bài giảng mạng máy tính căn bản chương 3 môi trường truyền dẫn cho networking

Phan Vĩnh Thuần Computer Network 1 Chương 3: MÔI TRƯỜNG TRUYỀN DẪN CHO NETWORKING Overview • Copper cable is used in almost every LAN. Many different types of copper cable are available, with each type having advantages and disadvantages. Proper selection of cabling is key to efficient network operation. Phan Vĩnh Thuần Computer Network 2 • Optical fiber is the most frequently used medium for the longer, high bandwidth, point- to-point transmissions required on LAN backbones and on WANs. Using optical media, light is used to transmit data through thin glass or plastic fiber. Electrical signals cause a fiber-optic transmitter to generate the light signals sent down the fiber. The receiving host receives the light signals and converts them to electrical signals at the far end of the fiber. However, there is no electricity in the fiber- optic cable itself. In fact, the glass used in fiber-optic cable is a very good electrical insulator. Phan Vĩnh Thuần Computer Network 3 • Physical connectivity allowed an increase in productivity by allowing the sharing of printers, servers, and software. Traditional networked systems require that the workstation remains stationary permitting moves only within the limits of the media and office area. • The introduction of wireless technology removes these restraints and brings true portability to the computing world. Currently, wireless technology does not provide the high-speed transfers, security, or uptime reliability of cabled networks. However, flexibility of wireless has justified the trade off. Phan Vĩnh Thuần Computer Network 4 • Administrators often consider wireless when installing a new network or when upgrading an existing network. A simple wireless network could be working just a few minutes after the workstations are turned on. Connectivity to the Internet is provided through a wired connection, router, cable or DSL modem and a wireless access point that acts as a hub for the wireless nodes. In a residential or small office environment these devices may be combined into a single unit Phan Vĩnh Thuần Computer Network 5 • Students completing this module should be able to: – Describe the specifications and performances of different types of cable. – Describe coaxial cable and its advantages and disadvantages over other types of cable. – Describe shielded twisted-pair (STP) cable and its uses. – Describe unshielded twisted-pair cable (UTP) and its uses. Phan Vĩnh Thuần Computer Network 6 – Discuss the characteristics of straight- through, crossover, and rollover cables and where each is used. – Explain the basics of fiber-optic cable. – Describe how fibers can guide light for long distances. – Describe multimode and single-mode fiber. – Describe the type of connectors and equipment used with fiber-optic cable. Phan Vĩnh Thuần Computer Network 7 3.1. Đường truyền cáp đồng 3.1.1. Các đặc tả cáp Cables have different specifications and expectations pertaining to performance: Phan Vĩnh Thuần Computer Network 8 • What speeds for data transmission can be achieved using a particular type of cable? The speed of bit transmission through the cable is extremely important. The speed of transmission is affected by the kind of conduit used. • What kind of transmission is being considered? Will the transmissions be digital or will they be analog-based? Digital or baseband transmission and analog-based or broadband transmission are the two choices. Phan Vĩnh Thuần Computer Network 9 • How far can a signal travel through a particular type of cable before attenuation of that signal becomes a concern? In other words, will the signal become so degraded that the recipient device might not be able to accurately receive and interpret the signal by the time the signal reaches that device? The distance the signal travels through the cable directly affects attenuation of the signal. Degradation of the signal is directly related to the distance the signal travels and the type of cable used. Phan Vĩnh Thuần Computer Network 10 • Some examples of Ethernet specifications which relate to cable type include: – 10BASE-T – 10BASE5 – 10BASE2 • 10BASE-T refers to the speed of transmission at 10 Mbps. The type of transmission is baseband, or digitally interpreted. The T stands for twisted pair. [...]... Network 30 • Two switches are connected together The cable that connects from one switch port to another switch port is called a crossover cableComputer Network Phan Vĩnh Thuần 31 • The cable that connects the RJ-45 adapter on the com port of the computer to the console port of the router or switch is called a rollover cable Phan Vĩnh Thuần Computer Network 32 3. 2 Đường truyền cáp quang (Optical media) 3. 2.1... coaxial cable Connection problems result in electrical noise that interferes with signal transmittal on the networking media For this reason thinnet is no longer commonly used nor supported by latest standards (100 Mbps and higher) for Ethernet networks Phan Vĩnh Thuần Computer Network 20 3. 1 .3 Cáp STP (Shield Twisted-Pain) Phan Vĩnh Thuần Computer Network 21 • Shielded twisted-pair cable (STP) combines... form of waves can travel through a vacuum, the air, and through some materials like glass An important property of any energy wave is the wavelength Phan Vĩnh Thuần Computer Network 33 Phan Vĩnh Thuần Computer Network 34 • Radio, microwaves, radar, visible light, x-rays, and gamma rays seem to be very different things However, they are all types of electromagnetic energy If all the types of electromagnetic... disrupt the ability of the receiver to appropriately interpret the signal being received 10BASE2 is often referred to Computer Network as Thinnet Phan Vĩnh Thuần 12 Phan Vĩnh Thuần Computer Network 13 3.1.2 Cáp đồng trục (Coaxial cable ) Phan Vĩnh Thuần Computer Network 14 Phan Vĩnh Thuần Computer Network 15 • Coaxial cable consists of a hollow outer cylindrical conductor that surrounds a single inner... and interference than other types of networking media, and the distance between signal boosts is shorter for UTP than it is for coaxial and fiber optic cables • UTP was once considered slower at transmitting data than other types of cable This is no longer true In fact, today, UTP is considered the fastest copper-based media Phan Vĩnh Thuần Computer Network 28 3. 1.5 Kết nối cáp UTP When communication... electromagnetic waves are arranged in order from the longest wavelength down to the shortest wavelength, a continuum called the electromagnetic spectrum is created Phan Vĩnh Thuần Computer Network 35 Phan Vĩnh Thuần Computer Network 36 ... cable Thicknet cable is almost never used anymore, except for special purpose installations Phan Vĩnh Thuần Computer Network 18 • In the past, ‘thinnet’ coaxial cable with an outside diameter of only 0 .35 cm was used in Ethernet networks It was especially useful for cable installations that required the cable to make many twists and turns Since thinnet was easier to install, it was also cheaper to install... of unshielded twistedpair cable (UTP) STP affords greater protection from all types of external interference, but is more expensive and difficult to install than UTP Phan Vĩnh Thuần Computer Network 23 • A new hybrid of UTP with traditional STP is Screened UTP (ScTP), also known as Foil Twisted Pair (FTP) ScTP is essentially UTP wrapped in a metallic foil shield, or screen It is usually 100-Ohm or... electromagnetic waves from causing noise on data wires, but it also minimizes the outgoing radiated electromagnetic waves These waves could cause noise in other devices Phan Vĩnh Thuần Computer Network 24 3. 1.4 Cáp UTP (Unshield Twisted-Pair) Phan Vĩnh Thuần Computer Network 25 • Unshielded twisted-pair cable (UTP) is a fourpair wire medium used in a variety of networks Each of the 8 individual copper wires... twists or braids are permitted per foot of cable Phan Vĩnh Thuần Computer Network 26 • Unshielded twisted-pair cable has many advantages It is easy to install and is less expensive than other types of networking media In fact, UTP costs less per meter than any other type of LAN cabling However, the real advantage is the size Since it has such a small external diameter, UTP does not fill up wiring ducts . Phan Vĩnh Thuần Computer Network 1 Chương 3: MÔI TRƯỜNG TRUYỀN DẪN CHO NETWORKING Overview • Copper cable is used in almost every LAN. Many different. connectors and equipment used with fiber-optic cable. Phan Vĩnh Thuần Computer Network 7 3. 1. Đường truyền cáp đồng 3. 1.1. Các đặc tả cáp Cables have different specifications and expectations pertaining. received. 10BASE2 is often referred to as Thinnet Phan Vĩnh Thuần Computer Network 13 Phan Vĩnh Thuần Computer Network 14 3. 1.2. Cáp đồng trục (Coaxial cable ) Phan Vĩnh Thuần Computer Network 15 Phan