Identify and discuss the seven layers of the Open System Interconnection (OSI) model and their importance on TCP/IP operation.
Minimum two pages.
Helpful topics to research:
OSI Layers
How TCP/IP Works
TCP/IP Operates on Open Systems Interconnection Levels 3 (IP) and 4 (TCP)
TCP/UDP/RTP User Datagram Protocol
TCP/IP Address Schemes
APA format
Lesson 13
University of the Cumberlands
Professor: Dr. Irvin R. Heard
Course: ISOL 634 Physical Security (20-21)
Reading Assignment
- Chapter 17
Individual Project 13
Identify and discuss the seven layers of the Open System Interconnection (OSI) model and their importance on TCP/IP operation.
Minimum two pages.
Helpful topics to research:
- OSI Layers
- How TCP/IP Works
- TCP/IP Operates on Open Systems Interconnection Levels 3 (IP) and 4 (TCP)
- TCP/UDP/RTP User Datagram Protocol
- TCP/IP Address Schemes
Open Systems Interconnection (OSI) Reference Model
- Layer 7–Application layer
- Layer 6–Presentation layer
- Layer 5–Session layer
- Layer 4–Transport layer
- Layer 3–Network layer
- Layer 2–Data Link layer
- Layer 1–Physical layer
OSI – Upper and Lower Levels
- The seven layers of the OSI reference model can be divided into two categories: upper layers and lower layers.
- The upper layers of the OSI model deal with application issues and generally are implemented only in software. The highest layer, application, is closest to the end user. Both users and application-layer processes interact with software applications that contain a communications component. The term upper layer is sometimes used to refer to any layer above another layer in the OSI model.
- The lower layers of the OSI model handle data transport issues. The physical layer and data-link layer are implemented in hardware and software. The other lower layers generally are implemented only in software. The lowest layer, the physical layer, is closest to the physical network medium (the network cabling, for example, and is responsible for actually placing information on the medium.
TCP/IP
The networking industry uses the OSI seven layer model as a standard, however before that was a standards TCP/IP was being developed (OSI was just completed first and adopted). Both models have similar goals. Its often to see developers apply OSI terminology to TCP/IP.
Similarities
The most compatible aspects at the Transport and Internet layers (called the Network in OSI)
TCP/UDP/RTP
Click the titles to review resources
TCP/IP Address Schemes
- TCP/IP includes an Internet addressing scheme that allows users and applications to identify a specific network or host to communicate with. An Internet address works like a postal address, allowing data to be routed to the chosen destination. TCP/IP provides standards for assigning addresses to networks, subnetworks, hosts, and sockets, and for using special addresses for broadcasts and local loopback.
- Internet addresses are made up of a network address and a host (or local) address. This two-part address allows a sender to specify the network as well as a specific host on the network. A unique, official network address is assigned to each network when it connects to other Internet networks. However, if a local network is not going to connect to other Internet networks, it can be assigned any network address that is convenient for local use.
Internet Address
Internet Addresses
The Internet Protocol (IP) uses a 32-bit, two-part address field. The 32 bits are divided into four sections or octets as in the following:
01111101 00001101 01001001 00001111
These binary numbers translate into:
125 13 73 15
The two parts of an Internet address are the network address portion and the host address portion. This allows a remote host to specify both the remote network and the host on the remote network when sending information. By convention, a host number of 0 (zero) is used to refer to the network itself.
TCP/IP supports three classes of Internet addresses: Class A, Class B, and Class C. The different classes of Internet addresses are designated by how the 32 bits of the address are allocated. The particular address class a network is assigned depends on the size of the network.
Class A
Class A Addresses
A Class A address consists of an 8-bit network address and a 24-bit local or host address. The first bit in the network address is dedicated to indicating the network class, leaving 7 bits for the actual network address. Since the highest number that 7 bits can represent in binary is 128, there are 128 possible Class A network addresses. Of the 128 possible network addresses, two are reserved for special cases: the network address 127 is reserved for local loopback addresses, and a network address of all ones indicates a broadcast address.
Therefore, there are 126 possible Class A network addresses and 16,777,216 possible local host addresses. In a Class A address the highest order bit is set to 0.
In other words, the first octet of a Class A address is in the range 1 to 126.
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Class B
Class B Addresses
A Class B address consists of a 16-bit network address and a 16-bit local or host address. The first two bits in the network address are dedicated to indicating the network class, leaving 14 bits for the actual network address. Therefore, there are 16,384 possible network addresses and 65,536 local host addresses. In a Class B address the highest order bits are set to 1 and 0.
In other words, the first octet of a Class B address is in the range 128 to 191.
Class C
Class C Addresses
A Class C address consists of a 24-bit network address and an 8-bit local host address. The first two bits in the network address are dedicated to indicating the network class, leaving 22 bits for the actual network address. Therefore, there are 2,097,152 possible network addresses and 256 possible local host addresses. In a Class C address the highest order bits are set to 1 and 1.
In other words, the first octet of a Class C address is in the range 192 to 223.
When deciding which network address class to use, you need to consider how many local hosts there will be on the network and how many subnetworks there will be in the organization. If the organization is small and the network will have fewer than 256 hosts, a Class C address is probably sufficient. If the organization is large, then a Class B or Class A address may be more appropriate.
Discussion Board 13
How can the OSI Seven-Layer Network Model be applied to Information Security?
Questions
