NOTIFICATION Message Format A NOTIFICATION message is sent when an error condition is detected The BGP connection is closed immediately after sending it In addition to the fixed-size BGP header, the NOTIFICATION message contains the following fields:.. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 - - - - - - - - - - - - - - - - - - - - - - - - - - - - | Error code | Error subcode | Data | - - - - - - - - - - - - - - - - | | - - - - - - - - - - - - -
Error Code: This 1-octet unsigned integer indicates the type of NOTIFICATION The following Error Codes have been defined:. Error Code Symbolic Name 1 Message Header Error 2 OPEN Message Error 3 UPDATE Message Error 4 Hold Timer Expired 5 Finite State Machine Error 6 Cease error subcode: This 1-octet unsigned integer provides more specific information about the nature of the reported error Each error Code may have one or more error subcodes associated with it If no appropriate error Subcode is defined, then a zero (unspecific) value.. is used for the Error Subcode field Message Header Error subcodes:. 1 - Connection Not Synchronized 2 - Bad Message Length 3 - Bad Message Type OPEN Message Error subcodes:... 1 - Unsupported Version Number 2 - Bad Peer AS 3 -.. Bad BGP Identifier. 4 - UNSUPPORTED OPTIONAL Parameter. 5 - Authentication Failure. 6 - Unacceptable Hold Time. Update Message Error SU bcodes:...... 1 - Malformed Attribute List 2 - Unrecognized Well-known Attribute 3 - Missing Well-known Attribute 4 - Attribute Flags Error 5 - Attribute Length Error 6 - Invalid ORIGIN Attribute 7 - AS Routing Loop 8 - Invalid .. NEXT_HOP Attribute 9 - Optional Attribute Error 10 - Invalid Network Field 11 - Malformed AS_PATH Data:.. This variable-length field is used to diagnose the reason for the NOTIFICATION The contents of the Data field depend upon the Error Code and Error. Subcode. See Section 6 Below for more details. Note That the length of the data field can be determined from the message length length = 21
