6. Compatibility Considerations

All BGP speakers participating as members of a confederation MUST recognize the AS_CONFED_SET and AS_CONFED_SEQUENCE segment type extensions to the AS_PATH attribute.

Any BGP speaker not supporting these extensions will generate a NOTIFICATION message specifying an "UPDATE Message Error" and a sub-code of "Malformed AS_PATH".

This compatibility issue implies that all BGP speakers participating in a confederation MUST support BGP confederations. However, BGP speakers outside the confederation need not support these extensions.