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