Cabling and TopologyCabling and Topology

Chapter 3

ObjectivesObjectives

• Explain the different types of network topologies

• Describe the different types of network cabling

• Describe the IEEE networking standards

OverviewOverview

Three Parts to Chapter 3Three Parts to Chapter 3

• Network Topology• Most common standardized cable types• IEEE Committees for network technology

standards

TopologyTopology

• Network topology – The way that cables and other pieces of

hardware connect to one another

• Bus topology– Single bus cable– Connects all computer in a line

• Ring topology– Central ring of cable– Connects all computers in a ring

Bus and RingBus and Ring

Figure 3.1 Bus and ring topologies

Figure 3.2 Real-world bus topology

• Data flow– Bus topology

• Data flows from each computer onto the bus• Termination required at ends to prevent data reflection

– Ring Topology• Data flows from one computer to next one in circle• No end of cable and no need for termination

Figure 3.3 Terminated bus topology

Figure 3.4 Ring topology moving in a certain direction

• Problem with Bus and Ring– Entire network stops working if the cable is

broken at any point.

Figure 3.5 Nobody is talking!

• Star topology has a central connection for all computers

• Fault tolerance – benefit over bus and ring• Was not successful early on

– More expensive than bus and ring– Difficult to redesign early bus and ring hardware

StarStar

Figure 3.6 Star topology

• Hybrid topology combines topologies– Physical topology

• How cables physically look– Signaling topology

• How the signals travel electronically

HybridsHybrids

• Star-ring topology– Physical star + signaling ring– Ring shrunk down into a hub-like box– Cables connect to the hub

• Star-bus topology– Physical star + signaling bus– Segment (bus) shrunk down into a hub-like

box– Cables connect to the hub

Figure 3.7 Shrinking the ring

Figure 3.8 Shrinking the segment

• Mesh topology– Every computer connects to every other computer via

two or more routes

• Two types of mesh topology– Partially-meshed topology

• At least two machines have redundant connections– Fully-meshed topology

• Every computer connects directly to every other computer

• Most fault tolerant

Mesh and Point-to-MultipointMesh and Point-to-Multipoint

Figure 3.9 Mesh and point-to-multipoint

Figure 3.10 Partially- and fully-meshed topologies

• Point-to-multipoint topology– A single system is a common source

Figure 3.11 Comparing star and point-to-multipoint

• Two computers connect directly

• No need for a central hub

• Wired or wireless

Point-to-PointPoint-to-Point

Figure 3.12 Point-to-Point

• Topology is only one feature of a network• Other network features

– What is the cable made of?– How long can it be?– How do machines decide which machine should

send data and when?

Parameters of a TopologyParameters of a Topology

• Network technology– A practical application of a topology, and other

technologies that comprise a network– Examples

• 10BaseT• 1000BaseF• 10GBaseLX

CablingCabling

• A central conductor wire• Surrounded by an insulating material• Surrounded by a braided metal shield

Coaxial CableCoaxial Cable

Figure 3.13 Cutaway view of coaxial cable

• Outer mesh layer of coaxial cable– Shields transmissions from electromagnetic

interference (EMI)

Figure 3.14 Coaxial cable showing braided metal shielding

• Coaxial connectors in older networks– Bayonet-style BNC Connectors– Vampire taps pierced the cable

Figure 3.15 BNC connector on coaxial cable

• Connecting cable modems– F-type screw-on connector

Figure 3.16 F-type connector on coaxial cable

• RG rating for coaxial cable– Developed by military– RG-6 is predominate cable today– RG-59 cable is rarely used

Figure 3.17 RG-6 cable

• Coaxial cable Ohm rating– Relative measure of resistance – RG-6 and RG-59 are rated at 75 Ohms

Figure 3.18 Ohm rating (on an older RG-58 cable used for networking)

• Splitting coaxial cable

Figure 3.19 Coaxial splitter

• Extending coaxial cable

Figure 3.20 Barrel connector

• Most common network cabling• Twisted pairs of cables, bundled together• Twists reduce crosstalk interference

Twisted PairTwisted Pair

• Shielding protects from electromagnetic interference (EMI)

• Needed in locations with excessive EMI• Most common is IBM Type 1 cable

Shielded Twisted Pair (STP)Shielded Twisted Pair (STP)

Figure 3.21 Shielded twisted pair

• Most common• Twisted pairs of wires with plastic jacket• Cheaper than STP• Also used in telephone systems

Unshielded Twisted Pair (UTP)Unshielded Twisted Pair (UTP)

Figure 3.22 Unshielded twisted pair

• Category (CAT) ratings are grades of cable ratings

• Rated in MHz• Most common categories are in Table 3.1

CAT RatingsCAT Ratings

CAT Ratings for UTP

CAT MaxRating Frequency Max Bandwidth

Status with TIA/EIA

CAT1 <1 MHz Analog phone lines only No longer recognized

CAT2 4 MHz 4 Mbps No longer recognized

CAT3 16 MHz 16 Mbps Recognized

CAT4 20 MHz 20 Mbps No longer recognized

CAT5 100 MHz 100 Mbps No Longer recognized

CAT5e 100 MHz 1000 Mbps Recognized

CAT 6 250 MHz 10000 Mbps Recognized

Table 3.1

• Bandwidth is the maximum amount of data that will go through a cable per second

• 100 MHz originally translated to 100 Mbps• With bandwidth-efficient encoding

– CAT 5e at 100 MHz = 1,000 Mbps max bandwidth– CAT 6 at 250 MHz = 10,000 Mbps

UTP BandwidthUTP Bandwidth

• Look on the box

Using the Correct CableUsing the Correct Cable

Figure 3.23 CAT level marked on box of UTP

CAT level

• Look on the cable

Using the Correct CableUsing the Correct Cable

Figure 3.24 CAT level on UTP

CAT level

• RJ-11 (two pairs of wires) for telephones• RJ-45 (four pairs of wires) for networks

Register jack (RJ) connectorsRegister jack (RJ) connectors

Figure 3.25 RJ-11 (top) and RJ-45 (bottom) connectors

• Fiber-optic cable transmits light• Not affected by EMI• Excellent for long-distance transmissions

– Single copper cable works up to a few hundred meters

– Single fiber-optic cable works up to tens of kilometers

Fiber-OpticFiber-Optic

• Core: the glass fiber• Cladding: reflects signal down the fiber• Buffer: gives strength• Insulating jacket: protects inner components

Composition of Fiber-OpticComposition of Fiber-Optic

Figure 3.26 Cross section of fiber-optic cabling

• Two-number designator– Core and cladding measurements– 62.5/125 μm

Standardization of Fiber-OpticStandardization of Fiber-Optic

• One for sending• One for receiving • Cable may be connected together like a lamp

cord

Often used in cable pairsOften used in cable pairs

Figure 3.27 Duplex fiber-optic cabling

• Two possible light sources– Light Emitting Diodes (LEDs) – called multimode

• Usually 850 nm wavelength– Lasers – called single-mode

• Prevents modal distortion (a problem with multimode)• High transfer rates over long distances• 1310 or 1550 nm wavelength

Fiber-Optic Light SourcesFiber-Optic Light Sources

• ST: bayonet-style• SC: push-in• LC: duplex

Fiber-Optic connectorsFiber-Optic connectors

Figure 3.28 From left to right: ST, SC, and LC fiber-optic connectors

• Classic Serial– RS-232 recommended standard (RS)

• Dates from 1969• Has not changed significantly in 40 years• Usually 850 nm wavelength

– Most common serial port is 9-pin, male D-subminiature connector

– Slow data rates: about 56,000 bps– Only point-to-point connections

Other CablesOther Cables

Figure 3.29 Serial port

Serial port

• Parallel– Up to 2 Mbps– Limited to point-to-point– IEEE 1284 committee sets standards

Figure 3.30 Parallel connector

• FireWire– IEEE 1394 standard– Limited to point-to-point– Very fast – up to 800 Mbps– Unique connector

Figure 3.31 FireWire connector

• Underwriters Laboratories and the National Electrical Code (NEC)– Polyvinyl chloride (PVC) rating has no

significant fire protection• Lots of smoke and fumes

– Plenum-rated cable• Less smoke and fumes• Costs three to five times as much as PVC-rated cable

– Riser-rated cable for vertical runs

Cable Fire RatingsCable Fire Ratings

Networking Industry Networking Industry Standards Standards – IEEE– IEEE

• Institute of Electrical and Electronics Engineers (IEEE) defines standards– 802 Working Group began in February of 1980

• Defines frames, speed, distances, and types of cabling for networks

• IEEE 1284 committee sets standards for parallel communications

Figure 3.32 Parallel cable marked IEEE 1284–compliant

IEEE 802 Subcommittees

IEEE 802 LAN/MAN Overview & ArchitectureIEEE 802.1 Higher Layer LAN Protocols

802.1s Multiple Spanning Trees802.1w Rapid Reconfiguration of Spanning Tree802.1x Port Based Network Access Control

IEEE 802.2 Logical Link Control (LLC); now inactiveIEEE 802.3 Ethernet

802.3ae 10 Gigabit EthernetIEEE 802.5 Token Ring;; now inactiveIEEE 802.11 Wireless LAN (WLAN); specifications, such as Wi-FiIEEE 802.15 Wireless Personal Area Network (WPAN)IEEE 802.16 Broadband Wireless Access (BWA); specification for implementing Wireless

Metropolitan Area Network (Wireless MAN); referred to also as WiMax

IEEE 802.17 Resilient Packet Ring (RPR)IEEE 802.18 Radio Regulatory Technical Advisory GroupIEEE 802.19 Coexistence Technical Advisory GroupIEEE 802.20 Mobile Broadband Wireless Access (MBWA)IEEE 802.21 Media Independent HandoverIEEE 802.22 Wireless Regional Area Networks

Table 3.2