Network Information

General Tech

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Network Information

ARP - Address Resolution Protocol - converts 32-bit addresses into physical network addresses like 48-bit Ethernet addresses
ATM - Asynchronous Transfer Mode - a type of switching technology in which the switches are small, fixed-length cells containing data.
bridges - devices that filter packets between LANs by making a simple forward/don't forward decision on each packet they receive from any of the networks they are connected to.
CSMA/CD - Carrier Sense Multiple Access with Collision Detection - access method that is used by stations connected to an Ethernet LAN, in this method, each station contends for access to the shared medium.
Ethernet - the most widely used LAN technology, accounting for approximately 80 percent of all network connections, standard Ethernet runs at 10 million bits per second (10 Mbps) and balances speed, price, ease of installation, and availability. The rules of Ethernet are defined by the IEEE 802.3 specification, the most popular form of Ethernet is 10BASE-T.
Fast Ethernet - an extension of 10 Mbps Ethernet, Fast Ethernet runs at 100 million bits per second (Mbps). The rules of Fast Ethernet are defined by the IEEE 802.3u specification. Because they use the same protocol, data can be moved between Ethernet and Fast Ethernet without protocol translation.
FDDI - Fiber Distributed Data Interface - LAN technology that runs at 100 Mbps, a much higher data rate than Ethernet or Token Ring. Originally, FDDI networks required fiber optic cable, but today they can also be run on UTP.
FTP - File Transfer Protocol - permits files to be transferred from one computer to another using a TCP connection. TFTP (Trivial File Transfer Protocol) transfers file data over a UDP protocol instead.
ICMP - Internet Control Message Protocol - allows IP routers to send error and control messages to other IP routers and hosts. ICMP messages travel in the data fields of IP datagrams and are a required part of all IP implementations.
IGMP - Internet Group Management Protocol - permits IP datagrams to be broadcast, or multicast, to computers that belong to multicast groups.
intelligent hubs - wiring concentrators that can be monitored and managed by network operators.
IP - Internet Protocol - a low-level protocol that routes packets of data across separate networks tied together by routers to form the Internet or an intranet. Data travels in packets called IP datagrams.
LAN internetwork - connecting disparate and geographically dispersed LANs together to form an enterprise system.
LAN - Local Area Network - a high-speed communications system designed to link computers and other data processing devices together within a small geographic area such as a workgroup, department, or a single floor of a multistory building.
manageable hubs - another definition for intelligent hubs. Each of the ports on the managed hub can be configured, monitored, and enabled or disabled by a network operator from a hub management console.
modular hubs - a hub that starts with a chassis, or card cage, with multiple card slots, each of which can accept a communications card, or module. Each module acts like a standalone hub; when the communications modules are placed in the card slots in the chassis, they connect to a high-speed communications backplane that links them together so that a station connected to a port on one module can easily communicate with a station on another module.
MAU - Multistation Access Unit - a Token Ring wiring concentrator that connects each station in a Token Ring LAN.
NIC - Network Interface Card - the physical connection from the computer to the network is made by putting a NIC inside the computer and connecting it to the shared cable.
OSI - Open Systems Interconnect reference model - a communications model developed by the International Standards Organization (ISO) to define all of the services a LAN should provide. This model defines seven layers, each of which provides a subset of all of the LAN services. This layered approach allows small groups of related services to be implemented in a modular fashion that makes designing network software much more flexible.
packet - in a shared media network, when one stations wishes to send a message to another station, it uses the network software to put the message in an "envelope." This envelope is called a packet.
RARP - Reverse Address Resolution Protocol - converts physical network addresses into IP addresses.
repeaters - devices that amplify and regenerate signals so they can travel farther on a cable. The term "repeater" is often used to describe hubs.
ring topology - a network whose nodes are connected in a continuous loop.
routers - these are more complex internetworking devices that are also typically more expensive than bridges. They use Network Layer Protocol Information within each packet to route it from one LAN to another.
segmentation - the act of improving network performance by dividing a single large network into multiple smaller, less congested LANs while maintaining connectivity between them. Switches offer an effective segmentation tool by providing each port with dedicated bandwith without requiring users to change any existing equipment such as NICs, hubs, wiring, or any routers or bridges that are currently in place. Switches can also support numerous transmissions simultaneously.
SMTP - Simple Network Management Protocol - specifies the format of messages that an SMTP client on one computer can use to send electronic mail to an SMTP server on another computer.
stackable hubs - hubs that look and act like standalone hubs except that several of them can be "stacked" or connected together, usually by short lengths of cable. When they are linked together they can be managed as a single unit.
standalone hubs - single box-level hubs with a number of ports. Standalone hubs usually include some method of linking them to other standalone hubs -- either by connecting them together with a length of 10BASE5 coaxial cable or cascading them using twisted pair between individual ports on each hub.
STP - Shielded Twisted Pair - cable that has shielding around it to provide more protection against electromagnetic interference (EMI).
switches - a device that links several separate LANs and provides packet filtering between them. A LAN switch is a device with multiple ports, each of which can support an entire Ethernet or Token Ring LAN.
token - a signal used in a Token Ring network that coordinates the transmission of data among the nodes. The token travels around the network, and a node can transmit data only when it has a token.
TCP - Transmission Control Protocol - a connection-oriented protocol that transmits data in byte streams. Data is transmitted in packets called TCP segments, which contain TCP headers and data. TCP is a "reliable" protocol because it uses checksums to verify data integrity and handshaking to make sure transmitted data is received intact.
10BASE-T - the specification for running Ethernet on UTP. This stands for 10 Mbps, baseband signaling (the signaling method used by Ethernet networks), over twisted pair cable.
10BASE5 - an Ethernet specification that uses a thick coaxial cable. 10BASE5 is seldom installed in new Ethernet networks today.
10BASE2 - an Ethernet specification that uses a thin coaxial cable medium. 10BASE2 is only used in very small office networks.
UTP - Unshielded Twisted Pair - UTP cable is similar to telephone cable but has somewhat more stringent specifications regarding its susceptibility to outside EMI than common telephone wire. UTP is used much more often than STP.
Token Ring - a major LAN technology in use today. Token Ring rules are defined in the IEEE 802.5 specification. Like Ethernet, the Token Ring protocol provides services at the Physical and Data Link Layers of the OSI model. Token Ring networks can be run at two different data rates, 4 Mbps or 16 Mbps.
UDP - User Datagram Protocol - a connectionless protocol that transmits data in packets called UDP datagrams. UDP is an "unreliable" protocol because the sender receives no information indicating whether a datagram was actually received. An example of an UDP application is SNMP (Simple Network Management Protocol).

Network Comparison
Cable Type	Speed	Connector	Faults	Topology
FDDI (Fast Ethernet)	100 Mbps (million bits per second)			collapsed ring or physical star
10-Base-T (UTP - unshielded twisted pair)	10 Mbps	RJ-45 (telephone type)	fault doesn't affect all nodes	star - nodes connected to hub (concentrator)
10-Base2 (thin coaxial cable - thinnet)		BNC (circular plug)	fault affects all nodes	bus (straight line)
10-Base5 (thick coaxial cable)		AUI (15 pin)
Token Ring	4 Mbps or 16 Mbps			token ring

ISO/OSI - TCP/IP Mapping
ISO/OSI	TCP/IP
Application layer	/\
Presentation layer	Network Application (like FTP or Telnet)
Session layer	\/
Transport layer	TCP or UDP
Network layer	IP
Data-link layer	ARP <-->Network Interface Card <-->RARP
Physical layer	Network cabling