As per Relevance of the word exchange, we have this rfc below:
Network Working Group M.
Request for Comments: 2625 R.
Category: Standards Track W.
Gadzoox
June 1999
IP and ARP over Fibre
Status of this
This document specifies an Internet standards track protocol for
Internet community, and requests discussion and suggestions
improvements. Please refer to the current edition of the "
Official Protocol Standards" (STD 1) for the standardization
and status of this protocol. Distribution of this memo is unlimited
Copyright
Copyright (C) The Internet Society (1999). All Rights Reserved
Fibre Channel (FC) is a high speed serial interface technology
supports several higher layer protocols including Small
System Interface (SCSI) and Internet Protocol(IP). Until now,
has been the only widely used protocol over FC. Existing FC
[3] do not adequately specify how IP packets may be transported
FC and how IP addresses are resolved to FC addresses. The purpose
this document is to specify a way of encapsulating IP and
Resolution Protocol(ARP) over Fibre Channel and also to describe
mechanism(s) for IP address resolution
Table of
1. Introduction ............................................... 3
2. Problem Statement .......................................... 5
3. IP and ARP Encapsulation ................................... 5
3.1 FC Frame Format ........................................ 5
3.2 MTU .................................................... 7
3.2.1 IP MTU ........................................... 7
3.2.2 Maximally Minimum IPv4 packet .................... 8
3.2.3 ARP MTU .......................................... 8
3.2.4 FC Data Field containing FARP Packet ............. 9
3.3 FC Port and Node Network Addresses ..................... 9
3.4 FC Sequence Payload Format ............................. 10
3.5 Bit and Byte Ordering .................................. 12
4. ARP ........................................................ 12
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4.1 Address Resolution .................................... 12
4.2 ARP Packet Format ...................................... 13
4.3 ARP Layer Mapping and Operation ........................ 15
4.4 ARP Broadcast in a Point-to-Point Topology ............. 16
4.5 ARP Broadcast in a Private Loop Topology ............... 16
4.6 ARP Broadcast in a Public Loop Topology ................ 16
4.7 ARP Operation in a Fabric Topology ..................... 17
5. FARP ....................................................... 18
5.1 Scope .................................................. 18
5.2 FARP Overview .......................................... 18
5.3 FARP Command Format .................................... 20
5.4 Match Address Code Points .............................. 22
5.5 Responder Flags ........................................ 23
5.6 FARP Support Requirements .............................. 24
6. Exchange Management ........................................ 25
6.1 Exchange Origination ................................... 25
6.2 Exchange Termination ................................... 25
7. Summary of Supported Features .............................. 25
7.1 FC-4 Header ............................................ 25
7.2 R_CTL .................................................. 26
7.3 F_CTL .................................................. 27
7.4 Sequences .............................................. 28
7.5 Exchanges .............................................. 29
7.6 ARP and InARP ......................................... 30
7.7 Extended Link Services (ELS) ........................... 31
7.8 Login Parameters ....................................... 31
7.8.1 Common Service Parameters - FLOGI ............... 32
7.8.2 Common Services Parameters - PLOGI ............... 32
7.8.3 Class Service Parameters - PLOGI ................. 32
8. Security Considerations .................................... 32
8.1 IP and ARP Related ..................................... 32
8.2 FC Related ............................................. 32
9. Acknowledgements ........................................... 33
10. References ................................................ 33
11. Authors' Addresses ........................................ 35
Appendix A: Additional Matching Mechanisms in FARP ............ 36
Appendix B: InARP ............................................. 40
B.1 General Discussion ..................................... 40
B.2 InARP Protocol Operation ............................... 40
B.3 InARP Packet Format .................................... 40
B.4 InARP Support Requirements ............................. 41
Appendix C: Some Informal Mechanisms for FC Layer Mappings .... 42
C.1 Login on cached Mapping Information .................... 42
C.2 Login on ARP parsing ................................... 42
C.3 Login to Everyone ...................................... 43
C.4 Static Table ........................................... 43
Appendix D: FC Layer Address Validation........................ 44
D.1 General Discussion ..................................... 44
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D.2 FC Layer Address Validation in a Point-to-Point Topology 45
D.3 FC Layer Address Validation in a Private Loop Topology . 45
D.4 FC Layer Address Validation in a Public Loop Topology .. 45
D.5 FC layer Address Validation in a Fabric Topology ....... 46
Appendix E: Fibre channel Overview ............................ 47
E.1 Brief Tutorial ......................................... 47
E.2 Exchange, Information Unit, Sequence, and Frame ........ 48
E.3 Fibre Channel Header Fields ............................ 49
E.4 Code Points for FC Frame ............................... 52
E.4.1 Code Points with IP and ARP Packet .............. 52
E.4.2 Code Points with FARP Command ................... 54
Appendix F: Fibre Channel Protocol Considerations.............. 58
F.1 Reliability in Class 3 ................................. 58
F.2 Continuously Increasing SEQ_CNT ........................ 58
Appendix G: Acronyms and Glossary of FC Terms ................. 60
Full Copyright Statement ...................................... 63
1.
Fibre Channel (FC) is a gigabit speed networking technology
used for Storage Area Networking (SAN). FC is standardized
American National Standard for Information Systems of the
Committee for Information Technology Standards (NCITS) and
specified a number of documents describing its protocols, operations
and services
Need
Currently, Fibre Channel is predominantly used for
between storage devices and servers using the SCSI protocol,
most of the servers still communicating with each other over LANs
Although, there exists a Fibre Channel Standard [3] that
architecturally defined support for IP encapsulation and
resolution, it is inadequately specified. ([3] prohibits broadcasts
thus loops are not covered; [10] has no support for Class 3).
This has lead to a nonstandard way of using IP over FC in the past
Once such a standard method is completely specified, servers
directly communicate with each other using IP over FC,
boosting performance in Server host-to-host communications.
technique will be especially useful in a Clustering Application
Objective and Scope
The major objective of this specification is to promote
implementations of IPv4 over FC. This specification describes
method for encapsulating IPv4 and Address Resolution Protocol (ARP
packets over FC. This specification accommodates any FC
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(loop, fabric, or point-to-point) and any FC class of service (1, 2
or 3). This specification also describes a FC Address
Protocol(FARP) for associating World Wide Port Names (MAC addresses
and FC Port identifiers
A secondary objective of this specification is to describe
optional address resolution mechanisms
- Other FARP mechanisms that directly build IPv4 address and
Port Identifier (Port_ID) associations
- Inverse ARP (InARP) that allows learning the IP address of
remote node given its World Wide Port Name (WW_PN) and Port_ID
"Multicasting" in Fibre Channel is defined as an optional
[11] for FC Classes 3 and 6 only, with no definition for Classes 1
and 2. Currently, there are no vendor implementations of this
for either Class of service. Broadcast service available within
Channel can be used to do multicasting, although less efficiently
Presently, there appears to be no IP applications over Fibre
that require support for IP multicasting. This
therefore does not support IP Multicasting
Organization
Section 2 states the problem that is solved in this specification
Section 3 describes the techniques used for encapsulating IP and
packets in a FC sequence. Section 4 discusses the ARP protocol(
address to WW_PN). Section 5 discusses the FARP protocol used in
Layer mappings (WW_PN to Port_ID). Section 6 describes
"Exchange" Management in FC. Section 7 is a summary section
provides a quick reference to FC header settings, FC Link
Commands, supported features in ARP, FARP, InARP, FC Sequences,
Exchanges, and FC Login Parameters. Section 8 discusses security
Section 9 acknowledges the technical contributors of this document
Section 10 provides a list of references, and Section 11 provides
authors' addresses
Appendix A discusses other optional FARP mechanisms. Appendix
discusses the Inverse ARP protocol(WW_PN to IP address) as
alternate and optional way of building MAC and IP
associations. Appendix C lists some informal mechanisms for FC
Mappings. Appendix D provides a discussion on validation of the FC
layer mappings for the different FC topologies. Appendix E
a brief overview of the FC Protocols and Networks. Appendix
addresses reliability in Class 3 and Sequence Count FC
issues. Appendix G provides a list of acronyms and a glossary of
Terms used in this specification
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The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in
document are to be interpreted as described in RFC 2119 [19].
2. Problem
This specification addresses two problems
- A format definition and encapsulation mechanism for IPv
and ARP packets over
- Mechanisms for Address
As noted earlier, the existing FC Standard [3] ([10]) is
to solve the above problems. A solution to both problems was
proposed by the Fibre Channel Association (FCA)[1]. FCA is
industry consortium of FC vendor companies and not a Standards Body
This specification is based on the proposed solution in [1]
builds on it
Address Resolution is concerned with resolving IP addresses to WW_
(MAC address) and WW_PN to FC Port Identifiers (Port_ID).
provides a solution to the first resolution problem and FARP
second
An optional FARP mechanism resolves IP address directly to
Port_IDs. This is useful in some upper layer applications
InARP is another optional mechanism that resolves WW_PN and Port_
to an IP address. InARP is useful when a node after performing
PLOGI with another node, knows its WW_PN and Port_ID, but not its
address
3. IP and ARP
3.1 FC Frame
All FC frames have a standard format much like LAN 802.x protocols
(See Appendix E and F). However, the exact size of each frame
depending on the size of the variable fields. The size of
variable field ranges from 0 to 2112-bytes as shown in the FC
Format in Fig. 1.
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+------+--------+-----------+----//-------+------+------+
| SOF |Frame |Optional | Frame | CRC | EOF |
| (4B) |Header |Header | Payload | (4B) | (4B) |
| |(24B) |<----------------------->| | |
| | | Data Field = (0-2112B) | | |
+------+--------+-----------+----//-------+------+------+
Fig. 1 FC Frame
The Start of Frame (SOF) and End of Frame (EOF) are both 4-bytes
and act as frame delimiters
The CRC is 4-bytes long and uses the same 32-bit polynomial used
FDDI and is specified in ANSI X3.139 Fiber Distributed
Interface
The Frame Header is 24-bytes long and has several fields that
associated with the identification and control of the payload.
of the values and options for this field that are relevant to the
and ARP payloads are discussed in Section 7.
Current FC Standards allow up to 3 Optional Header fields [11]:
- Network_Header (16-bytes
- Association_Header (32-bytes
- Device_Header (up to 64-bytes).
The IP and ARP FC Sequences SHALL carry only the Network_Header
which is 16-bytes long. Other types of optional headers SHALL NOT
used. The Network_Header is REQUIRED in all ARP packets and in
first frame of a logical sequence carrying an IP payload as
below
An application level payload such as IP is called an Information
at the FC-4 Level. Lower FC levels map this to a FC Sequence. (
Appendix E.2 for a description of Sequences and Information Units.)
Typically, a Sequence consists of more than one frame. Larger
data is segmented and reassembled using two methods: Sequence
and Relative Offset [18]. With the use of Sequence Count, data
are sent using frames with increasing sequence counts (modulo 65536)
and it is quite straightforward to detect the first frame
contains the Network_Header. When Relative Offset is used, as
arrive, some computation is required to detect the first frame
contains the Network_Header. Sequence Count and Relative Offset
control information, is carried in the FC Header
In FC, the physical temporal ordering of the frames as it arrives
a destination can be different from that of the order sent because
traversing through a FC Network
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When IP forms the FC Payload then only the first frame of the
Sequence SHALL include the FC Network_Header. Fig. 2 shows
logical First Frame and logical subsequent frames. Since frames
arrive out of order, detection of the first frame of the logical
Sequence is necessary
ARP packets map to a single frame FC Sequence and SHALL always
the FC Network_Header
Note the definition of FC Data Field and FC Frame Payload in Fig. 1.
FC Data Field includes the FC Frame Payload and the FC
Header, that is, Frame Payload definition does not include the
Optional Header. One or more Frame Payloads together make the
Sequence Payload as shown in Fig 2 and discussed further in
3.2 and 3.4. FC Sequence Payload includes the mapped IP or ARP
along with the LLC/SNAP headers
First Frame of a Logical FC
---+------------+---------------------------+----------//----------+---
| FC Header | FC Network_Header | FC Sequence Payload |
---+------------+---------------------------+---------//-----------+---
Subsequent Frames of a Logical FC
--+-----------+--------------//----------------+--
| FC Header | Additional FC Sequence Payload |
--+-----------+-------------//-----------------+--
Fig. 2 FC Network_Header in a Frame
The SOF, CRC, EOF control fields of the FC frame and other
headers have been omitted in the figure for clarity
3.2
3.2.1 IP
An FC Information Unit specific to each protocol such as IP
defined in FC-4. This defines the upper bound on the size of
information that can be transported
Each IP or ARP Packet is mapped to a single FC Information Unit
which in turn is mapped to a single FC Sequence. There is a one-to
one mapping between an IP or ARP packet and a FC Sequence
Fibre Channel limits the size of a single Information Unit to 2^32-1,
which is very large [2]. However, since the Maximum
Unit (MTU) size of an IPv4 packet does not exceed 65,536-bytes,
mapped IPv4 size is far below the 2^32-1 limit
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IPv4 Packet definition includes the IP Payload and IP Headers -
fixed and optional. The corresponding FC Sequence Payload
the LLC/SNAP Header and the IPv4 packet
As noted above, the greatest length allowed for an IPv4
including any optional headers and independent of this standard
65,536-bytes. However, limiting the IP MTU size to 65,280-bytes
in buffer resource allocation at N_Ports and also allows for up
256-bytes of overhead. Since the FC Network_Header requires 16-
and the IEEE 802.2 LLC/SNAP header requires 8 bytes, it leaves 232
bytes for future use
All implementations SHALL restrict the IP MTU size to 65,280
and the corresponding FC Sequence Payload size to 65536-bytes
3.2.2 Maximally Minimum IPv4
In order for IP fragmentation and reassembly to work properly it
necessary that every implementation of IP be capable of
a maximally minimum size IP packet without fragmentation. A
minimum size IP Packet is defined as an IP Packet with an 8-
payload (the smallest possible non-zero payload size for a fragment
and a 60-byte header (the largest possible header consisting of
20-byte fixed part and a maximum size option field of 40-bytes) [17].
All implementations SHALL support a FC Data Field of 92-bytes,
is required to support 68-bytes of the maximally minimum sized
Packet, 16-bytes of the FC Network_Header, and 8-bytes of
LLC/SNAP Header
3.2.3 ARP
The ARP packet has a fixed size of 28-bytes. All
SHALL support a FC Data Field size of 52-bytes, which is required
support 28-bytes of an ARP Packet, 16-bytes of the FC Network_Header
and 8-bytes of the LLC/SNAP Header. Note that the minimum
requirement for ARP is already covered by the minimum MTU
for IP but it is mentioned here for completeness
The InARP packet is identical in size to the ARP and the same
requirements apply
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3.2.4 FC Data Field containing FARP
The FARP Command is a FC Extended Link Service (ELS) command and
directly to the FC Data Field without the LLC/SNAP or the
Network_Header. The FARP Command has a fixed size of 76-bytes
Because FARP operates purely in the FC space, it places no
MTU requirements in this specification
3.3 FC Port and Node Network
FC devices are identified by Nodes and their Ports. A Node is
collection of one or more Ports identified by a unique
64-bit World Wide Node name (WW_NN). Each Port in a node,
identified with a unique nonvolatile 64-bit World Wide Port
(WW_PN), and a volatile Port Identifier (Port_ID).
Port_IDs are 24-bits long. A FC frame header carries a Source Port_
(S_ID) and a Destination Port_ID (D_ID). The Port_ID of a given
is volatile. (The mechanism(s) by which a Port_ID may change in a
topology is outside the scope of this document. See Appendix D).
The FC Network_Header is normally optional in FC Standards,
REQUIRED in this specification. A FC Network_Header carries
and destination WW_PNs. A WW_PN consists of a 60-bit Network
and a upper 4-bit Network Address Authority (NAA) field as shown
Fig. 3. The 4-bit NAA field is used to distinguish between
various name registration authorities used to define the
Address [2].
In this specification, both the Source and Destination 4-bit
identifiers SHALL be set to binary '0001' indicating that an
48-bit MAC address is contained in the lower 48 bits of the
address fields. The high order 12 bits in the network address
SHALL be set to 0x0000. The NAA field value equal to binary '0001'
allows FC networks to be bridged with other FC networks
traditional LANs
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+--------+---------------------------------------+
| D_NAA |Network_Dest_Address (High-order bits) |
|(4 bits)| (28 bits) |
+--------+---------------------------------------+
| Network_Dest_Address (Low-order bits) |
| (32 bits) |
+--------+---------------------------------------+
| S_NAA |Network_Source_Address(High-order bits)|
|(4 bits)| (28 bits) |
+--------+---------------------------------------+
| Network_Source_Address (Low-order bit) |
| (32 bits) |
+--------+---------------------------------------+
Fig. 3 Format of the Network_Header
3.4 FC Sequence Payload
FC Payload with IP
An FC Sequence Payload carrying an IP and ARP packet SHALL use
formats shown in Figs. 4 and 5 respectively. Both formats use
8-byte LLC/SNAP header
+-----------------+-----------+------------+-------------//----------+
| LLC/SNAP Header | IP Header | Opt.IP Hdr.| IP Data |
| (8 bytes) | (20 bytes)| (40 bytes | (65280 -IP Header |
| | | Max) | - Opt. IP Hdr.) bytes |
+-----------------+-----------+------------+-------------//----------+
Fig. 4 Format of FC Sequence Payload carrying
FC Sequence Payload with ARP
As noted earlier, FC frames belonging to the same Sequence may
delivered out of order over a Fabric. If the Relative Offset
is used to identify FC Sequence Payload fragments, then the IP
MUST appear in the frame that has a relative offset of 0.
+-----------------+-------------------+
| LLC/SNAP Header | ARP Packet |
| (8 bytes) | (28 bytes) |
+-----------------+-------------------+
Fig. 5 Format of FC Sequence Payload carrying
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FC Sequence Payload with FARP
FARP Protocol commands are directly mapped to the Frame
Payload and are 76-bytes long. No LLC/SNAP Header or
Network_Header is used and therefore the FC Data Field size
consists of the FC Sequence Payload
LLC
A Logical Link Control (LLC) field along with a Sub Network
Protocol (SNAP) field is a method used to identify routed and
non-OSI protocol PDUs and is defined by IEEE 802.2 and applied to
in [8]. In LLC Type 1 operation (i.e., unacknowledged
mode), the LLC header is 3-bytes long and consists of a 1-
Destination Service Access Point (DSAP)field, a 1-byte Source
Access Point (SSAP)field, and a 1-byte Control field as shown in Fig
6.
+----------+----------+----------+
| DSAP | SSAP | CTRL |
| (1 byte) | (1 byte) | (1 byte) |
+----------+----------+----------+
Fig. 6 LLC
The LLC's DSAP and SSAP values of 0xAA indicate that an IEEE 802.2
SNAP header follows. The LLC's CTRL value equal to 0x03 specifies
Unnumbered Information Command PDU. In this specification the
Header value SHALL be set to 0xAA-AA-03. Other values of DSAP/
indicate support for other protocols and SHALL NOT be used in
specification
SNAP
The SNAP Header is 5-bytes long and consists of a 3-
Organizationally Unique Identifier (OUI) field and a 2-byte
Identifier (PID) as shown in Fig. 7
+------+------+-------+------+------+
| OUI | PID |
| ( 3 bytes) | (2 bytes) |
+------+------+-------+------+------+
Fig. 7 SNAP
SNAP was invented to "encapsulate" LAN frames within the payload
The SNAP OUI value equal to 0x00-00-00 specifies that the PID is
EtherType (i.e., routed non-OSI protocol).
The SNAP OUI value equal to 0x00-80-C2 indicates Bridged Protocols
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With the OUI value set to 0x00-00-00, the SNAP PID value equal
0x08-00 indicates IP and a PID value equal to 0x08-06 indicates
(or InARP).
The complete LLC/SNAP Header is shown in Fig. 8.
+-----------+----------+----------+-------+-------+-------+-------+------+
| DSAP | SSAP | CTRL | OUI | PID |
| (1 byte) | (1 byte) | (1 byte) | ( 3 bytes) | (2 bytes |
+-----------+----------+----------+-------+-------+-------+-------+------+
Fig. 8 LLC/SNAP
3.5 Bit and Byte
IP or ARP Packets are mapped to FC-4 Level using the big endian
ordering, which corresponds to the standard network byte order
canonical form [20]. FC-4 Payload maps with no change in order to
FC-2 Level
FC-1 Level defines the method used to encode data prior
transmission and subsequently decode the data upon reception.
method encodes 8-bit bytes into 10-bit transmission characters
improve the transmission characteristics of the serial data stream
In Fibre Channel, data fields are aligned on word boundaries.
Appendix E. A word in FC is defined as 4 bytes or 32 bits.
resulting transmission word after the 8-bit to 10-bit
consists of 40 bits
Data words or Ordered Sets (special FC-2 Level control words)
the FC-2 Level map to the FC-1 Level with no change in order and
bytes in the word are transmitted in the Most Significant Byte
to Least Significant Byte order. The transmission order of
within each byte is the Least Significant Bit to the Most
Bit
4.
4.1 Address
Address Resolution in this specification is primarily concerned
associating IP addresses with FC Port addresses. As
earlier, FC device ports have two types of addresses
- a non-volatile unique 64-bit address called World Wide Port_
(WW_PN
- a volatile 24-bit address called a Port_
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The Address Resolution mechanism therefore will need two levels
mapping
1. A mapping from the IP address to the WW_PN (i.e.,
48-bit MAC address
2. A mapping from the WW_PN to the Port_ID (see Appendix G for
definition of Port_ID
The address resolution problem is compounded by the fact that
Port_ID is volatile and the second mapping MUST be valid before use
Moreover, this validation process can be different depending on
network topology used. Appendix D provides a discussion on
for the different FC topologies
Architecturally, the first level of mapping and control operation
handled by the Address Resolution Protocol (ARP), and the
level by the FC Address Resolution Protocol (FARP). FARP is
in Section 5.
Other optional mechanisms in FARP that directly map an IP address
a Port_ID, or WW_NN to a Port_ID are described in Appendix A
The Inverse Address Resolution Protocol (InARP) is yet
optional mechanism that resolves WW_PN and Port_IDs to IP addresses
InARP is described in Appendix B
4.2 ARP Packet
The Address Resolution Protocol (ARP) given in [9] was designed to
a general purpose protocol, and to work with many
technologies, and with many upper layer protocols. Fig 9 shows
ARP packet format based on [9], where the upper layer protocol uses
4 octet protocol (IP) address and the network technology uses six
octet hardware (MAC) address
The ARP uses two packet types - Request and Reply - and each type
packet is 28 -bytes long in this specification. The ARP Packet
are common to both ARP Requests and ARP Replys
The LLC/SNAP encapsulated ARP Request Packet is mapped to a
Broadcast Sequence and the exact mechanism used to broadcast a
Sequence depends on the FC topology. This is discussed later in
section. Compliant ARP Request Broadcasts SHALL
Network_Headers
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The LLC/SNAP encapsulated ARP Reply Packet is mapped to a
Sequence. Compliant ARP Replys SHALL include Network_Headers
Note that in all discussions to follow, the WW_PN and the 48-bit
address conceptually mean the same thing
The 'HW Type' field SHALL be set to 0x00-01.
Technically, the correct HW Type value should be set to 0x00-06
according to RFC 1700 indicating IEEE 802 networks. However, as
practical matter a HW Type value of 0x00-06 is known to
rejections from some Ethernet end stations when FC is bridged
Ethernet. Translational bridges are normally expected to change
field from Type 6 to 1 and vice versa under these configurations,
many do not. It is because of this reason that the Type Code is
to 1 rather than 6. However, both HW Type values of 0x00-01
0x00-06 SHALL be accepted
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
HW address
The 'Protocol Addr Length' field SHALL be set to 0x04 indicating 4-
bytes of IPv4 address
The 'Operation' Code field SHALL be set as follows
0x00-01 for ARP
0x00-02 for ARP
The 'HW Addr of Sender' field SHALL be the 6-byte IEEE MAC address
the sender. It is either the Requester (ARP Request) or the
(ARP Reply) address
The 'Protocol Addr of Sender' field SHALL be the 4-byte IP address
the Requester (ARP Request) or that of the Responder (ARP Reply).
The 'HW Addr of Target' field SHALL be set to zero during an
Request and to the 6-byte MAC address of the Requester (ARP Request
in an ARP Reply
The 'Protocol Addr of Target' field SHALL be set to the 4-byte
address of the Responder (ARP Reply) in a ARP Request, and to
4-byte IP address of the Requester (ARP Request) in an ARP Reply
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+-------------------------+
| HW Type | 2
+-------------------------+
| Protocol | 2
+-------------------------+
| HW Addr Length | 1
+-------------------------+
| Protocol Addr Length | 1
+-------------------------+
| Op Code | 2
+-------------------------+
| HW Addr of Sender | 6
+-------------------------+
| Protocol Addr of Sender | 4
+-------------------------+
| HW Addr of Target | 6
+-------------------------+
| Protocol Addr of Target | 4
+-------------------------+
Total 28
Fig. 9 ARP Packet
4.3 ARP Layer Mapping and
Whenever a FC port wishes to send IP data to another FC port,
the following steps are taken
1. The source port should first consult its local mapping tables
determine the <destination IP address, destination WW_PN>.
2. If such a mapping is found, then the source sends the
data to the port whose WW_PN address was found in the table
3. If such a mapping is not found, then the source sends
ARP Request broadcast to its connected FC network
anticipation of getting a reply from the correct
along with its WW_PN
4. When an ARP Request Broadcast frame is received by a node
the matching IP address, it generates an ARP Reply. Since
ARP Reply must be addressed to a specific destination Port_ID
the FC layer mapping between the WW_PN and Port_ID (of the
Request orginator) MUST be valid before the reply is sent
5. If no node has the matching IP address, the result is a
behavior
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4.4 ARP Broadcast in a Point-to-Point
The ARP Request (Broadcast) and Reply mechanism described above
apply, although there is only one node that receives the ARP Request
4.5 ARP Broadcast in a Private Loop
In a private loop, the ARP Request Broadcast frame is sent using
broadcast method specified in the FC-AL [7]standard
1. The source port first sends an Open Broadcast
primitive (OPN(fr))Signal forcing all the ports in the
(except itself), to replicate the frames that they
while examining the frame header's Destination_ID field
2. The source port then removes this OPN(fr) signal when
returns to it
3. The loop is now ready to receive the ARP broadcast. The
now sends the ARP Request as a single-frame Broadcast
in a Class 3 frame with the following FC Header D_ID field
F_CTL bits setting
Destination ID : D_ID = 0xFF-FF-
Sequence Initiative : SI=0
Last Sequence : LS=1
End Sequence : ES=1.
4. A compliant ARP Broadcast Sequence frame SHALL include
Network_Header with destination MAC address set to 0xFF-FF-FF
FF-FF-FF and with NAA = b'0001'
5. The destination port recognizing its IP address in the
Request packet SHALL respond with an ARP Reply
4.6 ARP Broadcast in a Public Loop
The following steps will be followed when a port is configured in
public loop
1. A public loop device attached to a fabric through a FL_
MUST NOT use the OPN(fr) signal primitive. Rather, it sends
broadcast sequence to the FL_Port at AL_PA = 0x00.
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2. A FC Fabric propagates the broadcast to all other
including the FL_Port which the broadcast arrived on.
includes all F_Ports, and other FL_Ports
3. On each FL_Port, the fabric propagates the broadcast by
using the primitive signal OPNfr, in order to prepare the
to receive the broadcast sequence
4. A Broadcast Sequence is now sent on all ports (all FL_ports
F_Ports) in Class 3 frame with
Destination ID : D_ID = 0xFF-FF-
Sequence Initiative : SI=0
Last Sequence : LS=1
End Sequence : ES=1.
5. A compliant ARP Broadcast Sequence frame SHALL include
Network_Header with destination MAC address set to 0xFF-FF-FF
FF-FF-FF and with NAA = b'0001'
6. The destination port recognizing its IP address in the
Request packet SHALL respond with an ARP Reply
4.7 ARP Operation in a Fabric
1. Nodes directly attached to fabric do not require the OPN(fr
primitive signal
2. A Broadcast Sequence is now sent on all ports (all FL_ports
F_Ports) in Class 3 frame with
Destination ID : D_ID = 0xFF-FF-
Sequence Initiative : SI=0
Last Sequence : LS=1
End Sequence : ES=1.
3. A compliant ARP Broadcast Sequence frame SHALL include
Network_Header with destination MAC address set
0xFF-FF-FF-FF-FF-FF and with NAA = b'0001'
4. The destination port recognizing its IP address
the ARP packet SHALL respond with an ARP Reply
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5.
5.1
FC Layer Mapping between the WW_PN and the Port_ID is independent
the ARP mechanism and is more closely associated with the details
the FC protocols. Name Server and FC Address Resolution
(FARP) are two formal mechanisms that can be used to create
maintain WW_PN to Port_ID tables
FARP is a method using Extended Link Service (ELS) commands
resolves mappings. The WW_PN to Port_ID
resolution using FARP is especially useful in instances where
Login table entries at a node expire and a Name Server is
available. It is outside the scope of this document to describe
Server. (See [14].)
Additional address matching mechanisms that resolve
and mapping have been added to FARP.
additional mechanisms are optional and described in Appendix A
Direct IP address to Port_ID mapping is useful in applications
there is no visibility of the MAC address
Other less formal FC Layer Mapping mechanisms are described
Appendix C
Since Port_IDs are volatile, all mapped Port_IDs at all times
be valid before use. There are many events that can invalidate
mapping. Appendix D discusses conditions when such a validation
required
5.2 FARP
The FARP protocol uses two ELS commands - FARP-REQ and FARP-REPLY
Note: In the following discussion 'Requester' means the
issuing the FARP-REQ ELS message; 'Responder' means
node replying to the request by sending the FARP-
command
The FARP-REQ ELS Broadcast Request command is used to retrieve
specific node's current Port_ID given its unique WW_PN. This Port_
is sent in a FARP-REPLY unicast command
The FARP-REQ may indicate that the Responder
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- Perform only a Login with it (Requester) or
- Send only a FARP-REPLY or
- Perform a Login and send a FARP-REPLY
No sequence initiative is transferred with the FARP-REQ and
no Reply (ACCEPT or REJECT) follows this command
Since a Sequence Initiative is transferred with the FARP-REPLY
either a ACCEPT or REJECT follows this command as a response
Reception of a FARP-REQ requires a higher level entity at
responding node to send a FARP-REPLY or perform a Port Login
You do not have to be logged in to issue a FARP Request. Also, you
not have to be logged in to the FARP Requester to issue a FARP-REPLY
The FARP Protocol Steps
FARP-REQ (ELS broadcast) Request
(No Reply Sequence
FARP-REPLY (ELS command)
Accept/Reject Reply
The FARP Protocol Format [2] and Size
FT_1, 76-bytes fixed
The FARP Protocol Addressing
- In a FARP-REQ, the S_ID in the FC Header designates
Requester's Port ID. The D_ID in the FC Header is the
identifier 0xFF-FF-FF
- In a FARP-REPLY, the S_ID in the FC Header designates
Responder's Port_ID. The D_ID in the FC Header is the Requester'
Port_ID
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5.3 FARP Command
FARP-REQ and FARP-REPLY commands have identical formats (76-
fixed size) and fields but use different command codes. See
below
+---------------------------------------------------------------------+
| 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 = |
| | | S_ID in FC Header |
+-------------------------------------+---------+---------------------+
| 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; |
| | |See Appendix A |
+-------------------------------------+---------+---------------------+
| WW_PN of Responder | 8 |Supplied by Requester
+-------------------------------------+---------+---------------------+
| WW_NN of Responder | 8 |OPTIONAL; see App. A |
+-------------------------------------+---------+---------------------+
| IP Address of Requester | 16 |OPTIONAL; see App. A |
+-------------------------------------+---------+---------------------+
| IP Address of Responder | 16 |OPTIONAL; see App. A |
+-------------------------------------+---------+---------------------+
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+---------------------------------------------------------------------+
| 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 | Extracted from |
| | | FARP-REQ |
+-------------------------------------+---------+---------------------+
| Responder Flags | 1 | Not Used and |
| | | Unchanged from the |
| | | FARP-REQ |
+-------------------------------------+---------+---------------------+
| Port_ID of Responder | 3 | Supplied by |
| | | Responder = |
| | | S_ID in FC Header |
+-------------------------------------+---------+---------------------+
|WW_PN of Requester | 8 |Supplied by Requester
+-------------------------------------+---------+---------------------+
|WW_NN of Requester | 8 |OPTIONAL; see App. A |
+-------------------------------------+---------+---------------------+
|WW_PN of Responder | 8 |Supplied by Requester
+-------------------------------------+---------+---------------------+
|WW_NN of Responder | 8 |OPTIONAL; see App. A |
+-------------------------------------+---------+---------------------+
|IP Add. of Requester | 16 |OPTIONAL; see App. A |
+-------------------------------------+---------+---------------------+
|IP Address of Responder | 16 |OPTIONAL; see App. A |
+-------------------------------------+---------+---------------------+
Following is a description of the address fields in the
Commands
Port_ID of Requester
It is the 24-bit Port_ID used in the S_ID field of the FC Header of
FARP-REQ. It is supplied by the Requester in a FARP-REQ and
in a FARP-REPLY
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Port_ID of Responder
It is the 24-bit Port_ID used in the S_ID field of the FC Header of
FARP-REPLY. It SHALL be set to 0x00-00-00 in a FARP-REQ. It
supplied by the Responder in a FARP-REPLY
WW_PN
This address field is used with the b'001', b'011', b'101, b'111',
Match Address Code Points. See Match Address Code Point Table below
The Requester supplies the unique 8-byte WW_PN of the Requester
the Responder. It is retained in a FARP-REPLY
WW_NN
The WW_NN address field is used with Match Address Code
b'010', b'011', b'110', and b'111', which are all optional. Its
is fully described in Appendix A. When the WW_NN field is not used
SHALL be either set to '0' or a valid non-zero address
IPv4:
The IPv4 address field is used with the Match Address Code
b'100', b'101', b'110', and b'111', which are all optional. Its
is fully described in Appendix A. When the IP Address field is
used it SHALL be either set to '0' or a valid IP address. A valid
address consists of the 32-bit IPv4 Address with the upper 96
set to '0'.
5.4 Match Address Code
For each receipt of the FARP-REQ Broadcast ELS, the recipients
one or more addresses based on the encoded bits of the "FARP
Address Code Points" field shown in the table below. FARP
with the Match Address Code Point equal to b'001' is described
this section. Other code points are OPTIONAL and are discussed
Appendix A. The upper 5 bits of the Match Address Code Point byte
unused and their use is not currently defined
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+------------------------------------------------------------------+
| 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 | OPTIONAL; see Appendix A |
+-----------+--------------------+---------------------------------+
| 011 | MATCH_WW_PN_NN | OPTIONAL; see Appendix A |
+-----------+--------------------+---------------------------------+
| 100 | MATCH_IPv4 | OPTIONAL; see Appendix A |
+-----------+--------------------+---------------------------------+
| 101 | MATCH_WW_PN_IPv4 | OPTIONAL; see Appendix A |
+-----------+--------------------+---------------------------------+
| 110 | MATCH_WW_NN_IPv4 | OPTIONAL; see Appendix A |
+-----------+--------------------+---------------------------------+
| 111 | MATCH_WW_PN_NN_IPv4| OPTIONAL; see Appendix A |
+-----------+--------------------+---------------------------------+
When a node receives a FARP-REQ with Code Point b'001', it checks
WW_PN against the one set in 'WW_PN of Responder' field of the FARP
REQ command. If there is a match, then the node issues a
according to the action indicated by the FARP Responder Flag.
table below
WW_NN and IPv4 address fields are not used with the b'001' Code
operation. They SHALL be set to '0' or a valid address either by
Requester or the Requester and the Responder
Note that there can be utmost one FARP-REPLY per FARP-REQ
5.5 Responder
The Responder Flags define what Responder action to take if
result of the Match Address Code Points is successful. '
Flags' is an 8-bit field (bits 0-7) and is defined in the
below. This field is used only in a FARP-REQ. This field is
unchanged in a FARP-REPLY. If no bits are set, the Responder
take no action
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+----------+-------------------------------------------------------+
| | FARP Responder Flag |
+----------+----------------+--------------------------------------+
| Bit | Bit Name | Action |
| Position | | |
+----------+----------------+--------------------------------------+
| 0 | INIT_P_LOGI | Initiate a P_LOGI to the Requester |
+----------+----------------+--------------------------------------+
| 1 | INIT_REPLY | Send FARP_REPLY to Requester |
+----------+----------------+--------------------------------------+
| 2 to 7 | Reserved | |
+----------+----------------+--------------------------------------+
If INIT_P_LOGI bit is set then, a Login is performed with the
identified by "Port_ID of Requester" field
If INIT_REPLY is set then, a FARP-REPLY is sent to the
Identified by "Port_ID of Requester" field
If both bits are set at the same time, then both Actions
performed
All other bit patterns are undefined at this time and are
for possible future use
5.6 FARP Support
Responder action - FARP-REPLY and/or Port Login - for a
MATCH_WW_PN is always REQUIRED. If there is no address match then
silent behavior is specified
Support for all other Match Address Code Points is OPTIONAL and
silent behavior from the Responder is valid when it is not supported
Recipients of the FARP-REQ ELS SHALL NOT issue a Service
(LS_RJT) if FARP OPTIONAL mechanisms are not supported
In all cases, if there are no matches, then a silent behavior
specified
If an implementation issues a FARP-REQ with a Match Address
Point that is OPTIONAL, and fails to receive a response, and
implementation has not obtained the Port_ID of the Responder's
by other means (e.g., prior FARP-REQ with other Code Points),
the implementation SHALL reattempt the FARP-REQ with the MATCH_WW_
Code Point
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Getting multiple FARP Replies corresponding to a single FARP-
should normally never occur. It is beyond the scope of this
to specify conditions under which this error may occur or what
corrective action ought to be
6. Exchange
6.1 Exchange
FC Exchanges shall be established to transfer data between ports
Frames on IP exchanges shall not transfer Sequence Initiative.
Appendix E for a discussion on FC Exchanges
6.2 Exchange
With the exception of the recommendations in Appendix F, Section F.1,
"Reliability in Class 3", the mechanism for aging or
exchanges based on activity, timeout, or other method is outside
scope of this document
Exchanges may be terminated by either port. The Exchange
may terminate Exchanges by setting the LS bit, following normal
standard FC-PH [2] rules. This specification prohibits the use of
NOP ELS with LS set for Exchange termination
Exchanges may be torn down by the Exchange Originator or
Responder by using the ABTS_LS protocol. The use of ABTS_LS
terminating aged Exchanges or error recovery is outside the scope
this document
The termination of IP Exchanges by Logout is discouraged, since
may terminate active Exchanges on other FC-4s
7. Summary of Supported
Note: 'Settable' means support is as specified in the
standard; all other key words are as defined earlier in
document
7.1 FC-4
+--------------------------------------------------------------------+
| Feature | Support | Notes |
+--------------------------------------------------------------------+
| Type Code ( = 5) ISO8802-2 LLC/SNAP | REQUIRED | 2 |
| Network_Headers | REQUIRED | 3 |
| Other Optional Headers | MUST NOT | |
+--------------------------------------------------------------------+
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Notes
1. This table applies only to FC-4 related data, such as IP
ARP packets. This table does not apply to link services
other non-FC-4 sequences (PLOGI, for example) that must
for normal operation
2. The TYPE field in the FC Header (Word 2 bits 31-24)
indicate ISO 8802-2 LLC/SNAP Encapsulation (Type 5).
revision of the document focuses solely on the issues
to running IP and ARP over FC. All other issues are
the scope of this document, including full support for
802.2 LLC
3. DF_CTL field (Word 3, bits 23-16 of FC-Header) MUST
the presence of a Network_Header (0010 0000) on the
logical Frame of FC-4 Sequences. It should not indicate
presence of a Network_Header on any subsequent frames of
Sequence
7.2 R_
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 | |
+--------------------------------------------------------------------+
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Notes
1. This is REQUIRED for FC-4 (IP and ARP)
- Routing bits of R_CTL field MUST indicate Device
frames (0000)
- Information Category of R_CTL field MUST
Unsolicited Data (0100)
7.3 F_
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 | |
+--------------------------------------------------------------------+
1. For FC-4 frames, each N_Port shall have a dedicated OX_ID
sending data to each N_Port in the network and a
RX_ID for receiving data from each N_Port as well.
are used in a unidirectional mode, thus setting
Initiative is not valid for FC-4 frames. Sequence Initiative
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
the F_CTL Abort Sequence Condition bits in the first data
of the exchange. For Classes 1 and 2, ACK frame is required
be "continuous sequence".
4. Relative offset prohibited on all other types (
Category) of frames
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7.4
+---------------------------------------------------------------------+
| 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
containing more frames than the available credit indicated by
Sequence recipient at Login. FC-PH [2] end-to-end flow
rules will be followed when transmitting such Sequences
3. a) IP MTU size is 65280-bytes and resulting FC
Payload size is 65536-bytes
b) Maximally Minimum IP Packet size is 68-bytes and
FC Data Field size is 92-bytes
c) ARP (and InARP) Packet size is 28-bytes and resulting
Data Field size is 52-bytes
4. Some OS environments may not handle the max Sequence
size of 65536. It is up to the administrator to configure
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,
where otherwise specified (e.g. Broadcasts are always sent
Class 3).
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8. Review Appendix F, "Reliability in Class 3".
9. The first frame of the first sequence of a new Exchange
have SEQ_CNT = 0 [2].
7.5
+--------------------------------------------------------------------+
| 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
Originator. A Port SHALL be capable of interoperating
another Port that requires X_ID interlock. The
Originator facility within the Port shall use the X_
Interlock protocol in such cases
2. An Exchange Responder is not required to assign RX_IDs. If
RX_ID of FFFF is assigned, it is identifying Exchanges based
S_ID / D_ID / OX_ID only
3. In Classes 1 and 2, a Port shall reject a frame that
create a new Exchange with a P_RJT containing reason
"Unable to establish Exchange". In Class 3, the frame would
dropped
4. When an Exchange is created between 2 Ports for IP/ARP data,
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
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7.6 ARP and
+--------------------------------------------------------------------+
| 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.
from Well-known address FFFFFC are not considered to be
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
configured class of service is used
5. An InARP Request or Reply is a normal Sequence, thus
administrator configured class of service is used
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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
instead. As a Responder, an implementation may need to
to both ADISC and PDISC for compatibility with
specifications
3. Responder Action - FARP-REPLY and/or Port Login - for
successful MATCH_WW_PN is always REQUIRED
Support for all other match Address Codes Points is a
behavior from the Responder is valid when it is not supported
Recipients of the FARP-REQ ELS shall not issue a Service
(LS_RJT) if FARP is not supported
4. If other ELS commands are received an LS_RJT may be sent.
is not required by this specification, and shall not be used
a mechanism to terminate exchanges
5. Required for FL_
7.8 Login
Unless explicitly noted here, a compliant 