Peripherals

LAN PERIPHERALS TRANSMISSION MEDIA Data is transmitted over copper wires, fiber optic cable, radio and microwaves. The term 'media' is used to generically refer to the physical connectors, wires or devices used to plug things together. Basic Communications Media Types

• Copper

•

o o o o Fiber o o

Unshielded Twisted Pair (3,5,5e,6,7) Shielded Twisted Pair Coaxial Cable (Thinnet, Thicknet) Heliax Optic Single-mode Multi-mode

COPPER Coaxial Cable . Coaxial cable consists of a copper wire core surrounded by a plastic cladding sheathed in a wire mesh. Coaxial cable comes in two sizes which are called thinnet and thicknet.

Unshielded Twisted Pair (UTP) If you use two pairs of wires to enable two communications circuits, one for transmit, and one for receive and If you twist the wires of each pair, you can place them much closer together. There are several grades of coaxial cable with category ratings. There are Category 3 (<10 Mbps), Category 5 (10 Mbps), Category 5e (10/100 Mbps) and Category 6 (100/1000 Mbps) versions of unshielded twisted pair. Fiber Optic Single Mode

Single mode fiber refers to the fact that only a single wavelength (one color of light) is transmitted over the physical medium. Typically, single mode fiber is true doped fiberglass fibers wrapped in a plastic cladding. Single mode typically has much longer reach, but a larger bend radius than multi-mode. Dispersion Shifted Non-Dispersion Shifted Non-Zero Dispersion-Shifted Multi-Mode Multi-mode fiber can carry multiple wavelengths, is made of special clear plastic materials and has a much smaller bend radius than single mode fiber. Multi-mode does not have as long a reach as single mode fiber. Step Index Graded-Index

MEDIA ACCESS UNIT (MAU) A MAU is a repeater device used to connect Token Ring devices into a physical star topology. There are two types of MAUs, active and passive. Active MAUs are electrically powered from a separate source and passive MAUs run on the power from the network connections. Transceivers are also referred to as Medium Access Units (MAUs). They are used to connect nodes to the various Ethernet media. Most computers and network interface cards contain a built-in 10BASE-T or 10BASE2 transceiver which allows them to be connected directly to Ethernet without the need for an external transceiver. Many Ethernet devices provide an attachment unit interface (AUI) connector to allow the user to connect to any type of medium via an external transceiver. The AUI connector consists of a 15-pin D-shell type connector, female on the computer side, male on the transceiver side. For Fast Ethernet networks, a new interface called the MII (Media Independent Interface) was developed to offer a flexible way to

support 100 Mbps connections. The MII is a popular way to connect 100BASE-FX links to copper-based Fast Ethernet devices.

HUBS Hubs are repeater devices designed to replicate a signal on one port and replicating it on all other ports. This works very well for small network segments where there are only a few devices. However, in highly populated Ethernet networks, this can create a collision domain which experiences a collision rate that is so high, no data can be transmitted. Hubs/repeaters are used to connect together two or more segments of any type of medium. In larger designs, signal quality begins to deteriorate as segments exceed their maximum length. Hubs provide the signal amplification required to allow a segment to be extended a greater distance. A hub repeats any incoming signal to all ports. Hubs are necessary in star topologies such as 10BASE-T. A multi-port twisted pair hub allows several pointto-point segments to be joined into one network. One end of the pointto-point link is attached to the hub and the other is attached to the computer. If the hub is attached to a backbone, then all computers at the end of the twisted pair segments can communicate with all the hosts on the backbone.

BRIDGES Bridges connect two LAN segments of similar or dissimilar types, such as Ethernet and Token Ring. This allows two Ethernet segments to behave like a single Ethernet allowing any pair of computers on the extended Ethernet to communicate. Bridges are transparent therefore computers don’t know whether a bridge separates them. Bridges map the Ethernet addresses of the nodes residing on each network segment and allow only necessary traffic to pass through the bridge. When a packet is received by the bridge, the bridge determines the destination and source segments. If the segments are the same, the packet is dropped or also referred to as “filtered"; if the segments are different, then the packet is "forwarded" to the correct segment. Additionally, bridges do not forward bad or misaligned packets.

Bridges are also called "store-and-forward" devices because they look at the whole Ethernet packet before making filtering or forwarding decisions. Filtering packets and regenerating forwarded packets enables bridging technology to split a network into separate collision domains. Bridges are able to isolate network problems; if interference occurs on one of two segments, the bridge will receive and discard an invalid frame keeping the problem from affecting the other segment. This allows for greater distances and more repeaters to be used in the total network design.

SWITCHES LAN switches link multiple networks together and have two basic architectures: cut-through and store-and-forward. In the past, cut-through switches were faster because they examined the packet destination address only before forwarding it on to its destination segment. A store-and-forward switch works like a bridge in a way that it accepts and analyzes the entire packet before forwarding it to its destination. Historically, store-and-forward took more time to examine the entire packet, although one benefit was that it allowed the switch to catch certain packet errors and keep them from propagating through the network. Today, the speed of store-and-forward switches has caught up with cut-through switches so the difference between the two is minimal. Also, there are a large number of hybrid switches available that mix both cut-through and store-and-forward architectures. Both cut-through and store-and-forward switches separate a network into collision domains, allowing network design rules to be extended. Each of the segments attached to an Ethernet switch has a full 10 Mbps of bandwidth shared by fewer users, which results in better performance (as opposed to hubs that only allow bandwidth sharing from a single Ethernet). Newer switches today offer highspeed links, either Fast Ethernet, Gigabit Ethernet, 10 Gigabit Ethernet or ATM. These are used to link switches together or give added bandwidth to high-traffic servers. A network composed of a number of switches linked together via uplinks is termed a "collapsed backbone" network. Switches occupy the same place in the network as hubs. Unlike hubs, switches examine each packet and process it accordingly rather than simply repeating the signal to all ports. Switches map the Ethernet addresses of the nodes residing on each network segment

and then allow only the necessary traffic to pass through the switch. When a packet is received by the switch, the switch examines the destination and source hardware addresses and compares them to a table of network segments and addresses. If the segments are the same, the packet is dropped or "filtered"; if the segments are different, then the packet is "forwarded" to the proper segment. Additionally, switches prevent bad or misaligned packets from spreading by not forwarding them.

ROUTERS A router is specialized computer device connected to more than one network. It runs software that allows it to move data from one network to another. Routers operate at the network layer (OSI layer 3). The primary function of a router is to connect networks together and keep certain kinds of broadcast traffic under control. There are several companies that make routers: Cisco, Juniper, Nortel (Bay Networks), Redback, Lucent, 3Com, and HP just to name a few. Routers perform the following functions: o o o o

Restrict network broadcasts to the local LAN Act as the default gateway. Move data between networks Learn and advertise loop free paths between subnetworks.

A router is a device that forwards data packets along networks, and determines which way to send each data packet based on its current understanding of the state of its connected networks. Routers are typically connected to at least two networks, commonly two LANs or WANs or a LAN and its Internet Service Provider’s (ISPs) network. Routers are located at gateways, the places where two or more networks connect. Routers filter out network traffic by specific protocol rather than by packet address. Routers also divide networks logically instead of physically. An IP router can divide a network into various subnets so that only traffic destined for particular IP addresses can pass between segments. Network speed often decreases due to this type of intelligent forwarding. Such filtering takes more time than that exercised in a switch or bridge, which only looks at the Ethernet

address. However, in more complex networks, overall efficiency is improved by using routers.

MODEMS A modem is an communication device which allows your computer to communicate with other computers over a communications link. The modem's job is to convert your data into the format used on the communications connection and the remote modem converts that transmission back into data. Examples of modems include a standard fax/phone modem, a cable modem or a DSL modem or even a satellite modem. All modems perform what is called modulation to encode your data into the line signal and demodulation to decode it from the line signal. The term MODEM is short for Modulator/Demodulator. Modems come in many shapes and sizes but can be generally broken down into two categories, internal and external. As the names imply, an internal modem goes inside your computer into either an ISA or PCI slot. External modems are attached to the computer through some other connection but are physically outside the computer case. Modems perform modulation of the analog signal they put out, and demodulation of the signal they receive. They do this by mixing two signals in a digital signal processor and transmitting the analog result to the phone system as the electrical equivalent of sound. Here is a list of the protocols. The Bell protocols were developed by Bell Telephone prior to the government's breakup of that monopoly. The CCITT is an international standards body, which changed it's name later to the ITU (International Telecommunications Union). MODULATI ON

SPEED

IN USE

Bell 103

300 bps

Dead

Bell 212A

600 bps

Dead

CCITT V.21

900 bps

Rare

ITU V.22

1,200 bps

Rare

ITU V.29

9,600

Uncommon

ITU V.32

14,400

Uncommon

ITU V.32bis

28,800 downlink/uplink

Yes

ITU V.34

33,600 downlink 28,800 uplink

Yes

ITU V.90, K56flex & x2

56k downlink* ~28,800 Uplink

Yes

56k downlink* 33k Uplink

Yes

ITU V.92

NETWORK INTERFACE CARDS Network Interface Cards, commonly referred to as NICs, are used to connect a PC to a network. The NIC provides a physical connection between the networking cable and the computer's internal bus. Different computers have different bus architectures. PCI bus slots are most commonly found on 486/Pentium PCs and ISA expansion slots are commonly found on 386 and older PCs. NICs come in three basic varieties: 8-bit, 16-bit, and 32-bit. The larger the number of bits that can be transferred to the NIC, the faster the NIC can transfer data to the network cable. Most NICs are designed for a particular type of network, protocol, and medium, though some can serve multiple networks. Many NIC adapters comply with plug-and-play specifications. On these systems, NICs are automatically configured without user intervention, while on non-plug-and-play systems, configuration is done manually through a set-up program and/or DIP switches. Cards are available to support almost all networking standards. Fast Ethernet NICs are often 10/100 capable, and will automatically set to the appropriate speed. Gigabit Ethernet NICs are 10/100/1000 capable with auto negotiation depending on the user’s Ethernet speed. Full duplex networking is another option where a dedicated connection to a switch allows a NIC to operate at twice the speed.

DEVICE SERVERS A device server is “a specialized network-based hardware device designed to perform a single or specialized set of functions with client access independent of any operating system or proprietary protocol.” Device servers allow independence from proprietary protocols and the ability to meet a number of different functions. The RAID controller application discussed above is just one of many applications where device servers can be used to put any device or "machine" on the network. PCs have been used to network serial devices with some success. This, however, required the product with the serial port to have software able to run on the PC, and then have that application software allow the PC's networking software to access the application. This task equaled the problems of putting Ethernet on the serial device itself so it wasn’t a satisfactory solution. To be successful, a device server must provide a simple solution for networking a device and allow access to that device as if it were locally available through its serial port. Additionally, the device server should provide for the multitude of connection possibilities that a device may require on both the serial and network sides of a connection. Should the device be connected all the time to a specific host or PC? Are there multiple hosts or network devices that may want or need to connect to the newly-networked serial device? Are there specific requirements for an application which requires the serial device to reject a connection from the network under certain circumstances? The bottom line is a server must have both the flexibility to service a multitude of application requirements and be able to meet all the demands of those applications. Device servers are currently used in a wide variety of environments in which machinery, instruments, sensors and other discrete devices generate data that was previously inaccessible through enterprise networks. They are also used for security systems, point-of-sale applications, network management and many other applications where network access to a device is required. As device servers become more widely adopted and implemented into specialized applications, we can expect to see variations in size, mounting capabilities and enclosures. Device servers are also

available as embedded devices, capable of providing instant networking support for developers of future products where connectivity will be required. Print servers, terminal servers, remote access servers and network time servers are examples of device servers which are specialized for particular functions. Each of these types of servers has unique configuration attributes in hardware or software that help them to perform best in their particular arena. EXAMPLES •

External Device Servers

External device servers are stand-alone serial-towireless (802.11b) or serial-to-Ethernet device servers that can put just about any device with serial connectivity on the network in a matter of minutes so it can be managed remotely. External device servers provide the ability to remotely control, monitor, diagnose and troubleshoot equipment over a network or the Internet. By opting for a powerful external device with full network and web capabilities, companies are able to preserve their present equipment investments. Wireless (WiBox®): Providing a whole new level of flexibility and mobility, these devices allow users to connect devices that are inaccessible via cabling. Users can also add intelligence to their businesses by putting mobile devices, such as medical instruments or warehouse equipment, on networks. Security (SecureBox® SDS1100 and SDS2100): Ideal for protecting data such as business transactions, customer information, financial records, etc., these devices provide enhanced security for networked devices. Commercial (UDS-10, UDS100, UDS200, MSS4, MSS100, MSS485-T and CoBox-FL): These devices enable users to networkenable their existing equipment (such as POS devices, AV equipment, medical instruments, etc.) simply and cost-effectively, without the need for special software. Industrial (UDS-10-IAP, UDS100-IAP, CoBox-FL-IAP, XPress-DR and XPress-DR-IAP): For heavy-duty factory applications, Lantronix offers a full complement of industrial-strength external device servers designed for use with manufacturing, assembly and factory

automation protocols.

•

equipment.

All

models

support

Modbus

industrial

Embedded Device Servers

Embedded device servers integrate all the required hardware and software into a single embedded device. They use a device’s serial port to web-enable or network-enable products quickly and easily without the complexities of extensive hardware and software integration. Embedded device servers are typically plug-and-play solutions that operate independently of a PC and usually include a wireless or Ethernet connection, operating system, an embedded web server, a full TCP/IP protocol stack, and some sort of encryption for secure communications.

•

•

Module (XPort® and WiPort™): These devices allow users tonetwork-enable just about any electronic device with Ethernet and/or wireless connectivity.

•

Board-Level (Micro, Micro100, MSSLite, Mini, UDS-10B and UDS100B): Users can integrate networking capabilities onto the circuit boards of equipment like factory machinery, security systems and medical devices.

•

Single-Chip Solutions (DSTni-LX, DSTni-EX): These powerful, system-on-chip solutions help users address networking issues early in the design cycle to support the most popular embedded networking technologies.

Terminal Servers

Terminal servers are used to enable terminals to transmit data to and from host computers across LANs, without requiring each terminal to have its own direct connection. And while the terminal server's existence is still justified by convenience and cost considerations, its inherent intelligence provides many more advantages. Among these is enhanced remote monitoring and control. Terminal servers that support protocols like SNMP make networks easier to manage. Devices that are attached to a network through a server can be shared between terminals and hosts at both the local site and throughout the network. A single terminal may be connected to several hosts at the same time (in multiple concurrent sessions), and can switch between them. Terminal servers are also used to network devices that have only serial outputs. A connection between serial

ports on different servers is opened, allowing data to move between the two devices.

•

Print Servers

Print servers enable printers to be shared by other users on the network. Supporting either parallel and/or serial interfaces, a print server accepts print jobs from any person on the network using supported protocols and manages those jobs on each appropriate printer. The earliest print servers were external devices, which supported printing via parallel or serial ports on the device. Typically, only one or two protocols were supported. The latest generations of print servers support multiple protocols, have multiple parallel and serial connection options and, in some cases, are small enough to fit directly on the parallel port of the printer itself. Some printers have embedded or internal print servers. This design has an integral communication benefit between printer and print server, but lacks flexibility if the printer has physical problems. Print servers generally do not contain a large amount of memory; printers simply store information in a queue. When the desired printer becomes available, they allow the host to transmit the data to the appropriate printer port on the server. The print server can then simply queue and print each job in the order in which print requests are received, regardless of protocol used or the size of the job.

•

Console Servers

Console servers provide the flexibility of both standard and emergency remote access via attachment to the network or to a modem. Remote console management serves as a valuable tool to help maximize system uptime and system operating costs. Secured console servers provide familiar tools to leverage the console or emergency management port built into most serial devices, including servers, switches, routers, telecom equipment - anything in a rack - even if the network is down. They also supply complete in-

band and out-of-band local and remote management for the data center with tools such as telnet and SSH that help manage the performance and availability of critical business information systems.

KEYBOARDS A keyboard is a long flat device that has 102, 104 or more keys on it that is designed to allow a user to type data and feed it into the computer. Keyboards are attached to either the PS2 port or the USB port on your computer. Keyboards draw electrical power from the computer, detect your keystrokes and transmit the keystrokes back to the computer.

(a)Types of Keyboards WINDOWS KEYBOARDS Windows keyboards aren't all that special. You DO NOT need a Windows keyboard to work with a Windows computer. The Windows keyboard contains one special key that opens up the context menu in Windows. Most computer stores that sell keyboards call Windows keyboards 'standard keyboards', so like it or not, you often get a Windows keyboard whether you want it or not. MAC KEYBOARDS Yes, MacIntosh computers DO use a special keyboard. The Mac computer has the following special keys: 'Open Apple', 'Closed Apple', 'cmd', 'Option' and 'Alt' which are not found on other keyboards. Yes, other keyboards will work, but the keys won't be marked correctly and you may have to guess which key is which. MULTIMEDIA KEYBOARDS Multimedia is a term used to describe anything that combines audio, video and/or graphics. Multi-media keyboards often have a Pause/Play and volume buttons on them for controlling audio and video players configured on the computer. These keyboards don't work with all multimedia applications and you have to install special drivers just to get these keyboards to work. If you can't figure out how to change the volume on Windows media player or in WinAmp, you're probably going to have a hard time getting your spiffy new multimedia keyboard to work (since you must install the driver and installing drives is far more difficult than changing the volume setting). WIRELESS KEYBOARDS These are keyboards that do not use a physical wire to communicate with the computer. A small object is connected to the keyboard port (PS2 or USB port) and that small device communicates with the keyboard using a radio frequency. Problems with this technology: radio interfereance--someone else might be using the same keyboard you are or using a device that uses the same radio

frequencies. Second problem--a standard keyboard draws electricity from the computer through the port it is connected to. Wireless keyboards aren't plugged into the computer so they can't draw power. Therefore, all wireless keyboards (and mice) use batteries. When the batteries go dead, the keyboard goes dead and you can't use your computer.

MOUSE The computer mouse is a display-selection device used to 'point and click' on various things on your computer. The graphical user interface (GUI) often uses a graphical pointer to indicate the currently pointed-to location on the computer's display. The computer mouse is the conception of Douglas Engelbart, head of the self-founded Augmentation Research Center of Stanford University's Research Institute. Englebart designed and sketched out the concept for a mouse, performed studies on effictive interface devices (with ARPA research dollars) and Bill English built it. Not Apple, Not Xerox. It was the Advanced Research Projects Administration that brought you this cute little point-and-click thingy we are all so attached to. That's right, the United States Government funded the development of the mouse. Internally, a standard mouse consists of a roller ball a guide wheel and two sensor wheels. When the mouse is moved, the roller ball moves the sensor wheels. The sensor wheels detect this movement, calculate the ammount and send data to the computer to indicate how much and in which direction the digital pointer on the screen should move.

Types of Mice •

•

•

•

• •

STANDARD MOUSE This type of mouse comes in a two button and three button design. The two button mouse has a left mouse button and a right mouse button. WHEEL MICE Wheel mice have a rolling wheel between the two mouse buttons. Most graphical user interfaces (GUI) have scroll bars for areas where the content of the window exceeds the size of the display device. OPTICAL MICE This s a mouse that uses an optical sensor instead of a rolling ball. The advertised advantage is accuracy, but the real advantage is a clean mouse that never gets dirty as roller-based mice are prone to do. GAME MICE These are special mice that the mouse manufacturers claim are more accurate and which respond faster. These mice often have buttons that can be programmed to perform special functions within a game. WIRELESS MICE These mice use a radio frequency or infrared transmitter to communicate with a 'base station' that is connected to the computer. WIRELESS OPTICAL MICE

This is a mouse that combines the features of an optical and a wireless mouse.

COMPUTER SOFTWARE Software is a sets of instructions telling the computer how to process store and retreive data. Software is divided into two broad categories, Operating Systems and Applications.

OPERATING SYSTEMS Operating Systems run the computer and provide us with an interface with which to issue commands to the computer system. There are many varieties of operating systems. The differences between them stem from the hardware they were originally designed to run on and who engineers and manufactures the software. IBM Produced a number of operating systems including OS/360 for mainframes and OS/2 for desktop and personal computers. To sell their Personal Computers (PC's), IBM contracted with Microsoft to install a variation of "Quick and Dirty DOS" on all IBM PC's sold. This "Quick and Dirty DOS" became Microsoft DOS. Microsoft is the most well know manufacturer of operating systems today. Microsoft got their lead by making an exclusive deal with IBM in 1981 to include their variation of "Quick and Dirty DOS" operating system on every "IBM Personal Computer" microcomputer sold. Ever since that time, the vast majority of Intelprocessor based computers have shipped with Microsoft operating systems on them. The most recent version is Microsoft Windows XP.

Types of Operating Systems Operating systems can be divided into two broad categories. Those that are designed to run on workstations, PC's and microcomputers and those designed to run on massive computers often referred to as 'big iron', or mainframes. This section currently focuses on those operating systems that run on workstations and smaller, non-mainframe servers.

(a) Mainframe Operating Systems • • •

IBM System 370, 380, 390 AIX (IBM Unix) VMS (VAX)

•

DEC Operating System

(b)Computer Operating Systems UNIX • • • •

BSD HP-UX Solaris Tru64

LINUX • • • • •

Red Hat Suse Slackware YellowDog (Linux on MacIntosh) OS2/Warp

Microsoft Operating Systems • • • • • • •

MS-DOS (command-line) Windows 3.1 Windows 95 WIndows ME Windows NT Windows 2000 Windows XP

Apple Operating Systems • • • •

Mac Mac Mac Mac

OS OS OS OS

7 8 9 X

COMPUTER DEVICE DRIVERS Device drivers are small pieces of software that provide the operating system with easier access to the hardware. Drivers are installed for every device on the computer. Some devices such as disk drives, the processor and the chipset on the motherboard are shipped with the operating system (the operating system wouldn't be able to get up and running without them). Other drivers must be installed after installing a new device. The manufacturer of the device will provide drivers if the operating system does not support the device. Drivers for any given device will differ by operating system and version. This means that a video card manufacturer may not make a driver for the particular operating system you are using. This is especially the case when you have an old operating system and a brand new piece of hardware. Drivers are free, come with the hardware and usually can be

downloaded from the manufacturer's website as well. If your game crashes whenever it switches in and out of the game, you probably need to update your video drivers. If your computer's sound goes berzerk and then it crashes, you might need to update the sound drivers. Driver problems are more likely to be an issue on Windows based computers instead of MacIntosh computers. This is NOT because Windows computers are 'more complicated', it's because there are more CHOICES with Windows computers. There are many times more devices available to be installed on Windows-compatible computers. Microsoft also assumes you are smart enough to handle drivers yourself.