Transcript Meyers_CompTIA_4e_PPT_Ch02x

Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Network Models
Chapter 2
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Objectives
• Describe how models such as the OSI sevenlayer model and the TCP/IP model help
technicians understand and troubleshoot
networks
• Explain the major functions of network
hardware with the OSI seven-layer model
• Describe the major functions of networks with
the TCP/IP model
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Overview
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
The CompTIA Network+ Challenge
• Understand every aspect of networking
• Methods of conceptualizing the parts of the
network
– The Open Systems Interconnect (OSI) model
– The Transmission Control Protocol/Internet
Protocol (TCP/IP) model
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Two Network Models
• The OSI seven-layer and TCP/IP models
provide:
– A powerful tool for diagnosing
problems
– A common language to describe
networks
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 2.1 Using the OSI terminology—Layer 3—in
typical configuration documentation
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Historical/Conceptual
Working with Models
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Biography of a Model
• What does “model” mean to you?
– Computer models that predict weather
– Plastic model airplane
– Fashion model
• All models are a simplified representation of
the real thing
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 2.2 Types of models (images from left to right
courtesy of NOAA, Mike Schinkel, and Michael Smyer)
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
A Model: An Example
• A model has all the major functions of the real
item
Figure 2.3 Simple model airplane
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Network Models
• What functions define all networks?
• What details can be omitted?
• ISO (International Organization for
Standardization) proposed the OSI seven-layer
model
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
The OSI Seven-Layer
Model in Action
Layer 7 - Application
Layer 6 - Presentation
Layer 5 - Session
Layer 4 - Transport
Layer 3 - Network
Layer 2 - Data Link
Layer 1 - Physical
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Welcome to MHTechEd!
• A conceptual viewpoint of networking
– One of the workers has just completed a new
employee handbook
– She needs to transfer the Word document to the
other worker for review
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
She Could…
• Copy the file to a flash drive and walk it
over to the other person (Sneakernet)
• Transfer the file using the network
Figure 2.4 Janelle and Dana, hard at work
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Test Specific
Let’s Get Physical—Network
Hardware and Layers 1–2
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Cabling
• Most networks use unshielded twisted pair
(UTP) cable as a physical channel to move the
bits of data between systems
Figure 2.5 UTP cabling
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Central Box
• Each computer system has a cable leading to a
central box
– The central box sends the data received from one
system to all the other systems attached to it
Figure 2.6 Typical central box
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 2.7 The network so far, with the Physical
layer hardware installed
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Network Interface Cards (NICs)
• NICs are installed in PCs
– Network cables attach to the NICs
Figure 2.8 Typical NIC
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
NIC to Central Box Connections
• Cables run from the NIC in the PC to a jack on
the wall
– Inside the wall another cable runs all the way back
to the central box
Figure 2.9 NIC with cable connecting the PC to the wall jack
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 2.10 The MHTechEd network
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
The NIC
• Each system must have a unique identifier
• Media access control address or MAC address
– A unique address burned into a ROM chip on
the NIC
– Each MAC address is 12 hex characters or
48 bits in length
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
The MAC address is printed on
the surface of the chip and
burned into the ROM chip
Figure 2.11 MAC address
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
MAC Addresses
• MAC addresses are 48 bits long
– Usually represented using hexadecimal characters
(12 hex digits = 48 bits)
• A typical MAC address: 004005-607D49\
Organizationally Unique
Identifier (OUI)
Device ID
– No two MAC addresses are ever the same!
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
MAC address
Figure 2.12 Output from ipconfig /all
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 2.13 Data moving along a wire
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 2-14 Oscilloscope of data
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 2.15 Data as ones and zeroes
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 2-16 Inside the NIC
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Frames
• A frame is basically a container for a chunk of
data moving across a network
– Contains the recipient’s MAC address, the
sender’s MAC address, the data itself, and a frame
check sequence (FCS) for error checking
Figure 2.17 Generic frame
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 2.18 Frame as a canister
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Frame Size
• Different types of networks use different sizes
of frames
• Many frames hold at most 1500 bytes of data
• The sending software breaks up large amounts
of data into smaller chunks
• The receiving system’s software must
recombine the data chunks
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Into the Central Box
• When a system sends a frame out on the
network, the frame goes into the central box
• The technology of the central box determines
the next steps for the frame
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
The Central Box: Hubs
• In the early days, the central box was called a
hub
– The hub made copies of a frame and sent a copy
to every other system on the network
– Every frame sent on a network was received by
every NIC
– Only the NIC with the matching MAC address
would process that particular frame
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 2.19 Incoming frame!
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
The Central Box: Switches
• Switches replaced hubs
– A frame is sent only to the correct recipient MAC
address
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Getting the Data on the Line
• Since the cable is shared, only one
system may speak at a time
• Networks use frames to restrict the amount of
data a NIC can send at once
• NICs handle these and other issues on their
own without our help
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Getting to Know You
• Usually two devices have talked before, so the
destination MAC address is already known
• If the MAC address is not known, a broadcast
message is sent over the network
– The destination device will respond by sending its
MAC address
– The MAC broadcast address is FF-FF-FF-FF-FF-FF
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 2.20 Building the frame
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 2.21 Adding the data and FCS to the frame
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 2.22 Sending the frame
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 2.23 Reading an incoming frame
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
After the Frame is Received
• The receiving NIC uses the FCS to verify that
the data is valid
• If the data is valid, the receiving NIC strips off
all the framing information and sends the data
to the software—the operating system—for
processing
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 2.24 Layer 1 and Layer 2 are now properly applied to
the network
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
The Two Aspects of NICs
• Logical Link Control (LLC): the aspect of the
NIC that talks to the system’s operating system
(usually via device drivers)
– Handles multiple network protocols and provides
flow control
• Media Access Control (MAC): the role in which
frames are created and addressed
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 2.25 LLC and MAC, the two parts of the Data Link layer
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Beyond the Single Wire—
Network Software
and Layers 3–7
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
How Does Data Get from One System
to Another in Large Networks?
• A logical addressing method:
– Ignores the hardware
– Enables breaking a large network into subnets
• A network protocol creates:
– Unique identifiers for each system
– A set of communication rules for issues, e.g. how
to get packets from one subnet to another
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 2.26 Large LAN complete (left) and broken into
two subnets (right)
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
IP—Playing on Layer 3,
the Network Layer
• Packets are created and addressed
• The Internet Protocol is the primary logical
addressing protocol for TCP/IP
• A router connects each of the subnets
– The IP address is used to forward data
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 2.27 Typical small router
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 2.28 MHTechEd addressing
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 2.29 IP Packet
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 2.30 IP packet in a frame (as a canister)
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Packets Within Frames
• The packet is enclosed within a frame that
contains the sending and receiving MAC
addresses
Figure 2.31 IP packet in a frame
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
The Process of Sending Data
• Data sent from one computer to another on a
TCP/IP network can go through many routers
• Each router strips off the incoming frame and
creates a new frame needed for the
connection (e.g., cable or DSL network) to the
next router
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
The Process of Sending Data (cont’d.)
• Once the packet reaches the destination
subnet’s router, that router:
– Strips off the incoming frame
– Looks at the destination address
– Adds a frame with the appropriate MAC address
• The NIC strips off the MAC header and hands
the frame off to the network operating system
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 2.32 Router removing network frame
and adding one for outgoing connection
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Assembly and Disassembly—
Layer 4, the Transport Layer
• Most data is much larger than a single frame
• The transport protocol
– Breaks up the data into chunks called segments or
datagrams (depending on the specific transport
protocol used)
– Gives each segment some type of sequence
number
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Assembly and Disassembly—
Layer 4, the Transport Layer (cont’d.)
• The transport protocol breaks data into
segments and gives each segment a sequence
number
• The sequence numbers notify the receiving
system of the total number of segments and
how to put them together
– Similar to the numbering of boxes by UPS
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 2.33 Labeling the boxes
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
The Functions of the Transport Layer
• It is the assembler/disassembler software
• Also initializes requests for packets that were
not received in good order
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 2.34 OSI updated
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Talking on a Network—Layer 5,
the Session Layer
• One system may be talking to many other
systems simultaneously
• Session software handles processes of
connecting applications to applications
• Layer 5, the Session layer initiates sessions,
accepts incoming sessions, and opens and
closes existing sessions
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 2.35 Handling multiple inputs
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 2.36 Each request becomes a session
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 2.37 OSI updated
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Translation—Layer 6,
the Presentation Layer
• The Presentation layer translates data from
lower layers into a format usable by the
Application layer, and vice versa
– TCP/IP networks do not necessarily map directly
to the OSI model
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 2.38 OSI updated
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Network Applications—Layer 7,
the Application Layer
• Allow users to exchange data on a network
– Networks in Windows 7 or 8
– Web browsers: Google Chrome, Mozilla Firefox
– E-mail applications
• All operating systems have application
programming interfaces (APIs) at the
Application layer for network-aware
applications
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 2.39 Network applications at work
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 2.40 OSI updated
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Encapsulation and De-Encapsulation
• Encapsulation: the entire process of preparing
data to go onto a network
– All the steps from the application to the
Application, Presentation, Session, Transport,
Network, and Data Link layers
• De-encapsulation: the reverse process of
encapsulation
– Stripping all the extra header information out as
the data goes up the stack
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
The TCP/IP Model
• Four layers
– Application
– Transport
– Internet
– Link/Network Interface
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
The TCP/IP Model (cont’d.)
• TCP/IP does not have a standards body
– Results in a number of variations on the TCP/IP
model
• Version 1 (four layers) is used by Cisco,
Microsoft, and other major companies
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
The Link (Network Interface) Layer
• Corresponds to OSI model Layers 1 and 2
• Handles “physical” elements (cabling, hubs,
physical addresses, and NICs)
• Any part of the network that deals with
complete frames is in the Link layer
– Once the frame information is stripped away from
an IP packet, we move into the Internet layer
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 2.43 TCP/IP Link layer compared to OSI Layers 1 and 2
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
The Internet Layer
• The “IP packet” layer
• Deals with any device or application that uses
IP protocols and IP addressing and routing
• Routers function at this layer
• Maps to the Network layer (Layer 3) of the OSI
model
• IP packets are created in this layer
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 2.44 TCP/IP Internet layer compared to OSI Layer 3
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
The Transport Layer
• Maps to OSI Transport layer, Session layer,
and some of the Application layer
• Involved with assembly and disassembly
of data
• Provides both connection-oriented and
connectionless communications
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 2.45 TCP/IP Transport layer compared
to OSI Layers 4, 5, and part of 6
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Types of Communications Protocols
• Some protocols (e.g., Post Office Protocol or
POP) require good, established connections to
function
• A number of TCP/IP protocols (e.g., Voice over
IP) simply send data without first waiting to
verify that the receiving system is ready
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Connection-Oriented vs.
Connectionless Communications
• Connection-oriented protocol: Transmission
Control Protocol (TCP)
• Connectionless protocol: User Datagram
Protocol (UDP)
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Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 2.44 Connection between e-mail client and server
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 2.45 Connectionless communication
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Segments Within Packets
• TCP segments have fields that ensure the
connection-oriented communication works
properly
Figure 2.46 TCP segment
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
UDP Datagram
• Includes data from the Application layer with
added port and length numbers plus a
checksum
• A UDP datagram lacks most of the extra fields
found in TCP segments
– UDP does not care if the receiving computer gets
its data
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 2.47 UDP datagram
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
The Application Layer
• The TCP/IP Application layer maps to the top
three layers of the OSI model
– Uses a unique port numbering system that gives
each application a unique number between 1 and
65,535
– Allows Presentation layer formats, such as MIME
• Every TCP/IP application must be a part of a
network to function
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 2.48 TCP/IP Application layer compared to OSI Layers 5-7
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Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 2.49 OSI model and TCP/IP model side by side
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Frames, Packets, and Segments/
Datagrams, Oh My!
• Application layer: create the data
• Transport layer: breaks the data into chunks,
i.e., into TCP/UDP segments
• Internet layer: adds the IP addressing and
creates the IP packets
• Link layer: wraps the IP packet into a frame,
with the MAC address information and a
frame check sequence (FCS)
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Figure 2.50 Data encapsulation in TCP/IP
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Copyright © 2015 by McGraw-Hill Education. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Fourth Edition (Exam N10-006)
Tech Tip: The Tech’s
Troubleshooting Tools
• Example using OSI model: Jane cannot print to
the networked printer
– Layer 1 and 2: NIC shows activity?
– Layer 3: Does computer have a proper
IP address?
– Move up through the layers to discover problem
area
• The models are also communication tools
Copyright © 2015 by McGraw-Hill Education. All rights reserved.