Module 3
Local and Wide Area Networks Architecture
Submitted To:
Dr. Refre
Submitted By:
Yap, Nelson M.
IM-520
Local and Wide Area Networks Architecture
Network architecture, is the logical and structural layout of
the network consisting of transmission equipment, software
and communication protocols and infrastructure (wired or
wireless) transmission of data and connectivity between
components.
There are 4 different network topology: star network, a bus
or line network, a loop or ring network, (hierarchical) or a
mesh network.
The different topologies can be arranged in different
fashion described as LAN (Local Area Network), MAN (Metropolitan Area Network) and WAN
(Wide Area Network) where the network extends over a local area (<1 km), metropolitan (<100
km) and long distance.
wireless LAN (WLAN or Wireless Local
Area Network)
A wireless LAN (or WLAN, for wireless local area network,
sometimes referred to as LAWN, for local area wireless
network) is one in which a mobile user can connect to a
local area network (LAN) through a wireless (radio)
connection. The IEEE 802.11 group of standards specify
the technologies for wireless LANs. 802.11 standards use
the Ethernet protocol and CSMA/CA (carrier sense
multiple access with collision avoidance) for path sharing
and include an encryption method, the Wired Equivalent
Privacy algorithm.
High-bandwidth allocation for wireless will make possible a relatively low-cost wiring of
classrooms in the United States. A similar frequency allocation has been made in Europe.
Hospitals and businesses are also expected to install wireless LAN systems where existing LANs
are not already in place.
Using technology from the Symbionics Networks, Ltd., a wireless LAN adapter can be made to fit
on a Personal Computer Memory Card Industry Association (PCMCIA) card for a laptop or
notebook computer.
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Local and Wide Area Networks Architecture
metropolitan area network (MAN)
A metropolitan area network (MAN) is a network that
interconnects users with computer resources in a
geographic area or region larger than that covered by even a
large local area network (LAN) but smaller than the area
covered by a wide area network (WAN). The term is
applied to the interconnection of networks in a city into a
single larger network (which may then also offer efficient
connection to a wide area network). It is also used to mean
the interconnection of several local area networks by
bridging them with backbone lines. The latter usage is also
sometimes referred to as a campus network.
Examples of metropolitan area networks of various sizes can be found in the metropolitan areas
of London, England; Lodz, Poland; and Geneva, Switzerland. Large universities also sometimes
use the term to describe their networks. A recent trend is the installation of wireless MANs.
Campus Area Network (CAN)
A campus area network (CAN) is a computer network
interconnecting a few local area networks (LANs)
within a university campus or corporate campus.
Campus area network may link a variety of campus
buildings including departments, the university library
and student halls of residence. A campus area network
is larger than a local area network but smaller than a
metropolitan area network (MAN) or wide area
network (WAN). CAN can also stand for corporate area
network.
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Local and Wide Area Networks Architecture
storage area network (SAN)
A storage area network (SAN) is a high-speed
special-purpose network (or
subnetwork)
that
interconnects different kinds of data storage devices
with associated data servers on behalf of a larger
network of users.
Typically, a storage area network is part of the
overall network of computing resources for
an enterprise. A storage area network is usually
clustered in close proximity to other computinsg
resources such as IBM z990 mainframes but may
also extend to remote locations forbackup and
archival storage, using wide area network carrier
technologies such as ATM or SONET.
A storage area network can use existing communication technology such as IBM's optical
fiber ESCON or use Fibre Channel technology. Some SAN system integrators liken it to the
common storage bus (flow of data) in a personal computer that is shared by different kinds of
storage devices such as a hard disk or a CD-ROM player.
SANs support disk mirroring, backup and restore, archival and retrieval of archived data, data
migration from one storage device to another and the sharing of data among different servers in a
network. SANs can incorporate subnetworks with network-attached storage (NAS) systems.
System Area Network (SAN)
System Area Networks deliver very high bandwidth
(more than 1 GB/second) with very low latency.
SANs are switched, with a typical hub supporting 48 nodes. You can build larger networks from
cascading hubs. Cable length limitations can vary
from a few meters to a few kilometers.
A SAN is typically used to interconnect nodes
within a distributed computer system, such as a
cluster. These systems are members of a common
administrative domain and are usually in close
physical proximity. A SAN is assumed to be
physically secure.
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Local and Wide Area Networks Architecture
These new interconnections differ from existing high-performance media, such as Gigabit
Ethernet and ATM, in several ways. SAN network adapters implement reliable transport service,
akin to TCP or SPX, directly in hardware. The network adapter controller exposes individual
transport endpoints and demultiplexes incoming packets accordingly. Each endpoint is usually
represented by a set of memory-based queues and registers that are shared by the host processor
and the network adapter controller. Many SAN network adapter controllers permit these
endpoint resources to be mapped directly into the address space of a user-mode process. Program
processes can post messaging requests directly to the hardware, with no system calls and no
intermediate data copying. Fully reliable SAN network adapter controllers, with direct user-mode
access,
can
deliver
extremely
good
message-passing
performance.
SANs have very low error rates. SANs are often made highly available by using redundant
interconnect fabrics. SAN performance more closely resembles that of a memory subsystem than a
traditional network, such as a LAN.
SANs provide bulk data transfer through a Remote Direct Memory Access (RDMA) mechanism.
The initiator specifies a buffer on the local system and a buffer on the remote system. Data is then
transferred directly between the two locations by the network adapters without host CPU
involvement at either end. Both read (get) and write (put) transfers can be supported. The remote
address must be prearranged through a message exchange. Some designs also permit the transfer
of a small amount of immediate data on RDMA operations. This data is delivered to the remote
process when the RDMA transfer has finished and is used in lieu of a subsequent message.
A new specification has been implemented in Winsock called "Windows Sockets Direct Path"
(WSDP) for SANs. This new technology enables Windows Sockets programs that use TCP/IP to
obtain the performance benefits of SANs without program modifications.
A new layer called "switch" is inserted between Windows Sockets Interface and Windows Sockets
Service Providers (Microsoft Base Winsock Provider and SAN Winsock Provider). This
component emulates TCP/IP semantics over native SAN service providers. It is referred to as the
"switch" because it transparently switches between the standard TCP/IP Windows Sockets
provider and SAN providers on a per-socket basis.
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