This lesson was primarily about Media (cabling etc)
So here we go, there are quite a few definitions to follow:
• Copper Media
o This is a bounded type of meida which uses on or more copper conductors with a non conductive covering or sheath which insulates it. eg. twisted pair and coax
• Twisted Pair Cable
o Type of copper cable with colour coded wires which are twisted around each other and the have a protective cladding over them (the tighter the twist the better the shielding)
There are clour schemes attached to these twisted pairs, this is explained below:
Primary Secondary
1. White/Blue Blue/White
2. White/Orange Orange/White
3. White/Green Green /White
4. White/Brown Brown/White
• UTP versus STP
Twisted pair cable can be shielded (STP) or un-shielded (UTP) - this type of cable is available in 2 pair, 6 pair, 25 pair and 100 pair.
• UTP - this typically does not include shielding around the conductors adn usually has 4 pairs of stranded or solid conductors (copper). It is relatively inexpensive and reliable.
• STP - This includes shielding and is typically wrapped in foil wrapper is surrounding the conductors which decreases interference and noise on the line. typically also contains 4 pairs and can support distances upto 100 metres.
• To connect two Peers together (computers) you would use a cross-over cable. This eliminates the switch or if there is no uplink and downlink available on the switch.
The cable categories are as follows:
Twisted Pair Connecotrs:
Twisted pair cables always use a connector called a RJ45 - this is a 8 pin connector used for networking connections. See the image below for connections:
RJ11 Connector:
• This is a connector used for Category 1 cable which is typically used for telephone systems.
COAX Cable:
• Coaxial Cable or coax is a copper cable which has a central core made of copper which is conductive adn is covered by a shield (non-conductive) and then a braiding or foild cover surrounding it. The diaelectric insulator separated the conductor and the shield. The signal is transported in the central copper core.
Coax Cable connectors and cable types:
• RG58/U - 5mm coax cable with solid core and 50 ohms impedance, used for ethernet networking. (could also use stranded core)
• RG8 - 10mm with stranded core adn 50 ohms impedance, used for ethernet networking
• RG9 - 10mm with stranded core adn 51 ohms impedance used for television adn transmission cable modems
• RG62 - 5mm with solid core adn 93 ohms impedance, used for ARCNET networking
• RG59 - 6mm with 75 ohms impedance used for low power video connections.
• RG6 - this is the same as RG59 but is preferred.
Connectors:
• BNC (Bayone-Neill-Concelman)
o T-Connector
o Barrel Connector
o Terminator
Coax cables typically require a termination to prevent signal reflections at the end of the cable.
ThinNet
• ThinNet is the name given to ehternet networking over RG58/U or RG58A/U cabling adn is wired in a bus configuration with segments no longer the 185m.
ThickNet
• This is the name given to Ethernet NEtworking over RG8 cabling, this is not commonly used and the segments can be up to 500m
• Networking devices are not connected directly to ThickNet cables and are typically connected using vampire clamps. ThickNet segments must be terminated with a 50 Ohms terminator.
Fiber Optic Cable:
• In this the core is made up of 1 or more glass/plastic cores which is between 5 and 100 microns thick.
• Light is transmitted through the core adn reflected at various frequencies to transport data.
Fiber Optic Cable Modes:
• Single Mode Fiber:
o Carries a single optic signal (usually in the infrared spectrum)
• Step-index multimode fiber:
o Contains a core with cladding each with its own unique form index of refraction.
o When light from the core enteres the cladding a "step down" occurs due to the difference in the refractive indices. Step-index fiber uses the total internal reflection to trap light.
• Graded index multimode fiber:
o Has variations in the core glass to compensate for mode path lenght deifferences - provides more bandwith thean Step-index.
Fiber Optic Connectors:
Cable Type Properties:
10Mbps Networking
Standard Cable Type Segment Length Connector Topology IEEE Standard
10Base2 Thin Coaxial 185 meters BNC Physical bus 803.2a
10BaseT Category 3, 4, 5 twisted pair 100 meters RJ-45 Physical star
10BaseFL Fiber-optic 2000 meters SC/ST Physical star
Notes on 10Base2
- 10Base2 networks follow the 5-4-3 rule whereby there is a maximum of 5 network segments allowed, using a maximum of 4 repeaters. Only 3 of the 5 permitted segments may be populated.
Notes on 10BaseT
10BaseT networks follow the 5-4-5 rule whereby there is a maximum of 5 network segments allowed, using a maximum of 4 repeaters. All 5 segments may be populated with nodes.
Fast Ethernet Networking
Fast Ethernet defines a group of standards for networking speed of 100 Mbps
Standard Cable Type Segment Length Connector Topology IEEE Standard
100BaseTX Category 5 UTP 100 meters RJ-45 Physical Star 802.3u
100BaseT4 Category 3, 4, 5 UTP 100 meters RJ-45 Physical Star 802.3u
100BaseFX Multimode Single-mode fiber-optic 412 meters / Multimode fiber
10000 meters / Single-mode fiber SC, ST Physical Star 802.3u
FDDI Fiber Optic /
Twisted Pair (CDDI) 2000 meters SC, ST Dual Ring ANSI FDDI
Gigabit Ethernet Networking
Standard Cable Type Segment Length Connector IEEE Standard
1000BaseLX Multimode/Single-mode fiber 550/multimode 5000/Single-mode Fiber connectors 802.3z
1000BaseSX Multimode fiber 550 meters with 50 micron multimode fiber Fiber connectors 802.3z
1000BaseCX Shielded Twisted Pair 25 meters 9-pin shielded connector
8-pin fiber channel type 2 connector 802.3z
1000BaseT UTP Category 5 75 meters 75 meters 802.3ab
10 Gigabit Ethernet
Standard Transmission Type Distance Cable type Connector IEEE Standard
10GBBaseSR Baseband 33m / 300m 50 micron / 62.5 micron multimode Fiber connectors 802.3ae
10GBBaseLR Baseband 10000 meters Single-mode fiber Fiber connectors 802.3ae
10GBBaseER Baseband 40000 meters Single-mode fiber Fiber connectors 802.3ae
Normal Ethernet Cables
A normal Ethernet cable is a straight-through cable, where the smaller cables inside the Ethernet cable on both ends will be in the same order of colours, from left to right. There are two standards in which the colours of the cables are arranged, they are; T-568A and T-568B. The variation in their colour order is not an indication of their performance, but just their standard. This type of cable is used to connect the computer to a hub or router to a switch.
Ethernet Cable Categories (Cat)
- Cat 3 - This category was widely used as a voice cabling format among computer network administrators in the 1990s. It is an unshielded twisted pair (UTP) that can carry up to 10 Mbit/s with a bandwidth performance of 16 MHz.
- Cat 4 - Cat 4 was mainly used in token ring networks and the cable consists of four unshielded twisted-pair (UTP) wires, with a data rate of 16 Mbit/s, and performance of up to 20 MHz.
- Cat 5 - This is a twisted pair high signal integrity cable that has three twists per inch of each twisted pair of 24 gouge copper wires within the cables. Cat 5 is used for 10/100Mb Ethernet and as a voice cabling format.
- Cat 5e - This category is an enhanced version of Cat 5 that prevents interference between one unshielded twisted pair to another twisted pair running in parallel within the same cable (Far End Crosstalk – FEXT). It works for 10/100Mb and 1000Mb Ethernet.
- Cat 6 - It is very similar to Cat 5e and is a cable standard for Gigabyte Ethernet (considered better than Cat 5e) and other network protocols that are backward compatible with the Cat 5/5e and Cat 3 cable standards. Cat 6 is made up of larger gouge wires, that work for 10/100/1000Mb Ethernet.
- Cat 7 - This cable type is a standard for Ethernet and other interconnect technologies, that are backward compatible with traditional Cat 5 and Cat 6 Ethernet cables. As it has more strict specifications for crosstalk and system noise than Cat 6 and Cat 5e, its cables and the wires within are completely shielded. The cable contains four twisted copper wire pairs and supports up to 600Mhz.
An Ethernet crossover cable is a type of Ethernet cable, that is used to connect computing devices together, without the use of a hub or switch. These cables have different pin points or plugs on each side. The wires within the Ethernet crossover cable can reverse the transmit and receive signals. Starting from the left, the 1st and 3rd wires and the 2nd and 6th wires are crossed, and can be seen through the RJ-45 connectors at each end of the crossover cable.
Ethernet cable types should be determined by your requirement, as there are many types and categories easily available all across the country. Ethernet cables are faster and take less processing from the CPU and other computer networking devices, which can save a lot of time during the transmission of data.
Other Cable Types:
• Serial Cable
o Type of bounded cable to connect two devices using serial transmission, this most often uses RS232 connector
• IEEE 1394 (FireWire)
o Not a common bounded media, it contains either 4 or 6 conductorss
• USB
o Connects multiple peripherals to a single port with high performance
Serial versus Parallel:
The difference is primarily the method data is transmitted, in parallel data is typically transmit as 8bits across several channels or wires simultaneously.
USB
The current standard is 2.0 It can communicate up to 480Mbs
Firewire versus USB
Original USB was slower than Firewire, but the 2.0 is as fast or better than Firewire except on throughput, thus firewire is still used for video.
Shielding
Plenum and PVC
PVC is plastic and burns - relatively inexpensive but fire can travel along it.
Plenum is not toxic/noxious and is also fire resistent.
UNBOUNDED Network Media
Wireless communication
Electromagnetic energy such as radio, microwave or light pulses, this enables users to move more freely whilst been connected.
Point to Point Broadcast
This would be from one point to another point - like from building to building. Often used in a CAN, MAN or WAN. It couvers wide areas over a short distance.
Radio Networking
A form of wireless communication where signals are sent via RF, electical interference and buildings
Broadcast Radio
A form of RF Networking that is non directional, uses a single frequency for transmission.
RADIO TYPES OF TRANSMISSION:
• Spread Spectrum Radio (this is like SABC, sent over various channels)
o The signal is sent over more than one frequency - because the signal is split over various frequency it is more difficult to eavesdrop
• Frequency Hopping Spread Spectrum (this is like MNet)
o A signal is sent on one channel at a time; at predetermined intervals the frequency is changed. The sender and receiver use the same frequency at the same intervals to receive the information.
• Direct Sequence Spread Spectrum (DSSS)
o Uses multiple channels simultaneously to send data.
o Additionally error detection and correction techniques are used to reduce data transmission errors.
o In DSSS a single data signal is converted into multiple digital data signals called chips. The chips are sent across a wide band of adjacent channels.
• Infrared Transmission
o A form of wireless transmission over unbounded media of which signals are sent via pulses of infrared light.
o This is purely line of site, but can be reflected of surfaces.
o Infrared supports transmission rates of 10Mbs to 16Mbs
• Microwave Transmission
o This is a form of point-to-point transmission (wireless) over unbounded media where signals are sent via pulses of electromagnetic energy in the microwave region.
o Microwave must have an unobstructed view of the transceivers
Noise Control
The flow of network communications can be impaired by interference such as noise.
• Electrical noise
o Unwanted noise introduced to the network media
• Sources of Electrical Noise
o Ambient noise
Can come from many sources such as solar disturbances which affect the earth’s magnetosphere, nearby radio broadcast towers. Longer segments are more affected then shorter ones.
o Power wires
Nearby high tension wires or the buildings power cables can cause electrical noise. Network cables which run parallel to power cables are more susceptible than those that run perpendicular.
o Electric Motors
Such as those in refrigerators, lifts create noise
o Electrical heat generating devices
Same as electrical motors which draw large amounts of power on start up.
o Fluorescent lighting and HID lights
Transformers and ballasts causes noise
Noise affects power is when motors etc start up they can cause fluctuations in the power stability causing peaks and troughs in the supply which can damage equipment.
Grounding
Grounding where a cable or pipe is in direct contact with the Earth can help in curbing noise by shunting the noise into the ground.
Grounding for safety, this is important to direct power sources away from humans and into the ground.
Isolated grounds – network equipment should have isolated grounds and not common ground like a pipe. These types of grounded plug points are often orange in colour.
Shielding
Shielding is the grounded conductive material placed around the data media to block the introduction of noise into the media. The connection between the ground and the shield is called the drain and are drained in only one place to prevent a ground loop, a phenomenon where shield generates noise in the data signal.
Noise Control with Twisted Pair
• Simple, the more twists the better, the less interference or noise. This is because the tighter the twist the less surface area of the core is exposed to the air.
• Termination will also assist in the combating of noise as the signal is terminated and does not bounce around!
This is very much part of lesson 7
Network Connectivity devices:
• Network Interface Cards (NICs)
o This is also sometimes called a NAC – Network Adapter Card
o This is a transceiver (sends and receives)
o The NIC serves as the go-between between the computers data bus and the network.
o You must have a NIC to connect to a network.
• Network card busses:
o ISA – industry standard adapter (8Mbs)
o EISA – Extended industry standards adapter (16Mbs)
o PCI – 32Mbs and up
• Installing a NIC into is not that important but is on page 125 of the first text book.
Transceivers
This is a device which both sends and receives data
Repeaters
The repeater is a device which regenerates the signal to improve signal (like an amplifier) with repeaters you can stretch segments further. (Remember when you amplify the signal you also amplify any noise!)
The 5-4-3 rule fits in here but was explained earlier in this blog! As a recap:
There is a limit as to how many repeaters one can add before timing problems occur. Basically: five segments, four repeaters, three usable of populated segments.
When using HUBs the 5-4-3 rule is important, with switches you can ignore the rule!
Hubs
(The hub functions on the physical layer)
This is a networking device used to connect nodes in the physical star topology into the logical bus topology.
A good question in the exam is to explain the difference between a passive and active hub!
Managed Hub
This is a hub which includes functions that enable you to monitor and configure operation. Typically you would connect to the hub using special software; they are sometimes also called ‘intelligent hubs”
Switching Hub
This is now called a switch! This hub reads the destination address to the packed and directs it to the correct port. Switching hubs can be slower as they must process each packet. They support load balancing
Hub Speeds
Hubs support transmission speeds of 10Mbps and 100Mbps although they are typically auto sensing hubs which provide either transmission speed.
Should one PC have a 100Mbps network card installed and another a 10Mbps network card, the hub will sense this and the network will run at 10Mbps to accommodate the slower network card.
Switches
Next time!
