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Network cabling and devices

Unit objectives Discuss network communication methods Identify the characteristics and appropriate

implementation techniques of various types of cables and connectors

Discuss coaxial and fiber optic cables (and, of course, UTP – unshielded twisted pair, AKA CAT3, 5, 5e, 6, 6e, 7, etc.)

Discuss Ethernet and Token Ring devices

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More on Full Duplex Benefits

The bandwidth of a full-duplex communication is more than double that of half-duplex:– first, for example, if you have a 10Mbps

network, the bandwidth is 10 Mbps is each direction, or effectively, 20 Mbps.

– second, full-duplex only works with point-to-point links; i.e., you cannot, for example, implement CSMA/CD using full-duplex. The very nature of CSMA/CD suggests that every host listens and then only one host transmits.

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Full Duplex Benefits (continued) On a LAN, full-duplex is normally implemented

on a switch port; with a WAN, full-duplex, point-to-point connections normally end at router interfaces.

Because there are only two parties to a full-duplex communication, there are no collisions!

Without collisions, there is no retransmission of data, further speeding the transfer rate.

Finally, a host never has to wait for another host to finish transmitting before it can send! The further increases the “throughput”.

(Distinguish throughput – the actual rate of transmission, from bandwidth and also from goodput.

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Topic A

Topic A: Network communication methods

Topic B: Cables and connectors Topic C: Coaxial and fiber optic cables Topic D: Ethernet and Token Ring devices

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Baseband vs. broadband

The baseband transmission method uses the media in such a way that the entire capacity of the cable is taken up by a single transmission

In broadband communications the communicators use different frequencies to separate their messages from others by using the same media at the same time

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Data signals can be sent over a network cable in one of two ways: broadband or baseband.

Baseband signaling only sends a single signal over the cable. This type of signaling is typically used in Ethernet networks, (with the exception of 10Broad3 standard - rarely used). Baseband uses very simple transceiver devices that send and receive signals on a cable. The simplicity behind baseband signaling is that only three states need to be distinguished: one, zero and idle.

Broadband transceivers are much more complex because they must be able to distinguish those same states, but on multiple channels within the same cable. Because of its simplicity, baseband signaling is used on most Ethernet networks.

Baseband vs. broadband (cont)

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One way to look at the difference is based on the technology used. You can give someone 56k on a broadband service and give someone 11Mb on a Linksys WiFi router that is baseband networking! The distinctions are not always clear. – 56k - dialup - narrowband, this includes the so-called

compressed services that give you 300k downloads – 128k - ISDN - narrowband, also a glorified dialup – DSL, Cable, Fixed Wireless(PTMP) - Broadband, these are

carrier grade services offering anywhere from 56k - 5Mb.– WiFi – networking/baseband - While it is providing a fast

connection it is just resending the broadband it is given to be shared by all.

– T1, Fiber, P2P wireless – “Backhaul” - Not really broadband. Used to deliver connections from the internet to the broadband device or network. But it is broadband for test purposes; just remember all the frequency-hopping and switching in the various transmission methods.

Baseband vs. broadband (cont)

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Broadband in telecommunications refers to a signaling method that includes or handles a relatively wide range of frequencies, which may be divided into channels or frequency bins. Broadband is always a relative term, understood according to its context. The wider the bandwidth, the greater the information-carrying capacity.

For example, the FCC says 200 Kbps = broadband (even if in one direction!) Anything under that, however is not necessarily baseband; baseband is defined by the use of only one frequency. In terms of speed, though, <200K just isn’t fast enough to be labeled “broadband” – probably for consumer protection purposes

Baseband vs. broadband (cont)

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So what we are left with is:– 1. The use of multiple signals with a bandwidth

greater than 200 Kbps is broadband.– 2. The use of multiple signals with a bandwidth

less than 200 Kbps is “narrowband”. – 3. The use of a single frequency in a system

than provides any level of bandwidth is baseband.

– 4. “Backhaul / broadband” – where your connection is essentially a delivery mechanism for a broadband implementation.

Baseband vs. broadband (cont)

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Half-duplex vs. full-duplex

Half-duplex communications need that each participant only transmits when the other is listening

By using full-duplex communications, both parties can transmit simultaneously

The benefit of full-duplex mode is less delay in transmitting a message, because a computer could receive and transmit information simultaneously

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Throughput, Bandwidth, & Goodput

Bandwidth is the capacity for a given system to transfer data over a connection.

Throughput is the average rate of successful message delivery over a communication channel.

Goodput is the application level throughput, i.e. the number of useful bits per unit of time forwarded by the network from a certain source address to a certain destination, excluding protocol overhead, and excluding retransmitted data packets.

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Activity A-1 – (pg 5-3)

Discussing communication methods

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Topic B

Topic A: Network communication methods Topic B: Cables and connectors Topic C: Coaxial and fiber optic cables Topic D: Ethernet and Token Ring devices

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Twisted pair properties

Twisted pair is made of insulated copper wires that have been twisted around each other to form wire pairs

Twisted-pair cabling is divided into two categories– Unshielded Twisted Pair (UTP)– Shielded Twisted Pair (STP)

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Unshielded Twisted Pair (UTP)

UTP is a set of twisted pairs within a plastic sheath

The common use for this type of cable is telephone wiring and LAN communications

Two popular UTP cabling types are Category 3 (all but obsolete) and Category 5 UTP (AKA “CAT5” and “CAT3”).

Newer types include Category 5e and Category 6 (5e is no longer “new”; it is the defacto standard for new network installations, per the TIA/EIA. The TIA is the Telecommunications Industry Association and the EIA is the Electronic Industries Association.

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Unshielded Twisted Pair (UTP)

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UTP installation During UTP installation hardware connectivity is

accomplished by using an RJ-45 connector. The wires in a CAT5, 6 or 7 cable, for example

are arranged into pairs: each cable carries 8 wires, or 4 pairs.

The classification as CAT 5, 6, etc. is made base on the number or the frequency of the twists in each wire!

The twists in wire pairs in a UTP cable are put in to protect against electrical interference – from on wire affecting another. A cancellation effect. The interference is called “crosstalk”. More twists also allows longer cable runs.

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UTP installation: Note that the maximum length of an ethernet

cable run using CAT 5e UTP is 100 meters. This length includes all three of the segments

between the networking device – e.g., the router, and the workstation: next pg

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Max Distances for Horizontal Cabling (Using CAT5 UTP in an Ethernet network)

3 Meters – 90 Meters – 6 Meters 3 Meters: Work area patch cable.  From

computer to wall 90 Meters: What is considered the

Horizontal Cabling. From wall outlet to the patch panel in the MDF or IDF – Main or Intermediate Distribution Facility (Server Room).

6 Meters: The patch cable that cross connects a patch panel (in the MDF)

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Shielded Twisted Pair (STP)

STP includes a protective sheathing around the copper wire

The twisted pair is wrapped in foil to cut down on outside interference (RFI – radio frequency interference) and electromagnetic radiation

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Twisted Pair IEEE 802.5 (Token Ring) Originally, it used STP and the IBM

hermaphroditic connectors (below), but has since been adapted to use UTP and RJ-45 connectors

Token Ring networks run at either 4 Mbps or 16 Mbps

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Type 1 ( 2 twisted pairs, #22 AWG – American Wire Gauge)

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Type 2 ( 4 twisted pairs, #22 AWG – American Wire Gauge)

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Type 6 ( 2 twisted pairs, #26 AWG – American Wire Gauge)

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Activity B-1 – (pg 5-8)

Discussing twisted pair cabling

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RJ-45 RJ-45 connector and Ethernet

– For 10BaseT and 100BaseTX, pins 1, 2, 3, and 6 are needed to transport data. Of the 4 active pins, two are positive – one transmit (#1) and one receive (#3), and two are negative – again one transmit (#2) and one receive (#6).

– With full-duplex, all 8 pins are used. RJ-45 connector and Token Ring

– Many Token Ring cards have a modular connector. The active pin assignments are pins 3, 4, 5, and 6

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RJ45 Connectors

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Full-Duplex pinout

Ethernet 1000BaseT (Twisted Pair Pinout)

Pin # Signal Name Function

1 BI_DA+ i.e., Transmit/Receive, positive Bi-directional pair +A

2 BI_DA- i.e., Transmit/Receive, negative Bi-directional pair -A

3 BI_DB+ i.e., Transmit/Receive, positive Bi-directional pair +B

4 BI_DC+ i.e., Transmit/Receive, positive Bi-directional pair +C

5 BI_DC- i.e., Transmit/Receive, negative Bi-directional pair -C

6 BI_DB- i.e., Transmit/Receive, negative Bi-directional pair -B

7 BI_DD+ i.e., Transmit/Receive, positive Bi-directional pair +D

8 BI_DD- i.e., Transmit/Receive, negative Bi-directional pair -D

The wires are not necessarily bi-directional, i.e., you can have 2 positive transmit and 2 positive receive; the same is

true for the negative wires: 2 to send and 2 to receive.

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RJ-45 (cont)

The RJ-45 connector is also widely used for digital telephone sets, serial data transmissions, and many other applications.

The standards for how ethernet cables are configured and wired are determined by the TIA/EIA – “Telecommunications Industry Association/ Electronic Industry Association.”

The T568A and T568B standards, for example, determine the order in which the individual wires are arranged inside an ethernet cable: Orange, Orange/White, Green/White, Blue, etc.

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RJ45 pin positions

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RJ45 pin positions: Straight-through cable

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RJ45 pin positions: Crossover cable

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Other Twisted-Pair Cable connectors

The classic Token Ring cable has a DB-9 connector at one end and an IBM-style hermaphroditic data connector at the other

Some manufacturers use the RJ-11 and RJ-14 modular connectors

RJ-11 is a 4-pin connector while RJ-14 connectors have six pins (used for telephone jacks)

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RJ-11

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RJ-14

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Activity B-2 (page 5-12)

Terminating with an RJ-45 connector

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IEEE 1394 (FireWire)

External serial bus standard with speeds of up to 400 Mbps

Apple Computer, Inc. trademarked the term FireWire for its 1394 products

Most commonly used to connect peripherals to computers

It is possible to connect two computers together for basic file sharing

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IEEE 1394 specifications

Each FireWire port (bus) can support up to 63 devices

The total number of buses that can be linked together is 1,024

Transfer speeds include 100 Mbps, 200 Mbps and 400 Mbps

The supported distance for devices is 15 feet

Can be extended by adding repeaters every 15 feet for a maximum distance of 225 feet

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IEEE 1394 cabling (& connectors)

6 wire STP – Two pairs of separately shielded twisted

pairs– Two power wires– All encased in an overall shielded cable – Uses a 6-pin connector on both ends

4 wire STP– Same as 6 wire STP but without power

wires– Uses a 4-pin connector on both ends

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IEEE 1394 cabling (& connectors)

Another configuration uses either type of cable, with a 4-pin connector on one end and a 6-pin connector on the other

Standard cabling is 28 AWG Supports both asynchronous and

isochronous data transfer

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Activity B-3 (page 5-15)

Discussing FireWire

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Topic C Topic A: Network communication methods Topic B: Cables and connectors

Topic C: Coaxial and fiber optic cables Topic D: Ethernet and Token Ring

devices

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Properties of coaxial cable

Coaxial cable is composed of two conductors that share the same axis

For proper functioning, coaxial cable must always be terminated at both ends and the outer conductor grounded at only one end

Transmissions over coaxial cable might be either baseband or broadband

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Five Factors (page 5-17)– Cost: Moderate– Installation: Clumsy, compared to UTP– Capacity: Up to Fast Ethernet – 100 Mbps– Attenuation: Better than UTP. 2 types of coax:

Thinnet or 10Base2: This is the common type of coax that we are used to see being used for cable TV. It can go 185 meters between repeaters, which is better than UTP’s 100 meters.185 is close to 200, hence the “2” in 10Base2

Thicknet or 10Base5: This is horrible stuff; heavy, a pain to work with and connected using “vampire taps”. It can span 500 meters! between repeaters, hence the “5” in 10Base5.

– EMI Immunity: Less sensitive than UTP.

Properties of coaxial cable

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BNC cable connector

The standard BNC, or “bayonet nut connector”, is considered a 2-pin connector

This is a rather interesting construction. The inner core of a cable is usually the part that carries the data; but it is highly unusual for an outer, protective covering to do double duty as a second conductor!

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BNC cable connector

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Activity C-1

Terminating with a BNC connector

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Fiber optic cable

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Fiber optic properties

Fiber optic cable can support data rates up to 4 Gbps (not true; fiber can easily handle 10 Gbps. See IEEE standards for 10 Gigabit ethernet!) over distances ranging from 2 to 25 km (again, too conservative! Fiber can span dozens and even hundreds of miles – especially single-mode).

Common fiber optic cables are classified based on the diameter of their core

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Fiber optic cable types

Multimode Fiber (MMF) – Typically has a 62.5 micron core– Light travels down the core in many rays– Works with LED light sources of different

wavelengths

Single Mode Fiber (SMF)– Very small core of about 9 microns– Light travels down the cable in one ray– Optimal for very fast transmissions – (and the light source is a laser, not an

LED).

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Fiber optic connectors Fiber Optic Association http://www.thefoa.org/tech/connID.htm

ST: This and SC are the most common and the most often tested. “Keyed BNC”. On the left, below.

SC: A “push-pull” connector. Both the transmit and receive fibers are contained in a single clip. On the right, below.

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FSD: (Fixed Shroud Device) – e.g., the MIC (Media Independent Connector). Left.

LC: Smaller connector; to save space. On the right, below.

Fiber optic connectors - cont

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MTRJ: Another space-saver. Used with single or multi-mode. On the left.

SMA: A threaded connector. Obsolete. Twisting the end to remove it was a bad idea! On the right, below:

Fiber optic connectors - cont

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5 Factors (page 5-19)

– Cost: Expensive (but usually worth it).– Installation: Slow and technical. Be careful;

mistakes can cost a lot of money and you can injure your eyes.

– Capacity: Up to 10 Gigabit Ethernet – 10Gbps– Attenuation: Very little. Book says 25 Km, but

single mode fiber optic runs can span dozens of miles given the right conditions! In the cert exam, give the more conservative distance in the book.

– EMI Immunity: Immune! Also, very secure (you can cut into a copper-based cable and get information; you cannot “read” the light that passes through a fiber cable.

Properties of Fiber Optic cable

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Activity C-2 (page 5-21)

Discussing fiber optic cables

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Topic D Topic A: Network communication methods Topic B: Cables and connectors

Topic C: Coaxial and fiber optic cables Topic D: Ethernet and Token Ring

devices

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Ethernet devices Ethernet hub

– Take the signal transmitted from one computer and propagates it to all the other computers on the network Hubs operate at the Physical Layer. The

prototypical hub just receives a signal, boosts it a bit and sends it on its way. It never looks at any addresses – it doesn’t know how!)

Types of hubs– Passive– Active– Switching– Intelligent

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Passive hubs Take incoming electrical signals on one port

and pass them down the cable on its other ports – a simple rebroadcast.

All nodes see the signal just as if they were all connected on a physical bus topology

Many passive hubs have indicator lights for power, network traffic, link state per port, and collisions

But a passive hub doesn’t really even need a power source to perform its job. It is not a repeater; so it does not expand the limit of the topology – e.g., 100M for ethernet.

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Active hubs Repair weak signals by actually

retransmitting the data with proper transmission voltage and current

This essentially resets the cable length limitations for each port on the hub

Other active hubs have the ability to resynchronize data that has been received from a NIC. So they can check the timing of the data that enters the hub. This is almost a Transport layer function!

An active hub extends the max distance of a network topology. With the “5-4-3” rule, you can have up to 4 “repeaters” (active hubs) to create 5 “segments”, extending the max distance for ethernet from 100M to 500M!

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Switching hubs Each port on a switching hub is isolated from the other

ports On power up, it listens to each port and records the NIC

hardware address attached (this is a task normally done by a switch!)

Takes incoming packets and looks inside at the destination hardware address

Instead of rebroadcasting this packet on all the ports, it only sends the packet out the port connected to the destination machine. – This is definitely a “layer 2” job, normally done by a switch or a

bridge. A hub normally does not look at the MAC address of any device – it doesn’t know how to read them! This isn’t the only job of a switch, just one of the very important ones.

They also can be “auto-sensing”, so can adjust the speed of outgoing packets, and handle both 10 and 100 Mbps machines in the same network segment. With this feature, some machines can run at 100 Mbps and others can be running at 10 Mbps, and the hub can handle both!

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Intelligent hubs

The term intelligent hub is more nebulous than the terms discussed to this point

An intelligent hub might – have management features – support SNMP (Simple Network Management Protocol)

– be able to log into the hub (?) itself and perform tasks

– have advanced features

Make sure you understand features

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Activity D-1

Discussing Ethernet devices

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Token Ring devices

Are devices that are analogous to Ethernet hubs (but the functions are not at all the same!)

Called MSAUs - see another Power Point for Token Ring

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MSAUs

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Miscellaneous devices

Devices used for network cabling other than Ethernet and Token ring include:– Network patch panels – a bank of

connectors between a network device on one side (a switch, normally) and all the wall jacks in an area on the other.

– Transceivers – a device that allows one type of media to be connected to another. On one side is an AUI port; on the other is some kind of connector for the particular “channel access method”, like an RJ45, or a coax BNC, a fiber optic SC or ST, etc.

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Activity D-2 – (page 5-27)

Discussing Token Ring and other devices

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Unit summary

Discussed network communication methods

Learned about UTP, STP and FireWire

Learned about coaxial and fiber optic cables

Discussed network devices