3: Network + (OSI Model) (Jason Dion)

Layer 1

Physical

Layer 2

Data Link

Layer 3

Network

Layer 4

Transport

Layer 5

Session

Layer 6

Presentation

Layer 7

Application

Data Types in OSI Model (Descending)

Data, Segments, Packets, Frames, Bits

Physical Layer

Where Transmission of bits across a network occurs and includes Physical and Electrical characteristics. (Wiring Standards, bandwidth usage, multiplexing strategy)

TIA/EIA-568B

Wiring standard for RJ-45 cables

Crossover Cable Wiring Standard

TIA/EIA - 568A and 568B

Straight Through Cable Wiring Standard

TIA/EIA 568B or 568A on both ends

Asynchronous Communication

Uses start bits and stop bits to indicate transmission occurence

Synchronous Communication

Uses reference clock to coordinate transmisison

Broadband

Bandwidth is divided into separate channels

Baseband

Uses all available frequency on a medium and uses reference clock to coordinate transmission

Multiplexing

difference types of data are transmitted on the same media for more efficient use

Data Link Layer

Data is transmitted as a frame using a MAC address to identify recipients and senders. (Mac, Physical addressing, logical topology)

Media Access Control (MAC)

48 bit address for NIC. first 24 bits vendor code, second 24 bits unique value. Physical Address

Logical Link Control (LLC)

Provides connection services for layer two. Provides flow and error control.

Isonchronous

Network uses common clock to create transmission time slots. Least overhead. Isochronous is about predictable timing intervals, even within a synchronous framework

Synchronous

Uses control character or timing channel to create reference clock for transmission

Asynchronous

Network devices reference there internal clock for transmission time

Network Layer

Forwards traffic, Packets, using logical address, IP. (Switching, Route Discovery and selection, bandwidth usage)

Packet Switching

Data is divided into packets and forwarded. (Envelope, can get there different ways but arrives in the same spot)

Circuit Switching

Dedicated communication link. (Phone call, during conversation data goes the same way) establishes a dedicated, end-to-end physical path (circuit) between two endpoints before data transmission

Message Switching

Data is divided into messages then sent. Like packet switching but data can be stored then forwarded.

Internet Control Message Protocol (ICMP)

A TCP/IP protocol that is used by devices to communicate updates or error information to other devices.

Examples Layer 1

Cables, Radio Frequencies, Hubs, Wireless AP, Media Converters

Examples of Layer 2

NIC, Bridges, Switches

Examples Layer 3

Router, Multilayer switch, IP, ICMP

Transport Layer

Divides upper and lower layers. Data is sent as Segments. (TCP, UDP, Windowing, Buffering)

Transmission Control Protocol (TCP)

Connection oriented. (SYN, SYN ACK, ACK)

User Datagram Protocol (UDP)

Connectionless. Good for audio and video streaming. No guaranteeing delivery, order, or error correction

Windowing

Allows client to adjust the amount of data sent with each Segment. (Download speed changing until it finds a set speed)

Buffering

allocating memory to store data when bandwidth isn't available

Examples of Layer 4

TCP, UDP, Firewalls

Session Layer

Think of it as a conversation that needs to be kept separate so it doesn't get interrupted. (Sets up, Maintains, Tears down seesion)

Setting Up Session

Starting a conversation where everyone introduces themselves and decides who talks first

Maintaining Session

Asking a question data is transferred and conversation ends when the question is answered

Tearing Down Session

Conversation ends when both parties decide or one stop talking

Presentation Layer

Formats and secures data

Data Formatting Types

ASCII, GIF, JPG

Application Layer

Unites communication components from more than one network device. (Email, File transfer, remote access)

OSI Model Layers Top Down Example

Application Layer (7): You request a webpage.

Presentation Layer (6): Data is encrypted and formatted for transmission.

Session Layer (5): A connection (session) is initiated with the web server.

Transport Layer (4): Data is broken into segments, with port numbers added.

Network Layer (3): Segments become packets, with source/destination IP addresses added for routing.

Data Link Layer (2): Packets become frames, with MAC addresses for local delivery.

Physical Layer (1): Frames are converted to electrical signals (bits) and sent over the cable.

OSI Model Layers (People Don't Need Those Stupid Packets Anyway)

Physical, Data Link, Network, Transport, Session, Presentation, Application