Transcript Slide 1

Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Network Models
Chapter 2
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
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
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Overview
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
The CompTIA Network+ challenge
• Understand every aspect of networking
– Use the Open Systems Interconnect (OSI)
model
– Understand the TCP/IP model
– Conceptualize the parts of a network
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
• The OSI seven-layer model provides
– A powerful tool for diagnosing
problems
– A common language to describe
networks
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Figure 2.1 Using the OSI terminology – Layer 3 –
in a typical setup screen
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Working with models
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Biography of a model
• What does “model” mean to you?
– Computer models that predict weather
– Plastic model airplane
– Fashion model
Figure 2.2 Types of models
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
A model has all the major
functions of the real item
Figure 2.3 Simple model airplane
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
The OSI seven-layer model
• What functions define all networks?
• What details can be omitted?
• ISO (International Organization for
Standardization) proposed the OSI
seven-layer model
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Layer 7 - Application
The seven layers
in action
Layer 6 - Presentation
Layer 5 - Session
Layer 4 - Transport
The OSI model
Layer 3 - Network
Layer 2 - Data Link
Layer 1 - Physical
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
The TCP/IP model
• Another model that we will describe in
depth a bit later in the chapter
• Describes the actual de-facto protocol
of the Internet
• Maps to the OSI model very well
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
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
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Figure 2.4 Janelle and Dana,
hard at work
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
She could…
• Copy the file to a flash drive and walk it
over to the other person (Sneakernet)
• Transfer the file using the network
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Let’s get physical...
network hardware and
Layers 1 – 2
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Cabling
• Most networks use a cable,
like this one, as a physical
channel to move the bits of
data
unshielded twisted pair
(UTP) cable
Figure 2.5 UTP cabling
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Hubs
• Each computer system has
a cable leading to a device
called a hub
– Usually located in a closet
• The hub sends the data
received from one system
to all the other systems
attached to it
Figure 2.6 Typical hub
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Figure 2.7 The network so far, with the Physical layer
hardware
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Network Interface Cards
• Network Interface Cards
(NICs) are installed in
PCs
• Network cables attach
to the NICs
Figure 2.8 Typical NIC
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
NIC to hub connections
• Cables run from the
NIC in the PC to a jack
on the wall
• Cables run through the
walls to the closet
where they connect to
a hub
Figure 2.9 NIC with cable connecting the PC to the wall jack
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Network cabling system
Figure 2.10 The MHTechEd network
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
The NIC
• Each system must
have a unique
identifier
• Media Access Control
(MAC) address
MAC address printed on
surface of chip – and burned
inside the chip.
– A unique address burned
into a ROM chip on the
network card
– Each MAC address is 12
hex characters or 48 bits in
length
Figure 2.11 MAC address
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
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)
Note: This is an IEE
standard, called EUI-48!
Device ID
No two MAC addresses are ever the same!
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
ipconfig /all
MAC address
Figure 2.12 Output from ipconfig /all
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Moving data
Figure 2.13 Data moving along a wire
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Moving data (cont.)
Figure 2-14: Oscilloscope of data
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Moving data (cont.)
Figure 2.15 Data as ones and zeroes
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Frames
Figure 2-16 Inside the NIC
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Inside a frame
• Frames are made up of fields that contain
information
• Frames contain 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
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Frame as a canister
Figure 2.18 Frame as a canister
Note: 2nd MAC address is wrong
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Frame size
• Different networks use different sizes of
frames
• Many frames hold about 1500 bytes of data
• The sending software breaks up large
amounts of data into smaller chunks
• The receiving station must then put the
chunks back together in the proper order
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Processing frames
• All devices on the network see the frame,
but only the device that it is addressed to
will process it
– Every frame is received by every NIC
– The MAC address is used to decide if the frame
belongs to a given device
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Getting data on the line
• Since the cable is shared, only one
system may speak at a time
• Processes are used to keep two NICs
from talking at the same time
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Incoming frame!
Figure 2.19 Incoming frame!
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
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
– A MAC broadcast address is FF-FF-FF-FF-FF-FF
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Figure 2.20 Building the frame
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Figure 2.21 Adding the data and FCS to the frame
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Figure 2.22 Sending the frame
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Figure 2.23 Reading an incoming frame
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
After the frame is received
• The receiving station checks the FCS value in
the frame
– If the value matches what it should, then the NIC
sends the data portion to the network operating
system for processing
– If the value does not match, the frame has errors and
must be resent
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
The two aspects
of NICs
Figure 2.24 Layer 1 and Layer 2 are now properly
applied to the network
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Figure 2.25 LLC and MAC, the two parts of the Data Link layer
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Beyond the single wire –
network software
and Layers 3 – 7
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Subnets
Figure 2.26 Large LAN complete (left),
and broken into two subnets (right)
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
• Routers are used to
chop large networks up
into smaller ones
• Routers forward
packets by logical
address
• An IP router (most
common) forwards IP
packets
• Works at Layer 3, the
Network layer
Figure 2.27 Typical small router
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Figure 2.28 MHTechEd addressing
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Figure 2.29 IP Packet
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Figure 2.30 IP packet in a frame (as a canister)
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Frames (packets) within frames
• Network software creates a packet that
contains the sending and receiving IP
addresses along with the data
IP packet
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
• The packet is enclosed within a frame that
contains the sending and receiving MAC
addresses
Figure 2.31 IP packet in a frame
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Connecting to the Internet
• A router connects a local network to the Internet
• The local hub or switch is connected to the
router
• The router is connected to the Internet through a
cable or phone line
• The cable or phone line uses a different kind of
frame, so the router strips the frame and creates
a new one
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Connecting
to the Internet
Figure 2.32 Router removing network frame
and adding one for outgoing connection
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
• The router replaces the MAC address with the type
of address used by the cable or phone company
• The frame uses the IP address to guide it to the
receiving system
• The receiving router strips off the cable or phone
company frame and adds the MAC address for the
receiving system
• The NIC strips off the MAC header and hands the
frame off to the NOS
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Assembly and disassembly – Layer 4,
the Transport layer
• Most data is much larger than a single frame
• Network protocols chop up the data into smaller
packets, and give each one a sequence number
• The sequence numbers are used by the receiving system
to put the packets back in order, and to assemble them
• This compares to the numbering of boxes by UPS
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Figure 2.33 Labeling the boxes
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
• Transport layer is the assembler/disassembler
• Transport layer also initializes requests for packets
that weren’t received in good order
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Figure 2.34 OSI updated
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Talking on a network – Layer 5,
the Session layer
• One system may be talking to many other
systems simultaneously
• The software that handles these processes is
called session software, working at Layer 5
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Figure 2.35 Handling multiple inputs
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Figure 2.36 Each request becomes a session
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Figure 2.37 OSI updated
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Standardized formats – or why Layer 6,
Presentation, has no friends
• Presentation layer tasks solved an old problem
• Macintoshes and PCs use very different formats
• Standardized formats have been created that
allow very different operating systems to
exchange data
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Figure 2.38 Different data formats were
often unreadable between systems
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Figure 2.39 Everyone recognizes PDF files!
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Figure 2.40 OSI updated
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Network applications – Layer 7,
the Application layer
• Users use Application layer network applications
to exchange data on a network
– Network in Windows Vista/7 (My Network Places in
earlier Windows)
– Web browser like Internet Explorer or Mozilla
Firefox
– Outlook Express for e-mail
• All operating systems have APIs at the Application
layer for network-aware applications
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Figure 2.41 Network applications at work
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Figure 2.42 OSI updated
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Layer 4- Application
The four-layer
model
The TCP/IP
model
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Layer 3 - Transport
Layer 2 - Internet
Layer 1 - Link
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
• OSI model developed due to need to standardize
hundreds of protocols made by different
manufacturers
• In the end, one major protocols suite won out
and is now the de-facto standard of network and
Internet communications: Transmission Control
Protocol/Internet Protocol (TCP/IP)
• TCP/IP is both a protocol suite and a model
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
• TCP/IP model layers map to corresponding OSI
model layers
• Perform the same functions and use the same
terminology, protocols, services, devices, etc.
• Some layers map directly to corresponding
layers in OSI model, others map to multiple
layers
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
• TCP/IP does not have a “standards” body
• Results in many interpretations and variations
• Variation used for the exam is the most popular
used by Microsoft, Cisco and major players
• This variation uses four standard layers:
–
–
–
–
Link/Network Interface
Internet
Transport
Application
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Physical, hardware, and frames –
Layer 1, the Link layer
• Also called the Network Interface layer
• Corresponds to Layers 1 and 2 of the OSI model
• Handles “physical” elements (cabling, hubs, physical
addresses, and even NICs)
• Software and higher-level protocols work in higher
layers of TCP/IP stack
• Protocol Data Unit (PDU) is called a frame
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Figure 2.43 TCP/IP Link layer compared to OSI Layers 1 and 2
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
IP addressing and routing - Layer 2,
the Internet 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
• PDU at this layer is called a packet
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Figure 2.44 TCP/IP Internet layer compared to OSI Layer 3
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Segments and datagrams - Layer 3, the
Transport layer
• Maps to OSI Transport layer, Session layer, and some of
the Application layer
• Uses two protocols, TCP and UDP
• Provides both connection-oriented and connectionless
communications
• PDUs are segments (TCP) and datagrams (UDP)
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Figure 2.45 TCP/IP Transport layer compared to
OSI Layers 4, 5, and part of 6
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
• TCP provides connection-oriented
communications
• Some upper-layer protocols (for example, HTTP
and POP) require good, established connections
to function
• TCP follows a prescribed set of procedures to
establish and keep a good connection –
synchronizes session between transmitting and
receiving hosts
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Figure 2.46 Connections between e-mail client and server
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
• UDP provides connectionless communications
• Some upper-layer protocols do not require
reliable, verified connections to function
• UDP sends data without waiting to see if the
receiving system is ready or able to handle it
• Used primarily in audio and video streaming,
DNS queries, and DHCP broadcasts
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Figure 2.47 Connectionless communication with
Skype (a VoIP application)
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
• TCP segments contain header information such
as source and destination port, sequence and
acknowledgement numbers, and flags to ensure
that connections are established and verified
• Data follows the TCP header information
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Figure 2.48 TCP segment
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
• UDP datagrams only have four header fields
• No mechanisms built in to establish, verify, or
track connections or data
• Data follows the UDP header information
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Figure 2.49 UDP datagram
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
The top layer - Layer 4, the Application
layer
• Maps to the top three layers of the OSI model
• Contains many of the familiar Application layer
protocols (HTTP, DNS, DHCP, and so on)
• Allows Presentation layer formats, such as MIME, and
Application layer APIs
• Application software and APIs interface to the network
via Application layer protocols
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Figure 2.50 TCP/IP Application layer compared to OSI Layers 5-7
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Figure 2.51 OSI model and TCP/IP model side by side
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
• Each layer of both the OSI and TCP/IP models
encapsulates data by adding headers in front of
the data to be able to pass it up and down the
stack
• Data is called or known by different names as it
travels through each layer
• These names are called Protocol Data Units
(PDUs)
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
Figure 2.52 Data encapsulation in TCP/IP
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.
Mike Meyers’ CompTIA Network+® Guide to Managing and
Troubleshooting Networks, Third Edition (Exam N10-005)
• The OSI seven-layer model is a troubleshooting
tool
• Example: Jane can’t 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
© 2012 The McGraw-Hill Companies, Inc. All rights reserved.