used
  and is coordinated by the World DMB Forum.
• DAB uses the MPEG-1 Audio Layer 2 audio (MP2)
  codec for audio broadcasting while personal
  players use the MP3 codec.
• Original objectives of DAB were to ?
• DAB standard with a better and more efficient
  transmission codec has been proposed.

38
Chapter11 Overview

• The slides for this chapter are also expanded and
  split into several parts
• Part A Introduction
• Part B Audio Networks
• Part C Data networks Fixed ?
• Part D Data networks Wireless
• Part E Video Multi-Content Access Networks
• Part F Ubiquitous Networks PLC, PAN, BAN,
  Mobile
• Part G Network Access Control
• Part H Service-Oriented Networks 1
• Part I Service-Oriented Networks 2

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Internet

• Early Internet (1960s) was based upon several
  innovations.
• Shift from batch to time-shared computers.
• Shift from P2P topology
• Shift from analogue to digital communication
• Support for high capacity and resilient network
  paths
• Large data was split into fixed size data packets
  
• Shift from circuit switched to packet-switched
  data model

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Network Protocols

• Types of data and control packets are defined in
  a network communication protocol
• Data packet size
• Data segmentation.
• .

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Network Protocols

• Types of packet to data packets called control
  packets,
• Each data packet is labelled with the address
• Enables packets from multiple messages to be
  multiplexed to use the same part of the network.

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Data Packet Protocols
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Addressing

• Before communication can occur between network
  elements, e.g., computers, they need to be
  allocated network addresses.
• Explain .

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Address Space Size

• IPv4 supports 32 bit (about 4.3 billion)
  addresses.
• IPv6 supports 128 bit addresses

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Routing and Internetworking

• Multiple paths may be available
• Data may be too large to be transmitted
• Normally performed at the network level without
  applications being aware of this.

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Packet-switched Routing
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Routing and Internetworking

• Routers examine the addresses of data packets to
  decide
• ????
• Routers communicate with each other using
  specialised routing protocols
• ??
• Dynamic routing ?
• Use of multiple routes ?

48
Chapter11 Overview

• The slides for this chapter are also expanded and
  split into several parts
• Part A Introduction
• Part B Audio Networks
• Part C Data networks Fixed
• Part D Data networks Wireless ?
• Part E Video Multi-Content Access Networks
• Part F Ubiquitous Networks PLC, PAN, BAN,
  Mobile
• Part G Network Access Control
• Part H Service-Oriented Networks 1
• Part I Service-Oriented Networks 2

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Wireless Data Networks

• Wireless LANs (WLANs) / WiFi
• WiMAX
• BlueTooth
• ZigBee
• InfraRed (IR)
• Ultra Wide Band (UWB)
• Satellite and Microwave

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Wireless Data Networks

• Benefits for using wireless networks
• Anywhere
• Mobility
• Less disruptive
• Adaptivity

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Wireless Data Networks

• Wide variety of wireless networks exist.
• Networks vary according to ?

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Wireless Data Networks examples

• Most global, wide area and local area wireless
  networks are infrastructure dependent and use
  fixed transmitters,
• Ad Hoc Wireless Network the transmitters and
  routers are dynamic
• .
• Mobile wireless networks can vary by the range
  they cover.

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Wireless Data Networks

• Range depends upon ?
• Generally, the higher the frequency

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Wireless Data Networks

• Spatial Efficiency (SE )
• Power efficiency metric
• Spatial and power efficiency

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Wireless Data Networks bandwidth allocation

• Proliferation of new wireless services
• -gt concern over how to (re)allocate scarce radio
  frequency (
• New to techniques allow ? flexible efficient
  spectrum use?

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Wireless Data Networks Software Radio

• Software Radio moves the radio functionality from
  hardware into software
• Software radio alters trad. radio design in 3
  main ways. How?

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Wireless LANs (WLANs)

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WiMAX

• WiMAX, the Worldwide Interoperability for
  Microwave Access, from the WiMAX Forum , is
  proposed as wireless wide-area broadband access
  technology, based upon the IEEE 802.16 standard
• Etc.

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Bluetooth

• Bluetooth standard for short-range wireless
  communication over about 1-100M
• Bluetooth applications include both local
  communication and increasingly local control.
• Unlike IR, Bluetooth does not require a line of
  sight between the transmitter and receiver.
• Current Bluetooth devices and applications
  include ?

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Bluetooth versus WLAN

• ???

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ZigBee

• ZigBee is a specification for a suite of
  communication protocols from the ZigBee alliance
  formed in 2002
• Uses small, low-power digital radios based on the
  IEEE 802.15.4 standard for Wireless Personal Area
  Networks (WPAN)
• etc

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ZigBee versus Bluetooth

• ???.

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Infrared (IR)

• Infrared (IR) a short-range low bandwidth data
  communication
• ..

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Ultra-Wideband (UWB)

• Transmits information at data rates exceeding 100
  M bits / s, spread over a large bandwidth (gt500
  MHz), in the 3.110.6 GHz frequency range at a
  low power range, over short distances.
• Provide an efficient use of scarce radio
  bandwidth while enabling both high data rate
  wireless connectivity
• Uses
• Short-range BANs, PANs and within buildings
• Longer-range, low data rate applications radar,
  collision obstacle avoidance, precision altimetry
  imaging systems

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Satellite and Microwave Comms

• Geostationary satellites use simpler antennae
  design and configuration small No. of
  satellites can be interlinked to provide global
  coverage.
• Satellite design issues?

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Internetworking WLANs

• Benefits to internet wireless networks ?
• WLAN can access Internet for mobile computer,

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Internetworking WLANs

• Mobile phone use faster? Cheaper? WLAN at hot
  spots
• requires OS support pipelines across
  heterogeneous networks.
• Generic Access Network (GAN), also known as
  Unlicensed Mobile Access (UMA), is a
  telecommunication system allowing seamless
  roaming and handover between local area networks
  and wide area networks using dual-mode mobile
  phones.
• Femtocells, small cellular access points which
  provide enhanced coverage converged voice, data
  and video services such as IPTV

68
Chapter11 Overview

• The slides for this chapter are also expanded and
  split into several parts
• Part A Introduction
• Part B Audio Networks
• Part C Data networks Fixed
• Part D Data networks Wireless
• Part E Video Multi-Content Access Networks ?
• Part F Ubiquitous Networks PLC, PAN, BAN,
  Mobile
• Part G Network Access Control
• Part H Service-Oriented Networks 1
• Part I Service-Oriented Networks 2

69
Universal Content Networks / Network Convergence

• Services ? delivered over common network
• Audio and Video (AV) broadcast Content Based
  Networks (CBN) have different drivers compared to
  Telecoms and network networks.
• Telecoms networks are developed to support duplex
  or two-way, one-to-one communication, global
  interoperability
• Internet developed (initially) to support
  asynchronous communication.

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Audio and Video (AV) broadcast Content Based
Networks (CBN)

• Digital AV CBN designed to transmits streamed
  audio video
• .
• Broadcast networks are designed more for

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Audio and Video (AV) broadcast Content Based
Networks (CBN)

• AV CBN oriented to for a regional rather than
  global customer base.
• Video content is richer and it is more likely to
  be tailored to a specific region in terms of
  language and culture.
• Receivers have limited control over live
  broadcasts
• Video synchronisation with audio ( metadata) is
  complex

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Internet and Common Codecs

• Internet focussed most on alphanumeric data
  transmission
• support for managing reliable and unreliable data
  streams, mainly for paired senders and receiver.
• support for scalable AV content streamed
  broadcasts over Internet still maturing
• Adoption of compatible standards for the
  triple-play (audio, video and alphanumeric data)
  will facilitate their integration.

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PSDN IP and UDP

• UDP ( User Datagram Protocol) used to support
  mutlicast
• .
• Unreliable transport protocols, e.g., UDP can be
  used to transmit media streams.
• Depending on the protocol and the extent of the
  loss, receivers may be able to recover the data
  using

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Streaming Media over IP networks

• Protocols designed to stream media over IP
  networks.
• RTP and RTCP built on top of unreliable UDP
• RTSP built on top of reliable TCP

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Combined Voice and Data networks ADSL

• In residential SME buildings, single external
  comms line is used to access multiple services,
  e.g., voice, text, video,
• ADSL is replacing use of older ISDN, dial-up
  modems
• There are different types of access device or
  modem, e.g.,

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(No Transcript)
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Voice over IP (VoIP)

• Use of IP network, to In transmitting voice as
  data packets interleave text data and voice
  over same network
• Requirements \/
• Delays can be caused by ?

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Combined Audio-Video and Data Content
Distribution Networks

• Traditionally, the three different types of
  conventional networks for broadcasting
  audio-video entertainment content are
• VHF TV
• Satellite TV
• Cable TV.

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Integrating Analogue Video and Text Teletext

• Analogue television broadcast signal can be
  augmented with text data by embedding this data
  in the Vertical Blanking Interval or VBI part of
  the television signal.
• In EU called Teletext data transmission
  closed-captioning in USA
• .

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Digital Video Broadcasting (DVB)

• DVB replacing analogue video broadcasting
• Multiple standards for digital video broadcasting
• .
• DVB system is the most widely used
• DVB is modelled like TCP/IP at an abstract level
• All data is transmitted as MPEG-2 transport
  streams.

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Multimedia Broadcast networks

• Triple-play networks, e.g., Web documents VoIP,
  video streaming.
• Quad-play networks triple-play mobile phone
• Need to multiplex heterogeneous packets from
  multiple applications which have different
  sensitivities to time delays and jitter. Several
  ways to this in IPv4 networks?
• IPv6 has more inbuilt support for this.

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Multiplexing heterogeneous packets from multiple
applications (IPv4)

• MPLS
• Differentiated Services (Diffserv)
• Resource Reservation Protocol (RSVP)

83
On-demand, Interactive and Distributed Content

• In contrast, Video-On-demand (VoD) Benefits?

84
Chapter11 Overview

• The slides for this chapter are also expanded and
  split into several parts
• Part A Introduction
• Part B Audio Networks
• Part C Data networks Fixed
• Part D Data networks Wireless
• Part E Video Multi-Content Access Networks
• Part F Ubiquitous Networks PLC, PAN, BAN
  Mobile?
• Part G Network Access Control
• Part H Service-Oriented Networks 1
• Part I Service-Oriented Networks 2

85
Pervasive Networks Types

• Already covered some examples of pervasive
  networks
• Mobile Telecoms Networks such as GSM, UTMS
• Wireless data networks WiFi, Bluetooth, Zigbee
  etc
• In addition will cover
• Power Line Communication (PLC)
• Personal Area Networks (PAN)
• Body Area Networks (BAN)
• Mobile Users Networks

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Pervasive Telecoms Networks
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Pervasive Wireless Networks Challenges

• Signal Transmission
• Overlapping Networks
• Power Consumption Transmission Efficiency
• Soft Boundaries Access Control
• Interference

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Power Line Communication (PLC)

• An alternative to ubiquitously access data and
  A-V content.
• Wherever there is an electricity PL connection,
  same network that conducts electricity to deliver
  energy
• PL can be used modulate electricity as a signal
  and can be used as a channel to communicate
  data/AV content.
• PLC describes a range of systems for using
  electricity distribution wires for simultaneous
  distribution of data.

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Wireless Personal Area Networks (WPAN)

• Specified by the IEEE P802.15 working group
• PAN is normally confined to a person or object
  typically lt10 M in all directions and envelops
  two or more objects or persons whether stationary
  or in motion.
• Could WLAN standard be used for PANs?
• Bluetooth, Zigbee and IR can be used to implement
  a PAN.

90
Wireless Personal Area Networks (WPAN)

• Typical WPAN applications include ??

91
Body Area Network or BAN

• Consists of a set of mobile and compact
  intercommunicating sensors that are either
  wearable or implanted into the human body.
• A typical BAN application can monitor vital body
  parameters and movements
• E.g., monitor EEG, ECG, and EMG signals
• Data Management?
• Either to store them in some device on the body
  for later upload and analysis
• To periodically transmit data in real-time via
  some external network interface

92
BAN

• Can Bluetooth or ZigBee be used for BAN?

93
BAN

• Electronic devices can be connected as part of
  near field BANs to exchange digital information
  by capacitively coupling picoamp currents through
  the body (Zimmerman).
• Low-frequency carrier, less than one megahertz,
  was used. Why?
• Zimmerman demonstrated a near-field BAN system
  to support business processes

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Inter-BAN Application
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Mobile Users Networks

• Not all network access by mobile users,
  applications and devices need be via wireless
  networks and vice versa
• Wireless access devices can be static and mobile
  users can move in between wired or wireless
  hotspots such as in Internet cafes.
• Mobility vs. portability network support.

96
Mobile User Networks Design Issues

• Design issues include?
• We can also classify mobile network support in
  terms of ?
• Advantage of mobile user support at the network
  level of the network protocol stack means that
  mobility, at least to some extent, is transparent
  to applications.

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Concepts Mobile vs. Wireless Services
98
Mobile Addresses

• Network location or address for a mobile user
  needs to be determined in order for a user to
  receive data.
• It is easier to send (somewhere) as the user just
  has to locate the nearest access network base
  station.
• There are two basic approaches to mobile user
  addressing
• ????.

99
Message Routing for Mobile Users

• Different types of routing for mobile users
  can be classified along 2 dimensions
• Fixed versus variable routes
• Single versus multi-path routes

100
Message Routing for Mobile Users single path
route

• Example of single path route is Mobile IP
  consisting of Mobile Node, Home agent and foreign
  agent
• Mobile IP performs three main functions
• Discovery.
• Registration
• Tunnelling

101
Message Routing for Mobile Users single path
route

• Mobile IP performs three main functions
• Discovery
• Registration
• Tunnelling

102
Multi-Path Routing in Mobile Ad hoc Networks
(MANETs)

• In contrast to fixed computer networks, ad hoc
  networks
• use connections established for duration of 1
  session
• require no base station or fixed router.
• Ad hoc networks that support mobile nodes are
  called Mobile Ad hoc Networks (MANETs)
• Rather than used dedicated router nodes, each
  node is willing to forward data for other nodes,
  and so the determination of which nodes forward
  data is made dynamically based on the network
  connectivity, hence the name ad hoc

103
MANETs

• Instead, devices discover others within range to
  form a network for those computers.
• Devices may search for target nodes that are out
  of range by flooding the network with broadcasts
  that are forwarded by each node.
• Connections can be made over multiple nodes
  (multi-hop ad hoc network).
• Routing protocols then provide stable connections
  even if nodes are moving around.

104
MANETs

• MANETs Applications
• in situations where a useful network
  infrastructure is not already in place
• E.g., in natural disaster
• in armed conflict situations
• Wireless multiplayer gaming
• E.g., Sony's PlayStation and the Nintendo Dsi
  and Wii game consoles

105
MANET
106
Chapter11 Overview

• The slides for this chapter are also expanded and
  split into several parts
• Part A Introduction
• Part B Audio Networks
• Part C Data networks Fixed
• Part D Data networks Wireless
• Part E Video Multi-Content Access Networks
• Part F Ubiquitous Networks PLC, PAN, BAN
  Mobile
• Part G Network Access Control ?
• Part H Service-Oriented Networks 1
• Part I Service-Oriented Networks 2

107
Network Design Issues

• Network Access Control
• Controlling Network Access Firewalls, NATs and
  VPNs
• Group Communication Transmissions for Multiple
  Receivers
• Internetworking Heterogeneous Networks
• Separating Management and Control from Usage
• Ubiquitous versus Localised Access
• Global Use Low-cost Access Networks for Rural
  Use

108
Network Access Control Mobile Phone

• Different networks use a range of access control
  techniques to
• handle network resource allocation problems
• allow multiple users to access network media with
  limited capacity.
• TDMA
• CDMA

109
Network Access Control WLAN

• WLANs often based on sharing freq. between
  several active users.
• Many simultaneous users may cause packet
  collisions -gt waste channel bandwidth
• Difficulty to detect some (hidden) nodes -gt
  design to avoid packet collisions.
• WLANs typically use a MACA type transmission
  protocol.

110
Network Access Control LAN

• A further option is to use CSMA/CD

111
Network Access Control LAN

• Token-based systems control access to local
  networks using special control messages, tokens,
  which continuously circulate throughout a system,
  
• e.g., structured as a token ring topology.

112
Controlling Network Access Firewalls, NATs and
VPNs

• Many ICT resources connected to the Internet are
  protected to control access to specific
  resources by specific users or to a closed user
  group.
• If access is not restricted what happens?

113
Controlling Network Access Firewalls, NATs and
VPNs

• How to protect access to local networks?

114
Controlling Network Access Firewalls

• Routes versus Firewalls
• A router / special purpose computer that .
• Firewalls designed according to which level of
  network they work

115
Controlling Network Access Firewalls

• Packet-level firewalls
• Application level firewalls

116
Controlling Network Access NAT

• Network Address Translation (NAT)
• Firewalls

117
Controlling Network Access NAT

• .

118
Controlling Network Access VPN

• Useful to restrict the use of resources on remote
  networks to specific users that are accessed over
  a public Internet.
• Common technique to achieve this is a VPN
• .

119
Controlling Network Access VPN

• Users normally authenticate themselves at VPN
  client or access device to gain access to remote
  resources via VPN
• Several types of VPN / Service
• ????

120
Controlling Network Access VPN

• Persistence of messaging
• Proxy host
• Bastion host
• Network Interfaces Available
• ???

121
Multicasts Transmissions for Multiple Receivers

• Sending the same message from a single source to
  a defined group of multiple receivers, multicast
  communication or group communication is useful.
  Why?
• Hardware vs. software support

122
Multicasts Transmissions for Multiple Receivers

• To avoid the overhead in managing large groups,
  groups can be split into hierarchies
• Messages can be tagged with sequenced identifiers
  to indicate ordering.
• Acknowledgements can be used to support more
  reliable group communications.

123
Multicasts Transmissions for Multiple Receivers

• Group membership may or may not be visible to the
  members depending upon the design.
• ???

124
Low-cost Access Networks for Rural Use VSAT

• Very Small Aperture Terminal (VSAT)
• .

125
Ubiquitous versus Localised Access

• Networks can be designed for local context-aware
  access
• Used to tailor services for local needs.

126
Ubiquitous versus Localised Access

• Services can be restricted to local access
  because?
• Local services can also be designed to have
  access control

127
Ubiquitous Access WANs
128
Global Use Low-cost Access Networks for Rural Use

• In theory, wireless networks could be ubiquitous
  but in practice they arent in many regions.
• Currently, the total worldwide Internet usage
  penetration was only about 18 but only about 4
  in Africa (2007).
• but 29 of the global population use GSM type
  mobile phone technology (2007), more if other
  types of mobile phone are also included.
• People in some rural areas may not be able to pay
  much
• Hence low-cost networks and access terminals are
  needed.

129
Low-cost Access Networks for Rural Use

• In rural areas, several low cost network access
  methods have been developed?
• CorDECT
• PrintCast
• VSAT
• Mesh Network

130
Low-cost Access Networks for Rural Use VSAT

• Very Small Aperture Terminal (VSAT)
• ??.

131
Low-cost Access Networks for Rural Use CorDECT

• CorDECT system
• Based on the DECT standard which initially was
  designed for use with cordless telephones.
• Uses MC-TDMA to performs both time and frequency
  division in order to accommodate multiple
  channels.
• Typically operates over distances of up to 10 KM
  with data rates supporting data rates of 35 and
  70kbps. T
• Conventional listen before you talk type MAC is
  problematic when used in low bandwidth
  transmission over several km

132
Low-cost Access Networks for Rural Use PrintCast

• PrintCast system leverage broadcast TV as a
  service access network.
• .

133
Chapter11 Overview

• The slides for this chapter are also expanded and
  split into several parts
• Part A Introduction
• Part B Audio Networks
• Part C Data networks Fixed
• Part D Data networks Wireless
• Part E Video Multi-Content Access Networks
• Part F Ubiquitous Networks PLC, PAN, BAN
  Mobile
• Part G Network Access Control
• Part H Service-Oriented Networks 1 ?
• Part I Service-Oriented Networks 2

134
Service-oriented Networks

• Internetworking
• Network-Dependent vs. Independent Services
• Separating Management and Control from Usage
• Service Orientation in Edge Network

135
Internetworking Heterogeneous Networks

• Ideally, universal access means
• any type of data
• may be accessed simultaneously
• anywhere over any kind of network
• Historically, many separate types of
  communication network exist that are not
  interlinked.
• Networks are heterogeneous in terms of the
  physical media that electromagnetic signals
  propagate through.
• e.g., signals may propagate through wired copper
  or optical fibre networks or through wireless or
  Over-The-Air, (OTA) networks.

136
Internetworking Heterogeneous Networks

• Different types of physical or links of the
  network have different signal capacities and have
  different signal attenuation and hence different
  requirements for signal amplification and
  repeaters.
• Each type of physical media network,
• e.g., Ethernet, Point to Point Protocol (PPP)
  defines its own protocols to partition, structure
  data into packets for transmission.

137
Inter-Network Architecture
138
Separating Management and Control from Usage

• Are different options for designing application
  use versus control and management of networks
• Architectural model can separate concerns about
• media access,
• control of the communication
• management of the communication.

139
Separating Management and Control from Usage

• Management
• FCAPS functions.
• Control
• .
• Application centric model

140
Separating Management and Control from Usage
141
Separating Management and Control from Usage

• in-band signalling
• out-of-band signalling

142
Separating Management and Control from Usage

• In some systems, each major application uses its
  own dedicated network,
• Hence management is application (network)
  specific.
• As multimedia content applications are becoming
  integrated into single networks, ..

143
Network Dependent Services

•  Traditionally, different application services
  were coupled to specific networks because
  different applications need different levels of
  support for
• Data transmission functions, such as latency,
• sequencing,
• performance and reliability,
• channel sharing,
• data control
• security.

144
Network Independent Services

•  Simpler to design networks to support 1 specific
  set of application requirements rather than to
  support multiple applications. Why?
• Disadvantages?

145
Service-Oriented Networks

• Focus was on network oriented models
• To use a service, users must subscribe to a
  particular network and service configuration on
  the network,
• e.g., voice calls via a telecoms network and
  audio-video content via an audio-video wireless
  broadcast network.
• Focus has now shifted to service- oriented models
• Focus is on core networks that support multiple
  services
• Services are coupled less to specific networks
• Services can be available across heterogeneous
  networks

146
Paradigm Shift from Network-Oriented to Service
Orientated Architectures
147
A Simple Network Topology

• Simplest network topology is to have only one
  network
• E.g., analogue VHF radio network from transmitter
  to receiver
• Next simplest network topology is to partition
  network into 2 parts
• Access network or edge network
• Core network

148
Service-Orientation in Edge Network

• Important design decision is whether or not to
  put the complexity or intelligence for service
  specific communication
• into the core network,
• e.g., PSTN
• Or in the edge network
• Or in both
• e.g., IP networks.

149
Service-Orientation in Edge Network

• Motivation for end-to-end or edge-based
  complexity?
• A main argument is that functions placed at low
  levels of system may be redundant or of little
  value when compared with cost of providing them
  at that low level.
• This implies that networks that are simple and
  neutral as possible should be used

150
Service-Orientation in Edge Network

• Widespread adoption of IP in the core network has
  given the Internet a nearly universal
  interoperability
• allows all end users to access Internet
  applications and content on a non discriminatory
  basis.
• IP provide a network neutrality vision for comms
  content delivery worlds in which every end user
  can obtain access to every available application
  and piece of information is quite compelling.
• However, it has led to some content providers
  resisting more open access to the edge network as
  they will lose market share.

151
Chapter11 Overview

• The slides for this chapter are also expanded and
  split into several parts
• Part A Introduction
• Part B Audio Networks
• Part C Data networks Fixed
• Part D Data networks Wireless
• Part E Video Multi-Content Access Networks
• Part F Ubiquitous Networks PLC, PAN, BAN
  Mobile
• Part G Network Access Control
• Part H Service-Oriented Networks 1
• Part I Service-Oriented Networks 2 ?

152
Service-Oriented Networks 2

• This part gives an overview of network paradigms
  that support some more flexible messaging
• Content-based Networks (CN)
• Programmable Networks
• Overlay Networks
• Mesh Networks
• Cooperative Networks

153
Content-based Networks (CN)

• CN is a network in which the flow of messages
  through the network is driven by the content of
  the messages, rather than by linking specific
  senders to specific receivers.
• With this communication pattern, receivers
  subscribe to the types of content that are of
  interest to them without regard to any specific
  source (unless that is one of the selection
  criteria).
• Senders simply publish information without
  addressing it to any specific destination.

154
Programmable Networks

• Typically, service providers do not have access
  to the router, in order to optimise network use
  for different applications.
• e.g., router control environments algorithms
  router states,
• This makes the deployment of new network
  services, which could be far more flexible than
  proprietary control systems, impossible due to
  the closed nature of network nodes.

155
Programmable Networks

• Programmable networks allow some of the network
  elements to be reprogrammed dynamically
• .
• Disadvantages?
• .

156
Programmable Networks

• 2 two main initiatives to establish programmable
  networks
• DARAPAs Active Networks (AN) program
• Open Signalling (Opensig) community.
• Difference in focus between these two?

157
Overlay Network

• An overlay network is a virtual network built on
  top of a physical network that provides a
  (virtual) infrastructure to one or more
  applications.
• It handles the forwarding and handling of
  application data in ways that can differ from or
  in competition with the basic underlying physical
  network such as the Internet or PSTN.
• It can be operated in an organised and coherent
  way by third parties, which may include
  collections of end-users.

158
Overlay Network

• Motivation for Overlay networks
• ????

159
Overlay Network

• Another issue is that different applications may
  need different levels of reliability, performance
  and latency and security and access control.
• Application specific overlay networks can be
  incrementally deployed on end-hosts running an
  overlay protocol,

160
Mesh Networks

• In a full mesh network topology, every network
  node is connected using point-to-point
  connections to every other one. Cons?
• connecting every node to every other node is
  costly to wire and costly power wise to transmit
  to each other.
• Hence, in practice, mesh networks are usually
  partial mesh networks, in which each node is not
  connected to every other node.
• Partial mesh networks tend to combine ring and
  star based network topologies.

161
Full Mesh
162
Partial Mesh
163
Wireless Mesh Networks (WMNs)

• Are partial mesh, ad hoc, networks that can
  significantly improve the performance, at a lower
  cost and at a lower power output compared to
  other types of WLAN
• WMN is lower power because it uses a set of
  lower power multi-hop transmissions rather than
  needing a single more powerful transmission to
  base-station.
• WNM may be a suitable solution in rural areas
  where conventional base-station wireless type
  network support or DSL support maybe patchy.
• However, each WMN receiver is now more complex
  and more costly as it must also act as a relay.

164
Wireless Mesh Networks (WMNs)

• Instead of using a sophisticated and costly,
  centralised base stations, each wireless receiver
  in a WMN can act as a relay point or node for
  other receivers within range
• -gt WMN acts as a kind of cooperative network for
  its users.
• WMNs can be used to ??
• .

165
Wireless Mesh Networks (WMNs)

• In WMNs, each node operates not only as a host
  but also as a router (meshclients), forwarding
  packets on behalf of other nodes that may not be
  within direct wireless transmission range of
  their destinations
• In addition, dedicated mesh routers which contain
  additional routing capabilities and bridging and
  gateway function to other networks.
• WMN can also dynamically self-organise and
  self-configure mesh connectivity to support ad
  hoc multi-hop networking.

166
Wireless Mesh Network (WMN)
167
Cooperative Networks

• Some network access devices cannot access
  multiple networks in order to communicate, they
  just have access to 1 network connection
• Some other network access devices have inbuilt
  support to heterogeneous network access,
• e.g
• Each of these networks must be used in isolation
  they do not interoperate.

168
Cooperative Networks

• Multiple types of the same type of physical and
  network layer may exist
• because multiple independent users and providers
  may offer overlapping wireless networks within
  the same vicinity but yet again these do not
  interoperate.
• These overlap and the coincidence of multiple
  overlapping networks will increase as more
  networks get installed but yet again these
  networks do no interoperate.

169
Cooperative Networks

• Cooperative communication is designed to enable
  single-antenna mobile access devices to reap some
  of the benefits of being Multiple Input Multiple
  Outputs (MIMO) systems
• A specific problem that cooperative communication
  can solve at the physical media layer concerns
  signal fading
• because thermal noise, shadowing due to fixed
  obstacles and due to signal attenuation can vary
  significantly over the course of a given
  transmission.
• Transmitting independent copies of the signal
  that will face independent fading generates
  diversity and can effectively combat the
  deleterious effects of fading through combining
  these multiple signals.

170
Chapter11 Overview

• The slides for this chapter are also expanded and
  split into several parts
• Part A Introduction ?
• Part B Audio Networks ?
• Part C Data networks Fixed ?
• Part D Data networks Wireless ?
• Part E Video Multi-Content Access Networks ?
• Part F Ubiquitous Networks PLC, PAN, BAN
  Mobile ?
• Part G Network Access Control ?
• Part H Service-Oriented Networks 1 ?
• Part I Service-Oriented Networks 2 ?

171
Summary Revision

• For each chapter
• See book web-site for chapter summaries,
  references, resources etc.
• Identify new terms concepts
• Apply new terms and concepts define, use in old
  and new situations problems
• Debate problems, challenges and solutions
• See Chapter exercises on web-site

172
Exercises Define New Concepts

• Client-server, etc

173
Exercise Applying New Concepts

• What is the difference between client-server and
  P2P model?