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CHAPTER 1
NETWORKING BASICS
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What is a Network?
A network consists of two or more computers that are linked in order to share
resources (such as printers and CD-ROMs), exchange files, or allow electronic
communications. The computers on a network may be linked through cables,
telephone lines, radio waves, satellites, or infrared light beams.
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1. LAN (LOCAL AREA NETWORK)
2. CAN (CAMPUS AREA NETWORK)
3. MAN (METROPOLITAN AREA NETWORK)
4. WAN (WIDE AREA NETWORK)
TYPES OF NETWORK
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CABLES AND STANDARDS USED FOR LAN NETWORK
CAT 3, 4 AND 5
IBM TYPE 1-9 CABLING STANDARDS
EIA568A AND 568B
ETHERNET CABLING STANDARDS: IEEE 802.3 (10base5),
IEEE 802.3a(10base2)
IEEE 802.3i(10baset)
UNSHEILDED TWISTED PAIR (UTP)
SHIELDED TWISTED PAIR (STP)
CONNECTORS: RJ-45, RJ-11, RS-232, BNC
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HARDWARE DEVICES USED IN LAN
NICs (NETWORK INTERFACE CARDS)
REPEATERS
ETHERNET HUBS
TOKEN RING
BRIDGES
BROUTERS
ROUTERS
GATEWAYS
PRINT SERVERS
FILE SERVERS
SWITCHES
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PEER to PEER NETWORK
Peer-to-peer network operating systems allow users to share resources and files
located on their computers and to access shared resources found on other computers.However, they do not have a file server or a centralized management source (See the
figure below). In a peer-to-peer network, all computers are considered equal; they all
have the same abilities to use the resources available on the network. Peer-to-peer
networks are designed primarily for small to medium local area networks.
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Client/Server
Client/server network operating systems allow the network to centralize functions andapplications in one or more dedicated file servers (See the figure below). The file
servers become the heart of the system, providing access to resources and providing
security. Individual workstations (clients) have access to the resources available on the
file servers. The network operating system provides the mechanism to integrate all the
components of the network and allow multiple users to simultaneously share the same
resources irrespective of physical location
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CAMPUS AREA NETWORK
Campus Area Network or CAN is a network spread over a limited geographical area
such as an university. Cables as the communication medium, and a device that can
interface various patches of LANs across the campus. Once such device is the LAN
extender.
Cable 1: Power adapter
Cable 2: RJ45 Ethernet port. You could either connect the LAN extender directly to a
PC using a cross-over cable, or connect it to an Ethernet hub or switch using a straight
through cable.
Cable 3: Console port. Initial configuration of the LAN Extender is done by connecting
it to a free COM port on your PC using a RS232 cable.
Cable 4: RJ11 Telephone cable. A plain two-wire telephone cable serves as the WAN
link between the two LAN Extenders.
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MAN (METROPOLITAN AREA NETWORK)
METROPOLITAN AREA NETWORKS (MAN) ARE NETWORKS THAT
CONNECT LANS TOGETHER WITHIN A CITY.
THE PROTOCOLS USED FOR MAN ARE :-
RS-232, V-35
X.25 (56KBPS), PACKET ASSEMBLETS AND DISSEMBLERS
FRAME RELAY
ASYNCHRONOUS TRANSFER MODE (ATM)
ISDN (INTEGRATED SERVICES DIGITAL NETWORK)
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A typical use of MANs to provide shared access
to a wide area network is shown in thefigure below:
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WAN (WIDE AREA NETWORK)
Wide Area Networks (WANs) connect larger geographic areas, such as Florida, the
United States, or the world. Dedicated transoceanic cabling or satellite uplinks may be
used to connect this type of network.
Using a WAN, schools in Florida can communicate with places like Tokyo in a matter
of minutes, without paying enormous phone bills. A WAN is complicated. It uses
multiplexers to connect local and metropolitan networks to global communicationsnetworks like the Internet. To users, however, a WAN will not appear to be much
different than a LAN or a MAN.
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OSI REFERENCE MODEL
When computers were first linked together into networks, moving information betweendifferent types of computers was a very difficult task.
In the early 1970s, the International Organization of Standards (ISO) recognized the
need for a standard network model. This would help vendors to create interpretable
network devices. The Open Systems Interconnection (OSI) reference model, released in
1984, addressed this need.
The OSI model describes how information makes its way from application programs
through a network medium to another application program in another computer. It
divides this one big problem into seven smaller problems.
Each of these seven problems is reasonably self-contained and therefore more easily
solved without excessive reliance on external information. Each problem is addressedby one of the seven layers of the OSI model.
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The Seven Layers of the OSI model
Application
Presentation
Session
Transport
Network
Data-link
Physical
The lower two OSI model layers are implemented with hardware and software.
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OSI Model
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Data Encapsulation
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APPLICATION LAYER
The application layer of the OSI model is the layer that is closest to the user. Instead of
providing services to other OSI layers, it provides services to application programs
outside the scope of the OSI model. It's services are often part of the application
process. Main functions are:-
identifies and establishes the availability of the intended communication partner.
synchronizes the sending and receiving applications.
establishes agreement on procedures for error recovery and control of data integrity. determines whether sufficient resources for the intended communications exist.
Devices :-
Browsers
Search engines E-mail programs
Newsgroup and chat programs
Transaction services
Audio/video conferencing
Telnet
SNMP
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The presentation layer
It ensures that information sent by the application layer of one system will be readableby the application layer of another system. It provides a common format for
transmitting data across various systems, so that data can be understood, regardless of
the types of machines involved.
The presentation layer concerns itself not only with the format and representation of
actual user data, but also with data structure used by programs. Therefore, the
presentation layer negotiates data transfer syntax for the application layer.
Devices:-
Encryption
EBCDIC and ASCII GIF & JPEG
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The Session LayerThe main function of the OSI model's session layer is to control "sessions", which are
logical connections between network devices. A session consists of a dialog, or data
communications conversation, between two presentation entities. Dialogs can be
simplex (one-way)
half-duplex (alternate)
full-duplex (bi-directional)
Simplex conversations are rare on networks. Half-duplex conversations require a good
deal of session layer control, because the start and end of each transmission need to be
monitored.Most networks are of course capable of full-duplex transmission, but in fact many
conversations are in practice half-duplex.
Devices:-
Some examples of session layer protocols and interfaces are:
Network File System (NFS)
Concurrent database access X-Windows System
Remote Procedure Call (RPC)
SQL
NetBIOS Names
AppleTalk Session Protocol (ASP)
Digital Network Architecture
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The Transport Layer
You can think of the transport layer of the OSI model as a boundary between the upper
and lower protocols. The transport layer provides a data transport service that shields
the upper layers from transport implementation issues such as the reliability of a
connection.
The transport layer provides mechanisms for:-
multiplexing upper layer applications the establishment, maintenance, and orderly termination of virtual circuits
information flow control
transport fault detection and recovery
Devices:-
TCP, UDP, SPX and Sliding Windows.
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The Network LayerLayer three of the OSI model is the network layer.
The network layer sends packets from source network to destination network.
It provides consistent end-to-end packet delivery services to its user, the transport
layer.
In wide area networking a substantial geographic distance and many networks can
separate two end systems that wish to communicate. Between the two end systems the
data may have to be passed through a series of widely distributed intermediary nodes.
These intermediary nodes are normally routers.
Routers are special stations on a network, capable of making complex routing decisions. The network layer is the domain of routing.
Routing protocols select optimal paths through the series of interconnected networks.
Network layer protocols then move information along these paths.
One of the functions of the network layer is "path determination".
Path determination enables the router to evaluate all available paths to a destination and
determine which to use. It can also establish the preferred way to handle a packet.After the router determines which path to use it can proceed with switching the packet.
It takes the packet it has accepted on one interface and forwards it to another interface
or port that reflects the best path to the packet's destination.
Devices:-
IP, IPX, Routers, Routing Protocols (RIP, IGRP, OSPF, BGP etc), ARP, RARP, ICMP.
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The Data-Link Layer
Layer two of the OSI reference model is the data-link layer. This layer is responsible forproviding reliable transit of data across a physical link. The data-link layer is concerned
with
physical addressing; Bridges, Transparent Bridges, Layer 2 Switches
network topology; CDP
line discipline (how end systems will use the network link)
error notification ordered delivery of frames
flow control
Frame Relay, PPP, SDLC, X.25, 802.3, 802.3, 802.5/Token Ring, FDDI.
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The Physical LayerLayer one of the OSI model is the physical layer. The physical layer is concerned with
the interface to the transmission medium. At the physical layer, data is transmitted onto
the medium (e.g. coaxial cable or optical fiber) as a stream of bits.So, the physical layer is concerned, not with networking protocols, but with the
transmission media on the network.
The physical layer defines the electrical, mechanical, procedural, and functional
specifications for activating, maintaining, and deactivating the physical link between
end systems. This layer puts 1's & 0's onto the wire.
Characteristics specified by the physical layer include
voltage levels
timing of voltage changes
physical data rates
maximum transmission distances
physical connectors
Devices:-
Hubs, FDDI Hardware, Fast Ethernet, Token Ring Hardware.
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CHAPTER 2
NETWORK TOPOLOGIES
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CHAPTER 2
NETWORK TOPOLOGIES
What is a Topology?
The physical topology of a network refers to the configuration of cables, computers,
and other peripherals. Physical topology should not be confused with logical topology
which is the method used to pass information between workstations. Logical topologywill be discussed in the Protocol Chapter.
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Main Types of Physical Topologies
The following sections discuss the physical topologies used in networks and otherrelated topics.
Linear Bus
Star
Ring
TreeConsiderations When Choosing a Topology
Summary Chart
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Linear BusA linear bus topology consists of a main run of cable with a terminatorat each end (See
fig. 1). All nodes (file server, workstations, and peripherals) are connected to the linear
cable. Ethernet and LocalTalknetworks use a linear bus topology.
Advantages of a Linear Bus Topology
Easy to connect a computer or peripheral to a linear bus.Requires less cable length than a star topology.
Disadvantages of a Linear Bus Topology
Entire network shuts down if there is a break in the main cable.
Terminators are required at both ends of the backbone cable.
Difficult to identify the problem if the entire network shuts down.
Not meant to be used as a stand-alone solution in a large building
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StarA star topology is designed with each node (file server, workstations, and peripherals)
connected directly to a central networkhub orconcentrator(See fig. 2).Data on a star network passes through the hub or concentrator before continuing to its
destination. The hub or concentrator manages and controls all functions of the network.
It also acts as a repeaterfor the data flow. This configuration is common with twisted
pair cable; however, it can also be used with coaxial cable orfiber optic cable.
Advantages of a Star TopologyEasy to install and wire.
No disruptions to the network then connecting or removing devices.
Easy to detect faults and to remove parts.
Disadvantages of a Star Topology
Requires more cable length than a linear topology.
If the hub or concentrator fails, nodes attached are disabled.More expensive than linear bus topologies because of the cost of the concentrators.
The protocols used with star configurations are usually Ethernet orLocalTalk. Token
Ring uses a similar topology, called the star-wired ring.
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Ring Topology
A star-wired ring topology may appear (externally) to be the same as a star topology.Internally, the MAU (multistation access unit) of a star-wired ring contains wiring that
allows information to pass from one device to another in a circle or ring. The Token
Ringprotocol uses a star-wired ring topology.
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TreeA tree topology combines characteristics of linear bus and star topologies. It consists of
groups of star-configured workstations connected to a linear bus backbone cable. Tree
topologies allow for the expansion of an existing network, and enable schools toconfigure a network to meet their needs.
Advantages of a Tree Topology
Point-to-point wiring for individual segments.
Supported by several hardware and software venders.
Disadvantages of a Tree Topology
Overall length of each segment is limited by the typeof cabling used.
If the backbone line breaks, the entire segment goes down.
More difficult to configure and wire than other topologies
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MESH TOPOLOGY
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Hierarchical Topology
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Physical
Topology
Common Cable Common Protocol
Linear Bus Twisted PairCoaxialFiber
EthernetLocalTalk
Star Twisted PairFiber
EthernetLocalTalk
Star-Wired
Ring
Twisted Pair Token Ring
Tree Twisted PairCoaxialFiber
Ethernet
Summary Chart:
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CHAPTER 3
NETWORK TECHNOLOGY
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ETHERNET
The termEthernetrefers to the family of local-area network (LAN) products covered
by the IEEE 802.3 standard that defines what is commonly known as the CSMA/CD
protocol. Three data rates are currently defined for operation over optical fiber and
twisted-pair cables:
10 Mbps10Base-T Ethernet
100 MbpsFast Ethernet
1000 MbpsGigabit Ethernet
10-Gigabit Ethernet is under development and will likely be published as the IEEE
802.3ae supplement to the IEEE 802.3 base standard in late 2001 or early 2002.
Other technologies and protocols have been touted as likely replacements, but the
market has spoken. Ethernet has survived as the major LAN technology (it is currently
used for approximately 85 percent of the world's LAN-connected PCs and
workstations) because its protocol has the following characteristics: Is easy to understand, implement, manage, and maintain
Allows low-cost network implementations
Provides extensive topological flexibility for network installation
Guarantees successful interconnection and operation of standards-compliant products,
regardless of manufacturer
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EthernetABriefHistory
The original Ethernet was developed as an experimental coaxial cable network in the
1970s by Xerox Corporation to operate with a data rate of 3 Mbps using a carrier sensemultiple access collision detect (CSMA/CD) protocol for LANs with sporadic but
occasionally heavy traffic requirements. Success with that project attracted early
attention and led to the 1980 joint development of the 10-Mbps Ethernet Version 1.0
specification by the three-company consortium: Digital Equipment Corporation, Intel
Corporation, and Xerox Corporation.
The original IEEE 802.3 standard was based on, and was very similar to, the EthernetVersion 1.0 specification. The draft standard was approved by the 802.3 working group
in 1983 and was subsequently published as an official standard in 1985 (ANSI/IEEE
Std. 802.3-1985). Since then, a number of supplements to the standard have been
defined to take advantage of improvements in the technologies and to support additional
network media and higher data rate capabilities, plus several new optional network
access control features.Throughout the rest of this chapter, the termsEthernetand 802.3 will refer exclusively
to network implementations compatible with the IEEE 802.3 standard.
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Ethernet Network Elements
Ethernet LANs consist of network nodes and interconnecting media. The network nodes
fall into two major classes: Data terminal equipment (DTE)Devices that are either the source or the
destination of data frames. DTEs are typically devices such as PCs, workstations, file
servers, or print servers that, as a group, are all often referred to as end stations.
Data communication equipment (DCE)Intermediate network devices that receive
and forward frames across the network. DCEs may be either standalone devices such as
repeaters, network switches, and routers, or communications interface units such as
interface cards and modems.
Throughout this chapter, standalone intermediate network devices will be referred to as
eitherintermediate nodes orDCEs. Network interface cards will be referred to asNICs.
The current Ethernet media options include two general types of copper cable:
unshielded twisted-pair (UTP) and shielded twisted-pair (STP), plus several types ofoptical fiber cable
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802.3 (Ethernet)
This standard specifies a network that uses a bus topology, base band signaling, and a
CSMA/CD network access method. This standard was developed to match the Digital,
Intel, and Xerox (DIX) Ethernet networking technology. So many people implemented
the 802.3 standard, which resembles the DIX Ethernet, that people just started calling it
Ethernet. It is the most widely implemented of all the 802 standards because of itssimplicity and low cost.
EthernetSpeeds - 10, 100, or 1000 Mbps
Access - CSMA/CD
Topologies - Logical bus
Media - Coaxial or UTP
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10BASE-T
Speeds - 10Mbps
Signal type - base band
Length - 100 meters between the node and
hub (100 meters per segment)
- no more than 1024 nodes per hub
Topology - physica
lstar,
logica
lbus
Cable type - UTP
- one of the most popular networking
cabling schemes
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100BASE-TX
Speeds - 100 Mbps
Cable type - UTP/STP
Length - 100 meters per segment
- Two pairs of category 5 UTP or
Type 1 STP
- Physically resembles 10BASE-T
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10 Base 2
Can be used I many of the same instances as 10BASE5, but it is much easier to
install and much less expensive. 10BASE2 uses RG-58 coaxial cable with BNC
connectors.
Cables in the 10BASE2 systems connect with BNC connectors. The network
interface card in a computer requires a T-connector where you can two cables to
adjacent computers. Any unused connection must have a 50-ohm terminator.
Speeds - 10 Mbps
signal
type - base band (single signa
lon the cab
le)
length - no longer than 185 meters
- no more than 30 nodes per segment ,
nodes must be spaced at least 0.5 Meters apart
Known as - thin Ethernet, thinnet, and sometimes
cheapernet
cable type - coax
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10BASE5
Speeds - 10 Mbpssignal type - base bandlength - 500 meters per segment
- no more than 100 nodes per segment- nodes must be placed at 2.5 meter intervals
(cable is marked every 2.5 Meters forease of installation)
Color - typically yellow in color but its not standard
know as - thick Ethernet or thicknetcable type - coax
- uses vampire taps to connect devices to cable
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100BASE-FX
Speeds - 100Mbps (Ethernet over fiber
optic implementation)
Connectors - SC or ST
Cable type - fiber optic
Length - 2000 meters
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Gigabit Ethernet
1000BASESX
Cable type - Multimode fiber optic
Speeds - 1000Mbps
Length - 260 meters
Connectors - SC fiber
1000BASETX
Cable type - Cat 5 UTP
Speeds - 1000Mbps
Length - 100 meters
Connectors - same as 10BASE-T (RJ-45)
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The IEEE 802.3 Logical Relationship to the ISO Reference Model
Figure below shows the IEEE 802.3 logical layers and their relationship to the OSI
reference model. As with all IEEE 802 protocols, the ISO data link layer is divided into
two IEEE 802 sublayers, the Media Access Control (MAC) sublayer and the MAC-
client sublayer. The IEEE 802.3 physical layer corresponds to the ISO physical layer.
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The MAC-client sublayer may be one of the following:
Logical Link Control (LLC), if the unit is a DTE. This sublayer provides the interface
between the Ethernet MAC and the upper layers in the protocol stack of the end station.The LLC sublayer is defined by IEEE 802.2 standards.
Bridge entity, if the unit is a DCE. Bridge entities provide LAN-to-LAN interfaces
between LANs that use the same protocol (for example, Ethernet to Ethernet) and also
between different protocols (for example, Ethernet to Token Ring). Bridge entities are
defined by IEEE 802.1 standards.
Because specifications for LLC and bridge entities are common for all IEEE 802 LAN
protocols, network compatibility becomes the primary responsibility of the particular
network protocol. Figure shows different compatibility requirements imposed by the
MAC and physical levels for basic data communication over an Ethernet link.
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The Basic Ethernet Frame FormatThe IEEE 802.3 standard defines a basic data frame format that is required for all MAC
implementations, plus several additional optional formats that are used to extend the
protocol's basic capability. The basic data frame format contains the seven fields shown
in Figure. Preamble (PRE)Consists of 7 bytes. The PRE is an alternating pattern of ones and
zeros that tells receiving stations that a frame is coming, and that provides a means to
synchronize the frame-reception portions of receiving physical layers with the incoming
bit stream.
Start-of-frame delimiter (SOF)Consists of 1 byte. The SOF is an alternating
pattern of ones and zeros, ending with two consecutive 1-bits indicating that the next bit
is the left-most bit in the left-most byte of the destination address.
Destination address (DA)Consists of 6 bytes. The DA field identifies which
station(s) should receive the frame. The left-most bit in the DA field indicates whether
the address is an individual address (indicated by a 0) or a group address (indicated by a
1). The second bit from the left indicates whether the DA is globally administered(indicated by a 0) or locally administered (indicated by a 1). The remaining 46 bits are a
uniquely assigned value that identifies a single station, a defined group of stations, or all
stations on the network.
Source addresses (SA)Consists of 6 bytes. The SA field identifies the sending
station. The SA is always an individual address and the left-most bit in the SA field is
always 0.
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Length/TypeConsists of 2 bytes. This field indicates either the number of MAC-
client data bytes that are contained in the data field of the frame, or the frame type ID if
the frame is assembled using an optional format. If the Length/Type field value is less
than or equal to 1500, the number of LLC bytes in the Data field is equal to the
Length/Type field value. If the Length/Type field value is greater than 1536, the frameis an optional type frame, and the Length/Type field value identifies the particular type
of frame being sent or received.
DataIs a sequence ofnbytes of any value, where n is less than or equal to 1500. If
the length of the Data field is less than 46, the Data field must be extended by adding a
filler (a pad) sufficient to bring the Data field length to 46 bytes.
Frame check sequence (FCS)Consists of 4 bytes. This sequence contains a 32-bitcyclic redundancy check (CRC) value, which is created by the sending MAC and is
recalculated by the receiving MAC to check for damaged frames. The FCS is generated
over the DA, SA, Length/Type, and Data fields.
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Frame TransmissionWhenever an end station MAC receives a transmit-frame request with the
accompanying address and data information from the LLC sublayer, the MAC begins
the transmission sequence by transferring the LLC information into the MAC frame
buffer.
The preamble and start-of-frame delimiter are inserted in the PRE and SOF fields.
The destination and source addresses are inserted into the address fields.
The LLC data bytes are counted, and the number of bytes is inserted into the
Length/Type field. The LLC data bytes are inserted into the Data field. If the number of LLC data bytes is
less than 46, a pad is added to bring the Data field length up to 46.
An FCS value is generated over the DA, SA, Length/Type, and Data fields and is
appended to the end of the Data field.
After the frame is assembled, actual frame transmission will depend on whether the
MAC is operating in half-duplex or full-duplex mode.The IEEE 802.3 standard currently requires that all Ethernet MACs support half-duplex
operation, in which the MAC can be either transmitting or receiving a frame, but it
cannot be doing both simultaneously. Full-duplex operation is an optional MAC
capability that allows the MAC to transmit and receive frames simultaneously.
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Half-Duplex TransmissionThe CSMA/CDAccess Method
The CSMA/CD access rules are summarized by the
protocol's acronym:Carrier senseEach station continuously listens for
traffic on the medium to determine when
gaps between frame transmissions occur.
Multiple accessStations may begin transmitting any
time they detect that the network is quiet
(there is no traffic).Collision detectIf two or more stations in the same
CSMA/CD network (collision domain)
begin transmitting at approximately the
same time, the bit streams from the
transmitting stations will interfere
(collide) with each other, and both
transmissions will be unreadable. If
that happens, each transmitting station
must be capable of detecting that a
collision has occurred before it
has finished sending its frame.
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FullDuplex Operation
Full-duplex operation is an optional MAC capability that allows simultaneous
two-way transmission over point-to-point links. Full duplex transmission is
functionally much simpler than half-duplex transmission because it involves no
media contention, no collisions, no need to schedule retransmissions, and no need
for extension bits on the end of short frames. The result is not only more time
available for transmission, but also an effective doubling of the link bandwidth
because each link can now support full-rate, simultaneous, two-way
transmission.Transmission can usually begin as soon as frames are ready to send. The only
restriction is that there must be a minimum-length inter-frame gap between
successive frames, as shown in Figure, and each frame must conform to Ethernet
frame format standards
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10-Mbps Ethernet10Base-T
10Base-T provides Manchester-encoded 10-Mbps bit-serial communication over two
unshielded twisted-pair cables. Although the standard was designed to supporttransmission over common telephone cable, the more typical link configuration is to use
two pair of a four-pair Category 3 or 5 cable, terminated at each NIC with an 8-pin RJ-
45 connector (the MDI). Figure below is he 10Base-T Link A Four-Pair UTP cable in
which Two Pairs are not used.
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100 MbpsFast EthernetIncreasing the Ethernet transmission rate by a factor of ten over 10Base-T was not a
simple task, and the effort resulted in the development of three separate physical layer
standards for 100 Mbps over UTP cable: 100Base-TX and 100Base-T4 in 1995, and100Base-T2 in 1997. Each was defined with different encoding requirements and a
different set of media-dependent sublayers, even though there is some overlap in the
link cabling. Table compares the physical layer characteristics of 10Base-T to the
various 100Base versions.
Ethernet
Version
Transmit
Symbol Rate1Encodi
ngCabling
Full-Duplex
Operation
10Base-T 10 MBps Manch
ester
Two pairs of UTP Category -3
or better
Supported
100Base-
TX
125 MBps 4B/5B Two pairs of UTP Category -5
or Type 1 ST
P
Supported
100Base-
T4
33 MBps 8B/6T Four pairs of UTP Category -3
or better
Not supported
100Base-
T2
25 MBps PAM5x
5
Two pairs of UTP Category -3
or better
Supported
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The 100Base-T4 Frame Transmission Sequence
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1000 MbpsGigabit Ethernet
The Gigabit Ethernet standards development resulted in two primary specifications:
1000Base-T for UTP copper cable and 1000Base-X STP copper cable, as well as singleand multimode optical fiber (see Figure).
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1000Base-T
1000Base-T Ethernet provides full-duplex transmission over four-pair Category 5 or
better UTP cable. 1000Base-T is based largely on the findings and design approachesthat led to the development of the Fast Ethernet physical layer implementations:
100Base-TX proved that binary symbol streams could be successfully transmitted
over Category 5 UTP cable at 125 MBps.
100Base-T4 provided a basic understanding of the problems related to sending
multilevel signals over four wire pairs.
100Base-T2 proved that PAM5 encoding, coupled with digital signal processing,could handle both simultaneous two-way data streams and potential crosstalk problems
resulting from alien signals on adjacent wire pairs.
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1000Base-X
All three 1000Base-X versions support full-duplex binary transmission at 1250 Mbps
over two strands of optical fiber or two STP copper wire-pairs, as shown in Figure.Transmission coding is based on the ANSI Fibre Channel 8B/10B encoding scheme.
Each 8-bit data byte is mapped into a 10-bit code-group for bit-serial transmission. Like
earlier Ethernet versions, each data frame is encapsulated at the physical layer before
transmission, and link synchronization is maintained by sending a continuous stream of
IDLE code-groups during interframe gaps. All 1000Base-X physical layers support both
half-duplex and full-duplex
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Network Cabling Link Crossover Requirements
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CHAPTER 4
NETWORK CABLING
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What is NetworkCabling?
Cable is the medium through which information usually moves from one networkdevice to another. There are several types of cable which are commonly used with
LANs. In some cases, a network will utilize only one type of cable, other networks will
use a variety of cable types. The type of cable chosen for a network is related to the
network's topology, protocol, and size. Understanding the characteristics of different
types of cable and how they relate to other aspects of a network is necessary for the
development of a successful network.
The types of cables used in networks
Unshielded Twisted Pair (UTP) Cable
Shielded Twisted Pair (STP) Cable
Coaxial Cable
Fiber Optic Cable
Wireless LANs
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Unshielded twisted pair (UTP) is the most popular and is generally the best option for
school networks
The quality of UTP may vary from telephone-grade wire to extremely high-speed cable.
The cable has four pairs of wires inside the jacket. Each pair is twisted with a different
number of twists per inch to help eliminate interference from adjacent pairs and other
electrical devices. The tighter the twisting, the higher the supported transmission rate
and the greater the cost per foot. The EIA/TIA (Electronic Industry
Association/Telecommunication Industry Association) has established standards of UTP
and rated five categories of wire.
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Unshielded Twisted Pair Connector
The standard connector for unshielded twisted pair cabling is an RJ-45 connector. This
is a plastic co
nnecto
r that loo
ks like a large telepho
ne-style co
nnecto
r.A
slo
t allo
ws theRJ-45 to be inserted only one way. RJ stands for Registered Jack, implying that the
connector follows a standard borrowed from the telephone industry. This standard
designates which wire goes with each pin inside the connector.
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Shielded Twisted Pair (STP) Cable
A disadvantage of UTP is that it may be susceptible to radio and electrical frequency
interference. Shielded twisted pair (STP) is suitable for environments with electricalinterference; however, the extra shielding can make the cables quite bulky. Shielded
twisted pair is often used on networks using Token Ring topology.
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Coaxial Cable
Coaxial cabling has a single copper conductor at its center. A plastic layer provides insulation
between the center conductor and a braided metal shield The metal shield helps to block any
outside interference from fluorescent lights, motors, and other computers.
Although coaxial cabling is difficult to install, it is highly resistant to signal interference. In
addition, it can support greater cable lengths between network devices than twisted pair cable.The two types of coaxial cabling are thick coaxial and thin coaxial.
Thin coaxial cable is also referred to as thinnet. 10Base2 refers to the specifications for thin
coaxial cable carrying Ethernet signals. The 2 refers to the approximate maximum segment
length being 200 meters. In actual fact the maximum segment length is 185 meters. Thin coaxial
cable is popular in school networks, especially linear bus networks.
Thick coaxial cable is also referred to as thicknet. 10Base5 refers to the specifications for thick
coaxial cable carrying Ethernet signals. The 5 refers to the maximum segment length being 500meters. Thick coaxial cable has an extra protective plastic cover that helps keep moisture away
from the center conductor. This makes thick coaxial a great choice when running longer lengths
in a linear bus network. One disadvantage of thick coaxial is that it does not bend easily and is
difficult to install.
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CoaxialCable Connectors
The most common type of connector used with coaxial cables is theBayone-Neill-Concelman (BNC) connector. Different types of adapters
are available for BNC connectors, including a T-connector, barrel
connector, and terminator. Connectors on the cable are the weakest
points in any network. To help avoid problems with your network,
always use the BNC connectors that crimp, rather than screw, onto thecable.
FiberOptic Cable
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FiberOptic Cable
Fiber optic cabling consists of a center glass core surrounded by several layers of
protective materials. It transmits light rather than electronic signals eliminating the
problem of electrical interference. This makes it ideal for certain environments thatcontain a large amount of electrical interference. It has also made it the standard for
connecting networks between buildings, due to its immunity to the effects of moisture
and lighting.
Fiber optic cable has the ability to transmit signals over much longer distances than
coaxial and twisted pair. It also has the capability to carry information at vastly greater
speeds. This capacity broadens communication possibilities to include services such as
video conferencing and interactive services. The cost of fiber optic cabling is
comparable to copper cabling; however, it is more difficult to install and modify.
10BaseF refers to the specifications for fiber optic cable carrying Ethernet signals.
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FiberOptic Connector
The most common connector used with fiber optic cable is an ST connector. It is barrel
shaped, similar to a BNC connector. A newer connector, the SC, is becoming more
popular. It has a squared face and is easier to connect in a confined space.
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Ethernet Cable Summary
10BaseT Unshielded Twisted Pair 100 meters
10Base2 Thin Coaxial 185 meters
10Base5 Thick Coaxial l500 meters
10BaseF Fiber Optic 2000 meters
100BaseT Unshielded Twisted Pair 100 meters
100BaseTX Unshielded Twisted Pair 220 meters
Wireless LANs
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Wireless LANs
Not all networks are connected with cabling; some networks are wireless. WirelessLANs use high frequency radio signals, infrared light beams, or lasers to communicate
between the workstations and the file server or hubs. Each workstation and file server
on a wireless network has some sort of transceiver/antenna to send and receive the data.
Information is relayed between transceivers as if they were physically connected. For
longer distance, wireless communications can also take place through cellular telephone
technology, microwave transmission, or by satellite.
Wireless networks are great for allowing laptop computers or remote computers to
connect to the LAN. Wireless networks are also beneficial in older buildings where it
may be difficult or impossible to install cables.
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Installing Cable - Some Guidelines
When running cable, it is best to follow a few simple rules:
Always use more cable than you need. Leave plenty of slack.Test every part of a network as you install it. Even if it is brand new, it may have
problems that will be difficult to isolate later.
Stay at least 3 feet away from fluorescent light boxes and other sources of electrical
interference.
If it is necessary to run cable across the floor, cover the cable with cable protectors.
Label both ends of each cable.Use cable ties (not tape) to keep cables in the same location together.
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CHAPTER 5
NETWORKING BASICS
Hubs
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Hubs
The term hub is sometimes used to refer to any piece of network equipment that
connects PCs together, but it actually refers to a multi-port repeater. This type of device
simply passes on (repeats) all the information it receives, so that all devices connected
to its ports receive that information.
Hubs repeat everything they receive and can be used to extend the network. However,
this can result in a lot of unnecessary traffic being sent to all devices on the network.
Hubs pass on traffic to the network regardless of the intended destination; the PCs to
which the packets are sent use the address information in each packet to work out which
packets are meant for them. In a small network repeating is not a problem but for a
larger, more heavily used network, another piece of networking equipment (such as a
switch) may be required to help reduce the amount of unnecessary traffic being
generated.
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StandAloneHub
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StackableHub
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ModularHub
Hubs function on Layer 1, have a single collision domain, and do not segment network
traffic.
ROUTER
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ROUTER
A router is a computer networking device that forwards data packets toward their
destinations through a process known as routing. Routing occurs at layer 3 of the OSI
seven-layer model.
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Router Responsibilities
1. Optimizing the Routing Paths.
2. Switching
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Router Features
Use dynamic routingOperate at the protocollevel
Remote administration
Support complex networks
The more filtering done, the lower the performance
Provides security
Segment networks logically
Broadcast storms can be isolated
Often provide bridge functions also
More complex routing protocols used [such as RIP, IGRP,
OSPF]
Bridges
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g
A data-linkbridge is a device that connects two similar networks or divides one
network into two. It takes frames from one network and puts them on the other,
and vice versa.As it does this, it regenerates the signal strength of the frames,
allowing data to travel further. In this sense, a data-link bridge incorporates thefunctionality of a repeater, which also regenerates frames to extend a LAN. But a
bridge does more than a repeater.A bridge is more intelligent than a repeater. It
can look at each frame and decide on which of the two networks it belongs.
Repeaters simply forward every frame from one network to the other, without
looking at them.
A bridge looks at each frame as it passes, checking the source and destination
addresses. If a frame coming from Station 1 on LANA is destined for Station 5 on
LAN B, the bridge willpass the frame onto LAN B. If a frame coming from
Station 1 on LANA is destined for Station 3 on LAN A, the bridge will not forward
it; that is, it will filter it.
Bridges know which frames belong where by looking at the source and destination
addresses in the MediumAccess Control (MAC) layer information carried in the
frame. The MAClayer, which is part of the second layer ofOSI Model, defines
how frames get on the network without bumping into each other. It also contains
information about where the frame came from and where it should go. Because
bridges use this level of information, they have several advantages over other
forms of interconnecting LANs.
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Types of Bridges
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Bridges can be grouped into categories based on various product characteristics. Using
one popular classification scheme, bridges are either local or remote. Localbridges
provide a direct connection between multiple LAN segments in the same area.Remotebridges connect multiple LAN segments in different areas, usually over
telecommunications lines.
Figure Local and Remote Bridges Connect LAN Segments in SpecificAreas
AMAC-Layer Bridge Connects the IEEE 802.3
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and IEEE 802.5 Networks
Advantages of Bridges
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Increase the number of attached workstations and
network segments
Since bridges buffer frames, it is possible to interconnect
different segments which use different MACprotocols
Since bridges work at the MAClayer, they are
transparent to higher levelprotocols
By subdividing the LAN into smaller segments,
overall reliability is increased and the network becomes
easier to maintain
Used for non routable protocols like NetBEUI
which must be bridged
Advantages of Bridges
Disadvantages of Bridges
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The buffering of frames introduces network delays
Bridges may overload during periods of high traffic
Bridges combine different MACprotocols,require
the frames to be modified before transmission onto
the new segment. This causes delays
In complex networks, data may be sent over redundant
paths, and the shortest path is not always taken
Bridges pass on broadcasts, giving rise to broadcast
storms on the network
Disadvantages of Bridges
Bridge Features
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Operate at the MAClayer (layer 2 of the OSI model)
Can reduce traffic on other segments
Broadcasts are forwarded to every segment
Most allow remote access and configuration
Small delays introduced
Fault tolerant by isolating fault segments and
reconfiguring paths in the event of failure
Not efficient with complex networks
Redundant paths to other networks are not used (would
be useful if the major path being used was overloaded)
Shortest path is not always chosen by spanning tree
algorithm
Bridge Features
SWITCHES
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Switches are smart hubs that send data directly to the destination rather than
everywhere within a network. Switches also allow components of different
speeds to communicate.
Switches divide the network into smaller collision domains [a collision domain is a
group of workstations that contend for the same bandwidth]. Each segment
into the switch has its own collision domain (where the bandwidth is competed
for by workstations in that segment).As packets arrive at the switch, it looks at the
MAC address in the header, and decides which segment to forward the packet
to.Higher protocols like IPX and TCP/IP are buried deep inside the packet, so
are
invisible to the switch. Once the destination segment has been determined, the
packet is forwarded without delay.
Different forwarding techniques:-
1. Cut-through Switches
2. Store-Forward Switches
LAN Switch
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LAN switches are used to interconnect multiple LAN segments. LAN switching
provides dedicated, collision-free communication between network devices, with
support for multiple simultaneous conversations. LAN switches are designed to switchdata frames at high speeds. Figure 4-4 illustrates a simple network in which a LAN
switch interconnects a 10-Mbps and a 100-Mbps Ethernet LAN.
LAN Switch Can Link 10-Mbps and 100-Mbps Ethernet Segments
ATM Switch
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ATM Switch
Asynchronous Transfer Mode (ATM) switches provide high-speed switching and
scalable bandwidths in the workgroup, the enterprise network backbone, and the wide
area. ATM switches support voice, video, and data applications, and are designed to
switch fixed-size information units called cells, which are used in ATM
communications. Figure 4-3 illustrates an enterprise network comprised of multiple
LANs interconnected across an ATM backbone.
Multi-LAN Networks Can Use an ATM-Based Backbone When Switching Cells
Switch Benefits
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Switch Benefits
Isolates traffic, relieving congestion
Separates collision domains, reducing collisionsSegments, restarting distance and repeater rules
Switch Costs
Price: currently 3 to 5 times the price of a hubPacket processing time is longer than in a hub
Monitoring the network is more complicated
The two main impacts of switching will be faster
network connection to the server(s) and the isolation ofnon-relevant traffic from each segment.
Distinguishing between Bridges and Routers
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Both bridges and routers
Forward packets between networksSend data across WAN links
ABridge
Recognizes the address of EACH computer on it's segment and forwards packets onthe basis of the destination address
ARouter
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Works at the NETWORK layer and thus takes more information into account when
determining what to forward and where to forward it to.
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A router can connect networks that use
Different architectures
Different media access control methods
-- for example, they can connect an Ethernet segment
to a Token-Ring segment
MODEM
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The word "modem" stands for "modulator-demodulator".
A modem's purpose is to convert digital information to analog signals (modulation),
and to convert analog signals back into useful digital information (demodulation).
Wireless network means that each computer can communicate directly with every
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Wireless network means that each computer can communicate directly with every
other computer on the network. But some wireless networks are client/server.
They have an access point, which is a wired controller that receives and transmits
data to the wireless adapters installed in each computer.A gateway is a network point that acts as an entrance to another network.
In the network for an enterprise, a computer server acting as a gateway
node is often also acting as a proxy server and a firewall server
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A channel service unit/digital service unit (CSU/DSU) is a digital-interface
device used to connect a router to a digital circuit like a T1.
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RJ-45 CONNECTOR
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AUI
B t N il C l B iti h N l C t
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Bayonet Neil-Concelman or British NavelConnector
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SC
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SC
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CHAPTER 6
IEEE STANDARS
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IEEE STANDARDS
Fast Ethernet specification (IEEE 802.3u) is known as
100BASE-T. This new LAN standard has raised the
Ethernet speed limit from 10 Megabits per second to
100 Megabits per second with only minimal changes
to the existing cable structure
The Fast Ethernet specification calls for three types of transmission schemes
The first is 100BASE-TX
The second variation is 100Base-FX
The third variation is 100BASE-T4.
Types of Repeaters
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Class I Repeater: The Class 1 repeater operates by
translating line signals on the incoming port to adigital signal.
Class II Repeater: The Class II repeater immediately
repeats the signal on an incoming port to all the ports
on the repeater.
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The Fiber Distributed Data Interface (FDDI) specifies a 100-Mbps token passing dual-
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The Fiber Distributed Data Interface (FDDI) specifies a 100-Mbps token passing, dual-
ring LAN using fiber-optic cable. FDDI is frequently used as high-speed
backbone technology because of its support for high bandwidth and greater distances
than copper.
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FDDI Transmission Media
FDDI defines two types of optical fiber: single-modeand multimode. A mode is a ray of light that enters thefiber at a particular angle.Multimode fiber uses LED asthe light-generating device, while single-mode fibergenerally uses lasers.
Light Sources Differ for Single-Mode and Multimode Fibers
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Light Sources Differ for Single Mode and Multimode Fibers
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FDDI's four specifications are
Media Access Control (MAC)
Physical Layer Protocol (PHY),
Physical-Medium Dependent (PMD)
Station Management (SMT)
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FDDI Station-Attachment Types
FDDI defines four types of devices:
Single-Attachment Station (SAS)
Dual-Attachment Station (DAS)
Single-Attached Concentrator (SAC)Dual-Attached Concentrator (DAC).
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FDDI DAS PortsAttach to the Primary and Secondary Rings
AConcentratorAttaches to Both the Primary and
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y
Secondary Rings
A Ring Recovers from a Station Failure by Wrapping
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ARing also Wraps to Withstand a Cable Failure
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ADual-Homed Configuration Guarantees Operation
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The FDDI Frame Is Similar to That of a Token Ring Frame
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802.11b wireless network adapter can operate in two modes,
Ad-Hoc and Infrastructure.
In infrastructure mode, all your traffic passes through a
wireless access point.
InAd-hoc mode your computers talk directly to each other
and do not need an access point at all.
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Access point varieties
Access points come in three varieties
Bridge
NAT router
NAT router+bridge.
A bridge type connects a wireless network to a wired
network transparently. Communication is possible
between both networks in both directions
A NAT router type routes traffic from your wireless
network to an Ethernet wired network, but it will notroute traffic back. This type can be used to share
an Internet connection
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Hybrid NAT router + Bridge devices that bridge your
wired and wireless networks, then route them both to theinternet using a single IP address. This is good for sharing
an Internet connection when you have both wired and
wireless computers in your home. These are often
called Cable/DSL routers with wireless.
Bridging a wireless 802.11b network with a
i d Eth t t k
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wired Ethernet network.
Wireless access point (802.11b) of the router variety
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Cable/DSL Router with Wireless Ethernet
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IEEE 802.2 LLC - Logical LinkControl Layer
SAPs are Service Access Ports. A SAP is a port(l i l li k) t th N t k l t l If
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(logical link) to the Network layer protocol. If we wereoperating a multi protocol LAN, each Network Layer
protocol would have its own SAP.
Types of LLC Operation
Type 1: ConnectionlessType 2: Connection Oriented
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Type 1: Connectionless
Connectionless service for data communications is verysimilar to sending mail through the postal system(hand delivered mail): the data is sent and we hope itarrives at its destination.
Connection Oriented
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Connection Oriented
Connection Oriented service for data communications isvery similar to having a phone conversation
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Connection-Oriented operation for the LLC
layer provides these 4 services:
Connection establishment
Confirmation and acknowledgement that data has
been received.
Error recovery by requesting received bad data to
be resent.
Sliding Windows
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CHAPTER 7
MAC ADDRESS
MACAddress
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MAC addresses are also known as hardware addresses or physical addresses. They
uniquely identify an adapter on a LAN.
Short for Media Access Control address. This is OSI layer 2 hardware address defined
by IEEE standard and is used to deliver packets in the local network. It is sequence of
six two-digits hexadecimal numbers separated by colons, exempli gratia:
00:2f:21:c1:11:0a
MM:MM:MM:SS:SS:SSMM-MM-MM-SS-SS-SS
The first half of a MAC address contains the ID number of the adapter manufacturer.
These IDs are regulated by an Internet standards body. The second half of a MAC
address represents the serial number assigned to the adapter by the manufacturer
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IP networks maintain a mapping between the IP address of a device and its MAC
address This mapping is known as the ARP cache or ARP table
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address. This mapping is known as the ARP cache or ARP table
How to find your MAC address in Windows XP
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CHAPTER 8
IP ADDRESS
IPAddressing
IPAddress Requirements
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IPAddress Requirements
What is an IPAddress?
Network IDs and Host IDsIPAddressing Rules
Classfull IPAddressing
Address Classes
ClassAAddresses
Class BAddresses
Class CAddressesClass D & EAddresses
Address Class Summary
IP Addressing Requirements
Each Device that uses TCP/IP needs at least one!
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Computer/Host (each Network Interface Card)
Routers (each port or connection)
Other Devices
Each Device needs a Unique IP Address
An Example:
206.77.105.9Configured in TCP/IP Software
What is an IP Address?
32-bit Binary Number (Address)
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11000000101010000111000100010011
Divided into 4, 8-bit Octets
11000000.10101000.01110001.00010011
Converted to Decimal Numbers
See: Binary Math
192.168.113.19
Decimal range of an Octet: 0-255
It contains the devices:
Network ID and Host ID
Network ID and Host ID
Network ID
Sh d C t ll t th h i l t
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Shared or Common to all computers on the same physical segment
Unique on the Entire Network
Area Code
Host ID
Identifies a specific device (Host) within a physical segment
Unique on the physical segment
Phone Number
192.176.11.201
IP Addressing Rules
Each Device (Host) Needs at Least One Unique IP Address
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All Devices on the Same Physical Segment Share a Common Network ID (Subnet
Mask)
Each Physical Segment Has a Unique Network ID (Subnet Mask)
Classfull IP Addressing
Traditional Manner of Addressing
Class A
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Class A
Class B
Class C
Address Classes Specify Which Octets of the IP Address are the Network-ID and
Which are the Host-ID
Address Classes Specify Network Sizes (Number of Hosts)
Address Classes
ClassA
Network . Host . Host . Host
Class B
Network . Network . Host . Host
Class CNetwork . Network . Network . Host
Class D & E
Class A Networks:
The Definition
Per Specification:
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Per Specification:
1st Octet is the Network ID
2nd, 3rd, 4th Octets are the Host ID
In Binary
Any address that starts with a 0 in the first bit!
First Class A Network Address:
00000001.00000000.0000000.00000000 (Binary)
1.0.0.0 (Decimal)
Last Class A Network Address:
01111111.00000000.00000000.00000000 (Binary)
127.0.0.0 (Decimal) (Loopback Address)
Class A Networks:
Network IDs
1 t O t t i th N t k ID
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1st Octet is the Network ID
0.0.0.0 (Invalid)
1.0.0.0
2.0.0.0
3.0.0.0
~~~~
127.0.0.0 (Loop back)
2nd, 3rd, 4th Octets are the Host IDs
An Assigned Class A Network Address:
33.0.0.0 (Specifies the Network)
2nd, 3rd, 4th Octets are the Host IDs
Specified by Network Administrators
Class A Networks:
The Number of Networks
1st Octet is the Network ID
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1st Octet is the Network ID
1-126 = 126 Possible Class A Network IDs
2nd, 3rd, 4th Octets are the Host IDs
Each of the three Octets has a possible 256 Host IDs
Number of Host IDs from three Octets:
256 * 256 * 256 = 16,777,216 (minus 2) = 16,777,214
Always Subtract 2 from the number of Host IDs
Host IDs cannot be all 1s (reserved for broadcast address)
Host IDs cannot be all 0s (reserved for this network only address)
Class A Networks:
Host ID Addresses
33 0 0 0 (A A i d Cl AAdd )
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33.0.0.0 (An Assigned Class A Address)
All devices would share the 33 network ID.The Administrator would number the IP devices:
33.0.0.1 33.0.0.255 (255 Addresses)
33.0.1.0 33.0.1.255 (256 Addresses)
~~~~
33.0.255.0 -- 33.0.255.255 (256 Addresses)
(A Total of 65,535 Addresses)33.1.0.0 -- 33.1.255.255 (65,536 Addresses)
33.2.0.0 -- 33.2.255.255 (65,536 Addresses)
~~~~
33.255.0.0 -- 33.255.255.254 (65,535 Addresses)
( Total Addresses: 16.7 Million)
Class B Networks:
The Definition Per Specification:
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1st and 2nd Octets are the Network ID
3rd, 4th Octets are the Host IDs
In Binary
Any address that starts with a 10 in the first two bits of the first octet!
First Class B Network Address:
10000000.00000000.0000000.00000000 (Binary)
128.0.0.0 (Decimal)
Last Class B Network Address:
10111111.11111111.00000000.00000000 (Binary)
191.255.0.0 (Decimal)
Class B Networks:
Network IDs
1st and 2nd Octets are the Network IDs
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1st and 2nd Octets are the Network IDs
128.0.0.0
128.1.0.0
~~~~
128.255.0.0
129.0.0.0
129.1.0.0
~~~~
191.255.0.0
3rd, 4th Octets are the Host IDs
An Assigned Class B Network Addresses 153.11.0.0
3rd, 4th Octets are the Host IDs
Specified by Network Administrators
Class B Networks:
The Number of Networks
1st and 2nd Octets are the Network IDs
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1st and 2nd Octets are the Network IDs
1st Octet 128 -- 191 = 64 Possible Network IDs
2nd Octet 0 255 = 256 Possible Network IDs
Total Class B Network IDs 64 * 256 = 16,384
3rd, 4th Octets are the Host IDs
Each of the Two Octets has a possible 256 Host IDs
Number of Host IDs from Two Octets:256 * 256 = 65,536 (minus 2) = 65,534
Always Subtract 2 from the number of Host IDs
Host ID cannot be all 1s (reserved for broadcast address)
Host ID cannot be all 0s (reserved for this network only address)
Class B Networks:
Host ID Addresses
An Assigned Class B Address 153 11 0 0
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An Assigned Class B Address 153.11.0.0
All devices would share the 153.11 Network ID.
The Administrator would number the IP devices:153.11.0.1 -- 153.11.0.255 (255 Addresses)
153.11.1.0 -- 153.11.1.255 (256 Addresses)
153.11.2.0 -- 153.11.2.255 (256 Addresses)
~~~~
153.11.255.0 -- 153.11.255.254 (255 Addresses)
Total Addresses: 65,534
Class C Networks:
The DefinitionPer Specification:
1st 2nd 3rd Octets are the Network ID
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1st, 2nd, 3rd Octets are the Network ID
4th Octet is the Host ID
In Binary
Any address that starts with a 110 in the first three bits of the first octet!
First Class C Network Address:
11000000.00000000.0000000.00000000 (Binary)
192.0.0.0 (Decimal)
Last Class C Network Address:
11011111.11111111.11111111.00000000 (Binary)
223.255.255.0 (Decimal)
Class C Networks:
Network IDs
1st 2nd 3rd Octets are the Network IDs
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1st, 2nd, 3rd Octets are the Network IDs
192.0.0.0 192.0.255. 0
192.1.0.0 192.1.255.0
~~~~
192.255.0.0 192.255.255.0
193.0.0.0 193.255.255.0
~~~~
223.0.0.0 223.255.255.04th Octet is the Host IDs
An Assigned Class C Network Address
201.11.206.0
4th Octet is the Host IDsSpecified by Network Administrators
Class C Networks:
The Number of Networks
1st 2nd 3rd Octets are the Network IDs
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1st, 2nd, 3rd Octets are the Network IDs
1st Octet 192 -- 223 = 31 Possible IDs
2nd Octet 0 255 = 256 Possible IDs
3nd Octet 0 255 = 256 Possible IDs
Total Class C Network IDs 32 * 256 *256 = 2,097,152
4th Octet is the Host ID
An Octet has a possible 256 IDs
Number of Host IDs an Octet:
256 (minus 2) = 254
Always Subtract 2 from the number of Host IDs
Host ID cannot be all 1s (reserved for broadcast address)
Host ID cannot be all 0s (reserved for this network only address)
Class C Networks:
Host ID Addresses
An Assigned Class C Address
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An Assigned Class C Address
201.11.206.0
All devices would share the 201.11.206.0 Network ID.
The Administrator would number the IP devices:
201.11.206.1, 201.11.206.2, ~~~~ 201.11.206.254
Class D & E
Class D
Used by Multicast Applications
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Used by Multicast Applications
Shared Addresses
224.0.0.0 239.255.255.255
Class EExperimental
240.0.0.0 +
Address Classes:
Network IDs and Host IDs
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Class A (1st Octet 1-127)
Network.Host.Host.Host
Class B (1st Octet 128-191)
Network.Network.Host.Host
Class C (1st Octet 192-223)
Network.Network.Network.Host
Address Class Summary
1st Networks Hosts IDs
Octet IDs /Network
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Class A 1-127 126 16,777,214
Class B 128-191 16,384 65,534
Class C 192-223 2,097,152 254
Subnetting and Creating Custom Subnet Masks
Introduction: Why Custom Subnet Masks? What are Subnet IDs?
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Step 1 Design the Physical Network
Step 2 Choose a Custom Subnet Mask
Step 3 Determining the Subnet IDs
Step 4 Determining the Host IDs
Quick Review:
What is a Subnet Mask?
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An Address the accompanies an IP address that indicates which portion of the IP
address is the Network ID and which portion of the IP address is the Host ID.
152.107.102.7 (IP Address)
255.255.255.0 (Subnet Mask)
The IP Address and Subnet Mask (SNM) are interrelated and each only has meaning in
the context of the other!
IP Address and SNM are the minimum IP addressing requirements.
What Makes up a Subnet Mask (SNM)?
In Binary:
1s represent what portion of the IP address is the Network ID
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p p
0s represent what portion of the IP address is the Host ID
ForExample:
207.23.106.99 (Class CAddress)
Net . Net . Net . Host
11111111 . 11111111 . 11111111 . 00000000 (SNM in Binary)
255.255.255.0 (SNM in Decimal)
Default Subnet Masks (SNM)
ClassA (Net.Host.Host.Host)
11111111.00000000.00000000.00000000
255.0.0.0
Class B (Net.Net.Host.Host)
11111111.11111111.00000000.00000000255.255.0.0
Class C (Net.Net.Net.Host)
11111111.11111111.11111111.00000000
255.255.255.0
Why Custom Subnet Masks?
Default Subnet Masks
Class A (1 Network 16.7M Hosts)
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Class A (1 Network 16.7M Hosts)
Class B (1 Network 65K Hosts)
Class C (1 Network 254 Hosts)
Addressing an IP Network
Assigned an IP Network Address 152.77.0.0 (IP Address)
255.255.0.0 (Subnet Mask)
All Devices/Hosts on the Same Physical Segment Must have the Same Network ID
One Network ID Supports Only One Physical Segment!
What are Subnets?
A Subnet is a portion or subdivision of the IP Addresses that are associated with an
assigned Network ID.The Range of IP Addresses included in a subnet is determined by
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g g y
the Subnet Mask. Subnets must be meticulously numbered for network communication
to be successful.
Custom Subnetting:
The Steps
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Design Physical Network
Determine the Number of Physical Segments
Determine the Maximum Number of Hosts per Physical Segment
Choose a Subnet Mask that creates the number of:
Subnet-IDs >= Physical Segments
Host-IDs/Subnet-ID >= Hosts/Physical Segment
Determine and Number Subnet IDs (SN ID)
Determine and Number Host IDs
Subnet IDs
Portions of the Assigned Network ID are Defined by Subnet IDs 152.77.0.0
(Network IP Address) 255.255.0.0 (Default Subnet Mask)
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Network . Network . Host . Host (Default SNM)Network . Network . SN-ID . Host (Custom SNM)
All Device/Hosts Share the Assigned Network ID (All Physical Segments)
Each Physical Segment of the Network has a Unique Subnet-ID and the Subnet ID is
Common to All Hosts on a Physical Segment
Each Host on the Network has a Host ID Unique to its Subnet ID
Domain Naming System
DNS as a Service
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Domain Name Structure
DNS Software
Configuring DNS
How DNS Works
DNS as a Service
IP Address needed by programs
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y p g
100.109.23.144
The DNS Service Provides IP Name Resolution
DNS is a distributed database of Domain Names and their corresponding IP Addresses
Domain Naming System
A hierarchical naming system used to give each server on the Internet a unique name.
www.learntosubnet.com (URL or FQDN)
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( Q )
HostName.Domain.TLD HostName and the Domain Name = Fully Qualified Domain
Name (FQDN)
DNS keeps a complete listing of all FQDNs and their associated IP address
Domain Name Structure (Organizational Structure)
R t
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Root
NET COM GOV Org, us, ca, etc
IIHT COMPAQ SEC
DNS Software
Resolver
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Built into Client TCP/IP Software
Ask Designated Name Server for IP Address When Client Enters FQDN (URL)
Name Server
DNS Server (Available with Most OSs)
Retrieves IP Addresses for Clients
Supplies IP Address to other Name Servers
Provided by the Internet, ISP, or business
How DNS Works (The Two Key Functions)
Root Level DNS Server
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CLIENT
FQDN IP Address
TLD (com DNS Server)
SEC DNS Server
IP address
www.iiht.com
PROBLEMS
Scenario 1
Required Number of Physical Segments: 5
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Required Number of Physical Segments: 5
Maximum Number of Hosts/Physical Segment: 5000Network Address:152.77.0.0
Scenario 2
Required Number of Physical Segments: 100
Maximum Number of Hosts/Physical Segment: 350
Network Address: 177.133.0.0
Scenario 3
Required Number of Physical Segments: 100
Maximum Number of Hosts/Physical Segment: 88,000
Network Address:39.0.0.0
PROBLEMS
Scenario 4
Required Number of Physical Segments: 4
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Required Number of Physical Segments: 4
Maximum Number of Hosts/Physical Segment: 1,500,000Network Address: 120.0.0.0
Scenario 5
Required Number of Physical Segments: 12
Maximum Number of Hosts/Physical Segment: 12
Network Address: 216.122.44.0
Scenario 6
Required Number of Physical Segments: 50
Maximum Number of Hosts/Physical Segment: 600
Network Address: 134.119.0.0
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CHAPTER 9
COMMUNICATION PROTOCOLS
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Internet Protocol Suite
The Internet Protocol suite, usually referred to as "TCP/IP," is a full set of
internetworking protocols that operate in the network layer, the transport layer, and the
application layer. While TCP/IP refers to two separate protocols called TCP and IP,
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pp y p p ,
Internet Protocol suite refers to the entire set of protocols developed by the Internetcommunity. Still, most people just say "TCP/IP" when they are referring to the Internet
Protocol suite.
The global Internet is a success because of TCP/IP. It is hard to believe that there ever
was a "protocol war," but during the 1980s and early 1990s, many organizations wereindecisive about which protocols to use. TCP/IP was popular in academic, military, and
scientific communities, but many businesses had installed LANs using Novell SPX/IPX
and Microsoft's NetBEUI/NetBIOS, or were tied to legacy protocols such as IBM SNA.
The Internet protocols have been universally accepted because they support scalable
internetworking, for which the global Internet is the best example.
LAYERS IN THE TCP/IP SUITE
APPLICATION LAYER
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TRANSPORT LAYER
INTERNETWORK LAYER
NETWORK ACCESS LAYER
Network Access Layer
The design of TCP/IP hides the function of this layer from usersit is concerned with
getting data across a specific type of physical network (such as Ethernet, Token Ring,
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g g p yp p y ( g
etc.). This design reduces the need to rewrite higher levels of a TCP/IP stack when newphysical network technologies are introduced (such as ATM and Frame Relay).
The functions performed at this level include encapsulating the IP datagrams into
frames that are transmitted by the network. It also maps the IP addresses to the physical
addresses used by the network. One of the strengths of TCP/IP is its addressing scheme,
which uniquely identifies every computer on the network. This IP address must be
converted into whatever address is appropriate for the physical network over which thedatagram is transmitted.
Data to be transmitted is received from the internetwork layer. The network access layer
is responsible for routing and must add its routing information to the data. The network
access layer information is added in the form of a header, which is appended to the
beginning of the data.
Internetwork Layer
The best known TCP/IP protocol at the internetwork layer is the Internet Protocol (IP),
which provides the basic packet delivery service for all TCP/IP networks. In addition to
the physical node addresses used at the network access layer the IP protocol
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the physical node addresses used at the network access layer, the IP protocol
implements a system of logical host addresses called IP addresses. The IP addresses areused by the internetwork and higher layers to identify devices and to perform
internetwork routing. The Address Resolution Protocol (ARP) enables IP to identify the
physical address that matches a given IP address.
IP is used by all protocols in the layers above and below it to deliver data, which means
all TCP/IP data flows through IP when it is sent and received, regardless of its final
destination.
Host-to-Host Transport Layer
The protocol layer just above the internetwork layer is the host-to-host layer. It is
responsible for end-to-end data integrity. The two most important protocols employed at
this layer are the Transmission Control Protocol (TCP) and User Datagram Protocol
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this layer are the Transmission Control Protocol (TCP) and User Datagram Protocol
(UDP).TCP provides reliable, full-duplex connections and reliable service by ensuring that data
is resubmitted when transmission results in an error (end-to-end error detection and
correction). Also, TCP enables hosts to maintain multiple, simultaneous connections.
When error correction is not required, UDP provides unreliable datagram service
(connectionless) that enhances network throughput at the host-to-host transport layer.
Both protocols deliver data between the application layer and the internetwork layer.Applications programmers can choose the service that is most appropriate for their
specific applications.
Application Layer
The most widely known and implemented TCP/IP application layer protocols are listed
below:
File Transfer Protocol (FTP)
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File Transfer Protocol (FTP).
Telnet.Simple Mail Transfer Protocol (SMTP).
HyperText Transfer Protocol (HTTP).
Domain Name Service (DNS).
Routing Information Protocol (RIP).
Simple Network Management Protocol (SNMP).
Network File System (NFS).
HTTP
Protocol used by web browsers to request information from web servers
A Web Browser sends an HTTP Get packet to request a web page or other data
A Web Server sends the web page to the client in a HTTP Response packet.
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The HTTP Post packet allows end-users to send data to web servers (data entryforms)
Can transfer any type of data (resources)
HTML (Web pages)
Files (data, graphics, multimedia,etc.)
Packet format includes data like:
Request Method Get, Post, etc.
Location URL of Web site being accessed
Referrer URL of of last client access
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Referrer URL of of last client access
User-Agent Version information about the accessing web browser Data
Data-link header IP header TCP header HTTP Data link CRC
Hyper Text Markup Language (HTML)
A page description (formatting) language used to create Web sites
Uses tags and attributes to define the layout of a web page
Specify fonts, font sizes and colors of text
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