
12
Internetwork Packet Exchange
Internetwork Packet Exchange
103-000176-001
August 29, 2001
Novell Confidential
Manual
99a
38
July 17, 2001
Figure 1
How NetWare Protocols Correspond to the OSI Reference Model
The higher-level protocols (NetBIOS, SAP, NCP, SPX, NLSP, and RIP) rely
on the MAC protocols and IPX to handle lower-level communications, such
as node addressing. With the exception of NetBIOS, NCP, and SPX, each of
these protocols plays a role in the operation of IPX routing.
The IPX Protocol
Novell adapted IPX from the Xerox* Network System (XNS*) Internet
Datagram Protocol (IDP). IPX is a connectionless datagram protocol.
Connectionless
means that when a process running on a particular node uses
IPX to communicate with a process on another node, no connection between
the two nodes is established. Thus, IPX packets are addressed and sent to their
destinations, but there is no guarantee or verification of successful delivery.
Any packet acknowledgment or connection control is provided by protocols
above IPX, such as SPX.
Datagram
means that each packet is treated as an
individual entity, having no logical or sequential relation to any other packet.
As shown in
, IPX operates at the OSI Network layer. As a Network-
layer protocol, IPX addresses and routes packets from one location to another
on an IPX internetwork. IPX bases its routing decisions on the address fields
in its header and on the information it receives from RIP or NLSP. IPX uses
this information to forward packets to their destination node or to the next
router providing a path to the destination node.
IPX
SPX
NCP
NetBIOS
NetBIOS
Applications
NLSP
RIP
SAP
NetWare
Applications
MAC Protocols
(Ethernet, token ring, ARCnet*)
Application
Presentation
Session
Transport
Network
Data Link
Physical