Operation of an electronic data network

 Operation of an electronic data network

 An electronic data network can be simply defined as a system that links two or more points (terminals) by means of a physical medium, which serves to send or receive a certain flow of information.

 An electronic data network has a number of functions described below:

·         Electronic networking infrastructure and skills: this function helps network members to have the necessary equipment (hardware and software) and skills to work with the electronic network. This can be assumed through the development of a web page, emphasizing skills workshops, software advice among others.

·         Basic communication: in this function, various exchanges can be carried out quickly and easily at necessary moments between actors, i.e. people connected to the work team and geographically dispersed, but who at certain times need to cooperate. This is mainly done through email lists or through large documents or data for access to partners, but also includes access to contact details.

·         Creation of relationships: basically this function; allows people to easily create a network of contacts with those who need or wish to interact, to which they can resort in order to better perform their work through an electronic data network.

Computer equipment configuration

 In every computer network there is communication equipment that is designed to establish that connection between computers, but in order to carry the data transmission of a network, through the workstations and computers it is necessary to configure the modem, transmission channel processors, communication processors and the data PBX. It is very important to know their configuration in order to guarantee the interconnection in the network. This interconnection of diverse equipment brings with it multiple advantages. 

Saving material costs. In addition, the use of shared software allows an application to be used from different workstations, resulting in greater productivity. With the configuration of the in networked computers the administration and support tasks are simplified and made more accessible since from the same location the network administrator can perform the different administrative tasks in any computer of the network.

• Server installation

   The installation and configuration of a server with the Debian operating system will be carried out. One of the most common ways to install it are the CDs with the images and the installation over the Internet. As it is not necessary more than the basic programs, it is more than profitable to do the installation by Internet

  The process:

  1.    Download the disk images from the same Debian FTP. The floppy disk size images for the stable version and an x86 processor, can be found at

  ftp://ftp.debian.org/debian/dists/stable/main/disks-i386/current/images-1.44

  2.    Download the following files; driver-1.bin, driver-2.bin, driver-3.bin, driver-4.bin, rescue.bin yroot.bin.

  3.    Burn the images on 1.4 Mb floppy disks. This can be done from Linux with the command dd if=image-name.bin of=/dev/fd0 or from Windows with programs like rawrite2 or others that transfer the file byte by byte to the floppy.

  4.    Insert the diskette into rescue.bin and turn on the computer. When boot appears: press Enter. After some time it will ask for the diskette to root.bin and continue the installation.

  5.    Continue the installation in the normal way, paying special attention to the following points:

  ·         Partitions: two are necessary: a swap (type 82) not very big (more or less the same number of Mb as the computer RAM, although a value between 50 and 100 Mb. is already good), and the rest of the disk destined to the other partition, of type Linux Native (number 83), with a mount point in the root (" / "). If possible, better create first the Native and then the swap to be able to call them later/dev/hda1 and /dev/hda2 respectively. You should also mark the Native as bootable.

• ·         When you ask where the kernel is, indicate that in the floppy disk drive: /dev/fd0 and insert the disks you request.

  ·         Kernel modules: at least the drivers for the network card must now be added.

  ·         Host name: we can change it at any time, but better to decide one now and not change it. For example, bruguers.

  ·         Computer IP: usually you put the network IP, finished in a small number. For example, in our case we can put 192.168.0.2 (192.168.0.1 is for the router).

  ·         Lilo: it's not necessary because we only have one operating system, but it's not necessary to install it either. It will be fine if we want to be able to boot with different kernels.

  ·         Starter disk: not necessary, but it's always good to have one.

  1.    After rebooting, we will continue with the system customization. We will select the recommended options, making sure to activate the shadow password option.

  2.    When creating users, you must enter the root password, the most important user on the system. It is extremely important to choose a good password. Also, for security reasons we will not always work with the root user (it is dangerous) but create another normal user account (with our name or nickname).

  3.    When you ask from where to install the packages, indicate that by ftp and choose one from the list (for example, ftp.debian.org). Then, Debian will use apt to download the latest versions of each program. We will have to decide which groups of programs we decide to install. We will follow these indications:

  ·         You will not need the X's (for the graphic mode), because everything you need can be done from the console.

  ·         Games and entertainment programs either.

  ·         Web servers, DNS, mail, etc. will be installed individually in the different sections, so they should not be marked either.

  ·         C and C++ tools: they are basic to compile the programs. They have to be installed.

  ·         Environment in Spanish: optional. If we check it, some help pages will be in Spanish, but they may not be as up to date.

  4.    By marking a few packages we make sure that nothing is installed that we don't need. If we don't do this, when the installation is finished there will be so many services available that someone could take advantage of them and enter the server without permission.

• 1.    When everything is ready, the list of packages to be downloaded and what they occupy will appear. We tell you to continue and leave the computer on as you download each package along with its dependencies. When it's done, we'll have to configure some while others will be unpacked and installed automatically. If he asks how to configure the mail, we tell him that we don't want to configure it; this way we will avoid many unnecessary bugs.

  2.    At the end we will end up in the login screen, which will appear every time we turn on the computer to ask us for the user name and password.

  Access lists

   Access lists are the mechanism for selecting traffic. Once a set of packets has been selected the router can perform various tasks on them. One of the most widespread uses of access lists is to control the flow of incoming and outgoing traffic to a router. The process of configuring access lists consists of two general steps, the creation of the access list and its application in the corresponding interface. There are mechanisms at the time of having a proper reload, reset and loopback configuration.

   In some cases access lists are used in computer security to encourage separation of privileges. This is because it is a way of determining the appropriate access permissions for a given object. Depending on certain aspects of the ordering process ACLs are characterized by the ability to control the flow of traffic on network equipment such as routers and switches. Its main objective is to filter traffic, allowing or denying network traffic according to some condition. However, they also have additional uses, for example, to distinguish "interesting traffic" (traffic important enough to activate or maintain a connection) in ISDN. 

• There is a reason why they are usually managed in a separate class or system, and not in each of the parts that are intended to be associated with permissions, is because they follow SOLID rules, in this case the S (Single Responsibility Principle), which allows you to even better scale. It would be similar to a typical physical access control system of a building, where that part is centralized in one place. This place only needs to know two things: Who you are (for example, a card ID, your user ID) and what you want to do. Answer whether you have permission to do so or not. With this approach this same system can be used not only to access places but for anything that needs to be separated from people who can and cannot do things, for example: access a page or section, post a comment, make a friend, send an email.

   In computer networks, ACL refers to a list of rules detailing service ports or domain (network) names that are available on a terminal or other network layer device, each with a list of terminals and/or networks that are allowed to use the service. Both individual servers and routers can have network ACLs. Access control lists can generally be configured to control inbound and outbound traffic and in this context are similar to a firewall.

   There are two types of access control lists:

  ·         Fixed lists.

  ·         Variable lists.