TCP/IP Protocol (Packet Layers)

When data is being transmitted through a network the following process is used (TCP/IP):

Application Layer - This is the top layer of TCP/IP protocol suite. This layer includes applications or processes that use transport layer protocols to deliver the data to destination computers. Each different piece of software uses a different protocol so the correct one is selected. 

 The most common types of protocol used are: 
  • HTTP (Hypertext transfer protocol)
  • FTP (File transfer protocol)
  • SMTP (Simple mail transfer protocol)
Transport Layer - divides the data (coming from the application layer) into proper sized chunks and then passes these chunks onto the network (packets). It acknowledges received packets, waits for the acknowledgments of the packets it sent and sets timeout to resend the packets if acknowledgements are not received in time. The term ‘reliable connection’ is used where it is not desired to loose any information that is being transferred over the network through this connection.

Network Layer - This layer is also known as Internet layer. The main purpose of this layer is to organise or handle the movement of data on network. IP addresses of the sender and recipient are assigned at this stage so we now where the data/requests have come from/where they are going. 

Data Link Layer - This layer is also known as network interface layer. This layer normally consists of device drivers in the OS and the network interface card attached to the system. Both the device drivers and the network interface card take care of the communication details with the media being used to transfer the data over the network (is it wired or wireless). MAC addresses are assigned to the packet so we know specifically which device that data/request has come from. 

Comments

Post a Comment

Popular posts from this blog

CPU Fetch-Decode-Execute Cycle

Image
A CPU (central processing unit) executes and manages the rest of the hardware inside a computer system - it is the brain of a computer! The CPU is made up of the main memory, the processor and the cache memory. It's job is to process data (by processing we mean searching, sorting, calculating and decision making). The CPU follows the Fetch-Decode-Execute cycle. The Fetch Stage: the CPU use a piece of hardware called the ' address bus ', this is where the CPU asks the RAM for some data. The RAM then responds with this data on the ' Data Bus '.  The Decode Stage: This is where the CPU converts the instructions in to a way in which it understands it. It then gets things ready for the next step.  The Execute Stage: This is where data processing happens. Instructions are carried out on the data, as soon as the command is completed it starts the next one. 
Read more

Scheduling

Image
Scheduling is where a computer prioritises tasks to be carried out in a certain order to maximise the use of the computer and all of its peripherals. The algorithm must be robust so the computer does not freeze and also so every task/user gets a fair response time. Two main types of jobs are I/O bound jobs and processor bound jobs: I/O bound jobs (input/output) examples: Sending a document to the printer. Moving the mouse. Typing on the keyboard. Processor bound jobs examples: Playing Music Watching a video Calculating in Excel. There are different ways a processor can prioritise tasks: FCFS (first come first served) - tasks are started and completed in the order they are received. RR (round robin) – the time slice is 1 minute - each job has a minute spent on it before moving onto the next one. This occurs in a circuit until all jobs are complete. SJF – shortest job first - The job with the shortest completion time is carri
Read more

Utility Software

Image
Computer security Anti-virus - Scans/analysing your system to check for virus’ on a regular basis, if it identifies a virus that it knows of (in its database) it will remove it from the system. Spyware protection - Scans user files, checks for damage caused by installed spyware to the system and analyses domain names that potentially contain spyware. They then remove or warn the user about issues.   Firewall - use to prevent specific network packets making it onto a network. These may be blocking people from accessing certain websites or from certain files from being downloaded/uploaded. Disk organisation Defragmenter - rearranges files stored on the hard drive so related files are stored together. This makes it easier for the CPU to find files easier to find and results in much faster performance. File transfer - software designed to transfer content from one device to another. Either done from one piece of hardware to another using physical cables or done using F
Read more