Editing Short Message Peer-to-Peer (section)

== Extensibility, compatibility and interoperability ==

Since introduction of TLV parameters in version 3.4, the SMPP may be regarded an [[Extensibility|extensible]] protocol. In order to achieve the highest possible degree of compatibility and [[interoperability]] any implementation should apply the Internet [[robustness principle]]: ″Be conservative in what you send, be liberal in what you accept″. It should use a minimal set of features which are necessary to accomplish a task. And if the goal is communication and not quibbling, each implementation should overcome minor nonconformities with standard:

* Respond with a <code>generic_nack</code> with <code>command_status=3</code> to any unrecognised SMPP command, but do not stop the communication.
* Ignore any unrecognised, unexpected or unsupported TLV parameters.
* The borders of PDUs are always given by the PDUs' <code>command_length</code> field. Any message field must not exceed the end of PDU. If a field is not properly finished, it should be treated as truncated at the end of PDU, and it should not affect further PDUs.

Information applicable to one version of SMPP can often be found in another version of SMPP, for example with the case of SMPP 3.4 describing the only mechanism of delivery receipts in SMPP 3.3 described above.