My Netwok Dictionary

Ethernet and its evolution:

Ethernet LAN technology has been most successful, largely due to the simplicity of implementation and low cost, when compared with other technologies. Ethernet has also been successful because it is a flexible technology that has evolved to meet changing needs and abilities of the media.

10-Mbps Ethernet and 100-Mbps:

10BASE5 Ethernet, 10BASE2 and 10BASE-T are considered old implementations of Ethernet. The four common features of legacy Ethernet are timing parameters, frame format, the process of transmission and basic design rule. Read the rest of this entry »

It happened in the development of Gigabit Ethernet, the increase in the speed comes with higher requirements. A shorter bit time resulting from a higher speed requires special considerations. In the 10 GbE transmissions, each data bit lasts 0.1 nanoseconds. This means there would be 1000 bits of data at the same time GbE bit a bit of data in a data stream of 10-Mbps Ethernet. Due to the short duration of data bit 10 GbE; it is often difficult to separate one data bit of noise. The transmission of 10 GbE data depend on the exact timing of the data bit to separate the effects of noise on the physical layer. This is the purpose of synchronization.

In response to these problems of synchronization, the bandwidth and the relationship between signal and noise, 10 Gigabit Ethernet uses two different steps of encoding. By using codes to represent user data, data transmission occurs more efficiently. The encoded data provides synchronization, efficient use of bandwidth and best features of the Relationship between signal and noise. Read the rest of this entry »

A wireless network can be comprised of only two devices. The nodes can be simple workstations of desktop or handheld computers. It equipped with not wireless, a network can be established ‘ad hoc’ comparable to a wired network peer to peer. Both devices work as servers and clients in this environment. Although it provides connectivity, security is minimal, as the transfer rate. Another problem with this type of network is compatibility. Many times, the NIC from different manufacturers are not compatible.

To solve the compatibility problem is usually installed an access point (AP) to act as a central hub for infrastructure mode WLAN. The AP is connected by wiring to the wired LAN to provide Internet access and connectivity to the wired network. The AP is equipped with antennas and provides wireless connectivity to a specific area that receives the name of cell. According to the structural composition of the place where the AP is installed, the size and gain of the antennas, the size of the cell can vary greatly. Generally, the range is 91.44 meters to 152.4 meters (300 to 500 feet). To service larger areas, you can install multiple access points with a certain degree of overlap. Read the rest of this entry »

We already know that packets (or datagrams) of layer 3 in the layer 2 (link layer) to be encapsulated frames. Similarly, also assembles the IP packet from the data consists of the higher layers, and a header.

IP header contains the following fields:

• Version: Shows the used IP version. All devices must use the same IP version; device with other versions of the packages would reject (4 bits).
• Length of the IP header: Shows the length of the datagram header in 32-bit words. This is the total length of the header data, which are given under two different length header fields must be (4 bits).

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It is increasingly common to find that when you set up a connection in the home is counted with wireless access for both computers and mobile devices to access the Internet. However, many users can enter questions when talking about the security of a wireless network. Today we will try to clarify the main concerns on this issue. At the time of a wireless network, the user should take several precautions in regard to the same settings, including the level of security desired for the network.

It is always recommended that a wireless network is encrypted to prevent an outsider she can connect and access resources that should not, such as photographs or personal records. Unlike wired networks, data transmitted in one of these networks are “on air”, so there are no physical restrictions for an outsider to intercept communications. For this reason, it is important that the data are transmitted encrypted between the teams and the router. Read the rest of this entry »

An understanding of regulations and standards that apply to wireless technology will enable interoperability and compliance with all existing networks. As in the case of wired networks, the IEEE is the main generator of standards for wireless networks. The standards have been established under the regulations established by the Federal Communications Committee (Federal Communications Commission - FCC).

The key technology that contains the 802.11 standard is Spread Spectrum Direct Sequence (DSSS). The DSSS is applied to wireless devices that operate within a range of 1 to 2 Mbps DSSS A system can transmit up to 11 Mbps, but if operating above 2 Mbps are considered not compliant. Follows the 802.11b standard was approved, which increased transmission capabilities to 11 Mbps DSSS WLAN Although they could interoperate with WLAN Spread Spectrum Frequency Hopping (FHSS), problems that motivated the manufacturers to changes in design. In this case, the IEEE task was simply to create a standard to coincide with the solution manufacturer. Read the rest of this entry »

How to switch a frame to its destination port is a tradeoff between latency and reliability. A switch can start transferring the plot as soon as it receives the destination MAC address. Switching at this point is called failover cutting method and results in lower latency at the switch. However, you can check for errors. At the other end, the switch can receive the entire frame before sending it to the destination port.

It gives the switch software can control the frame check sequence (Frame Check Sequence, FCS) to ensure that the plot has been so reliable before it is sent to the destination. If it is discovered that the frame is invalid, it is discarded in this switch rather than at the final destination. Since the whole plot is stored before being sent, this mode is called warehousing and shipping. Read the rest of this entry »

The Internet is the most important data network in the world. The Internet is collected of a big quantity of interconnected small and large networks. Individual computers are the sources and destinations of information through the Internet. Wireless Internet connection can be divided into physical connection and logical connection applications.

A physical connection is connecting an adapter card, such as a modem or a NIC, from a PC to a network. The physical connection is utilized to transfer the signs among the different PC inside the network of local area (LAN) and toward the remote devices that are found on the Internet. Read the rest of this entry »

A sniffer is a program to capture network frames.

It is common that the transmission medium (coaxial cable, UTP, fiber optics etc.) be shared by several computers and network devices, which enables a computer to capture the patterns of information is not meant for it. To achieve this, the sniffer computer tells you to stop ignoring all traffic not destined for the team and pay attention, this is put in a state known as “promiscuous” to the NIC (Network Interface Card).

Currently the network security is of vital importance, since all the information transmitted through them can often be used for profit or make electronic crimes. Read the rest of this entry »

When using LAN and WAN technologies, many computers are interconnected to provide services to its users. To achieve this, the computers in network take different roles and functions between them. Some types of applications require the computer to function as equal partners. Another type of applications distributed their tasks so that the functions of a computer serving a number of other unevenly.

In either case, two computers usually communicate if using protocols request / response. A computer performs a service request, and the second computer receives and responds. The making the request assumes the role of customer, and the server responds. Read the rest of this entry »