This article describes the basic components in the Microsoft NWLINK IPX/SPX Compatible Transport.
The following table defines some components included in the NWLINK IPX/SPX Compatible Transport protocol suite.
Component Definition
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IPX Internet Packet eXchange (IPX) is a connectionless, routable
protocol. It provides no session services by itself.
IPX Packet An IPX packet contains fields for Checksum, Length, Transport
Control (hop count), Packet Type, Destination Address, and
Source Address.
IPX Address An IPX address contains Network, Node, and Socket.
Network The External network numbers are defined per network segment.
The Internal network numbers are defined per server for any
server which requires one. All network numbers, Internal or
External, must be unique for the entire network.
NOTE: All NetWare servers require an Internal network number. Only in the following specific circumstances does Windows NT server require Internal
network numbers:
- Windows NT servers using multiple NIC cards require an Internal
network number.
- Windows NT servers using only a single NIC card, but two or more frame types bound to it, require an Internal network number.
- Some programs, such as Btrieve, require Windows NT to define an
Internal network number to function correctly.
Component Definition
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Node An address assigned to a node can be a MAC address,
a logically assigned address (Token Ring), or the number
one (1) if an Internal network number is specified.
For the local IPX destination addresses, the Node address
maps to the hardware address of the network node. This
eliminates the requirement for a separate address resolution
protocol such as ARP for IP.
Socket Some IPX Sockets are designated for a specific process,
some are negotiated for a session.
The following table lists some well known sockets:
Process Socket
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NCP 451
SAP 452
RIP 453
NetBIOS 455
NMPI 551
A Packet Type describes the protocol included in the frame. The following table lists some of the protocols and their hexadecimal and decimal values:
Hex Dec Protocol
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00 00 SAP, NSP, other IPX broadcasts
01 01 RIP
04 04 SAP, NetBIOS sessions and directed datagrams
05 05 SPX
11 17 NCP
14 20 NetBIOS name resolution broadcasts
The IPX frame type describes the method of encapsulating data in an IPX
packet, and is distinguished by the header of network packet. Network
nodes with dissimilar frame types cannot communicate with each other.
The following table lists the fields present in the header for each frame type:
Protocol Ethernet - 802.3 Etype LLC SNAP Token
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802. X X
802.3 X
Ethernet II X 0x8137
Ethernet SNAP X X X
Token X X
Token SNAP X X X
Component Definition
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SPX Sequenced Packet eXchange (SPX) is a Session management
protocol, which provides connection oriented services for
applications that do not require file or print I/O. Original
implementation requires an ACK for every packet sent.
SPX II SPX II includes performance enhancements such as burst mode
support.
NCP NetWare Core Protocol (NCP) provides standard file and print
services to NetWare servers. This is the Novell equivalent of
the Microsoft SMB protocol.
SAP Service Advertising Protocol (SAP) facilitates the creation of
a database of network services. The SAP database is
maintained by periodic SAP broadcasts.
NOTE: Clients can attempt to locate network services either by directly querying the NetWare Bindery, or by broadcasting a SAP request for the requested service.
Component Definition
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RIP Routing Information Protocol (RIP) facilitates the
exchange or routing information on an IPX network.
Routing Services Routing services allow routers to determine the
fastest route using Hop counts and ticks. Every router
on a network broadcasts every 60 seconds. All servers
with an Internal Network Number must perform periodic
RIP broadcasts.
Address Resolution Address resolution allows clients to map a destination
IPX address to a MAC address. This provides the same
functionality for IPX as ARP provides for IP.
NBIPX NetBIOS over IPX (NBIPX) provides connection oriented
session support for NetBIOS applications and the SMB
protocol. NetBIOS support over IPX is provided on most
Microsoft implementations of NWLink.
NOTE: Windows NT requires NetBIOS over IPX for client SMB support through the Workstation service.
Component Definition
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NMPI Name Management Protocol on IPX (NMPI) is Microsoft's
protocol for name management support when you
use IPX without the NetBIOS interface. This process of
routing the SMB protocol directly through IPX is known
as Direct Hosting.
NOTE: Windows 95 and Windows for Workgroups 3.11 use Direct Hosting by default. Windows NT Server 3.5 and later support Direct Hosting using the Server service only.