IP Storage Working Group Charles Monia
INTERNET DRAFT Rod Mullendore
Expires February 2002 Josh Tseng
<draft-ietf-ips-ifcp-04.txt> Nishan Systems
Franco Travostino
Victor Firoiu
Nortel Networks
David Robinson
Sun Microsystems
Wayland Jeong
Troika Networks
Rory Bolt
Quantum/ATL
Paul Rutherford
ADIC
Mark Edwards
Eurologic
August 2001
iFCP - A Protocol for Internet Fibre Channel Storage Networking
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026 [RFC2026].
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts. Internet-Drafts are draft documents valid for a maximum of
six months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as "work in
progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
Comments
Comments should be sent to the ips mailing list (ips@ece.cmu.edu)
or to the author(s).
Monia, et al. Standards Track [Page 1]
iFCP Revision 4 August 2001
Status of this Memo...................................................1
Comments..............................................................1
1. Abstract.....................................................4
2. About This Document..........................................4
2.1 Conventions used in this document............................4
2.2 Purpose of this document.....................................4
3. iFCP Introduction............................................4
3.1 Definitions..................................................5
4. Fibre Channel Communication Concepts.........................7
4.1 The Fibre Channel Network....................................7
4.2 Fabric Topologies............................................8
4.2.1 Switched Fibre Channel Fabrics..............................9
4.2.2 Mixed Fibre Channel Fabric.................................10
4.3 Fibre Channel Layers and Link Services......................11
4.3.1 Fabric-Supplied Link Services..............................12
4.4 Fibre Channel Devices.......................................12
4.5 Fibre Channel Device Discovery..............................13
4.6 Fibre Channel Information Elements..........................13
4.7 Fibre Channel Frame Format..................................13
4.7.1 N_PORT Address Model.......................................14
4.8 Fibre Channel Transport Services............................15
4.9 Login Processes.............................................15
5. The iFCP Network Model......................................16
5.1 Fabric Topologies Supported by iFCP.........................17
5.2 iFCP Transport Services.....................................18
5.2.1 Fibre Channel Transport Services Supported by iFCP.........18
5.3 The iFCP N_PORT Address Model...............................18
5.3.1 Operation in Address Transparent Mode......................20
5.3.2 Operation in Address Translation Mode......................21
6. iFCP Protocol...............................................25
6.1 Overview....................................................25
6.1.1 iFCP Transport Services....................................25
6.1.2 iFCP Support for Link Services............................26
6.2 TCP Stream Transport of iFCP Frames.........................26
6.2.1 iFCP Session Model.........................................26
6.2.2 iFCP Session Management....................................27
6.2.3 Terminating an N_PORT Login Session........................32
6.3 IANA Considerations.........................................32
6.4 Encapsulation of Fibre Channel Frames.......................33
6.4.1 Encapsulation Header Format................................33
6.4.2 SOF and EOF Delimiter Fields...............................36
6.4.3 Frame Encapsulation........................................37
6.4.4 Frame De-encapsulation.....................................37
7. Fibre Channel Link Services.................................38
7.1 Augmented Link Service Messages.............................38
7.2 Augmented Link Services Requiring Payload Address Translation39
7.3 Augmented Link Services.....................................41
7.3.1 Abort Exchange (ABTX)......................................42
7.3.2 Discover Address (ADISC)...................................42
7.3.3 Discover Address Accept (ADISC ACC)........................43
7.3.4 FC Address Resolution Protocol Reply (FARP-REPLY)..........44
7.3.5 FC Address Resolution Protocol Request (FARP-REQ)..........45
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7.3.6 Logout (LOGO)..............................................46
7.3.7 Port Login (PLOGI).........................................46
7.3.8 Read Exchange Concise......................................47
7.3.9 Read Exchange Concise Accept...............................48
7.3.10 Read Exchange Status Block (RES).........................49
7.3.11 Read Exchange Status Block Accept........................50
7.3.12 Read Link Error Status (RLS).............................51
7.3.13 Read Sequence Status Block (RSS).........................51
7.3.14 Reinstate Recovery Qualifier (RRQ).......................52
7.3.15 Request Sequence Initiative (RSI)........................52
7.3.16 Third Party Process Logout (TPRLO).......................53
7.4 FLOGI Service Parameters Supported by an iFCP Gateway.......55
8. TCP Session Control Messages................................58
8.1 Connection Bind (CBIND).....................................59
8.2 Unbind Connection (UNBIND)..................................62
9. iFCP Error Detection........................................63
9.1 Overview....................................................63
9.2 Stale Frame Prevention......................................63
9.2.1 Enforcing R_A_TOV Limits...................................63
10. Fabric Services Supported by an iFCP implementation.........65
10.1 F_PORT Server...............................................65
10.2 Fabric Controller...........................................65
10.3 Directory/Name Server.......................................66
10.4 iFCP Support for the FC Broadcast Service...................66
11. Security....................................................67
11.1 Overview....................................................67
11.2 Physical Security...........................................67
11.3 Controlling Access..........................................67
11.4 Authentication and Encryption...............................67
11.5 Storage Firewalls...........................................68
12. Quality of Service Considerations...........................68
12.1 Minimal requirements........................................68
12.2 High-assurance..............................................69
13. Author's Addresses..........................................70
A. iFCP Support for Fibre Channel Link Services................72
A.1 Basic Link Services.........................................72
A.2 Link Services Processed Transparently.......................72
A.3 Augmented Link Services.....................................73
B. Implementing IP to FC Connectivity..........................75
B.1 IP Over Fibre Channel.......................................76
B.2 Router Management and Configuration.........................77
C. Performance of The iFCP Session Model.......................78
C.1 Relationship of Throughput to Packet Losses.................78
C.2 Background..................................................79
Full Copyright Statement.............................................81
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1. Abstract
This document specifies an architecture and gateway-to-gateway
protocol for the implementation of Fibre Channel fabric
functionality on a network in which TCP/IP switching and routing
elements replace Fibre Channel components. The protocol enables the
attachment of existing Fibre Channel storage products to an IP
network by supporting the fabric services required by such devices.
2. About This Document
2.1 Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in
this document are to be interpreted as described in RFC-2119
[RFC2119].
All frame formats are in big endian network byte order.
2.2 Purpose of this document
This is a standards-track document, which specifies a protocol for
the implementation of Fibre Channel transport services on a TCP/IP
network. Some portions of this document contain material from
standards controlled by NCITS T10 and T11. This material is
included here for informational purposes only. The authoritative
information is given in the appropriate NCITS standards document.
The authoritative portions of this document specify the protocol
for mapping standards-compliant fibre Channel storage and adapter
implementations to TCP/IP. This mapping includes sections of this
document which describe the "iFCP Protocol" (see section 6).
3. iFCP Introduction
iFCP is a gateway-to-gateway protocol, which provides Fibre Channel
fabric services to Fibre Channel devices over a TCP/IP network.
iFCP uses TCP to provide congestion control, error detection and
recovery. iFCP's primary objective is to allow interconnection and
networking of existing Fibre Channel devices at wire speeds over an
IP network.
The protocol and method of frame address translation described in
this document permit the attachment of Fibre Channel storage
devices to an IP-based fabric by means of transparent gateways.
The protocol achieves this transparency through a process that
allows normal Fibre Channel frame traffic to pass through the
gateway directly, with provisions, where necessary, for
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intercepting and emulating the fabric services required by a Fibre
Channel device.
3.1 Definitions
Terms needed to clarify the concepts presented in this document are
presented here.
Locally Attached Device - With respect to a gateway, a Fibre
Channel device accessed through the Fibre Channel fabric to
which the gateway is attached.
Remotely Attached Device - With respect to a gateway, a Fibre
Channel device accessed from the gateway by means of the
iFCP protocol.
Address-translation mode û A mode of gateway operation in which the
scope of N_PORT fabric addresses for locally attached
devices are local to the iFCP gateway.
Address-transparent mode û A mode of gateway operation in which the
scope of N_PORT fabric addresses for all Fibre Channel
devices are unique to the logical fabric to which the
gateway belongs.
Gateway Region û The portion of the iFCP storage network accessed
through an iFCP gateway. Fibre Channel devices in the
region consist of all Fibre Channel devices locally
attached to the gateway.
Logical Fabric û The union of two or more gateway regions
configured to interoperate together in address-transparent
mode.
Fibre Channel Device - A device attached to a Fibre Channel fabric
by means of the N_PORT interface described in [FC-FS].
Fibre Channel Network - A native Fibre Channel fabric and all
attached Fibre Channel devices.
Fabric - The components of a Fibre Channel network that provides
the transport services defined in [FC-FS]. A fabric may be
implemented in the IP framework by means of the
architecture and protocols discussed in this document.
Fabric Port - The interface through which an N_PORT accesses a
Fibre Channel fabric. The type of fabric port depends on
the Fibre Channel fabric topology. In this specification,
all fabric port interfaces are considered to be
functionally equivalent.
FC-2 - The Fibre Channel transport services layer described in [FC-
FS].
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iFCP Portal - An IP-addressable entity representing the point at
which a logical or physical iFCP device is attached to the
IP network.
N_PORT - An iFCP or Fibre Channel entity representing the interface
to Fibre Channel device functionality. This interface
implements the Fibre Channel N_PORT semantics specified in
[FC-FS]. Fibre Channel defines several variants of this
interface that are dependant on the Fibre Channel fabric
topology. As used in this document, the term applies
equally to all variants.
N_PORT fabric address - The address of an N_PORT within the Fibre
Channel fabric.
N_PORT ID -- The address of a locally attached N_PORT within a
gateway region. N_PORT I/Ds are assigned in accordance
with the Fibre Channel rules for address assignment
specified in [FC-FS].
N_PORT Alias -- The N_PORT address assigned by a gateway to
represent a remote N_PORT accessed via the iFCP network.
When routing frame traffic in address translation mode, the
gateway automatically converts N_PORT aliases to N_PORT
network addresses and vice versa.
N_PORT Network Address - The address of an N_PORT in the IP fabric.
This address consists of the IP address of the iFCP Portal
and the N_PORT ID of the locally attached Fibre Channel
device.
F_PORT - The interface used by an N_PORT to access Fibre Channel
switched fabric functionality.
iFCP - The protocol discussed in this document.
Logical iFCP Device - The abstraction representing a single Fibre
Channel device as it appears on an iFCP network.
iSNS - The IP protocol by which storage name services are
implemented in an iFCP network. Fibre Channel Name services
are provided by an iSNS name server as described in [ISNS].
N_PORT Session - An association created when two N_PORTS have
executed a PLOGI operation. It is comprised of the N_PORTs
and TCP connection that carries traffic between them.
iFCP Frame - A Fibre Channel frame encapsulated in accordance with
the Common Encapsulation Specification [ENCAP] and this
specification.
Port Login (PLOGI) - The Fibre Channel Extended Link Service (ELS)
that establishes an N_PORT login session through the
Monia et-al. Standards Track [Page 6]
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exchange of identification and operation parameters between
an originating N_PORT and a responding N_PORT.
DOMAIN_ID û The value contained in the high-order byte of a 24-bit
N_PORT Fibre Channel address.
4. Fibre Channel Communication Concepts
Fibre Channel is a frame-based, serial technology designed for
peer-to-peer communication between devices at gigabit speeds and
with low overhead and latency.
This section contains a discussion of the Fibre Channel concepts
that form the basis for the iFCP network architecture and protocol
described in this document. Readers familiar with this material may
skip to section 5.
Material presented in this section is drawn from the following T11
specifications:
-- The Fibre Channel Framing and Signaling Interface, [FC-FS]
-- Fibre Channel Switch Fabric -2, [FC-SW2]
-- Fibre Channel Generic Services, [FC-GS3]
-- Fibre Channel Fabric Loop Attachment, [FC-FLA]
The reader will find an in-depth treatment of the technology in
[Kembel].
4.1 The Fibre Channel Network
The fundamental entity in Fibre Channel is the Fibre Channel
network. Unlike a layered network architecture, a Fibre Channel
network is largely specified by functional elements and the
interfaces between them. As shown in Figure 1, these consist, in
part, of the following:
a) N_PORTs -- The end points for Fibre Channel traffic. In the FC
standards, N_PORT interfaces have several variants, depending on
the topology of the fabric to which they are attached. As used
in this specification, the term applies to any one of the
variants.
b) FC Devices û The Fibre Channel devices to which the N_PORTs
provide access.
c) Fabric Ports -û The interface within a fabric that provides Fibre
Channel attachment for an N_PORT. The types of fabric port
depend on the fabric topology and are discussed in section 4.2.
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d) The fabric infrastructure for carrying frame traffic between
N_PORTs.
e) Within a switched or mixed fabric (see section 4.2), a set of
auxiliary servers, including a name server for device discovery
and network address resolution. The types of service depend on
the network topology.
+--------+ +--------+ +--------+ +--------+
| FC | | FC | | FC | | FC |
| Device | | Device |<-------->| Device | | Device |
|........| |........| |........| |........|
| N_PORT | | N_PORT | | N_PORT | | N_PORT |
+---+----+ +----+---+ +----+---+ +----+---+
| | | |
+---+----+ +----+---+ +----+---+ +----+---+
| Fabric | | Fabric | | Fabric | | Fabric |
| Port | | Port | | Port | | Port |
+========+===+========+==========+========+==+========+====
| Fabric |
| & |
| Fabric Services |
+-----------------------------------------------------+
Figure 1 -- A Fibre Channel Network
The following sections describe Fibre Channel fabric topologies and
give an overview of the Fibre Channel communications model.
4.2 Fabric Topologies
The principal Fibre Channel fabric topologies consist of the
following:
a) Arbitrated Loop -- A series of N_PORTs connected together in
daisy-chain fashion. Data transmission between N_PORTs
requires arbitration for control of the loop in a manner
similar to a token ring network.
b) Switched Fabric -- A fabric consisting of switching elements,
as described in section 4.2.1.
c) Mixed Fabric -- A fabric consisting of switches and "fabric-
attached" loops. A description can be found in [FC-FLA].
Depending on the topology, the N_PORT and fabric port variants
through which a Fibre Channel device is attached to the network may
be one of the following:
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Fabric Topology Fabric Port Type N_PORT Variant
--------------- ---------------- --------------
Loop L_PORT NL_PORT
Switched F_PORT N_PORT
Mixed FL_PORT NL_PORT
F_PORT N_PORT
The differences in each N_PORT variant and its corresponding fabric
port are confined to the interactions between them. To an external
N_PORT, all fabric ports are transparent and all remote N_PORTs are
functionally identical.
4.2.1 Switched Fibre Channel Fabrics
An example of a multi-switch Fibre Channel fabric is shown below.
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+----------+ +----------+
| FC | | FC |
| Device | | Device |
|..........| |..........|
| N_PORT |<........>| N_PORT |
+----+-----+ +-----+----+
| |
+----+-----+ +-----+----+
| F_PORT | | F_PORT |
==========+==========+==========+==========+==============
| FC | | FC |
| Switch | | Switch |
+----------+ +----------+ Fibre Channel
|Inter- | |Inter- | Fabric
|Switch | |Switch |
|Interface | |Interface |
+-----+----+ +-----+----+
| |
| |
+-----+----+----------+-----+----+
|Inter- | |Inter- |
|Switch | |Switch |
|Interface | |Interface |
+----------+ +----------+
| FC Switch |
| |
+--------------------------------+
Figure 2 -- Multi-Switch Fibre Channel Fabric
The interface between switch elements is either proprietary or the
standards-compliant E_PORT interface described by the FC-SW2
specification, [FC-SW2].
4.2.2 Mixed Fibre Channel Fabric
A mixed fabric contains one or more arbitrated loops connected to a
switched fabric as shown in Figure 3.
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+----------+ +----------+ +---------+
| FC | | FC | | FC |
| Device | | Device | | Device |
|..........| |..........| |.........|
| N_PORT |<........>| NL_PORT +---+ NL_PORT |
+----+-----+ +-----+----+ +----+----+
| | FC Loop |
+----+-----+ +-----+----+ |
| F_PORT | | FL_PORT +--------+
| | | |
==========+==========+==========+==========+==============
| FC | | FC |
| Switch | | Switch |
+----------+ +----------+
|Inter- | |Inter- |
|Switch | |Switch |
|Interface | |Interface |
+-----+----+ +-----+----+
| |
| |
+-----+----+----------+-----+----+
|Inter- | |Inter- |
|Switch | |Switch |
|Interface | |Interface |
+----------+ +----------+
| FC Switch |
| |
+--------------------------------+
Figure 3 -- Mixed Fibre Channel Fabric
As noted previously, the protocol for communications between peer
N_PORTs is independent of the fabric topology, N_PORT variant and
type of fabric port to which an N_PORT is attached.
4.3 Fibre Channel Layers and Link Services
Fibre channel consists of the following layers:
FC0 -- The interface to the physical media,
FC1 û- The encoding and decoding of data and out-of-band physical
link control information for transmission over the physical media,
FC2 û- The transfer of frames, sequences and Exchanges comprising
protocol information units.
FC3 û- Common Services,
FC4 û- Application protocols, such as FCP, the Fibre Channel SCSI
protocol.
In addition to the layers defined above, Fibre Channel defines a
set of auxiliary operations, some of which are implemented within
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the transport layer fabric, called link services. These are
required to manage the Fibre Channel environment, establish
communications with other devices, retrieve error information,
perform error recovery and other similar services. Some link
services are executed by the N_PORT. Others are implemented
internally within the fabric. These internal services are
described in the next section.
4.3.1 Fabric-Supplied Link Services
Servers internal to a switched fabric handle certain classes of
Link Service requests. The servers appear as N_PORTs located at
well-known N_PORT fabric addresses. Service requests use the
standard Fibre Channel mechanisms for N_PORT-to-N_PORT
communications.
All switched fabrics must provide the following services:
Fabric F_PORT server û Services an N_PORT request to access the
fabric for communications.
Fabric Controller -- Provides state change information to inform
other FC devices when an N_PORT exits or enters the fabric (see
section 4.5).
Directory/Name Server û Allows N_PORTs to register information
in a database, retrieve information about other N_PORTs and
discover other devices as described in section 4.5.
A switched fabric may also implement the following optional
services:
Broadcast Address/Server û- Transmits single-frame, class 3
sequences to all N_PORTs.
Time Server û- Intended for the management of fabric-wide
expiration timers or elapsed time values and is not intended for
precise time synchronization.
Management Server û Collects and reports management information,
such as link usage, error statistics, link quality and similar
items.
Quality of Service Facilitator û Performs fabric-wide bandwidth
and latency management.
4.4 Fibre Channel Devices
A Fibre Channel device has one or more fabric-attached N_PORTs. The
device and its N_PORTs have the following associated identifiers:
a) A world-wide unique identifier for the device,
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b) A world-wide unique identifier for each N_PORT attached to the
device,
c) For each N_PORT attached to a fabric, a 24-bit fabric-unique
address having the properties defined in section 4.7.1. The
fabric address is the address to which frames are sent.
Each world-wide unique identifier is a 64-bit binary quantity
having the format defined in [FC-FS].
4.5 Fibre Channel Device Discovery
In a switched or mixed fabric, fibre channel devices and changes in
the device configuration may be discovered by means of services
provided by the Fibre Channel Name Server and Fabric Controller.
The Name Server provides registration and query services that allow
a Fibre Channel device to register its presence on the fabric and
discover the existence of other devices. For example, one type of
query obtains the fabric address of an N_PORT from its 64-bit
world-wide unique name. The full set of supported Fibre Channel
Name Server queries is specified in [FC-GS3].
The Fabric Controller complements the static discovery capabilities
provided by the Name Server through a service that dynamically
alerts a Fibre Channel device whenever an N_PORT is added or
removed from the configuration. A Fibre Channel device receives
these notifications by subscribing to the service as specified in
[FC-FS].
4.6 Fibre Channel Information Elements
The fundamental element of information in Fibre Channel is the
frame. A frame consists of a fixed header and up to 2112 bytes of
payload having the structure described in section 4.7. The maximum
frame size that may be transmitted between a pair of Fibre Channel
devices is negotiable up to the payload limit, based on the size of
the frame buffers in each Fibre Channel device and the path MTU
supported by the fabric.
Operations involving the transfer of information between N_PORT
pairs are performed through 'Exchanges'. In an Exchange,
information is transferred in one or more ordered series of frames
referred to as Sequences.
Within this framework, an upper layer protocol is defined in terms
of transactions carried by Exchanges. Each transaction, in turn,
consists of protocol information units, each of which is carried by
an individual Sequence within an Exchange.
4.7 Fibre Channel Frame Format
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A Fibre Channel frame consists of a header, payload and 32-bit CRC
bracketed by SOF and EOF delimiters. The header contains the
control information necessary to route frames between N_PORTs and
manage Exchanges and Sequences. The following diagram gives a
highly simplified view of the frame.
+-----------------------------+
| Start-of-frame Delimiter |
+-----+-----------------------+<----+
| | Destination N_PORT | |
| | Fabric Address (D_ID) | |
| | (24-bits) | |
+-----+-----------------------+ 24-byte
| | Source N_PORT | Frame
| | Fabric Address (S_ID) | Header
| | (24 bits) | |
+-----+-----------------------+ |
| Control information for | |
| frame type, Exchange | |
| management, IU | |
| segmentation and | |
| re-assembly | |
+-----------------------------+<----+
| |
| Frame payload |
| (0 û 2112 bytes) |
| |
| |
| |
+-----------------------------+
| CRC |
+-----------------------------+
| End-of-Frame Delimiter |
+-----------------------------+
Figure 4 -- Fibre Channel Frame Format
The source and destination N_PORT fabric addresses embedded in the
S_ID and D_ID fields represent the physical MAC addresses of
originating and receiving N_PORTs.
4.7.1 N_PORT Address Model
N_PORT fabric addresses are 24-bit values having the following
format defined by the Fibre Channel specification [FC-FS]:
Bit 23 16 15 8 7 0
+-----------+------------+----------+
| Domain ID | Area ID | Port ID |
+-----------+------------+----------+
Figure 5 -- Fibre Channel Address Format
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A Fibre Channel device acquires an address when it is attached to
the fabric. Such addresses are volatile and subject to change based
on modifications in the fabric configuration.
In a Fibre Channel fabric, each switch element has a unique Domain
I/D assigned by the principal switch. The value of the Domain I/D
ranges from 1 to 239 (0xEF). Each switch element, in turn,
administers a block of addresses divided into area and port IDs.
N_PORTs logging into the fabric receive a unique fabric address
consisting of the switchÆs Domain I/D concatenated with switch-
assigned area and port I/Ds.
4.8 Fibre Channel Transport Services
The Fibre Channel standard ([FC-FS]) defines the following classes
of service provided by a fabric implementation:
Class 1 û A dedicated physical circuit connecting two N_PORTs.
Class 2 û A frame-multiplexed connection with end-to-end flow
control and delivery confirmation.
Class 3 û A frame-multiplexed connection with no provisions for
end-to-end flow control or delivery confirmation.
Class 3 service is similar to UDP or IP datagram service. Fibre
channel storage devices using this class of service rely on the ULP
implementation to detect and recover from transient device and
transport errors.
In addition to the above services, fabrics may implement additional
quality of service policies.
For service classes other than class 1, the Fibre Channel fabric is
not required to provide in-order delivery of frames unless
explicitly requested by the frame originator (and supported by the
fabric). If ordered delivery is not in effect, it is the
responsibility of the frame recipient to reconstruct the order in
which frames were sent based on sequence information in the frame
header.
4.9 Login Processes
The Login processes are the means whereby an N_PORT establishes the
operating environment necessary to communicate with the fabric and
other N_PORTs. Fabric login (FLOGI) and destination N_PORT login
(PLOGI) are performed through procedures by which an N_PORT
exchanges operating parameters with the fabric or another N_PORT.
Since N_PORT addresses are volatile, an N_PORT login (PLOGI)
operation is almost always preceded by a Name Server query to
discover the Fibre Channel address of the remote device. A common
query type involves use of the world-wide unique name of an N_PORT
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to obtain the 24-bit N_PORT Fibre Channel address to which the
PLOGI request is sent.
5. The iFCP Network Model
The purpose of the iFCP protocol is to enable the implementation of
Fibre Channel mixed or switched fabric functionality on an IP
network in which IP components and technology replace the Fibre
Channel switching and routing infrastructure described in section
4.2.
The following diagram shows a Fibre Channel fabric with attached
devices. These are connected to the fabric through an N_PORT
interface attached to a Fabric Port whose behavior is specified in
[FC-FS]. In this case, the N_PORT and Fabric Port represent any of
the variants described in section 4.2.
Within the Fibre Channel device domain, fabric-addressable entities
consist of other N_PORTs and devices internal to the fabric that
perform the fabric services defined in [FC-GS3].
Fibre Channel Network
+--------+ +--------+
| FC | | FC |
| Device | | Device |
|........| |........| Fibre Channel
| N_PORT |<......>| N_PORT | Device Domain
+---+----+ +----+---+ ^
| | |
+---+----+ +----+---+ |
| Fabric | | Fabric | |
| Port | | Port | |
==========+========+========+========+==============
| Fabric & | |
| Fabric Services | v
| | Fibre Channel
+--------------------------+ Fabric Domain
Figure 6 -- A Fibre Channel Fabric
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Gateway Region Gateway Region
+--------+ +--------+ +--------+ +--------+
| FC | | FC | | FC | | FC |
| Device | | Device | Fibre | Device | | Device | Fibre
|........| |........| Channel |........| |........| Channel
| N_PORT | | N_PORT |<.........>| N_PORT | | N_PORT | Device
+---+----+ +---+----+ Traffic +----+---+ +----+---+ Domain
| | | | ^
+---+----+ +---+----+ +----+---+ +----+---+ |
| Fabric | | Fabric | | Fabric | | Fabric | |
| Port | | Port | | Port | | Port | |
=+========+==+========+===========+========+==+========+==========
| iFCP Layer |<--------->| iFCP Layer | |
|....................| ^ |....................| |
| iFCP Portal | | | iFCP Portal | v
+--------+-----------+ | +----------+---------+ IP
iFCP|Gateway Control iFCP|Gateway Fabric
| Data |
| |
| |
|<------Encapsulated Frames------->|
| +------------------+ |
| | | |
+------+ IP Network +--------+
| |
+------------------+
Figure 7 -- An iFCP Network with iFCP Gateways
The above diagram shows one implementation of an equivalent iFCP
fabric. Two gateway regions are shown. Each consists of Fibre
Channel devices directly connected to the iFCP fabric through
fabric ports implemented as part of the edge switch or gateway.
Looking into the fabric port on the Fibre Channel side of the
gateway, the network appears as a Fibre Channel fabric. Here, the
gateway presents remote N_PORTs as fabric-attached devices.
Conversely, on the IP network side, the gateway presents each
locally connected N_PORT as a logical Fibre Channel device.
5.1 Fabric Topologies Supported by iFCP
A property of this gateway architecture is that the fabric
configuration and topology within the gateway region are opaque to
the IP network and other gateway regions. That is, the topology in
the gateway region, whether it is loop- or switch-based, is hidden
from the IP network and from other gateway regions. As a result,
support for specific FC fabric topologies becomes a gateway
implementation issue. In such cases, the gateway incorporates
whatever functionality is required to present locally attached
N_PORTs as logical iFCP devices.
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Regarding fabric topologies, the examples in this specification
show an N_PORT directly connected to a gateway fabric port, this is
done to keep the illustrations simple and does not reflect any
fundamental limitation in the fabric configuration that an
implementation can support.
5.2 iFCP Transport Services
N_PORT to N_PORT communications that traverse a TCP/IP network
require the intervention of the iFCP layer within the gateway. This
consists of the following operations:
a) Execution of the frame addressing and mapping functions
described in section 5.3.
b) Execution of fabric-supplied link services addressed to one of
the well-known Fibre Channel N_PORT addresses.
c) Encapsulation of Fibre Channel frames for injection into the
TCP/IP network and de-encapsulation of Fibre Channel frames
received from the TCP/IP network.
d) Establishment of an N_PORT login session in response to a PLOGI
directed to a remote device.
The following sections discuss the frame addressing mechanism and
the way in which it is used to achieve communications transparency
between N_PORTs.
5.2.1 Fibre Channel Transport Services Supported by iFCP
An iFCP fabric supports Class 2 and Class 3 Fibre Channel transport
services as specified in [FC-FS]. An iFCP fabric does not support
Class 1 (dedicated connection).
5.3 The iFCP N_PORT Address Model
This section discusses the role of the N_PORT addressing model of
section 4.7.1 in the routing of frames between locally and remotely
attached N_PORTs.
In the case of a remote N_PORT, where the frame traffic must
traverse the IP network, the gateway must perform this routing
transparently with respect to the locally attached N_PORT.
To provide such transparency, the gateway maintains an association
between the Fibre Channel address of a remote N_PORT, as seen by a
locally attached device, and the corresponding address of the
remote device on the IP network. To establish this association the
iFCP gateway assigns and manages Fibre Channel N_PORT fabric
addresses as described in the following paragraphs.
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In an iFCP storage fabric, the iFCP gateway performs the address
assignment and frame routing functions of an FC switch element.
Unlike an FC switch, however, an iFCP gateway must also route
frames to external devices attached to remote gateways on the IP
network.
In order to be transparent to FC devices, the gateway must route
such frames using only the embedded 24-bit address. By exploiting
its control of address allocation and access to frame traffic
entering or leaving the gateway region, it is able to achieve the
necessary transparency.
The gateway may allocate device addresses in one of two ways:
a) Address Translation Mode û A mode of address assignment in which
the gateway allocates an N_PORT device address that is unique to
the gateway region. The address of a remote device is
represented in that gateway region by a gateway assigned N_PORT
alias.
b) Address Transparent Mode û A mode of address assignment in which
the gateway allocates an N_PORT address that is unique across
the set of gateway regions comprising a logical fabric.
In address transparent mode, gateways within a logical fabric
cooperate in the assignment of addresses to locally attached
N_PORTs. Each gateway in control of a region is responsible for
obtaining and distributing unique domain I/Ds from the address
assignment authority as described in section 5.3.1.1. Consequently,
within the scope of the logical fabric, the address of each N_PORT
is unique. For that reason, gateway-assigned aliases are not
required to represent remote N_PORTs.
All iFCP implementations MUST support operation in address
translation mode. Support for address transparent mode is optional.
The mode of gateway operation is settable in an implementation-
specific manner. The implementation MUST NOT allow the mode to be
changed after iFCP sessions have been established.
The choice of addressing mode involves the tradeoffs between
scalability and transparency discussed below.
The scalability constraints in address transparent mode are a
consequence of the Fibre Channel address allocation policy
described in section 4.7.1. As noted, an IP fabric using this
address allocation scheme is limited to a combined total of 239
gateways and Fibre Channel switch elements. As the system expands,
an IP fabric may consist of many switch elements distributed
throughout the enterprise, each of which controls a small number of
devices. In this case, the limitation in switch count may become a
barrier to extending and fully integrating the storage network.
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Address Translation mode avoids this limitation by decoupling
N_PORT fabric addresses from the constraints of fabric-wide address
space management. Consequently, a virtually unlimited number of
iFCP gateways, Fibre Channel devices and switch elements may be
internetworked. This mode of address allocation also simplifies
management of the IP storage fabric configuration by eliminating
the need for a centralized address-assignment authority.
A consequence of address translation mode is that the 24-bit N_PORT
address is no longer unique across the storage network. As a
result, when processing frame traffic to or from remote N_PORTs,
the gateway must intervene to translate the 24-bit N_PORT addresses
between the sending and receiving gateway regions. These address
operations involve:
a) Translating the N_PORT I/Ds in the frame header and
b) Translating N_PORT I/Ds carried in the payload of certain
extended link service messages.
The process of N_PORT I/D translation for the frame header is
described in section 5.3.2. The processing for link services with
frame addresses in the payload is described in section 7.1.
The details of the address transparent and address translation
operational modes are discussed in the following sections.
5.3.1 Operation in Address Transparent Mode
In addition to the scalability limits discussed above, the
following considerations and requirements apply to this mode of
operation:
a) There is increased dependency on the services of a central
address assignment authority, such as iSNS. If connectivity with
the server is lost, new DOMAIN_ID values cannot be automatically
allocated as gateways and Fibre Channel switch elements are
added to the logical fabric. As a result, new gateways and
switch elements cannot be automatically added to the ip fabric.
Of course, it is always possible to add and manage such
additional components manually.
b) Coordination of iSNS servers is required. Multiple iFCP gateways
set up with independently-administered address servers must be
completely torn down and slaved under a single iSNS name server
before they can be configured into the same logical fabric. In
contrast, operation in address translation mode requires only
that the independent iSNS servers import client attributes from
other iSNS servers, before clients under different iSNS
authorities can be made to interoperate.
c) iFCP gateways in transparent mode will not interoperate with
iFCP gateways that are not in transparent mode.
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d) When interoperating with locally attached Fibre Channel fabrics,
the iFCP gateway MUST assume control of DOMAIN_ID assignments in
accordance with the appropriate Fibre Channel standard or
specification. As described in section 5.3.1.1, DOMAIN_ID
values assigned to FC switches in attached fabrics must be
issued by the iSNS server or manually assigned.
e) When operating in address transparent Mode, no Fibre Channel
address translation SHALL take place, and no link service
Messages shall be augmented with additional information by the
iFCP layer.
The process for establishing the TCP/IP context associated with an
N_PORT login session in this mode is similar to that specified for
address translation mode (section 5.3.2).
5.3.1.1 Transparent Mode Domain I/D Management
As described above, each gateway and Fibre Channel switch in a
logical fabric must have a unique domain I/D. In a gateway region
containing Fibre Channel switch elements, each element obtains a
domain I/D by querying the principal switch as described in [FC-
SW2] -- in this case the iFCP gateway itself. The gateway in turn
may obtain domain I/Ds on demand from a central address allocation
authority, such as an iSNS name server or manually from a pre-
assigned block of IDs. In that sense, the address authority (e.g.,
iSNS) assumes the role of master switch for the logical fabric.
5.3.1.2 Incompatibility with Address Translation Mode
iFCP gateways in address transparent mode shall not originate or
accept frames that do not have the TRN bit set to one in the iFCP
flags field of the encapsulation header (see section 6.4.1). The
iFCP gateway shall immediately terminate any N_PORT sessions with
the iFCP gateway from which it receives such frames.
5.3.2 Operation in Address Translation Mode
This section summarizes the process for managing the assignment of
addresses within a gateway region, including the modification of FC
frame addresses embedded in the frame header for frames sent and
received from remotely attached N_PORTs.
As described above, the scope of N_PORT addresses in this mode is
local to the gateway region. A principal switch within the gateway
region, possibly the iFCP gateway itself, oversees the assignment
of such addresses in accordance with the rules specified in [FC-
SW2] and [FC-FLA].
The assignment of N_PORT addresses to locally attached devices is
controlled by the switch element to which the device is connected.
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When a remotely attached N_PORT is accessed, the gateway assigns a
locally significant N_PORT alias. This alias is used in place of
the N_PORT I/D assigned by the remote gateway. To perform address
conversion and enable the appropriate routing, the gateway
maintains a table mapping N_PORT aliases to the appropriate TCP/IP
connection context and N_PORT ID of all remotely accessed N_PORTs.
The means by which translation table entries are created and
updated are described in section 5.3.2.1.
5.3.2.1 Translation Table Maintenance
This section discusses the mechanisms for creating and maintaining
the translation tables used by a gateway operating in address
translation mode. For purposes of illustration, Figure 8 shows an
example of how a translation table entry might be formatted.
+--------------------------------+
| IP Address of Remote Gateway |
+--------------------------------+
| N_PORT I/D |
+--------------------------------+
| N_PORT Alias |
+--------------------------------+
| N_PORT World-wide Unique Name |
+--------------------------------+
Figure 8 -- Address Translation Table Entry for Remote Device
Each entry contains the following information:
IP Address of Remote Gateway -- IP address of the gateway to
which the remote device is attached.
N_PORT I/D -- N_PORT address assigned to the remote device by
the remote iFCP gateway.
N_PORT Alias -- N_PORT address assigned to the remote device by
the 'local' iFCP gateway.
N_PORT World-wide Unique Name -- 64-bit N_PORT world wide name
as specified in [FC-FS].
In addition to the table itself, the iFCP gateway is assumed to
have some way of performing rapid table lookups when translating
addresses for frame traffic as described in section 5.3.2.2.
Translation table entries may be built in response to the following
Fibre Channel transactions:
a) Name Server requests issued by locally-attached N_PORTs as part
of Fibre Channel device discovery (see section 4.5) or,
b) N_PORT PLOGI requests received from remote Fibre Channel devices
(see section 7.3.7).
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An iFCP gateway converts a Fibre Channel Name Server request to an
iSNS server query. Information returned in response to the query
includes the IP address, N_PORT ID and N_PORT world wide unique
name for the remote device. After building the table entry
containing this information, the iFCP layer creates and adds the
24-bit N_PORT alias that is returned to the local N_PORT as the
Fibre Channel address of the remotely attached device.
The information in a PLOGI frame received from a remote device can
also be used to construct a translation table entry. As described
in section 7.3.7, the device's N_PORT world-wide unique name is
obtained from the request payload. The IP address is available
from the TCP/IP connection context and the N_PORT I/D is contained
in the S_ID field of the PLOGI frame header. The N_PORT alias may
then be assigned and used in address translation as specified in
section 5.3.2.
5.3.2.1.1 Updating a Translation Table Entry
A translation table entry may become stale as the result of any
event that invalidates or triggers a change in the fabric-assigned
N_PORT network address, such as a fabric reconfiguration or the
replacement of the device. As a consequence of the event causing
the reconfiguration, frames directed to the N_PORT as the result of
a stale translation table entry will be rejected or discarded by
the receiver.
Once the originating N_PORT learns of the reconfiguration, usually
through the Fibre Channel state change notification mechanism, the
normal name server lookup and PLOGI mechanisms needed to
reestablish the N_PORT login session will automatically purge the
translation table of such stale entries.
5.3.2.2 Frame Address Translation
For outbound frames, the table of external N_PORT network addresses
are referenced to map the Destination N_PORT alias and Source
N_PORT ID to the TCP connection context and the N_PORT ID assigned
by the remote gateway. The translation process for outbound frames
is shown below.
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Raw Fibre Channel Frame
+--------+-----------------------------------+ +--------------+
| | Destination N_PORT Alias |--->| Lookup TCP |
+--------+-----------------------------------+ | connection |
| | Source N_PORT ID | | context |
+--------------------------------------------+ | and N_PORT ID|
| | +------+-------+
| Control information, | | TCP
| Payload and FC CRC | | conn
| | | context
+--------------------------------------------+ | &
| N_PORT
| ID
|
After Address Translation and Encapsulation |
+--------------------------------------------+ |
| FC Encapsulation Header | |
+--------------------------------------------+ |
| SOF Delimiter Word | |
+============================================+ |
| | Destination N_PORT ID |<----------+
+--------+-----------------------------------+
| | Source N_PORT ID |
+--------+-----------------------------------+
| |
| Control information, Payload |
| and FC CRC |
+============================================+
| EOF Delimiter Word |
+--------------------------------------------+
Figure 9 -- Outbound Frame Address Translation
For inbound frames, a translation table lookup is performed to
regenerate the N_PORT alias from the TCP connection context and
N_PORT ID contained in the encapsulated FC frame. The translation
process for inbound frames is shown below.
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Network Format of Inbound Frame
+--------------------------------------------+ TCP
| FC Encapsulation Header | Connection
+--------------------------------------------+ Context
| SOF Delimiter Word | |
+============================================+ V
| | Destination N_PORT ID | +---+----+
+--------+-----------------------------------+ | Lookup |
| | Source N_PORT ID |---->| Source |
+--------+-----------------------------------+ | N_PORT |
| | | Alias |
| Control information, Payload | +----+---+
| and FC CRC | | Source
+============================================+ | N_PORT
| EOF Delimiter Word | | Alias
+--------------------------------------------+ |
|
|
Frame after Address Translation and De-encapsulation |
+--------+-----------------------------------+ |
| | Destination N_PORT ID | |
+--------+-----------------------------------+ |
| | Source N_PORT Alias |<---------+
+--------+-----------------------------------+
| |
| Control information, Payload, |
| and FC CRC |
+--------------------------------------------+
Figure 10 -- Inbound Frame Address Translation
5.3.2.3 Incompatibility with Address Transparent Mode
iFCP gateways in address translation mode shall not originate or
accept frames that have the TRN bit set to one in the iFCP flags
field of the encapsulation header. The iFCP gateway shall
immediately abort any N_PORT login sessions with the iFCP gateway
from which it receives such frames as described in section 6.2.3.2.
6. iFCP Protocol
6.1 Overview
6.1.1 iFCP Transport Services
The main function of the iFCP protocol layer is to transport Fibre
Channel frame images between locally and remotely attached N_PORTs.
When transporting frames to a remote N_PORT, the iFCP layer
encapsulates and routes the Fibre Channel frames comprising each
Fibre Channel Information Unit via a predetermined TCP connection
for transport across the IP network.
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When receiving Fibre Channel frame images from the IP network, the
iFCP layer de-encapsulates and delivers each frame to the
appropriate N_PORT.
The iFCP layer processes the following types of traffic:
a) FC4 frame images associated with a Fibre Channel application
protocol.
b) FC2 frames comprising Fibre Channel link service requests and
responses
c) Fibre Channel broadcast frames
d) iFCP control messages required to setup or terminate an iFCP
session.
For FC4 N_PORT traffic and most FC2 messages the iFCP layer never
interprets the contents of the frame payload.
iFCP does interpret and process iFCP control messages and certain
FC2 extended link service messages as described in section 6.1.2
6.1.2 iFCP Support for Link Services
iFCP must intervene in the processing of those Fibre Channel
Extended Link Service (ELS) messages which contain N_PORT addresses
in the message payload or require other special handling, such as
an N_PORT login request (PLOGI).
In the former case, an iFCP gateway operating in address
translation mode must supplement the payload with additional
information that enables the receiving gateway to convert such
embedded N_PORT addresses to its frame of reference.
For out-bound Fibre Channel frames comprising such an ELS, the iFCP
layer creates the supplemental information based on frame content,
modifies the frame payload, then transmits the resulting Fibre
Channel frame with supplemental data through the appropriate TCP
connection.
For incoming iFCP frames containing supplemented Fibre Channel
ELSs, iFCP interprets the frame, including any supplemental
information, modifies the frame content, and forwards the resulting
frame to the destination N_PORT for further processing.
Section 7.1 describes the processing of these Extended Link Service
messages in detail.
6.2 TCP Stream Transport of iFCP Frames
6.2.1 iFCP Session Model
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An iFCP session consists of the pair of N_PORTs comprising the
session endpoints joined by a single TCP/IP connection.
An N_PORT is identified by its network address consisting of:
a) The N_PORT I/D assigned by the gateway to which the N_PORT is
locally attached and
b) The IP address of the gateway's iFCP Portal.
Since only one iFCP session may exist between a pair of N_PORTs,
the iFCP session is uniquely identified by the network addresses of
the session end points.
TCP connections that may be used for iFCP sessions between pairs of
iFCP portals are either "bound" or "unbound". An unbound
connection is a TCP connection that is not actively supporting an
iFCP session. A gateway implementation MAY establish a pool of
unbound connections to reduce the session setup time. Such pre-
existing TCP connections between iFCP Portals remain unbound and
uncommitted until allocated to an iFCP session through a CBIND
message (see section 8.1).
When the iFCP layer detects a Port Login (PLOGI) message creating
an iFCP session between a pair of N_PORTs, it may select an
existing unbound TCP connection or establish a new TCP connection,
and send the CBIND message down that TCP connection. This
allocates the TCP connection to that PLOGI login session.
6.2.2 iFCP Session Management
This section describes the protocols for establishing and
terminating an N_PORT login session.
6.2.2.1 Creating an iFCP Session
An iFCP session may be in one of the following states:
a) OPEN -- The session state in which Fibre Channel frame images
may be sent and received.
b) OPEN PENDING -- The session state after a gateway has issued a
CBIND request but no response has yet been received. No Fibre
Channel frames may be sent.
The gateway SHALL initiate the creation of an iFCP session in
response to a PLOGI ELS directed to a remote N_PORT from a locally
attached N_PORT as described in the following steps.
a) If no iFCP session exists, allocate a TCP connection to the
remote gateway. An implementation may use an existing
connection in the Unbound state or a new connection may be
created and placed in the Unbound state.
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b) If a connection cannot be allocated or created due to limited
resources, the gateway SHALL terminate the PLOGI with an LS_RJT
response. The Reason Code field in the LS_RJT message shall be
set to 0x09 (Unable to Perform Command Request) and the Reason
Explanation SHALL be set to 0x29 (Insufficient Resources to
Support Login).
c) If an iFCP session in the OPEN state already exists to the
remote N_PORT, the gateway SHALL forward the PLOGI ELS using the
existing session.
d) If the iFCP session does not exist, the gateway SHALL issue a
CBIND session control message (see section 8.1) and place the
session in the OPEN PENDING state.
e) In the event that a CBIND response is returned with one of the
following statuses, the PLOGI shall be terminated with an LS_RJT
message. Depending on the CBIND failure status, the Reason Code
and Reason Explanation SHALL be set to the following values
specified in [FC-FS].
CBIND Failure LS_RJT Reason LS_RJT Reason Code
Status Code Explanation
------------- ------------- ------------------
Unspecified Unable to Perform No additional
Reason (16) Command Request explanation (0x00)
(0x09)
No Such Device Unable to Perform Invalid N_PORT Name
(17) Command Request (0x0D).
(0x09)
Lack of Unable to Perform Insufficient
Resources (19) Command Request Resources to Support
(0x09). Login (0x29).
Incompatible Unable to Perform No additional
address Command Request Explanation (0x00)
translation mode (0x09)
(20)
Incorrect Unable to Perform No additional
protocol version Command Request explanation (0x00)
number (21) (0x09)
f) A CBIND response with a CBIND STATUS of "N_PORT session already
exists" indicates that the remote gateway has concurrently
initiated a CBIND request to create an iFCP session between the
same pair of N_PORTs. The receiving gateway SHALL terminate this
attempt and prepare to respond to an incoming CBIND request as
described below.
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The gateway receiving a CBIND request SHALL respond as follows:
a) If the receiver has a duplicate iFCP session in the OPEN PENDING
state, then the receiving gateway SHALL compare the IP address
of the sender with the receiver's IP address.
b) If the sender's IP address is greater, the receiver shall issue
a CBIND response of "Success" and SHALL place the session in the
OPEN state.
c) If the sender's IP address is less, the receiver shall issue a
CBIND RESPONSE of Failed - N_PORT session already exists. The
state of the receiver-initiated iFCP session SHALL BE unchanged.
d) If there is no duplicate iFCP session, the receiving gateway
SHALL issue a CBIND response. If a status of Success is
returned, the receiving gateway SHALL create the iFCP session
and place it in the OPEN state.
6.2.2.2 TCP Settings
This section describes optional TCP features and their usage in an
iFCP session. The core TCP protocol is defined in [RFC793]. TCP
implementation requirements and guidelines are specified in
[RFC1122].
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+-----------+------------+--------------+------------+------------+
| Feature | Applicable | RFC | Peer-wise | Requirement|
| | RFCs | Status | agreement | Level |
| | | | required? | |
+===========+============+==============+============+============+
| Keep Alive| [RFC1122] | None | No | SHOULD NOT |
| |(discussion)| | | use |
+-----------+------------+--------------+------------+------------+
| Tiny | [RFC896] | Standard | No | MUST NOT |
| Segment | | | | use |
| Avoidance | | | | |
| (Nagle) | | | | |
+-----------+------------+--------------+------------+------------+
| Window | [RFC1323] | Proposed | No | SHOULD use |
| Scale | | Standard | | |
+-----------+------------+--------------+------------+------------+
| Wrapped | [RFC1323] | Proposed | No | SHOULD use |
| Sequence | | Standard | | |
| Protection| | | | |
| (PAWS) | | | | |
+-----------+------------+--------------+------------+------------+
| Selective | [RFC2018], | Proposed | Yes | SHOULD use |
| Ack | [RFC2883] | Standard | | |
+-----------+------------+--------------+------------+------------+
| Congestion| [RFC2581] | Proposed | No | SHOULD use |
| Control | | Standard | | |
| with Fast | | | | |
| Recovery | | | | |
+-----------+------------+--------------+------------+------------+
| Explicit | [RFC2481] | Experimental| Yes | MAY use |
| Congestion| | | | |
| Control | | | | |
+-----------+------------+--------------+------------+------------+
Table 1 -- Usage of Optional TCP Features
The following sections describe these options in greater detail.
6.2.2.2.1 Keep Alive
Keep Alive speeds fault detection and the cleanup of dysfunctional
TCP connections by sending traffic when a connection would
otherwise be idle. The issues are discussed in [RFC1122].
In order to test the device more comprehensively, Fibre Channel
applications, such as storage, may implement an equivalent keep
alive function at the FC4 level. For that reason and the
considerations described in [RFC1122], keep alive at the transport
layer SHOULD NOT be implemented.
6.2.2.2.2 'Tiny' Segment Avoidance (Nagle)
The Nagle algorithm described in [RFC896] is designed to avoid the
overhead of small segments by delaying transmission in order to
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agglomerate transfer requests into a large segment. In iFCP, such
small transfers often contain I/O requests. Hence, the
transmission delay of the Nagle algorithm may decrease I/O
throughput. For that reason, the Nagle algorithm SHOULD NOT be
used.
6.2.2.2.3 Window Scale
Window scaling, as specified in [RFC1323], allows full utilization
of links with large bandwidth - delay products. For this reason,
an iFCP implementation SHOULD support this capability.
6.2.2.2.4 Wrapped Sequence Protection (PAWS)
TCP segments are identified with 32-bit sequence numbers. In
networks with large bandwidth - delay products, it is therefore
possible for more than one TCP segment with the same sequence
number to be in flight. In iFCP, receipt of such a sequence out of
order may cause out-of-order frame delivery or data corruption.
Consequently, this feature SHOULD be supported as described in
[RFC1323].
6.2.2.2.5 Selective Acknowledge
Selective acknowledge acknowledges segments as they arrive, rather
than waiting for all prior missing segments to be delivered.
Consequently, error recovery is faster since only the
unacknowledged segments must be resent. Selective Acknowledge
SHOULD therefore be supported as described in [RFC2018] and
[RFC2883].
6.2.2.2.6 Congestion Control with Fast Recovery
Fast recovery, as specified in [RFC2581], involves the use of
duplicate acknowledgements to expedite error recovery by notifying
the sender that a segment may have been lost. An iFCP
implementation SHOULD support this feature.
6.2.2.2.7 Explicit Congestion Control
TCP congestion avoidance throttles the inflow of data to the
network when data loss is experienced. Essentially, the system is
driven beyond saturation before load shedding occurs.
The method of explicit congestion notification in [RFC2481]
specifies an experimental approach for congestion avoidance that is
not triggered by data loss and hence does not incur the error
recovery penalties. This method relies on the insertion of router-
generated notifications into the TCP Acknowledgement to inform the
sender when the system is approaching its load carrying capacity.
As such, it requires support by the routing infrastructure and MAY
be supported by an iFCP implementation.
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6.2.3 Terminating an N_PORT Login Session
An N_PORT login session SHALL be terminated or aborted in response
to one of the following events:
a) An LS_RJT response is returned to the gateway that issued the
PLOGI ELS. The gateway SHALL forward the LS_RJT to the local
N_PORT and complete the session as described in section
6.2.3.1.
b) An ACC received from a remote device in response to a LOGO. The
gateway SHALL forward the ACC to the local N_PORT and complete
the session as described in section 6.2.3.1.
c) For an FC frame received from the IP network, a gateway detects
a CRC error in the encapsulation header. The gateway shall
abort the session as described in section 6.2.3.2.
d) The TCP connection associated with the login session fails for
any reason. The gateway detecting the failed connection shall
abort the session as described in section 6.2.3.2.
6.2.3.1 N_PORT Login Session Completion
An N_PORT login session is completed in response to a rejected
PLOGI request as described in section 6.2.3 or a successful LOGO
ELS.
The gateway receiving one of the above responses shall issue an
Unbind session control ELS as described in section 8.2.
In response to the Unbind message, either gateway may choose to
close the connection or return it to a pool of unbound connections.
6.2.3.2 Aborting an N_PORT Login Session
An N_PORT login session SHALL be aborted if the TCP connection is
spontaneously terminated or whenever one of the following occurs:
a) An encapsulation error is detected as described in section
6.4.3.
b) The gateway receives an encapsulated frame from a gateway
operating in an incompatible address translation mode as
specified in section 5.3.2.3 or 5.3.1.2.
In any event, the TCP connection shall be closed. If the local
N_PORT has logged in to the remote N_PORT, the gateway SHALL send a
LOGO to the local N_PORT.
6.3 IANA Considerations
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There will be a well-known port for iFCP connections. Such port
will be used for both TCP traffic (iFCP regular traffic) and UDP
traffic (iFCP broadcast services only, see 10.4). This well-known
port will b e r e g i s t r e d e w i t h A I A N .
An iFCP Portal may initiate a connection using any TCP port number
consistent with its implementation of the TCP/IP stack, provided
each port number is unique. To prevent the receipt of stale data
associated with a previous connection using a given port number,
the provisions of [RFC1323] SHOULD be observed.
6.4 Encapsulation of Fibre Channel Frames
This section describes the iFCP encapsulation of Fibre Channel
frames. The encapsulation is based on the common encapsulation
format defined in [ENCAP].
The format of an encapsulated frame is shown below:
+--------------------+
| Header |
+--------------------+-----+
| SOF | f |
+--------------------+ F r |
| FC frame content | C a |
+--------------------+ m |
| EOF | e |
+--------------------+-----+
Figure 11 -- Encapsulation Format
The encapsulation consists of a 7-word header, an SOF delimiter
word, the FC frame (including the Fibre Channel CRC), and an EOF
delimiter word. The header and delimiter formats are described in
the following sections.
6.4.1 Encapsulation Header Format
W|------------------------------Bit------------------------------|
o| |
r|3 3 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1 |
d|1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0|
+---------------+---------------+---------------+---------------+
0| Protocol# | Version | -Protocol# | -Version |
+---------------+---------------+---------------+---------------+
1| Reserved (must be zero) |
+---------------+---------------+---------------+---------------+
2| LS_COMMAND | iFCP Flags | SOF | EOF |
+-----------+---+---------------+-----------+---+---------------+
3| Flags | Frame Length | -Flags | -Frame Length |
+-----------+-------------------+-----------+-------------------+
4| Time Stamp [integer] |
+---------------------------------------------------------------+
5| Time Stamp [fraction] |
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+---------------------------------------------------------------+
6| CRC |
+---------------------------------------------------------------+
Common Encapsulation Fields:
Protocol# IANA-assigned protocol number
identifying the protocol using the
encapsulation. For iFCP the value is
(/TBD/).
Version Encapsulation version
-Protocol# Ones complement of the protocol#
-Version Ones complement of the version
Flags Encapsulation flags (see 6.4.1.1)
Frame Length Contains the length of the entire FC
Encapsulated frame including the FC
Encapsulation Header and the FC frame
(including SOF and EOF words) in units
of 32-bit words.
-Flags Ones-complement of the Flags field.
-Frame Length Ones-complement of the Frame Length
field.
Time Stamp [integer] Integer component of the frame time
stamp in SNTP format [RFC2030].
Time Stamp Fractional component of the time stamp
[fraction] in SNTP format [RFC2030].
CRC Header CRC. MUST be valid for iFCP.
The time stamp fields are used to enforce the limit on the
lifetime of a Fibre Channel frame as described in section
9.2.1.
iFCP-specific fields:
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LS_COMMAND For an augmented ELS ACC response, the
LS_COMMAND field SHALL contain bits 31
through 24 of the LS_COMMAND to which
the ACC applies. Otherwise the
LS_COMMAND field shall be set to zero.
iFCP Flags iFCP-specific flags (see below)
SOF Copy of the SOF delimiter encoding
(see section 6.4.2)
EOF Copy of the EOF delimiter encoding
(see section 6.4.2)
The iFCP flags word has the following format:
|------------------------Bit----------------------------|
| |
| 23 22 21 20 19 18 17 16 |
+------+------+------+------+------+------+------+------+
| Reserved | SES | TRN | AUG |
+------+------+------+------+------+------+------+------+
Figure 12 -- iFCP Flags Word
iFCP Flags:
SES 1 = Session control frame (TRN and AUG MUST be
0)
TRN 1 = Address transparent mode enabled
0 = Address translation mode enabled
AUG 1 = Augmented frame.
6.4.1.1 Common Encapsulation Flags
The iFCP usage of the common encapsulation flags is shown below:
|------------------------Bit--------------------------|
| |
| 31 30 29 28 27 26 |
+--------------------------------------------+--------+
| Reserved | CRCV |
+--------------------------------------------+--------+
For iFCP, the CRC field MUST be valid and CRCV MUST be set to one.
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6.4.2 SOF and EOF Delimiter Fields
The format of the delimiter fields is shown below.
W|------------------------------Bit------------------------------|
o| |
r|3 3 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1 |
d|1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0|
+---------------+---------------+-------------------------------+
0| SOF | SOF | -SOF | -SOF |
+---------------+---------------+-------------------------------+
1| |
+----- FC frame content -----+
| |
+---------------+---------------+-------------------------------+
n| EOF | EOF | -EOF | -EOF |
+---------------+---------------+-------------------------------+
Figure 13 -- FC Frame Encapsulation Format
SOF (bits 31-24 and bits 23-16 in word 0): iFCP uses the
following subset of the SOF fields described in [ENCAP].
+-------+----------+
| FC | |
| SOF | SOF Code |
+-------+----------+
| SOFi2 | 0x2D |
| SOFn2 | 0x35 |
| SOFi3 | 0x2E |
| SOFn3 | 0x36 |
+-------+----------+
Table 2-- Translation of FC SOF Values to SOF Field Contents
-SOF (bits 15-8 and 7-0 in word 0): The -SOF fields contain the
ones complement of the value in the SOF fields.
EOF (bits 31-24 and 23-16 in word n): iFCP uses the following
subset of EOF fields specified in [ENCAP].
+-------+----------+
| FC | |
| EOF | EOF Code |
+-------+----------+
| EOFn | 0x41 |
| EOFt | 0x42 |
+-------+----------+
Table 3 -- Translation of FC EOF Values to EOF Field Contents
-EOF (bits 15-8 and 7-0 in word n): The -EOF fields contain the
one's complement of the value in the EOF fields.
iFCP implementations SHALL place a copy of the SOF and EOF
delimiter codes in the appropriate header fields.
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6.4.3 Frame Encapsulation
A Fibre Channel Frame to be encapsulated MUST first be validated as
described in [FC-FS]. Any frames received from a locally attached
Fibre Channel device that do not pass the validity tests in [FC-FS]
SHALL be discarded by the gateway.
Frames types submitted for encapsulation and forwarding on the IP
network SHALL have one of the SOF delimiters in Table 2 and an EOF
delimiter from Table 3. Other valid frame types MUST be processed
internally by the gateway as specified in the appropriate Fibre
Channel specification.
Prior to submitting a frame for encapsulation, a gateway in address
translation mode SHALL replace the D_ID address, and, if processing
an augmented ELS, SHALL format the frame payload and add the
supplemental information as specified in section 7.1. The gateway
SHALL then calculate a new FC CRC on the reformatted frame.
A gateway in address transparent mode MAY encapsulate and transmit
the frame image without recalculating the FC CRC.
The frame originator MUST then create and fill in the header and
the SOF and EOF delimiter words as specified above.
6.4.4 Frame De-encapsulation
The receiving gateway SHALL perform de-encapsulation as follows:
Upon receiving the encapsulated frame, the gateway SHALL check the
header CRC. If the header CRC is invalid, the gateway SHALL
terminate the N_PORT login session as described in section 6.2.3.2.
After validating the header CRC, the receiving gateway MAY verify
the frame propagation delay as described in section 9.2.1. If the
propagation delay is too long, the frame SHALL be discarded.
Otherwise, the gateway SHALL check the SOF and EOF in the
encapsulation header. A frame shall be discarded if it has an SOF
code that is not in Table 2 or an EOF code that is not in Table 3.
The gateway shall then de-encapsulate the frame. If operating in
address translation mode, the gateway shall:
a) Check the FC CRC and discard the frame if the CRC is invalid.
b) Replace the S_ID with the N_PORT alias of the frame originator
c) If processing an augmented ELS, replace the ELS frame with a
copy whose payload has been modified as specified in section
7.1.
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The resulting frame SHALL then be delivered to the N_PORT specified
in the D_ID field. If the frame contents have been modified by the
receiving gateway, a new FC CRC SHALL be calculated.
7. Fibre Channel Link Services
Link services provide a set of Fibre Channel functions that allow a
port to send control information or request another port to perform
a specific control function.
Each Link Service message (request and reply) is carried by a Fibre
Channel sequence, and can be segmented into multiple frames.
The iFCP Layer is responsible for transporting link service
messages across the IP fabric. This includes mapping Link Service
messages appropriately from the domain of the Fibre Channel
transport to that of the IP network. This process may require
special processing and the inclusion of augmented data by the iFCP
layer.
Each link service or extended link service is processed according
to one of the following rules:
a) Transparent û The link service message and reply MUST be
transported to the receiving N_PORT by the iFCP gateway without
altering the message payload. The link service message and reply
are not processed by the iFCP implementation.
b) Augmented - Applies to an extended link service reply or
request containing Fibre Channel addresses in the payload or
requiring other special processing by the iFCP implementation.
The processing for augmented link services is described in this
section.
c) Rejected û When issued by a locally attached N_PORT, the
specified link service request MUST be rejected by the iFCP
implementation. The gateway SHALL respond to a rejected link
service message by returning an LS_RJT response with a Reason
Code of 0x0B (Command Not Supported) and a Reason Code
Explanation of 0x0 (No Additional Explanation).
This section describes the processing for augmented link services,
including the manner in which augmentation data is transmitted over
the IP network.
Appendix A enumerates all link services and the iFCP processing
policy that applies to each.
7.1 Augmented Link Service Messages
Augmentation applies to extended link service requests that require
the intervention of the iFCP layer. Such intervention is required
in order to:
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a) Service any ELS that requires special handling, such as a PLOGI.
b) In address translation mode only, service any ELS which has an
N_PORT address in the payload.
Such ELS messages are transmitted in a Fibre Channel frame having
the following format:
Word
31 24 23 0
+----------+------------------------------------------------+
0| R_CTL | D_ID |
| [22] | [Destination of extended link Service request] |
+----------+------------------------------------------------+
1| CS_CTL | S_ID |
| | [Source of extended link service request] |
+----------+------------------------------------------------+
2| TYPE | F_CTL |
+----------+------------------+-----------------------------+
3| SEQ_ID | DF_CTL | SEQ_CNT |
+----------+------------------+-----------------------------+
4| OX_ID | RX_ID |
+-----------------------------+-----------------------------+
5| Parameter |
| [ 00 00 00 00 ] |
+-----------------------------------------------------------+
6| LS_COMMAND |
| [Extended Link Service Command Code] |
+-----------------------------------------------------------+
7| |
.| Additional Service Request Parameters |
.| ( if any ) |
n| |
+-----------------------------------------------------------+
Figure 14 -- Format of Extended Link Service Frame
7.2 Augmented Link Services Requiring Payload Address Translation
This section describes the handling for ELS frames containing
N_PORT addresses in the ELS payload. Such addresses SHALL only be
translated when the gateway is operating in address translation
mode. When operating in address transparent mode, these addresses
SHALL NOT be translated and such ELS messages SHALL not be sent as
augmented frames unless other special processing is required.
Supplemental data includes information required by the receiving
gateway to convert an N_PORT address in the payload to an N_PORT
address in the receiving gatewayÆs address space. The following
rules define the manner in which such supplemental data is packaged
and referenced.
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For an N_PORT address field, the gateway originating the frame MUST
set the value in the payload to identify the address translation
type as follows:
0x00 00 01 û The gateway receiving the frame from the IP
network MUST replace the contents of the field with the N_PORT
alias of the frame originator. This translation type MUST be
used when the address to be converted is that of the source
N_PORT.
0x00 00 02 û The gateway receiving the frame from the IP
network MUST replace the contents of the field with the N_PORT
I/D of the destination N_PORT. This translation type MUST be
used when the address to be converted is that of the
destination N_PORT
0x00 00 03 û The gateway receiving the frame from the IP
network MUST reference augmentation data to set the field
contents. The augmentation information is the 64-bit world wide
identifier of the N_PORT as set forth in the Fibre Channel
specification [FC-FS]. If not otherwise part of the ELS, this
information MUST be appended as described below. This
translation type SHALL NOT be used when the address to be
converted corresponds to that of the frame originator or
recipient.
Since Fibre Channel addressing rules prohibit the assignment of
fabric addresses with a domain I/D of 0, the above codes will never
correspond to valid N_PORT fabric IDs.
For translation type 3, the receiving gateway SHALL obtain the
information needed to fill in the ELS field by converting the
specified N_PORT world-wide identifier to a gateway IP address and
N_PORT ID. This information MUST be obtained through a name server
query. If the N_PORT is locally attached, the gateway MUST fill in
the field with the N_PORT ID. If the N_PORT is remotely attached,
the gateway MUST assign and fill in the field with an N_PORT alias.
If an N_PORT alias has already been assigned, it MUST be reused.
In the event that the sending gateway cannot obtain the world wide
identifier of an N_PORT, or a receiving gateway cannot obtain the
IP address and N_PORT ID, the gateway detecting the error SHALL
terminate the request with an LS_RJT message as described in [FCS].
The Reason Code SHALL be set to 0x07 (protocol error) and the
Reason Explanation SHALL be set to 0x1F (Invalid N_PORT
identifier).
Supplemental data is sent with the ELS request or ACC frames in one
of the following ways:
a) By appending the necessary data to the end of the ELS frame.
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b) By extending the sequence with the addition of additional
frames.
In the first case, a new frame SHALL be created whose length
includes the supplemental data. The procedure for extending the ELS
sequence with additional frames is dependent on the format of the
augmented ELS.
After applying the supplemental data, the receiving gateway SHALL
forward the resulting ELS frames to the destination N_PORT with the
supplemental information removed.
When the ACC response must be augmented, the receiving gateway MUST
act as a proxy for the originator, retaining the state needed to
process the response from the N_PORT to which the request was
directed.
7.3 Augmented Link Services
The following Link Service Messages must receive special processing
or be supplemented with additional control data.
An encapsulated Fibre Channel frame that is part of an augmented
ELS MUST have the AUG bit set to one in the iFCP FLAGS field of the
encapsulation header as specified in section 6.4.1. The
supplemental data (if any) MUST be appended as described in the
following section. An ELS ACC frame that is augmented must be
similarly formatted.
Link Service Message LS_COMMAND Mnemonic
-------------------- ---------- --------
Abort Exchange 0x06 00 00 00 ABTX
Discover Address 0x52 00 00 00 ADISC
Discover Address Accept 0x02 00 00 00 ADISC ACC
FC Address Resolution Protocol 0x55 00 00 00 FARP-REPLY
Reply
FC Address Resolution Protocol 0x54 00 00 00 FARP-REQ
Request
Logout 0x05 00 00 00 LOGO
Port Login 0x30 00 00 00 PLOGI
Read Exchange Concise 0x13 00 00 00 REC
Read Exchange Concise Accept 0x02 00 00 00 REC ACC
Read Exchange Status Block 0x08 00 00 00 RES
Read Exchange Status Block 0x02 00 00 00 RES ACC
Accept
Read Link Error Status Block 0x0F 00 00 00 RLS
Read Sequence Status Block 0x09 00 00 00 RSS
Reinstate Recovery Qualifier 0x12 00 00 00 RRQ
Request Sequence Initiative 0x0A 00 00 00 RSI
Third Party Process Logout 0x24 00 00 00 TPRLO
The formats of each augmented ELS, including supplemental data
where applicable, are shown in the following sections. Each ELS
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diagram shows the basic format, as specified in the applicable FC
standard, followed by supplemental data as shown in the example
below.
+------+------------+------------+-----------+----------+
| Word | Bits 31û24 | Bits 23û16 | Bits 15û8 | Bits 7-0 |
+------+------------+------------+-----------+----------+
| 0 | LS_COMMAND |
+------+------------+------------+-----------+----------+
| 1 | |
| . | |
| . | ELS Payload |
| | |
| n | |
+======+============+============+===========+==========+
| n+1 | |
| . | Supplemental Data |
| . | (if any) |
| n+k | |
+======+================================================+
ELS Diagram (single FC Frame Format)
7.3.1 Abort Exchange (ABTX)
ELS Format:
+------+------------+------------+-----------+----------+
| Word | Bits 31û24 | Bits 23û16 | Bits 15û8 | Bits 7-0 |
+------+------------+------------+-----------+----------+
| 0 | Cmd = 0x6 | 0x00 | 0x00 | 0x00 |
+------+------------+------------+-----------+----------+
| 1 | RRQ Status | Exchange Originator S_ID |
+------+------------+------------+-----------+----------+
| 2 | OX_ID of Tgt exchange | RX_ID of tgt exchange|
+------+------------+------------+-----------+----------+
| 3-10 | Optional association header (32 bytes |
+======+============+============+===========+==========+
Fields Requiring Translation Supplemental Data
Address Translation Type (see (type 3 only)
------------------- section 7.2) ------------
-----------
Exchange Originator 1, 2 N/A
S_ID
Other Special Processing:
None
7.3.2 Discover Address (ADISC)
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Format of ADISC ELS:
+------+------------+------------+-----------+----------+
| Word | Bits 31û24 | Bits 23û16 | Bits 15û8 | Bits 7-0 |
+------+------------+------------+-----------+----------+
| 0 | Cmd = 0x52 | 0x00 | 0x00 | 0x00 |
+------+------------+------------+-----------+----------+
| 1 | Reserved | Hard address of ELS Originator |
+------+------------+------------+-----------+----------+
| 2-3 | Port Name of Originator |
+------+------------+------------+-----------+----------+
| 4-5 | Node Name of originator |
+------+------------+------------+-----------+----------+
| 6 | Rsvd | N_PORT I/D of ELS Originator |
+======+============+============+===========+==========+
Fields Requiring Translation Supplemental Data
Address Translation Type (see (type 3 only)
------------------- section 7.2) ------------
-------------
N_PORT I/D of ELS 1 N/A
Originator
Other Special Processing:
The Hard Address of the ELS originator SHALL be set to 0.
7.3.3 Discover Address Accept (ADISC ACC)
Format of ADISC ACC ELS:
+------+------------+------------+-----------+----------+
| Word | Bits 31û24 | Bits 23û16 | Bits 15û8 | Bits 7-0 |
+------+------------+------------+-----------+----------+
| 0 | Cmd = 0x20 | 0x00 | 0x00 | 0x00 |
+------+------------+------------+-----------+----------+
| 1 | Reserved | Hard address of ELS Originator |
+------+------------+------------+-----------+----------+
| 2-3 | Port Name of Originator |
+------+------------+------------+-----------+----------+
| 4-5 | Node Name of originator |
+------+------------+------------+-----------+----------+
| 6 | Rsvd | N_PORT I/D of ELS Originator |
+======+============+============+===========+==========+
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Fields Requiring Translation Supplemental Data
Address Translation Type (see (type 3 only)
------------------- section 7.2) ------------
------------
N_PORT I/D of ELS 1 N/A
Originator
Other Special Processing:
The Hard Address of the ELS originator SHALL be set to 0.
7.3.4 FC Address Resolution Protocol Reply (FARP-REPLY)
The FARP-REPLY ELS is used in conjunction with the FARP-REQ ELS
(see section 7.3.5) to perform the address resolution services
required by the FC-VI protocol [FC-VI] and the Fibre Channel
mapping of IP and ARP specified in RFC 2625 [RFC2625].
Format of FARP-REPLY ELS:
+------+------------+------------+-----------+----------+
| Word | Bits 31û24 | Bits 23û16 | Bits 15û8 | Bits 7-0 |
+------+------------+------------+-----------+----------+
| 0 | Cmd = 0x55 | 0x00 | 0x00 | 0x00 |
+------+------------+------------+-----------+----------+
| 1 | Match Addr | Requesting N_PORT Identifier |
| | Code Points| |
+------+------------+------------+-----------+----------+
| 2 | Responder | Responding N_PORT Identifier |
| | Action | |
+------+------------+------------+-----------+----------+
| 3-4 | Requesting N_PORT Port_Name |
+------+------------+------------+-----------+----------+
| 5-6 | Requesting N_PORT Node_Name |
+------+------------+------------+-----------+----------+
| 7-8 | Responding N_PORT Port_Name |
+------+------------+------------+-----------+----------+
| 9-10 | Responding N_PORT Node_Name |
+------+------------+------------+-----------+----------+
| 11-14| Requesting N_PORT IP Address |
+------+------------+------------+-----------+----------+
| 15-18| Responding N_PORT IP Address |
+======+============+============+===========+==========+
Fields Requiring Translation Supplemental Data
Address Translation Type (see (type 3 only)
section 7.2)
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------------------- ------------- -----------------
Requesting N_PORT 2 N/A
Identifier
Responding N_PORT 1 N/A
identifier
Other Special Processing:
None.
7.3.5 FC Address Resolution Protocol Request (FARP-REQ)
The FARP-REQ ELS is used to in conjunction with the FC-VI protocol
[FC-VI] and IP to FC mapping of RFC 2625 [RFC2625] to perform IP
and FC address resolution in an FC fabric. The FARP-REQ ELS is
usually directed to the fabric broadcast server at well-known
address 0xFF-FF-FF for retransmission to all attached N_PORTs.
Section 10.4 describes the iFCP implementation of FC broadcast
server functionality in an iFCP fabric.
Format of FARP_REQ ELS:
+------+------------+------------+-----------+----------+
| Word | Bits 31û24 | Bits 23û16 | Bits 15û8 | Bits 7-0 |
+------+------------+------------+-----------+----------+
| 0 | Cmd = 0x54 | 0x00 | 0x00 | 0x00 |
+------+------------+------------+-----------+----------+
| 1 | Match Addr | Requesting N_PORT Identifier |
| | Code Points| |
+------+------------+------------+-----------+----------+
| 2 | Responder | Responding N_PORT Identifier |
| | Action | |
+------+------------+------------+-----------+----------+
| 3-4 | Requesting N_PORT Port_Name |
+------+------------+------------+-----------+----------+
| 5-6 | Requesting N_PORT Node_Name |
+------+------------+------------+-----------+----------+
| 7-8 | Responding N_PORT Port_Name |
+------+------------+------------+-----------+----------+
| 9-10 | Responding N_PORT Node_Name |
+------+------------+------------+-----------+----------+
| 11-14| Requesting N_PORT IP Address |
+------+------------+------------+-----------+----------+
| 15-18| Responding N_PORT IP Address |
+======+============+============+===========+==========+
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Fields Requiring Translation Supplemental Data
Address Translation Type (see (type 3 only)
------------------- section 7.2) -----------------
-----------
Requesting N_PORT 3 Requesting N_PORT
Identifier Port Name
Other Special Processing:
None.
7.3.6 Logout (LOGO)
ELS Format:
+------+------------+------------+-----------+----------+
| Word | Bits 31û24 | Bits 23û16 | Bits 15û8 | Bits 7-0 |
+------+------------+------------+-----------+----------+
| 0 | Cmd = 0x5 | 0x00 | 0x00 | 0x00 |
+------+------------+------------+-----------+----------+
| 1 | Rsvd | N_PORT I/D being logged out |
+------+------------+------------+-----------+----------+
| 2-3 | Port name of the LOGO originator (8 bytes) |
+======+============+============+===========+==========+
This ELS shall always be sent as an augmented ELS regardless of the
translation mode in effect.
Fields Requiring Translation Supplemental Data
Address Translation Type(see (type 3 only)
------------------- section 7.2) --------------
-----------
N_PORT I/D Being 1 N/A
Logged Out
Other Special Processing:
See section 6.2.3.1.
7.3.7 Port Login (PLOGI)
PLOGI provides the mechanism for establishing a login session
between two N_PORTs. In iFCP, a PLOGI request addressed to a
remotely attached N_PORT may trigger the creation of an iFCP
session, if one does not already exist. Otherwise, the PLOGI and
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ACC payloads MUST be passed transparently to the destination
N_PORT.
The PLOGI request and ACC response carry information identifying
the originating N_PORT, including specification of its capabilities
and limitations. If the destination N_PORT accepts the login
request, it sends an accept (an ACC frame with PLOGI payload),
specifying its capabilities and limitations. This exchange
establishes the operating environment for the two N_PORTs.
The following figure is duplicated from [FC-FS], and shows the
PLOGI message format for both request and accept (ACC) response. A
port will reject a PLOGI request by transmitting an LS_RJT message,
which contains no payload.
Byte
Offset
+----------------------------------+
0 | LS_COMMAND | 4 Bytes
+----------------------------------+
4 | COMMON SERVICE PARAMETERS | 16 Bytes
+----------------------------------+
20 | PORT NAME | 8 Bytes
+----------------------------------+
28 | NODE NAME | 8 Bytes
+----------------------------------+
36 | CLASS 1 SERVICE PARAMETERS | 16 Bytes
+----------------------------------+
52 | CLASS 2 SERVICE PARAMETERS | 16 Bytes
+----------------------------------+
68 | CLASS 3 SERVICE PARAMETERS | 16 Bytes
+----------------------------------+
86 | CLASS 4 SERVICE PARAMETERS | 16 Bytes
+----------------------------------+
102 | VENDOR VERSION LEVEL | 16 Bytes
+----------------------------------+
Total Length = 116 bytes
Figure 15 -- Format of PLOGI Request and ACC Payloads
Details on the above fields, including common and class-based
service parameters, can be found in [FC-FS].
7.3.8 Read Exchange Concise
ELS Format:
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+------+------------+------------+-----------+----------+
| Word | Bits 31û24 | Bits 23û16 | Bits 15û8 | Bits 7-0 |
+------+------------+------------+-----------+----------+
| 0 | Cmd = 0x13 | 0x00 | 0x00 | 0x00 |
+------+------------+------------+-----------+----------+
| 1 | Rsvd | Exchange Originator S_ID |
+------+------------+------------+-----------+----------+
| 2 | OX_ID | RX_ID |
+======+============+============+===========+==========+
| 3-4 |Port name of the exchange originator (8 bytes) |
| | (present only for translation type 3) |
+======+============+============+===========+==========+
Fields Requiring Translation Supplemental Data
Address Translation Type(see (type 3 only)
------------------- section 7.2) ------------------
-----------
Exchange Originator 1, 2 or 3 Port Name of the
S_ID Exchange
Originator
Other Special Processing:
None.
7.3.9 Read Exchange Concise Accept
Format of ACC Response:
+------+------------+------------+-----------+----------+
| Word | Bits 31û24 | Bits 23û16 | Bits 15û8 | Bits 7-0 |
+------+------------+------------+-----------+----------+
| 0 | Acc = 0x02 | 0x00 | 0x00 | 0x00 |
+------+------------+------------+-----------+----------+
| 1 | OX_ID | RX_ID |
+------+------------+------------+-----------+----------+
| 2 | Rsvd | Exchange Originator N_PORT ID |
+------+------------+------------+-----------+----------+
| 3 | Rsvd | Exchange Responder N_PORT ID |
+------+------------+------------+-----------+----------+
| 4 | Data Transfer Count |
+------+------------+------------+-----------+----------+
| 5 | Exchange Status |
+======+============+============+===========+==========+
| 6-7 |Port name of the Exchange Originator (8 bytes) |
+======+============+============+===========+==========+
| 8-9 |Port name of the Exchange Responder (8 bytes) |
+======+============+============+===========+==========+
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Fields Requiring Translation Supplemental Data
Address Translation Type(see (type 3 only)
------------------- section 7.2) ------------------
-----------
Exchange Originator 1, 2 or 3 Port Name of the
N_PORT I/D Exchange Originator
Exchange Responder 1, 2 or 3 Port Name of the
N_PORT I/D Exchange Responder
When supplemental data is required, the ELS shall always be
extended by 4 words as shown above. If the translation type for
the Exchange Originator N_PORT I/D or the Exchange Responder N_PORT
I/D is 1 or 2, the corresponding 8-byte port name SHALL be set to
all zeros.
Other Special Processing:
None.
7.3.10 Read Exchange Status Block (RES)
ELS Format:
+------+------------+------------+-----------+----------+
| Word | Bits 31û24 | Bits 23û16 | Bits 15û8 | Bits 7-0 |
+------+------------+------------+-----------+----------+
| 0 | Cmd = 0x13 | 0x00 | 0x00 | 0x00 |
+------+------------+------------+-----------+----------+
| 1 | Rsvd | Exchange Originator S_ID |
+------+------------+------------+-----------+----------+
| 2 | OX_ID | RX_ID |
+------+------------+------------+-----------+----------+
| 3-10 | Association header (may be optionally reqÆd) |
+======+============+============+===========+==========+
| 11-12| Port name of the Exchange Originator (8 bytes) |
+======+============+============+===========+==========+
Fields Requiring Translation Supplemental Data
Address Translation Type(see (type 3 only)
------------------- section 7.2) ------------------
-----------
Exchange Originator 1, 2 or 3 Port Name of the
S_ID Exchange Originator
Other Special Processing:
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None.
7.3.11 Read Exchange Status Block Accept
Format of ELS Accept Response:
+------+------------+------------+-----------+----------+
| Word | Bits 31û24 | Bits 23û16 | Bits 15û8 | Bits 7-0 |
+------+------------+------------+-----------+----------+
| 0 | Acc = 0x02 | 0x00 | 0x00 | 0x00 |
+------+------------+------------+-----------+----------+
| 1 | OX_ID | RX_ID |
+------+------------+------------+-----------+----------+
| 2 | Rsvd | Exchange Originator N_PORT ID |
+------+------------+------------+-----------+----------+
| 3 | Rsvd | Exchange Responder N_PORT ID |
+------+------------+------------+-----------+----------+
| 4 | Exchange Status Bits |
+------+------------+------------+-----------+----------+
| 5 | Reserved |
+------+------------+------------+-----------+----------+
| 6ûn | Service Parameters and Sequence Statuses |
| | as described in [FCS] |
+======+============+============+===========+==========+
|n+1- | Port name of the Exchange Originator (8 bytes) |
|n+2 | |
+======+============+============+===========+==========+
|n+3- | Port name of the Exchange Responder (8 bytes) |
|n+4 | |
+======+============+============+===========+==========+
Fields Requiring Translation Supplemental Data
Address Translation Type(see (type 3 only)
------------------- section 7.2) ------------------
-----------
Exchange Originator 1, 2 or 3 Port Name of the
N_PORT I/D Exchange Originator
Exchange Responder 1, 2 or 3 Port Name of the
N_0ORT I/D Exchange Responder
When supplemental data is required, the ELS SHALL be extended by 4
words as shown above. If the translation type for the Exchange
Originator N_PORT I/D or the Exchange Responder N_PORT I/D is 1 or
2, the corresponding 8-byte port name SHALL be set to all zeros.
Other Special Processing:
None.
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7.3.12 Read Link Error Status (RLS)
ELS Format:
+------+------------+------------+-----------+----------+
| Word | Bits 31û24 | Bits 23û16 | Bits 15û8 | Bits 7-0 |
+------+------------+------------+-----------+----------+
| 0 | Cmd = 0x0F | 0x00 | 0x00 | 0x00 |
+------+------------+------------+-----------+----------+
| 1 | Rsvd | N_PORT Identifier |
+======+============+============+===========+==========+
| 2-3 | Port name of the N_PORT (8 bytes) |
+======+============+============+===========+==========+
Fields Requiring Translation Supplemental Data (type
Address Translation Type(see 3 only)
------------------- section 7.2) ------------------
-----------
N_PORT Identifier 1, 2 or 3 Port Name of the N_PORT
Other Special Processing:
None.
7.3.13 Read Sequence Status Block (RSS)
ELS Format:
+------+------------+------------+-----------+----------+
| Word | Bits 31û24 | Bits 23û16 | Bits 15û8 | Bits 7-0 |
+------+------------+------------+-----------+----------+
| 0 | Cmd = 0x09 | 0x00 | 0x00 | 0x00 |
+------+------------+------------+-----------+----------+
| 1 | SEQ_ID | Exchange Originator S_ID |
+------+------------+------------+-----------+----------+
| 2 | OX_ID | RX_ID |
+======+============+============+===========+==========+
| 3-4 |Port name of the Exchange Originator (8 bytes) |
+======+============+============+===========+==========+
Fields Requiring Translation Supplemental Data
Address Translation Type(see (type 3 only)
------------------- section 7.2) ------------------
-----------
Exchange Originator 1, 2 or 3 Port Name of the
S_ID Exchange Originator
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Other Special Processing:
None.
7.3.14 Reinstate Recovery Qualifier (RRQ)
ELS Format:
+------+------------+------------+-----------+----------+
| Word | Bits 31û24 | Bits 23û16 | Bits 15û8 | Bits 7-0 |
+------+------------+------------+-----------+----------+
| 0 | Cmd = 0x12 | 0x00 | 0x00 | 0x00 |
+------+------------+------------+-----------+----------+
| 1 | Rsvd | Exchange Originator S_ID |
+------+------------+------------+-----------+----------+
| 2 | OX_ID | RX_ID |
+------+------------+------------+-----------+----------+
| 3-10 | Association header (may be optionally reqÆd) |
+======+============+============+===========+==========+
Fields Requiring Translation Supplemental Data
Address Translation Type(see (type 3 only)
------------------- section 7.2) ------------------
-----------
Exchange Originator 1 or 2 N/A
S_ID
Other Special Processing:
None.
7.3.15 Request Sequence Initiative (RSI)
ELS Format:
+------+------------+------------+-----------+----------+
| Word | Bits 31û24 | Bits 23û16 | Bits 15û8 | Bits 7-0 |
+------+------------+------------+-----------+----------+
| 0 | Cmd = 0x0A | 0x00 | 0x00 | 0x00 |
+------+------------+------------+-----------+----------+
| 1 | Rsvd | Exchange Originator S_ID |
+------+------------+------------+-----------+----------+
| 2 | OX_ID | RX_ID |
+------+------------+------------+-----------+----------+
| 3-10 | Association header (may be optionally reqÆd) |
+======+============+============+===========+==========+
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Fields Requiring Translation Supplemental Data
Address Translation Type(see (type 3 only)
------------------- section 7.2) ------------------
-----------
Exchange Originator 1 or 2 N/A
S_ID
Other Special Processing:
None.
7.3.16 Third Party Process Logout (TPRLO)
TPRLO provides a mechanism for an N_PORT (third party) to remove
one or more process login sessions that exist between the
destination N_PORT and other N_PORTs specified in the command.
This command includes one or more TPRLO LOGOUT PARAMETER PAGEs,
each of which when combined with the destination N_PORT identifies
a process login to tobe terminated by the command.
Byte
Offset
+----------------------------------+
0 | LS_COMMAND | 1 Byte
+----------------------------------+
1 | PAGE LENGTH (0x10) | 1 Byte
+----------------------------------+
2 | PAYLOAD LENGTH | 2 Bytes
+----------------------------------+
4 | TPRLO LOGOUT PARAMETER PAGE 1 | 2-4 Bytes
+----------------------------------+
. | . . . . | M Bytes
. +----------------------------------+
n | TPRLO LOGOUT PARAMETER PAGE N |
+----------------------------------+
Figure 16 -- Format of TPRLO ELS
Each TPRLO parameter page contains parameters identifying one or
more image pairs and may be associated with a single FC4 protocol
type, common to all FC4 protocol types between the specified image
pair, or global to all specified image pairs. The format of an
augmented TPRLO page is shown in Figure 17. Additional information
on TPRLO can be found in [FC-FS].
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+------+------------+------------+-----------+----------+
| Word | Bits 31û24 | Bits 23û16 | Bits 15-8 | Bits 7-0 |
+------+------------+------------+-----------+----------+
| 0 | TYPE Code | TYPE CODE | |
| | or | EXTENSION | TPRLO Flags |
| | Common SVC | | |
| | Parameters | | |
+------+------------+------------+-----------+----------+
| 1 | Third Party Process Associator |
+------+------------+------------+-----------+----------+
| 2 | Responder Process Associator |
+------+------------+------------+-----------+----------+
| 3 | Reserved | Third Party Originator N_PORT ID |
+======+============+============+===========+==========+
| 4-5 | World Wide Name of Third Party Originator |
| | N_PORT |
+------+------------------------------------------------+
Figure 17 -- Format of an Augmented TPRLO Parameter Page
The TPRLO flags that affect the processing of the augmented ELS are
as follows:
Bit 12: Global Process logout. When set to one, this bit
indicates that all image pairs for all N_PORTs of the
specified FC4 protocol shall be invalidated. When the
value of this bit is one, only one logout parameter page
is permitted in the TPRLO payload.
Bit 13: Third party Originator N_PORT Validity. When set to
one, this bit indicates that word 3, bits 23-00 (Third
Party Originator N_PORT ID) are meaningful.
.
If bit 13 has a value of zero and bit 12 has a value of one in the
TPRLO flags field, then the ELS SHALL NOT be sent as an augmented
ELS.
Otherwise the originating gateway SHALL process the ELS as follows:
a) The first word of the TPRLO payload SHALL NOT be modified.
b) Each TPRLO page shall be extended by two words as shown in
Figure 17.
c) If word 0, bit 13 (Third Party Originator N_PORT I/D validity)
in the TPRLO flags field has a value of one, then the sender
shall place the world-wide port name of the fibre channel
device's N_PORT in the extension words. The N_PORT I/D SHALL be
set to 3. Otherwise, the contents of the extension words and
the Third Party Originator N_PORT ID SHALL be set to zero.
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d) The ELS originator SHALL set the AUG bit in the encapsulation
header of each augmented frame comprising the ELS (see section
6.4.1).
e) If the ELS only contains a single TPRLO parameter page, the
originator SHALL increase the frame length as necessary to
include the extended parameter page.
f) If the ELS to be augmented contains multiple TPRLO parameter
pages, the FC frames created to contain the augmented ELS
payload SHALL NOT exceed the maximum frame size that can be
accepted by the destination N_PORT.
Each frame SHALL contain an integer number of extended TPRLO
parameter pages. The maximum number of extended TPRLO parameter
pages in a frame SHALL be limited to the number that can be
held without exceeding the above upper limit. New frames
resulting from the extension of the TPRLO pages to include the
supplemental data shall be created by extending the SEQ_CNT.
The SEQ_ID SHALL NOT be modified.
The gateway receiving the augmented TPRLO ELS SHALL generate ELS
frames to be sent to the destination N_PORT by copying word 0 of
the ELS payload and processing each augmented parameter page as
follows:
a) If word 0, bit 13 has a value of one, create a parameter page by
copying words 0 through 2 of the augmented parameter page. The
Third Party Originator N_PORT I/D shall be generated by
referencing the supplemental data as described in section 7.2.
b) If word 0, bit 13 has a value of zero, create a parameter page
by copying words 0 through 3 of the augmented parameter page.
The size of each frame to be sent to the destination N_PORT MUST
NOT exceed the maximum frame size that the destination N_PORT can
accept. The sequence identifier in each frame header SHALL be
copied from the augmented ELS and the sequence count shall be
monotonically increasing.
7.4 FLOGI Service Parameters Supported by an iFCP Gateway
The FLOGI ELS is issued by an N_PORT that wishes to access the
fabric transport services.
The format of the FLOGI request and FLOGI ACC payloads are
identical to the PLOGI request and ACC payloads described in
section 7.3.7. The figure in that section is duplicated below for
convenience.
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Byte
Offset
+----------------------------------+
0 | LS_COMMAND | 4 Bytes
+----------------------------------+
4 | COMMON SERVICE PARAMETERS | 16 Bytes
+----------------------------------+
20 | PORT NAME | 8 Bytes
+----------------------------------+
28 | NODE NAME | 8 Bytes
+----------------------------------+
36 | CLASS 1 SERVICE PARAMETERS | 16 Bytes
+----------------------------------+
52 | CLASS 2 SERVICE PARAMETERS | 16 Bytes
+----------------------------------+
68 | CLASS 3 SERVICE PARAMETERS | 16 Bytes
+----------------------------------+
86 | CLASS 4 SERVICE PARAMETERS | 16 Bytes
+----------------------------------+
102 | VENDOR VERSION LEVEL | 16 Bytes
+----------------------------------+
Figure 18 -- FLOGI Request and ACC Payload Format
A full description of each parameter is given in [FC-FS].
This section tabulates the service parameters supported by a fabric
port attached to an iFCP gateway.
FC service parameters are carried in the payload of a PLOGI or
FLOGI extended link service request having the following format:
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+-----------------------------------------+---------------+
| | Fabric Login |
| Service Parameter | Class |
| +---+---+---+---+
| | 1 | 2 | 3 | 4 |
+-----------------------------------------+---+---+---+---+
| Class Validity | X | a | a | n |
+-----------------------------------------+---+---+---+---+
| Service Options | |
+-----------------------------------------+---+---+---+---+
| Intermix Mode | n | n | n | n |
+-----------------------------------------+---+---+---+---+
| Stacked Connect-Requests | n | n | n | n |
+-----------------------------------------+---+---+---+---+
| Sequential Delivery | n | M | M | n |
+-----------------------------------------+---+---+---+---+
| Dedicated Simplex | n | n | n | n |
+-----------------------------------------+---+---+---+---+
| Camp on | n | n | n | n |
+-----------------------------------------+---+---+---+---+
| Buffered Class 1 | n | n | n | n |
+-----------------------------------------+---+---+---+---+
| Priority | n | a | a | n |
+-----------------------------------------+---+---+---+---+
| Initiator Control | |
+-----------------------------------------+---+---+---+---+
| Initial Responder Process Associator | n | n | n | n |
+-----------------------------------------+---+---+---+---+
| ACK_0 capable | n | n | n | n |
+-----------------------------------------+---+---+---+---+
| ACK generation assistance | n | n | n | n |
+-----------------------------------------+---+---+---+---+
| Clock synchronization ELS capable | n | n | n | n |
+-----------------------------------------+---+---+---+---+
| Recipient Control | |
+-----------------------------------------+---+---+---+---+
| ACK_0 capable | n | n | n | n |
+-----------------------------------------+---+---+---+---+
| X_ID interlock | n | n | n | n |
+-----------------------------------------+---+---+---+---+
| Error policy support | n | n | n | n |
+-----------------------------------------+---+---+---+---+
| Categories per sequence | n | n | n | n |
+-----------------------------------------+---+---+---+---+
| Clock synchronization ELS capable | n | n | n | n |
+-----------------------------------------+---+---+---+---+
| Reserved - Fabric Specific | n | y | y | n |
+-----------------------------------------+---+---+---+---+
Notes:
1) "y" indicates a parameter that applies to an iFCP gateway
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2) "n" indicates the parameter is not applicable to an iFCP
gateway
3) "M" indicates a parameter that MUST be supported by an
iFCP gateway
4) "X" indicates a parameter that MUST NOT be supported by an
iFCP gateway
8. TCP Session Control Messages
TCP session control messages are used to create and manage an iFCP
session as described in section 6.2.2. They are passed between peer
iFCP Portals, and are only processed within the iFCP layer.
The message format is based on the extended link service message
template shown below.
Word
31<Bits>24 23<---------------Bits------------------------->0
+----------+------------------------------------------------+
0| R_CTL | D_ID [0x00 00 00] |
|[Req = 22]| [Destination of extended link Service request] |
|[Rep = 23]| |
+----------+------------------------------------------------+
1| CS_CTL | S_ID [0x00 00 00] |
| [0x0] | [Source of extended link service request] |
+----------+------------------------------------------------+
2|TYPE [0x1]| F_CTL [0] |
+----------+------------------+-----------------------------+
3|SEQ_ID | DF_CTL [0x00] | SEQ_CNT [0x00] |
|[0x0] | | |
+----------+------------------+-----------------------------+
4| OX_ID [0x0000] | RX_ID_[0x0000] |
+-----------------------------+-----------------------------+
5| Parameter |
| [ 00 00 00 00 ] |
+-----------------------------------------------------------+
6| LS_COMMAND |
| [Session Control Command Code] |
+-----------------------------------------------------------+
7| |
.| Additional Session Control Parameters |
.| ( if any ) |
n| |
+===========================================================+
n| Fibre Channel CRC |
+| |
1+===========================================================+
Figure 19 -- Format of Session Control Message
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The LS_COMMAND value for the response remains the same as that used
for the request.
The session control ELS frame is terminated with a Fibre Channel
CRC.
The encapsulation header for the link Service frame carrying a TCP
ELS message SHALL be set as follows:
Encapsulation Header Fields:
LS_COMMAND 0
iFCP Flags SES = 1
TRN = 0
AUG = 0
SOF code SOFi3 encoding (0x2E)
EOF code EOFt encoding (0x42)
Time Stamp Integer 0,0
and Fraction fields
The SOF and EOF delimiter words SHALL be set based on the SOF and
EOF codes specified above.
The following lists the session control messages and their
corresponding LS_COMMAND values.
Request LS_COMMAND Short Name iFCP Support
------- ---------- ---------- -----------
Connection Bind 0xE0 CBIND REQUIRED
Unbind Connection 0xE4 UNBIND REQUIRED
8.1 Connection Bind (CBIND)
As described in section 6.2.2.1, the CBIND message and response are
used to bind an N_PORT login session to a specific TCP
connectionand establish iFCP session. In the CBIND request
message, the source and destination N_Ports are identified by the
N_PORT network address (iFCP portal address and N_PORT ID).
The following shows the format of the CBIND request.
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+------+------------+------------+-----------+----------+
| Word | Byte 0 | Byte 1 | Byte 2 | Byte 3 |
+------+------------+------------+-----------+----------+
| 0 | Cmd = 0xE0 | 0x00 | 0x00 | 0x00 |
+------+------------+------------+-----------+----------+
| 1 | Reserved | Addr Mode | iFCP Ver |
+------+-------------------------+-----------+----------+
| 2 | User Info |
+------+------------+------------+-----------+----------+
| 3 | |
+------+ SOURCE PORT NAME |
| 4 | |
+------+------------------------------------------------+
| 5 | |
+------+ DESTINATION PORT NAME |
| 6 | |
+------+------------------------------------------------+
Addr Mode - The address translation mode of the originating
gateway. 0 = Address Translation mode, 1 = Address Transparent
mode.
iFCP Ver - iFCP version number. SHALL be set to 1.
USER INFO - Contains any data desired by the requester. This info
MUST be echoed by the recipient in the CBIND response message.
SOURCE PORT NAME - Contains the originating N_PORT's World Wide
Port Name (WWPN).
DESTINATION PORT NAME - Contains the destination N_PORT's World
Wide Port Name (WWPN).
The following shows the format of the CBIND response.
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+------+------------+------------+-----------+----------+
| Word | Byte 0 | Byte 1 | Byte 2 | Byte 3 |
+------+------------+------------+-----------+----------+
| 0 | Cmd = 0xE0 | 0x00 | 0x00 | 0x00 |
+------+------------+------------+-----------+----------+
| 1 | Reserved | Addr Mode | iFCP Ver |
+------+-------------------------+-----------+----------+
| 2 | User Info |
+------+------------+------------+-----------+----------+
| 3 | |
+------+ SOURCE PORT NAME |
| 4 | |
+------+------------------------------------------------+
| 5 | |
+------+ DESTINATION PORT NAME |
| 6 | |
+------+-------------------------+----------------------+
| 7 | Reserved | CBIND Status |
+------+-------------------------+----------------------+
| 8 | Reserved | CONNECTION HANDLE |
+------+-------------------------+----------------------+
Total Length = 32
Addr Mode - The address translation mode of the responding
gateway. 0 = Address Translation mode, 1 = Address Transparent
mode.
iFCP Ver - iFCP version number of the responding gateway. SHALL be
set to 1.
USER INFO - Contains the same value received in the USER INFO field
of the CBIND request message.
DESTINATION PORT NAME - Contains the destination N_PORT's World
Wide Port Name (WWPN).
CBIND STATUS - Indicates success or failure of the CBIND request.
CBIND values are shown below.
Value Description
----- -----------
0 Successful û No other status
1 û 15 Reserved
16 Failed û Unspecified Reason
17 Failed û No such device
18 Failed û N_PORT session already exists
19 Failed û Lack of resources
20 Failed - Incompatible address translation mode
21 Failed - Incorrect protocol version number
Others Reserved
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CONNECTION HANDLE (CHANDLE) - Contains a value assigned by the iFCP
Portal to identify the connection.
8.2 Unbind Connection (UNBIND)
UNBIND is used to release a bound TCP connection and return it to
the pool of unbound TCP connections. This message is transmitted
in the connection that is to be unbound.
The following is the format of the UNBIND request message.
+------+------------+------------+-----------+----------+
| Word | Byte 0 | Byte 1 | Byte 2 | Byte 3 |
+------+------------+------------+-----------+----------+
| 0 | Cmd = 0xE4 | 0x00 | 0x00 | 0x00 |
+------+------------+------------+-----------+----------+
| 1 | User Info |
+------+------------+------------+-----------+----------+
| 2 | Reserved | Connection Handle |
+------+------------+------------+----------------------+
| 3 | Reserved |
+------+------------+------------+-----------+----------+
| 4 | Reserved |
+------+------------+------------+-----------+----------+
CONNECTION HANDLE (CHANDLE) - Contains a value assigned by the iFCP
Portal to identify the connection
The following shows the format of the UNBIND response message.
+------+------------+------------+-----------+----------+
| Word | Byte 0 | Byte 1 | Byte 2 | Byte 3 |
+------+------------+------------+-----------+----------+
| 0 | Cmd = 0xE4 | 0x00 | 0x00 | 0x00 |
+------+------------+------------+-----------+----------+
| 1 | User Info |
+------+------------+------------+-----------+----------+
| 2 | Reserved | Connection Handle |
+------+------------+------------+-----------+----------+
| 3 | Reserved |
+------+------------+------------+-----------+----------+
| 4 | Reserved |
+------+------------+------------+-----------+----------+
| 5 | Reserved | UNBIND Status |
+------+------------+------------+-----------+----------+
UNBIND STATUS - Indicates the success or failure of the UNBIND
request.
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Value Description
----- -----------
0 Successful û No other status
1 û 15 Reserved
16 Failed û Unspecified Reason
17 Failed û No such device
18 Failed û Connection ID Invalid
Others Reserved
CONNECTION HANDLE (CHANDLE) - Contains a value assigned by the iFCP
Portal to identify the unbound connection.
9. iFCP Error Detection
9.1 Overview
[FC-FS] defines error detection and recovery procedures. These
Fibre Channel-defined mechanisms continue to be available in the
iFCP environment.
9.2 Stale Frame Prevention
Recovery from Fibre Channel protocol error conditions requires that
frames associated with a failed or aborted Exchange drain from the
fabric before Exchange resources can be safely reused.
Since a Fibre Channel fabric may not preserve frame order, there is
no deterministic way to purge such frames. Instead, the fabric
guarantees that frame the lifetime will not exceed a specific limit
(R_A_TOV).
R_A_TOV is defined in [FC-FS] as "the maximum transit time within a
fabric to guarantee that a lost frame will never emerge from the
fabric". For example, a value of 2 x R_A_TOV is the minimum time
that the originator of an ELS request or FC4 ELS request must wait
for the response to that request. The Fibre Channel default value
for R_A_TOV is 10 seconds.
The iFCP fabric MAY actively enforce limits on R_A_TOV as described
in section 9.2.1.
9.2.1 Enforcing R_A_TOV Limits
The R_A_TOV limit on frame lifetimes MAY be enforced by means of
the time stamp in the encapsulation header (see section 6.4.1) as
described in this section.
The budget for R_A_TOV SHOULD include allowances for the
propagation delay through the gateway regions of the sending and
receiving N_PORTs plus the propagation delay through the IP
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network. This latter component is referred to in this
specification as IP_TOV.
If enforced by a gateway, IP_TOV SHOULD be set well below the value
of R_A_TOV specified for the iFCP fabric and SHOULD be stored in
the iSNS server. IP_TOV SHOULD be set to 50 percent of R_A_TOV.
The following paragraphs describe the requirements for
synchronizing gateway time bases and the rules for measuring and
enforcing propagation delay limits.
The protocol for synchronizing a gateway time base is SNTP
[RFC2030]. In order to insure that all gateways are time-aligned, a
gateway SHOULD obtain the address of an SNTP-compatible time server
via an iSNS query. If multiple time server addresses are returned
by the query, the servers must be synchronized and the gateway may
use any server in the list. Alternatively, the server may return a
multicast group address in support of operation in Anycast mode.
Implementation of Anycast mode is as specified in RFC 2030,
including the precautions defined in that document. Multicast mode
SHOULD NOT be used.
An SNTP server may use any one of the time reference sources listed
in RFC 2030. The resolution of the time reference MUST be 125
milliseconds or better.
With regard to the time base, the gateway is in either the
Synchronized or Unsynchronized state. When in the Unsynchronized
state, the gateway SHALL:
a) Set the time stamp field to 0,0 for all outgoing frames
b) Ignore the time stamp field for all incoming frames.
When in the synchronized state, the gateway SHALL
a) Set the time stamp field for each outgoing frame in accordance
with the gateway's internal time base
b) Check the time stamp field of each incoming frame, following
validation of the encapsulation header CRC as described in
section 6.4.4.
c) If the incoming frame has a time stamp of 0,0, the receiving
gateway SHALL NOT test the frame to determine if it is stale.
d) If the incoming frame has a non-zero time stamp, the receiving
gateway SHALL compute the absolute value of the time in flight
and SHALL compare it against the value of IP_TOV specified for
the IP fabric.
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e) If the result in step (d) exceeds IP_TOV, the encapsulated
frame shall be discarded. Otherwise, the frame shall be de-
encapsulated as described in section 6.4.4.
A gateway SHALL enter the Synchronized state upon receiving a
successful response to an SNTP query.
A gateway shall enter the Unsynchronized state:
a) Upon power up and before successful completion of an SNTP query
b) Whenever the gateway looses contact with the SNTP server such
that the gateway's time base may no longer be in alignment with
that of the SNTP server. The criterion for determining loss of
contact is implementation specific.
The gateway response to loss of synchronization is implementation-
specific. The gateway MAY choose to abort all N_PORT login sessions
with all remote gateways.
10. Fabric Services Supported by an iFCP implementation
An iFCP gateway implementation MUST support the following fabric
services:
N_PORT ID Value Description Section
--------------- ----------- -------
0xFF-FF-FE F_PORT Server 10.1
0xFF-FF-FD Fabric Controller 10.2
0xFF-FF-FC Directory/Name Server 10.3
In addition, an iFCP gateway MAY support the FC broadcast server
functionality described in section 10.4.
10.1 F_PORT Server
The F_PORT server SHALL support the FLOGI ELS as described in
section 7.4 as well as the following ELSs specified in [FC-FS]:
a) Request for fabric service parameters (FDISC),
b) Request for the link error status (LESB),
c) Read Fabric Timeout Values (RTV).
10.2 Fabric Controller
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The Fabric Controller SHALL support the following ELSs as specified
in [FC-FS]:
a) State Change Notification (SCN),
b) Registered State Change Notification (RSCN),
c) State Change Registration (SCR).
10.3 Directory/Name Server
The Directory/Name server provides a registration service allowing
an N_PORT to record or query the database for information about
other N_PORTs. The services are defined in [FC-GS3]. The queries
are issued as FC-4 transactions using the FC-CT command transport
protocol specified in [FC-GS3].
In iFCP, name server requests are translated to the iSNS queries
defined in [ISNS]. The definitions of name server objects are
specified in [FC-GS3].
The name server SHALL support record and query operations for
directory subtype 0x02 (Name Server) and 0x03 (IP Address Server)
and MAY support the FC-4 specific services as defined in [FC-GS3].
10.4 iFCP Support for the FC Broadcast Service
In Fibre Channel, frames are broadcast by addressing them to the
broadcast server at well-known address 0xFF-FF-FF. The broadcast
server then replicates and delivers the frame to each attached
N_PORT in all zones to which the originating device belongs. Only
class 3 (datagram) service is supported.
In an iFCP system, outgoing frames to be broadcast are directed to
the gateway-resident broadcast server by locally attached N_PORTs.
The broadcast server then redistributes such frames as follows:
a) One copy is sent to each locally attached N_PORT in the same
discovery domain as the originator.
b) One copy is sent to the broadcast server in each remote gateway
via a UDP datagram. The D_ID field is set to the well-known
address of the FC broadcast server. The datagram encapsulation
format is identical to the iFCP encapsulation format described
in section 6.4. The UDP datagram SHALL be sent to the IANA-
assigned port number at the specified IP address. The DF bit
SHALL be set to 1 in the IP header to prohibit IP fragmentation
(see [RFC791]).
On receiving an iFCP broadcast datagram via UDP, the broadcast
server SHALL:
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a) Validate the encapsulation header as described in section 6.4.3.
If the header is invalid, the frame SHALL be discarded.
b) Convert the S_ID N_PORT address in the frame to an N_PORT alias
as described in section 5.3.2, if address translation mode is in
effect.
c) If the AUG bit is set in the iFCP flags field, perform any
special processing required by the ELS, including translation of
any addresses in the payload.
d) Replicate and redistribute the frame to all locally attached
N_PORTs in the discovery domain of the sender.
If no broadcast server is implemented, the receiving gateway SHALL
discard an incoming broadcast frame from a remote gateway.
Broadcast frames received from locally attached N_PORTs shall be
processed as specified in[FC-GS3].
11. Security
11.1 Overview
As with any other IP-based network, an iFCP storage network has
security issues which must be addressed with the appropriate
security policies and enforcement resources. There are various
levels of security paradigms which when applied appropriately to an
iFCP network can provide sufficient levels of security, including
data integrity, authentication, and privacy, depending on user
needs.
11.2 Physical Security
Most existing SCSI and Fibre Channel interconnections are deployed
in private, physically isolated environments where hostile entities
are not provided access to the SCSI and Fibre Channel
interconnects. This is the most basic security mechanism, and may
be a sufficient model in some cases for an iFCP network.
11.3 Controlling Access
A second level of security is the use of zoning. Zoning specifies
which devices are allowed to communicate, and is similar in concept
to VLAN (Virtual Local Area Network) technology. Zoning
information is maintained in the iSNS name server specified in
[ISNS].
11.4 Authentication and Encryption
Where additional levels of data integrity and privacy are required
for iFCP, existing IPSec specifications can be applied to iFCP.
Because IPSec is a layer-3 technology and has no knowledge of TCP,
UDP, or higher-level protocols such as iFCP and FCP, it can be
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applied transparently to iFCP. The following IETF documents
describe the operational framework and automatic keying mechanisms
for IPSec.
[RFC2401] Security Architecture for the Internet Protocol
[RFC2402] IP Authentication Header
[RFC2406] IP Encapsulating Security Payload
[RFC2407] The Internet IP Security Domain of Interpretation for
ISAKMP
[RFC2408] Internet Security Association and Key Management
Protocol (ISAKMP)
[RFC2409] The Internet Key Exchange (IKE)
11.5 Storage Firewalls
Firewalls are a common and proven methodology for securing access
to IP-based networks, and they can be appropriate for use in IP-
based storage networks as well. A firewall is a choke point
through which all transit traffic must transit in order to pass
between two separate networks. Since all iFCP traffic uses a well-
known IANA-assigned TCP port number, it can easily be recognized
and inspected.
Access to storage resources can be secured by setting up a single
gateway through which all outside non-secured traffic must pass
through in order to access resources in the storage network. Such
a firewall can be a proxy host operating at the session or
application layer, requiring authentication before allowing traffic
to pass. It can also be a stateful inspection gateway which
understands the iFCP protocol, and can passively inspect and
discover security threats as they transit the gateway. A third
option is to use a standard router access control list to filter
authorized traffic based upon static parameters such as IP
addresses and TCP port numbers.
12. Quality of Service Considerations
12.1 Minimal requirements
Conforming iFCP protocol implementations SHALL correctly
communicate gateway-to-gateway even across one or more intervening
best-effort IP regions. The timings with which such gateway-to
gateway communication is performed, however, will greatly depend
upon BER, packet losses, latency, and jitter experienced throughout
the best-effort IP regions. The higher these parameters, the higher
will be the gap measured between iFCP observed behaviors and
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baseline iFCP behaviors (i.e., as produced by two iFCP gateways
directly connected to one another).
12.2 High-assurance
It is expected that many iFCP deployments will benefit from a high
degree of assurance on the behaviors of the intervening IP regions,
with resulting high-assurance on the overall end-to-end path, as
directly experienced by Fibre Channel applications. Such assurance
on the IP behaviors stems from the intervening IP regions
supporting standard Quality-of-Service (QoS) techniques, fully
complementary to iFCP, such as:
a) Congestion avoidance by over-provisioning of the network
b) Integrated Services [RFC1633] QoS
c) .Differentiated Services [RFC2475] QoS
d) .Multi-Protocol Label Switching [RFC3031]
In the most general definition, two iFCP gateways are separated by
one or more independently managed IP regions, some of which
implement some of the QoS solutions mentioned above. The IP regions
with these QoS solutions are said to support Service Level
Agreements (SLAs). Such agreements finalize requirements on network
parameters such as bandwidth, loss, latency, jitter, burst length.
The requirements may be expressed in absolute or relative terms,
and apply to a unidirectional flow of packets. Depending on the QoS
techniques available, the dynamic stipulation of a SLA may require
the iFCP gateway to interact with network ancillary functions such
admission control and bandwidth brokers (with RSVP or other
signalling protocols that an IP region may accept).
Due to the fact that Fibre Channel Class 2 and Class 3 do not
currently support fractional bandwidth guarantees, and that iFCP is
committed to supporting Fibre Channel semantics, it is impossible
for an iFCP gateway to autonomously infer bandwidth requirements
from streaming Fibre Channel traffic. Rather, the requirements on
bandwidth or other network parameters need to be injected out-of-
band into a iFCP gateway (or the node that will actually negotiate
the SLA on the gateway's behalf) through mechanisms outside the
scope of this specification (e.g., through a management interface
into the iFCP gateway).
The administrator of a iFCP gateway MAY thus stipulate a Service
Level Agreement with the local IP region for one, several, or all
of an iFCP gateway's TCP sessions used by iFCP. Alternately, this
responsibility may be delegated to a node downstream. Since one TCP
connection is dedicated to each N_PORT login session , an
individual N_PORT to N_PORT flow can enjoy a customized SLA.
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To render the best emulation of Fibre Channel possible over IP, it
is anticipated that typical SLAs will specify a fixed amount of
bandwidth, null losses, and, to a lesser degree of relevance, low
latency, and low jitter. For example, an IP region using DiffServ
QoS may support SLAs of this nature by applying EF DSCPs to the
iFCP traffic. For the same SLA, another IP region might as well use
a different DSCP or different QoS techniques alltogether. The way
different QoS techniques are re-mapped at the edge of different
intervening IP regions is beyond the scope of this specification.
[00-603] describes a proposal to add fractional bandwidth
guarantees to Class 2 and 3 (migrating it from Class 4). In such
proposal, the bandwidth parameters would surface in the FLOGI
request and accept, and PLOGI request and accept. In this case, it
will become possible for an iFCP gateway to trap this information
and autonomously remap it onto the SLA negotiation mechanism
required by the local IP region, without resorting to out-of-band
QoS management. Such an in-band QoS mechanism would result in true
end-to-end provisioning of network resources. Forthcoming revisions
of this iFCP specification will build upon this new opportunity.
13. Author's Addresses
Charles Monia Franco Travostino
Rod Mullendore Director, Content
Josh Tseng Internetworking Lab,
Nishan Systems Victor Firoiu
3850 North First Street
San Jose, CA 95134 Nortel Networks
Phone: 408-519-3986 3 Federal Street
Email: Billerica, MA 01821
cmonia@nishansystems.com Phone: 978-288-7708
Email:
travos@nortelnetworks.com
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David Robinson Wayland Jeong
Sun Microsystems Troika Networks
Senior Staff Engineer Vice President, Hardware
M/S UNWK16-301 Engineering
901 San Antonio Road 2829 Townsgate Road Suite
Palo Alto, CA 94303-4900 200
Phone: 510-936-2337 Westlake Village, CA 91361
Email: Phone: 805-370-2614
David.Robinson@sun.com Email:
wayland@troikanetworks.com
Rory Bolt Paul Rutherford
Quantum/ATL ADIC
Director, System Design Vice President, Technology &
101 Innovation Drive Software
Irvine, CA 92612 1143 Willows Road N.E.
Phone: 949-856-7760 P.O. Box 97057
Email: rbolt@atlp.com Redmond, WA 98073-9757
Phone: 425-881-8004
Email:
paul.rutherford@adic.com
Mark Edwards
Senior Systems Architect
Eurologic Development, Ltd.
4th Floor, Howard House
Queens Ave, UK. BS8 1SD
Phone: +44 (0)117 930 9600
Email:
medwards@eurologic.com
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Appendix A
A. iFCP Support for Fibre Channel Link Services
For reference purposes, this appendix enumerates all the Fibre
Channel link services and the manner in which each shall be
processed by an iFCP implementation. The iFCP processing policies
are defined in section 7.
A.1 Basic Link Services
The basic link services are shown in the following table.
Basic Link Services
Name Description iFCP Policy
---- ----------- ----------
ABTS Abort Sequence Transparent
BA_ACC Basic Accept Transparent
BA_RJT Basic Reject Transparent
NOP No Operation Transparent
PRMT Preempted Rejected
(Applies to
Class 1 only)
RMC Remove Connection Rejected
(Applies to
Class 1 only)
A.2 Link Services Processed Transparently
The following link service requests and responses MUST be processed
transparently as defined in section 7.
ELSs Processed Transparently
Name Description
---- -----------
ACC Accept
ADVC Advise Credit
CSR Clock Synchronization Request
CSU Clock Synchronization Update
ECHO Echo
ESTC Estimate Credit
ESTS Establish Streaming
FACT Fabric Activate Alias_ID
FAN Fabric Address Notification
FDACT Fabric Deactivate Alias_ID
FDISC Discover F_Port Service
Parameters
FLOGI F_Port Login
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GAID Get Alias_ID
LCLM Login Control List Management
LINIT Loop Initialize
LIRR Link Incident Record
Registration
LPC Loop Port Control
LS_RJT Link Service Reject
LSTS Loop Status
NACT N_Port Activate Alias_ID
NDACT N_Port Deactivate Alias_ID
PDISC Discover N_Port Service
Parameters
PRLI Process Login
PRLO Process Logout
QoSR Quality of Service Request
RCS Read Connection Status
RLIR Registered Link Incident Report
RNC Report Node Capability
RNFT Report Node FC-4 Types
RNID Request Node Identification
Data
RPL Read Port List
RPS Read Port Status Block
RPSC Report Port Speed Capabilities
RSCN Registered State Change
Notification
RTIN Request Topology Information
RTV Read Timeout Value
RVCS Read Virtual Circuit Status
SBRP Set Bit-error Reporting
Parameters
SCL Scan Remote Loop
SCN State Change Notification
SCR State Change Registration
TEST Test
TPLS Test Process Login State
A.3 Augmented Link Services
The following extended link services are augmented with additional
data and processed by the iFCP implementation as described in the
referenced section listed in the table.
Augmented Link Services
Name Description Section
---- ----------- -------
ABTX Abort Exchange 7.3.1
ADISC Discover Address 7.3.2
ADISC Discover Address Accept 7.3.3
ACC
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FARP- Fibre Channel Address 7.3.4
REPLY Resolution Protocol Reply
FARP-REQ Fibre Channel Address 7.3.5
Resolution Protocol Request
LOGO N_PORT Logout 7.3.6
PLOGI Port Login 7.3.7
REC Read Exchange Concise 7.3.8
REC ACC Read Exchange Concise Accept 7.3.9
RES Read Exchange Status Block 7.3.10
RES ACC Read Exchange Status Block 7.3.11
Accept
RLS Read Link Error Status Block 7.3.12
RRQ Reinstate Recovery Qualifier 7.3.14
RSI Request Sequence Initiative 7.3.15
RSS Read Sequence Status Block 7.3.13
TPRLO Third Party Process Logout 7.3.16
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Appendix B
B. Implementing IP to FC Connectivity
This appendix describes an optional method for allowing FC devices
locally connected to an iFCP gateway to internetwork with IP
devices.
Fibre Channel devices may access IP-based protocol stacks and IP-
connected network devices by implementing support for the ARP and
IP to FC encapsulation capabilities specified in RFC 2625
[RFC2625]. In order for such an FC device to access a node anywhere
in the IP network, the FC device must have access to the
appropriate bridging or routing device. This appendix describes an
architecture for providing such connectivity through a Fibre
Channel to IP routing element implemented in an iFCP gateway.
An IP-to-FC router is a multi-port-port device internal to an iFCP
gateway consisting of one N_PORT and any number of ethernet ports
as shown in the topology diagram of Figure 20.
IP to FC Router
+----+-------+
FC Subnets | | | To ethernet
+----------+ | N | R +-------------->
| Fibre | FC-encapsulated | | O | subnet
| Channel +-----------------+ P | U | .
| Device | IP Datagrams | O | T | .
| Domain | | R | E | To ethernet
+----------+ | T | R +-------------->
| | | subnet
+----+-------+
Figure 20 -- IP to FC Router Topology
A routing Fibre Channel device is indistinguishable from any other
locally-attached N_PORT in the gateway region and may be accessed
via iFCP from remotely attached N_PORTs. Such access may be
necessary when the router is the only means of reaching an
otherwise inaccessible IP subnet. A gateway MAY implement any
number of such devices.
The router directs IP datagrams to an addressed node on the
appropriate IP subnet in accordance with the implemented routing
policy. Note that all ports on the IP to FC router, including the
N_PORT connected to the Fibre Channel device domain, participate in
the IP routing algorithm. For example, a router than supports OSPF
[RFC1247], may route traffic to another IP-addressable routing
device in the Fibre Channel device domain by encapsulating OSPF
traffic in IP datagrams, which are themselves carried by iFCP-
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encapsulated Fibre Channel frames. As noted above, routing in this
manner, may be required in order to reach a subnet that is only
accessible from a single IP-to-FC router.
When necessary, the router converts IP datagrams received over one
of its ethernet ports to FC-encapsulated IP datagrams (and vice
versa) in accordance with RFC 2625 [RFC2625]. An overview of this
specification is given in the following section.
B.1 IP Over Fibre Channel
RFC 2625 specifies the elements needed to enable the
internetworking of Fibre Channel devices using an IP protocol
stacks including:
a) A Fibre Channel encapsulation of IP datagrams.
b) Support for ARP, the address resolution protocol specified by
[RFC826]
c) Use of FARP-REQ and FARP-REPLY for address resolution in a Fibre
Channel fabric (see sections 7.3.4 and 7.3.5).
This section is a schematic description of the functionality. The
reader should consult the referenced RFC for the implementation
details, including the IP datagram encapsulation format and the
details of the ARP and FARP protocols.
A Fibre Channel device that wishes to communicate using IP over
Fibre Channel must have an N_PORT with the following associated
identifiers:
a) An assigned IP address
b) An IEEE 802.3 conformant 48-bit world-wide unique port name
(WWPN) as specified in [RFC2625]. For ease in bridging a Fibre
Channel fabric to an IEEE 802.3 LAN, the WWPN is carried in the
Fibre Channel IP encapsulation and is returned in response to
ARP queries as described below.
c) A volatile, 24-bit Fibre Channel N_PORT ID.
Given the above, Fibre Channel address resolution is a two-step
process that consists of:
a) Discovering the world-wide unique port name associated with the
N_PORT's IP address
b) Translating the world wide unique identifier to an N_PORT ID.
According to RFC 2625, address resolution may be performed in
several ways, including direct lookup, name service queries and by
means of the Fibre Channel ARP and FARP protocols. An iFCP gateway
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that supports address lookup by means of name service queries SHALL
support the IP Address Server functionality defined in [FC-GS3].
In the absence of name server support, an ARP query similar to the
LAN version is performed by broadcasting an FC ARP frame via the
broadcast server as described in section 10.4 and listening for a
reply. An ARP response will contain the 48-bit world-wide unique
port name (WWPN). A FARP-REQ is then broadcast using the WWPN to
obtain an N_PORT ID and perform the N_PORT login.
B.2 Router Management and Configuration
All IP-to-FC routers implemented in an iFCP network SHOULD support
the same routing protocol.
Management of the router configuration, including the ability to
act as an ARP proxy, as defined in [RFC826], SHOULD be controllable
through the router management interface.
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Appendix C
C. Performance of The iFCP Session Model
This appendix provides a quantitative analysis of the claim that N
TCP connections carrying the traffic of all the <N_PORT, N_PORT>
sessions active between gateways provide significantly higher
aggregate average throughput than a single TCP connection carrying
the same <N_PORT, N_PORT> sessions. The analysis shows that the
difference is proportional to the square of the number of TCP
sessions, N.
This analyses is based on three fundamental assumptions: (i) all
the available bandwidth in a link is available to iFCP traffic,
(ii) the sender has always data ready to send (as is most likely
the case with a backup application), and (iii) the maximum window
size at the two TCP ends (i.e., the iFCP gateways) is set to the
link nominal capacity multiplied by the round-trip-time (so as to
have the highest chances of saturating the link yet without unduly
raising buffering requirements at the end nodes). The N^2 factor
that emerges from this analysis is essentially due to the way TCP
congestion control reacts to packet losses.
C.1 Relationship of Throughput to Packet Losses
There are several reasons for packet losses: network congestion,
link errors and network errors. Network congestion is pervasive in
current IP networks, where the only way to control congestion is
through dropping packets. Techniques for loss prevention, such as
traffic engineering, admission control and bandwidth reservation,
are not widely deployed and hence are not a factor in the behavior
of existing networks.
Even in a perfectly engineered network, link errors occur. Assuming
a link error rate equal to that specified for Fibre Channel (10^-
12) and a 10Gb/s link, there is one error every 100 seconds.
Network errors also occur with significant frequency in IP
networks. Jonathan Stone and Craig Partridge recently reported in
[PART00] that network errors caught by the TCP checksum occur with
significant frequency. Between one packet in 1100 and one in 32000
have errors which get past the link CRC and are detected by the
TCP/IP checksum.
TCP throughput is impacted by each packet loss. Following TCP's
congestion control algorithm (supported by the Tahoe, Reno, New-
Reno, and SACK implementations (see [RFC2018] and [RFC2883]), each
packet loss results in the TCP sender's congestion window being
reduced to half of its current value, and therefore (assuming
constant Round Trip Time), TCP's throughput is halved. After that,
the window increases by roughly one packet every two Round Trip
Times (assuming the widely-used Delayed-Acknowledgement algorithm).
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The temporary decrease in TCP's rate translates into a missed
opportunity to transmit a given amount of data. As we show in the
following Background section, for N storage connections sharing an
IP "pipe" of rate E, the amount of data missing the opportunity to
be transmitted due to a packet loss is:
D(N) = E^2/(N^2)*RTT^2/(256*M)
where RTT = Round Trip Time, M = packet size.
For example, for a set of N=100 connections totaling E=10Gb/s,
RTT=10ms, M=1500B, the data not transmitted in time due to a packet
loss is D(N)=2.6MB. For the same set transported over one TCP
session, the data not sent in time is D(1)= 26GB, a 10,000 fold
increase. The time interval for TCP to recover its sending rate to
its initial value after a packet loss is I(N)= 0.833 seconds in the
case N TCP connections, and I(1)=83.3seconds in the case of a
single TCP connection. Observe that in the latter case, the time to
recover its rate, I(1)=83.3s, is of the same order of magnitude as
the time between two packet losses due exclusively to a link Bit
Error Rate of 10^-12. In other words, a packet loss occurs almost
immediately after TCP has recovered its rate.
This means that a single TCP connection delivers on average about
3/4 of the required 10Gb/s rate, since 1/4 of the rate is lost
during the time the TCP rate is increasing linearly from 1/2 to
full rate. (More precisely, the effective rate is 8.27Gb/s because
1/4 of the rate is lost during 83.3s, and the time between two
errors is now 120.825s due to a decreased sending rate). By
comparison, N TCP connections deliver approximately 9.99979Gb/s
(i.e., lost 1/4 of one TCP full rate of 100Mb/s during 0.833s out
of a 100s interval).
If the impact of TCP checksum errors is also considered, the TCP
sending rate is limited to an average of (8M/RTT)sqrt(3/4p), where
p is the probability of packet loss (see [PADHYE00] for details).
For M=1500, RTT=10ms and p=1/32000, TCP throughput is about
240Mb/s. For p=1/1100, maximum TCP throughput is 34.4Mb/s.
Therefore, to fill a 10Gb/s line, about 42 simultaneous TCP flows
are required (in the case where p=1/32000) or 291 TCP flows (in the
case where p=1/1100).
Practically, for these reasons the iFCP protocol supports
combinations of M <N_PORT, N_PORT> tuples using N TCP connections,
with M, N >= 1, and with an individual <N_PORT, N_PORT> tuple
using at most one TCP connection (thus M >= N).
C.2 Background.
For a TCP session to sustain a rate of C bits/second, the TCP's
maximum congestion window W (measured in number of packets) has to
be at least W0=RTT*C/(8*M) where RTT = Round Trip Time in seconds,
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M = packet size in Bytes. The following analyses assumes W=W0.
Later, the problems with the alternative W>W0 are discussed.
The time needed by the TCP sender to recover from a single packet
loss and have its sending rate reach the previous C value is
I = 2*RTT*W/2 = RTT*W = RTT^2*C/(8*M).
The total amount of data (in Bytes) missing the opportunity to be
transmitted in this time interval I is:
D = C/8*I/4 = C^2*RTT^2/(256*M)
Consider a set of <N_PORT, N_PORT> tuples sharing an IP "pipe" of
rate E to be transported in N TCP sessions. Assuming all
connections are processed equally, each TCP session sends at a rate
of E/N. One packet loss impacts only one TCP session, and thus, the
total amount of data missing the opportunity to be transmitted due
to a packet loss is
D(N) = E^2/(N^2)*RTT^2/(256*M).
On the other hand, if the same set of <N_PORT, N_PORT> tuples
sharing an IP "pipe" of rate E is transported in one TCP session
only, the total amount of data losing the opportunity to be
transmitted due to a packet loss is
D(1) = E^2*RTT^2/(256*M) = D(N)*N^2.
The impact of packet losses on the single-TCP solution can be
reduced by configuring the maximum congestion window to be larger
than the bandwidth*delay product, W>W0. But in this case, only W0
packets can be in transit on the line, while the rest (up to the
current window size) need to be stored in a queue at the line's
ingress. In order to provide full line rate utilization assuming
periodic losses, the maximum congestion window should be at least
2*W0, due to TCP's congestion
Monia et-al. Standards Track [Page 80]
iFCP Revision 4 August 2001
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Monia et-al. Standards Track [Page 81]
iFCP Revision 4 August 2001
References
[RFC2026] Bradner, S., "The Internet Standards Process -- Revision
3", BCP 9, RFC 2026, October 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997
[FC-FS] dpANS X3.XXX-200X, "Fibre Channel Framing and Signaling
Interface", Revision 1.2, NCITS Project 1331-D, February 2001
[FC-SW2] dpANS X3.XXX-2000X, "Fibre Channel Switch Fabric -2 (FC-
SW2)", revision 5.2, NCITS Project 1305-D, May 2001
[FC-GS3] dpANS X3.XXX-200X, "Fibre Channel Generic Services -3 (FC-
GS3)", revision 7.01, NCITS Project 1356-D, November 2000
[FC-FLA] TR-20-199X, "Fibre Channel Fabric Loop Attachment (FC-
FLA)", revision 2.7, NCITS Project 1235-D, August 1997
[Kembel] Kembel, R., "Fibre Channel, A Comprehensive Introduction",
Northwest Learning Associates Inc., 2000, ISBN 0-931836-84-0
Kembel, R., "The Fibre Channel Consultant, Arbitrated Loop", Robert
W. Kembel, Northwest Learning Associates, 2000, ISBN 0-931836-84-0
[RFC793] Postel, J., "Transmission Control Protocol", RFC 793,
September, 1981
[RFC1122] Braden, S., "Requirements for Internet Hosts --
Communication Layers", RFC 1122, October 1989
[RFC896] Nagel, J., "Congestion Control in IP/TCP Networks", RFC
896, January 1984
[RFC1323] Jacobsen, V., et-al., "TCP Extensions for High
Performance", RFC 1323, May, 1992
[RFC2018] Mathis, M., et-al., TCP Selective Acknowledgement
Options", RFC 2018, October 1996
[RFC2883] Floyd, S., et-al., An Extension to the Selective
Acknowledge (SACK) Option for TCP", RFC 2883, July 2000
[RFC2581] Allman, M., et-al., "TCP Congestion Control", RFC 2581,
April 1991
Monia et-al. Standards Track [Page 82]
iFCP Revision 4 August 2001
[RFC2481] Ramakrishnan, K., "A Proposal to Add Explicit Congestion
Notification (ECN) to TCP", RFC 2481, January 1999
[ENCAP] Weber, et-al., "FC Frame Encapsulation", draft-ietf-ips-
fcencapsulation-01.txt, May 2001
[RFC2030] Mills, D., RFC 2030, "Simple Network Time Protocol (SNTP)"
Version 4, October 1996
[RFC2625] Rajagopal, M., et-al., RFC 2625, "IP and ARP over Fibre
Channel", June 1999
[ISNS] Tseng, J., et-al., "iSNS Internet Storage Name Service",
draft-ietf-ips-04.txt, July 2001
[RFC791] Postel, J., RFC 791, "The Internet Protocol", September
1981
[RFC2401] Kent, S., Atkinson, R., RFC 2401, "Security Architecture
for the Internet Protocol", November 1998
[RFC2402] Kent, S., Atkinson, R., RFC 2402, "IP Authentication
Header", November 1998
[RFC2406] Kent, S., Atkinson, R., RFC 2406, "Encapsulating Security
Protocol", November 1998
[RFC2407] Piper, D., RFC 2407, " The Internet IP Security Domain of
Interpretation for ISAKMP", November 1998
[RFC2408] Maughan, D., Schertler, M., Schneider, M., Turner, J., RFC
2408, "Internet Security Association and Key Management Protocol
(ISAKMP)" November 1998
[RFC2409] D. Harkins, D. Carrel, RFC 2409, "The Internet Key
Exchange (IKE)", November 1998
[RFC1633] Braden, R., Clark, D. and S. Shenker, "Integrated Services
in the Internet Architecture: an Overview", RFC 1633, June 1994.
[RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.
and W. Weiss, "An Architecture for Differentiated Services", RFC
2475, December 1998
[RFC3031] Rosen, E., Viswanathan, A. and Callon, R., "Multi-Protocol
Label Switching Architecture", RFC 3031, January 2001
Monia et-al. Standards Track [Page 83]
iFCP Revision 4 August 2001
[00-603] Stephens, G., Warden, G. T11/00-603, "Fractional Bandwidth,
Class 2, Class 3", October 2000
[RFC1247] Moy, J., RFC 1247 "OSPF Version 2", July 1991
[RFC2625] Rajagopal, M, et.al., RFC 2625, "IP and ARP over Fibre
Channel", June 1999
[RFC826] Plummer, D.C., RFC 826 "Ethernet Address Resolution
Protocol: Or converting network protocol addresses to 48.bit
Ethernet address for transmission on Ethernet hardware", November
1982.
[PART00] Partridge, C and J. Stone, "When The CRC and TCP Checksum
Disagree", ACM SIGCOMM, September 2000
[PADHYE00] Padhye, J, Firoiu, D, Kurose, J., "Modeling TCP Reno
Performance: A Simple Model and its Empirical Validation"
IEEE/ACM Transactions on Networking, April 2000
Monia et-al. Standards Track [Page 84]
