IPX/SPX Configuration and Management Manual

Introduction to NonStop™ IPX/SPX

IPX/SPX Configuration and Management Manual—425731-001

2-9

Frame Types

NonStop™ IPX/SPX supports the four frame types used on Ethernet and token-ring

LANs, as shown in Table 2-1.

Internetwork Packet Exchange (IPX) Protocol

IPX is a connectionless, datagram-oriented, internetworking protocol. IPX sends

outgoing data packets onto the network and directs incoming data to the proper area

within the workstation’s operating system or the network operating system (NOS).

Higher-level protocols (SPX, NCP, and SAP) use IPX to transport messages to their

destinations. IPX does not use a checksum and therefore cannot guarantee end-to-end

data integrity. Higher-level protocols must ensure the reliable transmission of the data.

IPX uses the RIP routing tables to find the fastest route on which to send packets. IPX

uses the services of a LAN driver to deliver messages from one network interface card

(NIC) to another.

Appendix A, Protocol Interfaces and Services for NonStop™ IPX/SPX

, describes the

format of IPX packets.

Sequenced Packet Exchange (SPX) Protocol

SPX provides a connection-oriented service that is reliable in the sense of proper packet

sequencing and retransmissions. SPX tracks data transmissions by sending

acknowledgment requests to the destination of the transmissions. If there is no response

within a specified time, SPX retransmits the data. If a positive acknowledgment is not

received after a period of time, SPX assumes a failure in the connection and drops the

connection. Like IPX, SPX does not use a checksum. Therefore, SPX cannot guarantee

end-to-end data integrity.

Appendix A, Protocol Interfaces and Services for NonStop™ IPX/SPX

, describes the

format of SPX packets.

NetWare Core Protocol (NCP)

NCP is used by clients to communicate with a NetWare file server. NCP can be seen as

both an interface and a protocol. NCP provides access to NetWare network services,

such as printing, connection services, queue management, and file services. For

example, NetWare print servers use NCP to log onto the file server and access print

queues. NCP is a half-duplex, request/response protocol that uses IPX as the underlying

network-level protocol. An NCP packet occupies the data portion of an IPX packet.

Table 2-1. Frame Types and Filter Protocols for Ethernet and Token-Ring LANs

Frame Type Filter Protocol LAN Type

Ethernet II (IEEE 802.3) ipxeth Ethernet only

Logical Link Control (IEEE 802.2) ipx8022 Ethernet or token-ring

IPX 802.3 (Raw 802.3) ipx8023 Ethernet only

Subnetwork Access Protocol (SNAP) ipxsnap Ethernet or token-ring