IPX, Internet Packet Exchange

Protocol suite:	Novell NetWare.
Protocol type:	Connectionless network layer protocol.

RFC 1634, pages 2 and 3:

The IPX WAN protocol operation begins immediately after link establishment. While IPX is a connectionless datagram protocol, WANs are often connection-oriented. Different WANs have different methods of link establishment.

Operation Over PPP. IPX uses PPP when operating over point-to-point synchronous and asynchronous networks.

Operation over X.25 Switched Virtual Circuits. With X.25, link establishment means successfully opening an X.25 virtual circuit. As specified in RFC 1356, "Multiprotocol Interconnect on X.25 and ISDN in the Packet Mode", the protocol identifier 0x800000008137 is used in the X.25 Call User Data field of the Call Request frame, and indicates that the virtual circuit will be devoted to IPX.

Operation over X.25 Permanent Virtual Circuits. The nature of X.25 PVC's is that no call request is made. When the router is informed that X.25 Layer 2 is up, the router should assume that link establishment is complete. Each IPX packet is encapsulated in an X.25 data frame sequence without additional framing. Novell IPX assumes a particular X.25 permanent circuit is devoted to the use of IPX.

Operation over Frame Relay Permanent Virtual Circuits. Each IPX packet is encapsulated in a Frame Relay frame sequence as defined in [RFC 1490] without additional framing. When a router detects that a Frame Relay PVC has transitioned from an inactive to an active state, link establishment is considered complete and IPXWAN exchange over this newly activated link begins. When an active PVC becomes inactive, the router reflects the lost connectivity in its routing information database.

MAC header

IPX header

Data :::

IPX header:

00	08	16
Checksum		Packet length
Transport control	Type	Destination network
Destination network		Destination node
Destination node
Destination socket		Source network
Source network		Source node
Source node
Source socket		Data :::

Checksum. 16 bits.
Always set to 0xFFFF.

Packet Length. 16 bits.
The total length of the packet header and the data.

Transport control. 8 bits.
The hop count.

Type. 8 bits.
Specifies the encapsulated protocol.

Type	Description
0x00	Unknown.
0x01	RIP, Routing Information Packet.
0x02	Echo Packet.
0x03	Error Packet.
0x04	PEP, Packet Exchange Protocol.
0x05	SPX, Sequenced Packet Protocol.
0x10 - 0x1F	Experimental Protocols.
0x11	NCP, NetWare Core Protocol.
0x12 - 0xFF

Destination network. 32 bits.
A subnet identifier of the receiver.

Destination node. 48 bits.
The physical address of the receiver.

Destination socket. 16 bits.
The socket number of the receiver.

Source network. 32 bits.
Subnet identifier of the sender.

Source node. 48 bits.
The physical address of the sender.

Source socket. 16 bits.
The socket number of the sender.

Data. Variable length.

Socket	Description
0x01	RIP, Routing Information Packet.
0x02	Echo Protocol Packet.
0x03	Error Handling Packet.
0x20 - 0x3F	Experimental.
0x1 - 0xBB8	Xerox registered.
0xBB9	Dynamically Assigned.
0x451	NCP, NetWare Core Protocol.
0x452	SAP, Service Advertising Protocol.
0x453	RIP, Routing Information Protocol.
0x455	NetBios.
0x456	Diagnostic.
0x457	Serialization.
0x8060	IPX.
0x9091	TCP over IPXF.
0x9092	UDP over IPXF.
0x9093	IPXF, IPX Fragmentation Protocol.