The Ip Protocol Creates and Addresses Packets at the Layer

The TCP/IP suite is based on a iv-layer model of networking that is similar to the vii-layer open up systems interconnection (OSI) model. The following illustration shows how the TCP/IP model matches upwards with the OSI model and where some of the key TCP/IP protocols fit into the model.

As you tin can run into, the everyman layer of the model, the Network Interface layer, corresponds to the OSI model’south Physical and Data Link layers. TCP/IP can run over a wide variety of Network Interface layer protocols, including Ethernet, as well equally other protocols, such as Token Ring and FDDI (an older standard for fiber-optic networks).

The Application layer of the TCP/IP model corresponds to the upper three layers of the OSI model — that is, the Session, Presentation, and Application layers. Many protocols tin be used at this level. A few of the almost popular are HTTP, FTP, Telnet, SMTP, DNS, and SNMP.

IP

IP is a network layer protocol that is responsible for delivering packets to network devices. The IP protocol uses logical IP addresses to refer to individual devices rather than physical (MAC) addresses. A protocol called ARP (for address resolution protocol) handles the task of converting IP addresses to MAC addresses.

Because IP addresses consist of a network part and a host function, IP is a
routable protocol.
As a result, IP tin frontward a packet to another network if the host is not on the electric current network. (The power to route packets across networks is where IP gets its name. An
I
nternet
is a series of two or more connected TCP/IP networks that tin can exist reached past routing.)

TCP

TCP
is a connectedness-oriented transport layer protocol. TCP lets a device reliably send a packet to another device on the same network or on a different network.

TCP ensures that each parcel is delivered if at all possible. It does so past establishing a connection with the receiving device and and so sending the packets. If a package doesn’t arrive, TCP resends the packet. The connection is closed only after the parcel has been successfully delivered or an unrecoverable error status has occurred.

One key aspect of TCP is that it’due south always used for i-to-ane communications. In other words, TCP allows a single network device to exchange data with another single network device. TCP isn’t used to circulate messages to multiple network recipients. Instead, the user datagram protocol (UDP) is used for that purpose.

Many well-known awarding layer protocols rely on TCP. For example, when a web browser requests a folio, the browser uses HTTP to send a request via TCP to the web server. When the spider web server receives the request, it uses HTTP to fulfill the request, again via TCP. Other Application layer protocols that use TCP include Telnet (for terminal emulation), FTP (for file exchange), and SMTP (for e-mail).

UDP

The
user datagram protocol
is a connectionless ship layer protocol that is used when the overhead of a connexion isn’t required. After UDP has placed a packet on the network (via the IP protocol), information technology forgets about information technology. UDP doesn’t guarantee that the packet actually arrives at its destination. Most applications that use UDP simply look for whatever replies expected every bit a consequence of packets sent via UDP. If a reply doesn’t arrive within a certain period of time, the awarding either sends the packet over again or gives up.

Probably the all-time-known application layer protocol that uses UDP is the domain name arrangement (DNS). When an application needs to access a domain name such every bit www.dummies.com, DNS sends a UDP packet to a DNS server to look upward the domain. When the server finds the domain, it returns the domain’s IP address in another UDP packet.