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Chapter 4: Connecting Through a Cabled Network

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1 Chapter 4: Connecting Through a Cabled Network

2 Communications Media Types
OSI Layer 1: communication media and interfaces Five basic communication media types Coaxial cable: based on copper wire Twisted-pair cable: based on copper wire Fiber-optic cable: glass or plastic cable Hybrid fiber/coax: combines copper and fiber Wireless technologies: radio or microwaves The suitability of media varies with different networks Example: uses of coaxial cable Older LANs LANs in areas with signal interference strong Connecting wireless antenna to network device

3 Communications Media Types
When choosing the best medium for a LAN or WAN consider capabilities and limitations of media Factors affecting the choice of LAN or WAN medium Data transfer speed Use in specific network topologies Distance requirements Cable and cable component costs Additional network equipment that might be required Flexibility and ease of installation Immunity to interference from outside sources Upgrade options Security

4 Communications Media Types
Backbone cabling: cable that runs between network equipment rooms, floors, and buildings and is often used to connect network devices Plenum cable: Teflon-coated cable that does not emit a toxic vapor when burned Used in locations such as a false ceiling through which circulating air reaches other parts of a building Impedance: total amount of opposition to the flow of current and is measured in ohms

5 Coaxial Cable Coaxial cable was the first media type defined with Ethernet standards (early 1980s) Two types of coaxial cable (coax) Thick: used in early networks, typically as backbone Thin: used to connect desktops to LANs Has much smaller diameter than thick coax Use of both thick and thin coaxial cables declining

6 Thick Coax Cable Thick coax cable (thickwire, thicknet, RG-8)
Has relatively large .4-inch diameter Copper or copper-clad aluminum conductor at core Conductor surrounded by insulation Aluminum sleeve wrapped around insulation PVC or Teflon jacket covers aluminum sleeve The cable jacket is marked every 2.5 m to show where a network-connecting device can be attached If devices are attached more closely than 2.5 meters, the signal can be impaired and errors may occur Hands-on Networking Fundamentals

7 Figure 4-1 Thick coax (RG-8) cable
Hands-on Networking Fundamentals

8 Thick Coax Cable Media access unit (MAU) transceiver
Connecting device driven by small current (.5 amps) Has 15-pin attachment unit interface (AUI) connector AUI connects via cable to network cable Thick AUI cable up to 50 meters long Impedance of thick coax cable is 50 ohms Maximum cable segment length is 500 meters 10Base5 10 = the cable transmission rate is 10 Mbps Base = that baseband transmission is used 5 = 500 meters for the longest cable run Hands-on Networking Fundamentals

9 Figure 4-2 Connecting to thick coax cable
Hands-on Networking Fundamentals

10 Table 4-1 Thick coax cable (10Base5) properties for Ethernet applications
Hands-on Networking Fundamentals

11 Thin Coax Cable Ethernet specifications for thin coax cable
50 ohms of impedance (RG-58A/U or Radio Grade 58) Meets criteria in 10Base2 designation Maximum theoretical speed of 10Mbps Wire runs up to 185 meters (formerly 200) Used for baseband (Base) data transmission Thin coax has a smaller diameter than thick coax (.2") Implementing thin coax cable: Cable is attached to a bayonet nut connector (BNC) BNC is connected to a T-connector Middle of T-connector is attached to a NIC Terminator may be attached to one end of a T-connector Hands-on Networking Fundamentals

12 Figure 4-3 A BNC T-connector with a terminator at one end
Hands-on Networking Fundamentals

13 Thin Coax Cable Advantages of thin coax cable
Easier and cheaper to install than thick coax More resistant to EMI and RFI (interferences) than twisted pair Coax is still found on some legacy networks and in places subject to very high EMI/RFI Hands-on Networking Fundamentals

14 Table 4-2 Thin coax cable (10Base2) properties for Ethernet applications
Hands-on Networking Fundamentals

15 Twisted Pair Cable Twisted-pair cable
Contains pairs of insulated copper wires Outer insulating jacket covers wires Communication specific properties Copper wires twisted to reduce EMI and RFI Length: up to 100 meters Transmission speed: up to 10 Gbps RJ-45 plug-in connector attaches cable to device Less expensive and more flexible than T-connectors Two kinds of twisted pair cable: shielded and unshielded (preferred) Hands-on Networking Fundamentals

16 Figure 4-4 Twisted-pair cable with an RJ-45 plug-in connector
Hands-on Networking Fundamentals

17 Shielded Twisted Pair Cable
Shielded Twisted Pair Cable (STP) Surrounded by braided or corrugated shielding Shielding reduces interference due to EMI and RFI Further reducing impact of EMI and RFI Interval of twists (lay length) in each pair should differ Connectors and wall outlets should be shielded Have proper grounding Use medium when strong interference sources nearby Example: heavy electrical equipment Shielded cable and associated equipment is more expensive than unshielded cable Hands-on Networking Fundamentals

18 Figure 4-5 STP and UTP cables
Hands-on Networking Fundamentals

19 Unshielded Twisted-Pair Cable
Unshielded Twisted-Pair Cable (UTP) Consists of wire pairs within insulated outer covering Has no shielding between wires and encasement UTP is the most frequently used network cable Reducing EMI and RFI Twist interior strands (like STP) Built-in media filter into network equipment, workstation, and file connection servers UTP cables used in 10BaseT networks Category 3: transmission rates up to 16 Mbps Category 4: transmission rates up to 20 Mbps Hands-on Networking Fundamentals

20 Unshielded Twisted-Pair Cable
Category 5 UTP has 100 Mbps transmission rate Category 5e (enhanced) UTP vs. Category 5 UTP 1 Gbps transmission rate Uses better-quality copper Has a higher twist ratio for better EMI/RFI protection Category 6 UTP Wire pairs are wrapped within insulating foil Has fire resistant plastic sheath Category 7 UTP Extremely resistant to EMI/RFI but it requires special connectors and is not as flexible Hands-on Networking Fundamentals

21 Table 4-3 Ethernet twisted-pair cable standards
Table 4-3 Ethernet twisted-pair cable standards Hands-on Networking Fundamentals

22 Unshielded Twisted-Pair Cable
Reasons for preferring UTP over STP Fewer points of failure Has no shield that can tear (up through Category 5e) Connectors and wall outlets do not need shielding Proper grounding not as critical to purity of signal Horizontal cabling (defined by EIA/TIA-568 standard) Cabling connecting workstations/servers in work area Implemented with Categories 5e, 6, and 6e UTPs Hands-on Networking Fundamentals

23 Table 4-4 10BaseT (and in general 100BaseX) unshielded
twisted-pair Ethernet specifications Hands-on Networking Fundamentals

24 Table 4-5 10BaseT (and in general 100BaseX) shielded
twisted-pair Ethernet specifications Hands-on Networking Fundamentals

25 Figure 4-7 Twisted-pair cable connected to an RJ-45 connector
Hands-on Networking Fundamentals

26 Fiber-Optic Cable Fiber-optic cable
One or more glass or plastic fiber cores encased in glass tube (cladding) Fiber cores and cladding are surrounded by PVC cover Signal transmissions consist of light (usually infrared) Three commonly used fiber-optic cable sizes 50/125 micron Micron (μm): millionth of a meter 50 represents core diameter 125 represents cladding diameter 62.5/125 micron 100/140 micron Hands-on Networking Fundamentals

27 Figure 4-9 Fiber-optic cable
Hands-on Networking Fundamentals

28 Fiber-Optic Cable Uses of fiber-optic cables Cable-plant backbones
Fat pipe: high bandwidth backbone between floors Connect different buildings in campus environment Joining spread-out LANs into a WAN Advantages of fiber-optic cables Each cable type has multimode transmission capacity Transmission speeds from 100 Mbps - over 100 Gbps No EMI or RFI problems, data travels by light pulse Low attenuation (attenuation: signal loss during travel) Secure from unauthorized taps Hands-on Networking Fundamentals

29 Fiber-Optic Cable Disadvantages of fiber-optic cables Fragile
More expensive than UTP Requires specialized training to install Basic characteristics of light transmission Light wavelength is measured in nanometers (nm) Infrared light travels in the range of nm Three ideal wavelengths (windows): 850 nm, 1300 nm, 1550 nm High-speed transmission typically use the 1300 nm window Hands-on Networking Fundamentals

30 Fiber-Optic Cable Fiber-optic cable comes in two modes
Single-mode: used for long-distance communication 8-10/125 micron cable transmits one wave at a time Communications signal is laser light Multimode: supports multiple waves (broadband) Comes in two varieties: step index and graded index Cable diameter between 50 and 115 microns Source for multimode cable is light-emitting diode (LED) Three connector types used with fiber-optic cables Subscriber connector (SC) Straight tip (ST) MTRJ Hands-on Networking Fundamentals

31 Table 4-6 EIA/TIA-568-B specifications for single-mode
fiber-optic cable in a cable-plant backbone Hands-on Networking Fundamentals

32 Table 4-7 EIA/TIA-568-B specification for multimode
fiber-optic cable in a cable-plant backbone Hands-on Networking Fundamentals

33 Hybrid Fiber/Coax Cables
Hybrid fiber/coax (HFC) cable Single sheath containing fibers and copper cables Different combinations for different implementations How HFC cables improve cable networks Increase upstream bandwidth and reduce noise HFC drawbacks: expensive and not fully installed Services possible using HFC cables Plain old telephone service (POTS) Over 200 digital TV channels Over 400 digital point channels High-speed, two-way digital data link for PCs Hands-on Networking Fundamentals

34 High-speed Technologies For Twisted-Pair And Fiber-Optic Cable
High-speed threshold: 10 Mbps Three technologies enhancing cables for high-speed Fast Ethernet Gigabit Ethernet 10 Gigabit Ethernet 40 and 100 Gigabit Ethernet Hands-on Networking Fundamentals

35 Fast Ethernet Fast Ethernet: 100 Mbps data transfer over twisted-pair cable Two Fast Ethernet technologies 100BaseVG or 100VG-AnyLAN 100BaseX Hands-on Networking Fundamentals

36 The IEEE 802.3u Standard IEEE 802.3u (100BaseX): standard for Fast Ethernet Versions of 100BaseX: 100BaseT, 100BaseTX, 100BaseT4, 100BaseT2, 100BaseFX Common properties of standards (except 100BaseT2) All use CSMA/CD media access methods All propagate signal in more than one direction 100BaseT2 transmits signal in timed-delay manner Signal transmitted with twisted-pair or fiber-optic cable Limitations and restrictions Signal can only go through one Class I repeater or two Class II repeaters Hands-on Networking Fundamentals

37 The IEEE 802.3u Standard A Class I repeater introduces delays when performing the Fast Ethernet conversion For this reason, only one Class I repeater can be put in a single, Fast Ethernet LAN segment Class II repeaters have all ports of the same Fast Ethernet media type so there is no need for a conversion Very little delay is introduced by the quick movement of data For this reason, two Class II repeaters are allowed per Fast Ethernet segment Hands-on Networking Fundamentals

38 Table 4-8 100BaseX communication options
Hands-on Networking Fundamentals

39 The IEEE 802.12 Standard IEEE 802.12: (100BaseVG/100VG-AnyLAN)
Abandons CSMA/CD for demand priority Demand priority Ensures signal travels in one direction Used in star networks linked by a central switch Grants requests one by one Benefits of demand priority Enables packet travel up to 100 Mbps Security: packet visible only to receiving node Prioritizes multimedia and time sensitive transmissions Hands-on Networking Fundamentals

40 Figure 4-13 Using demand priority
Hands-on Networking Fundamentals

41 Gigabit Ethernet Gigabit Ethernet (1000BaseX)
Provides data transfer of up to 1 Gbps Uses CSMA/CD access methods Upgrade path for 100BaseX Ethernet networks Uses of Gigabit Ethernet Alternative for backbone LAN congestion Attract token ring users with star-based topologies Gigabit Ethernet target Installations using Layer 3 routed communications Separate standards for fiber-optic and twisted-pair cables Hands-on Networking Fundamentals

42 Table 4-9 Gigabit Ethernet specifications
Hands-on Networking Fundamentals

43 10 Gigabit Ethernet 10 Gigabit Ethernet or 10GBaseX
High-speed networking protocol Competes with other high-speed MANs and WANs Provides fast backbone networking in LANs True Ethernet with some differences Operates at full duplex (transmission in two directions) Does not need to employ CSMA/CD No packet collisions by design How to distinguish various standards By interfaces and transmission characteristics Hands-on Networking Fundamentals

44 40 and 100 Gigabit Ethernet 40 Gigabit (40GBaseX/40GBaseE) and 100 Gigabit (100GBaseX/100GBaseE) are relatively new high-speed Ethernet options Both are intended to serve two purposes: Enable faster computing services, such as through faster backbone speeds Provide faster communications for network aggregation points, such as links to servers and network storage Shared resources such as Internet Protocol television (IPTV) and streaming media require faster backbone speeds Hands-on Networking Fundamentals

45 40 and 100 Gigabit Ethernet Network aggregation – refers to central resources such as servers and network storage Gigabit Ethernet is intended to remove network transport bottlenecks surrounding these aggregated resources Table Gigabit Ethernet specifications Hands-on Networking Fundamentals

46 Table 4-12 100 Gigabit Ethernet specifications
Hands-on Networking Fundamentals

47 Connecting Computers to a Cabled Network
Network Interface Card (NIC) Enables node to connect to cabled network Matches transport methods, bus types, and media Network connection requires four components Appropriate connector for network medium Hardware and protocol control firmware and drivers Transceiver Controller to support MAC sublayer of Data Link layer Hands-on Networking Fundamentals

48 The NIC Connector Connector designed for specific medium type
Examples: twisted-pair, fiber-optic cable, wireless Older combination NICs have multiple connectors May be used with different media Newer combination NICs have single connector Select one among: 10BaseT, 100BaseX, 1000BaseTX Hands-on Networking Fundamentals

49 The Role of Firmware and NIC Drivers
Firmware and NIC driver support communications Firmware: software stored on a chip, such as ROM NIC Driver: manages how packets or frames sent Firmware or driver may automatically detect media Some NIC drivers can be signed Driver signing: placing digital signature in driver Functions of digital signature Ensures driver compatible with operating system Certifies that driver tested for defects or viruses Ensures that driver cannot overwrite new driver Hands-on Networking Fundamentals

50 Using a Transceiver Cable connector is attached to transceiver Transceiver: device that transmits and receives signals on a communications cable Transceiver may be internal or external to NIC Hands-on Networking Fundamentals

51 The Role of the MAC Controller Unit
MAC controller unit and firmware work together to encapsulate: Source and destination address information Data to be transported CRC error control information MAC Controller operates at two sublayers of Layer 2 MAC sublayer: formats frames LLC sublayer: initiates and maintains link between nodes and ensures the communications link is not broken and remains reliable after it is established Hands-on Networking Fundamentals

52 Half- and Full-Duplex NIC Communications
Two transmission modes for NIC and network equipment Half-duplex: cannot send and receive at the same time Full-duplex: can send and receive simultaneously Made possible by buffering at NIC Buffering: temporarily storing information Full-duplex is a good choice on networks Usually faster than half-duplex Hands-on Networking Fundamentals

53 Buses and NICs Bus: data pathway inside the computer
Common bus types (standards) Industry Standard Architecture (ISA) Extended Industry Standard Architecture (EISA) Microchannel Architecture (MCA) Peripheral Computer Interface (PCI) SPARC Bus (SBUS) Universal Serial Bus (USB) Hands-on Networking Fundamentals

54 Choosing a NIC Every NIC is critical for effective communication
Questions to consider when purchasing a NIC Is NIC for host computer, server, or workstation? What kind of throughput does the computer require? What network media and transport methods are in use? Who manufactures the NIC? What is the computer or network equipment bus type? What operating system is used by the computer? Are half-duplex or full-duplex communications used? If NIC is for a special application, how does it attach? Hands-on Networking Fundamentals

55 Designing a Cabled Network
Design choices applicable to most networks Use Ethernet as the transport method Use twisted pair to the desktop Employ fiber-optic cable for the backbone Connect servers to the network at 1 Gbps or 10 Gbps Use the best and fastest options within budget Scenario: small credit union in two story building Use star-bus hybrid topology Run 100BaseT to computers on both floors Fiber-optic cable run for backbone between floors Connect servers using 1000BaseTX or 10GBaseF Hands-on Networking Fundamentals

56 Figure 4-18 Designing a network for a small credit union
Hands-on Networking Fundamentals

57 Summary High-speed technologies for twisted-pair and fiber-optic cabling include Fast Ethernet, Gigabit Ethernet, 10 Gigabit Ethernet, 40 Gigabit Ethernet, and 100 Gigabit Ethernet NICs have an important role on networks because these devices connect computers and network devices to network cable. Important NIC components on a cabled network include a connector, firmware and drivers, a transceiver, and a MAC controller. Hands-on Networking Fundamentals

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