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TCP-IP
TCP-IP is a description of network protocols developed by Vinton Cerf and Robert E. Kahn, in the 1970s
It was implemented in the ARPANET network, the first wide area network (WAN), developed on behalf of DARPA, an agency of the United States Department of Defense, and predecessor of the Internet
Sometimes referred to as model DoD or model DARPA
IP addressing
All the computers connected to a network must be identified by a unique address
Ethernet compatible computers have a unique MAC address that is 48 bits (6 bytes) long
Each manufacturer of Ethernet equipment is assigned a segment of addresses, and it is their responsibility to assign a different address to each equipment
MAC addresses are represented in hexadecimal in the following format: XX : XX : XX : XX : XX : XX, which is made up of values in the range 0-FF
Valid MAC example: 00:14:83:B2:19:45
In IP networks, the unique identification is done through the IP address
Currently it is done using the protocol IPv4 that sets the address using 32 bits (4 bytes)
The protocol will be implemented in the near future IPv6 which sets the address using 128 bits (16 bytes)
Subnet Mask
A subnet is a network in a multi-network environment that uses IP addresses derived from a single network identifier. Subnets divide a large network into multiple physical networks connected to routers. A subnet mask removes part of an IP address so that TCP/IP can distinguish the network ID from the host ID. When TCP/IP is attempted to communicate, the subnet mask determines whether the target host belongs to a local network or a remote network. Computers must have the same subnet mask to communicate within a local network
| Class | IP |
| A | 255.0.0.0 |
| B | 255.255.0.0 |
| C | 255.255.255.0 |
| D | 255.255.255.255 |
Default Gateway
It is the intermediate device of a local network that stores network identifiers for other enterprise or Internet networks. An IP address is configured for the default gateway so that it can communicate with a host on another network. TCP/IP sends packets for remote networks to the default gateway (if no other route is configured), which forwards packets to other gateways until the packet is delivered to a gateway connected to the specified destination
DNS (Domain Name System)
The idea is simple, associate names with IP addresses and provide a translation system that will be carried out by DNS servers. Obviously DNS servers are always referenced by their IP address
Domain names have a name part and a domain identifier part. The identifiers established are:
| Id | Description |
| .arpa | Identification ARPANET to Internet |
| .com | Trading company |
| .edu | Educational institution |
| .gov | Government agency | .mil | Military | .net | Related to the Internet or its providers | .org | Another organism that is not included in the previous |
This definition was created exclusively for the US, when with the expansion of the Internet, new identifiers with two letters were created to indicate a country. For example .es for Spain, .fr for France, .uk for United Kingdom, etc
An extension is foreseen with identifiers such as .info for information, .nom for nominal people
The use of a name is requested from the NIC (Network Information Center), if the name is approved it is added to the Internet database
URL (Uniform Resource Locator)
One of the objectives of the WWW was to have a system to locate and easily access any element (documents, program files, etc.), through the browser and in a simple and independent way of the protocol used
With this objective, the Uniform Resource locator was developed. A URL is a complete description of an element indicating the access protocol, the machine where it is located, the path to follow and the element's identifier
The general format of a URL is:
service://machine.domain:port/path/file?parameters
The service is one of those offered by the Internet: http, https (HyperText Transfer Protocol Secure) for secure http connections, ftp, ghoper, wais, news, telnet, mailto for sending mail and file to obtain a local file from the local disk , follows from ://
The machine.domino indicates the server that offers us the resource, for example for the University of La Rioja, the web server is www.unirioja.es and the mail server via the Web is Correo.unirioja.es
The port is optional and normally it is not necessary to indicate it if we use the one normally assigned to the service. For the Web mail server of the University of La Rioja, port 8000 is used and it must be indicated
The path is the directory path to follow to find the desired file. To separate subdirectories we will use the UNIX / slash, it is used by convention because it is the system of most servers. It is important to remember that on UNIX type machines there is a difference between upper and lower case both in the name of the directories and in the name of the files
The extension of the files is important because it tells the browser how to treat them. txt plain text file; htm or html HTML document; gif, jpg or jpeg image format, etc
In http if we do not indicate a file, in some servers they assume by default index.htm or the file that will be assigned by default
The parameters are used to pass to certain files (htm, php, ...) variable values
The format is:
variable=valor&variable=valor&variable=…
DHCP (Dynamic Host Configuration Protocol)
Protocol for Dynamic Computer Configuration. Allows you to automate the configuration of the IP address, the gateway, optional values, the address of the DNS servers, the address of the WINS servers
Users do not need to acquire IP addressing information from an administrator to configure TCP/IP. DHCP service provides all necessary configuration information on the network to DHCP clients
Valid IP addressing information ensures proper configuration, eliminating many difficult to-trace problems
Having servers running the DHCP service on each subnet eliminates the overhead associated with having to manually reconfigure IP addresses, subnet masks, and default gateways when moving computers from one subnet to another. Note that a single DHCP server can support IP address assignment for multiple networks
WINS (Windows Internet Name Service)
The WINS name resolution process allows WINS clients to register their name and IP address on WINS servers. WINS clients can query WINS servers to locate and communicate with other resources on the network
A WINS client automatically updates the WINS database whenever its IP addressing information changes, for example, when dynamic addressing through the DHCP service results in a new IP address for a computer that was moved from a subnet to other
The following steps outline the WINS name resolution process:
- Each time a WINS client starts, it registers its NetBIOS name/IP address correspondence with a designated WINS server. Then query the WINS server for computer name resolution
- When a WINS client initiates a NetBIOS command to communicate with another resource on the network, it sends a name query request directly to the WINS service instead of broadcasting the request on the local network
- The WINS server finds in its database for a matching NetBIOS name/IP address for the destination resource, and returns the IP address to the WINS client