Chapter 2
Communicating Over the
Network
Modified by Profs. Chen and Cappellino
Objectives

This chapter prepares you to:

Describe the structure of a network, including the
devices and media that are necessary for
successful communications.
 Explain the function of protocols in network
communications.
 Explain the advantages of using a layered model
to describe network functionality.
 Describe the role of each layer in two recognized
network models: The TCP/IP model and the OSI
model.
 Describe the importance of addressing and
naming schemes in network communications.
The three Elements of Communication
The first - message ___________, or sender.
 The second -________________, or receiver



receives the message and interprets it.
A third - a __________________
the
media that provides the pathway over which
the message can travel from source to
destination.
Communicating the Messages

In theory, a single communication, such as a an
e-mail message, could be sent across a network
from a source to a destination as one
massive continuous stream of bits.


Why is this not a good idea?
The solution: divide data into
_____________, more manageable pieces
to send over the network.
This
division of the data stream into smaller
pieces is called ___________________.
Communicating the Messages

Segmenting messages has two primary
benefits.
First,
many ___________________________
_________ or mixed together on the network.

The process used to mix together the pieces of separate and
distinct conversations on the network is called ______________.
Second,
segmentation can _______________
______________ of network communications.


Separate pieces need __________________________ across
the network from source to destination.
If part of the message fails to make it to the destination, _______
__________________________________________________
Communicating the Messages

Disadvantage of segmentation and
multiplexing

______________________________________
Each packet must be individually addressed and
numbered
 Then reassembled into the content of the original
message.


Devices throughout the network and
protocols ensure that the pieces of the
message arrive reliably at their destination.
Components of the Network

_____________________ are the physical elements
or _____________________ of the network.

Can you list some examples of devices?
 Can you list some examples of media?

_______________________________________
that run on the networked devices.
Services
include ______________________________ we
use. What are some examples?
 ____________________________________ that directs
and moves the messages through the network


The set of rules which help determine what goes where
______________________ consist of ___________
or _________________________ (more to come…)
End Devices and their Role on the Network

Example of end devices:
____________________________
(work stations,
laptops, file servers, web servers)
Network _____________________
______________________________
Security cameras
__________________________________ (such as
wireless barcode scanners, PDAs)

End devices are referred to as ______________.
A host

______ have software installed that enables them to provide information
and services, like e-mail or web pages, to other hosts on the network.


can act as a client, a server, or both.
Network computer that responds to client requests for network resources
_____________________________________ obtained from the server.
Intermediary Devices and their Role on the Network

Networks rely on ___________________________
_______________________ and ensure that data
flows to destination


work behind the scenes
Examples of intermediary network devices are:
_________________________
Devices (____________
__________________, and wireless access points)
_______________________________ (____________)
Communication Servers and Modems
_______________________ (_________________)

In managing data, _________________ devices use
the ___________________________, in conjunction
with information about the network interconnections,
in path determination
Intermediary Devices and their Role on the Network

Processes possibly running on some or all the
intermediary network devices are:
________________________________
_____________________________
about what
_________________________________
_____________________ other devices ____________
and communication failures
Direct data along __________________________ when
there is a link failure
Classify and direct messages according to QoS
priorities
__________________________________, based on
security settings – ACL’s
Network Media


Communication across a
network- from source to
destination is carried on a
_____________________.
These media are:

____________ within cables

Data sent via ___________ pulses

___________________ (fiber
optic cable)


Data sent via ________________
______________ transmission

Data sent via electromagnetic
_________________
Network Media

Different types of network media have different
features and benefits.
 The
___________________ the media can
successfully carry a signal
 _____________ can carry a signal the farthest
 The __________ in which the media is to be installed
 ___________ best in “noisy” environments
 The ________________________ at which it must be
transmitted.
 Cat 5 can go fairly high and is often very sufficient
but fiber is best
 The ________________ of the media and installation
 ________________ is most costly!
Network Infrastructures

Vary greatly in terms of:
 The
size of the area covered
 The number of users connected
 The number and types of services available

Different types include:
 ___________
(Local Area Networks)
 ___________ (Wide Area Networks)
 ___________ (Storage Area Networks)
 ETC
Local Area Networks


An individual ______________
network
__________________________
_____________________
providing
services to people within
a __________________________,


single business, campus or region.
Administered by a ___________
______________________
The
administrative control that
governs the security and access
control policies are enforced on the
_______________________

Ie. – under control of that business itself
Wide Area Networks


__________________________
________________________
Typically _________________
capacity
slower

than LAN’s
_____________ (businesses)
that are at distant locations

businesses generally use a
_________________________
___________ (TSP) to interconnect
the LANs at the different locations.
WANs use specifically designed
network devices to make the
interconnections between LANs.
The Internet – A Network of Networks


Enables user to communicate with a resource on
another network, outside of our local organization.
Internetwork (aka Network)
The
most well-known and publicly-accessible internetwork
is the Internet.
Internet Service Provider (ISP) networks _____________
_________________ to help form the Internet


Use generally accepted standards and protocols
Intranet

Refers to ____________________________________
___________________________________________
_______________________, or others with authorization.

Accessed internally or remotely
Network Representations



Recall “Elements of a Network” from
Chapter 1
We will be using visual representations
often so please commit them to memory
Additional important terms:
______________________
- A NIC, or LAN
adapter, provides the ________________
__________________ or other host device.

The media connection plugs directly into the
NIC.
Physical
Port - A _________ or outlet on a
networking device ___________________
___________________
Interface - Specialized ports on an
internetworking device ________________
_________________________________

the ports on a router are referred to
_____________________
Rules that Govern Communications

For successful communication,
_____________________________
must be followed by both parties
These
protocols are ________________
______________________ that is loaded
on each host and network device.

Easy way to think of protocols
interacting with each other to help
move data along, is to think of a stack
or layered hierarchy.
Each
__________________________
depends on the functionality defined by the
____________________________

Higher level protocols focus on message
being sent and user interface
The
____________________ of the stack
are concerned with __________________
__________________________
Network Protocol Suite:

____________________________________
______________________________



used in a computer network
Example: ________________protocol suite
Must describe precise requirements and
interactions such as:
The
______________ or structure of the message
The ____________ by which networking devices
share information about pathways with other networks
How and when __________ and system messages
are ______________________________
The ___________________ of data transfer sessions
Proprietary Network Protocols

Individual protocols in a protocol suite _____
_________________________________

_______________ or vendor ___________ the
definition of the protocol and how it functions.
Not so with the TCP/IP protocol suite

________________________________
Industry Standards
A process or protocol that ______________
_________________________ and ratified
by a ________________________
Ex:
the Institute of Electrical and Electronics
Engineers (IEEE) or the Internet Engineering
Task Force (IETF).
Use of standards ensures that products _____
____________________________________ for
efficient communications.

Can anyone think of an example of a
product/process or protocol that is
considered standard?
Example: interaction of protocols between
a web server and a web browser.

___________________________:
Hypertext
Transfer Protocol (HTTP) is a
protocol that governs the way that a web
server and a web client interact.


HTTP defines first- the content and formatting of the
requests and second- the responses exchanged
between client and server.
How are the messages transported?...
___________________________:
______________________________
________________________________
________________ - in this examplebetween web servers and web clients


TCP divides the HTTP messages into __________
_________________________, to be sent to the
destination client.
TCP also controls the rate at which messages are
exchanged.
Example: interaction of protocols CONT…

____________________________:
Internet
Protocol (IP) is responsible for taking the
segments (from upper transport layer),
___________________________, _______
___________________________________


Then selecting the ________________________
to the destination host.
________________________________:
Network access protocols describe two primary
functions, _____________________ and the
______________________ of data on the media.

 Data-link management protocols take the packets from IP
(the above layer) and format them to be transmitted over the
media.
 The standards and protocols for the physical media govern
______________________________________________ and
how they are interpreted by the receiving clients.
 Transceivers on the network interface cards (NICs)
implement the appropriate standards for the media that
is being used.
Technology Independent Protocols
Networking protocols describe the _______
__________ during network communications.
 Protocols generally __________________
________________ a particular function.
 This is why many protocols are said to be
___________________________

This
means that a computer - and other devices
– can, for example, access a web page stored on
any type of web server (IIS, Apache, etc) that
uses any form of operating system (Windows,
MAC, Linux) from anywhere on the Internet.
The Benefits of Using Layered Model

________________________
protocols
that operate at a specific layer have
defined information that they act upon and a
defined interface to the layers above and
below.




_________________ because products
from different vendors can work together.
_____________ technology or capability
_______________________________
_______________ above and below.
________________ to describe
networking functions and capabilities.
Helps us visualize and __________ about
networking and protocol interaction
Protocol and Reference Models


There are two basic types of
networking models: protocol
models and reference models.
A _______________ model:
provides a model that ________
__________________________
______________________.
The
hierarchical set of related protocols in
a suite typically represents all the
functionality required to interface the
human network with the data network.
The ____________________ (seen in
previous example) is a protocol model
because it describes the functions (and
protocols) that occur at each layer of the
TCP/IP suite.
________ Model
Protocol and Reference Models

A _______________ model:
helps provide ____________
_______________________
involved in all types of network
protocols and services.
 Not
intended to provide a sufficient
level of detail to define precisely the
services of the network architecture.
 The _________________________
___________ is the most widely
known internetwork reference model.
 Used in ___________, operation
specifications, and troubleshooting.
________ Model
The TCP/IP Model


It defines ________ categories
of functions (in layers) that must
occur for communications to be
successful.
An _____________________
________________________
________________________
over definitions and standards of
the model
Definitions and standards
(including use of the protocols)
defined in a publicly-available set
of documents

_____________________________
Please memorize
the functions
represented at leach
layer
Communication Process

(through the TCP/IP model)
A complete communication process includes these steps:
1. _____________ at the application layer of the __________ device
2. __________________________________ of data as it passes
down the protocol stack in the source end device
3. Generation of the data _______________________ at the
network access layer of the stack
4. _____________________________________________, which
consists of media and any intermediary devices
5. _________________ of the data at the network access layer of
the _____________________ device
6. _____________________ of the data as it passes up the stack in
the destination device
7. Passing this data to the destination application at the Application
layer of the destination device
Protocol Data Units and Encapsulation

______________________

__________________________
_______________________

The encapsulation process:
As
application data is passed
down the protocol stack various
________________________ to it
_______________________.
The form that a piece of data
takes at any layer is called a
_______________________
During encapsulation, each
succeeding layer encapsulates
the PDU that it _____________
__________________ in
accordance with the protocol
being used.
Protocol Data Units and Encapsulation

At each stage of the process, a
PDU has a different name to
reflect its new appearance.
 ______
- The general term for the
PDU used at the _____________
 ________ - _____________ PDU
 _________ - _______________
Layer PDU
 ____________ - _____________
___________ PDU
 ______________ - A PDU used
when __________________ data
over the medium
The Sending and Receiving process

(from Web Server to client)
In the web server example from earlier:
The Application layer: HTTP begins the process by delivering the
HTML web page data to the Transport layer.
The Transport layer: The application data is broken into TCP
segments.


Each TCP segment is given a label, _____________, containing information
about which process running on the destination computer should receive the
message.
The Transport layer: encapsulates the web page HTML data within the
segment and sends it to the Internet layer,
The Internet layer: Here the entire TCP segment is encapsulated
within an IP packet, which adds another label, called the IP header.

The IP header contains source and destination IP addresses.
 The Network Access layer: Using the Ethernet protocol, the
packet is encapsulated within a frame header and trailer.




Frame header contains source and destination physical address.
The trailer contains error checking information.
Finally the bits are encoded onto the Ethernet media by the server NIC.
This process is reversed at the receiving host.
Data
travels up the layers of the model
The OSI Model




Designed by the ______________
_____________________________
___________ (ISO)
Provides an extensive list of
functions and services that can occur
at each layer.
It also describes the ____________
_____________________________
____________________________
NOTE:
Although the content of this course
will be structured around the OSI
Model
 the
focus of discussion will be the
protocols identified in the TCP/IP
protocol stack.
Supplementary OSI
layer slides
ALL PEOPLE SEEM TO
NEED DATA PROCESSING
7. The Application Layer

_______________________________
________________________
 provides
general network access
Directly supports user applications
 The OSI layer ____________________
 Applications it supports are outside the
OSI layer model

 Example

of applications:
________________________________
6. The Presentation Layer
Ensures that data sent by the application
layer of one system is readable by the
application layer of another system
 ________ the way data is _____________
__________________________

5. The Session Layer

____________________________
_____________________ between
applications on different computers
4. The Transport Layer
Segments data from the sending host &
reassembles data on the receiving host
 ________________________________
________________________________
____________________________.

 Error
detection-and-recovery
 Information flow control
 Involved in Quality Of Service, Reliability
3. The Network Layer

_________________________________
______________ between two end
systems
 based
on network conditions, priority of
service etc
__________________ occurs at this layer
 __________________ occurs at this layer

2. The Data Link Layer
Provides reliable __________________
______________________ (media)
 ______________ (vs. logical)addressing
 Cyclical redundancy check (_______)
allows for __________________________

1. The Physical Layer

Defines the _______________________
__________________________
specifications for the ______________
 Wires,

connectors, voltages, data rates
Transmits ______________________
over the physical medium
Comparing the OSI and TCP/IP Model

The key parallels between the two models occur at
the OSI model _______________________

L3 of OSI deals with addressing and routing of
messages


Functions at L4 of OSI include acknowledgement,
error recovery, and sequencing.



The ___________________ is the TCP/IP suite protocol
that includes the functionality described at ___________
______________________________ includes the
functionality described at ________________
Application layer and the Network Access layer of the
TCP/IP model are further detailed in the OSI model
At the TCP/IP Network Access Layer,
 the
TCP/IP protocol suite does not specify which
protocols to use when transmitting over a physical
medium; it only describes the handoff from the Internet
Layer to the physical network protocols.

The TCP/IP Application layer

OSI model Layers 5, 6 and 7 are used as references for application software developers
and vendors to produce products that need to access networks for communications.
Addressing in the Network


The OSI model describes the processes of
encoding, formatting, segmenting, and
encapsulating data for transmission over the
network.
Using the OSI model as a guide, we can see the
different addresses and identifiers that are
necessary at each layer.
Address
identifiers are added to the data (using
encapsulation) as it travels down the protocol stack on
the source host.
Getting the Data to the End Device
Focusing on Layer 2 PDU – Frame…

Host physical address, is contained in
the header of the frame.
The physical address is also called the
______________________________


Layer 2 is concerned with the delivery
of messages on a _____________
_______________________
The
MAC address is unique on the local
network and _______________________
_______________________________

Once a frame is successfully received
by the destination host, the Layer 2
address information is removed as the
data is decapsulated and moved up the
protocol stack to Layer 3…
Getting the Data Through the Internetwork
Focusing on Layer 3 PDU – Packet…

Layer 3 protocols are designed to ____
________________________________
_____________ within an internetwork.
Layer
3 addresses must include _________
that enable intermediary network devices to
_______________________________

Every _________________________
________________________________
__________________________
___________
use the __________ identifier
portion of this address to determine which
path to use to reach the destination host.
Once the path is determined, the router
encapsulates the packet in a new frame and
sends it on its way toward the destination
end device.
When the frame reaches its final destination,
the frame and packet headers are removed
and the data moved up to Layer 4.
Getting the Data To the Right Application

At Layer 4, information contained in the PDU header
(segment) identifies the _____________________
__________________________________________
___________________________________
Hosts can run ______________________________.
 Example: e-mail client running at the same time as a web browser,
an instant messaging program etc
 All these separately running programs are examples of individual
processes.

Each application or service is _______________ at
Layer 4 by a ________________________
A unique
dialogue between devices is identified with a pair
of Layer 4 source and destination port numbers that are
representative of the two communicating applications.
When the data is received at the host, the ____________
_______________________________________________
______________________________________
Putting it all together
OSI
TCP/
ISO Layer
Layer
IP
Name
#
#
7
Application
(All)
4
6
Presentation
(People)
5
Session
(Seem)
4
Transport
(To)
3
3
Network
(Need)
2
2
Data Link
(Data)
1
1
Physical
(Processing)
Devices
Encapsul
or
TCP/IP
ation
Keywords/Description
Compon Protocols
Units
ents
FTP, HTTP,
POP3, IMAP,
Network services for
telnet,
application processes, such
SMTP, DNS, as file, print, messaging,
TFTP
data
PC
database services
Standard interface to data
Application
for the application layer.
MIME encoding, data
encryption, conversion,
data
formatting, compression
Interhost communication.
Establishes, manages and
data
terminates connection
between applications
TCP, UDP
End-to-end connections
and reliability.
Segmentation/desegmentat
Transport segments
ion of data in proper
sequence. Flow control
IP
Logical addressing and
path determination.
Internet packets
Routing. Reporting delivery
router
errors
Physical addressing and
access to media. Two
bridge,
sublayers: Logical Link
Network
frames switch,
Control (LLC) and Media
Access
NIC
Access Control (MAC)
repeater,
Binary transmission signals
hub,
and encoding. Layout of
bits
trancieve
pins, voltages, cable
r
specifications, modulation
TCP/IP
layer
Name