Thick net Coaxial A 1/2-inch thick cable that carries a signal up to 500 meters. A transceiver is used to make a physical connection with the thick net core.

Unshielded Twisted Pair-Twisted pair wiring, carries a signal up to 100 meters. This cable is susceptible to crosstalk.

Shielded Twisted Pair - Twisted pair wiring, carries a signal up to 100 meters. This cable has a foil or braided jacket around the wiring to help reduce crosstalk and to prevent electromagnetic interference.

Fiber-Optic This cable carries light pulse signals through a glass core at speeds of between 100 Mbps and 200,000 Mbps.

RJ-45 An 8-pin modular plug that is used to terminate UTP and STP cables. This connector can be used for both Ethernet and Token Ring applications.

AUl/DlX - Used to connect RG8 or RG11 (10BaseS) coaxial cable to another cabling •system or to a communications device such as a computer or router.

BNC - A 2-pin connector used to connect coaxial cables. It uses a twist lock mechanism, which prevents the cable from disconnecting.

ST (Straight Tip) -A frequently used fiber optic connector. It is a keyed BNC-style connector.

• Bus - Consists of a linear transmission medium (like Coaxial cable) that is terminated at both ends. Nodes attach directly to the bus. More difficult than a star to add, move or change layout. The entire bus is effected by a segment break.

• Mesh - Consists of a network where each device has a point-to-point connection to every other device on the network. Too complex and costly for networks with a large number of devices. Usually used on a network backbone.

• Ring - Provides a closed-loop transmission medium. Repeaters at each node connection repeat the signals. This is done to minimize any signal degradation. Used in older networks, and as high speed network backbones.

• Wireless - Uses radio transmission to connect nodes with a central wireless access point.

Access methods
An access method is a set of rules determining how network devices can communicate simultaneously on the same media, and how network devices respond when a data collision occurs.

• CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) - This methodology attempts to avoid collisions. An alert message notifies nodes of an impending transmission. Any collisions that occur will be during this alert sequence rather than during actual data transmission. Because the alert sequence is shorter than an actual data transmission, the retransmit of lengthy data is avoided.

• Token passing - A token is passed around the ring to which the computers are connected. The computer that grabs the token is able to send data over the network. When the token returns to its source with an acknowledgment from the destination, the source relinquishes the token and continues passing it around the ring, permitting another workstation to send data out on the network.

MAC address - Also known as the physical addresses, operates on the data link layer (MAC sublayer). Each address is a unique 12-digit hexadecimal ID number, which is hard coded to the network adapter by the factory, and is used by devices to direct packets to other devices.

To see your computer's Physical Address, type IPCONFIG /ALL at a command prompt.

• IP (Internet Protocol) - Provides packet routing and delivery between computer systems. It is a connection less protocol, so there is no guarantee of proper sequencing or even arrival at the destination.
• TCP (Transmission Control Protocol) -Provides connection-oriented communications. TCP provides guaranteed delivery, proper sequencing, and data integrity checks. If errors occur during transmission, TCP re-transmits the data.
• UDP (User Datagram Protocol)- Designed for connection less, unacknowledged communications.

• IPX/SPX - Fast protocol for small and large Novell networks. Also known in Windows as NWLink.

• IPX (Inlernetwork Packet Exchange) -Runs at the Network layer of the 051 model and provides connection less service.
• SPX (Sequenced Packet Exchange) -Runs at the Transport layer of the OSI model and provides connection-oriented services.

• NetBEUI - Microsoft protocol designed for small LANs. Not compatible with UNIX networks.

IP - Internet Protocol addressing is the standard for data packet delivery over the Internet. IP also defines how data packets can be routed across the network to their destinations. Routers forward each packet across the Internet based on its destination IP address. Each device attached to the Internet or any IP network must have a unique IP address. IP operates on the OSI Network Layer because it is responsible for network addressing.

TCP - Transmission Control Protocol is connection-based Internet protocol responsible for breaking data into packets, which the IP protocol sends over the network. This protocol provides a reliable, sequenced communication stream for network communication. TCP operates on the OSI Transport Layer because it is responsible for data transport.

UDP - User Datagram Protocol runs on top of IP and is used as an alternative to TCP. UDP does not, however, provide any error checking for guaranteeing packet delivery. Because UDP is not as complex as TCP, it is also faster. UDP is a connectionless transport protocol. UDP operates on the OSI Transport Layer because it is responsible for data transport.

FTP - File Transfer Protocol, is used for exchanging files in a TCP/IP environment and is implemented at the application layer of the OSI model. FTP operates on the OSI Application Layer because it is operates as an application (FTP server or FTP client software)

TFTP - Trivial File Transfer Protocol is a file transfer protocol that transfers files to and from a remote computer running the TFTP service. TFTP was designed with less functions than FTP. TFTP is also on the OSI application layer.

SMTP - Simple Mail Transfer Protocol, is used to transfer messages between two remote computers. It is used on the Internet, and is part of the TCP/IP protocol stack. SMTP operates on the OSI Application Layer because it is operates as a server service.

POP3 - Post Office Protocol, used to retrieve e-mail from a mail server. POP is used on Email servers as a service that hold users messages, and allows users to connect, authenticate, and receive messages. This puts POP3 on the OSI Application layer.

HTTP - Hypertext Transfer Protocol is the underlying protocol for the World Wide Web. HTTP defines how all resources on the web are transferred and what action web servers and browsers should take in response to commands. This puts HTTP on the OSI Application layer.

HTTPS / SSL - HTTPS is HTTP using a Secure Socket Layer (SSL). A secure socket layer is an encryption protocol invoked on a Web server that provides secure web connections. Most implementations of the HTTPS protocol involve online purchasing or the exchange of private information. Like HTTP, HTTPS and SSL are on the OSI Application layer. 

Telnet - Short for Telecommunication Network, a virtual terminal protocol allowing a user logged on to one TCP/IP host to access other hosts on the network. Telnet is on the OSI Application layer. 

ICMP - Internet Control Message Protocol is a maintenance protocol in the TCP/IP suite, required in every TCP/IP implementation, that allows two nodes on an IP network to share IP status and error information. ICMP is used by the PING and TRACERT utilities to determine the readability of a remote system.

ARP - Address Resolution Protocol, is a TCP/IP protocol used to convert an IP address (network layer) into a physical address (Data Link layer). 

lPSec - Provides authentication and encryption over the Internet. Operates at the OSI Network layer.

L2TP- Used with IPSec to create Virtual Private Network (VPN) connections.

Kerberos - Provide strong authentication for client/server applications by using secret-key cryptography. Kerberos is used to authenticate user and computer accounts in Microsoft Active Directory networks.

Remote access protocols
These protocols are used to establish dial-up and VPN connections.

• SLIP (Serial Line IP) - Provides dial-up Communications, but is unable to simultaneously transfer multiple protocols.
• PPP (Point-to-Point Protocol) - Performs dynamic lP addressing, multi-protocol support, password login, and error control.

• PPTP (Point-to-Point funneling Protocol) - Provides a means to secure client connections over the Internet through account authentication. Through Virtual Private Networks (VPNs), secure communications are supported over standard Internet connections.
• L2TP (Layer Two Tunneling Protocol) - Provides a means to secure client connections over the Internet through certificate authentication. Through Virtual Private Networks (VPNs), secure communications are supported over standard Internet connections.

• RAS (Remote Access Server) - A computer with one or more modems installed to facilitate remote connections to a network.

Modems - A peripheral device that permits a personal computer, microcomputer, or main­frame to receive and transmit data in digital format across voice-oriented communications links, such as telephone lines.

Segment - The portion of the network on either side of a router.

Packet switching networks (term) Packets are relayed across networks along the best route available.

• X.25 - Designed to connect remote terminals to mainframe host systems. Very slow due to constant error-checking.

• Frame Relay - Point-to-point system that uses digital leased lines. Requires frame relay capable bridge or router for transmission.

• AIM - Advanced implementation of packet switching. Transmits at speeds of 1 55 Mbps to 622 Mbps with capabilities of higher speeds. Uses switches as multiplexers to permit several computers to simultaneously transmit data on a network.

• ISDN - Transmits at 1 28k/sec. Has three data channels: two B channels @ 64k/sec and one D channel @ 1 6k/sec. The B channels carry data, while the D channel performs link management and signaling.

• FDDI - 100 Mbps token-passing ring network that uses fiber-optic media. Uses a dual-ring topology for redundancy and in case of ring failure. Each ring is capable of connecting 500 computers over 100 kilometers (62 miles). Can be used as a network backbone.

• Private network - A network that is guarded by some form of firewall.

Typical Network:

• Ping - Will send ICMP echo packets to verify connections to a remote host (or test the local TCP/IP installation if using the loopback address).

• Arp - Used to gather hardware addresses of local hosts and the default gateway, you can view the ARP cache and check for invalid or duplicate entries.

• Netstat - This command displays protocol statistics and gets information about TCP/IP connections.

• Nbtstat - Reports statistics and connections for NetBIOS over TCP/IP. Used for DNS and WINS name resolution, local cache Iookup, and referral to LMHOSTS and HOSTS files. Troubleshoots name-to-address mappings.

• lpconfig - command line utility utilities display IP-addressing information for the local computer.

• Nslookup - A graphical version of IPCONFIG available in Windows 95/98.

• Nslookup - Queries a name server to determine which name resolves to which IP address.

• Media tester - Large as network hand tools go, this tests network media to be sure it meets manufacturer’s requirements.

• Tone generator - Software that will play sounds, such as sine, triangle, impulse, or white noise, using a computer’s sound card. Ideal tool for testing sound on a computer.

• Optical tester - A hand-held device that measures optical parameters.

• Time Domain Reflectometer (TDR) - A sophisticated tool used to find a break in the middle of a cable.

• Loopback adapter - Transmits a signal across a medium while the sending device waits for the return of the signal.

• Screwdrivers - Helpful for opening systems, removing and replacing boards, and attaching cables.

• Standard pliers - Necessary for certain types of clips.

• Long-nose (needle-nose) pliers - Helpful for pulling or replacing jumpers. Also used for straightening bent pins on DIP packages.

• Nut drivers (or a small socket set) - Necessary for hex-topped screws.

• Tweezers - Useful for picking up small items that you have dropped.

• Torx (spline) drivers - Necessary for getting into some system enclosures, including many Macintosh and some Compaq systems.

• Multimeter (VoIt-Ohm-Meter) - Useful for checking power supply voltages.

• Full backup - This will back up all of the data on the server. File archive bits will be reset.

• Incremental backup - This will back up any data that has changed after the last backup (full or incremental). File archive bits will be reset.

• Differential backup - This will back up any data that has changed after the last full backup. File archive bits will not be reset.

Backup tapes should be stored in off-site locations, so that the servers and backups cannot be destroyed by the same disaster.

To upgrade a network to 100 Mbps Ethernet, you must do all of the following:

• Upgrade all hubs to switches or 100 Mbps hubs.

• Upgrade the wiring to CAT 5 UTP/STP.

• Upgrade all network cards to 100 Mbps.

Redundant Array of Independent Disks

A set of specifications describing hard disk fault tolerance configurations.

• RAID Level 0 - Disk striping without parity. Data is distributed across a series of drives. This is not a fault tolerance specification. It increases the speed of disk I/O.

• RAID Level 1 - Mirror sets (including duplexing). Data is mirrored across two disk drives. Mirroring a pair of disks reduces the total disk storage by one half.

• RAID Level 5 - Stripe sets with parity. Data and parity blocks are spread across all drives in the array. These eliminate the dedicated parity drive and thereby you can read and write multiple transactions to be performed in parallel.

• What will the company need if disaster strikes?
• What departments have priority for getting back online first?
• How much of the data is at risk?
• What is the minimum and maximum downtime you can afford?
• What is your cost per minute if your system is down?
• Are there redundant networks that can replace your failed system?
• Would a clustered environment minimize your risk?

• Always keep a set of the data OFFSITE.
• Establish an alternative site (cold site, offsite new building, or maybe even a different state).
• Prepare a special group of people to work at your alternative site and devise a plan to get them to the new site from the disaster site. Consider a rotating schedule of different technical staff members.
• Decide which products are needed to support the recovery process, acquire them, and train in their use.
• Some disaster recovery scenarios even include having a complete duplicate of your server standing by in case of disaster.
• Simple items such as a UPS can save you a lot of headaches, such as in the case of power failures.
• Disaster-recovery management should always begin with a planning meeting.