The Basic Local Area Network

Published Date: 02 Nov 2017

Local Area Network is a usually high- speed network that covers a small geographical area. It is using for Information sharing and Resource Sharing. It is usually use in the single building or campus. Ethernet is most common LAN technology. A LAN requires hub, router, radio or radio technology.

Information sharing means, user can access the same files, exchanging the information/data through the emails or using internet.

Resource sharing means, organization having some hardware devices shared by all users within the organization. Etc. printers, scanners, fax machines, laptops, PCs and PDAs. Having some software packages shared by all users on a LAN. Reduced the hardware cost. User devices must consist of specialized hardware as well,

Example – bar code scanners and patient monitoring

Basic Local Area Network (LAN)

NIC (Network Interface Card) NIC (Network Interface Card)

Cables Cables

Client Hub Network Server

In the network a computer act as a server and other computers are act as a clients. The server is connected to a hub, clients are also connected to the same hub. Now that the computers each a have one a common electric door (hub), they can use the hub pass signal back and forth. To direct these signals, Routers are another name for Hub. The router is the similar of an electronic traffic that handles data traffic between the computers.

Network Interface card means every computer in the network it must have a net work card installed, name is Network Interface Card (NIC). These devices each have a primary address. In hard-wired networks, called another name for cabling Ethernet runs from the network card to hub. In a wireless the network cards and ROUTERS communicate with each other by using radio waves.

Routers means it used to, on single network have ability to use resources on other network frames would have go through number of networks connecting to number of networks called Routers.

Ethernet

Ethernet is a part of the technology that provides data-link and physical specification for controlling access to a shared to a network medium. It has emerged as the dominant technology used in the LAN networking.

There are several benefits over the LAN technologies

Easy to install and manage

Inexpensive

Flexible and scalable

Easy to interoperate between vendors.

Ethernet Standards

The 802 committee

Committee of the institute for Electrical and Electronics Engineers (IEEE).

Created the 802 MAN/Local Area Network Standards Committee for LAN standards.

This committee is usually called the 802 Committee.

The 802 Committee creates groups working for common types of standards.

802.1 for General Standards

802.3 for Ethernet Standards

802.11 for wireless LAN standards.

802.16 for WiMax Wireless Metropolitan Area Network .

The 802.3 Working Group

This group is in charge of making Ethernet standards.

The terms 802.3 and Ethernet are interchangeable today.

Figure6-4 shows Ethernet physical layers standards.

Ethernet also has data link layer standards.

Ethernet Cabling Types

4-Pair Unshielded Twisted Pair (UTP)

Coaxial Cabling

Twisted – Pair cabling (TP)

Fiber Optic cabling

4-Pair Unshielded Twisted Pair (UTP)

Ethernet is the dominant LAN standards family.

Ethernet LANs usually use 4-pair unshielded twisted pair wiring to merge hosts to the closers switch.

They also use Unshielded Twisted Pair to merge switches to other switches.

Unshielded Twisted Pair cabling uses copper wires.

Unshielded Twisted Pair mostly used for telecommunication and customer networks. It contains of various types of copper wires that have twisted into similar pair. Unshielded Twisted Pair cable doesn’t give as larger bandwidth or as good security from interference as coaxial cables or fiber optic, but it is less high cost and easier to handle it.

twisted-pair-cable-utp.jpg

Unshielded Twisted Pair (UTP)

There are some types of twisted pair cables, recognize by the number of twists per inch of the copper pairs.

CAT 3- 3 twists per inch

CAT 5- 5 twists per inch

CAT 5e – same as the CAT 5 but pairs are twist around each other.

CAT6 – 6 twists per inch, improved insulation.

Cord organization

A long of Unshielded Twisted Pair wiring is a cord.

Each cord has eight copper wires.

Each wire is insulated with dielectric (non conducting) insulation.

The wires are used four pairs.

Each pair’s two are twisted it each around other several times per one inch.

There is an outer plastic jacket that covers the four pairs.

Connectors

RJ-45 connector is the standard connector.

It plugs to an RJ- 45 jack in a host.

Characteristics

Inexpensive and easy to purchase.

Easy to install.

Represent in channel for access a links between a HOST and the closers SWITCH.

Uncrimped_rj-45_connector_close-up.jpg

RJ – 45 Connector

Coaxial Cables

Coaxial cables consist of a single wire surrounded by insulation, a metallic shield, and a plastic sheath. The shield use to protect against electromagnetic interference (EMI). This can cause attenuation, a reduction of the strength and quality of a signal. EMI can be generated by a variety of sources, such as florescent light ballasts, microwaves, cell phones, and radio transmitters. Coaxial cables are commonly used in television to homes and business.

Less prone to interference than Twisted Pair (TP) due to shield

More expensive than Twisted Pair (TP).

Using in TV cables.

There are two types of coaxial cables were used in historically in Ethernet networks such as

Thinnet

Thicknet

coaxla.gif

Coaxial Cable

Both Coaxial Cables and Twisted Pair Cables transmitting electronic signals, Fiber Optics use to transmit the signals, it is very fast than the other cables. Ethernet have two types of fiber cables such as

Single mode Fiber

It has a small glass core,0 it is allowing a single ray or mode of light to go across it. This will reduces the attenuation and dispersion of the LED or Laser signal.

It is provide high bandwidth over very long distances, measured in kilometers.

Multimode Fiber

It has a large core. Allowing multiple modes of light to transmit it. It supported for shorter distance.

Twisted – Pair cabling (TP)

Twisted pair usually use for telephones and Local Area Networks (LAN).

Decrease the electromagnetic interference.

Twisted pairs cables have number of pairs of wires.

Telephones used 2 pairs.

LAN used4 pairs.

Also used in telephone trunk lines

Shielded twisted pair can also use but cost is very expensive.

twisted-pair-cable.gif

Twisted Pair Cabling

Fiber Optics Cables

It is use a LED or Laser light to transmit a signal.

Signal transmits through the glass or plastic fiber.

It has extremely high capacity, useful for broadband.

It is properly worked under the harsh environment.

Types of fiber optics

Multimode fiber( mention in above)

Single mode fiber(mention in above)

Graded index multimode

Decrease problem by changing the refractive resources of the fiber to refocus the transmission.

It can be used over distance up to about 1000 meters.

fiber-optics.jpg

Fiber Optics

Optical Fiber Wavelength

Windows for every good glass propagation

850 nanometers (nm) +/-50mm

1310 nanometers (nm) +/-50mm

1550 nanometers (nm) +/- 50mm

Longer wavelength travel deeply.

Longer wavelength are more expensive to generate

For LAN distance, 850nm dominates because it gives sufficient distance.

Unshielded Twisted Pair VS Fiber Optics

Fiber is good for going deeply, not going faster

Unshielded Twisted Pair and Fiber Optics can be used for speeds up 10 Gbps

Fiber optics can span longer distances

Less than 100 meters, use less expensive 4 pair unshielded twisted pair.

Beyond 100 meters, fiber optics is very useful.

Hubs, Switches, Routes

Switches are generally identified as Layer -2 devices(Data-Link Layer), as switches process information stored in the Data-Link header of a frame (such as MAC address in Ethernet).similarly, routers and identified as layer-3 devices(Network Layer), as routers process logical addressing information in the Network header of a packet (such as an IP address).

Following icons will be used represent network devices

switch.jpg

m switch.jpg router.jpg hub.jpg

Hubs

Amplify signal.

All devices in the same collision domain.

All devices in the same broadcast domain.

All devices share available bandwidth

Hubs are belongs to physical layer. It is use to connect network devices together for communication. Hubs can also call as repeaters.

Thus, hubs will always forward every frame out every port, excluding the port originating the frame. Hubs do not differentiate between frame types, and thus will always forward unicasts, multicasts, and broadcasts out every port bur the originating port.

Ethernet hubs operate at half-duplex, which allows a device to either transmit or receive data, but not simultaneously. Ethernet utilizes Carrier Sense Multiple Access with Collision Detect (CSMS/CD) to control media access. Host devices monitor the physical link, and will only transmit a frame if the link is idle.

If these two devices transmit simultaneously, a collision will happen. if collision will identify, the hub will discard the frames and signal the host devices. Both devices take a random time amount and after that transmit the signal again.

Multiple hubs that are uplinked together still all belong to one collision domain. Increase the number of host devices in a single collision domain will increase the number of collisions. This can significantly degrade performance.

Hubs also used to only one broadcast domain- a hub will forward both broadcasts and multicasts out every port but the originating port. A broadcast domain is a logical segmentation of a network, dictating how far a broadcast (or multicast) frame can propagate.

Hub

Client A Client B Client C

How hubs are working

Switches

This is way how packet are switching to the destination

` Client Host

Packet switch A

Packet switch C

Packet Switch B

Packet switch E

Packet switch D

Packet switch F

Destination Host

Physical Link

Data Link

Packet switch A receives packet addressed to Destination Host .packet switch A decided to send the Frames/Packets to C or B. This is forwarding decision.

The packet switches do not know the entire path. Its only knows the next switch (B or C).

Physical links are the connection between two switches devices.

Data Link is the packets path through the network

Ex. Client Host  A  B  E F  Destination Host

This is the entire path of that particular packet.

Data link layer forwarding was original referred to as bridging. Bridging is a largely deprecated term (mostly for marketing purposes), and Data- Link layer forwarding is now commonly referred to as switching.

There some subtle technologies difference between bridging and switching. Switches usually have a higher port-density, and can perform forwarding decisions at wire speed, due to specialized hardware circuits called ASICs(application-specific Integrated Circuits). Otherwise, bridges and switches are nearly identical in functions.

Ethernet switches build MAC- address tables through a dynamic learning process. A switch behaves much like a hub when first powered on. The switch will flood every frame, including uncasts, out every port but the originating port.

The switches will then build the MAC-address table by examining the source MAC address of each frame. Consider the following diagram

Computer A

Computer B

Fa0/11

Fa0/10

When Computer A send a frame to Computer B, the switch will add Computer A’s MAC address to its table, associating it with port fa0/10. However, the switch will not learn Computer B’s MAC address until Computer B sends a frames to Computer A, or to another device connected to the switch. Switches always learn from the source MAC address.

While hubs were limited to half-duplex communication; switches can operate in full duplex. Each individual port on a switch belongs to is own collision domain. Thus switches create more collision domains, which results in fewer collisions. Like hubs though, switches belong to only one broadcast domain. A layer-2 switch will forward both broadcasts and multicasts out every port but the originating port. only layer-3 devices separate broadcast domains.

Routers

Usually hardware devices are designed to take incoming packets, analyzing and send packets to the destination. Converting the packet, dropping the packets or performing other actions.

A router has lot of benefits than the other devices (hub and switch). Hub used to transfer the data between computers or network devices, doesn’t analyze or can do something with the data it is transferring. Routers can identify the data be sent to a network, change its package and send it to another different networks. Routers usually used in home networks because it share a single network with a multiple computers. There are two types of routers and wireless routers. Router also using internet to share data and files among the users.