Running head: NETWORK SECURITY PAPER 1

Network Security Paper

CMGT/245

March 21, 2012

NETWORK SECURITY PAPER 2

Network Security Paper

The understanding of network security is critical to ensuring the security of operating

systems. Additionally, network security incorporates such technologies as “biometrics,

cryptography, and the Internet that support key activities of authentication, data protection,

computer and network protection, and facilities protection,” (University of Phoenix, 2012). The

Open System Interconnection, OSI model is a seven-layer structure, which “data

communications between any two-networked systems,” (Global Knowledge FZ-LLC., 2012).

The paper details the information of the OSI seven-layer model. In addition, the paper describes,

“which layers do packet-filtering routers and firewalls reside, and elaborates on how do pack-

filtering routers and firewalls protect a network,” (Apollo Group, Inc, 2012).

Seven layers of the OSI model

The OSI model is tool, which helps people understand how a network works. “The OSI

model provides a comprehensive understanding of how the hardware and software elements

function together makes troubleshooting easier by separating networks into manageable pieces,”

(Global Knowledge FZ-LLC., 2012).

Layer 1 - The Physical Layer

Cables, wires, and hardware, which physically connect to a terminal allowing network

connection, have called the physical layer.

Layer 2 - The Data Link Layer

The data layer transmits raw bits to the physical layer. The data layer is a basic

addressing scheme, MAC Addresses. Additionally, the data layer is dependent on the network

NETWORK SECURITY PAPER 3

layer and the physical layer, also known as the lower layers. The “three lowest layers focus on

passing traffic through the network to an end system,” (Global Knowledge FZ-LLC., 2012).

“Common networking components that function at layer 2 include:

Network interface cards

Ethernet and Token Ring switches

Bridges,” (Global Knowledge FZ-LLC., P.1, 2012)

Figure 1: Upper and lower layers,” (telecomHall, 2012)

Layer 3 – The Network Layer

The network layer is responsible for logical addressing, which computer to be able to

group computers together.

Layer 4 – The Transport Layer

“The transportation layer provides the ability to offer end-to-end communication between

end devices through a network,” (Global Knowledge FZ-LLC., P.1, 2012). Furthermore, the

transportation layer includes such functions as the following listed below:

NETWORK SECURITY PAPER 4

Transmission- error detection

Control of data flow

Multiplexing or sharing

Layer 5 – The Session Layer

The session layer has a plethora of functions, “including applications functioning on

devices to establish, manage, and terminate a dialog through a network,” (Global Knowledge FZ-

LLC., P.1, 2012).

Layer 6 – The Presentation Layer

The presentation layer mainly pertains to the process of sending and receiving messages.

Moreover, the presentation layer incorporates such functions as encryption, compression, and

allows applications to read and comprehend the content and direction of the message.

Layer 7 – The Application Layer

“The application layer interfaces with the end users operating device connected to a

network,” (Global Knowledge FZ-LLC., P.1, 2012). The application layer enables the user the

visually see the function or end result of an application process such as a web browser.

Furthermore, Session, Presentation, and Application are the upper layers of the OSI model.

Packet-filtering routers and firewalls

Packet filtering firewalls and routers operate at different layers and a

different criterion has to restrict traffic. Although they both address incoming

data packets and the source and destination addresses. Moreover, firewalls

NETWORK SECURITY PAPER 5

and routers reside in the lower layers levels. The specific layers, which

address them, are the Layer three - Network and Layer four - Transport layer

on the OSI model, Pearson Education, Inc., (2009).

Pack-filtering routers and firewalls network protection

In conclusion, packet filtering examines each packet going in and out of the firewall.

Furthermore, pre-configured set of rules or filters inspect the information contain inside the

headers of messages and either allows or denies the packers. The packet filtering routers and

firewalls are thee network layer firewalls because the filtering is primarily done at the network

layer (layer three) or the transport layer (layer four) of the OSI reference model, Lipták (2002).

NETWORK SECURITY PAPER 6

References

Apollo Group, Inc. (2012). CMGT/245 - MENTC11 Syllabus. Retrieved from

https://classroom.phoenix.edu/afm212/secure/view-thread.jspa?threadID=41643378

Digital Foundation, inc.. (2006). 7 Layer OSI Model. Retrieved from

http://www.networkclue.com/routing/tcpip/osi-model.aspx

Global Knowledge FZ-LLC.. (2012). The OSI Model: Understanding the Seven Layers of

Computer Networks. Retrieved from http://www.globalknowledge.ae/knowledge

%20centre/white%20papers/networking%20%20wireless/the%20osi%20model

%20understanding%20t.aspx

Instrument engineers' handbook, Béla G. Lipták, ISA--The Instrumentation, Systems, and

Automation Society 2002 Retrieved July 3, 2009

Pearson Education, Inc.. (2009). The OSI model. Retrieved from

http://petersheehan.blogspot.com/2009/09/osi-model.html

telecomHall. (2012). OSI 7 Layers Model. Retrieved from http://www.telecomhall.com/osi-7-

layers-model.aspx

University of Phoenix. (2012). CMGT/245 IS Security Concepts. Retrieved from

https://portal.phoenix.edu/classroom/coursematerials/cmgt_245/20120229/