Engineering & Technology

Saturday, 8 February 2014


#include<iostream.h>
#include<conio.h>
void main()
{
int a,b;
clrscr();


cout<<"\n\nEnter the two no=:";
cin>>a>>b;
cout<<"\na"<<a<<"\nb"<<b;


a=a+b;
b=a-b;
a=a-b;


cout<<"\n\na="<<a<<"\nb="<<b;
getch();
}








Learn Easy way of calculating sin-cos-tan values.

Swapping using two variables in C++


#include<iostream.h>
#include<conio.h>
void main()
{
int a,b;
clrscr();


cout<<"\n\nEnter the two no=:";
cin>>a>>b;
cout<<"\na"<<a<<"\nb"<<b;


a=a+b;
b=a-b;
a=a-b;


cout<<"\n\na="<<a<<"\nb="<<b;
getch();
}








Learn Easy way of calculating sin-cos-tan values.

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Posted at 02:42 | by viralnom

Thursday, 6 February 2014

Ethernet Standardization

Notwithstanding its technical merits, timely standardization was instrumental to the success of Ethernet. It

required well-coordinated and partly competitive activities in several standardization bodies such as the

IEEE, ECMA, IEC, and finally ISO.

The "DIX-group" with Gary Robinson (DEC), Phil Arst (Intel), and Bob Printis (Xerox) submitted the so-

called "Blue Book" CSMA/CD specification as a candidate for the LAN specification. Since IEEE

membership is open to all professionals, including students, the group received countless comments on this

technology.

Networks

Simple switched Ethernet networks, while a great improvement over repeater-based Ethernet, suffer from

single points of failure, attacks that trick switches or hosts into sending data to a machine even if it is not

intended for it, scalability and security issues with regard to broadcast radiation and multicast traffic, and

bandwidth choke points where a lot of traffic is forced down a single link.

Advanced networking features in switches and routers combat these issues through a number of means

including spanning-tree protocol to maintain the active links of the network as a tree while allowing physical

loops for redundancy, port security and protection features such as MAC lock down and broadcast

radiation filtering, virtual LANs to keep different classes of users separate while using the same physical

infrastructure, multi-layer switching to route between different classes and link aggregation to add bandwidth

to overloaded links and to provide some measure of redundancy.

Standards

The vast majority of customer has LAN's that employ Ethernet as the network protocol - a few uses Token

Ring. At least 90% of these networks are 10 BASE-T. The LAN sits behind the router and hub or high-

speed Ethernet switch, and the workstations are connected in a star topology. Actually, most networks

have replaced the Cat 3 cables with Cat 5. Both Cat 3 and 5 cables have 4 un-shielded, twisted pairs of

copper wires and use the RJ-45 connector, as shown below:

Comparison

Often referred to as Thick net, 10Base5 was the first incarnation of Ethernet technology. The industry used

thick net in the 1980s until 10Base2 Thin net appeared. Compared to thick net, thin net offered the

advantage of thinner (5 millimeters vs. 10 millimeters) and more flexible cabling, making it easier to wire

office buildings for Ethernet.

The most common form of traditional Ethernet, however, is 10Base-T. 10Base-T offers better electrical

properties than thick net or Thin net, because 10Base-T cables utilize unshielded twisted pair (UTP) wiring

rather than coaxial. 10Base-T also proved more cost effective than alternatives like fiber optic cabling.

The table below details these traditional Ethernet technologies. Besides the type of cable involved, another

important aspect of Ethernet networking is the segment length. A segment is a network connection made by

a single unbroken network cable. Ethernet cables and segments can only span a limited physical distance,

after which transmissions will likely fail due to line noise, reduced signal strength and other degradation. Per

the Ethernet specifications, manufacturers of Ethernet equipment must meet the below minimum

specifications for segment length.

Numerous other lesser-known Ethernet standards exist, including 10Base-FL, 10Base-FB, and 10Base-

FP for fiber optic networks and 10Broad36 for broadband (cable television) cabling.

Gigabit Ethernet

Whereas Fast Ethernet improved traditional Ethernet from 10 Megabit to 100 Megabit speed, Gigabit

Ethernet boasts the same order-of-magnitude improvement over Fast Ethernet by offering speeds of 1000

Megabits (1 Gigabit). Gigabit Ethernet was first made to travel over optical and copper cabling, but the

1000Base-T standard successfully supports it as well. 1000Base-T uses Category 5 cabling similar to 100

Mbps Ethernet, although achieving gigabit speed requires the use of additional wire pairs.

100BASE-FX:

100BASE-FX is a version of Fast Ethernet over optical fiber. It uses a 1300 nm near-infrared (NIR) light

wavelength transmitted via two strands of optical fiber, one for receive (RX) and the other for transmit (TX).

Maximum length is 400 meters (1,310 ft.) for half-duplex connections (to ensure collisions are detected),

and 2 kilometres (6,600 ft) for full-duplex over multi-mode optical fiber. 100BASE-FX uses the same

4B5B encoding and NRZI line code that 100BASE-TX does. 100BASE-FX should use SC, ST, LC,

MTRJ or MIC connectors with SC being the preferred option.

100BASE-FX is not compatible with 10BASE-FL, the 10 MBit/s versions over optical fiber.

100BASE-SX:

100BASE-SX is a version of Fast Ethernet over optical fiber. It uses two strands of multi-mode optical

fiber for receive and transmit. It is a lower cost alternative to using 100BASE-FX, because it uses short

wavelength optics which are significantly less expensive than the long wavelength optics used in 100BASE-

FX. 100BASE-SX can operate at distances up to 550 meters (1,800 ft.).

100BASE-SX uses the same wavelength as 10BASE-FL, the 10 Mbit/s versions over optical fiber. Unlike

100BASE-FX, this allows 100BASE-SX to be backwards-compatible with 10BASE-FL.

Because of the shorter wavelength used (850 nm) and the shorter distance it can support, 100BASE-SX

uses less expensive optical components (LEDs instead of lasers) which makes it an attractive option for

those upgrading from 10BASE-FL and those who do not require long distances.

Ethernet Standardization