2.1.1.4 NetBIOS over IPX (NCACN_NB_IPX)
This protocol sequence specifies RPC directly over NetBIOS over IPX, which MAY<7><8> be supported. There are no intermediate protocols between RPC and NetBIOS over IPX. These extensions define three NetBIOS mappings for RPC. The mappings are the same at the RPC level but use a different NetBIOS transport. Some implementations can offer higher-layer protocols the opportunity to choose the NetBIOS transport to be used. This section covers the mapping of RPC to NetBIOS over IPX.<9>
When these extensions are enabled over the NetBIOS over IPX session service, as specified in [MS-CIFS] section 2.1.1.3, the network address MUST be a NetBIOS host name.
The endpoint MUST be an 8-bit unsigned integer socket number. The network address and endpoint are not transmitted on the network by these extensions but are used by lower-layer protocols to set up the connection.
RPC over NetBIOS over IPX MUST use an endpoint mapper well-known endpoint of 135. RPC over NetBIOS over IPX MUST use a protocol identifier of 0x12 instead of the value of 0x11, as specified in [C706] Appendix I.
When communicating between a client and a server by using NetBIOS over IPX, each RPC PDU MUST be prefixed with a 4-octet sequence number encoded with little-endian byte ordering, as defined in the following diagram.
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The sequence numbers SHOULD start at 0 and increase monotonically, wrapping if it exceeds 232-1, for each sent PDU on a given NetBIOS connection. The server SHOULD ignore the sequence number values.