LAN BASICS

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CHAPTER

Network Hardware

Chapter Objectives

• Describe the important basic network hardware and the internetworking hardware

• Discuss the desired characteristics of a server and a workstation

• Present different switching technologies

• Examine the routing process with the help of an example

Module 1

(4-06)

Introduction

Network Hardware Categories

• Local networking hardware

• Internetworking hardware

Local Networking Hardware

• Network Interface Cards (NICs)

• Cables

• Connectors

• Line drivers or repeaters

• Hubs / Switches

• Servers

• Workstations

Internetworking Hardware

• Line drivers or repeaters

• Transceivers

• Bridges

• Switches

• Routers

• Gateways

Current Day Internetworking

Devices

• Mostly confined to the following:

– Switches

– Routers

Folding of Devices into Switches

• Show Diagram

Folding of Devices into routers

• Show Diagram

Manageable Devices

• Switches and routers in a large network can be managed from a remote console

End of Module

MODULE

Network Interface Cards (NICs)

• Technology used

• Connectors used

• Speed of the network

• Interface technologies

NIC Basics

An Actual NIC Description

• 100BaseTX, PCI card

– 100 = speed in Mbps

– Base =Ethernet

– TX = Twisted pair

– 32-bit = bus width; it may also be 64-bit wide

– PCI = bus technology

10BaseT NIC

• 10BaseT cards

– Physical star and logical bus networks

– 10 Mbps speed

– Ethernet standard

– Twisted pair wiring

– RJ-45 Connectors

10Base2 NIC

• 10base2 cards

– Physical bus and logical bus networks

– 10 Mbps speed

– Ethernet standard

– Thin coaxial wiring

– BNC connectors

10Base5 NICs

• 10Base5

– Physical bus and logical star networks

– 10 Mbps speed

– Ethernet standard

– Thick coaxial wiring

– AUI connectors are used

• Note: 10BaseT, 10Base2 and 10Base5 are not used widely in practice anymore

100BaseTX NIC

• 100BaseTX

– 100 Mbps speed

– Fast Ethernet standard

– Twisted pair

• Higher quality Category 5 wires are normally required to implement 100 mbps Ethernet networks

• 1000BaseT

– 1000 Mbps

– Ethernet

– Twisted-pair wire

• Category 5e

• 1000BaseF

– 1000 Mbps

– Ethernet

– Optical fiber wire

1000BaseT NICs

1000BaseT NIC

Source: 3Com

Note the RJ-45 connection and the status lights on the card

Gigabit Ethernet Fiber NIC

Source: 3Com

•Note the two connectors for the RX and TX connections

•For use with PCI and PCI-X servers

Gigabit Ethernet NIC Properties

(Source: 3Com)

• Tenfold throughput boost: accelerate Fast Ethernet server connections to 1000 Mbps

• Fiber-optic cabling supports data security and faster throughput

• Automatic link aggregation and fail-over allow multiple NIC connections to be installed

• Advanced server features maximize availability, scalability, and fault tolerance

Gigabit Ethernet NIC Properties

(Source: 3Com)

• 64-bit PCI and PCI-X support: faster transmissions with lower CPU utilization

• Centralized, standards-compliant management lowers network administration time and total cost of ownership

• TCP/UDP/IP checksum offloads reduce host CPU load for improved system performance

• PCI Hot-Plug lets you remove/replace server NICs without taking the server offline

Token Ring Cards

• Token ring network cards

• Earlier token ring cards

– 4/1 Mbps

• Later token ring cards

– 16/4 Mbps

• Newer token ring cards

– Fast token ring networks

– 100/16/4 Mbps

PCI Bus Types for NICs

• Width

– Bus width is 32-bit or 64-bit

• Bus frequency

– 33 MHz

– 66 MHz

– 100 MHz etc.

• Technology

– PCI

– PCI-X

– PCI Express

Source: Tomshardware: www6.tomshardware.com/howto/02q3/020904/diy-06.html

Cable Connections for NICs

• BNC barrel connector

– Thin coaxial

• RJ 45

– Twisted pair

• Note the difference between RJ 11 and RJ-45

– RJ-11 is smaller and it is used in telephone connection

– RJ-45 is larger and it is used in LAN connections

Different Coax Connectors

Coaxial Cable Connectors

T connector

Network

Interface

Card

Thin coaxial cable

Terminator

BNC

AUI and Combo Cable

Connections for NICs

• AUI Possibilities

– Designed for a thick coaxial cable

– Designed for a token ring network

• Combo Cards

– Consisting of different ports

– BNC, RJ-45, AUI

RJ-45 Connectors

RJ-45 Port RJ-45 Connector

Possible Combo Card

Connections

• Thin coaxial cables (BNC)

• Twisted pair wires (RJ-45)

• Phone connection (RJ11)

• Thick coaxial cables (AUI)

Wireless Network Interface

Cards

• IEEE 802.11b

– 2.4 GHz, 11 Mbps

• IEEE 802.11b+, IEEE 802.11g?

– 2.4 GHz, up to 20% more throughput

• IEEE 802.11a

– 5.8 GHz, 54 Mbps

• IEEE 802.11g

• 2.4 GHz, 54 Mbps, 108 Mbps (Full duplex)?

• IEEE 802.11n

BNC

Example of Older 10Base2 Card

Source: Black Box

Example of Older 10BaseT Card

ISA

RJ 45

Source: Black Box

Example of Older Combo Card

RJ 45

Combo

Source: Black Box

BNC

D-Link Fast Ethernet Card

(100BaseTX)

D-Link 100BaseTX Specs

(Source D-Link)

• A manageable 10/100MB Dual Speed

Ethernet PCI Network Interface Card with

Wake-On-LAN (WOL)

• Fully compliant with IEEE802.3 10Base-T,

IEEE 802.3u 100Base-T specifications

• Supports ACPI/WOL (Advanced

Configuration Power Management Interface) feature, IP Multicast packet filtering, PXE

(PreBoot execution Environment) Boot ROM,

IEEE 802.1p, IEEE 802.1Q, and DMI (Desktop

Management Interface).

A Note on Remote Wake on LAN

(Source: Intel)

• A remote wake-up technology that enables you to remotely power systems "on" for offhours maintenance. A result of the Intel-IBM

Advanced Manageability Alliance and part of the Wired for Management Baseline

Specification, this technology helps save time on automated software installations, upgrades, disk backups and virus scans.

Equally important, it increases end-user productivity by moving such planned disruptions to off-hours.

Fast Ethernet PC Multi-Port

Card

NIC and modem connections

Fast Ethernet Card Specs.

The D-Link DMF-560TX is a 10/100Mb Dual Speed Ethernet PC Card with an integrated V.90/K56flex Data/Fax Modem. The DMF-560TX is targeted at notebook and laptop users that connect to a wide variety of datacommunications devices and services, and require access to faster technologies. Laptop users are able to seamlessly connect to both Ethernet and Fast Ethernet LANs, as well as send and receive faxes, connect to the

Internet, and dial into a Remote Access Server or PC using this one

PCMCIA PC Card solution.

The DMF-560TX strictly adheres to the IEEE Ethernet standards and the

ITU Data Communications and Modem standards in order to ensure maximum interoperability. The DMF-560TX attempts to connect at the highest speed supported by an ISP, LAN, host modem, or fax machine and automatically defaults to a lower speed until a stable connection can be created.

Fast Ethernet Card Operational

Specs.

Modem Operating Protocols

•V.90 (down-stream up to 56,000 bps)

•K56flex (down-stream up to 56,000 bps)

•V.34bis (up to 33,600 bps)

•V.34 (2,400 to 28,800 bps)

•V.32bis, V.32, V.22bis, V.23, V.22/Bell 212A, V.21/Bell 103

Error Correction Data Compression

•V.42/V.42bis and MCP Class 2 to 5

Fax Compatibility

•Group 3 send and receive

•EIA Class 1 fax commands

•V.17 (14,400 bps), V.29 (9600 bps), V.27ter (4800 bps),

•V.21 (300bps)

Token Ring Adapter (NIC)

Note the connector type.

Ethernet to Token Ring Bridge

Wireless PC Card Adapter

Wireless PC Card Specs

D-LinkAir DWL-650 PC Card Type-II

11Mbps Wireless LAN Adapter

The D-Link DWL-650 is an IEEE 802.11b compliant PC Card Type-II

11Mbps wireless LAN adapter. The DWL-650 will operate in 2.4 GHz

Direct Sequence Spread Spectrum (DSSS) for wireless networks in the home or office environment. It is designed to operate in 3.3V or 5.0V DC slots. In addition, the DWL-650 uses a 64/128-bit WEP (Wired Equivalent

Privacy) Encryption for a secure network connection.

The D-Link DWL-650 can operate in either Ad-Hoc mode (Peer-to-Peer networking without access point) or Infrastructure mode (Peer-to-Peer networking using an access point). In Infrastructure mode, the DWL-650 can be connected to a broadband residential gateway or a DSL/Cable modem for high-speed wireless Internet access on the existing network.

Wireless PC Card Specs

The DWL-650 can transmit data at 11, 5.5, 2 or 1 Mbps per channel. The DWL-650 transmit rate values can be manually selected for Auto Select 1 or 2 Mbps, Fixed 1 Mbps, Fixed 11

Mbps, Fixed 2 Mbps, Fixed 5.5 Mbps and Fully Auto. The

DWL-650 has full mobility and seamless roaming from cell to cell as well as across access points. The range of coverage per cell for indoor use is up to 328 feet and up to 984 feet per cell for outdoor use.

The DWL-650 comes with an internal non-detachable diversity patch antenna and one built-in green LED indicator for power, network link and activity. The DWL-650 is compatible with

Windows 98, Windows ME, Windows 2000, Windows XP.

Wireless PCI Card

Wireless PCI Card Specs

The D-LinkAir DWL-520 is an IEEE 802.11b wireless PCI adapter. The DWL-520 provides an integrated PCI solution that will operate within the 2.4 GHz Direct Sequence Spread

Spectrum (DSSS) for wireless networks in the home or office environment. Along with the advanced wireless technology that is incorporated into the DWL-520, wide range motherboard support is assured by compliance to the latest

PCI 2.2 standard interface. The DWL-520 is the solution for users and network administrators looking for the convenience offered by a wireless connection.

Wireless PCI Card Specs Cont.

The D-Link DWL-520 can operate in either Ad-Hoc mode (Peer-to-

Peer networking without an access point) or Infrastructure mode (Peer-to-Peer networking using an access point). In

Infrastructure mode, the DWL-520 can be connected to a wireless residential gateway with a broadband connection to enable wireless sharing of the High-speed Internet access.

The DWL-520 can transmit data at rates of 11Mpbs, 5.5Mbps, 2Mps and 1 Mbps per channel. With its detachable antenna using a reverse SMA connector, the DWL-520 has an effective range of up to 230 feet for indoor use and up to 984 feet in an outdoor environment. In addition, the DWL-520 supports 64/128-bit

WEP (Wired Equivalent Privacy) Encryption for network security.

Wireless 5 GHz

Wireless 5 GHz Specs

•Next generation of wireless products with its highperformance D-LinkAir Pro series of 5GHz networking technology.

Designed for indoor use, the D-LinkAir Pro DWL-A650 is a powerful notebook PC CardBus adapter that allows users to have mobile access to networks. It provides roaming capabilities from cell to cell and network to network.

•At 54 Megabits per second (Mbps), the D-LinkAir Pro DWL-

A650 5GHz high speed wireless CardBus adapter delivers the fastest standards-based wireless technology in the industry.

With IEEE 802.11a standard compliance, the D-LinkAir Pro

DWL-A650 high-speed wireless adapter provides excellent network interoperability.

Wireless 5 GHz Specs

(Continued)

• A proprietary “Turbo” mode allows the D-LinkAir Pro DWL-

A650 to operate at significantly greater data rates up to 72Mpbs.

Eight non-overlapping channels create less interference, which supplies higher average cell throughput to clients. The D-

LinkAir Pro DWL-A650 employs enhanced 152-bit Wired

Equivalent Privacy (WEP) and Dynamic Key Exchange to protect data from unauthorized access.

• The D-LinkAir Pro DWL-A650 is easily installed into a laptop

PC to provide connectivity directly to another wireless enabled device (ad-hoc mode) or through an 802.11a based access point

(infrastructure mode).

END OF MODULE

NIC Resources

MODULE

NIC Resources

• IRQ

• I/O address

• Base memory address, if provided

• DMA, if provided

IRQ

• Must be unique for each device, unless it is steered

– IRQ steering

• An NIC requires an IRQ

• IRQ is used to gain the attention of the

CPU

• There are a limited number of IRQs available on a computer

IRQ Assignment (learnthat.com)

IRQ Device

9

10

11

12

13

14

15

6

7

4

5

8

2

3

0

1

Timer

Keyboard

Wired to IRQ 9

COM 2 (COM 4)

COM 1 (COM 3)

Available (often LPT2, sound cards, or network cards)

Floppy Disk Controller

LPT1

Clock

Wired to IRQ 2

Unused

Unused

Mouse Port

Coprocessor

Hard Disk Controller

Unused

I/O Address

• Must be unique to each device

• Each device of port must have an I/O address

• The NIC must have an I/O Address as well

Address (Hex)

00-0F

20-21

40-43

1F0-1F8

200-20F

238-23B

278-27F

2E8-2EF

2F8-2FF

300-30F

330-33F

378-37F

3E8-3EF

3F0-3F7

3F8-3FF

Common I/O Address

Assginemnt (learnthat.com)

Device

DMA Controller

Interrupt Controller

Timer

Hard Disk Controller

Joystick Controller

Bus Mouse

LPT2

COM4 Serial Port

COM2 Serial Port

Ethernet Card

MIDI Port

LPT1 Port

COM3 Serial Port

Floppy Disk Controller

COM1 Serial Port

I/O Address

( www.techencylopedia.com

)

• There is a 64K address space for I/O addresses, although typically less than 1K is used. Each board that uses an I/O address contains a few bytes of memory (16, 32, etc.) set to a default address range. One or more alternate addresses is also provided to resolve conflicts with other boards. These I/O spaces are a bunch of tiny memory banks scattered over different devices. As long as each one is set to a different address, the

CPU can transmit signals to the appropriate boards without conflict.

I/O Address Continued

( www.techencylopedia.com

)

• An I/O address operation takes place as follows. If a program needs to send a byte to the serial port, it issues an OUT instruction to the CPU with the address of that serial port.

The CPU notifies the address bus to activate the I/O space, not regular memory, and the address bus signals the appropriate byte location on the board. The CPU then sends the data character over the data bus to that memory location.

Base Memory Address

• Must have a unique range for the NIC card

• Some older cards did not require the base memory address to be specified

• Direct Memory Access

• Channels are assigned for DMA

• Not all the NIC cards have DMA

• Newer PCI technologies used for expansion slots have made DMA somewhat obsolete

DMA

DMA Use (Source learnthat.com)

• In most PCs, there are 8 DMA Channels.

• In most modern PCs, DMA shouldn't be used as it just slows it down. But, older PCs may use DMA.

• Channels 4-7 are usually available, while

Channel 0 is used to refresh DRAM, Channel

1 is used by a hard disk controller or sound card, and Channel 2 is usually used by the floppy disk controller.

Resource Allocation on a NIC

Examining the Network

Resources

Device Manager NIC

Resources Properties

END OF MODULE

MODULE

Network Connectors and Hubs

Simple Connectors

• T connectors

– An interface between the NIC and the cables

• Terminators

– Used at both ends of a bus network

T Connector

Terminator

Example of T-Connector and

Terminator

T Connector

Terminator

Source: Black Box

Connectors : Hubs

• Types

– Passive hub

– Active hub

– Intelligent hub

• Passive hubs

– Simply provides the physical and the electrical connection for the network

• Active hubs

– A Multi-port device

– Amplifies LAN signals

• Manageable hubs

– Has built-in manageability

– Some are manageable hubs

Connectors : Passive Hub

MAU

WS WS

Hub Connecting A Token-ring Network

WS

A Manageable Hub/ Switches

WS

WS

WS

Active Hub

Backbone

Remote

Workstation

Remote Monitor

LAN Management Software

• Sophisticated

• Monitor the network traffic through each of the ports

• Becoming popular

• Standardized protocol for remote management exists

– SNMP (Simple Network Management

Protocol)

SNMP

• A major protocol used in the management of networks

• A number of LAN management software is based on the SNMP protocol

SNMP Cont. (Source: Cisco)

• The Simple Network Management Protocol (SNMP) is an application-layer protocol designed to facilitate the exchange of management information between network devices.

• By using SNMP-transported data (such as packets per second and network error rates), network administrators can more easily manage network performance, find and solve network problems, and plan for network growth.

• SNMP is a relatively simple protocol, yet its feature set is sufficiently powerful to handle the difficult problems presented in trying to manage today's heterogeneous networks.

• Today, SNMP is the most popular protocol for managing diverse commercial internetworks as well as those used in universities and research organizations.

SNMP Cont.

• Like the Transmission Control Protocol (TCP), SNMP is an Internet protocol.

• There are two versions of SNMP: Version 1 and

Version 2.

• Most of the changes introduced in Version 2 increase SNMP's security capabilities. Other changes increase interoperability by more rigorously defining the specifications for SNMP implementation.

• SNMP's creators believe that after a relatively brief period of coexistence, SNMP Version 2 (SNMPv2) will largely replace SNMP Version 1 (SNMPv1).

Web Research

• Obtain additional information on the following LAN troubleshooting software

– LAN Analyzer

– LAN Sniffer

Example of a Hub Used in Ring

Network

Source: Black Box

Stackable

Hubs

Example of Hubs Used in the

Star Network

Source: Black Box

END OF MODULE

Web Research

• Photonic switching

– www.agilent.com/comms/photonicswitch

– www.cnn.com/tech

MODULE

Server and Workstation

Hardware

Module Objectives

• Give an overview of the different types of the server hardware

• Discuss the desired characteristics of a server

• Provide a specification for a workstation

Servers

• Types

– Powerful micros

– Servers

– Super-servers

– Mini and large computers are used as servers

• In a client-server environment, the server also acts as an engine for database execution

• In general, the server is used for the sharing of stored data and application

Desired Characteristics of Server:

Processor and Storage

Requirement

• Powerful processor

– Latest Pentium Processor for example

– Multiple processors, if necessary

• Large storage space

– Several gigabytes at a minimum

– Actual requirement will vary with LAN size

• Fast disk access speed

– Less than 10 ms, for example

• Versatile CD-ROM access (Towers)

• Fault tolerance

Processors

• Intel Pentium 4, 32-bit processors

• Intel Itanium 64-bit processors

• Special Xeon processors meant for servers

• Multiple processors

– Symmetric Multi-Processing (SMP)

• Other processors

– Spark (Sun), AMD, Motorola, IBM’s own processors etc.

Symmetric Multiprocessing

(SMP) Source: Search390.com

• SMP (symmetric multiprocessing) is the processing of program s by multiple processor s that share a common operating system and memory . In symmetric (or

"tightly coupled") multiprocessing, the processors share memory and the I/O bus or data path. A single copy of the operating system is in charge of all the processors. SMP, also known as a "shared everything" system, does not usually exceed 16 processors.

Chip Set

• Chip sets designed for servers to boost

I/O operation

Hard Disk Technologies

• SCSI

• ATA

• Serial ATA (SATA)

• Fiber channel storage

• RAID

Overview of Storage

Technologies

• SCSI, Small Computer Systems Interface, is widely used in mid- to high- performance workstations and servers.

• SCSI offers faster transfer rates than ATA / IDE , the interface most commonly used in desktop PCs.

• In general, ATA/IDE is considered easier to implement and less expensive than SCSI but does not offer as many features.

– For example, SCSI can support up to 16 devices on a single bus (IDE offers two), generally offers faster throughput, uses less CPU horsepower during operation, and is therefore more efficient in demanding multiple initiator applications for multi-users and uses. This is significant because it allows the processor to perform more commands at one time making for greater efficiency.

SCSI Standards

S

C

SI

Fast

SCSI

Ultra

SCSI

Wide

Ultra

SCSI

Ultra2

SCSI

Wide

Ultra2

SCSI

Ultra3

SCSI

Data transfer rates max.

Bus speed (MB/sec)

5 10

Maximum Data Bus width (bits)

20 40

8bit

8-bit 8-bit 16-bit

40 80

8-bit 16-bit

160

16-bit

Max. cable length

(meters)

Max. device support

6 3

8 8

1.5 - 3 1.5 - 3 12

8 - 4 8 - 4 8

12

16

12

16

SCSI Terms (source: IBM)

• The SCSI terms Fast, Ultra, or Ultra2 typically refer to data rate increases that move data faster on the bus, while the term Wide refers to adding more lanes to the bus, typically transferring 16 bits of data at one time rather than eight bits. Other differences between the standards include the maximum cable length and the number of devices that can exist on the same SCSI bus.

Ultra 3 SCSI (source: IBM)

•As one of the recent developments in SCSI, Ultra3 SCSI presents significant feature and benefit enhancements over Ultra2 SCSI products. Ultra3 SCSI products are designed to offer, at a minimum, the following features:

Cyclic Redundancy Check (CRC) , domain validation , and double transition clocking , none of which are available in Ultra2 SCSI products.

•These features are designed to improve speed, performance, and overall manageability of SCSI.

Ultra 160 (source: IBM)

• The subset of Ultra3 that includes the three features, Cyclic Redundancy Check (CRC) , domain validation , and double transition clocking , is commonly called Ultra160, for its speed 160MB per/sec. The main difference between Ultra3 and Ultra160 is that Ultra3 implementations may offer other features in addition to those listed above.

ATA

• The term ATA stands for Advanced Technology

Attachment, for the standard bus interface on the original IBM AT computer. This interface also is called IDE , for Integrated Drive Electronics; ATA is the official ANSI (American National Standard

Institute) standard designation.

• Also known as Ultra DMA, ATA is generally the least expensive hard drive interface; many computer motherboards include ATA controllers and cable connectors that typically control the "C" drive that contains the operating system. However, ATA is a slightly slower drive interface, so it is used primarily in single user computer applications or low-end

RAID systems.

Data transfer rates max. Bus speed

(MB/sec)

ATA Variations

ATA/ ATA-2 Ultra-ATA/33 Ultra-ATA/66

8.3

16.6

33 66

16-bit Maximum Data Bus width (bits)

16-bit 16-bit 16-bit

Max. device support 2 2 2 2

Serial ATA (SATA)

Fiber-Channel

• Fiber Channel - Arbitrated Loop (FC-AL) is an exceptionally high-bandwidth industrystandard interface primarily targeted toward high-end servers and similar demanding applications.

• FC-AL uses fiber optic cabling in a loop configuration to produce maximum transfer speeds of 100 MB/second and is designed to connect up to 127 devices as far as 10 kilometers apart, enabling data storage in remote, secure locations distant from the server.

More on Fiber Channel

• FC-AL devices can be dual ported, providing two simultaneous input/output sessions that doubles maximum throughput, and FC-AL enables "hot swapping," so you can add and remove hard drives without interrupting system operation, an important option in server environments.

• FC-AL adapters tend to cost more than SCSI adapters.

PCI BUS Technology

• PCI is preferred

– 32-bit and 64-bits

• PCI-X

– An extension to the PCI Bus interface

• General PCI standards

– PCI 1.0, 2.0 and 3.0

• PCI Express

A Note on PCI-X 2.0

(Source PCISIG)

• PCI-X 2.0 is an evolutionary, backward compatible technology that builds on the foundation of PCI and PCI-X while offering bandwidths 4 times higher than PCI-X without increasing pin-count.

• These new, higher bandwidths are ideal for server-oriented adapter cards in the areas of

Fibre Channel, RAID, networking,

InfiniBand™ Architecture, SCSI, iSCSI, and other high-bandwidth technologies.

PCI-X 2.0 Performance

Advantage (Source PCISIG)

• Doubles and Quadruples PCI-X bandwidth.

• Enables 10Gb Ethernet, 10Gb Fiber

Channel, InfiniBand™ Architecture, and other IO technologies.

• Performance 32 times higher than the first generation of PCI.

Desired Characteristics of Server:

Bus and Memory Technologies

• Better bus technology

– PCI

• Memory

– In excess of 512 Mbytes

– SDRAM or similar memory technology functioning at 10 nanoseconds or less

– The 168-pin SDRAM is also known as the DIMM chips as opposed to the 72-pin SIMM chips

– 182 DDR RAM

– Rambus RAM

Desired Characteristics of Server:

Reliability

• Good back-up facilities

– Back-up tape

• Uninterruptible Power Supply (UPS)

Fault Tolerant Feature for

Servers

• RAID storage technology

– A system based on multiple disk

– Hot-swappable disks

• Redundant power supply

– Hot-swappable power supply

Hot Pluggable and Hot

Swappable

• Hot Pluggable

– When a card or a device is plugged into the computer (PCI), the computer will recognize the device automatically and install the device

• An example is a NIC

• Hot Swappable

– A device that can be removed and replaced without having switch off the computer

• An example is a hard drive

Workstation

• Most applications are executed at the workstation in the case of a file server

• Therefore, it must be powerful in terms of the processor and the memory

• As a rule of thumb, the workstation must be as powerful as it were to be used as a standalone unit to run the applications

Workstation Processor and

Memory

• Powerful processor

– Pentium class processor

• Adequate memory

– 32 Mbytes or more

– DIMM preferred although fast EDO SIMM may also be used

Workstation Storage and

Compatibility

• Sufficient storage

– Storage in gigabytes

– Important in a client-server environment

– Front-end tools are stored on the workstation

• Speed of storage

– Ultra DMA or SCSI preferred

– EIDE may also be used

• Hardware components with appropriate drivers for the client operating system

Reliability

• Power surge protector

• Uninterruptible Power Supply (UPS), for critical applications

END OF MODULE

Repeater

MODULE

An Overview of Repeaters

• Used for extending the physical span of a network

– An example is the extension of the distance between a hub and a node

• Span is often limited by design considerations

• 10base5

– The span is limited to 500 meters

A Repeater Connection

Expanding the Span of the Network

Source: Black Box

Another Example of Repeater

Connection

Extending the distance between the backbone and the nodes.

Source: Black Box

Current Day Use of Repeaters

• Fiber optic repeaters are used for extending the distance between two nodes in a link or a network

Operations of a Repeater Within the ISO OSI Model

• Operates at the lower level of the ISO

OSI model, namely layer 1

– Physical layer

Physical

Layer

Medium

Repeater

Physical

Layer

Medium

Other Devices Used for

Extending the Span of a Network

• Line Drivers

• Short-Haul Modems

Another Layer 1 Device

• Hub

– This is simply an electrical connecting device used in the configuration of a network

• The topology in this case would be that of a star topology

END OF MODULE

Bridge

MODULE

An Overview of a Bridge

• A device used for connecting two LANs operating usually under the same protocol

– There are bridges that connect LAN segments operating under different protocols

• Currently, the term bridge is loosely being used to describe different interconnecting devices

– Used now for connecting LANs operating under different protocols as well

Purpose of a Bridge

• Facilitate the movement of data packet from one network segment to another

• Not a sophisticated internetworking device

• Bridge does not perform the routing of information to different segments of a network

• Connects two network segments and not multiple network segments

Bridge : ISO-OSI Layer of

Operation

Data

Link

Layer

Physical

Layer

Bridge

Data

Link

Layer

Physical

Layer

X Medium X Medium

A simple bridge operates at the second layer of the ISO model.

Practical Bridge Implementations

• Local Bridge

• Remote Bridge

Local and Remote Bridges

• Local bridge

– Connects two different LANs located locally

• Remote bridge

– Connects LAN segments that are geographically apart

– An example is a device that provide dialup access to a LAN

A Practical Bridge Example

END OF MODULE

Switch

MODULE

Switch Definition and Purpose

• A switch is defined as a device that allows a LAN to be segmented

– The segments will operate under the same protocol

Difference Between a Switch and a Bridge

• A switch focuses on segmenting a LAN

• A bridge is concerned with linking two network segments that operate under different protocols

Purpose of a Switch

• Improve the network performance and reliability

• Better manage the network in general

Switch : ISO-OSI Layer of

Operation

Data

Link

Layer

Physical

Layer

Switch

Data

Link

Layer

Physical

Layer

X Medium X Medium

A simple Switch operates at the second layer of the ISO model.

Layer 3 Switches

• Some switches operate at Layer 3 of the

ISO-OSI model

• These switches perform routing as well

Performance Improvement in

Segmented Networks

• Performance is improved especially in the case of a bus network

• Multiple bus paths are now available for communication

• Each segment can engage in simultaneous communication within itself

• Easier to isolate a problem to a segment

– Thus, better manage the entire network

Network Reliability

• When one segment does not function, the other segments can continue to function

– Offers better reliability to at least part of the function

Switches in Ethernet and Token

Ring LANs

• Switches were originally designed for segmenting Ethernet LANs

– Used extensively in configuring large

Ethernet bus LANs

• Physically the network configured would still largely remain based on the star topology

• Switches are now available for token ring networks as well

Use of Switches in Linking LAN

Segments

Crossover Traffic

Switch

Segment 1

Hub Hub

Segment 2

WS Server WS Server

Segment 1

Using A Switch to

Link Bus LAN Segments

Switch

Segment 2

Use of Switches in

Internetworking

• Because the typical inter-networking connection involves multiple segments, the use of a switch is more common than the use of a bridge

Use of Switches for Higher

Bandwidth

100 MBps Switch

WS

WS WS WS

Each port in theory has a bandwidth of 100 Mbps.

END OF MODULE

MODULE

Switching Technology

Module Objectives

• Explain the basic operation of a switch

• List the switching technologies and describe their operation

– Cut-through and store-and-forward technologies

The Basic Operation of Switches

Receiver’s Address Sender’s Address Data

• A data packet is analyzed

• Receiver’s addresses is checked

• If it indicates the receiver to be in the same segment, the packet is dropped

• If it indicates the receiver to be in a different segment, the packet is forwarded to a different segment

Switching Technologies

• There are two major types of switching technologies

– Cut-through

– Store-and-forward

Cut-Through Technology

• Reads only part of the packet

– The addresses header

– Packet is forwarded accordingly

• Bad packets are not filtered

• Faster

• Less error checking

Store-and-Forward Technology

• Entire packet is processed

• Packets are filtered

– Bad packets are filtered

• Slower

• More error checking

Switching Technology

Comparison

Header Sender’s Add

Cut-through

Store-and-forward

Receiver’s Add Data

Switching Technology Operation at the ISO Layer

• In each of the two cases of switching technologies no protocol conversion takes place

• Forwarding and filtering are done at the

MAC layer

• A switch switches the traffic based on

MAC address

• Fiber channel

• Clustering

• Load Balancing

Web Research

END OF MODULE

Routers

MODULE

The Purpose of a Router

• Connect LANs operating under different protocols

• The LANs connected are better known as sub-networks instead of network segments

– The term segments is nevertheless used in practice

– Each segment basically represents a subnet

Router Characteristics

• A router is a true internetworking device

– Connects different sub-networks together

• Establishes a logical path of communication between the sub-networks

• Contributes to the modular construction of a network

– Network itself is better managed

– Network resources are better utilized

Internetworking with a Router

IEEE 802.3

Sub-network

Router

PC-NFS

Sub-network

IEEE 802.5

Sub-network

Routers, Switches and Hubs in

Perspective

Backbone

Router

Switch Switch

Hub Hub

S WS S WS

Sub-network 1

Sub-network 2

Difference Between Routers,

Switches and Hubs

• Hubs

– Simply provides the mechanical and electrical connections between the nodes

• Switches

– Examine the data packet for the destination address

– Do not alter the data packets

– Switches based on MAC address

– Basically a Layer 2 device

• Routers

– Examine and alter the data packet format

– Perform protocol conversion

– Routes based on IP address

– Basically a Layer 3 device

Router Requirements

• Requires more processing power compared to switches and bridges

• Operations fall within the network layer of the ISO-OSI communication model

Router : Network Layer Interface

NETWORK

LAYER

DATA LINK

LAYER

PHYSICAL

LAYER

X MEDIUM

ROUTER

NETWORK

LAYER

DATA LINK

LAYER

PHYSICAL

LAYER

X MEDIUM

Layer 3

Layer 2

Layer 1

Devices and Layers

NETWORK

LAYER

DATA LINK

LAYER

PHYSICAL

LAYER

Routers

Switches

Hubs and

Repeaters

A Practical Router Example

Router

Router

Router

Router

Router

END OF MODULE

Gateway

MODULE

Web Exercise

• Build a small network consisting of 4 workstations and 1 server for a small business

– Provide details of the hardware in terms of the types of hardware and the cost of the hardware

• Connect the network to the Internet

– Again provide the cost associated with the hardware required to make the connection

• In both of the above cases, also provide a schematic diagram showing the network connections

An Introduction to Gateways

• Gateways are comprehensive internetworking devices

• They can be computers themselves

Gateways in the Past

• Very popular

• They were the only devices that could be used for internetworking

• Computers of the past were not designed with network connections in mind

– Interconnection of different computer systems has to be managed and driven by an advanced device such as a gateway

The Present Scenario

• Computers are now designed with due consideration given to network connections

• Larger networks could today be configured using internetworking devices

– Routers, switches, hubs etc.

• Even, mainframes can be connected easily using the above internetworking devices

• In the past, because of the different nature of the network (SNA), connecting a mainframe to a LAN often required a gateway (SAN

Gateway)

Use of Gateways at Present

• Used in the rare occasion when neither of the internetworking devices could be used for connecting the sub-networks together

• Example

– Connection of a legacy mainframe system to a bus LAN

Rule of Thump

• Gateways are used for interconnecting vastly differing computing environments together

Gateway

Interface

Card

NIC Card

Gateway software

SNA

Gateway

SNA Gateway

FEP

WS

WS

LAN - Ethernet

IBM - SNA

Gateway’s Functional Relationship to the ISO-OSI Model

Application

Presentation

Session

Transport

Network

Data Link

Physical

Application

Presentation

Session

Transport

Network

Data Link

Physical

END OF MODULE

END OF MODULE

END OF CHAPTER

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