CIM6400 CTNW
Lesson 9 – LAN Architectures &
Networking Protocols and the OSI Model
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LAN Architectures
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Ethernet
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Architecture refers to the overall structure of a computer or communication
system. It determines the capabilities and limitations of the system.
The Ethernet architecture is based on the IEEE 802.3 standard. The IEEE
802.3 standard specifies that a network implements the Carrier Sense
Multiple Access with Collision Detection (CSMA/CD) access control
method.
Standard transfer rates are 10 Mbps or 100 Mbps, but new standards provide
for gigabit Ethernet, which are capable of attaining speeds up to 1 Gbps over
fiber-optic cable or other high-speed media.
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Ethernet
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10BASE-T uses a star topology.
The 10 stands for the common
transmission speed of 10 Mbps, the
"BASE" stands for baseband mode, and
the "T" stands for twisted pair cabling.
Ethernet cable generally describes the
UTP cabling, but STP cable can also be
used.
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Ethernet
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100BASE-X (also called Fast Ethernet)
comes in several different varieties.
It can be implemented over 4-pair
Category 3, 4, or 5 UTP (100BASE-T).
It can also be implemented over 4-pair
Category 5 UTP or Shielded Twisted Pair
(STP) (100BASE-TX), or as Ethernet
over 2-strand fiber-optic cable
(100BASE-FX).
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Ethernet
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1000BASE-T is Gigabit Ethernet.
This architecture supports data transfer rates of 1 Gbps.
Its implementation over fiber-optic cable makes it suitable for metropolitanarea networks (MANs).
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Token Ring
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The Token Ring standards are defined in
IEEE 802.5.
It is often integrated with IBM mainframe
systems such as AS400.
Token Ring is so named of its logical
topology and its MAC method of token
passing. The transfer rate for Token Ring
can be either 4Mbps or 16Mbps.
A Token Ring network uses a token (that
is, a special signal) to control access to the
cable.
 A token is initially generated when the first
computer on the network comes online.
 When a computer wants to transmit, it
waits for and then takes control of the
token when it comes its way.
 The token can travel in either direction
around the ring, but only in one direction at
a time.
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Fiber Distributed Data Interface (FDDI)
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FDDI is a type of Token Ring network.
It runs on fiber-optic cable, and thus
combines high-speed performance with
the advantages of the token-passing ring
topology.
It runs at 100 Mbps, and its topology is a
dual ring.
The outer ring is called the primary ring
and the inner ring is called the secondary
ring.
Normally, traffic flow only on the
primary ring. If primary ring fails, the
data automatically flows onto the
secondary ring in the opposite direction
(fault tolerance).
Advantages
 High speed fiber-optic transmission
 Not susceptible to EMI and noise
 Send data for greater distances between
repeaters
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Networking Protocols and the OSI Model
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OSI Model Overview
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The Open Systems Interconnection
(OSI) reference model is an industry
standard framework that is used to
divide the functions of networking into
seven distinct layers.
Each layer provides specific services
to the layers above and below it in
order for the network to work
effectively.
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OSI Model Overview
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A message begins at the top application layer and moves down the OSI layers to the
bottom physical layer.
As the message descends, each successive OSI model layer adds a header to it.
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OSI Model Overview
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A header is layer-specific information that
basically explains what functions the layer
carried out.
Conversely, at the receiving end, headers
are striped from the message as it travels
up the corresponding layers.
The process of data being encapsulated on
the sending end and data being deencapsulated on the receiving end is the
function of the OSI model.
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OSI Model Layer and Their Functions
• The OSI model was intended to be a reference model for developing
networking protocols.
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What is a Protocol?
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Protocol is a controlled sequence of
messages that is exchanged between two
or more systems to accomplish a given
task.
Protocol specifications define this
sequence together with the format or
layout of the messages that are
exchanged.
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Transmission Control Protocol/Internet
Protocol
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Internet
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The Transmission Control
Protocol/Internet Protocol (TCP/IP)
suite of protocols has become the
dominant standard for internetworking.
TCP/IP represents a set of public
standards that specify how packets of
information are exchanged between
computers over one or more
networks.
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Transmission Control Protocol/Internet
Protocol
Internet
Internet
Internet
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Transmission Control Protocol/Internet
Protocol
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Application Protocols
 Hypertext Transfer Protocol (HTTP)
• Govern how files – such as text, graphics, sounds and video – are
exchanged on the Internet.
• A web server runs an HTTP services or daemon. A daemon is a
program that services HTTP requests.
 Hypertext Markup Language (HTML)
• A page-description language
• Web designers use HTML to indicate to web browser software
how the page should look.
 Telnet
• Enables terminal access to local or remote systems
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Transmission Control Protocol/Internet
Protocol
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Application Protocols (Cont.)
 File Transfer Protocol (FTP)
• Provides services for file transfer and manipulation. FTP uses the
session layer to allow multiple simultaneous connections to remote
file system
 Simple Mail Transport Protocol (SMTP)
• Provides messaging services over TCP/IP and supports most
Internet e-mail programs.
 Domain Name System (DNS)
• Provides access to name servers, where network names are
translated to the addresses used by Layer 3 network protocols.
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Transmission Control Protocol/Internet
Protocol
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Transport Protocols
 Transmission Control Protocol (TCP)
• Facilities for end-to-end connection establishment, error detection
and recovery, and metering the rate of data flow into the network
(i.e. for reliable delivery of data)
 User Datagram Protocol (UDP)
• Offers a connectionless service to applications
• Uses lower overhead than TCP
 Both TCP & UDP identify applications by port number
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Transmission Control Protocol/Internet
Protocol
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Internet Protocols
 Internet Protocol (IP) address
• Provides source and destination addressing. In conjunction with
routing protocols, the IP address provides packet forwarding from
one network to another
 Internet Control Message Protocol (ICMP)
• Used for network testing and trouble-shooting, it enables
diagnostic and error messages
 Routing Information Protocol (RIP)
• Operates between router devices to discover paths between
networks
 Address Resolution Protocol (ARP)
• Maps an IP address to a physical machine address
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Internetwork Packet
Exchange/Sequenced Packet Exchange
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Internetwork Packet
Exchange/Sequenced Packet
Exchange (IPX/SPX) is the protocol
suite employed originally by
Novell®, NetWare.
It delivers functions similar to those
included in TCP/IP.
The native – or original – NetWare
protocols remained proprietary
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NetBEUI
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NetBIOS Extended User Interface (NetBEUI) is a protocol used primarily
on small Windows NT networks.
It was used earlier as the default networking protocol in Windows 3.11,
Windows for Workgroups, and LAN manager.
NetBEUI is a simple protocol that lacks many of the features that enable
protocol suites such as TCP/IP to be used on networks of almost any size.
NetBEUI cannot be used to build large networks or to connect several
networks. However, it is suitable for small peer-to-peer networks.
It can be used in conjunction with another routable protocol such as
TCP/IP.
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AppleTalk
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AppleTalk is a protocol suite that is
used to network Macintoch
computers.
AppleTalk is comprised of a set of
protocols that span the seven layers of
the OSI reference model.
AppleTalk protocols were designed to
run over the major LAN types,
notably Ethernet and Token Ring, and
also Apple's own LAN physical
topology, LocalTalk.
Like Novell, Apple Computer also
developed its own proprietary
protocol suite to network Macintosh
computers.
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