Introduction
In this section, of generally carried out of TCP / IP whirlwind tour, explained the four data transmission, link layer, network layer, transport layer and application layer, and wherein each layer was distinguished.
Meanwhile the author also describes how to perform collaborative work between the four layers, namely encapsulation and demultiplexing
Internet is a collection of numerous network, they communicate via IP address and port number.
Layering
TCP / IP is composed of four levels, four levels are:
- Application
- Transport
- Network
- Link
Layer Link , also known as data-link layer, or network interface layer, for handling various hardware problems.
Network Layer , called internet layer, for processing network packets, the protocol comprising three aspects: IP (Internet Protocol), ICMP (Internet Group Management Protocol), IGMP (Internet Group Management Protocol)
Transport Layer , whose function is to provide a channel for the exchange of the two planes, including the TCP (Transmission Control Protocol) and UDP (User Datagram Protocol ) in two.
file application Layer , the actual functions, such as FTP, SMTP, HTTP and the like.
the difference
details of the application layer for processing applications, but know nothing about the transmission data;
three layer under the application ignorant of the details, but is responsible for data transmission.
Layer is an IP hop-by-hop protocol, while the other protocol, all end-to-end protocol, wherein the IP Router may be connected to a different link layer protocol IP.
TCP has a timeout and retransmission mechanism, but there is no IP, TCP layer and therefore safer.
purpose
Built purpose is to hide all the details of the physical layout of the internet
Internet Address
Definition: Each interface must have an internet address, which is known as IP address.
Notation: 32-bit is divided into A, B, C, D, E five levels, each level comprising a number prefixes, netid, hostid.
the Domain Name System
Definitions: DNS, for providing a mapping between the IP address and hostname.
Encapsulation & Demultiplexing
Encapsulation
Defined above;
when the user application transmits information, i.e. the data from the application layer down migration time, after each layer is received, it will add some information before or thereafter, and then sent to the next layer, this concept is called encapsulation.
concepts:
in which TCP transmission is transmitted to the IP TCP segment, IP Datagram to the IP link layer is finally formed in the Ethernet frame Ethernet layer..
Demultiplexing
When the data receiving terminal to receive information, the information carried in the header are explained in layers and removed, and then a layer retransmission up the header information is removed, this process is called demultiplexing.
In the process of demultiplexing, the need to use the source IP address & port number and destination port address & port number.
Client-Server Model
All networking application assume that one end is client, the other end is a server, and therefore the presence of two types of server, and the server respectively Iterative concurrent server.
Handling Iterative server as:
- Wait for a client request to arrive
- Process the client request
- Send the response back to the client.
- Go back to STEP 1.
concurrent server are handled as follows:
- Wait for a client request to arrive
- Start a new server( to handle this client's request, and terminates when complete)
- Go back to STEP 1
Port number
ephemeral port: a client's port, is only present in the time client landing, thus short lived in the
UNIX system, the port number is located in / etc / services may be utilized
grep telnet / etc / services to find these port locations.

Internet & internet
the difference
Refers to the Internet can be able to communicate on a global scale by the host TCP / IP protocol,.
Internet refers to a protocol by using a common connection network of the group. Is a collection of networks
contact
Internet is a kind of internet.