– Usually a single frame Sequence or a frame inserted in the existing sequence
– Used to abort a sequence
• Extended Link Services:
– Used to request specific actions of the destination port – A separate Exchange with one or more frames per sequence – Usually have a reply or reject sequence – May be sent without a prior port login to fabric (e.g. FLOGI)
Basic Link Services (LS):
• Defined by the Fibre Channel ANSI standard • Each BLS is a frame. • ULPs are unaware of BLS frames.
Extended Link Services (ELS):
• Defined regularly by the ANSI committee to provide additional control functions within Fibre Channel
• The number and functionality of Extended Link Services are constantly evolving.