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Network-Security Fundamentals Course Notes
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9/13/24, 11:05 Network-Security Fundamentals CoursePM Notes
1. Introduction to Computer Networks
Protocol: a set of rules established for users to exchange information
Topology: the physical architecture of a network
Network Topologies:
- Star: the most common networking topology in today’s LANs. Devices are connected
via twisted-pair cables with modular plugs. At the center of the network is a switch
or hub, connecting the network devices and facilitating the transfer of data.
- Bus: All LAN data traffic is carried over a common coaxial cable link. This topology
prevents data transmission from being very bandwidth efficient.
- Mesh: All devices are directly connected to each other, providing full redundancy in
the network data paths. This method is very costly due to the additional data paths,
which increase cabling and networking hardware costs.
- Token Ring: A “token” is placed in the data channel and circulates around the ring.
For a user to transmit data, it must wait until it has control of the token, known as
token passing. This is known as a deterministic network, where access to the
network is provided at fixed time intervals.
OSI (Open Systems Interconnection) Model: A seven-layer model that provides a framework for
networking, ensuring compatibility in the network hardware and software, along with
accelerating the development of new networking technologies.
1. Physical Layer: provides electrical and mechanical connection to the network.
2. Data Link Layer: handles error recovery, flow control, and sequencing. It is
considered the “media access control layer” and where MAC addressing is defined.
3. Network Layer: accepts outgoing messages and combines messages or segments
into packets, adding a header that includes routing information. It acts as the
network controller. ftIP, IPX)
4. Transport Layer: Is concerned with message integrity between source and
destination. It also segments/reassembles packets and handles flow control. ftTCP,
UDP)
5. Session Layer: Provides the control functions necessary to establish, manage, and
terminate the connections as required to satisfy the user request. ftNFS, SQL)
6. Presentation Layer: Accepts and structures the messages for the application. It
translates the message from one code to another, if needed. This layer is responsible
for data compression and encryption. ftASCII, JPEG)
7. Application Layer: Interacts with application programs that incorporate a
communication component such as your Internet browser and email. This layer is
responsible for logging the message in, interpreting the request, and determining
what information is needed to support the request. ftHTTP, FTP, SMTP)
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PM Notes
Frame: a format the provides grouping of the information for transmission, which includes
header, data, and trailer.
- The header includes the preamble fta pattern of 1’s and 0’s for synchronization), start
frame delimiter ft8-bit binary sequence indicating the frame start), destination MAC
addresses, source MAC addresses, and length/type field ftindication of the number of
bytes in the data field).
- The data section includes the actual data being transmitted, and the padding ftused
to bring the total bytes up to the 46-byte minimum if the data is less).
- The trailer section includes the frame check sequence fta 4-byte cyclic redundancy
check [CRC] used for error checking).
Jumbo Frame: any frame that has data above 1500 MB’s
MAC (Media Access Control) Address: a unique address contained in each NIC ftNetwork
Interface Card) which is made up of 6 bytes ftdisplayed in 12 hexadecimal digits). The first 6
digits, known as the OUI ftorganizationally unique identifier), and the last 6 digits form a unique
value for each NIC. You can find your MAC address ftsometimes known as physical address), by
going in the CMD prompt and typing “ipconfig /all”.
IP (Internet Protocol) Address: a unique address that identifies the computer’s local network,
assigned by the IANA ftInternet Assigned Numbers Authority). They are classified as IPv4 or IPv6,
with IPv4 being the current TCP/IP addressing technique used on the Internet. The IP address is
a 32-bit address that identifies which network a computer is located and differentiates the
computer from all other devices on said network. IP Addresses are written as 4, 8-bit parts, with
the format being A.B.C.D, which each section ranging from 0-255.
IP Address Classes ftthe numbers indicate the network number, while the x’s indicate the host or
device number):
Class Description IP Examples Max Hosts
Class A Governments/Large Networks 44.x.x.x or 8.x.x.x 2^24=16,777,214
Class B Midsize companies, universities, etc. 128.123.x.x 2^16=65,534
Class C Small Networks 192.189.1.x 2^8=254
Class D Multicast Groups 224.x.x.x N/A
Intranet: an internal network that provides file and resource sharing but is not accessed from
the Internet.
Wireless Standards:
- 802.11a: provides data transfer rates up to 54 Mbps at a range of 75 ft; 5GHz
- 802.11b: provides data transfer rates up to 11 Mbps at a range of 100-150 ft; 2.4GHz
- 802.11g: provides data transfer rates up to 54 Mbps at a range of 150 ft; 2.4GHz
- 802.11n: provides data transfer rates at 200+ Mbps; 2.4GHz or 5GHz
- 802.11ac: provides data transfer rates up to 1.3 Gbps; 5GHz
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PM Notes
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