[{"name":"R5-202138","title":"Discussion paper on the need for testing UE handling of extended and spare fields in SI","source":"NTT DOCOMO INC.","contact":"Alan Aquino","contact-id":75436,"tdoctype":"discussion","for":"Discussion","abstract":"Extended\/spare fields in SI may be improperly handled by the UE, resulting in the UE being unable to Attach and the NW being unable to assist.\n\nDuring our rollout of commercial 5G, we discovered an issue in the field involving a Rel-9 UE being unable to properly decode a Rel-15 extended value being broadcast over System Information in our network. Normally, when UE receives an ASN.1 message on any logical channel and considers an optional value as not comprehended (e.g. when the value is set to one that is not defined in the version of the transfer syntax supported by the UE), the UE shall treat the message as if the field were absent and in accordance with the need code for absence of the concerned field. However, the observed behaviour was that the UE treated this as an ASN.1 violation or encoding error, ignoring the System Information message and as a result being unable to perform an attach to our network. \nSince the System Information is broadcast to all UEs and cannot be changed to account for decoding issues in a small number of UEs, and since the NW is unable to handle any issue when the UE is still in Idle, if this is not properly tested, the impact of this issue will be quite severe.\nAs far as we have checked, this error handling is not currently covered by any RAN5 test case, and so we propose that a test case be added as described in [1] to cover this issue in order to ensure that older UE are able to properly ignore newer extensions and spare fields that are added to System Information.\n\nThe issue that we have discussed concerns only improper handling of extended and spare fields, but if other companies have come across similar issues in other messages, then we are open to discussing those as well.\nProposal 1: RAN5 to add testing for this previously uncovered case for extended fields and spare fields.\nProposal 2: RAN5 to use index value 31 of SIB-Type for extended field testing from Rel-8 to Rel-16. \nProposal 3: RAN5 to use index value 15 of SIB-Type from Rel-8 to Rel-11, and index value 7 of si-WindowLength-BR from Rel-13 to Rel-16 for spare field testing.\nProposal 4: A CR for the extended field and spare field test can be found below in [1], and if this CR is agreed we will reflect the same change to the other existing NAS attach test cases.","secretary_remarks":"","agenda_item_sort_order":466,"ainumber":"6.4.6","ainame":"\tDiscussion Papers \/ Work Plan \/ TC lists","tdoc_agenda_sort_order":21380,"status":"noted","reservation_date":"2020-05-08 01:44:51","uploaded":"2020-05-08 06:45:35","revisionof":"","revisedto":"","release":"Rel-16","crspec":"","crspecversion":"","workitem":[{"winame":"TEI8_Test"}],"crnumber":"","crrevision":"","crcategory":"","tsg_crp":"","lsreplyto":"","lsto":"","Cc":"","lsoriginalls":"","lsreply":"","link":"http:\/\/www.3gpp.org\/ftp\/TSG_RAN\/WG5_Test_ex-T1\/TSGR5_87_Electronic\/Docs\/R5-202138.zip","group":"R5","meeting":"R5-ah-38102","year":2020,"uicc_affected":null,"me_affected":null,"ran_affected":null,"cn_affected":null,"clauses_affected":null,"crsinpack":null,"crsinpacknumber":0}]