It also makes sure that the data arrives, resending datagrams where necessary. But for a question that fits in a single datagram, we don’t need all the complexity of TCP to do this. If we don’t get an answer after a few seconds, we can just ask again. For applications like this, there are alternatives to TCP.

  • Another advantage of TCP/IP is that the IP packets don’t have to be sent to the same type of server.
  • This address may change between connections, but allows all devices to be identified on the internet for the purpose of data packet addressing.
  • Examples of some error messages returned by ICMP which are useful to both network hosts and devices such as routers, include Destination Unreachable and Time Exceeded.
  • Press theWindowskey on your keyboard and then enter “command prompt” to display theCommand Promptshortcut.
  • The internet is a prime example of this type of network.

The protocol defines the specific set of responses that can be sent as answers to any given command. However programs that don’t want to analyze them in detail can just look at the first digit. In general, responses that begin with a 2 indicate success. Those that begin with 3 indicate that some further action is needed, as shown above.

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Every session must begin with a HELO, which gives the name of the system that initiated the connection. (There can be more than one RCPT command, if there are several recipients.) Finally the data itself is sent. Note that the text of the message is terminated by a line containing just a period. (If such a line appears in the message, the period is doubled.) After the message is accepted, the sender can send another message, or terminate the session as in the example above.Generally, there is a pattern to the response numbers.

– The datagram is checked for corruption and the correct address. – If all is ok the Network Access Layer extracts the data and passes it to the designated protocol. Wikipedia articles on the Internet, packet switching and IP addresses. How many control bits will be used to control data transfer. This section provides general and specific information pertaining to networking, including an overview of network concepts and detailed discussion of popular network protocols. Another advantage of TCP/IP is that the IP packets don’t have to be sent to the same type of server.


A Wide Area Network is a network that covers a large geographical area. The internet is a prime example of this type of network. Quite a number of Wide Area networks are built by Internet service providers and are sold to people and companies via subscriptions. At each end of the leased line, a router connects to the LAN on one side and a hub within the WAN on the other. SMTP is used by mail servers to send and receive mail from all other mail servers around the world. FTP is the protocol used to upload or download (i.e. transfer) files between computers and the internet.

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Furthermore, every host implementation of TCP/IP must be prepared to accept pieces and put them back together. The most common alternative is UDP (“user datagram protocol”). UDP is designed for applications where you don’t need to put sequences of datagrams together.

In this lesson, learners will look at how networking protocols are used to ensure that clients can communicate and share information across computer networks. They will then learn about some key networking protocols that are used for much of the communication across the internet. Finally, learners will work together in small groups to design their own networking protocol to meet a set of objectives and to try to overcome a number of restrictions. This layer sets up the communication between the two hosts and they agree settings such as ‘language’ and size of packets. This is where the network applications, such as web browsers or email programs, operate. It is also where the transfer and email protocols operate.