+---+----------------+----------------+----------------+------------+
| 0 | 0x04 | D_ID |
+---+----------------+----------------+----------------+------------+
| 1 | 0x00 | S_ID |
+---+----------------+----------------+----------------+------------+
| 2 | 0x05 | F_CTL |
+---+----------------+----------------+----------------+------------+
| 3 | SEQ_ID | 0x20 | SEQ_CNT |
+---+----------------+----------------+----------------+------------+
| 4 | OX_ID | RX_ID |
+---+----------------+----------------+----------------+------------+
| 5 | 0xXX-XX-XX-XX Parameter Relative Offset |
+---+------+--------------------------------------------------------+
| 6 | 0001 | 0x000 | Dest. MAC (Hi order bits) |
+---+------+---------+----------------+----------------+------------+
| 7 | Dest. MAC (Lo order bits) |
+---+------+----------+----------------+----------------------------+
| 8 | 0001 | 0x000 | Src. MAC (Hi order bits) |
+---+------+---------+----------------+----------------+------------+
| 9 | Src. MAC (Lo order bits) |
+---+----------------+----------------+----------------+------------+
|10 | 0xAA | 0xAA | 0x03 | 0x00 |
+---+----------------+----------------+----------------+------------+
|11 | 0x00-00 | 0x08-06 |
+---+----------------+----------------+----------------+------------+
|12 | ARP Packet Data |
+---+----------------+----------------+----------------+------------+
|13| ... |
+---+----------------+----------------+----------------+------------+
The Code Points for a FARP-REQ for a specific Match Address Code
Point MATCH_WW_PN_NN ( b'011') is shown below. In particular, note
the IP addresses field of the Requester set to a valid address and
that of the responder set to '0'. Note also the setting of the D_ID
address and the Port_ID of the Responder.
The corresponding code point for a FARP-REPLY is also shown below.
In particular, note the setting of the Port_ID of Responder and the
IP address setting of the Responder.
E.4.2 Code Points with FARP Command
Code Points for FC Frame with FARP-REQ Command for MATCH_WW_PN_NN
+---+----------------+----------------+----------------+------------+
|Wrd| <31:24> | <23:16> | <15:08> | <07:00> |
+---+----------------+----------------+----------------+------------+
| 0 | 0x04 | D_ID = |
| | | 0xFF 0xFF 0xFF |
+---+----------------+----------------+----------------+------------+
| 1 | 0x00 | S_ID |
+---+----------------+----------------+----------------+------------+
| 2 | 0x05 | F_CTL |
+---+----------------+----------------+----------------+------------+
| 3 | SEQ_ID | 0x20 | SEQ_CNT |
+---+----------------+----------------+----------------+------------+
| 4 | OX_ID | RX_ID |
+---+----------------+----------------+----------------+------------+
| 5 | 0xXX-XX-XX-XX Parameter Relative Offset |
+---+----------------+----------------+----------------+------------+
| 6 | 0x54 | 0x00 | 0x00 | 0x00 |
+---+----------------+----------------+----------------+------------+
| 7 | Port_ID of Requester = S_ID |Match Addr. |
| | |Code Points |
| | | xxxxx011 |
+---+----------------+----------------+----------------+------------+
| 8 | Port_ID of Responder = |Responder |
| | 0x00 0x00 0x00 |Flags |
+---+----------------+----------------+----------------+------------+
| 9 | 0001 | 0x000 |WW_PN Src. MAC(Hi order bits)|
+---+------+---------+----------------+----------------+------------+
|10 | WW_PN Src. MAC (Lo order bits) |
+---+------+----------+---------------+-----------------------------+
|11 | 0001 | 0x000 |WW_NN Src. MAC(Hi order bits)|
+---+------+---------+----------------+----------------+------------+
|12 | WW_NN Src. MAC (Lo order bits) |
+---+----------------+----------------+----------------+------------+
|13 | 0001 | 0x000 |WW_PN Src. MAC(Hi order bits)|
+---+------+---------+----------------+----------------+------------+
|14 | WW_PN Dest. MAC (Lo order bits) |
+---+------+----------+---------------+-----------------------------+
|15 | 0001 | 0x000 |WW_NN Dest.MAC(Hi order bits)|
+---+------+---------+----------------+----------------+------------+
|16 | WW_NN Dest. MAC (Lo order bits) |
+---+----------------+----------------+----------------+------------+
|17 | 0x00-00-00-00 |
+--------------------+----------------+---------+-------------------+
|18 | 0x00-00-00-00 |
+--------------------+----------------+---------+-------------------+
|19 | 0x00-00-00-00 |
+--------------------+----------------+---------+-------------------+
|20 | set to a valid IPv4 Address by Requester if Available |
+--------------------+----------------+---------+-------------------+
|21 | 0x00-00-00-00 |
+--------------------+----------------+---------+-------------------+
|22 | 0x00-00-00-00 |
+--------------------+----------------+---------+-------------------+
|23 | 0x00-00-00-00 |
+--------------------+----------------+---------+-------------------+
| | 0x00-00-00-00 |
|24 | set to a valid IPv4 Address of Responder if available |
+--------------------+----------------+---------+-------------------+
Code Points for FC Frame with FARP-REPLY Command
+---+----------------+----------------+----------------+------------+
|Wrd| <31:24> | <23:16> | <15:08> | <07:00> |
+---+----------------+----------------+----------------+------------+
| 0 | 0x04 | D_ID |
+---+----------------+----------------+----------------+------------+
| 1 | 0x00 | S_ID |
+---+----------------+----------------+----------------+------------+
| 2 | 0x05 | F_CTL |
+---+----------------+----------------+----------------+------------+
| 3 | SEQ_ID | 0x20 | SEQ_CNT |
+---+----------------+----------------+----------------+------------+
| 4 | OX_ID | RX_ID |
+---+----------------+----------------+----------------+------------+
| 5 | 0xXX-XX-XX-XX Parameter Relative Offset |
+---+----------------+----------------+----------------+------------+
| 6 | 0x55 | 0x00 | 0x00 | 0x00 |
+---+----------------+----------------+----------------+------------+
| 7 | Port_ID of Requester = D_ID | xxxxx011 |
+---+----------------+----------------+----------------+------------+
| 8 | Port_ID of Responder = S_ID |Resp. Flag |
+---+----------------+----------------+----------------+------------+
| 9 | 0001 | 0x000 |WW_PN Src. MAC(Hi order bits)|
+---+------+---------+----------------+----------------+------------+
|10 | WW_PN Src. MAC (Lo order bits) |
+---+------+----------+---------------+-----------------------------+
|11 | 0001 | 0x000 |WW_NN Src. MAC(Hi order bits)|
+---+------+---------+----------------+----------------+------------+
|12 | WW_NN Src. MAC (Lo order bits) |
+---+----------------+----------------+----------------+------------+
|13 | 0001 | 0x000 |WW_PN Src. MAC(Hi order bits)|
+---+------+---------+----------------+----------------+------------+
|14 | WW_PN Dest. MAC (Lo order bits) |
+---+------+----------+---------------+-----------------------------+
|15 | 0001 | 0x000 |WW_NN Dest.MAC(Hi order bits)|
+---+------+---------+----------------+----------------+------------+
|16 | WW_NN Dest. MAC (Lo order bits) |
+---+----------------+----------------+----------------+------------+
|17 | 0x00-00-00-00 |
+--------------------+----------------+---------+-------------------+
|18 | 0x00-00-00-00 |
+--------------------+----------------+---------+-------------------+
|19 | 0x00-00-00-00 |
+--------------------+----------------+---------+-------------------+
|20 | set to a valid IPv4 Address by Requester |
+--------------------+----------------+---------+-------------------+
|21 | 0x00-00-00-00 |
+--------------------+----------------+---------+-------------------+
|22 | 0x00-00-00-00 |
+--------------------+----------------+---------+-------------------+
|23 | 0x00-00-00-00 |
+--------------------+----------------+---------+-------------------+
|24 | set to a valid IPv4 Address by Responder |
+--------------------+----------------+---------+-------------------+
APPENDIX F: Fibre Channel Protocol Considerations
F.1 Reliability In Class 3
Problem: Sequence ID reuse in Class 3 can conceivably result in
missing frame aliasing, which could result in delivery of corrupted
(incorrectly-assembled) data, with no corresponding detection at the
FC level.
Prevention: This specification requires one of the following methods
if Class 3 is used.
- Continuously increasing Sequence Count (new Login Bit) - both
sides must set When an N_Port sets the PLOGI login bit for
continuously increasing SEQ_CNT, it is guaranteeing that it
will transmit all frames within an Exchange using a
continuously increasing SEQ_CNT (see description in Section
B.1 below).
- After using all SEQ_IDs (0-255) once, must start a new
Exchange. It is recommended that a minimum of 4 Exchanges be
used before an OX_ID can be reused.
- Note: If an implementation is not checking the OX_ID when
reassembling Sequences, the problem can still occur. Cycling
through some number of SEQ_IDs, then jumping to a new Exchange
does not solve the problem. SEQ_IDs must still be unique
between two N_Ports, even across Exchanges.
- Use only single-frame Sequences.
F.2 Continuously Increasing SEQ_CNT
This method allows the recipient to check incoming frames, knowing
exactly what SEQ_CNT value to expect next. Since the SEQ_CNT will not
repeat for 65,536 frames, the aliasing problem is significantly
reduced.
A Login bit (PLOGI) is used to indicate that a device always uses a
continuously increasing SEQ_CNT, even across transfers of Sequence
Initiative. This bit is necessary for interoperability with some
devices, and it provides other benefits as well.
In the FC-PH-3 [11], the following is supported:
Word 1, bit 17 - SEQ_CNT (S)
0 = Normal FC-PH rules apply
1 = Continuously increasing SEQ_CNT
Any N_Port that sets Word 1, Bit 17 = 1, is guaranteeing that it will
transmit all frames within an Exchange using a continuously
increasing SEQ_CNT. Each Exchange SHALL start with SEQ_CNT = 0 in the
first frame, and every frame transmitted after that SHALL increment
the previous SEQ_CNT by one, even across transfers of Sequence
Initiative. Any frames received from the other N_Port in the Exchange
shall have no effect on the transmitted SEQ_CNT.
Appendix G: Acronyms and Glossary of FC Terms
It is assumed that the reader is familiar with the terms and acronyms
used in the FC protocol specification [2]. The following is provided
for easy reference.
First Frame: The frame that contains the SOFi field. This means a
logical first and may not necessarily be the first frame temporally
received in a sequence.
Code Point: The coded bit pattern associated with control fields in
frames or packets.
PDU: Protocol Data Unit
ABTS_LS: Abort Sequence Protocol - Last Sequence. A protocol for
aborting an exchange based on the ABTS recipient setting the
Last_Sequence bit in the BA_ACC ELS to the ABTS
ADISC: Discover Address. An ELS for discovering the Hard Addresses
(the 24 bit NL_Port Identifier) of N_Ports
D_ID: Destination ID
ES: End sequence. This FCTL bit in the FC header indicates this frame
is the last frame of the sequence.
FAN: Fabric Address Notification. An ELS sent by the fabric to all
known previously Logged in ports following an initialization event.
FLOGI: Fabric Login.
LIP: Loop Initialization. A primitive Sequence used by a port to
detect if it is part of a loop or to recover from certain loop
errors.
Link: Two unidirectional paths flowing in opposite directions and
connecting two Ports within adjacent Nodes.
LOGO: Logout.
LR: Link reset. A primitive sequence transmitted by a port to
initiate the link reset protocol or to recover from a link timeout.
LS: Last Sequence of Exchange. This FCTL bit in the FC header
indicates the Sequence is the Last Sequence of the Exchange.
Network Address Authority: A 4-bit field specified in Network_Headers
that distinguishes between various name registration authorities that
may be used to identify the WW_PN and the WW_NN. NAA=b'0001'
indicates IEEE-48-bit MAC addresses
Node: A collection of one or more Ports identified by a unique World
Wide Node Name (WW_NN).
NOS: Not Operational. A primitive Sequence transmitted to indicate
that the port transmitting this Sequence has detected a link failure
or is offline, waiting for OLS to be received.
OLS: Off line. A primitive Sequence transmitted to indicate that the
port transmitting this Sequence is either initiating the link
initialization protocol, receiving and recognizing NOS, or entering
the offline state.
PDISC: Discover Port. An ELS for exchanging Service Parameters
without affecting Login state.
Primitive Sequence: A primitive Sequence is an Ordered Set that is
transmitted repeatedly and continuously.
Private Loop Device: A device that does not attempt Fabric Login
(FLOGI) and usually adheres to PLDA. The Area and Domain components
of the NL_Port ID must be 0x0000. These devices cannot communicate
with any port not in the local loop.
Public Loop Device: A device whose Area and Domain components of the
NL_Port ID cannot be 0x0000. Additionally, to be FLA compliant, the
device must attempt to open AL_PA 0x00 and attempt FLOGI. These
devices communicate with devices on the local loop as well as devices
on the other side of a Fabric.
Port: The transmitter, receiver and associated logic at either end of
a link within a Node. There may be multiple Ports per Node. Each Port
is identified by a unique Port_ID, which is volatile, and a unique
World Wide Port Name (WW_PN), which is unchangeable. In this
document, the term "port" may be used interchangeably with NL_Port or
N_Port.
Port_ID: Fibre Channel ports are addressed by unique 24-bit Port_IDs.
In a Fibre Channel frame header, the Port_ID is referred to as S_ID
(Source ID) to identify the port originating a frame, and D_ID to
identify the destination port. The Port_ID of a given port is
volatile (changeable).
PLOGI: Port Login.
SI: Sequence Initiative
World Wide Port_Name (WW_PN): Fibre Channel requires each Port to
have an unchangeable WW_PN. Fibre Channel specifies a Network Address
Authority (NAA) to distinguish between the various name registration
authorities that may be used to identify the WW_PN. A 4-bit NAA
identifier, 12-bit field set to 0x0 and an IEEE 48-bit MAC address
together make this a 64-bit field.
World Wide Node_Name (WW_NN): Fibre Channel identifies each Node with
a unchangeable WW_NN. In a single port Node, the WW_NN and the WW_PN
may be identical.
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