TDC 363 Local Area Networks

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TDC 363 Local Area Networks

• Metropolitan Area Networks (MAN)

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MAN Definition

• Not a precise definition available
• Somewhere between a LAN and a WAN with some
  features of each
• Serves a geographic area larger than a LAN, such
  as a city or metropolitan region

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Definition Continued

• MANs can interconnect various sites for one
  company, or interconnect many companies
• MANs transfer data at LAN speeds (and higher) but
  often use more complicated protocols

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MAN Application Areas

• Interconnection and consolidation of corporate
  data centers
• Transparent extension of the LAN by
  interconnecting distributed corporate locations
• Support of SAN (storage area networks)
• Server-less offices

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MAN Application Areas

• Real-time transaction backups
• High-speed disaster recovery
• Interconnection between corporate data center and
  ISP
• Government, business, medicine and education
  high-speed interconnections

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SANs

• Latest evolution of mass data storage for large
  corporations and institutions
• Normally data storage is attached to the LAN via
  a server
• But with a SAN high-volume disk arrays and tape
  storage occupy a network separate, but connected
  to, a LAN

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MAN Features

• Why use a MAN?
• Very high speeds (Gbps possible)
• Self-healing networks
• Bandwidth on demand
• MANs cover distances that LANs cannot
• But MANs often provide a lower level of
  complexity than many WANs

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MAN Topologies

• Point-to-point
• Characterized by very high speeds (10 to 40 Gbps)
• Often DWDM over fiber
• Redundancy is provided at the card level -
  parallel fiber links with redundant equipment at
  the endpoints

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MAN Topologies

• Ring
• Most common architecture
• Can span tens of kilometers
• Data rates range from 622 Mbps to 10 Gbps per
  channel
• SONET rings a typical example
• Multiple rings with very fast failover provide
  stability

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MAN Topologies

• Mesh
• The future of MANs?
• A natural extension of point-to-point MANs
• Can also connect to established rings
• High speeds, long distances, good redundancy

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Support Technologies

• SONET/SDH
• ATM
• Gigabit Ethernet
• IP
• Fibre Channel
• FDDI

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Support Technology - SONET

• Currently most MANs are supported by SONET rings
• SONET is the fundamental transmission technology
  for both TDM-based circuit switched networks, and
  most overlay data networks
• Unfortunately, SONET has a number of shortcomings

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Support Technology - SONET

• SONET disadvantages
• Still fairly expensive
• Problems adapting data services to the
  voice-designed and voice-optimized hierarchy
• Inflexible multiplexing hierarchy (SONET
  increments in terms of DS-0s / DS-1s)
• SONET cannot be provisioned dynamically

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Support Technology - ATM

• Favored by many service providers because it can
  support different protocols and different traffic
  types into a common protocol format for
  transmission over SONET
• Unfortunately, ATM is complex, costly, and
  provides an extra layer of complexity

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Support Technology - Gigabit Ethernet

• A very interesting newcomer to MAN technology
• A very common and well-understood technology
• Can scale from 10 Mbps, 100 Mbps, 1000 Mbps, to
  10 Gbps easily
• Low cost
• No need for ATM or SONET

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Support Technology - IP

• Almost entire data world uses IP
• Also well known, widely adopted, reasonably
  flexible, relatively simple
• IP is a layer 3 protocol, so question is IP over
  ATM over SONET? IP over SONET? IP over Ethernet?

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Support Technology - Fibre Channel

• Predominant data link technology used in SANs
• Economical replacement for SCSI
• Interfaces available at 100 MBps with 200 MBps
  soon and 400 MBps testing
• Does not have a short distance limitation like
  SCSI
• Found in point-to-point, mesh, and arbitrated
  loops

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Support Technology - FDDI

• Basically a legacy technology
• Being replaced by Gigabit Ethernet or ATM
• Can be transparently transported over the optical
  layer using DWDM

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SONET vs. Gigabit Ethernet

• Lets examine the two more interesting support
  technologies
• Why more interesting?
• SONET is the ruler
• Gigabit Ethernet is trying to dethrone that ruler

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SONET vs. Gigabit Ethernet

• Ethernet is 10 times less expensive than current
  SONET technology
• Ethernet is a simple and widely understood
  technology
• Ethernet is the best technology for carrying IP
  traffic - IP and Ethernet have matured together

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SONET vs. Gigabit Ethernet

• Optical Ethernet can support links in the network
  range from 3 to 6 miles using single mode 1310
  nm wavelength and up to 43.4 miles for 1550 nm
  wavelength
• Optical Ethernet can segregate traffic of
  different users and deliver the particular
  service level each user purchases

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SONET vs. Gigabit Ethernet

• Traffic segregation is accomplished by using the
  IEEE 802.1pQ VLAN standard
• With this standard, each users frame is marked
  with a VLAN tag as it enters the network
• This tag keeps each users traffic separate as it
  crosses the network

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SONET vs. Gigabit Ethernet

• Optical Ethernet can also deliver guaranteed
  levels of latency, jitter, and bandwidth
• To provide these levels of latency and jitter,
  IETF created the Differentiated Services
  (Diff-Serv) project
• Diff-Serv - as each frame enters a network,
  information from the frame is used to assign it
  to a particular class of service

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SONET vs. Gigabit Ethernet

• User contracts also specify bandwidths, which
  network operators guarantee by limiting the
  aggregate of guarantees to network capacity
  (similar to frame relay and ATM)

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SONET vs. Gigabit Ethernet

• One of the big advantages of Gigabit Ethernet
  over SONET is the levels of complexity
• SONET has multiple layers - the router network
  running over the ATM network running over the
  SONET network running over a collection of
  point-to-point DWDM links

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SONET vs. Gigabit Ethernet
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SONET vs. Gigabit Ethernet

• Gigabit Ethernet, however, does not have all the
  levels, making the technology much simpler and
  much less expensive

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SONET vs. Gigabit Ethernet
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Yipesthats fast!

• 15 months old (as of Fall 2000)
• Up and running in 20 cities
• A disruptive approach to networking
• The first fully managed, all-IP regional optical
  networks using Gigabit Ethernet for linking
  businesses to eadch other and to the Internet

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Yipesthats fast!

• Fully scalable bandwidth-on-demand from 1 Mbps up
  to 1 Gbps in 1 Mbps increments
• Busting the regional bandwidth bottleneck between
  corporate LANs and cross-country fiber networks
  to drive a new generation of bandwidth-intensive
  applications
• Unprecedented levels of customer control via the
  Yipes Care Service Portal

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Yipes - Typical Regional Network

• Diversely sourced dark fiber
• Concatenated local access loops
• Less than 10 ms latency regional ring
• Multiple peering arrangements
• Several WAN connections
• 24x7 redundant monitoring

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Yipes - Extending the LANExperience

• Fiber to business locations
• Familiar computing environment
• Granular bandwidth increments - 1 Mbps to 1 Gbps
  in 1 Mbps increments
• Scalability on demand - no forklift upgrade -
  upgrade with a phone call, and soon with via a
  Web site

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Yipes - QoS

• Traffic engineering
• know bandwidth at access points and in metro
  network for all customers
• no over subscribing
• IEEE standard (802.1pQ) for VLANs
• identify customer packets with different tags
• prioritize packets

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Yipes - QoS

• Hardware
• equipment has separate queues and can prioritize
  frames
• Can prioritize at IP layer
• Based on IETFs Diff-Serv

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Yipes - Security, Survivability and Reliability

• Security
• Layer 2 switching using VLAN tags based on IEEE
  802.1q/p
• Survivability
• Dual fiber entrance to customer premises
• Failover
• 2-3 seconds for layer 3 routing
• 30 - 40 seconds for layer 2 bridging/switching (5
  seconds in future)
• Reliability
• 99.99 migrating to 99.999 by mid 2001

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