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12 RFC 3821
IPS Working Group M. Rajagopal, R. Bhagwat, R. A. Helland,
INTERNET-DRAFT LightSand Comm.
<draft-ietf-ips-fcovertcpip-03.txt> E. Rodriguez, Lucent Tech.
(Expires December, 2001) C. Carlson, QLogic
Category: standards-track D. Fraser, Compaq
D. Peterson, Cisco
L. Lamers, SAN Valley
V. Chau, G. Hecht, Gadzoox Networks
S. Wilson, B. Snively, R. Weber, Brocade Comm.
M. O'Donnell, A. Rijhsinghani, McDATA
S. Rupanagunta, Aarohi Comm.
V. Rangan, Rhapsody Networks
J. Nelson, K. Hirata, Vixel
M. Merhar, Pirus Networks
N. Wanamaker, Akara
Fibre Channel Over TCP/IP (FCIP)
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC 2026 [1].
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/lid-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html
Abstract
Fibre Channel Over TCP/IP (FCIP) describes mechanisms that allow the
interconnection of islands of Fibre Channel storage area networks
over IP-based networks to form a unified storage area network in a
single Fibre Channel fabric. FCIP relies on IP-based network
services to provide the connectivity between the storage area
network islands over local area networks, metropolitan area
networks, or wide area networks.
Rajagopal, et al. Standards Track [Page 1]
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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 [2].
Table Of Contents
1. Purpose, Motivation and Objectives . . . . . . . . . . . . . . . 3
2. Relationship to Fibre Channel Standards . . . . . . . . . . . . 4
2.1 Relevant Fibre Channel Standards . . . . . . . . . . . . . . . 4
2.2 This Specification and Fibre Channel Standards . . . . . . . . 4
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5. Protocol Summary . . . . . . . . . . . . . . . . . . . . . . . . 7
6. The FCIP Model . . . . . . . . . . . . . . . . . . . . . . . . . 9
6.1 FCIP Protocol Model . . . . . . . . . . . . . . . . . . . . . . 9
6.2 FCIP Link . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
6.3 FC Entity . . . . . . . . . . . . . . . . . . . . . . . . . . 10
6.4 FCIP Entity . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.5 FCIP Link Endpoint (FCIP_LEP) . . . . . . . . . . . . . . . . 12
6.6 FCIP Data Engine (FCIP_DE) . . . . . . . . . . . . . . . . . . 13
6.6.1 FCIP Encapsulation of FC Frames . . . . . . . . . . . . . . 15
6.6.2 FCIP Data Engine Error Detection and Recover . . . . . . . . 16
6.6.2.1 TCP Assistance With Error Detection and Recovery . . . . . 16
6.6.2.2 Errors in FCIP Headers and Discarding FCIP Frames . . . . 16
6.6.2.3 IP Network Transit Time Validation . . . . . . . . . . . . 17
6.6.2.4 Synchronization Failures . . . . . . . . . . . . . . . . . 17
7. TCP Connection Management . . . . . . . . . . . . . . . . . . . 18
7.1 TCP Connection Establishment . . . . . . . . . . . . . . . . . 18
7.1.1 Creating a New TCP Connection . . . . . . . . . . . . . . . 18
7.1.2 Processing TCP Connect Requests . . . . . . . . . . . . . . 19
7.2 TCP Connection Parameters . . . . . . . . . . . . . . . . . . 19
7.2.1 TCP Selective Acknowledgement Option . . . . . . . . . . . . 20
7.2.2 TCP Window Scale Option . . . . . . . . . . . . . . . . . . 20
7.2.3 IP DSCP Option . . . . . . . . . . . . . . . . . . . . . . . 20
7.2.4 Protection against sequence number wrap . . . . . . . . . . 20
7.2.5 TCP No Delay Option . . . . . . . . . . . . . . . . . . . . 20
7.2.6 TCP Acknowledgement Timeout . . . . . . . . . . . . . . . . 20
7.3 TCP Connection Considerations . . . . . . . . . . . . . . . . 20
7.4 Flow Control Mapping between TCP and FC . . . . . . . . . . . 21
8. Security . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
8.1 Considerations . . . . . . . . . . . . . . . . . . . . . . . . 22
8.2 IP Network Security Requirements . . . . . . . . . . . . . . . 22
8.3 Integrated Security . . . . . . . . . . . . . . . . . . . . . 23
8.4 External Security Gateway . . . . . . . . . . . . . . . . . . 24
8.5 Security Information Exchanged Between FC and FCIP Entities . 24
9. Performance . . . . . . . . . . . . . . . . . . . . . . . . . . 24
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9.1 Considerations . . . . . . . . . . . . . . . . . . . . . . . . 24
9.2 QoS Support . . . . . . . . . . . . . . . . . . . . . . . . . 25
9.3 QoS Information Exchanged Between FC and FCIP Entities . . . . 26
10. Dynamic Discovery of Participating FCIP Entities . . . . . . . 26
10.1 Requirements . . . . . . . . . . . . . . . . . . . . . . . . 26
10.2 Discovery Information Exchanged Between FC and FCIP Entities 26
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 27
12. Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . 28
13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 28
14. Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 29
15. Full Copyright Statement . . . . . . . . . . . . . . . . . . . 31
Annex
A Example of synchronization recovery algorithm . . . . . . . . . 31
B Relationship between FCIP and IP over FC (IPFC) . . . . . . . . 36
C FC Frame Format . . . . . . . . . . . . . . . . . . . . . . . . 36
D FCIP Requirements on an FC Entity . . . . . . . . . . . . . . . 38
E FC-BB-2 Inputs . . . . . . . . . . . . . . . . . . . . . . . . 39
1. Purpose, Motivation and Objectives
Fibre Channel (FC) is a gigabit speed networking technology
primarily used to implement Storage Area Networks (SANs). See
section 2 for information about how Fibre Channel is standardized
and the relationship of this specification to Fibre Channel standards.
This specification describes mechanisms that allow the
interconnection of islands of Fibre Channel SANs over IP Networks to
form a unified SAN in a single Fibre Channel fabric. The motivation
behind defining these interconnection mechanisms is a desire to
connect physically remote FC sites allowing remote disk access, tape
backup, and live mirroring.
Fibre Channel standards have chosen nominal distances between switch
elements that are less than the distances available in an IP
Network. Since Fibre Channel and IP Networking technologies are
compatible, it is logical to turn IP Networking for extending the
allowable distances between Fibre Channel switch elements.
The fundamental assumption made in this specification is that the
Fibre Channel traffic is carried over the IP Network in such a
manner that the Fibre Channel Fabric and all Fibre Channel devices
on the Fabric are unaware of the presence of the IP Network. This
means that the FC datagrams MUST be delivered in such time as to
comply with existing Fibre Channel specifications. The FC traffic
MAY span LANs, MANs and WANs, so long as this fundamental assumption
is adhered to.
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The objectives of this document are to:
1) specify the encapsulation and mapping of Fibre Channel (FC)
frames employing FC Frame Encapsulation [23].
2) apply the mechanism described in 1) to an FC Fabric using an IP
network as an interconnect for two or more islands in an FC
Fabric.
3) address any FC concerns arising from tunneling FC traffic over
an IP-based network, including security, data integrity (loss),
congestion, and performance. This will be accomplished by
utilizing the existing IETF-specified suite of protocols.
4) be compatible with the referenced FC standards. While new work
may be undertaken in T11 [8] to optimize and enhance FC Fabrics,
this specification requires conformance only to the referenced
FC standards.
5) be compatible with all applicable IETF standards so that the IP
Network used to extend an FC Fabric can be used concurrently for
other reasonable purposes.
2. Relationship to Fibre Channel Standards
2.1 Relevant Fibre Channel Standards
FC is standardized under American National Standard for Information
Systems of the National Committee for Information Technology
Standards (ANSI-NCITS) in its T11 technical committee. T11 has
specified a number of documents describing FC protocols, operations,
and services. T11 documents of interest to readers of this
specification include:
- FC-BB - Fibre Channel Backbone [3]
- FC-BB-2 - Fibre Channel Backbone -2 [4]
- FC-SW-2 - Fibre Channel Switch Fabric -2 [5]
- FC-FS - Fibre Channel Framing and Signaling [6]
- FC-GS-3 - Fibre Channel Generic Services -3 (FC-GS-3) [7]
Additional information regarding T11 activities is available on the
committee's web site [8].
2.2 This Specification and Fibre Channel Standards
Building a high performance device that successfully extends a FC
Fabric over an IP Network requires tight integration of FC and TCP/
IP technologies. Since these two technologies are standardized by
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multiple organizations, specifying all the requirements in one
document and getting high quality review of that document has proven
to be impossible.
Therefore, this specification addresses only the requirements
necessary to properly utilize an IP Network as a conduit for an FC
Fabric. The result is a specification for an FCIP Entity (see
section 6.4).
A product that tunnels an FC Fabric through an IP Network must
combine the FCIP Entity with an FC Entity (see section 6.3) using an
implementation specific interface. Although the requirements placed
on an FC Entity by this specification are listed in annex D, the
list here is not exhaustive. More information about FC Entities can
be found in the Fibre Channel standards and an example of an FC
Entity can be found in FC-BB-2 [4].
No attempt is being made to define the interface between an FCIP
Entity and an FC Entity at this time because doing so risks
compromising the performance and efficacy of the resulting products.
Current experience in this area is simply insufficient to guide
definition of the interface appropriately.
The objectives and motivations of this specification are not
impacted by the decision not to standardize the interface between
FCIP Entities and FC Entities because fully functional and compliant
products can be built provided they contain both an FCIP Entity and
an FC Entity. The only products that cannot be built are those that
contain only one or the other and there is no urgent need for such
products at this time.
3. Terminology
Terms needed to clarify the concepts presented in FCIP are defined
here.
FC End Node - A FC device that uses the connection services provided
by the FC Fabric.
FC Entity - The Fibre Channel specific element that combines with an
FCIP Entity to form an interface between an FC Fabric and an IP
Network (see section 6.3).
FC Fabric - An entity that interconnects various Nx_Ports (see [6])
attached to it, and is capable of routing frames using only the
destination ID information in a frame header (see annex C).
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FC Frame - The basic unit of Fibre Channel data transfer (see annex
C).
FC Receiver Portal - The access point through which an FC Frame
enters an FCIP Data Engine from the FC Entity.
FC Transmitter Portal - The access point through which a
reconstituted FC frame leaves an FCIP Data Engine to the FC Entity.
FCIP Data Engine (FCIP_DE) - The component of an FCIP Entity that
handles FC Frame encapsulation, de-encapsulation, and transmission
through a single TCP connection (see section 6.6).
FCIP Entity - The principle FCIP interface point to the IP Network
(see section 6.4).
FCIP Link - One or more TCP connections that connect one FCIP_LEP to
another (see section 6.2).
FCIP Link Endpoint (FCIP_LEP) - The component of an FCIP Entity that
handles FC Frame transmission through a single FCIP Link (see
section 6.5).
Encapsulated Frame Receiver Portal - The TCP access point through
which an FCIP encapsulated frame is received from the IP Network by
an FCIP Data Engine.
Encapsulated Frame Transmitter Portal - The TCP access point through
which an FCIP encapsulated frame is transmitted to the IP Network by
an FCIP Data Engine.
4. Open Issues
This draft is a work in progress and this section identifies areas
where the work is known to be incomplete and discusses the current
status of these efforts. This section will be removed before this
draft is considered for standardization.
- FCIP Entity Discovery - The basic principles of FCIP Entity
discovery are agreed and represented in section 5. Work on the
details of dynamic FCIP Entity discovery are incomplete (see
section 10). Work on FCIP Entity Discovery may change the way an
FCIP Entity is identified from the currently specified IP
Address usage.
- Security - In general, FCIP will follow or subset the security
mechanisms agreed for iSCSI. The basic principles of FCIP
security requirements are agreed and described in section 5.
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Section 8 contains the latest information on the details of FCIP
security. It must be noted that the association between IP
Addresses and FCIP Entities is open to changes based on yet to
be finalized decisions about security. The point at which a TCP
connection is authorized to carry data is still being debated.
- Timeout Coordination with Fibre Channel - In this revision, the
only timeout Fiber Channel timeout consideration enforced by the
FCIP Entity is R_A_TOV. All other timeout issues are the
responsibility of the FC Entity. Section 7.2.6 contains a
discussion of the TCP Acknowledge Timeout that needs to be
reviewed to determine if it is still needed.
- Performance - The discussion of performance considerations in
section 9 and particularly the quality of service discussion in
section 9.2 are known to require additional work. A particular
concern is that quality of service not be limited to using
diffserv.
5. Protocol Summary
The FCIP protocol is summarized as follows:
1) The primary function of an FCIP Entity is forwarding FC frames,
employing FC Frame Encapsulation described in [23].
2) Viewed from the IP Network perspective, all FCIP Entities are
peers and communicate using TCP/IP. Each FCIP Entity is a TCP
endpoint in the IP-based network.
3) Viewed from the FC Fabric perspective, each pair of FCIP
Entities, in combination with their associated FC Entities,
serves as a frame transmission component of the FC Fabric. The
FC End Nodes are unaware of the existence of the FCIP Link.
4) FC Primitive Signals, Primitive Sequences, and Class 1 FC Frames
are not transmitted across an FCIP Link because they cannot be
encoded using FC Frame Encapsulation [23].
5) The path (route) taken by an encapsulated FC Frame follows the
normal routing procedures of the IP Network.
6) An FCIP Entity SHALL have exactly one IP Address.
7) An FCIP Entity may contain multiple FCIP Link Endpoints, but
each FCIP Link Endpoint (FCIP_LEP) communicates with exactly one
other FCIP_LEP, possibly with multiple FCIP Data Engines.
(FCIP_DEs) and multiple TCP connections.
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8) When multiple FCIP_LEPs or multiple FCIP_DEs are in use,
selection of which FCIP_DE to use for encapsulating and
transmitting a given FC Frame outside the scope of this
document. FCIP Entities do not actively participate in FC Frame
routing.
9) The FCIP Control & Services function MAY use TCP/IP quality of
service features (see section 9.2) to support Fibre Channel
capabilities.
10) Each FCIP Entity is statically or dynamically configured with a
list of IP addresses and port numbers corresponding to
participating FCIP Entities. If dynamic discovery of
participating FCIP Entities is supported, the function SHALL be
performed using the Service Location Protocol (SLPv2) [21]. It
is outside the scope of this specification to describe any
static configuration method for participating FCIP Entity
discovery. Refer to section 10 for a detailed description of
dynamic discovery of participating FCIP Entities using SLPv2.
11) FCIP Entities do not actively participate in the discovery of FC
source and destination identifiers. Discovery of FC addresses
(accessible via the FCIP Entity) is provided by techniques and
protocols within the FC architecture as described in FC-FS [6],
FC-SW-2 [5], and FC-GS-3 [7].
12) To support IP Network security, FCIP Entities MUST:
a) implement cryptographically protected authentication and
cryptographic data integrity keyed to the authentication
process, or
b) be capable of operating with external IP security mechanisms
that provide cryptographically protected authentication and
cryptographic data integrity keyed to the authentication
process.
FCIP entities MAY implement data privacy security features.
Security features and requirements are detailed in section 8.
13) FCIP relies on TCP to recover from re-ordering in the IP network.
14) FCIP relies on both TCP and FC error recovery mechanisms to
detect and recover from data loss and corruption within the IP
Network.
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6. The FCIP Model
6.1 FCIP Protocol Model
The relationship between FCIP and other protocols is illustrated in
figure 1.
+------------------------+ FCIP Link +------------------------+
| FCIP |===========| FCIP |
+--------+------+--------+ +--------+------+--------+
| FC-2 | | TCP | | TCP | | FC-2 |
+--------+ +--------+ +--------+ +--------+
| FC-1 | | IP | | IP | | FC-1 |
+--------+ +--------+ +--------+ +--------+
| FC-0 | | LINK | | LINK | | FC-0 |
+--------+ +--------+ +--------+ +--------+
| | PHY | | PHY | |
| +--------+ +--------+ |
| | | |
| | | |
V +--------------------+ V
to Fibre to Fibre
Channel Channel
Environment Environment
Fig. 1 FCIP Protocol Stack Model
Note that the objective of the FCIP Protocol is creation and
maintenance of one or more FCIP Links.
6.2 FCIP Link
The FCIP Link is the basic unit of service provided by the FCIP
Protocol to a FC Fabric. As shown in figure 2, an FCIP Link connects
two portions of an FC Fabric using an IP Network as a transport to
form a single FC Fabric.
/\/\/\/\/\/\ /\/\/\/\/\/\ /\/\/\/\/\/\
\ FC / FCIP \ IP / Link \ FC /
/ Fabric \=========/ Network \=========/ Fabric \
\/\/\/\/\/\/ \/\/\/\/\/\/ \/\/\/\/\/\/
Fig. 2 FCIP Link Model
At the points where the ends of the FCIP Link meet portions of the
FC Fabric, an FCIP Entity (see section 6.4) combines with an FC
Entity as described in section 6.3 to serve as the interface between
FC and IP.
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An FCIP Link SHALL contain at least one TCP connection and MAY
contain more than one TCP connection. The endpoints of a single TCP
connection are FCIP Data Engines (see section 6.6). The endpoints of
a single FCIP Link are FCIP Link Endpoints (see section 6.5).
6.3 FC Entity
A product that tunnels an FC Fabric through an IP Network must
combine an FC Entity with an FCIP Entity (see section 6.4) to form a
complete interface between the FC Fabric and IP Network as shown in
figure 3.
+----------+ /\/\/\/\/\/\ +----------+
| FCIP | FCIP \ IP / Link | FCIP |
| Entity |=========/ Network \=========| Entity |
+----------+ \/\/\/\/\/\/ +----------+
| FC | | FC |
| Entity | | Entity |
+----------+ +----------+
| |
/\/\/\/\/\/\ /\/\/\/\/\/\
\ FC / \ FC /
/ Fabric \ / Fabric \
\/\/\/\/\/\/ \/\/\/\/\/\/
Fig. 3 FC Entity and FCIP Entity Model
The interface between the FC and FCIP Entities is implementation
specific. The minimum requirements placed on an FC Entity by this
specification are listed in annex D. More information about FC
Entities can be found in the Fibre Channel standards and an example
of an FC Entity can be found in FC-BB-2 [4].
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6.4 FCIP Entity
The model for an FCIP Entity is shown in figure 4.
.......................................................
: FCIP Entity :
: :
: +-----------+ :
: | FCIP | :
: | Control & |------------------------------------+ :
: | Services | | :
: | Module | | :
: +-----------+ | :
: | +--------------------+ | :
: | +-------+--------------------+|----+ | :
: | |+-----+--------------------+|----+| | :
: | ||+----| FCIP Link Endpoint |----+|| | :
: | ||| +--------------------+ ||| | :
:.............................................|||.....:
| ||| ||| |
| ||| ||| o<--+
| ||| unique TCP ||| | |
| ||| connections-->||| | |
| ||| ||| | |
+----------+ /\/\/\/\/\/\ |
| FC | \ IP / |
| Entity | / Network \ |
+----------+ \/\/\/\/\/\/ |
| |
/\/\/\/\/\/\ +------------------+
\ FC / +->IP Address &
/ Fabric \ +->Well Known Port
\/\/\/\/\/\/
Fig. 4 FCIP Entity Model
The FCIP Entity is the connection interface point for the IP Network
and is the owner of the IP Address and Well Known Port used to form
TCP connections. An FC Fabric to IP Network interface product SHALL
contain one FCIP Entity for each IP Address assigned to the product.
An FCIP Entity contains an FCIP Control & Services Module to provide
the FC Entity with an interface to key IP Network features. The
interfaces to the IP Network features is implementation specific,
however, to maintain interoperability, the TCP/IP mechanisms used
are specified in this document as follows:
- TCP Connections - see section 7
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- Security - see section 8
- Performance - see section 9
- Discovery - see section 10
The FCIP Link Endpoints in an FCIP Entity provide the FC Frame
transmission features of FCIP.
6.5 FCIP Link Endpoint (FCIP_LEP)
Each time a TCP connection is formed to an IP Address for which no
TCP connection already exists, the FCIP Entity SHALL create a new
FCIP Link Endpoint containing one FCIP Data Engine.
An FCIP_LEP is a transparent data translation point between an FC
Entity and an IP Network. A pair of FCIP_LEPs communicating over one
or more TCP connections create an FCIP Link to join two islands of a
FC Fabric, producing a single FC Fabric.
The IP Network over which the two FCIP_LEPs communicate is not aware
of the FC payloads that it is carrying. Likewise, the FC End Nodes
connected to the FC Fabric are unaware of the TCP/IP based transport
employed in the structure of the FC Fabric.
As shown in figure 5, the FCIP Link Endpoint contains one FCIP Data
Engine for each TCP connection in the FCIP Link.
................................................
: FCIP Link Endpoint :
: +------------------+ :
: +-------+------------------+|----+ :
: |+-----+------------------+|----+| :
: ||+----| FCIP Data Engine |----+|| :
: ||| +------------------+ ||| :
:..............................................:
||| |||
+----------+ /\/\/\/\/\/\
| FC | \ IP /
| Entity | / Network \
+----------+ \/\/\/\/\/\/
|
/\/\/\/\/\/\
\ FC /
/ Fabric \
\/\/\/\/\/\/
Fig. 5 FCIP Link Endpoint Model
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An FCIP_LEP uses normal TCP based flow control mechanisms for
managing its internal resources and matching them with the
advertised TCP Receiver Window Size. An FCIP_LEP MAY communicate
with its FC Entity counterpart to coordinate flow control.
6.6 FCIP Data Engine (FCIP_DE)
The model for one of the multiple FCIP_DEs that may be present in an
FCIP_LEP is shown in figure 6.
+--------------------------------+
| |
|-+ +------------------+ +-|
C |p| | Encapsulation | |p| N
F h -->|1|--->| Engine |--->|2|--> e
i a |-+ +------------------+ +-| t
b n | | I w
r n |-+ +------------------+ +-| P o
e e |p| | De-Encapsulation | |p| r
l <--|4|<---| Engine |<---|3|<-- k
|-+ +------------------+ +-|
| |
+--------------------------------+
Fig. 6 FCIP Data Engine Model
Data enters and leaves the FCIP_DE through four portals (p1 - p4).
The portals do not process or examine the data that passes through
them. They are only the named access points where the FCIP_DE
interfaces with external world. The names of the portals are as
follows:
p1) FC Receiver Portal - The interface through which an FC Frame
enters an FCIP_DE from the FC Entity.
p2) Encapsulated Frame Transmitter Portal - The TCP interface
through which an FCIP encapsulated frame is transmitted to the
IP Network by an FCIP_DE.
p3) Encapsulated Frame Receiver Portal - The TCP interface through
which an FCIP encapsulated frame is received from the IP Network
by an FCIP_DE.
p4) FC Transmitter Portal - The interface through which a
reconstituted FC frame exits an FCIP_DE to the FC Entity.
The work of the FCIP_DE is done by the Encapsulation and De-
Encapsulation Engines. The Engines have two functions:
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1) Encapsulating and de-encapsulating FC Frames using the
encapsulation format described in FC Frame Encapsulation [23]
and in section 6.6.1 of this document, and
2) Detecting some data transmission errors and performing minimal
error recovery as described in section 6.6.2.
Data flows through the FCIP_DE as follows:
1) An FC Frame arrives at the FC Receiver Portal and is passed to
the Encapsulation Engine. The FC Frame is assumed to have been
processed by the FC Entity according to the applicable FC rules
and is not validated by the FCIP_DE.
2) In the Encapsulation Engine the encapsulation format described
in FC Frame Encapsulation [23] and in section 6.6.1 of this
document SHALL be applied to prepare the FC Frame for
transmission over the IP Network.
3) The entire encapsulated frame SHALL be passed to the
Encapsulated Frame Transmitter Portal where it SHALL be inserted
in the TCP byte stream.
4) Transmission of the encapsulated frame over the IP Network
follows all the TCP rules of operation. This includes but is not
limited to the in-order delivery of bytes in the stream, as
specified by TCP [9].
5) The encapsulated FC Frame arrives at the partner FCIP Entity
where it enters the FCIP_DE through the Encapsulated Frame
Receiver Portal and is passed to the De-Encapsulation Engine for
processing.
6) The De-Encapsulation Engine SHALL validate the incoming TCP byte
stream as described in section 6.6.2 and SHALL de-encapsulate
the FC Frame according to the encapsulation format described in
FC Frame Encapsulation [23] and in section 6.6.1 of this document.
7) In the absence of errors, the de-encapsulated frame SHALL be
passed to the FC Transmitter Portal for delivery to the FC Entity.
Every FC Frame that arrives at the FC Receiver Portal SHALL be
transmitted on the IP Network as described in steps 1 through 4
above. Data bytes arriving at the Encapsulated Frame Receiver Portal
SHOULD be transmitted to the FC Transmitter Portal as described in
steps 5 through 7, but this MAY NOT always be the case.
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6.6.1 FCIP Encapsulation of FC Frames
The FCIP encapsulation of FC frames employs FC Frame Encapsulation
[23].
The features from FC Frame Encapsulation that are unique to
individual protocols SHALL be applied as follows for the FCIP
encapsulation of FC frames.
The Protocol# field SHALL contain 1 in accordance with the IANA
Considerations annex of FC Frame Encapsulation [23].
The Protocol Specific field SHALL have the format shown in figure 7.
Note: the word numbers in figure 7 are relative to the complete FC
frame encapsulation header, not to the Protocol Specific field.
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|
+---------------------------------------------------------------+
1| replication of encapsulation word 0 |
+-------------------------------+-------------------------------+
2| reserved | -reserved |
+-------------------------------+-------------------------------+
Fig. 7 FCIP Usage of FC Frame Encapsulation Protocol Specific
field
Word 1 of the Protocol Specific field SHALL contain an exact copy of
word 0 in FC Frame Encapsulation [23].
Word 2 of the Protocol Specific field is reserved for future
enhancements to the FCIP protocol.
The reserved field (bits 31-16 in word 2): SHALL contain 0.
The -reserved field (bits 15-0 in word 2): SHALL contain 65535 (or
0xFFFF).
The CRCV (CRC Valid) Flag SHALL be set to 0.
The CRC field SHALL be set to 0.
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6.6.2 FCIP Data Engine Error Detection and Recover
6.6.2.1 TCP Assistance With Error Detection and Recovery
The FCIP_LEP assumes that, if TCP determines that there are TCP
checksum errors, TCP applies the appropriate TCP retransmission and
error recovery procedures. So the FCIP_DE gets an ordered delivery
of FCIP frames with the TCP detected errors being transparent to the
FCIP_DE.
6.6.2.2 Errors in FCIP Headers and Discarding FCIP Frames
Bytes delivered through the Encapsulated Frame Receiver Portal that
are not correctly delimited as defined by the FC Frame Encapsulation
[23] SHOULD NOT be forwarded on to the FC Entity.
Synchronization of the FCIP_DE to the FCIP Frames in the data stream
entering the Encapsulated Frame Receiver Portal is maintained using
the FC Frame Encapsulation header's frame length field to determine
where in the data stream the next FC Encapsulation header is
located. Synchronization SHALL be verified by checking the validity
and positioning of any combination of the following FC Frame
Encapsulation information:
a) Protocol # field and its ones complement;
b) Version field and its ones complement;
c) Replication of encapsulation word 0 in word 1;
d) Reserved field and its ones complement;
e) Flags field and its ones complement;
f) Length field and its ones complement;
g) Time stamp [integer] and time stamp [fraction] fields;
h) CRC field is equal to zero;
i) SOF fields and ones complement fields;
j) Format and values of FC header;
k) CRC of FC frame;
l) EOF fields and ones complement fields; and/or
m) FC Encapsulation header information of next encapsulated frame.
For FCIP Frames with header errors, the FCIP_DE SHALL discard the
frame. Such errors should be considered carefully, since some may be
synchronization errors. Errors in encapsulated FCIP Frames detected
by the FCIP_DE that affect synchronization with the Encapsulated
Frame Receiver Portal byte stream SHALL be handled as defined by
section 6.6.2.4.
An error in an encapsulated FCIP Frame that effects the
synchronization may require the FCIP Entity to notify the FC Entity
that the previously delivered FC Frame was invalid.
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Whenever an FCIP_DE discards bytes delivered through the
Encapsulated Frame Receiver Portal, it SHALL cause the FC Entity to
be notified and provided with a suitable description of the reason
bytes were discarded.
6.6.2.3 IP Network Transit Time Validation
The FCIP_DE SHALL use the valid time stamp information in the FC
Frame Encapsulation [23] header to determine if received FCIP Frames
have been delayed by more than R_A_TOV in the IP Network. If an FCIP
Frame has been delayed by more than R_A_TOV in the IP network, the
FCIP_DE SHALL discard the FCIP Frame as described in section
6.6.2.2. The discarding of delayed FCIP frames SHALL continue until
a FCIP Frame is processed whose life in the IP Network is smaller
than R_A_TOV.
Note that unlike a physical Fibre Channel link, an FCIP Link MAY
involve IP routing dynamics that produce reliable, ordered delivery
at the TCP layer, with the result that some FC Fabric operating
constraints may be violated. The FCIP_DE is responsible for
detecting violations R_A_TOV FC Fabric constraint and discarding
affected frames.
6.6.2.4 Synchronization Failures
If an FCIP_DE determines that it cannot find the next FCIP header in
the byte stream entering through the Encapsulated Frame Receiver
Portal, the FCIP_DE SHALL either:
a) close the TCP connection [9] [11];
b) recover synchronization by searching the bytes delivered by the
Encapsulated Frame Receiver Portal for a valid FCIP Frame header
having the correct properties, and discarding bytes delivered by
the Encapsulated Frame Receiver Portal until a valid FCIP Frame
header is found; or
c) attempt to recover synchronization as described in b) and if
synchronization cannot be recovered close the TCP connection as
described in a).
If the FCIP_DE attempts to recover synchronization, the
resynchronization algorithm used SHALL meet the following
requirements:
a) discard or identify with an EOFa (see FC-FS [6] and FC Frame
Encapsulation [23])those FC frames and fragments of frames
identified before synchronization has again been completely
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verified. The number of FC frames not forwarded may vary based
on the algorithm used;
b) return to sending valid FC frames only after synchronization has
been verified; and
c) close the TCP/IP connection if the algorithm ends without
verifying successful synchronization. The probability of failing
to synchronize successfully and the time necessary to determine
whether or not synchronization was successful may vary with the
algorithm used.
An example algorithm meeting these requirements can be found in
annex A.
7. TCP Connection Management
7.1 TCP Connection Establishment
7.1.1 Creating a New TCP Connection
The FC Entity SHALL request creation of a new TCP Connection by
transmitting at least the following information to the FCIP Entity:
- IP Address
- R_A_TOV for the FCIP_Link
- TCP Connection Parameters (see section 7.2)
- Security Parameters (see section 8)
- Quality of Service Parameters (see section 9)
In response to a request from the FC Entity the FCIP Entity shall
generate a TCP connect request [9] to the FCIP Well-Known Port at
the specified IP Address. If the TCP connect request is rejected,
the FCIP Entity SHALL so inform the FC Entity.
If the TCP connect request is accepted, and the IP Address is one to
which no other TCP connections exist, the FCIP Entity SHALL:
1) Create a new FCIP_LEP for the new FCIP Link,
2) Create a new FCIP_DE within the newly created FCIP_LEP to
service the new TCP connection, and
3) Inform the FC Entity of the new FCIP_LEP and FCIP_DE.
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If the TCP connect request is accepted, and the IP Address is one
for which a TCP connection already exists, the FCIP Entity SHALL:
1) Create a new FCIP_DE within the existing FCIP_LEP to service the
new TCP connection, and
2) Inform the FC Entity of the FCIP_LEP and new FCIP_DE.
7.1.2 Processing TCP Connect Requests
The FCIP Entity SHALL listen for new TCP connection requests [9] on
the FCIP Well-Known Port. An FCIP Entity MAY also accept and
establish TCP connections to a TCP port number other than the FCIP
Well-Known Port, as configured by the network administrator.
Upon receipt of a TCP connect request, the FCIP Entity SHALL
determine if a TCP connection already exists for the IP Address
making the TCP connect request. The FCIP Entity SHALL notify the FC
Entity of the TCP connect request, transmitting at least the
following information:
- IP Address
- R_A_TOV for the FCIP_Link (zero for a new FCIP_LEP)
- Information about the FCIP_LEP, new or existing
- Information about the FCIP_DE for the new TCP connection
- TCP Connection Parameters (see section 7.2)
- Security Parameters (see section 8)
- Quality of Service Parameters (see section 9)
In response to the information provided by the FCIP Entity, the FC
Entity MUST either accept or reject the TCP connect request. If the
FC Entity rejects the TCP connect request, the FCIP Entity SHALL
terminate the TCP connect request [9]. If the FC Entity accepts the
TCP connect request, the FCIP Entity SHALL:
1) Accept the TCP connect request,
2) Finalize creation of the new FCIP_DE for the new TCP connection,
and
3) If the new TCP connection is to an IP Address for which no other
TCP connection exists, finalize the creation of the FCIP_LEP.
7.2 TCP Connection Parameters
In order to provide efficient management of FCIP_LEP resources as
well as FCIP Link resources, coordination of certain TCP connection
parameters between the FC Entity and FCIP Entity is RECOMMENDED.
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7.2.1 TCP Selective Acknowledgement Option
The Selective Acknowledgement option RFC 2883 [22] allows the
receiver to acknowledge multiple lost packets in a single ACK,
enabling faster recovery. If authorized by the FC Entity, an FCIP
Entity MAY negotiate use of TCP SACK and use it for faster recovery
from lost packets and holes in TCP sequence number space.
7.2.2 TCP Window Scale Option
This option allows TCP window sizes larger than 16-bit limits to be
advertised by the receiver. It is necessary to allow data in long
fat networks to fill the available pipe. This also implies buffering
on the TCP sender that matches the (bandwidth*RTT) product of the
TCP connection. An FCIP_LEP SHALL use locally available mechanisms
to set a window size that matches the available local buffer
resources and the desired throughput.
7.2.3 IP DSCP Option
The RECOMMENDED IP DSCP field setting is 101110 corresponding to the
EF service.
<Need better wording to fit current Diffserv specifications.>
7.2.4 Protection against sequence number wrap
It is RECOMMENDED that FCIP Entities implement protection against
sequence number wrap. It is quite possible that within a single
connection, TCP sequence numbers wrap within a timeout window.
7.2.5 TCP No Delay Option
FCIP Entities SHALL disable the Nagle TCP No Delay option. This
option is designed for usage in a telnet environment.
7.2.6 TCP Acknowledgement Timeout
TCP has a TCP acknowledgement timeout. This is a variable timeout.
<Need to elaborate on TCP timeouts and define how Fibre Channel
timeouts map to TCP timeouts.>
7.3 TCP Connection Considerations
An FCIP_LEP SHALL implement established TCP mechanisms as defined in
RFC 2581 [18] for congestion control on its connections.
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It is RECOMMENDED that FCIP_LEPs use the TCP mechanisms for Long Fat
Networks (LFNs) (i.e. an IP network with large (bandwidth*delay)
product), as defined in RFC 1072 [10].
In idle mode, a TCP connection "keep alive" option of TCP is
normally used to keep a connection alive. However, this timeout is
fairly large and may prevent early detection of loss of
connectivity. In order to facilitate faster detection of loss of
connectivity, FC Entities SHOULD implement some form of Fibre
Channel connection failure detection.
7.4 Flow Control Mapping between TCP and FC
The FCIP Entity and FC Entity are connected the IP Network and FC
Fabric, respectively, and they need to follow the flow control
mechanisms of both TCP and FC, which work independent of each other.
This section provides guidelines as to how the FCIP Entity can map
TCP flow control to status notifications to the FC Entity.
There are two scenarios when the flow control management becomes
crucial:
1) When there is line speed mismatch between the FC and IP
interfaces.
Even though it is RECOMMENDED that both the FC and IP interfaces
to the FC Entity and FCIP Entity, respectively, be of comparable
speeds, it is possible to carry FC traffic over an IP Network
that has a different line speed and bit error rate.
2) When the FC Fabric or IP Network encounters congestion.
Even when both the FC Fabric or IP network are of comparable
speeds, during the course of operation the FC Fabric or the IP
Network could encounter congestion due to transient conditions.
The FCIP Entity and FC Entity need to work cooperatively to use the
available flow control mechanisms in the TCP and FC protocols to
handle these situations. This specification does not specify any
particular mechanism to handle the flow control but leaves this to
implementation's choice.
If the Encapsulation Frame Transmitter Portal is unable to transmit
encapsulated FCIP Frames at the experienced data rate, the FCIP
Entity MUST request that the FC Entity reduce the rate at which new
FC Frames arrive at the FC Receiver Portal.
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If the FC Receiver Portal is unable to accept de-encapsulated FC
Frames at the experienced rate, the FC Entity MAY request the FCIP
Entity to reduce the rate at which new FC Frames are delivered. The
FCIP_DE MAY use TCP windowing techniques to control the packet
arrival rate from the IP Network. This MAY involve advertising zero-
window on TCP connection(s) occasionally so that the TCP
connection(s) are flow controlled while the FC Fabric is
encountering congestion.
8. Security
8.1 Considerations
Using a wide-area, general purpose network such as an IP Network in
a position normally occupied by physical cabling introduces some
security problems not normally encountered in Fibre Channel Fabrics.
FC transport media are typically protected physically from outside
access; IP Networks typically invite outside access.
The general effect is that the security of the entire FC Fabric is
only as good as the security of the entire IP Network through which
it tunnels. The following broad classes of attacks are possible:
1) Unauthorized Fibre Channel elements can gain access to resources
through normal Fibre Channel processes.
2) Unauthorized agents can monitor and manipulate Fibre Channel
traffic flowing over physical media used by the IP Network and
under control of the agent.
To a large extent, these security risks are typical of the risks
facing any other application using an IP Network. They are mentioned
here only because Fibre Channel storage networks are not normally
suspicious of the media. Fibre Channel Fabric administrators will
need to be aware of these additional security risks.
8.2 IP Network Security Requirements
Security protocols and procedures used in other IP applications MAY
be used for FCIP. FCIP Entities MUST ensure secure operation of FCIP
Links by implementing one of the following two methods:
1) by using ESP [13] from the IPSec Security Protocol Suite with
NULL encryption [14] for cryptographic data integrity and
integrity of authentication. Authentication is performed using
SRP [RFC2945]. This method is discussed in section 8.3; or
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2) by appropriate configuration of an external entity that
implements IP security using mechanisms such as IPSec and
Virtual Private Networks. This method is discussed in section 8.4.
The mechanism for configuring whether a particular deployment uses
1) or 2) is outside the scope of this document.
Note: Two overviews of the IPSec Security Protocol Suite are
available in RFC 2401 [12] and RFC 2411 [15].
8.3 Integrated Security
When both FCIP Entity and IP Security implementations are integrated
into a single device, IPSec ESP (in transport mode) MUST be
implemented.
Upon receiving a TCP connection request, the receiving FCIP Entity
SHALL identify the FCIP Link per the IP address pair of the
connection. It SHALL then verify that the FCIP Link has been
previously authenticated. If not, the FCIP Entity SHALL authenticate
a new peer using a separate TCP connection. This TCP connection is
used for negotiation of SRP related parameters.
<SRP message negotiation will be per iSCSI discussions>
If authentication fails, the original TCP connection that initiated
the authentication exchange is terminated and the FC Entity is not
informed that a TCP connect request was received.
If the authentication is successful, a new FCIP_LEP is created, with
the authenticated FCIP Link as described in section 7.1.2.
The FCIP Entity remembers the IP pair and the key material for
authentication, so that any future TCP connections for that IP
address pair bypasses this authentication step. The key material is
then used as part of the ESP Security Parameters.
<association of SRP key material with ESP header will be per iSCSI
discussions>
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8.4 External Security Gateway
Figure 8 illustrates the use of an externally supplied security
gateway for securing the FCIP Link.
+--------+ Insecure +--------+ Secure +--------+ Insecure +-------+
| FCIP | Network | IPSec | Network | IPSec | Network |FCIP |
| Entity |----------| Device |---------| Device |----------|Entity |
+--------+ +--------+ +--------+ +-------+
Fig. 8 External Security Gateway Model
In this deployment, only certain parts of the FCIP Link are exposed
to security threats and so only these specific parts of the FCIP
Link need to be secured. The part of the network between the two
security gateways is secured using devices implementing IPSec.
The IPSec Device or any other equivalent gateway is required to
operate in tunnel mode, so that the IP addresses of the two FCIP
Entities are visible through the security devices that are
implemented.
8.5 Security Information Exchanged Between FC and FCIP Entities
TBD
9. Performance
9.1 Considerations
The FCIP_DE does not interpret the contents of an FC Frame (except
for attaching the correct byte-encoded SOF and EOF) nor does it do
any FC payload processing. This allows any FC traffic to be tunneled
across at high throughput rates.
If fragmentation at the data link and IP layers is avoided by the
use of path MTU discovery, throughput performance is enhanced.
The Flow Control Protocol (discussed in section 7.4) provides the
ability to stream gigabit FC data when using a large window size.
It is RECOMMENDED that FCIP Entities use the TCP mechanisms for Long
Fat Networks (LFNs) when they are used in IP networks with a large
(bandwidth*delay) product. These mechanisms include TCP window scale
option, Selective Acknowledgement, among others. See section 7.2.
In order to achieve better TCP aggregate throughput in the face of
packet losses, a pair of peer FC Entities MAY use multiple TCP
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connections, and use appropriate policies for mapping FC Frames to
these connections. Section 7.1 describes the steps an FCIP Entity
takes in support of multiple TCP connection usage. All other aspects
of using multiple TCP connections are outside the scope of this
document.
The reason for using multiple TCP connections is the TCP's slow-
start algorithm, which reduces TCP's window whenever it detects
congestion in the network. If, on the other hand, the traffic is
distributed across multiple connections, all the connections will
not be affected at the same time, resulting in a better aggregate
throughput.
Note that even though multiple connections provide better aggregate
throughput (when packet losses occur on IP Networks), their use is
not a requirement. A pair of FC Entities MAY choose to use single
TCP connection to tunnel the FC traffic.
9.2 QoS Support
The Differentiated Services Architecture (diffserv) provides a
"Class of Service" to a flow aggregate [16], [17]. At so-called
diffserv boundaries, IP packets are classified and marked. Within
the diffserv domain, resources - bandwidth and buffers - are
allocated for each classification.
Packets with the same classification use the resources allocated for
the classification. IP packets with the same destination and class
marking exit a diffserv capable router in the same order they
arrived. Packets with the same destination but different class
markings exit according to priorities assigned to the different
class markings.
The Diffserv has renamed the Ipv4 TOS field as Differentiated
Services Code Point (DSCP). The DSCP indicates the particular
behavior a packet is to receive at each router.
How a packet gets marked is based on a policy administered and
configured into the network. [20] and [19] provide various encodings
of the DSCP field to achieve a specific behavior from the routers.
There may be several ways to administer the policies and the policy
definition is up to the network provider. That is one network
provider MAY choose to mark all packets going from one source IP
address to a specific destination as "high priority", while another
might mark just a specific traffic type (e.g., HTTP) as "high
priority". Thus packets carry the desired class information and each
diffserv-capable router treats the packet according to the
information in its DSCP field. This is referred to as Per Hop
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Behavior (PHB).
Currently, the IETF standards define essentially 3 types of
services: Expedited Forwarding (EF) [20], Assured Forwarding (AF)
[19], or Default Forwarding (DF) [16], [17] - that corresponds to
its DSCP.
[17] specifies the AF service AF PHB provides a way to prioritize
best-effort traffic. Currently, 4 AF classes and 3 drop precedence
levels are specified providing 12 different levels of forwarding
assurances. The DSCP value specifies a drop-order in the event that
a packet experiences congestion at a subsequent diffserv router.
[20] specifies the DSCP code point equal to 101110 EF service which
is also sometimes refereed to as "Premium" service. When supported,
this class behavior has the lowest levels of latency, packet loss,
and delay variation. This service behavior most closely matches the
Fibre Channel characteristics. This is therefore the RECOMMENDED
DSCP setting in the IP DSCP field.
What resources are not used for EF and AF are left for the DF
services which is really a best-effort service.
Note that if a packet is being forwarded over an underlying network
without diffserv support, then the packet would simply receive best-
effort service regardless of its DSCP field setting.
9.3 QoS Information Exchanged Between FC and FCIP Entities
TBD
10. Dynamic Discovery of Participating FCIP Entities
10.1 Requirements
If dynamic discovery of participating FCIP Entities is supported the
function SHALL be performed using the Service Location Protocol
(SLPv2) [21].
Additional details TBD.
10.2 Discovery Information Exchanged Between FC and FCIP Entities
TBD
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11. References
[1] Bradner, S., "The Internet Standards Process -- Revision 3", BCP
9, RFC 2026, October 1996.
[2] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[3] Fibre Channel Backbone (FC-BB), T11 Project 1238-D, Rev 4.8,
March 5, 2001 (www.t11.org).
[4] Fibre Channel Backbone -2 (FC-BB-2), T11 Project 1466-D,
(www.t11.org).
[5] Fibre Channel Switch Fabric -2 (FC-SW-2), T11 Project 1305-D,
Rev. 5.2, May 23, 2001 (www.t11.org).
[6] Fibre Channel Framing and Signaling (FC-FS), T11 Project 1331-D,
Rev 1.2, February 16, 2001 (www.t11.org).
[7] Fibre Channel Generic Services -3, ANSI NCITS.348-200x, November
28, 2000.
[8] http://www.t11.org
[9] "Transmission Control Protocol", RFC 793, Sept. 1981.
[10] Jacobson & Braden, "TCP Extensions for Long-Delay Paths", RFC
1072, October 1988.
[11] Braden, "Requirements for Internet Hosts -- Communication
Layers", RFC 1122, October 1989
[12] Kent, S. and Atkinson, R., "Security Architecture for the
Internet Protocol", RFC 2401, Nov. 1998.
[13] Kent, S. and Atkinson, R., "IP Encapsulating Security Payload
(ESP)", RFC 2406, Nov. 1998.
[14] Glenn, R., Kent, S., "The NULL Encryption Algorithm and Its Use
With IPsec", RFC 2410, Nov. 1998
[15] Thayer, R., Glenn, R., and Doraswamy, N., "IP Security Document
Roadmap", RFC 2411, Nov. 1998.
[16] Nichols, K., Blake, S., Baker, F. and D. Black, "Definition of
the Differentiated Services Field (DS Field) in the IPv4 and
Ipv6 Headers", RFC 2474, December 1998.
Rajagopal, et al. Standards Track [Page 27]
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[17] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z., Weiss,
W., "An Architecture for Differentiated Services", RFC 2475,
Dec. 1998.
[18] Allman, et. al., "TCP Congestion Control", RFC 2581, April 1999.
[19] Heinanen, J., Baker, F., Weiss, W., Wroclawski, J., "An Assured
Forwarding PHB", RFC 2597, June 1999.
[20] Jacobson, V., Nichols, K., Poduri, K., "An Expedited Forwarding
PHB Group", RFC 2598, June 1999.
[21] E.Guttman, C. Perkins, J. Veizades, M. Day. Service Location
Protocol, version 2, RFC 2608, July, 1999.
[22] Floyd, et al, "SACK Extension", RFC 2883, July 2000.
[23] Weber, Rajagopal, Travostino, Chau, O'Donnell, Monia Merhar,
"FC Frame Encapsulation", draft-ietf-ips-fcencapsulation-__.txt
(RFC reference and date to be added during standards action).
The following reference concerns SLP, see [21]. It is not referenced
in this revision of this draft but may be referenced in future
revisions.
[24] E.Guttman, C. Perkins, J. Kempf. Service Templates and Service:
Schemes, RFC 2609, July 1999.
12. Bibliography
The following references may prove informative to readers unfamiliar
with Fibre Channel.
Kembel, R., "The Fibre Channel Consultant: A Comprehensive
Introduction", Northwest Learning Associates, 1998
13. Acknowledgments
Funding for the RFC Editor function is currently provided by the
Internet Society.
Rajagopal, et al. Standards Track [Page 28]
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14. Authors' Addresses
Murali Rajagopal Raj Bhagwat
LightSand Communications, Inc. LightSand Communications, Inc.
24411 Ridge Route Dr. 24411 Ridge Route Dr.
Suite 135 Suite 135
Laguna Hills, CA 92653 Laguna Hills, CA 92653
USA USA
Phone: +1 949 837 1733 x101 Phone: +1 949 837 1733 x104
Email: muralir@lightsand.com Email: rajb@lightsand.com
R. Andy Helland Elizabeth G. Rodriguez
LightSand Communications, Inc. Lucent Technologies
375 Los Coches Street 1202 Richardson Drive, Suite 104
Milpitas, CA 95035 Richardson, TX 75080
USA USA
Phone: +1 408 404 3119 Phone: +1 972 231 0672
Fax: +1 408 941 2166 Fax: +1 972 644 5857
Email: andyh@lightsand.com Email: egrodriguez@lucent.com
Sriram Rupanagunta Neil Wanamaker
Aarohi Communications Akara
3200 Montelena Drive 10624 Icarus Court
San Jose, CA 95135 Austin, TX 78726
USA USA
Phone: +1 408 966 8309 Phone: +1 512 257 7633
Email: sriramr@aarohi-inc.com Fax: +1 512 257 7877
Email: nwanamaker@akara.com
Steve Wilson Bob Snively
Brocade Comm. Systems, Inc. Brocade Comm. Systems, Inc.
1745 Technology Drive 1745 Technology Drive
San Jose, CA. 95110 San Jose, CA 95110
USA USA
Phone: +1 408 487 8128 Phone: +1 408 487 8135
Fax: +1 408 487 8101 Email: rsnively@brocade.com
email: swilson@brocade.com
Ralph Weber
ENDL Texas, representing Brocade
Suite 102 PMB 178
18484 Preston Road
Dallas, TX 75252
USA
Phone: +1 214 912 1373
Email: roweber@acm.org
Rajagopal, et al. Standards Track [Page 29]
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David Peterson Donald R. Fraser
Cisco Systems - SRBU Compaq Computer Corporation
6450 Wedgwood Road 301 Rockrimmon Blvd., Bldg. 5
Maple Grove, MN 55311 Colorado Springs, CO 80919
USA USA
Phone: +1 763 398 1007 Phone: +1 719 548 3272
Cell: +1 612 802 3299 Email: don.fraser@compaq.com
Email: dap@cisco.com
Vi Chau Gaby Hecht
Gadzoox Networks, Inc. Gadzoox Network, Inc.
16241 Laguna Canyon Road 16241 Laguna Canyon Road
Suite 100 Suite 100
Irvine, CA 92618 Irvine, CA 92618
USA USA
Phone: +1 949 789 4639 Phone: +1 949 789 4642
Fax: +1 949 453 1271 Fax: +1 949 453 1271
Email: vchau@gadzoox.com Email: ghecht@Gadzoox.com
Ken Hirata Jim Nelson
Vixel Corporation Vixel Corporation
15245 Alton Parkway, Suite 100 15245 Alton Parkway, Suite 100
Irvine, CA 92618 Irvine, CA 92618
USA USA
Phone: +1 949 788 6368 Phone: +1 949 450 6159
Fax: +1 949 753 9500 Fax: +1 949 753 9500
Email: ken.hirata@vixel.com Email: Jim.Nelson@vixel.com
Michael E. O'Donnell Anil Rijhsinghani
McDATA Corporation McDATA Corporation
310 Interlocken Parkway 5 Brickyard lane
Broomfield, Co. 80021 Westboro, MA 01581
USA USA
Phone: +1 303 460 4142 Phone: +1 508 870 6593
Fax: +1 303 465 4996 Email:
Email: modonnell@mcdata.com anil.rijhsinghani@mcdata.com
Milan J. Merhar Craig W. Carlson
43 Nagog Park QLogic Corporation
Pirus Networks 6321 Bury Drive
Acton, MA 01720 Eden Prairie, MN 55346
USA USA
Phone: +1 978 206 9124 Phone: +1 952 932 4064
Email: Milan@pirus.com Email: craig.carlson@qlogic.com
Rajagopal, et al. Standards Track [Page 30]
Internet-Draft Fibre Channel Over TCP/IP (FCIP) June, 2001
Venkat Rangan Larwrence J. Lamers
Rhapsody Networks Inc. SAN Valley
3450 W. Warren Ave. 4611 Park Norton Place
Fremont, CA 94538 San Jose, CA 95136-2523
USA USA
Phone: +1 510 743 3018 Phone: +1 408 626 1285
Fax: +1 510 687 0136 Email: ljlamers@ieee.org
Email: venkat@rhapsodynetworks.com
15. Full Copyright Statement
Copyright (C) The Internet Society (2001). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph
are included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
ANNEX A - Example of synchronization recovery algorithm
Synchronization may be recovered as specified in section 6.6.2.4. An
example of an algorithm for searching the bytes delivered to the
Encapsulated Frame Receiver Portal for a valid FCIP Frame header is
provided in this annex.
This resynchronization uses the principle that a valid FCIP data
stream must contain at least one valid header every 2148 bytes (the
maximum length of an encapsulated frame). Although other data
patterns containing apparently valid headers may be contained in the
Rajagopal, et al. Standards Track [Page 31]
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stream, the FC CRC or frame validity of the data patterns contained
in the data stream will always be either interrupted by or
resynchronized with the valid FCIP Frame encapsulation headers.
Consider the case shown in figure 9. A series of short FCIP Frames,
perhaps from a trace, are embedded in larger FCIP Frames, say as a
result of a trace file being transferred from one disk to another.
The headers for the short frames are denoted SFH and the long frame
headers are marked as LFH.
+-+--+-+----+-+----+-+----+-+-+-+---+-+---
|L| |S| |S| |S| |S| |L| |S|
|F| |F| |F| |F| |F| |F| |F|...
|H| |H| |H| |H| |H| |H| |H|
+-+--+-+----+-+----+-+----+-+-+-+---+-+---
| |
|<---------2148 bytes-------->|
Fig. 9 Example of resynchronization data stream
A resynchronization attempt that starts just to the right of an LFH
will find several SFH frames before discovering that they do not
represent the transmitted stream of frames. Within 2148 bytes plus
or minus, however, the resynchronization attempt will encounter an
SFH whose length does not match up with the next SFH because the LFH
will fall in the middle of the short frame pushing the next header
farther out in the byte stream.
Note that the resynchronization algorithm cannot forward any
prospective FC Frames to the FC Transmitter Portal because until
synchronization is completely established there is no certainty that
anything that looked like an FCIP Frame really was one. For example,
an SFH might fortuitously contain a length that points exactly to
the beginning of an LFH. The LFH would identify the correct
beginning of a transmitted frame, but that in no way guarantees that
the SFH was also a correct FCIP Frame header.
There exist some data streams that cannot be resynchronized by this
algorithm. If such a data stream is encountered, the algorithm
causes the TCP connection to be closed.
The resynchronization assumes that security and authentication
procedures outside the FCIP Entity are protecting the valid data
stream from being replaced by an intruding data stream containing
valid FCIP data.
Rajagopal, et al. Standards Track [Page 32]
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The following steps are one example of how an FCIP_DE might
resynchronize with the data stream entering the Encapsulated Frame
Receiver Portal.
1) Search for candidate and strong headers:
The data stream entering the Encapsulated Frame Receiver Portal
is searched for 12 bytes in a row containing the required values
for:
a) Protocol field,
b) Version field,
c) ones complement of the Protocol field,
d) ones complement of the Version field,
e) replication of encapsulation word 0 in word 1, and
f) Reserved field and its ones complement.
If such a 12-byte grouping is found, the FCIP_DE assumes that it
has identified bytes 0-2 of a candidate FCIP encapsulation header.
All bytes up to and including the candidate header byte are
discarded.
If no candidate header has been found after searching a
specified number of bytes greater than some multiple of 2148
(the maximum length of an encapsulated frame), resynchronization
has failed and the TCP/IP connection is closed.
Word 3 of the candidate header contains the Frame Length and
Flags fields and their ones complements. If the fields are
consistent with their ones complements, the candidate header is
considered a strong candidate header. The Frame Length field is
used to determine where in byte stream the next strong candidate
header should be and processing continues at step 2).
2) Use multiple strong candidate headers to locate a verified
candidate header:
The Frame Length in one strong candidate header is used to skip
incoming bytes until the expected location of the next strong
candidate header is reached. Then the tests described in step 1)
are applied to see if another strong candidate header has
successfully been located.
All bytes skipped and all bytes in all strong candidate headers
processed are discarded.
Strong candidate headers continue to be verified in this way for
at least 4296 bytes (twice the maximum length of an encapsulated
Rajagopal, et al. Standards Track [Page 33]
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frame). If at anytime a verification test fails, processing
restarts at step 1 and a retry counter is incremented. If the
retry counter exceeds 3 retries, resynchronization has failed
and the TCP connection is closed.
After strong candidate headers haves been verified for at least
4296 bytes, the next header identified is a verified candidate
header and processing continues at step 3).
Note: If a strong candidate header was part of the data content
of an FC frame, the encapsulated frame defined by that or a
subsequent strong candidate header will eventually cross an
actual header in the byte stream. As a result it will either
identify the actual header as a strong candidate header or it
will lose synchronization again because of the extra 28 bytes in
the length, returning to step 1 as described above.
3) Use multiple strong candidate headers to locate a verified
candidate header:
Incoming bytes are skipped and discarded until the next verified
candidate header is reached. Each verified candidate header is
tested against the full collection of tests listed in section
6.6.2.2 as would normally be the case.
Verified candidate headers continue to be located and tested in
this way for a minimum of 4296 bytes (twice the maximum length
of an encapsulated frame). If all are verified candidate headers
encountered are valid, the last verified candidate header is a
valid header. At this point the FCIP_DE stops discarding bytes
and begins normal FCIP de-encapsulation begins, including for
the first time since synchronization was lost, delivery of FC
frames through the FC Transmitter Portal according to normal
FCIP rules.
If any verified candidate headers are invalid but meet all the
requirements of a strong candidate header, increment the retry
counter and return to step 2). If any verified candidate headers
are invalid and fail to meet the tests for a strong candidate
header, increment the retry counter and return to step 1. If the
retry counter exceeds 4 retries, resynchronization has failed
and the TCP/IP connection is closed.
A flowchart for this algorithm can be found in figure 10.
Rajagopal, et al. Standards Track [Page 34]
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Synchronization is lost
|
_____________v_______________
| |
| Search for candidate header |
+----------->| |
| | Found Not Found |
| | (Strong candidate) |
| |_____________________________|
| | |
| | + --------->Close TCP/IP
| _______v_____________________ Connection
| | |
| | Enough strong candidate |
| +---->| headers identified? |
| | | |
| | | No Yes |
| | | (Verified candidate) |
| | |_____________________________|
|___________________| |
^ | |
| | |
| | _______________________v_____
| | | |
| | | Enough verified candidate |
| | | headers validated? |
| | | |
| | | No Yes |
| | | (Resynchronized) |
| | |_____________________________|
| | | |
| | ______v__________ | Resume
| | | | + ---> Normal
| | | Synchronization | De-encapsulation
| | | Lost? |
| | | |
| | | No Yes |
| | |_________________|
| | | |
| |________| |
|___________________________|
Fig. 10 Flow diagram of simple synchronization example
Rajagopal, et al. Standards Track [Page 35]
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ANNEX B - Relationship between FCIP and IP over FC (IPFC)
IPFC (RFC 2625) describes the encapsulation of IP packets in FC
frames. It is intended to facilitate IP communication over an FC
network.
FCIP describes the encapsulation of FC frames in TCP segments which
in turn are encapsulated inside IP packets for transporting over an
IP network. It gives no consideration to the type of FC frame that
is being encapsulated. Therefore, the FC frame may actually contain
an IP packet as described in the IP over FC specification (RFC
2625). In such a case, the data packet would have:
- Data Link Header
- IP Header
- TCP Header
- FCIP Header
- FC Header
- IP Header
Note: The two IP headers would not be identical to each other. One
would have information pertaining to the final destination while the
other would have information pertaining to the FCIP Entity.
The two documents focus on different objectives. As mentioned above,
implementation of FCIP will lead to IP encapsulation within IP.
While perhaps inefficient, this should not lead to issues with IP
communication. One caveat: if a Fibre Channel device is
encapsulating IP packets in an FC frame (e.g. an IPFC device), and
that device is communicating with a device running IP over a non-FC
medium, a second IPFC device may need to act as a gateway between
the two networks. This scenario is not specifically addressed by FCIP.
There is nothing in either of the specifications to prevent a single
device from implementing both FCIP and IP-over-FC (IPFC), but this
is implementation specific, and is beyond the scope of this document.
ANNEX C - FC Frame Format
All FC frames have a standard format much like LAN's 802.x
protocols. However, the exact size of each frame varies depending on
the size of the variable fields. The size of the variable field
ranges from 0 to 2112-bytes as shown in the FC Frame Format in
figure 11 resulting in the minimum size FC Frame of 36 bytes and the
maximum size FC frame of 2148 bytes. Valid Fibre Channel frame
lengths are always a multiple of four bytes.
Rajagopal, et al. Standards Track [Page 36]
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+------+--------+-----------+----//-------+------+------+
| SOF |Frame |Optional | Frame | CRC | EOF |
| (4B) |Header |Header | Payload | (4B) | (4B) |
| |(24B) |<----------------------->| | |
| | | Data Field = (0-2112B) | | |
+------+--------+-----------+----//-------+------+------+
Fig. 11 FC Frame Format
SOF and EOF Delimiters
On an FC link, Start-of-Frame (SOF) and End-Of-Frame (EOF) are
called Ordered Sets and are sent as special words constructed from
the 8B/10B comma character (K28.5) followed by three additional 8B/
10B data characters making them uniquely identifiable in the data
stream.
On an FC link the SOF delimiter serves to identify the beginning of
a frame and prepares the receiver for frame reception. The SOF
contains information about the frame's Class of Service, position
within a sequence, and in some cases, connection status.
The EOF delimiter identifies the end of the frame and the final
frame of a sequence. In addition, it serves to force the running
disparity to negative. The EOF is used to end the connection in
connection-oriented classes of service.
It is therefore important to preserve the information conveyed by
the delimiters across the IP-based network, so that the receiving
FCIP Entity can correctly reconstruct the FC frame in its original
SOF and EOF format before forwarding it to its ultimate FC
destination on the FC link.
When an FC frame is encapsulated and sent over a byte-oriented
interface, the SOF and EOF delimiters are represented as sequences
of four consecutive bytes, which carry the equivalent Class of
Service and frame termination information as the FC ordered sets.
The representation of SOF and EOF in an encapsulation FC frame is
described in FC Frame Encapsulation [23].
Frame Header
The FC Frame Header is transparent to the FCIP Entity. The FC Frame
Header is 24 bytes long and has several fields that are associated
with the identification and control of the payload. Current FC
Standards allow up to 3 Optional Header fields [6]:
- Network_Header (16-bytes)
Rajagopal, et al. Standards Track [Page 37]
Internet-Draft Fibre Channel Over TCP/IP (FCIP) June, 2001
- Association_Header (32-bytes)
- Device_Header (up to 64-bytes).
Frame Payload
The FC Frame Payload is transparent to the FCIP Entity. An FC
application level payload is called an Information Unit at the FC-4
Level. This is mapped into the Frame Payload of the FC Frame. A
large Information Unit is segmented using a structure consisting of
FC Sequences. Typically, a Sequence consists of more than one FC
frame. FCIP does not maintain any state information regarding the
relationship of frames within a FC Sequence.
CRC
The FC CRC is 4 bytes long and uses the same 32-bit polynomial used
in FDDI and is specified in ANSI X3.139 Fiber Distributed Data
Interface. This CRC value is calculated over the entire FC header
and the FC payload; it does not include the SOF and EOF delimiters.
Note: When FC frames are encapsulated into FCIP frames, the FC frame
CRC is untouched by the FCIP Entity.
ANNEX D - FCIP Requirements on an FC Entity
The capabilities that FCIP requires of an FC Entity include:
1) The FC Entity must deliver FC frames to the correct FCIP Data
Engine (in the correct FCIP Link Endpoint) and forward FC Frames
from FCIP Data Engine(s) to the FC Fabric.
2) The only delivery ordering guarantee provided by FCIP is
correctly ordered delivery of FC Frames between a pair of FCIP
Data Engines. FCIP expects the FC Entity to implement all other
FC Frame delivery ordering requirements.
3) The FC Entity must support the FCIP Entity in the processing of
incoming connect requests by deciding to accept a connect request.
4) The FC Entity may generate connect and terminate requests.
5) The FC Entity may instruct the FCIP Entity regarding TCP
connection parameter settings and the R_A_TOV to be applied to
an FCIP Link.
6) The FC Entity may recover from connection failures.
Rajagopal, et al. Standards Track [Page 38]
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7) The FC Entity must recover from events that the FCIP Entity
cannot handle, such as:
a) loss of synchronization with FCIP Frame headers from the
Encapsulated Frame Receiver Portal requiring resetting the
TCP connection,
b) additional examples, TBD
8) The FC Entity must work cooperatively with the FCIP Entity to
manage flow control problems in either the IP Network or FC
Fabric.
9) The FC Entity may test for failed TCP connections.
10) TBD support for dynamic discovery
11) TBD support for security
12) TBD support for connection QoS features
13) TBD support for monitoring
Note that the Fibre Channel standards MUST be consulted for a
complete understanding of the requirements placed on an FC Entity.
ANNEX E - FC-BB-2 Inputs
This annex contains text from previous FCIP drafts that, because of
the new model structure, probably belongs in FC-BB-2 [4]. As soon as
the correctness of this annex is agreed, its contents will be
transferred to a T11 document do be used in the development of FC-BB-
2.
No attempt has been made to rewrite this text for inclusion in an
T11 standards, so it should be considered a guide to T11 content no
a specification.
All section references in this annex come from draft-ietf-ips-
fcovertcpip-02.txt. When only parts of a section are included here,
"{partial}" is appended to the section title.
4.3 FCIP's Interaction with FC and TCP {partial}
Since FC Primitive Signals and Primitive Sequences are not exchanged
between FCIP devices, there may be times when an FC frame is lost
within the IP network. When this event occurs it is the
responsibility of the communicating FC devices to detect and correct
the errors based on the features defined in FC-FS [6]. The FCIP
devices MAY choose not to generate Fibre Channel's F_BSY or F_RJT
Rajagopal, et al. Standards Track [Page 39]
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frames or otherwise participate in FC frame recovery.
Note that the order of the FC Frames sent by the Encapsulated Frame
Transmitter MAY not be the same as the order sent by the source FC
End Node. This is due to the fact that some types of FC login allow
FC Frames to be re-ordered in the FC Fabric before reaching the FC
Receiver Port.
5.3 TCP Connection Management
In order to realize a Virtual ISL between two FC end-points, an FCIP
Device establishes TCP connection(s) with its peer FCIP Device. In
order to achieve better TCP aggregate throughput properties in the
face of packet losses, a pair of peer FCIP devices MAY use multiple
TCP connections between them, and use appropriate policies for
mapping FC frames to these connections. It may also be useful to
assign a pool of connections for transmission of high priority and
control messages (e.g., Class F messages) on connections so they do
not encounter "head of line" blocking behind Class 2 or Class 3
traffic. The use of multiple connections and policies for
distributing frames on these connections are described in section 5.5.
A Virtual ISL and the two FCIP Device endpoints that are involved
are operational only after the first TCP connection is established.
The sequence of operations performed in order to establish a Virtual
ISL is as follows.
1) The FCIP device initializes its local resources to enable it to
listen to TCP connection requests.
2) The FCIP device discovers the FCIP device endpoints that it can
establish a virtual ISL. The result of the discovery SHALL be,
at the minimum, the IP address and the TCP port of the peer
endpoint. The discovery process MAY rely on administrative
configuration or on services such as SLP or iSNS (TBD). (Needs
to have its own section eventually).
3) The FCIP device endpoint SHALL exchange security context and
authenticate itself to the peer endpoint. The use of security
context is explained in section 8.
4) After connection establishment, FCIP devices use the FCIP frame
encapsulation defined in FC Frame Encapsulation [23] and in
section 6.6.1 of this document.
5) At this point the FCIP device endpoint SHALL exchange Fibre
Channel port initialization frames (SW_ILS) to enable and
identify port operation. Port state machine and initialization
Rajagopal, et al. Standards Track [Page 40]
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are described in FC-SW-2 [5].
6) An FCIP device operates in E-port or B-Port mode. When operating
in E-Port mode, normal FC-SW2 FSPF messages are exchanged and
the switch port becomes operational.
7) For computing the link cost of the ISL, the following formula
SHALL be used: <TBD>.
In certain deployments, a single FCIP device endpoint MAY establish
virtual ISLs with multiple FCIP device endpoints. In this situation,
the FCIP device endpoint SHALL manage TCP operational parameters
independently for each ISL. Also, the FCIP Device Endpoint SHALL
perform the E_Port or B_Port initialization independently, for each
connection.
5.4.1 Determining loss of connectivity {partial}
In order to facilitate faster detection of loss of connectivity, FC
Switches MAY process the Hello (HLO) SW_ILS request through a pair
of FCIP devices.
The relationship between the HLO SW_ILS and the paired FCIP devices
is TBD.
Upon detecting a loss of connectivity, an FCIP Device SHALL
establish a new connection, or SHALL use an existing TCP connection
to the same FCIP Device endpoint. An FCIP Device SHALL NOT
retransmit an FCIP frame on the new connection. This is to ensure
exactly-once delivery semantics to the Fibre Channel endpoint.
5.5 Multiple Connection Management
A pair of FCIP device endpoints MAY establish a certain number of
TCP connections between them. Since a Virtual ISL potentially maps a
fairly large number of FC flows (where a flow is a pair of Fibre
Channel S_ID, D_ID addresses), it may not be practical to establish
a separate TCP connection for each Fibre Channel flow. In order to
address this, an implementation MAY choose to manage a pool of TCP
connections for a single Virtual ISL and map Fibre Channel flows to
TCP connections of that ISL. However, while assigning Fibre Channel
flows to TCP connections, an implementation SHALL follow the
following rules:
1) Once a Fibre Channel flow is assigned to a TCP connection within
the virtual ISL, it SHALL send all Fibre Channel frames of that
flow on that connection.
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2) When an FCIP endpoint processes any response traffic from a
particular target, the Endpoint SHALL send the response on the
same connection on which the request was sent.
3) Any class 2 ACK frames SHALL be sent on the same connection in
which the original frame was sent.
These rules are in place to honor any in-order delivery guarantees
that may have been made between the two end points of the Fibre
Channel flow.
5.6 Multi Virtual ISL Management
It is quite likely that a single switch MAY provide multiple Virtual
ISLs, all providing alternate connectivity paths between two
switches. In this situation, a switch SHALL select any of the
available ISLs for mapping a FCIP flow. In doing so, a switch MUST
follow a flow allegiance model, where a pair of Fibre Channel [S_ID,
D_ID] end points are always mapped to the same Virtual ISL.
Furthermore, switches SHALL implement a connection allegiance
policy, which ensures that the responses to particular [S_ID, D_ID]
pair is always sent back on the same Virtual ISL.
8.3 Corruption {partial}
Data corruption is detected at two different levels: TCP checksum
and Fibre Channel frame encapsulation errors. Data corruption
detected at the TCP level SHALL be recovered via TCP data recovery
mechanisms. The recovery for Fibre Channel frame errors is described
below. The TCP and Fibre Channel frame recovery operations are
performed independently.
Fibre Channel frame errors and the expected resolution of those
errors are described below:
a) Incoming frames on the FC Receiver Port SHALL be verified for
correct header, proper format, valid length and valid CRC.
Frames having incorrect headers or CRC SHALL be discarded or
processed in accordance with the rules for the particular type
of FC Port.
b) All frames transmitted by the Encapsulated Frame Transmitter
shall be valid FC Encapsulations of valid FC frames with correct
TCP check sums on the correct TCP/IP connection.
e) The FC frames contained in incoming encapsulated frames on the
FC Receiver Port SHALL be verified for a valid header, proper
content, proper SOF and EOF values, and valid length. FC frames
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that are not valid according to those checks SHALL be managed
according to the following rules.
1) The frame may be discarded before being transmitted by the
FC Transmitter Port.
2) The frame may be transmitted in whole or in part by the FC
Transmitter Port and ended with an EOF indicating that the
content of the frame is invalid.
f) Any encapsulated frame received by the Encapsulated Frame
Receiver that has an invalid Fibre Channel CRC shall be managed
according to the following rules.
1) The frame may be transmitted unchanged by the FC Transmitter
Port. The frame will be discarded by the receiving FC Port
because of invalid CRC.
2) The frame may be discarded before being transmitted by the
FC Transmitter Port.
3) The frame may be transmitted in whole or in part by the FC
Transmitter Port and ended with an EOF indicating that the
content of the frame is invalid. The FC encapsulation header
Frame Length field MUST correctly specify the transmitted
frame length.
8.4 Timeouts {partial}
Fibre Channel has two important timeouts to consider in FCIP. These
are: E_D_TOV, and R_A_TOV.
E_D_TOV determines the life of an individual Fibre Channel frame in
any particular fabric element. The effects of E_D_TOV on the fabric
as a whole are typically cumulative since each fabric element
contains it's own E_D_TOV timers for any frame received.
R_A_TOV determines the life of an individual Fibre Channel frame in
the fabric as a whole. For a fabric, R_A_TOV implies that no
particular frame will remain in (and thus be emitted from) the
fabric after the timer expires.
10.1 Flow control on FC network
When the Fibre channel traffic is encapsulated over TCP
connection(s), the FCIP device needs to ensure that the TCP
connections can handle the frame arrival rate from FC Fabric. This
MAY require FCIP device to use Buffer-to-Buffer flow control (see FC-
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FS [6]) on its Fibre Channel port(s) to control the frame arrival
rate.
Rajagopal, et al. Standards Track [Page 44]
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