Networking Flashcards
Network
A network is simply two or more computers linked together to share data, information or resources.
Hubs
Hubs are used to connect multiple devices in a network. They’re less likely to be seen in business or corporate networks than in home networks. Hubs are wired devices and are not as smart as switches or routers.
Switches
Switches are wired devices that know the addresses of the devices connected to them and route traffic to that port/device rather than retransmitting to all devices.
Routers
Routers are used to control traffic flow on networks and are often used to connect similar networks and control traffic flow between them. Routers can be wired or wireless and can connect multiple switches. Smarter than hubs and switches, routers determine the most efficient “route” for the traffic to flow across the network.
Firewalls
Firewalls are essential tools in managing and controlling network traffic and protecting the network. A firewall is a network device used to filter traffic. It is typically deployed between a private network and the internet, but it can also be deployed between departments (segmented networks) within an organization (overall network). Firewalls filter traffic based on a defined set of rules, also called filters or access control lists.
Server
A server is a computer that provides information to other computers on a network. Some common servers are web servers, email servers, print servers, database servers and file servers. All of these are, by design, networked and accessed in some way by a client computer. Servers are usually secured differently than workstations to protect the information they contain.
Endpoint
Endpoints are the ends of a network communication link. One end is often at a server where a resource resides, and the other end is often a client making a request to use a network resource. An endpoint can be another server, desktop workstation, laptop, tablet, mobile phone or any other end user device.
MAC
Media Access Control (MAC) Address - Every network device is assigned a Media Access Control (MAC) address. An example is 00-13-02-1F-58-F5. The first 3 bytes (24 bits) of the address denote the vendor or manufacturer of the physical network interface. No two devices can have the same MAC address in the same local network; otherwise, an address conflict occurs.
IP
Internet Protocol (IP) Address - While MAC addresses are generally assigned in the firmware of the interface, IP hosts associate that address with a unique logical address. This logical IP address represents the network interface within the network and can be useful to maintain communications when a physical device is swapped with new hardware.
Upper Layer
1. Application
2. Presentation
3. Session
The upper layer, also known as the host or application layer, is responsible for managing the integrity of a connection and controlling the session as well as establishing, maintaining and terminating communication sessions between two computers. It is also responsible for transforming data received from the Application Layer into a format that any system can understand. And finally, it allows applications to communicate and determines whether a remote communication partner is available and accessible.
Lower Layer
4. Transport
5. Network
6. Data Link
7. Physical
The lower layer is often referred to as the media or transport layer and is responsible for receiving bits from the physical connection medium and converting them into a frame. Frames are grouped into standardized sizes. Think of frames as a bucket and the bits as water. If the buckets are sized similarly and the water is contained within the buckets, the data can be transported in a controlled manner. Route data is added to the frames of data to create packets. In other words, a destination address is added to the bucket. Once we have the buckets sorted and ready to go, the host layer takes over.
OSI model
The OSI Model was developed to establish a common way to describe the communication structure for interconnected computer systems. The OSI model serves as an abstract framework, or theoretical model, for how protocols should function in an ideal world, on ideal hardware.
osi model layers
When someone references an image file like a JPEG or PNG, we are talking about the Presentation Layer (6).
When discussing logical ports such as NetBIOS, we are discussing the Session Layer (5).
When discussing TCP/UDP, we are discussing the Transport Layer (4).
When discussing routers sending packets, we are discussing the Network Layer (3).
When discussing switches, bridges or WAPs sending frames, we are discussing the Data Link Layer (2).
Payload
As data is encapsulated at each descending layer, the previous layer’s header, payload and footer are all treated as the next layer’s payload. The data unit size increases as we move down the conceptual model and the contents continue to encapsulate.
At Application layer
TCP/IP protocols include Telnet, File Transfer Protocol (FTP), Simple Mail Transport Protocol (SMTP), and Domain Name Service (DNS).
