Advances of WAN Technologies

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Advances of WAN Technologies

• Zhangxi Lin
• ISQS 6341

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About SONET

• Not dead yet
• Some companies carry IP, ATM, frame relay and
  Gigabit Ethernet on a SONET transport structure
• Main beef against SONET End users can't scale up
  gradually to get--and pay for--just what they
  need. Another annoyance is that it traditionally
  took weeks and a couple of truck rolls to add to
  any customer's capacity.
• There is a way to provision bandwidth over SONET
  in seconds, and at increments of just 1.5 Mbps.
• The mistake most competitive carriers made is
  strictly focusing on customer touch--having
  facilities in the ground--rather than on the
  profit per megabit. Value-added voice--that's
  high revenue. Video is high revenue
• - May 29, 2001

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IP Over SONET

• A SONET ring provides point-to-point connections
  between routers. IP packets must, therefore, map
  to a point-to-point link, for which the most
  popular solution is using the Point-to-Point
  Protocol (PPP), defined by the IETF in RFC 1661.
• (the technology in 1997)

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IP Over SONET
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IP over DWDM

• IP over DWDM is the concept of transmitting raw
  IP packets over an optical layer, using DWDM for
  its capacity and other operations.
• This new technical solution can increase the
  capacity of existing networks without the need
  for expensive re-cabling and can tremendously
  reduce the cost of network upgrades. This creates
  a vision of an all-optical network where all
  management is carried out in the photonic layer.
• Transmitting IP directly over DWDM holds the key
  to the bandwidth glut and opens the frontier of
  terabit Internets.
• http//www.ari.vt.edu/ece5516/OpticalNetworks/ipdw
  dm.htm

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DWDM (Dense wavelength division multiplexing)

• A technology that puts data from different
  sources together on an optical fiber, with each
  signal carried on its own separate light
  wavelength.
• Up to 80 (and theoretically more) separate
  wavelengths or channel of data can be
  multiplexing into a lightstream transmitted on a
  single optical fiber. In a system with each
  channel carrying 2.5 Gbps (billion bits per
  second), up to 200 billion bits can be delivered
  a second by the optical fiber.
• Sometimes called wave division multiplexing
  (WDM). Since each channel is demultiplexed at the
  end of the transmission back into the original
  source, different data formats being transmitted
  at different data rates can be transmitted
  together. Specifically, Internet (IP) data,
  Synchronous Optical Network data, and
  asynchronous transfer mode data can all be
  traveling at the same time within the optical
  fiber.
• Promises to solve the "fiber exhaust" problem and
  is expected to be the central technology in the
  all-optical networks of the future.
• Replaces time-division multiplexing
  (Time-Division Multiplexing) as the most
  effective optical transmission method. Although
  TDM is the primary approach in today's networks,
  DWDM systems were tested and deployed in late
  1998 and 1999.

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DWDM The Solution for the next generation
Internet (NGI)

• If one million families decide they want to see
  video on Web sites and sample the new emerging
  video applications, then network transmission
  rates of terabits (trillions of bits per second
  Tbps) are required. With a transmission rate of
  one Tbps, it is possible to transmit 20 million
  simultaneous 2-way phone calls or transmit the
  text from 300 yearsworth of daily newspapers per
  second.
• For some applications the time sensitivity is so
  important that minimum delay is the overriding
  factor for all protocol and equipment design
  decisions. So, there is a need for Burst mode
  optical data switching.
• Many transmission protocols require that data
  packets traverse the network only after a circuit
  has been established. For some applications, such
  as periodic transmission of sensor data, this may
  be an unnecessary overhead to impose.

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Multi-layer Stack
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Disadvantages of Multi-layer Stack

• The multi-layer stack has more problems than
  advantages
• Every layer now runs at its own speed. So, low
  speed devices cannot fill the wavelength
  bandwidth.
• Increasing Bandwidth, due to this technological
  revolution, Core technologies are pushed to the
  edges.
• Functional overlap So many layers are doing the
  same thing, e.g. routing.
• A failure affects many layers

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IP and DWDM - A Winning Combination

• The good news about optical networking is that it
  lets carriers deliver huge amounts of bandwidth.
  The bad news is that it's hard to get money out
  of those fat pipes. But now, with ATM and
  SONET/SDH out of the way revenue generating
  services (which were struggling till now) like IP
  virtual private networks (VPN) and voice over IP
  (VOIP) will gain direct access to DWDM resources,
  and will finally become practical.

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Advantages of IP over DWDM

• Less latency
• Automatic provision
• Unified bandwidth service
• Improved QoS

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Challenges

• Any pair of photonic transmission paths cannot
  use the sane wavelength on a shared fiber link.
  An algorithm needs to be devised which could
  route more than 1 line on the same wavelength.
• There is limited address space arising from
  physical addressing i.e. there is a finite number
  of accessible wavelengths.

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Multi-Protocol Lambda Switching (MPLambdaS)

• Lambda switching is derived from Multi-Protocol
  Label Switching (MPLS). We can assume MPLambdaS
  to be just implementing Label Switching in the
  Optical domain.
• A DWDM network (implementing Lambda switching) is
  analogical to an ATM network in the aspects of
  switching. ATM networks perform packet switching
  based on the virtual circuit number, while the
  optical channel layer performs switching based on
  the wavelength of the signal (or packet). Hence
  the name "Lambda Switching" is applied to the
  optical network.

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The Way to All-Optical Network

• DWDM is just the first step on the road to full
  optical networking and the realization of the
  optical layer. The concept of an All-optical
  network implies that the service provider will
  have optical access to traffic at various nodes
  in the network, much like the SONET layer for
  SONET traffic. Optical wavelength add/drop (OWAD)
  offers that capability, where wavelengths are
  added or dropped to or from a fiber, without
  requiring a SONET terminal. Combined with OWAD
  and DWDM, the optical cross-connect (OXC) will
  offer service providers the ability to create a
  flexible, high-capacity, efficient optical
  network with full optical bandwidth management.

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Conclusions

• The future holds many challenges to the
  All-optical networks. But, the commercial
  implementations for IP over DWDM are not far
  away. It provides the backbone to support
  existing and emerging technologies with almost
  limitless amounts of bandwidth capacity and opens
  the pathway to Terabit networking.
• The trend of IP/DWDM solutions over the last few
  years seems to have taken an exponential growth.
  All-optical networking (not just point-to-point
  transport) enabled by Optical Cross-Connects,
  Optical programmable add/drop multiplexers, and
  Optical switches provides a unified
  infrastructure capable of meeting the
  telecommunications demands of today and tomorrow.
  
• Transparently moving trillions of bits of
  information efficiently and cost effectively will
  enable service providers to maximize their
  embedded infrastructure and position themselves
  for the capacity demand of the future.

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References

• ATM tutorial at IEC proforum www.iec.org/tutorials
  /atm_fund/index.htmlDescribes at length ATM
  technology, ATM classes of services High-speed
  local-area network (LAN) interconnection ATM
  standards, ATM multimedia applications in voice,
  video etc.
• Sonet tutorial at IEC proforum www.iec.org/tutoria
  ls/sonetThis Primer provides an introduction to
  the SONET standard, based on the latest
  information available from the Bellcore and
  International Telecommunications
  UnionTelecommunications Standardization Sector
  (ITUT) standards organizations.
• DWDM tutorial at IEC proforum www.iec.org/tutorial
  s/dwdmThis tutorial addresses the importance of
  scalable DWDM systems in enabling service
  providers to accommodate consumer demand for
  ever-increasing amounts of bandwidth.   
• Talk by Dr.Raj Jain on IP over DWDM
  www.netlab.ohio-state.edu/talks/h_aipwd.htm This
  streaming video lecture discusses a gamut of
  issues starting from the need for IP over DWDM to
  the requirements for creating an all optical
  networks based on Multi- protocol lambda
  switching(MPLS).