9 Error handling procedures

3GPP44.318Generic Access Network (GAN)Mobile GAN interface layer 3 specificationRelease 17TS

9.1 General

The procedures specified in this specification apply to those messages which pass the checks described in this sub-clause.

This sub-clause also specifies procedures for the handling of unknown, unforeseen, and erroneous protocol data by the receiving entity. These procedures are called "error handling procedures", but in addition to providing recovery mechanisms for error situations they define a compatibility mechanism for future extensions of the protocols.

Sub-clauses 9.2 to 9.4 shall be applied in order of precedence.

In this sub-clause the following terminology is used:

– An IE is defined to be syntactically incorrect in a message if it contains at least one value defined as "reserved" in sub-clause 11, or if its value part violates rules of clause 11. However it is not a syntactical error that an IE specifies in its length indicator a greater length than defined in clause 11.

– A message is defined to have semantically incorrect contents if it contains information which, possibly dependent on the state of the receiver, is in contradiction to the resources of the receiver and/or to the procedural part of this specification.

The procedures below apply to GA-RC/GA-CSR, GA-PSR, and GA-RRC messages, unless explicitly specified otherwise. The MS shall use the GA-CSR STATUS message to indicate problems with the GA-RC and GA-CSR protocols, the GA-PSR STATUS message to indicate problems with the GA-PSR protocol, and the GA-RRC STATUS message to indicate problems with the GA-RRC protocol.

9.2 Message too short

When a message is received that is too short to contain a complete message header and all the mandatory information elements, that message shall be ignored.

9.3 Invalid Message Header

If the MS receives a message over UDP with message type not defined or not implemented, it shall ignore the message.

If the MS receives a message over TCP with protocol discriminator not defined or not implemented, it shall ignore the message.

If the MS receives a message with Skip Indicator IE not encoded as 0000 or Length IE greater than 2048, it shall ignore the message.

If the MS receives a message over TCP with message type not defined for the specific PD (GA-RC/GA-CSR, GA-PSR or GA-RRC) or not implemented, it shall return a GA-CSR STATUS, GA-PSR STATUS or GA-RRC STATUS message, respectively, with cause "message type non-existent or not implemented".

If the MS receives a message not compatible with the protocol state, the MS shall ignore the message and shall return a (GA-CSR, GA-PSR or GA-RRC) STATUS message with cause "Message type not compatible with protocol state".

9.4 Invalid Information Elements

If the MS receives a GA-RC/GA-CSR, GA-PSR or GA-RRC message with a missing or syntactically incorrect mandatory IE, the MS shall ignore the message and shall return a (GA-CSR, GA-PSR or GA-RRC) STATUS message with cause "Invalid mandatory information". In addition, if the message was a GA-CSR RELEASE message or GA-RRC RELEASE message, the actions taken shall be the same as specified in sub-clause 7.5 or sub-clause 8a.5, respectively.

The MS shall ignore all unknown IEs in received messages.

The MS shall treat all optional IEs that are syntactically incorrect in a message as not present in the message.

If the MS diagnoses a missing or unexpected conditional IE or when it receives at least one syntactically incorrect conditional IE, it shall ignore the message and shall return a (GA-CSR, GA-PSR or GA-RRC) STATUS message with cause value "conditional IE error".

If the MS receives a message with semantically incorrect contents, it shall ignore the message and shall return a (GA-CSR, GA-PSR or GA-RRC) STATUS message with cause value "semantically incorrect message".

9.5 Handling of lower layer faults

The handling of lower layer failures in the MS while in the GA-RC-DEREGISTERED state is described in sub-clauses 5.6.2 and 6.2.4.2.

The handling of lower layer failures in the MS while not in the GA-RC-DEREGISTERED state is described below:

For all lower layer failures in the MS (for example related to DNS, IPsec or TCP failures other than RST), the MS shall:

– release the TCP connection towards the current GANC, if established,

– stop timer TU3906,

– release the secure connection towards SEGW of the current GANC, if established, as defined in sub-clause 4.5,

– start timer TU3905, and

– enter GA-RC-DEREGISTERED state.

9.6 Out of sequence IEs

The MS shall ignore all out of sequence IEs in a message. The network should take the same approach.