Responder by using the ABTS_LS protocol. The use of ABTS_LS for
terminating aged Exchanges or error recovery is outside the scope of
this document.
The termination of IP Exchanges by Logout is discouraged, since this
may terminate active Exchanges on other FC-4s.
7. Summary of Supported Features
Note: 'Settable' means support is as specified in the relevant
standard; all other key words are as defined earlier in this
document.
7.1 FC-4 Header
+--------------------------------------------------------------------+
| Feature | Support | Notes |
+--------------------------------------------------------------------+
| Type Code ( = 5) ISO8802-2 LLC/SNAP | REQUIRED | 2 |
| Network_Headers | REQUIRED | 3 |
| Other Optional Headers | MUST NOT | |
+--------------------------------------------------------------------+
Notes:
1. This table applies only to FC-4 related data, such as IP and
ARP packets. This table does not apply to link services and
other non-FC-4 sequences (PLOGI, for example) that must occur
for normal operation.
2. The TYPE field in the FC Header (Word 2 bits 31-24) MUST
indicate ISO 8802-2 LLC/SNAP Encapsulation (Type 5). This
revision of the document focuses solely on the issues related
to running IP and ARP over FC. All other issues are outside
the scope of this document, including full support for IEEE
802.2 LLC.
3. DF_CTL field (Word 3, bits 23-16 of FC-Header) MUST indicate
the presence of a Network_Header (0010 0000) on the First
logical Frame of FC-4 Sequences. It should not indicate the
presence of a Network_Header on any subsequent frames of the
Sequence.
7.2 R_CTL
R_CTL in FC-Header: Word 0, bits 31-24
+--------------------------------------------------------------------+
| Feature | Support | Notes |
+--------------------------------------------------------------------+
| Information Category (R_CTL Routing): | | |
| | | |
| FC-4 Device Data | REQUIRED | 1 |
| Extended Link Data | REQUIRED | |
| FC-4 Link Data | MUST NOT | |
| Video Data | MUST NOT | |
| Basic Link Data | REQUIRED | |
| Link Control | REQUIRED | |
| | | |
| R_CTL information : | | |
| | | |
| Uncategorized | MUST NOT | |
| Solicited Data | MUST NOT | |
| Unsolicited Control | REQUIRED | |
| Solicited Control | REQUIRED | |
| Unsolicited Data | REQUIRED | 1 |
| Data Descriptor | MUST NOT | |
| Unsolicited Command | MUST NOT | |
| Command Status | MUST NOT | |
+--------------------------------------------------------------------+
Notes:
1. This is REQUIRED for FC-4 (IP and ARP) packets
- Routing bits of R_CTL field MUST indicate Device Data
frames (0000)
- Information Category of R_CTL field MUST indicate
Unsolicited Data (0100)
7.3 F_CTL
F_CTL in FC-Header: Word 2, bits 23-0
+--------------------------------------------------------------------+
| Feature | Support | Notes |
+--------------------------------------------------------------------+
| Exchange Context | Settable | |
| Sequence Context | Settable | |
| First / Last / End Sequence (FS/LS/ES) | Settable | |
| Chained Sequence | MUST NOT | |
| Sequence Initiative (SI) | Settable | 1 |
| X_ID Reassigned / Invalidate | MUST NOT | |
| Unidirectional Transmit | Settable | |
| Continue Sequence Condition | REQUIRED | 2 |
| Abort Seq. Condition -continue and single Seq.| REQUIRED | 3 |
| Relative Offset - Unsolicited Data | Settable | 4 |
| Fill Bytes | Settable | |
+--------------------------------------------------------------------+
Notes
1. For FC-4 frames, each N_Port shall have a dedicated OX_ID for
sending data to each N_Port in the network and a dedicated
RX_ID for receiving data from each N_Port as well. Exchanges
are used in a unidirectional mode, thus setting Sequence
Initiative is not valid for FC-4 frames. Sequence Initiative is
valid when using Extended Link Services.
2. This field is required to be 00, no information.
3. Sequence error policy is requested by an exchange originator in
the F_CTL Abort Sequence Condition bits in the first data frame
of the exchange. For Classes 1 and 2, ACK frame is required to
be "continuous sequence".
4. Relative offset prohibited on all other types (Information
Category) of frames.
7.4 Sequences
+---------------------------------------------------------------------+
| Feature | Support |Notes |
+---------------------------------------------------------------------+
| Class 2 open Sequences / Exchange | 1 | 1 |
| Length of Seq. not limited by end-to-end credit | REQUIRED | 2 |
| IP and ARP Packet and FC Data Field sizes | REQUIRED | 3 |
| Capability to receive Sequence of maximum size | OPTIONAL | 4 |
| Sequence Streaming | MUST NOT | 5 |
| Stop Sequence Protocol | MUST NOT | |
| ACK_0 support | OPTIONAL | 6 |
| ACK_1 support | REQUIRED | 6 |
| ACK_N support | MUST NOT | |
| Class of Service for transmitted Sequences | Class | 7 |
| | 1, 2, or 3 | |
| Continuously Increasing Sequence Count | OPTIONAL | 8, 9 |
+---------------------------------------------------------------------+
Notes:
1. Only one active sequence per exchange is optional.
2. A Sequence Initiator shall be capable of transmitting Sequences
containing more frames than the available credit indicated by a
Sequence recipient at Login. FC-PH [2] end-to-end flow control
rules will be followed when transmitting such Sequences.
3. a) IP MTU size is 65280-bytes and resulting FC Sequence
Payload size is 65536-bytes.
b) Maximally Minimum IP Packet size is 68-bytes and resulting
FC Data Field size is 92-bytes.
c) ARP (and InARP) Packet size is 28-bytes and resulting FC
Data Field size is 52-bytes.
4. Some OS environments may not handle the max Sequence Payload
size of 65536. It is up to the administrator to configure the
Max size for all systems.
5. All class 3 sequences are assumed to be non-streamed.
6. Only applies for Class 1 and 2. Use of ACK_1 is default, ACK_0
used if indicated by Sequence recipient at Login.
7. The administrator configured class of service is used, except
where otherwise specified (e.g. Broadcasts are always sent in
Class 3).
8. Review Appendix F, "Reliability in Class 3".
9. The first frame of the first sequence of a new Exchange must
have SEQ_CNT = 0 [2].
7.5 Exchanges
+--------------------------------------------------------------------+
| Feature | Support | Notes |
+--------------------------------------------------------------------+
| X_ID interlock support | OPTIONAL | 1 |
| OX_ID=FFFF | MUST NOT | |
| RX_ID=FFFF | OPTIONAL | 2 |
| Action if no exchange resources available | P_RJT | 3 |
| Long Lived Exchanges | OPTIONAL | 4 |
| Reallocation of Idle Exchanges | OPTIONAL | |
+--------------------------------------------------------------------+
Notes:
1. Only applies to Classes 1 and 2, supported by the Exchange
Originator. A Port SHALL be capable of interoperating with
another Port that requires X_ID interlock. The Exchange
Originator facility within the Port shall use the X_ID
Interlock protocol in such cases.
2. An Exchange Responder is not required to assign RX_IDs. If a
RX_ID of FFFF is assigned, it is identifying Exchanges based on
S_ID / D_ID / OX_ID only.
3. In Classes 1 and 2, a Port shall reject a frame that would
create a new Exchange with a P_RJT containing reason code
"Unable to establish Exchange". In Class 3, the frame would be
dropped.
4. When an Exchange is created between 2 Ports for IP/ARP data, it
remains active while the ports are logged in with each other.
An Exchange SHALL NOT transfer Sequence Initiative (SI).
Broadcasts and ELS commands may use short lived Exchanges.
7.6 ARP and InARP
+--------------------------------------------------------------------+
| Feature | Support | Notes |
+--------------------------------------------------------------------+
| ARP Server Support | MUST NOT | 1 |
| Response to ARP requests | REQUIRED | 2 |
| Class of Service for ARP requests | Class 3 | 3 |
| Class of Service for ARP replies | Class | 4 |
| | 1, 2, or 3 | |
| Response to InARP requests | OPTIONAL | |
| Class of Service for InARP requests/replies | Class | |
| | 1, 2 or 3 | 5 |
+--------------------------------------------------------------------+
Notes:
1. Well-known Address FFFFFC is not used for ARP requests. Frames
from Well-known address FFFFFC are not considered to be ARP
frames. Broadcast support is REQUIRED for ARP.
2. The IP Address is mapped to a specific MAC address with ARP.
3. An ARP request is a Broadcast Sequence, therefore Class 3
is always used.
4. An ARP reply is a normal Sequence, thus the administrator
configured class of service is used.
5. An InARP Request or Reply is a normal Sequence, thus an
administrator configured class of service is used.
7.7 Extended Link Services (ELS)
+--------------------------------------------------------------------+
| Feature | Support | Notes |
+--------------------------------------------------------------------+
| Class of service for ELS commands / responses | Class | |
| | 1,2 or 3 | 1 |
| Explicit N-Port Login | REQUIRED | |
| Explicit F-Port Login | REQUIRED | |
| FLOGI ELS command | REQUIRED | |
| PLOGI ELS command | REQUIRED | |
| ADISC ELS command | REQUIRED | |
| PDISC ELS command | OPTIONAL | 2 |
| FAN ELS command | REQUIRED | 5 |
| LOGO ELS command | REQUIRED | |
| FARP-REQ/FARP-REPLY ELS commands | REQUIRED | 3 |
| Other ELS command support | OPTIONAL | 4 |
+-----------------------------------------------+------------+-------+
Notes:
1. The administrator configured class of service is used.
2. PDISC shall not be used as a Requester; ADISC shall be used
instead. As a Responder, an implementation may need to respond
to both ADISC and PDISC for compatibility with other
specifications.
3. Responder Action - FARP-REPLY and/or Port Login - for a
successful MATCH_WW_PN is always REQUIRED.
Support for all other match Address Codes Points is a silent
behavior from the Responder is valid when it is not supported.
Recipients of the FARP-REQ ELS shall not issue a Service Reject
(LS_RJT) if FARP is not supported.
4. If other ELS commands are received an LS_RJT may be sent. NOP
is not required by this specification, and shall not be used as
a mechanism to terminate exchanges.
5. Required for FL_Ports
7.8 Login Parameters
Unless explicitly noted here, a compliant implementation shall use
the login parameters as described in [4].
7.8.1 Common Service Parameters - FLOGI
- FC-PH Version, lowest version may be 0x09 to indicate
'minimum 4.3'.
- Can't use BB_Credit=0 for N_Port on a switched Fabric
(F_Port).
7.8.2 Common Service Parameters - PLOGI
- FC-PH Version, lowest version may be 0x09 to indicate
'minimum 4.3'.
- Can't use BB_Credit=0 for N_Port in a Point-to-Point
configuration
- Random Relative Offset is optional.
- Note that the 'Receive Data Field Size' fields specified in
the PLOGI represent both optional headers and payload.
- The MAC Address can therefore be extracted from the 6 lower
bytes of the WW_PN field (when the IEEE 48-bit Identifier
format is chosen as the NAA) during PLOGI or ACC payload
exchanged during Fibre Channel Login [2].
- The MAC Address can also be extracted from the WW_PN field in
the Network_Header during ADISC (and ADISC ACC), or PDISC
(and PDISC ACC).
7.8.3 Class Service Parameters - PLOGI
- Discard error policy only.
8. Security Considerations
8.1 IP and ARP Related
IP and ARP do not introduce any new security concerns beyond what
already exists within the Fibre Channel Protocols and Technology.
Therefore IP and ARP related Security does not require special
consideration in this document.
8.2 FC Related
FC Standards [11] specify a Security Key Server (independent of IP
and ARP) as an optional service. However, there are no known
implementations of this server yet. Also, the previously defined [2]
use of a Security Header has been discontinued [11].
9. Acknowledgement
This specification is based on FCA IP Profile, Version 3.3. The FCA
IP Profile was a joint work of the Fibre Channel Association (FCA)
vendor community. The following organizations or individuals have
contributed to the creation of the FCA IP Profile: Adaptec, Ancor,
Brocade, Clariion, Crossroads, emf Associates, Emulex, Finisar,
Gadzoox, Hewlett Packard, Interphase, Jaycor, McData, Migration
Associates, Orca Systems, Prisa, Q-Logic, Symbios, Systran,
Tektronix, Univ. of Minnesota, Univ. of New Hamshire. Jon Infante
from Emulex deserves special mention for his contributions to the
FARP Protocol. The authors extend their thanks to all who provided
comments and especially to Lansing Sloan from LLNL for his detailed
comments.
10. References
[1] FCA IP Profile, Revision 3.3, May 15, 1997
[2] Fibre Channel Physical and Signaling Interface (FC-PH) , ANSI
X3.230-1994
[3] Fibre Channel Link Encapsulation (FC-LE), Revision 1.1, June 26,
1996
[4] Fibre Channel Fabric Loop Attachment (FC-FLA), Rev. 2.7, August
12, 1997
[5] Fibre Channel Private Loop SCSI Direct Attach (FC-PLDA),
Rev. 2.1, September 22, 1997
[6] Fibre Channel Physical and Signaling Interface-2 (FC-PH-2),
Rev. 7.4, ANSI X3.297-1996
[7] Fibre Channel Arbitrated Loop (FC-AL), ANSI X3.272-1996
[8] Postel, J. and J. Reynolds, "A standard for the Transmission of
IP Datagrams over IEEE 802 Networks", STD 43, RFC1042, February
1988.
[9] Plummer, D. "An Ethernet Address Resolution Protocol -or-
Converting Network Addresses to 48-bit Ethernet Address for
Transmission on Ethernet Hardware", STD 37, RFC826, November
1982.
[10] FCSI IP Profile, FCSI-202, Revision 2.1, September 8, 1995
[11] Fibre Channel Physical and Signaling Interface -3 (FC-PH-3),
Rev. 9.3, ANSI X3.303-199x
[12] Fibre Channel-The Basics, "Gary R. Stephens and Jan V. Dedek",
Ancot Corporation
[13] Fibre Channel -Gigabit Communications and I/O for Computers
Networks "Alan Benner", McGraw-Hill, 1996, ISBN 0-07-005669-2
[14] Fibre Channel Generic Services -2 (FC-GS-2), Rev. 5.2
X3.288-199x
[15] Bradley, T. and C. Brown, "Inverse Address Resolution Protocol",
RFC1293, January 1992.
[16] Bradley, T., Brown, C. and A. Malis, "Inverse Address Resolution
Protocol", RFC2390, August 1992.
[17] Postel, J., "Internet Protocol", STD 5, RFC791, September 1981.
[18] The Fibre Channel Consultant: A Comprehensive Introduction,
"Robert W. Kembel", Northwest Learning Associates, 1998
[19] Bradner, S., "Key Words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC2119, March 1997.
[20] Narten, T. and C. Burton, "A Caution on The Canonical Ordering
of Link-Layer Addresses", RFC2469, December 1998.
11. Authors' Addresses
Murali Rajagopal
Gadzoox Networks, Inc.
711 Kimberly Avenue, Suite 100
Placentia, CA 92870
Phone: +1 714 577 6805
Fax: +1 714 524 8508
EMail: murali@gadzoox.com
Raj Bhagwat
Gadzoox Networks, Inc.
711 Kimberly Avenue, Suite 100
Placentia, CA 92870
Phone: +1 714 577 6806
Fax: +1 714 524 8508
EMail: raj@gadzoox.com
Wayne Rickard
Gadzoox Networks, Inc.
711 Kimberly Avenue, Suite 100
Placentia, CA 92870
Phone: +1 714 577 6803
Fax: +1 714 524 8508
EMail: wayne@gadzoox.com
Appendix A: Additional Matching Mechanisms in FARP
Section 5 described the FC Layer mapping between the WW_PN and the
Port_ID using the FARP Protocol. This appendix describes other
optional criteria for address matching and includes:
- WW_NN
- WW_PN & WW_NN at the same time
- IPv4
- IPv4 & WW_PN at the same time
- IPv4 & WW_NN at the same time
- IPv4 & WW_PN & WW_NN at the same time
Depending on the Match Address Code Points, the FARP protocol
fundamentally resolves three main types of addresses to Port_IDs and
is described in table below.
- For Match Address Code Point b'001': WW_PN Names fields are
used to resolve the WW_PN names to Port_IDs. WW_NN and IP
address fields are not used with these Code Points and SHALL be
set to either '0' or valid addresses by Requester or Requester
and Responder.
- For Match Address Code Point b'010': WW_NN Names fields are
used to resolve the WW_NN names to Port_IDs. WW_PN and IP
address fields are not used with these Code Points and SHALL be
set to either '0' or valid addresses by Requester or Requester
and Responder.
- For Match Address Code Point b'100': IPv4 fields are used to
resolve the IPv4 addresses to Port_IDs. WW_PN and WW_NN fields
are not used with these Code Points and SHALL be set to either '
0' or valid addresses by Requester or Requester and Responder.
- For all other Match Address Code Points b'011', b'101',b'110',
b'111', depending on set bits one or more addresses are jointly
resolved to a Port_ID. See table below. If fields are not used,
then they are set either to '0' or valid addresses.
The Responder Flags remain the same as before. Note that there can be
utmost one FARP-REPLY per FARP-REQ.
Tables showing FARP-REQ and FARP-REPLY and address fields setting are
given below:
+--------------------------------------------------------------------+
| Match Address Code Points |
+--------------------------------------------------------------------+
| LSBits| Bit name | Action |
+-------+--------------------+---------------------------------------+
| 000 | Reserved | |
+-------+--------------------+---------------------------------------+
| 001 | MATCH_WW_PN | If 'WW_PN of Responder' = |
| | | Node's WW_PN then respond |
+-------+--------------------+---------------------------------------+
| 010 | MATCH_WW_NN | If 'WW_NN of Responder' = |
| | | Node's WW_NN then respond |
+-------+--------------------+---------------------------------------+
| 011 | MATCH_WW_PN_NN | If both 'WW_PN of Responder' & |
| | | 'WW_NN of Responder' = |
| | | Node's WW_PN & WW_NN then respond |
+-------+--------------------+---------------------------------------+
| 100 | MATCH_IPv4 | If 'IPv4 Address of Responder' = |
| | | Node's IPv4 Address then respond |
+-------+--------------------+---------------------------------------+
| 101 | MATCH_WW_PN_IPv4 | If 'WW_PN & IPv4 of Responder' = |
| | | Node's WW_PN and IPv4 then respond |
+-------+--------------------+---------------------------------------+
| 110 | MATCH_WW_NN_IPv4 | If both 'WW_NN of Responder' & |
| | | 'IPv4 Address of Responder' = |
| | | Node's WW_NN & IPv4 then respond |
+-------+--------------------+---------------------------------------+
| 111 |MATCH_WW_PN_NN_IPv4 | If 'WW_PN of Responder' & |
| | | 'WW_NN of Responder' & |
| | | 'IPv4 Address of Responder' = |
| | | Nodes' WW_PN & WW_NN & IPv4 |
| | | then respond |
+-------+--------------------+---------------------------------------+
+---------------------------------------------------------------------+
| FARP-REQ Command |
+-------------------------------+---------+---------------------------+
| Field | Size | Remarks |
| | (Bytes) | |
+-------------------------------+---------+---------------------------+
| 0x54-00-00-00 | 4 | Request Command Code |
+-------------------------------+---------+---------------------------+
| Match Address Code Points | 1 | Indicates Address |
| | | Matching Mechanism |
+-------------------------------+---------+---------------------------+
| Port_ID of Requester | 3 |Supplied by Requester |
+-------------------------------+---------+---------------------------+
| Responder Flags | 1 |Response Action to be taken|
+-------------------------------+---------+---------------------------+
| Port_ID of Responder | 3 | Set to 0x00-00-00 |
+-------------------------------+---------+---------------------------+
|WW_PN of Requester | 8 | Supplied by Requester |
+-------------------------------+---------+---------------------------+
|WW_NN of Requester | 8 |OPTIONAL; |
| | |Supplied by Requester |
+-------------------------------+---------+---------------------------+
|WW_PN of Responder | 8 |Supplied by Requester |
+-------------------------------+---------+---------------------------+
|WW_NN of Responder | 8 |OPTIONAL ;Supplied by |
| | |Requester or Responder |
+-------------------------------+---------+---------------------------+
|IP Add. of Requester | 16 |OPTIONAL; Supplied by |
| | |Requester |
| | |IPv4 Add.=low 32 bits |
+-------------------------------+---------+---------------------------+
|IP Address of Responder | 16 |OPTIONAL; Supplied by |
| | |Requester or Responder |
| | |IPv4 Add.=low 32 bits |
+-------------------------------+---------+---------------------------+
+---------------------------------------------------------------------+
| FARP-REPLY Command |
+-------------------------------+---------+---------------------------+
| Field | Size | Remarks |
| | (Bytes) | |
+-------------------------------+---------+---------------------------+
| 0x55-00-00-00 | 4 |Reply Command Code |
+-------------------------------+---------+---------------------------+
| Match Address Code Points | 1 | Not Used and unchanged |
| | |from the FARP-REQ |
+-------------------------------+---------+---------------------------+
| Port_ID of Requester | 3 |Supplied by Requester |
+-------------------------------+---------+---------------------------+
| Responder Flags | 1 | Not Used and unchanged |
| | |from the FARP-REQ |
+-------------------------------+---------+---------------------------+
| Port_ID of Responder | 3 |Supplied by Responder |
+-------------------------------+---------+---------------------------+
|WW_PN of Requester | 8 |Supplied by Requester |
+-------------------------------+---------+---------------------------+
|WW_NN of Requester | 8 |OPTIONAL; Supplied by |
| | |Requester |
+-------------------------------+---------+---------------------------+
|WW_PN of Responder | 8 |Supplied by Requester |
+-------------------------------+---------+---------------------------+
|WW_NN of Responder | 8 |OPTIONAL; Supplied by |
| | |Requester or Responder |
+-------------------------------+---------+---------------------------+
|IP Add. of Requester | 16 |OPTIONAL; Supplied by |
| | |Requester |
| | |IPv4 Add.=low 32 bits |
+-------------------------------+---------+---------------------------+
|IP Address of Responder | 16 |OPTIONAL; Supplied by |
| | |Requester or Responder |
| | |IPv4 Add.=low 32 bits |
+-------------------------------+---------+---------------------------+
Appendix B: InARP
B.1 General Discussion
Inverse ARP (InARP) is a mechanism described in RFC1293/2390 [15,
16], which is useful when a node desires to know the protocol address
of a target node whose hardware address is known. Situations where
this could occur are described in [15, 16]. The motivation for using
InARP in FC is to allow a node to learn the IP address of another
node with which it has performed a Port Login (PLOGI). PLOGI is a
normal FC process that happens between nodes, independent of this
standard. PLOGI makes it possible for a node to discover the WW_PN
and the Port_ID of the other node but not its IP address. A node in
this way may potentially obtain the IP address of all nodes with
which it can PLOGI.
Note that the use of the InARP mechanism can result in resolving all
WW_PN to IP addresses and ARP may no longer be required. This can be
beneficially applied in cases where a particular FC topology makes it
inefficient to send out an ARP broadcast.
B.2 InARP Protocol Operation
InARP uses the same ARP Packet format but with different 'Op Codes',
one for InARP Request and another for InARP Reply.
The InARP protocol operation is very simple. The requesting node
fills the hardware address (WW_PN) of the target device and sets the
protocol address to 0x00-00-00-00. Because, the request is sent to a
node whose WW_PN and Port_ID are known, there is no need for a
broadcast. The target node fills in its Protocol address (IP address
in this case) and sends an InARP Reply back to the sender. A node
may collect, all such WW_PN and IP addresses pairs in a similar way.
B.3 InARP Packet Format
Since the InARP protocol uses the same packet format as the ARP
protocol, much of the discussion on ARP formats given in Section 4
applies here.
The InARP is 28-bytes long in this application and uses two packet
types: Request and Reply. Like ARP, the InARP Packet fields are
common to both InARP Requests and InARP Replies.
InARP Request and Reply Packets are encapsulated in a single frame FC
Sequence much like ARP. Compliant InARP Request and Reply FC
Sequences SHALL include Network_Headers.
The 'HW Type' field SHALL be set to 0x00-01.
The 'Protocol' field SHALL be set to 0x08-00 indicating IP protocol.
The 'HW Addr Length' field SHALL be set to 0x06 indicating 6-bytes of
HW address.
The 'Protocol Addr Length' field SHALL be set to 0x04 indicating
4-bytes of IP address.
The 'Operation' Code field SHALL be set as follows:
0x00-08 for InARP Request
0x00-09 for InARP Reply
The 'HW Addr of Sender' field SHALL be the 6-byte IEEE MAC address of
the Requester (InARP Request) or Responder (InARP Reply).
The 'Protocol Addr of Sender' field SHALL be the 4-byte IP address of
the Requester (InARP Request) or Responder (InARP Reply).
The 'HW Addr of Target' field SHALL be set to the 6-byte MAC address
of the Responder in an InARP Request and to the 6-byte MAC address of
the Requester in an InARP Reply.
The 'Protocol Addr of Target' field SHALL be set to 0x00-00-00-00 in
an InARP Request and to the 4-byte IP address of the Requester in an
InARP Reply.
B.4 InARP Support Requirements
Support for InARP is OPTIONAL. If a node does not support InARP and
it receives an InARP Request message then a silent behavior is
specified.
APPENDIX C: Some Informal Mechanisms for FC Layer Mappings
Each method SHALL have some check to ensure PLOGI has completed
successfully before data is sent. A related concern in large networks
is limiting concurrent logins to only those ports with active IP
traffic.
C.1 Login on Cached Mapping Information
This method insulates the level performing Login from the level
interpreting ARP. It is more accommodating of non-ARP mechanisms for
building the FC-layer mapping table.
1. Broadcast messages that carry a Network_Header contain the S_ID
on the FC-header and WW_PN in the Network-Header. Caching this
information provides a correlation of Port_ID to WW_PN. If the
received Broadcast message is compliant with this
specification, the WW_PN will contain the MAC Address.
2. The WW_PN is "available" if Login has been performed to the
Port_ID and flagged. If Login has not been performed, the WW_PN
is "unavailable".
3. If an outbound packet is destined for a port that is
"unavailable", the cached information (from broadcast) is used
to look up the Port_ID.
4. After sending an ELS PLOGI command (Port Login) to the Port
(from a higher level entity at the host), waiting for an
outbound packet before sending this Port Login conserves
resources for only those ports which wish to establish
communication.
5. After Port Login completes (ACC received), the outbound packet
can be forwarded. At this point in time, both ends have the
necessary information to complete their <IP address, MAC
Address, Port_ID> association.
C.2 Login on ARP Parsing
This method performs Login sooner by parsing ARP before passing it up
to higher levels for IP/MAC Address correlation. It requires a low-
level awareness of the IP address, and is therefore protocol-
specific.
1. When an ARP Broadcast Message is received, the S_ID is
extracted from the FC-header and the corresponding
Network_Source_Address from the Network_Header.
2. The ARP payload is parsed to determine if
(a) this host is the target of the ARP request (Target IP
Address match), and
(b) if this host is currently logged in with the port
(Port_ID = S_ID) originating the ARP broadcast.
3. The ARP is passed to a higher level for ARP Response
generation.
4. If a Port Login is required, an ELS PLOGI command (Port Login)
is sent immediately to the Port originating the ARP Broadcast.
5. After Port Login completes, an ARP response can be forwarded.
Note that there are two possible scenarios:
- The ACC to PLOGI returns before the ARP reply is processed
and the ARP Reply is immediately forwarded.
- The ARP reply is delayed, waiting for ACC (successful
Login).
6. At this point in time, both ends have the necessary
information to complete their
<IP address, MAC Address, Port_ID> association.
C.3 Login to Everyone
In Fibre Channel topologies with a limited number of ports, it may be
efficient to unconditionally Login to each port. This method is
discouraged in fabric and public loop environments.
After Port Login completes, the MAC Address to Port_ID Address tables
can be constructed.
C.4 Static Table
In some loop environments with a limited number of ports, a static
mapping from a MAC Address to Port_ID (D_ID or AL_PA) may be
maintained. The FC layer will always know the destination Port_ID
based on the table. The table is typically downloaded into the driver
at configuration time. This method scales poorly, and is therefore
not recommended.
Appendix D: FC Layer Address Validation
D.1 General Discussion
At all times, the <WW_PN, Port_ID> mapping MUST be valid before use.
There are many events that can invalidate this mapping. The
following discussion addresses conditions when such a validation is
required.
After a FC link interruption occurs, the Port_ID of a port may
change. After the interruption, the Port_IDs of all other ports that
have previously performed PLOGI (N_Port Login) with this port may
have changed, and its own Port_ID may have changed.
Because of this, address validation is required after a LIP in a loop
topology [7] or after NOS/OLS in a point-to-point topology [6].
Port_IDs will not change as a result of Link Reset (LR),thus address
validation is not required.
In addition to actively validating devices after a link interruption,
if a port receives any FC-4 data frames (other than broadcast
frames), from a port that is not currently logged in, then it shall
send an explicit Extended Link Service (ELS) Request logout (LOGO)
command to that port.
ELS commands (Requests and Replies) are used by an N_Port to solicit
a destination port (F_Port or N_Port) to perform some link-level
function or service.) The LOGO Request is used to request
invalidation of the service parameters and Port_ID of the recipient
N_Port.
The level of initialization and subsequent validation and recovery
reported to the upper (FC-4) layers is implementation-specific.
In general, an explicit Logout (LOGO) SHALL be sent whenever the FC-
Layer mapping between the Port_ID and WW_PN of a remote port is
removed.
The effect of power-up or re-boot on the mapping tables is outside
the scope of this specification.
D.2 FC Layer Address Validation in a Point-to-Point Topology
No validation is required after LR. In a point-to-point topology,
NOS/OLS causes implicit Logout of each port and after a NOS/OLS, each
port must perform a PLOGI [2].
D.3 FC Layer Address Validation in a Private Loop Topology
After a LIP, a port SHALL not transmit any link data to another port
until the address of the other port has been validated. The
validation consists of completing either ADISC or PDISC. (See
Appendix G.)
ADISC (Address Discovery) is an ELS command for discovering the hard
addresses - the 24-bit identifier- of NL_Ports [5], [6].
PDISC (Discover Port) is an ELS command for exchanging service
parameters without affecting Login state [5], [6].
As a requester, this specification prohibits PDISC and requires
ADISC.
As a responder, an implementation may need to respond to both ADISC
and PDISC for compatibility with other FC specifications.
If the three addresses, Port_ID, WW_PN, WW_NN, exactly match the
values prior to the LIP, then any active exchanges may continue.
If any of the three addresses have changed, then the node must be
explicitly Logged out [4], [5].
If a port's N_Port ID changes after a LIP, then all active Port-ID to
WW_PN mappings at this port must be explicitly Logged out.
D.4 FC Layer Address Validation in a Public Loop Topology
A FAN (Fabric Address Notification) ELS command is sent by the fabric
to all known previously logged in ports following an initialization
event. Therefore, after a LIP, hosts may wait for this notification
to arrive or they may perform a FLOGI.
If the WW_PN and WW_NN of the fabric FL_Port contained in the FAN ELS
or FLOGI response exactly match the values before the LIP, and if the
AL_PA obtained by the port is the same as the one before the LIP,
then the port may resume all exchanges. If not, then FLOGI (Fabric
Login) must be performed with the fabric and all nodes must be
explicitly Logged out.
A public loop device will have to perform the private loop
authentication to any nodes on the local loop which have an Area +
Domain Address == 0x00-00-XX
D.5 FC Layer Address Validation in a Fabric Topology
No validation is required after LR (link reset).
After NOS/OLS, a port must perform FLOGI. If, after FLOGI, the S_ID
of the port, the WW_PN of the fabric, and the WW_NN of the fabric are
the same as before the NOS/OLS, then the port may resume all
exchanges. If not, all nodes must be explicitly, Logged out [2].
APPENDIX E: Fibre Channel Overview
E.1 Brief Tutorial
The FC Standard [2] defines 5 "levels" (not layers) for its protocol
description: FC-0, FC-1, FC-2, FC-3, and FC-4. The first three levels
(FC-0, FC-1, FC-2) are largely concerned with the physical formatting
and control aspects of the protocol. FC-3 has been architected to
provide a place holder for functions that might need to be performed
after the upper layer protocol has requested the transmission of an
information unit, but before FC-2 is asked to deliver that piece of
information by using a sequence of frames [18]. At this time, no FC-3
functions have been defined. FC-4 is meant for supporting profiles
of Upper Layer Protocols (ULP) such as IP and Small Computer System
Interface (SCSI), and supports a relatively small set compared to LAN
protocols such as IEEE 802.3.
FC devices are called "Nodes", each of which has at least one "Port"
to connect to other ports. A Node may be a workstation, a disk drive
or disk array, a camera, a display unit, etc. A "Link" is two
unidirectional paths flowing in opposite directions and connecting
two Ports within adjacent Nodes.
FC Nodes communicate using higher layer protocols such as SCSI and IP
and are configured to operate using Point-to-Point, Private Loop,
Public Loop (attachment to a Fabric), or Fabric network topologies.
The point-to-point is the simplest of the four topologies, where only
two nodes communicate with each other. The private loop may connect a
number of devices (max 126) in a logical ring much like Token Ring,
and is distinguished from a public loop by the absence of a Fabric
Node participating in the loop. The Fabric topology is a switched
network where any attached node can communicate with any other. For a
detail description of FC topologies refer to [18].
Table below summarizes the usage of port types depending on its
location [12]. Note that E-Port is not relevant to any discussion in
this specification but is included below for completeness.
+-----------+-------------+-----------------------------------------+
| Port Type | Location | Topology Associated with |
+-----------+-------------+-----------------------------------------+
| N_Port | Node | Point-to-Point or Fabric |
+-----------+-------------+-----------------------------------------+
| NL_Port | Node |In N_Port mode -Point-to-Point or Fabric |
| | |In NL_Port mode - Arbitrated Loop |
+-----------+-------------+-----------------------------------------+
| F_Port | Fabric | Fabric |
+-----------+-------------+-----------------------------------------+
| FL_Port | Fabric | In F_Port mode - Fabric |
| | | In FL_Port mode - Arbitrated Loop |
+-----------+-------------+-----------------------------------------+
| E_Port | Fabric | Internal Fabric Expansion |
+-----------+-------------+-----------------------------------------+
E.2 Exchange, Information Unit, Sequence, and Frame
The FC 'Exchange' is a mechanism used by two FC ports to identify and
manage an operation between them [18]. An Exchange is opened whenever
an operation is started between two ports. The Exchange is closed
when this operation ends.
The FC-4 Level specifies data units for each type of application
level payload called 'Information Unit' (IU). Each protocol carried
by FC has a defined size for the IU. Every operation must have at
least one IU. Lower FC levels map this to a FC Sequence.
Typically, a Sequence consists of more than one frame. Larger user
data is segmented and reassembled using two methods: Sequence Count
and Relative Offset [18]. With the use of Sequence Count, data blocks
are sent using frames with increasing sequence counts (modulo 65536)
and it is quite straightforward to detect the first frame that
contains the Network_Header. When Relative Offset is used, as frames
arrive, some computation is required to detect the first frame that
contains the Network_Header. Sequence Count and Relative Offset field
control information, is carried in the FC Header.
The FC-4 Level makes a request to FC-3 Level when it wishes it to be
delivered. Currently, there are no FC-3 level defined functions, and
this level simply converts the Information Unit delivery request into
a 'Sequence' delivery request and passes it on to the FC-2 Level.
Therefore, each FC-4 Information Unit corresponds to a FC-2 Level
Sequence.
The maximum data carried by a FC frame cannot exceed 2112-bytes [2].
Whenever, the Information Unit exceeds this value, the FC-2 breaks it
into multiple frames and sends it in a sequence.
There can be multiple Sequences within an Exchange. Sequences within
an Exchange are processed sequentially. Only one Sequence is active
at a time. Within an Exchange information may flow in one direction
only or both. If bi-directional then one of the ports has the
initiative to send the next Sequence for that Exchange. Sequence
Initiative can be passed between the ports on the last frame of
Sequence when control is transferred. This amounts to half-duplex
behavior.
Ports may have more than one Exchange open at a time. Ports can
multiplex between Exchanges. Exchanges are uniquely identified by
Exchange IDs (X_ID). An Originator OX_ID and a Responder RX_ID
uniquely identify an Exchange.
E.3 Fibre Channel Header Fields
The FC header as shown in the diagrams below contains routing and
other control information to manage Frames, Sequences, and Exchanges.
The Frame-header is sent as 6 transmission words immediately
following an SOF delimiter and before the Data Field.
D_ID and S_ID:
FC uses destination address routing [12], [13]. Frame routing in a
point-to-point topology is trivial.
For the Arbitrated Loop topology, with the destination NL_Port on
the same AL, the source port must pick the destination port,
determine its AL Physical Address, and "Open" the destination
port. The frames must pass through other NL_Ports or the FL_Port
on the loop between the source and destination, but these ports do
not capture the frames. They simply repeat and transmit the frame.
Either communicating port may "Close" the circuit.
When the destination port is not on the same AL, the source
NL_Port must open the FL_Port attached to a Fabric. Once in the
Fabric, the Fabric routes the frames again to the destination.
In a Fabric topology, the Fabric looks into the Frame-header,
extracts the destination address (D_ID), searches its own routing
tables, and sends the frame to the destination port along the path
chosen. The process of choosing a path may be performed at each
fabric element or switch until the F_Port attached to the
destination N_Port is reached.
Fibre Channel Frame Header, Network_Header, and Payload carrying IP
Packet
+---+----------------+----------------+----------------+--------------+
|Wrd| <31:24> | <23:16> | <15:08> | <07:00> |
+---+----------------+----------------+----------------+--------------+
|0 | R_CTL | D_ID |
+---+----------------+----------------+----------------+--------------+
|1 | CS_CTL | S_ID |
+---+----------------+----------------+----------------+--------------+
|2 | TYPE | F_CTL |
+---+----------------+----------------+----------------+--------------+
|3 | SEQ_ID | DF_CTL | SEQ_CNT |
+---+----------------+----------------+----------------+--------------+
|4 | OX_ID | RX_ID |
+---+--------+-------+----------------+----------------+--------------+
|5 | Parameter (Control or Relative Offset for Data ) |
+---+-----------------------------------------------------------------+
|6 | NAA | Network_Dest_Address (Hi order bits) |
+---+--------+-------+----------------+----------------+--------------+
|7 | Network_Dest_Address (Lo order bits) |
+---+--------+-------+----------------+----------------+--------------+
|8 | NAA | Network_Src_Address (Hi order bits) |
+---+--------+-------+----------------+----------------+--------------+
|9 | Network_Src_Address (Lo order bits) |
+---+----------------+----------------+----------------+--------------+
|10 | DSAP | SSAP | CTRL | OUI |
+---+----------------+----------------+----------------+--------------+
|11 | OUI | PID |
+---+----------------+----------------+----------------+--------------+
|12 | IP Packet Data ... |
+---+----------------+----------------+----------------+--------------+
R_CTL (Routing Control) and TYPE(data structure):
Frames for each FC-4 can be easily distinguished from the others
at the receiving port using the R_CTL (Routing Control) and TYPE
(data structure) fields in the Frame-header.
The R_CTL has two sub-fields: Routing bits and Information
category. The Routing bits sub-field has specific values that mean
FC-4 data follows and the Information Category tells the receiver
the "Type" of data contained in the frame. The R_CTL and TYPE code
points are shown in the diagrams.
Other Header fields:
F_CTL (Frame Control) and SEQ_ID (Sequence Identification),
SEQ_CNT (Sequence Count), OX_ID (Originator exchange Identifier),
RX_ID (Responder exchange Identifier), and Parameter fields are
used to manage the contents of a frame, and mark information
exchange boundaries for the destination port.
F_CTL(Frame Control):
The FC_CTL field is a 3-byte field that contains information
relating to the frame content. Most of the other Frame-header
fields are used for frame identification. Among other things, bits
in this field indicate the First Sequence, Last Sequence, or End
Sequence. Sequence Initiative bit is used to pass control of the
next Sequence in the Exchange to the recipient.
SEQ_ID (Sequence Identifier) and SEQ_CNT (Sequence Count):
This is used to uniquely identify sequences within an Exchange.
The <S_ID, D_ID, SEQ_ID> uniquely identifies any active Sequence.
SEQ_CNT is used to uniquely identify frames within a Sequence to
assure sequentiality of frame reception, and to allow unique
correlation of link control frames with their related data frames.
Originator Exchange Identifier (OX_ID) and Responder Exchange
Identifier (RX_ID):
The OX_ID value provides association of frames with specific
Exchanges originating at a particular N_Port. The RX_ID field
provides the same function that the OX_ID provides for the
Exchange Originator. The OX_ID is meaningful on the Exchange
Originator, and the RX_ID is meaningful on the Responder.
DF_CTL (Data Field Control):
The DF_CTL field specifies the presence or absence of optional
headers between the Frame-header and Frame Payload
PARAMETER:
The Parameter field has two meanings, depending on Frame type.
For Link Control Frames, the Parameter field indicates the
specific type of Link Control frame. For Data frames, this field
contains the Relative Offset value. This specifies an offset from
an Upper Layer Protocol buffer from a base address.
E.4 Code Points for FC Frame
E.4.1 Code Points with IP and ARP Packets
The Code Points for FC Frames with IP and ARP Packets are very
similar with the exception of PID value in Word 11 which is set to
0x08-00 for IP and 0x08-06 for ARP. Also, the Network_Header appears
only in the first logical frame of a FC Sequence carrying IP. In the
case, where FC frames carry ARP packets it is always present because
these are single frame Sequences.
Code Points for FC Frame with IP packet Data
+---+----------------+----------------+----------------+------------+
|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 | 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 | 0x08-00 |
+---+----------------+----------------+----------------+------------+
|12 | IP Packet Data |
+---+----------------+----------------+----------------+------------+
|13 | ... |
+---+----------------+----------------+----------------+------------+
Code Points for FC Frame with ARP packet Data
+---+----------------+----------------+----------------+------------+
|Wrd| <31:24> | <23:16> | <15:08> | <07:00> |