2.1 Transport

[C706] specifies two protocol variants within connection-oriented RPC and connectionless RPC. This specification maintains, as specified in [C706], categorization for the descriptions of the RPC protocol variants.

These extensions update the protocol identifiers that are specified in [C706] Appendix I. [C706] specifies that the protocol identifier can be one of three types:

  1. An octet string derived from an interface UUID combined with a version number.

  2. An octet string derived from OSI object identifiers (OIDs).

  3. Single octet identifiers that are registered by the Open Software Foundation for commonly used protocols.

The extensions specified in this document mandate that the third type MUST be used for all communications.

Unless explicitly stated otherwise, the protocol identifier (used by each protocol sequence as specified in sections 2.1.1 and 2.1.2) is as specified in the table in [C706] Appendix I.

The RPC protocol sequence strings for the RPC transports defined by these extensions are specified in the following table.<1>

 RPC transport

 RPC protocol sequence string


ncacn_np (see section

TCP/IP (both IPv4 and IPv6)

ncacn_ip_tcp (see section


ncadg_ip_udp (see section


ncacn_spx (see section


ncadg_ipx (see section

NetBIOS over IPX

ncacn_nb_ipx (see section

NetBIOS over TCP

ncacn_nb_tcp (see section

NetBIOS over NetBEUI

ncacn_nb_nb (see section


ncacn_at_dsp (see section


ncacn_http (see section