wiki

OEM

OEM is an acronym for Original Equipment Manufacturer. As its name suggests, OEMs are companies that manufacture products for other companies that will typically re-brand the products and sell them. This is very common practice where companies with strong brand recognition would source products from other companies that either don’t have the same brand recognition or simply prefer to do business with other businesses only.

For example, power supplies are a product that companies commonly source from OEM manufacturers. While EVGA has an entire lineup of power supply offerings, all of these power supplies are manufactured by other companies such as Seasonic, Super Flower, and FSP. As such, Seasonic, Super Flower, and FSP can be referred to as OEM companies even though they also sell products under their own brand.

online proxy

An online proxy, or web proxy, is a proxy service that is operated using the web browser. Online proxies are useful for improving privacy by keeping your IP address private or for bypassing simple firewall restrictions.

Generally, online proxies can be used by simply visiting the online proxy’s website which can then be used to access other websites on the internet. This is the greatest advantage to using an online proxy as there’s no software to install and no system settings to change.

While online proxies sound like they function similar to VPN services, there is however one important distinction. Online proxies do not provide any sort of encryption capability, so the data transferred can still be monitored whereas VPN services generally provide encryption capabilities so that the data transferred cannot be monitored. Further, online proxies only protect the web browser connection and offers no additional privacy for other services such as e-mail, gaming, torrents, etc.

OSI Reference Model

The OSI Reference Model, or Open Systems Interconnection Reference Model, is a framework that defines the rules and procedures on how data should be sent across a network.

According to the model, which was developed by ISO (International Organization of Standardization) in 1984, there are 7 layers to the model, which is used together to form most packets sent across any network in existence.

OSI Reference Model

Layer Layer Name Protocol Data Unit Common Example
1 Physical Bit 10/100/1000 Ethernet, 802.11a/b/g/n/ac
2 Data-link Frame MAC, Frame Relay
3 Network Packet IP, OSPF, RIP
4 Transport Segment / Datagram TCP, UDP
5 Session Data RPC, SQL
6 Presentation Data SSL, TLS
7 Application Data HTTP, FTP

Layer 1 – Physical

The physical layer is the most obvious layer which covers anything physical to connect network devices. As the physical layer, it’s responsible for taking electrical signals and translating them into bits.

Layer 1 examples include cables, network cards, wireless radios, switches, routers, and more.

Layer 2 – Data-Link

The data-link layer is responsible for encapsulating, or packaging all the other layers after it, into a frame so that it may be sent across the physical layer.

The data-link layer contains two sub-layers: MAC (Media Access Control) and LLC (Logical Link Control).

  1. The MAC sub-layer is used to control how devices gain access to the network and get permission to transmit which is why the MAC address is so important.
  2. The LLC sub-layer is responsible for encapsulation, error checking, and frame syncing, or essentially how data is transmitted and received at layer 2.

Layer 2 examples include Ethernet, 802.11 Wi-Fi, Frame Relay, and more.

Layer 3 – Network

The network layer is responsible for controlling communications between networks. As such, it’s responsible for addressing, or assigning/identifying the host and the network the host is on, and routing, or figuring out how to get a packet from point a to point b in the most efficient way.

Layer 3 examples include IP (Internet Protocol), OSPF (Open Shortest Path First), RIP (Routing Information Protocol), and more.

Layer 4 – Transport

The transport layer is responsible for ensuring that data transferred between two devices is correct and error free.

There are two types of transmissions that occur with the transmission protocol – connection oriented transmissions and connectionless transmissions.

  1. Connection oriented transmissions require that a connection be established first before data is sent.
  2. Connectionless transmissions do not require a connection is established.

Layer 4 examples include TCP, UDP, and more. TCP is a connection oriented protocol, which is why it needs to go through a handshake process before data is sent. UDP is a connectionless protocol, which means data is blasted into the network without the distant end confirming data can be received.

Layer 5 – Session

The session layer is responsible for creating, maintaining, and ending sessions between network devices.

Layer 5 examples include RPC, SQL, and more.

Layer 6 – Presentation

The presentation layer is used to format data for the application layer to use. In addition, the presentation layer is also responsible for providing encryption/decryption and compression/decompression of files.

Layer 6 examples include JPG, GIF, MP3, WAV, AVI, MOV, ASCII, SSL, TLS, and more.

Layer 7 – Application

The application layer is the final interface between the application used on a system and the network. This is typically all protocols.

Layer 7 examples include HTTP, HTTPS, FTP, and more.

over-provisioning

Over-provisioning in SSDs is a method of maintaining SSD performance and increasing SSD endurance by either allocating a portion of NAND to be used as “swap space” when the drive is at capacity or as a replacement for degraded NAND cells.

Currently, consumer SSDs generally feature 7% over-provisioning while enterprise SSDs generally feature 28% over-provisioning. Some enterprise SSDs however, have been known to have over 50% over-provisioning for improved write endurance.