1. The OSI 7 Layer Model
Ben, Stuart, Charles

5. Physical Layer The physical, wired or wireless, transmitting of data.
Type of medium
Electrical signals
Implemented by the Network Interface Card (NIC)
802.3(wired ethernet)
(WI-FI)
2.4ghz & 5ghz
These standards also share importance in the data link layer
Includes standards for pin-outs, T-568A/B

6. 2) Data Link Layer
The Data Link layer ensures that messages are delivered to the proper device on a LAN using hardware (MAC) addresses
Translates messages from the Network layer into bits for the Physical layer to transmit.
The Data Link layer is responsible for the unique identification of each device that resides on a local network.
LLC decides whether the frame is ultimately destined for another host.

7. 3) Network Layer
Manages communication between devices that are not in the same LAN.
IP addresses record the logical address of each device.
IPv4 32 Bits
Contains a subnet
Division of the network into smaller groups
subnet mask
Used to determine the network ID of the IPv4 address
IPv6 128 Bits
Route-Update Packets maintain routing information on Layer 3 networking devices.
RIP
EIGRP
OSPF
BGP
Anything with an IP address is handled by Layer 3. The main actors are hosts and routers.

8. 4) Transport Layer Logically assembles data into segments. TCP vs UDP
TCP provides flow control.
Data is sent in order.
Receiver confirms that they received the data.
Lost data is retransmitted.
UDP is not concerned with whether or not the packets have been received by the intended recipient
Ports are on this layer. Each port is like a distinct conversation between multiple hosts.

9. 5) Session Layer Five main targets of the session layer
Ensures data from different applications is sent to the correct location and is handled properly.
The Session layer is responsible for setting up, managing, and then tearing down sessions between Presentation layer entities.
It coordinates communication between systems and serves to organize their communication by offering three different modes: simplex, half duplex, and full duplex.
Session layer basically keeps applications’ data separate from other applications’ data.
Deals with lost connections and what to do with them
basically the Session layer basically keeps applications’ data separate from other applications’ data.

10. 6) Presentation Layer
The Presentation layer gets its name from its purpose: it presents data to the Application layer and is responsible for data translation and code formatting
Data compression
Decompression
Encryption
Decryption.

11. 7) Application Layer
The Application layer is responsible for identifying and establishing the availability of the intended communication partner and determining whether sufficient resources for the requested communication exist.
Serves as an Interface between applications and rest of the OSI.
Telnet - 23
File Transport Protocol (FTP) - 20/21
Simple Mail Transport Protocol (SMTP) - 24
Domain Name System (DNS) - 25
High level API
So if an application determines that it needs to utilize networking, it will be built with a protocol, which is part of the Application Layer, that will access the rest of the OSI.

12. PDU’s