2.1.1.5 NetBIOS over TCP (NCACN_NB_TCP)
This protocol sequence specifies RPC directly over NetBIOS over TCP. There are no intermediate protocols between RPC and NetBIOS over TCP. 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 TCP, which MAY<10><11><12> be supported.
When these extensions are enabled over the NetBIOS over TCP session service, the network address MUST be a NetBIOS machine name, as specified in [RFC1001] and [RFC1002].
The endpoint MUST be an 8-bit unsigned integer port 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 TCP MUST use an endpoint mapper well-known endpoint of 135.
RPC over NetBIOS over TCP 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 TCP, 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.