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Novell IPX: Internetwork Packet Exchange protocol

Internetwork Packet Exchange (IPX) is a legacy network protocol used by the Novell NetWare operating systems to route packets through an internetwork. IPX is a datagram protocol used for connectionless communications - similar to IP (Internet Protocol) in the TCP/IP suite. Higher-level protocols, such as SPX and NCP, are used for additional error recovery services.

To make best-path routing decisions, IPX uses the services of a dynamic distance vector routing protocol such as Routing Information Protocol [RIP ]) or NetWare Link-State Protocol [NLSP]).

Novell IPX network addresses are unique and are represented in hexadecimal format that consist of two parts: a network number and a node number. The IPX network number, which is assigned by the network administrator, is 32 bits long. The node number, which usually is the Media Access Control (MAC) address for one of the system's network interface cards (NICs), is 48 bits long. IPX's use of a MAC address for the node number enables the system to send nodes to predict what MAC address to use on a data link.

Novell NetWare IPX supports four encapsulation schemes on a single router interface:

  • Novell Proprietary- Also called 802.3 raw or Novell Ethernet_802.3, Novell proprietary serves as the initial encapsulation scheme that Novell uses.
  • 802.3- Also called Novell_802.2, 802.3 is the standard IEEE 802.3 frame format.

  • Ethernet version 2- Also called Ethernet-II or ARPA, Ethernet version 2 includes the standard Ethernet Version 2 header, which consists of Destination and Source Address fields followed by an EtherType field.
  • SNAP- Also called Ethernet_SNAP, SNAP extends the IEEE 802.2 header by providing a type code similar to that defined in the Ethernet version 2 specification.
The maximum length of the data section of an IPX packet varies from a minimum of 30 bytes (the header only) depending on the lower layer MAC protocol (Ethernet or token ring) that is being used.


Protocol Structure - Novell IPX: Internetwork Packet Exchange Packet Header

The NetWare IPX Packet Header:

8

16bit

Checksum

Packet Length

Transport control

Packet Type

Destination Network (4 bytes)

Destination node (6 bytes)

Destination socket (2 bytes)

Source network (4 bytes)

Source node (6 bytes)

Source socket (2 bytes)

  • Checksum- Indicates that the checksum is not used when this 16-bit field is set to 1s (FFFF).
  • Packet length- Specifies the length, in bytes, of a complete IPX datagram. IPX packets can be any length, up to the media maximum transmission unit (MTU) size (no packet fragmentation allowed).
  • Transport control- Indicates the number of routers through which the packet has passed. When this value reaches 16, the packet is discarded under the assumption that a routing loop might be occurring.
  • Packet type- Specifies which upper-layer protocol should receive the packet's information. It has two common values:
    • 5- Specifies Sequenced Packet Exchange (SPX)
    • 17- Specifies NetWare Core Protocol (NCP)
  • Destination network, Destination node, and Destination socket- Specify destination information.
  • Source network, Source node, and Source socket- Specify source information.


Related Protocols
IP , IPv6 , NetWare , SPX , RIP , NLSP

Sponsor Source

IPX is a Novell protocol.



Reference

http://www.novell.com/:  IPX Structure  
http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/netwarep.htm : NetWare Protocols