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Networking Fundamentals Chapter 2 (Open Systems Interconnection (OSI) (4.)…
Networking Fundamentals Chapter 2
Open Systems Interconnection (OSI)
1.) Physical Layer
The physical connection, from wires to jacks to electricity and light
Takes into consideration the connector types
RJ45
ST
SC
Tkaes into consideration the hardware in place
2.) Data Link Layer
Error correction and detection
works on avoiding and monitoring collisions
Media Access Control Address (MAC)
Any layer 2 communication goes through the MAC address
3.) Network Layer
Addresses traffic
Ensures the addresses reach the intended location
Internet Protocol (IP)
Routing
4.) Transport Layer
User Datagram Protocol (UDP)
Transmission Control Protocol (TCP)
Each system has 65,536 ports for both these connection sessions
Address + Port combination
Allows multiple applications to communicate simultaneously
5.) Session Layer
Authentication and authorization
Makes sure you are who you say you are, as well as ensuring you have the correct permissions
A session is a steady coherent stream designed to complete a certain task
NetBIOS
Ensures if one of the lower layers is interrupted the session is restored
Assuming that it is reestablished within a short duration of time
6.) Presentation Layer
This layer is responsible for the representation of data
XML or JPEG formats are at this layer
Formats bits and bytes of data into recognizable formats
7.) Application Layer
handles the coming and going of data to the lower layers
STMP, IMAP, and POP are all application layer protocols
TCP/IP Architectures
Department of Defense (DoD)
The Four Layers
Application Layer
There are two types of authentication protocols
Provides services directly to users
Telnet
Remote sign-in services to users
Support protocols
Simple Network Management Protocol (SNMP)
Domain Name System (DNS)
Top Three Layers of the OSI Model (Session, Presentation, Application)
Internet Layer
Where the Internet Protocol (IP) resides
Internet Layer has two primary functions
Choosing the next hop gateway
Reassembles fragmented IP Datagrams
Internet Control Messaging Protocol (ICMP)
Error and diagnostic functionality
Corresponds the the Network Layer in the OSI Model
Transport Layer
Handles end to end communication
User Datagram Protocol (UDP)
Does not pay attention to datagrams arriving or not
Transmission Control Protocol (TCP)
Delivery is guaranteed through checks
Link Layer
Corresponds the the bottom two layers of the OSI model
Once a chunk of data makes it through the Link layer it is called a frame
Address Resolution Protocol (ARP)
Translates High level addresses to Link Layer addresses
Link Layer is responsible for ensure there are no ARP floods
Defined as an RFC
Addressing
IPv4
32 bit address separated into four octets
The final 8 bits are the source and destination IPs
Subnets
Binary
10000000 = 128
11000000 = 192
11100000 = 224
11110000 = 240
11111000 = 248
11111100 = 252
11111110 = 254
11111111 = 255
4 billion addresses
IPv6
3.4 X 10^38 addresses
IP Security (IPSec)
Uses Authentication Headers (AH) to ensure messages have not been tampered with
Abbreviations for 0's
fe80::12 34:78fa - example
Synchronized Message (SYN)
'Three Way Handshake'
Mitnick Shimomura Attack
Kevin Mitnick breaks into Tsuturo Shimomura's system
TCP Number Prediction Attack
This attack highlights vulnerabilities inherent in the design of TCP/IP
Looks at the sequence numbers, there is a pattern where the sequence number counts down from the previous
Domain Name System (DNS)
Created a way of looking up information about host names and IP addresses with flexibility and scalability for a growing network