What shall we know about TCP/IP?
Communication between computers, in a network, needs to be done with some communication protocols. A protocol means a set of rules and conventions between different participants to a common activity, in this case information transfer between computers.
Being complex, the protocols are designed on levels (layers). Every layer defines services and proper protocols. There are many protocols models, but the most used and known are OSI and TCP/IP.
TCP/IP is actually the first settled. He was defined in relation with the first computer network sometime around the 70th. The name result from its two main protocols. Here is the internet level used for packages communication. The transport level is like the OSI one. Here we define two important protocols TCP (Transmission Control Protocol) and UDP (User Datagram Protocol). At application level the most known protocols are: TELNET (virtual transmission), FTP (file transmission), SMTP (the electronic mail) and HTTP (hypertext).
Protocols used in Internet
The protocols used in Internet allow interconnections between different networks like LAN and WAN. TCP and IP are low level protocols, but the Internet protocols has also high level protocols. Lets see some
- ARP protocols (Address Resolution Protocol) and RARP (Reverse Address Resolution). ARP is used for connection between a Internet address and a hardware address and RARP realizes a inverse connection.
- IP (Internet Protocol) and ICMP (Internet Control Message Protocol)-ICMP is used for transmitting command information and set errors between networks components.
- TCP and UDP. Many applications programs in Internet are based on TCP. UDP is used in smaller and simplest application.
- The last levels in OSI corresponds with FTP, Telnet, SMTP, SNMP(Simple Network Management Protocol).
IP level
IP protocol send datagrams from a source address to a destination address. Sending datagrams it can be done in an independent way because besides the information sent, a datagram contains the source and the destination address.
IP protocols uses Internet addresses represented on 32 bytes. IP addresses are divided in five classes: A, B, C, D, E in terms of the way the four bytes are used.
Application level
There are many protocols but I am going to discuss about few:
DNS relates to a symbolic name gave to a node and to the correspondence between these names and the Internet addresses. There are superior name domains and each of them are divided in subdomains and so on. At the superior level (level 1) there are two domains categories: generics and country names. Generics domain are: .com (comercial), .edu(educational),. gov(guvernamental), .org(non-profit organizations). Example of name countries domains : .fr(France), .uk(Great Britain).
The e-mail services uses the SMTP protocols witch is dedicated for transmitting messages with ASCII content. The services suppose to send, receive, edit messages etc.
World Wide Web(WWW) is the most well-known Internet application who allow sending documents, pictures, etc. In WWW there is a distinguish between the client side and the server side. A WWW server administrates documents and send it to the clients. For a docs identifications we use (Universal Resource Locator URL).
protocol://computer:port/name#label
- protocol - http (for hypertext documents), ftp (for file transmission), file (for accessing a local file)
- computer - the name of the node where is the document
- port - the port where the server runs for the specified documents
- name - the path name of a file
- label - an optional element which can indicate for a location in the document.
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