%$Id: HEL91012.tex,v 1.1 1992/01/24 16:56:24 doc Exp $
%GLOSSARY FOR THE ETHERNET GUIDE, MARCH 1991.
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%\title{{\bf Glossary of Terms}}
%\author{Jessica King}
%\date{January 1991}
\pagestyle{plain}
%\begin{document}
%\maketitle
%\pagenumbering{arabic}
\section{\bf Glossary}

This glossary is intended to act as a quick reminder to
experienced readers and to help less experienced readers to follow
and understand the description of inter process communication 
in this Helios Ethernet package.

\begin{description}
\item {\bf Address family}

Named groups, {\it domains}, using common address 
formats \newline ({\tt AF\_HELIOS}, {\tt AF\_UNIX}, {\tt AF\_INET}, etc). 

\item {\bf ARP} 

Address Resolution Protocol - resolves Internet addresses
into Ethernet \newline hardware addresses.

\item {\bf ARPA}

Advanced Research Project Agency (part of US DoD) also
known as \newline DARPA, the Defense Advanced Research Project Agency.
   
\item {\bf ARPANET}

Network of computers (1969-1988), since
superseded by Internet, supported by DoD's ARPA agency 
and run internationally at universities and other research 
establishments.
   
\item {\bf Bandwidth}

Data transfer rate of a device.

\item {\bf Broadcast}

Sending messages through the network to all hosts.

\item {\bf BSD}

Berkeley Software Distribution 
   
\item {\bf Client}

User or application requesting services from the network.
    The client, therefore, initiates a connection.

   \item {\bf Collision detection}

Detection of clashing message transmissions,
    where hosts attempt to transmit simultaneously over the same
    connection. If a host detects that such a collision has occurred, it must
    wait and then repeat the failed transmission.

   \item {\bf Connection mode}

Transfer mode whereby information is transmitted
    by way of an established connection in a reliable, sequenced manner.
    ({\it See also Sockets and Streams.})

   \item {\bf Connectionless mode}

 Transfer mode whereby information is divided
    into self-contained units and transmitted unreliably in 
    unsequenced order. ({\it See also Datagram.})

   \item {\bf Daemon}

Common Unix name for server.

   \item {\bf DARPA}

{\it See ARPA.} 

   \item {\bf Datagram}

A unit of data transmitted between two tasks
    using the connectionless mode of communication. 
    It is unreliable, unsequenced and it allows messages to be duplicated. 
    It does, however, retain any internal record boundaries.

   \item {\bf DoD}

The United States of America's Department of Defense, the original
    source of funds for research into interprocessor communication.

   \item {\bf Domain}

A communications domain includes a common address structure
    and protocol for tasks that are communicating by way of sockets. HELIOS
    domain sockets have Helios pathnames. Sockets in the same domain
    can easily exchange data; sockets in different domains can only communicate
    if some translation process is implemented.

   \item {\bf Ethernet}

IEEE standard 802.3. 

   \item {\bf FTP}

File Transfer Protocol

   \item {\bf Host}

 A processor that requests services ({\it see Client}) 
    or provides services. A transport user.

   \item {\bf Internet}

{See also ARPANET, IP}

   \item {\bf IP}

Internet Protocol

   \item {\bf IP Address}

Internet Protocol address. In order for packets
    to find their correct destination, the IP protocol on the source
    host attaches its address. This address is made up of three numbers:
    a network number,
    which is externally assigned by the official Network
    Information Center,
    and a subnetwork number and a host number, both of which are 
    assigned locally by the network administrator. The total address is
    32-bits wide, divided into four 8-bit fields, called {\em octets}.
    Each octet field is divided from the next by a decimal point. Each byte
    of the address can be represented by a decimal number, in the range
    0-255. 

   \item {\bf IPC}

Inter Process Communication

   \item {\bf Layers}

 There are seven layers in the International Standards Division
   (ISO) Open Systems Interconnection (OSI) reference model, listed
   here from the lowest to the highest level: Layer 1, {\bf Physical}
   (raw data transmission over some sort of data communications medium, such 
   as an interface board or cable); Layer 2, {\bf Data Link} (handles the exchange
   of data between the network layers, detecting and correcting errors
   in physical transmission); Layer 3, {\bf Network}
   (manages the network, routing data exchanges for transport layer -
   IP works at this level);
   Layer 4, {\bf Transport} (provides data transfer services for session
   layer by TCP); Layer 5, {\bf Session} (provides services for presentation
   layer, helping with data exchange management); Layer 6, {\bf Presentation}
   (manages information representation for applications layer); Layer 7,
   {\bf Application} (serves communicating applications, handling their
   information exchange). Notice that each level provides services for the
   next level up. The level above therefore need not concern itself with 
   the protocol used to provide its services.

   \item {\bf OOB}

Out Of Band.

   \item {\bf OSI Reference Model}

 {\it See Layers.}

   \item {\bf Ping}

Command that is useful for testing and debugging networks:
    it sends a message to the specified host and then waits for a reply. It
    then reports back success or failure. A full description of {\tt ping}
    can be found in the reference section of this manual. 

   \item {\bf Port}

 Transport user id (acts a bit like a phone number!) Certain
    port numbers are restricted:

   \item {\bf Protocol}

A formal set of rules and conventions that
    govern and regulate the exchange of information between communicating
    entities.

   \item {\bf Protocol family}

Named groups of protocols; for example, {\tt PF\_INET}
    for Internet protocol family.

   \item {\bf Pseudo terminal}
 
   \item {\bf Raw}

A raw socket provides access to the underlying communications
    protocols. They are of little interest to the general user.

   \item {\bf RCP}

Remote Copy Protocol. {\it See} {\tt rcp} 
    {\it in the command reference section of this manual}.

   \item {\bf RDM}

Reliably Delivered Message.

   \item {\bf Sequenced packet stream}

   \item {\bf Server} 

Process supplying some form of service to the network.
    (Can also refer to opposite end of communication link from client.)

   \item {\bf Socket}

 An endpoint of communication to which a name can be bound.
    Sockets can be: stream sockets, datagram sockets, raw sockets, etc.
    A pair of connected stream sockets look and act like a pipe. A datagram
    socket (type {\tt SOCK\_DGRAM}), unlike a stream socket 
    (type {\tt SOCK\_STREAM}), is not sequenced or reliable. It may
    be duplicated and delivered in an order different from that which was
    originally sent. Unlike a stream socket, though, it does retain any
    record boundaries. Raw sockets (type {\tt SOCK\_RAW})
    depend on the underlying protocol;
    they are not intended for the casual user. Sequenced packet sockets
    (type {\tt SOCK\_SEQPACKET})
    are like stream sockets, except that they preserve record boundaries, 
    whereas RDM sockets (type {\tt SOCK\_RDM})
    are like datagram sockets, except that they undertake to 
    deliver messages reliably, like stream sockets.

   \item {\bf Stream}

 Sequenced data message, with no record boundaries, that
    flows reliably over an established inter-task connection. {\it See Socket}.

   \item {\bf TCP}

 Transmission Control Protocol

   \item {\bf TCP/IP}

 Transmission Control Protocol and Internet Protocol

   \item {\bf Telnet}

 The standard TCP/IP remote login protocol. It allows you
    to use your terminal as if it were attached to a machine elsewhere on
    the network. {\it See} {\tt telnet} 
    {\it in the command reference section of this manual}.

   \item {\bf Trailer}

 Method of sending information over Ethernet

   \item {\bf Transport layer}

 The ISO layer that supports communication between
    users by carrying out any data transfer services: it receives 
    data from the network layer, carries out necessary services
    and then passes the data on to the session layer. {\it See also Layer.}
\end{description}
%\end{document}
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