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UNDERSTANDING NETWORKPROTOCOLS
Archie Bianes
Liezl Marie LagrimasIrish Mae Lirio
Karen Joy Samera
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DEFINITIONOF NETWORK PROTOCOLS
A network protocol defines rules and
conventions for communication between
network devices. Protocols for computer
networking all generally use packet
switching techniques to send and receive
messages in the form of packets.
Packet Switching - any protocol that breaks filesinto packets.
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EXAMPLES
OFNETWORK PROTOCOL
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HYPER TEXT TRANSFER PROTOCOL (HTTP)
is a method of transmitting the information on the
web.
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POST OFFICE PROTOCOL (POP)
is use to retrieve emails from the remote serverover the TCP/IP connection.
INTERNET
MESSAGE
ACCESS
PROTOCOL
(IMAP) is used to access the emails on the remote
servers.
The email messages are generally stored on
the email server and the users generallyretrieve these message whether by the web
browser or email clients
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POST OFFICE PROTOCOL VS.
INTERNET MESSAGE ACCESS PROTOCOL
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SIMPLE MAIL TRANSFER PROTOCOL (SMTP)
is a protocol that is used to send the email
messages between the servers.
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FILE TRANSFER PROTOCOL (FTP)
is used to transfer (upload/download) data from
one computer to another over the internet or
through computer network.
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USER DATAGRAM PROTOCOL (UDP)
is a most important protocol of the TCP/IP suiteand is used to send the short messages known
as datagram.
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DOMAIN NAMING SERVICE (DNS)
An Internet protocol and distributed database,
provides more English like names for IP addresses.
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TELNET
Is a protocol that allows for one machine to
connect to another computer on the Internet.
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WORLD WIDE WEB (WWW)
A protocol that uses hypertext links and
accessed by using a browser.
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-is the basic communication language or protocol of
the Internet.
Transmission Control Protocol(higher layer)
-manages the assembling of a message or file
into smaller packets that are transmitted over theInternet and received by a TCP layer that
reassembles the packets into the original
message.
Internet Protocol(lower layer)-handles the address part of each packet so that
it gets to the right destination.
TRANSMISSION CONTROL PROTOCOL/INTERNET
PROTOCOL (TCP/IP)
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TRANSMISSION CONTROL PROTOCOL/INTERNET
PROTOCOL (TCP/IP)
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OSI REFERENCE MODEL
Open Systems InterconnectionReference model
provides a general framework for standardization
defines a set of layers and services provided by
each layer one or more protocols can be developed for each
layer
Developed by the International Organization
for Standardization (ISO) also published by ITU-T (International
Telecommunications Union)
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A layered model Seven layers seven has been presented as the
optimal number of layer
Delivered too late (published in 1984)
by that time TCP/IP started to become the de
facto standard
Although no OSI-based protocol survived,
the model is still valid (in the textbooks)
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OSI - THE LAYER MODEL
Each layer performs a subset of the required
communication functions
Each layer relies on the next lower layer to perform
more primitive functions Each layer provides services to the next higher
layer
Changes in one layer should not require changes in
other layers
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THE OSI ENVIRONMENT
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OSI LAYERS (1)
Physical Physical interface between devices
Characteristics
Mechanical - interface specs
Electrical - voltage levels for bits, transmission rate Data Link
Basic services: error detection and control, flow control atthe link level (point to point)
Higher layers may assume error free transmission
Later a sub layer is added to Data Link LayerMAC (Medium Access Control) sub layer
to deal with broadcast networks
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OSI LAYERS (2)
Network
Transfer of information through communication network
network related issues
Network nodes (relays/routers) should perform switching
and routing functions QoS (Quality of Service) and congestion control are also
addressed in this layer
Several other internetworking issues
e.g. differences in addressing, max. data length, etc.
Higher layers do not need to know about underlying
networking technology
Not needed on direct links
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OSI LAYERS (3)
Transport
End to end exchange of data
In sequence, no losses, no duplicates
If needed, upper layer data are split into smallerunits
Session
Control of dialogues
whose turn to talk?
Dialogue discipline (full-duplex, half-duplex)
Checkpointing and recovery
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OSI LAYERS (4)
Presentation
Data formats
Data compression
Encryption
Application
Support for various applications
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RISKS
Availability Integrity Confidentiality
Access to
personalinformation -
Could be high
risk.
Degree of
reliance on IT- Could be
high risk.
Unauthorized
access -Could be high
risk.
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CONTROLS
Ensuring the confidentiality of data through the application of acryptographic algorithm or a secret key.
Assuring the integrity of data through the application of a
message authentication code (MAC), checksum is sent with the
data.
Providing peer authentication to ensure that network traffic anddata are sent from the expected host.
Providing replay protection to assure that the same data is not
delivered multiple times and that the data is delivered in an
acceptable order.
Providing traffic analysis protection by obscuring the identitiesof the endpoints and the size of the data.
Providing access control by assuring that only authorized users
can access particular network resources.
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NETWORK PERFORMANCE AUDIT
Before conducting a network performance audit,
internal auditors need to understand how the
network operates. The best way to do this is by
requesting a copy of the company's network
diagram.
In addition, auditors need to identify any critical
business applications that reside within the network
and the network components that support them, as
well as determine each application's network
bandwidth use.
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Network Bandwidth UseWhen assessingthe application's network
bandwidth use, the auditor should conduct a
network traffic analysis that identifies:
1. The average amount of data flowing within the
network (i.e., overall bandwidth use).
2. The data's packet size distribution.
3. The type of data flow within the network.
4. The data's error rate.
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NETWORK DEVICES CONFIGURATION
Auditors need to review the configuration of all network devices(e.g., routers and printer settings). When reviewing theconfiguration of network devices, auditors need to:
Check for routes that cause bandwidth choking orclogging of network traffic due to the use of only one
gateway.
Identify all network users and their level of networkaccess.
Determine if access control lists (ACLs) areconfigured properly and are enabled.
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Identify whether network administrators aremonitoring and tracking changes made toACLs.
Determine whether the company uses a
switch port analyser or remote networkmonitoring specification.
Identify if network administrators aretracking and limiting changes to the overallnetwork.
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NETWORK APPLICATIONS CONFIGURATION
In terms of reviewing the configuration of network applications, (e.g.,determining whether the server application is excessively querying
clients) auditors need to:
1. First understand the importance and role of thenetwork device within the organization's network
topology.
2. Be aware of best practices for network devices ingeneral.
3. Identify whether each component and sub-component of the network are missing, appliedincorrectly, or used inappropriately.
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END OF REPORT
Thank you! :)