Description of Microsoft NWLINK IPX/SPX-Compatible Transport

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This article was previously published under Q203051

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SUMMARY

This article describes the basic components in the Microsoft NWLINK IPX/SPX Compatible Transport.

MORE INFORMATION

The following table defines some components included in the NWLINK IPX/SPX Compatible Transport protocol suite.

Component     Definition
---------------------------------------------------------------------------
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. Windows servers require Internal network numbers only in the following specific circumstances:

Windows servers using multiple NIC cards require an Internal network number.
Windows 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 to define an Internal network number to function correctly.

Component   Definition
------------------------------------------------------------------------
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
----------------
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
--------------------------------------------------------
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
-------------------------------------------------------------
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
-------------------------------------------------------------------------
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
--------------------------------------------------------------------------
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 requires NetBIOS over IPX for client SMB support through the Workstation service.

Component            Definition
--------------------------------------------------------------------------
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.