LAN and WAN

Ethernet became LAN standard was very popular at the moment. Compared with its competitors in the past 20 years the network Token Ring, Ethernet has won this fight due to the nature / karakteristic superiors; ease and low cost but reliable. So the Ethernet network is more widely used on the local LAN network or networks connected to the LAN and WAN network form. From the original commercial specifications with the ability to transfer data only up to 10 Mbps, with the ability to network Ethernet 10 Gigabit-per-second today, Ethernet networks have evolved and become the most popular Ethernet protocol so far.

Ethernet defines both Layer 1 (Physical Layer) and layer2 (Data Link Layer) of the OSI reference model. Phyisical layer and data link layer works together to provide the function of sending data through various types of physical networks. Some details of the physical function must be met before any communication takes place, such as cable networks, type-2 connectors are used at the ends of two wires, and so is the level of voltage and current used to encode binary 0 and 1.

Data Link layer protocols define or rule-2-2 to determine when a computer may use the physical network when the computer is not supposed to use the network, and how to find the errors that occur during transmission of data.

The term Ethernet refers to the family of protocols and standards that together-2 defines physical layer and data link from the most popular type of LAN. There are many variants of Ethernet include:

1. 10 Base-T

2. Fast Ethernet

3. Gigabit Ethernet

10Base-T Ethernet network

10-BaseT Ethernet network allows us to use existing telephone wiring, or a cheaper cable if needed a new cable. 10-BaseT Ethernet network using what is called a HUB devices. Physical network using Ethernet 10-BaseT Ethernet Card or NIC (Network Interface Card) on the computer, cabling and a hub (which is one of the most ancient network devices).

HUB used in 10-BaseT Ethernet network is basically a multiport repeater. This means that the HUB is only 2 devices amplifier electrical signal that goes to one of the ports and distributed to all ports of the HUB, so crash (collision) is very possible.

Network cabling Ethernet 10Base-T

10-BaseT Ethernet network using Category 5 UTP cable with RJ-45 connectors.

The cable used to connect computers to the HUB using Straight-through cables
The cable connects between the HUB using a cross cable.

In some kind of hub or switch now been using autosensing - which identify the type of cable you are, so do not have to use a cable cross - just use a straight through cable for all connections.

Collision be a performance problem HUB

Network Ethernet 10-Base2; 10Base5, and 10BaseT not be able to walk without the CSMA / CD. However, the algorithm CSMA / CD, Ethernet becomes less efficient at higher loads, Ethernet will be a slow start when network load exceeds 30% usage.

How CSMA / CD logic helps keep the collision (collision) as well as how he reacts when a collision occurs. Like the highway in both directions, as well as what happens on the network vulnerable HUB collision. The algorithm CSMA / CD can be explained as follows:

1. A network device with a frame of data to be sent, first to listen to the network whether it is quiet or not.

2. If the Ethernet network is no longer busy, the sender begins sending data frames to the network.

3. The sender look to determine whether a collision or not.

4. As soon as the sender knows the event of a collision, they each send a signal jamming-2 (signal path congestion) to ensure that all stations know that a collision has occurred.

5. As soon as the jamming signal is sent, the sender calculates every (timer) randomly and wait for it anyway before they start sending the frame to the network.

6. If the timer is up, then the process starts again from the beginning steppertama, and so on up to successfully send a data frame to the fixed address.

LAN Swith - reducing collisions

Collision term defines a set of device domains within a boundary that allows a data frame collisions occur. All devices on a network 10Base2, 10Base5, and 10Base-T HUB menggunkaan risk collisions between frames that they send, so all devices that exist on any type of Ethernet networks are in one collision domain.

For that emerged LAN Switch that can overcome this problem domain collisions and also problems algorithm CSMA / CD to relieve the possibility of collision. Unlike HUB, Switch does not create a shared bus, Switch treats each port as a separate bus. Switches use a memory buffer to hold data frames are coming, so if there are two devices on Switch tergubung simultaneously transmit data, the switch sends the frame and holds the second frame into a memory buffer, then wait to send the second frame to the first frame was finished being sent so it will never happen collisions.

Full-Duplex - eliminating collisions

Original specification of Ethernet is using a shared bus, while at the same time there is only one frame that could be sent or lajim called Half-Duplex. LAN switches with only one device connected to each port on the switch allows operation Full-Duplex. Full-duplex means that an Ethernet card can send and receive frames simultaneously.

Conclusion Ethernet Network

Protocol-2 physical layer defines how to transmit data across the physical medium. Protocol-2 data link layer is useful to make the physical network by defining how and when the physical network is used. Defining an Ethernet network layer of the OSI model serves first for Ethernet networks, including cabling, connectors, voltage level, and the cable distance limits, as well as many important functions of Layer 2 of the OSI model.