This counts instances where the length field of the SIP3 header extension, the portion of the header carrying optional or carrier-specific information, was invalid, a check on the optional-extension portion of the header rather than the core fields checked elsewhere. An admin treats this as evidence that whatever device or network element is inserting header extensions on this path is doing so incorrectly. For example, an increment here appearing right after a carrier begins inserting a new type of header extension for billing or routing purposes could indicate that new extension format is not being generated correctly.