Transcript TDC 363 Local Area Networks

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
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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
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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
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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 voicedesigned 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
• Let’s 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 user’s frame is
marked with a VLAN tag as it enters the
network
• This tag keeps each user’s 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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Yipes…that’s fast!
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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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Yipes…that’s 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
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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 LAN
Experience
• 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 IETF’s 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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