Operation Manual

123 NT/MPRI – Glossary
SPX (Sequenced Packet Exchange)
A protocol that enables two workstations or applications to communi-
cate over a network. Like TCP, SPX is located at Layer 4 (Transport Lay-
er) of the OSI reference model and ensures secure end-to-end commu-
nication. SPX uses NetWare IPX for data transmission. SPX ensures that
the sequence of messages in the packet stream remains the same.
TCP (Transmission Control Protocol)
TCP is designed for the implementation of packet-switched networks. It
builds immediately on the Internet Protocol (IP) and provides virtual
connection services for correctly sequenced, secure transmission of
user data. It ensures a reliable connection between two communica-
tions partners. TCP is published as RFC 793.
TCP/IP Addresses
TCP/IP addressing is a permanent part of the Internet Protocol (IP).
Internet addresses are written using decimal, octal or hexadecimal rep-
resentation. The NT/MPRI uses “dotted decimal” notation, in which the
decimal values of the individual bytes are separated from one another
by periods. The entire set of Internet addresses, the address space, is
divided into classes (A, B, C, D and E). Of these five address classes,
only the first three are used. These classes are characterized as fol-
lows:
Characteristics of IP address classes
Each IP address consists of two elements: the network address and the
host or computer address. The sizes of these two components are vari-
able; they are determined by the first four bits (of the first byte) of an IP
address.
l Class A addresses consist of a one-byte network address and a
three-byte computer address
Class Characteristics Network address,
decimal value
Class A address few networks, many net-
work nodes
0-127
Class B address medium distribution of net-
works and network nodes
128-191
Class C address many networks, few net-
work nodes
192-223
ntmpri-e.book Seite 123 Donnerstag, 28. Februar 2002 11:26 11