NetWare Client for DOS and MS Windows User Guide

2-12
Understanding the NetWare Client Software
The NetWare Protocols and Transports
The targeting ability of IPXODI is important but, by itself, does not
guarantee successful delivery of a data transmission.
IPXODI transmits data packets as datagrams (self-contained packages that
move independently from source to destination) and, therefore, can deliver
the packets only on a best-effort basis. Delivery is guaranteed only when
using the SPX protocol.
SPX Protocol
SPX (Sequenced Packet Exchange) is a protocol within IPXODI that is
derived from the Novell IPX protocol using the Xerox Sequenced Packet
protocol. It enhances IPX by supervising data sent out across the network.
SPX verifies and acknowledges successful packet delivery to any network
destination by requesting a verification that the data was received.
Within this verification must be a value that matches the value calculated
from the data before transmission. So SPX ensures not only that the data
packet arrived, but that it arrived intact.
SPX can track a single data transmission or data transmissions consisting of
a series of separate packets. If an acknowledgment request brings no
response within a specified time, SPX retransmits it.
After a reasonable number of retransmissions fail to return a positive
acknowledgment, SPX assumes the connection has failed and warns the
operator of the failure.
TCP/IP Protocol
The Novell Transmission Control Protocol/Internet Protocol (TCP/IP)
software (the TCP/IP.EXE file) provides communication between NetWare
(IPX) networks across an IP internet that does not directly support IPX. This
is known as IPX/IP tunneling.
NetWare TCP/IP also provides a transport interface for higher-level
networking services. This interface provides client workstations data-
communication services to the Network File System (NFS), and third-party
applications supporting the 4.3 BSD UNIX® socket interface, the AT&T*