Improving Network Performance: Glossary

Improving Network Performance: Glossary Glossary

Baud:

Used to describe the speed of a modem. The Baud rate of a modem describes how many bits it can send each second. Some of those bits, however, are used for error checking purposes. This means that instead of one byte taking eight bits, a byte could take from nine to eleven bits. These bits include: One parity bit, eight data bits, zero or one start bits and zero or one stop bits. (Seyer 2)

Broadcasting:

"Broadcasting is a protocol which allows a process to send one message out, and allow all of the other processes to read that single message". (qtd. in Gossweiler 4) The advantage of broadcast messages over multicast messages is that only one message has to be sent out instead of one message to each node. See also: Multicasting.

Connectionless:

No connection or pipe is established between two computers. (Novell 2-1)

Datagram:

"Each packet is treated as an individual entity, having no logical or sequential relation to any other packet." (qtd. in Novell 2-1)

Dead Reckoning:

A method of reducing the number of packets sent from a constantly moving object. If an object does not stray from it’s current course, a packet need not be sent.

Frame:

A frame is one completed display of the simulated environment. After a frame is drawn, input is taken and a new frame is calculated.

Heartbeat:

Often, to combat unreliable networks and to quickly inform new players about the state of the simulation, each player periodically sends out a heartbeat, informing everyone of its status. (Gossweiler 6) The name "Heartbeat" comes from a metaphor of biological heart beats. They are used by other players in the simulation to determine whether a player is still active (or alive). See also: Reliability.

IPX:

The heart of Novell’s Ethernet network system. "Novell adapted IPX from Xerox Network System’s (XNS) Internet Datagram Protocol (IDP)." (qtd. in Novell 2-1) While it was intended to be compatible with Xerox’s system, IPX has evolved to the point where the two hardware systems do not understand each other. "IPX is a datagram, connectionless protocol that does not require an acknowledgment for each packet sent." (qtd. In Novell 1-3) The tasks performed by the IPX protocol are: addressing, routing, and switching packets to move individual packets from one location to another on a network. IPX also serves as a base for many other protocols to operate on top of, because IPX provides a common interface to the underlying network hardware. NetBIOS, SP, NCP, SAP and RIP are all built on top of IPX. (Novell 1-2) See also: Connectionless, Datagram, Packet, Routing, Socket Number.

Multicasting:

Multicasting is the opposite of broadcasting. When sending a packet out on the network, a packet is sent to each computer playing on the network. This has a big drawback though. Whereas with broadcasting each player sends out one update, with multicasting each player has to send a message to each other player in the simulation. See also: Broadcasting.

Network:

A network is a collection of computers connected together that allows the computers to share information and resources. There are many different kinds of networks. The two most common are LANs (Local Area Network) and WANs (Wide Area Network). (Bishop 2) Networks can be connected to other networks, which allows them to exchange information with each other. One reason the Internet grew so rapidly (before it became popular) is that colleges would connect their individual LANs together to share information.

There are five building blocks to networks. Terminals, transmission links, nodes and switches, transmission methods and procedures, and architecture and standards. (Bishop 1) These all combine to form a uniform easily accessible interface that allows communications to take place in a transparent manner.

Node:

A computer on a network.

Packet:

One package of information. A packet is the lowest form of network communication between computers. The way that the packet is transmitted and the actual layout of the packet all depend on the underlying protocol used to send the packet. The maximum packet size for an IPX packet is 576 bytes. (Novell 2-2) See also: Protocol.

Process / Thread:

A process (also known as a thread) is one active application running on a computer. Under multitasking environments, many different processes may be executing at the same time and must share the resources of the computer.

Protocol:

A protocol is a definition of how communications over a network will operate. It specifies everything from the voltage levels on the wires, to the format of the data packets. Two important issues that a protocol must address are reliability and communications speed. (Gossweiler 2) There are many different protocols available on Novell networks. The base protocol is IPX, which provides a consistent interface to the hardware. Built on top of IPX, protocols like SPX, and NetBIOS, provide options to the programmer such as speed and reliability. Some protocols, for example: SAP, NCP, and RIP are special purpose protocols meant for doing one specific job. The details of each protocol are unnecessary. See also: IPX, Network, Routing, SPX.

Real Time:

A real time program does all calculations while the current frame is being updated and manipulates a large amount of data. They typically have large amounts of computations and have to be well organized and highly optimized. An example would be a three dimensional simulator. The opposite would be a word processor or spreadsheet, where all of the data is incrementally processed.

Reliability:

The reliability of a network can be measured by one factor. The number of packets lost in a time period. If two or more packets are sent out on the network at the same time, they crash together and either destroy each other, or destroy the data held in the packets. Thus, protocols that guarantee reliability must make sure that a packet was received, and if not, it must send it again. The two main factors that affect reliability are the number of messages sent, and how complex the network is. (Gossweiler 2)

Routing:

Moving a packet from one segment of a network onto another. Also used to move a packet from one network to another, connected network.

Socket Number:

A socket number is a sort of mail slot on a network terminal. Since many threads can be running on a computer at one time, and many of them accessing the network, some method must be used to distinguish the different destinations. Every computer on a network has a network address, and every application running on that computer has a set of socket numbers that it uses. (Novell 2-1)

SPX:

A common protocol used on Novell networks. It provides guaranteed in-order delivery of packets. To accomplish this, it runs on top of IPX and adds a layer of error correction and resend mechanisms. SPX typically runs ten times slower that IPX. See also: IPX, Protocols.