Fujitsu MBC2073RC, MBC2036RC, MBA3300RC, MBA3147RC Connection responses, Arbitration fairness

1.5 Address frames

1.5.5.3Connection responses

Table 1.25 lists the responses to an OPEN address frame being transmitted.

	Table 1.25 Connection responses
Response	Description
AIP	Arbitration in progress. When an expander device is trying
	to open a connection to the selected destination port, it
	returns an AIP to the source phy. The source phy shall
	reinitialize and restart its Open Timeout timer when it
	receives an AIP. AIP is sent by an expander device while it
	is internally arbitrating for access to an expander port.
OPEN_ACCEPT	Connection request accepted. This is sent by the destination
	phy.
OPEN_REJECT	Connection request rejected. This is sent in response by the
	destination phy or by an expander device.
OPEN address	If the AIP primitive has been detected just before the OPEN
frame	address frame, this indicates a top-priority connection
	request, meaning that the OPEN_ACCEPT primitive or an
	OPEN_REJECT primitive must be sent. If an AIP primitive
	has not been detected yet, this indicates that two connection
	requests have crossed over the physical link. At this time,
	arbitration fairness is used to determine which request
	should take priority.
BREAK	The destination port or expander port may reply with
	BREAK indicating the connection is not being established.
Open Timeout	The source phy shall abort the connection request by
timer expires	transmitting BREAK.

After an OPEN_REJECT (CONNECTION RATE NOT SUPPORTED) has been received by a SAS TARG port, the SAS TARG device shall set the connection rate for future requests for that I_T_L_Q nexus to:

a)the last value received in a connection request from the SAS INIT port;

b)1,5 Gbps; or

c)the connection rate in effect when the command was received.

1.5.5.4Arbitration fairness

SAS supports least-recently used arbitration fairness.

(This is a service equalization method that lowers the priority of the most recently used device, that is to say, gives higher priority to devices that have been in the wait state for a long period of time.)

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