VDSL Very High Bitrate DSL

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VDSLVery High Bit-rate DSL

• CTIS 451 Data Communications and Networking -
  Presentation
• Çagil Alsaç
• Can Özgüven

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Introduction The Internet

• A worldwide, publicly accessible series of
  interconnected computer networks that transmit
  data by packet switching using the standard
  Internet Protocol (IP).
• Consists of networks such as
• - domestic,
• - academic,
• - business,
• - government networks.

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Introduction The Internet (continued)

• These networks together carry various information
  and services such as
• - electronic mail,
• - online chat,
• - file transfer,
• - the interlinked web pages,
• - other resources of the World Wide Web (WWW).

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Introduction WAN Technologies

• A computer network that covers a broad area.
• Any network whose communications links cross
  metropolitan, regional or national boundaries.
• A network that uses routers and public
  communications links.

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Introduction WAN Technologies (continued)

• Examples
• - Campus area network (CAN),
• - Metropolitan area network (MAN),
• - The Internet -gt The largest and most
  well-known example of a WAN.

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Introduction WAN Technologies (continued)

• How to connect to the Internet
• - There are 3 connection types mainly used
  nowadays
• 1) Dial-up connections
• - The most common type of Internet connection
  available from ISPs (Internet Service Providers)
  in the past,
• - Still used and the slowest - the most
  inexpensive (56 Kbps), - In a dial-up
  connection, the users PC dials a phone number
  provided by the ISP and connects to the server
  then to the Internet.

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Introduction WAN Technologies (continued)

• 2) Cable connections - One of the best types of
  Internet connection available to the home users,
• - Offer very fast and reliable connections with
  a fixed monthly fee (approximately 30 Mbps ), -
  Because a cable connection uses a totally
  separate medium (Cable TV network through coaxial
  wires) to transfer data, it doesn't affect your
  ability to make/receive phone calls.

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Introduction WAN Technologies (continued)

• 3) ADSL connections - ADSL Asymmetric Digital
  Subscribers Line,
• - Becoming more and more widely available,
• - Provide an excellent Internet connection,
• - Fast and reliable (8 Mbps), - Work by
  splitting the phone line into two separate
  channels One for data (Internet) and one for
  voice (phone calls),
• - This means that users can talk on the phone
  and be connected to the Internet at the same
  time.

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Introduction WAN Technologies (continued)

• Both cable and ADSL connections are broadband
  connections that provide high bandwidth with a
  fixed monthly fee.

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Introduction Brief Definition of VDSL

• VDSL Very high bit-rate DSL.
• The next step in providing a complete home
  communications / entertainment package.
• Some companies offer VDSL service in selected
  areas.
• Provides an incredible amount of bandwidth, with
  speeds up to about 52 megabits per second (Mbps).

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VDSL The Necessities for a Better WAN
Technology

• Just like in other computer technologies, speed
  is crucial in Internet technologies.
• The speeds of the current Internet connection
  technologies are not satisfying the users
  anymore.
• More people buy home computers and create home
  networks.
• Other than the Internet Service, support for the
  integration of home services such as digital
  television and video-on-demand is demanded.
• The telephone lines can support more bandwidth
  than current DSL technologies use.

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VDSL The Necessities for a Better WAN
Technology (continued)

• Comparison of the various DSL technologies

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VDSL The Hardware

• VDSL operates over the copper wires in the phone
  line in much the same way that ADSL does.
• Therefore, VDSL uses two pieces of equipment just
  like ADSL.
• DSL Access Multiplexer (DSLAM) The DSL service
  provider has a DSLAM to receive customer
  connections,
• Transceiver (generally known as a DSL modem) At
  the customer's location there is a DSL
  transceiver, which may also provide other
  services.

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VDSL The Hardware (continued)

• The DSLAM
• The equipment at the access provider that really
  makes DSL happen,
• A DSLAM takes connections from many customers and
  aggregates them onto a single, high-capacity
  connection to the Internet,
• DSLAMs are generally flexible and able to support
  multiple types of DSL in a single central office,
• DSLAMs are generally able to support different
  varieties of protocol and modulation, such as
  DMT, in the same type of DSL,
• DSLAM may provide additional functions including
  routing or dynamic IP address assignment for the
  customers.

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VDSL The Hardware (continued)

• The Tranciever
• Generally called a "DSL modem by the customers,
• Engineers at the telephone company or ISP call it
  an ATU-R (ADSL Transceiver Unit - Remote),
• It's the point where data from the user's
  computer or network is connected to the DSL line,
  
• Can connect to a customer's equipment in several
  ways such as USB or 10 base-T Ethernet
  connections,
• Most of the ADSL transceivers sold by ISPs and
  telephone companies are simply transceivers,
• However, the devices used by businesses may
  combine network routers, network switches or
  other networking equipment in the same platform.

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VDSL The Hardware (continued)

• An ADSL Network Layout
• Notice that the maximum distance between the
  Central Office and the Clients Home is 4,000
  feet (1,200 meters) in VDSL!

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VDSL The Software

• Some VDSL trancievers come with software which
  helps the users easily setup the tranciever to
  establish a connection to the Internet.
• The setup can also be done via Internet Browsers
  that access the software implemented in the
  tranciever.

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VDSL The Software (continued)

• By using these software, the followings are
  basically identified to the network
• - DSL subscribers username and password,
• - PPP (Point-to-Point Protocol) form,
• - VCI - Virtual Channel Identifier (which is a
  16-bits unique identifier that indicates a
  particular virtual circuit on a network).

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VDSL - The Communication Medium

• Unshielded Twister Pair Copper Wires
• - Two insulated copper wires are twisted
  together to reduce the electrical interference,
  which occurs as noise,
• - Telephone lines include 1 pair
• DSL Tranciever ? Central Office,
• - UTP cables used in LAN wiring include 4 pairs
  
• Clients Computer ? DSL Tranciever.

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VDSL - The Communication Medium (continued)

• Radio Frequency (RF) Transmissions
• - Provided through Radio Frequency (RF) Modems
  Wireless Modems
• Clients Computer ? DSL Tranciever.

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VDSL - The Communication Medium (continued)

• Optical Fiber
• A glass or plastic fiber designed to guide light
  along its length,
• Fibers are used instead of metal wires because
  light travels along them with less loss and they
  are immune to electromagnetic interference.
• DSL Tranciever ? Central Office.

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VDSL - The Communication Medium (continued)

• The key to VDSL as the communication medium
• - The telephone companies are replacing many of
  their main feeds with fiber-optic cable,
• - Many phone companies are planning Fiber to the
  Curb (FTTC), which means that they will replace
  all existing copper lines right up to the point
  where your phone line branches off at your house,

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VDSL - The Communication Medium (continued)

• - Most companies expect to implement Fiber to
  the Neighborhood (FTTN),
• - Instead of installing fiber-optic cable along
  each street, FTTN has fiber going to the main
  junction box for a particular neighborhood.
• Therefore, the distance obstacle of VDSL will be
  overcome!

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VDSL The Standards

• TCP / IP
• The Internet protocol suite is the set of
  communications protocols that implement the
  protocol stack on which the Internet and most
  commercial networks run,
• Named afer Transmission Control Protocol (TCP)
  and the Internet Protocol (IP), which were also
  the first two networking protocols defined,
• The Internet Protocol suit can be viewed as a set
  of layers (consists of 5 layers).

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VDSL The Standards (continued)

• PPP
• The Point-to-Point Protocol (PPP) is a data link
  protocol commonly used to establish a direct
  connection between two nodes over serial cable,
  phone line, trunk line, cellular telephone,
  specialized radio links, or fiber optic links,
• Most Internet service providers use PPP for
  customers' dial-up access to the Internet,
• PPP is used in a similar role with Digital
  Subscriber Line (DSL) Internet service,

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VDSL The Standards (continued)

• Two common forms of PPP,
• 1) Point-to-Point Protocol over Ethernet (PPPoE)
  (mainly used)
• 2) Point-to-Point Protocol over ATM (PPPoA).

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VDSL The Standards (continued)

• DMT
• DMT Discrete MultiTone,
• Carrier system that most of the VDSL equipments
  use today,
• DMT divides signals into 247 separate channels,
  each 4 kilohertz (KHz) wide,
• Each channel is monitored and if the quality is
  too impaired, the signal is shifted to another
  channel,

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VDSL The Standards (continued)

• This system constantly shifts signals searching
  for the best channels for transmission and
  reception,
• Some of the lower channels (those starting at
  about 8 KHz) are used as bidirectional channels
  for both upstream and downstream information.

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VDSL - The Advantages over other WAN Technologies

• Internet connection by existing infrastructure
  (telephone line).
• Using telephone line for Internet access as well
  as for phone conversation at the same time.
• Active permanent connection without minute charge
  (unlike temporary connections established by a
  Dial-up Modem).
• Active permanent connection with fixed monthly
  fee.

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VDSL - The Advantages over other WAN Technologies
(continued)

• Catches the speed of the Cable Internet.
• Its high speed! 52 Mbps downstream and 16 Mbps
  upstream.
• Unlike Cable Internet, the connection speed of
  each client is constant.
• The connection speed doesnt depend on the number
  of users.
• More reliable than the Cable Internet.

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VDSL - The Disadvantages over other WAN
Technologies

• Short distance, about 1,200 m.
• Can be overcome by using fiber optic cable.
• Higher monthly fees than other Internet
  connection technologies.

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VDSL - The Application Areas

• United States
• Europe
• Asia
• Australia
• After fiber optic cables become more common, it
  is intended to be used world wide

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Conclusion

• VDSL is the fastest DSL technology.
• It will become available in Turkey in the
  beginning of the year 2008.
• It may be thought as an improved version of ADSL.
• Distance limitations and high monthly fees effect
  the popularity.

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Conclusion (continued)

• The wide usage of the VDSL technology depends on
  the availability of optical networks technology.
• After these networks become available everywhere,
  a new technology may come up and end the usage of
  VDSL.

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References

• http//www.howstuffworks.com
• http//en.wikipedia.org
• Computer Networks and Internets.
• D.E. Comer, Prentice Hall, 2004.
• Bilkent University
• Computer Technology and Information Systems
• CTIS 451Data Communications and Networking
• Fall 2007 Lecture Notes.

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Questions

• Is VDSL the final cable network technology?
• What other advantages do you think VDSL have?
• Will you consider using VDSL technology in Turkey?