Objectives:

Chapter 2: Physical Layer

Transmission media and cabling LAN Physical Layer Ethernet WAN Technologies Network Devices

Guided Transmission Data

• Magnetic Media

• Twisted Pair

• Coaxial Cable

• Fiber Optics

Twisted Pair

(a) Category 3 UTP.(b) Category 5 UTP.

Coaxial Cable

A coaxial cable.

Fiber Cables

(a) Side view of a single fiber.(b) End view of a sheath with three fibers.

Fiber Optics

(a) Three examples of a light ray from inside a silica fiber impinging on the air/silica boundary at different angles.

(b) Light trapped by total internal reflection.

Lightwave Transmission

Convection currents can interfere with laser communication systems.

A bidirectional system with two lasers is pictured here.

The Local Loop: Modems, ADSL, and Wireless

The use of both analog and digital transmissions for a computer to computer call. Conversion is done by the modems and codecs.

Modems

(a) A binary signal

(b) Amplitude modulation(c) Frequency modulation

(d) Phase modulation

Digital Subscriber Lines (3)

A typical ADSL equipment configuration.

Wireless Communication

a) Wireless networks use radio frequency (RF), laser, infrared (IR), or satellite/microwaves to carry signals from one computer to another without a permanent cable connection.

LAN Physical Layer

a)Each media has advantages and disadvantages. Some of the advantage or disadvantage comparisons concern the following: – Cable length

– Cost

– Ease of installation

– Susceptibility to interference

Ethernet in the Campusa)Ethernet technologies can be used in a campus

network in several different ways:

Connection Media / UTP Implementationa)EIA/TIA specifies an RJ-45 connector for unshielded twisted-pair (UTP) cable. The letters RJ stand for registered jack, and the number 45 refers to a specific wiring sequence. The RJ-45 connector and jack are the most common

Attach the RJ-45

Straight-Through Cables

a)Maintain the pin connection all the way through the cable.

b)Wire connected to pin 1 is the same on both ends.

c)Used to connect such devices as PCs or routers to other devices such as hubs or switches.

Crossover Cable

a)Cross the critical pair to properly align, transmit, and receive signals on devices with like connections.

b)Pin 1 connected to pin 3, pin 2 connected to pin 6.

c)Used to connect similar devices: switch to switch, switch to hub, hub to hub, router to router, PC to PC.

Rollover Cables Setting Up Console Connections

a) Maintain the pin connection all the way through the cable.

b) The console port allows monitoring and configuration of a Cisco hub, switch, or router.

c) Connect the devices using a rollover cable from the console port, on the router, to the serial port, on the terminal (workstation), Then Configure the terminal emulation application with the following common equipment (COM) port settings: 9600 bps, 8 data bits, no parity, 1 stop bit, and no flow control.

LAN Transmission Technologies

a) Ethernet 10 Mbit/s

b) Token Ring 4/16 Mbit/s

c) Fast Ethernet 100 Mbit/s

d) FDDI 100 Mbit/s

e) Gigabit Ethernet 1 Gbit/s

f) ATM 25 Mbit/s to 2.4 Gbit/s

Only Ethernet versions are growing

1- IEEE 802.3z 2- IEEE 802.3ab

1- Fiber Cabling Specifications 2- Copper Cabling Specifications

Gigabit Ethernet Standards

WAN Technologies

a) A Wide Area Network (WAN) is a data communications network that covers a relatively broad geographic area and often uses transmission facilities provided by common carriers, such as telephone companies.

b) A WAN is an interconnection of LANs.

c) A WAN functions at the lower three layers of the OSI model.

WAN Physical Layer

a) The speed of these connections ranges from 2400 bits per second (bps) to T1 service at 1.544 megabits per second (Mbps) and E1 service at 2.048 Mbps.

b) ISDN offers dial-on-demand connections or dial backup services.

c) With the increasing demand for residential broadband high-speed services, Digital Subscriber Line (DSL) and cable modem connections are becoming more popular.

WAN Backbones

a) T1 (DS1) 1.54 Mbit/s North Americab) E1 2.04 Mbit/s CCITTc) E3 34.36 Mbit/s CCITTd) T3 (DS3) 44.73 Mbit/s North Americae) OC1 51.84 Mbit/s Sonet fiberf) OC3 155.52 Mbit/s Sonet fiberg) OC96 4.976 Gbit/s Sonet fiberh) OC192 10 Gbit/s Sonet fiberi) OC768 40 Gbit/s Sonet fiber

Network Devices

Layer 1 network devices: Repeaters, HubsLayer 2 network devices: Bridges, Switches, modems, NICsLayer 3 network devices: Repeaters, Hubs

Repeaters: Layer 1

Repeaters

A repeater solves the problem of too many nodes and not enough cable; cleans, amplifies, and resends a

signal that is weakened by long cable length.

Hubs: Layer 1

Hubs

• Regenerate and repeat signals

• Used as network concentration points

• Multiport repeater

• Becoming obsolete

Hubs

Bridges: Layer 2

Bridges

Designed to create two or more LAN segments, each of which is a separate collision domain

Bridges filter traffic by looking at MAC

addresses.

Switches: Layer 2

A Switch is a Multiport Bridge

LAN Switches

Switches Combine the connectivity of a hub with the traffic regulation of a bridge on each port

Core and Layer3 Switches

NICs in the OSI Model

Host Connectivity

a) When selecting a NIC, consider the following:

– Network architecture– Operating system– Media type– Data transfer speed– Available bus types

NICs

a) Bus architectures

• ISA (Industry Standard Architecture)• EISA (Extended ISA)• PCI (Peripheral Component Interconnect)• MCA (Micro Channel Architecture)• PCMCIA (Personal Computer Memory Card

International Association)

Routers and Serial Connectionsa) Routers are used to connect

LANs to WANs

b) Determine whether DTE or DCE connectors are required. The DTE is the endpoint of the user’s device on the WAN link.

c) The DCE is the point where responsibility for delivering data passes into the hands of the service provider.

d) When cabling routers for serial connectivity, the routers will either have fixed or modular ports.

Routers and DSL Connections

a) The Cisco 827 ADSL router has one Asymmetric Digital Subscriber Line (ADSL) interface.

b) To connect an ADSL line to the ADSL port on a router, do the following:

1. Connect the phone cable to the ADSL port on the router.

2. Connect the other end of the phone cable to the phone jack.