Request for Comments: 3831 Cisco Systems
Category: Standards Track July 2004
Transmission of IPv6 Packets over Fibre Channel
Status of this Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2004).
Abstract
This document specifies the way of encapsulating IPv6 packets over
Fibre Channel, and the method of forming IPv6 link-local addresses
and statelessly autoconfigured addresses on Fibre Channel networks.
Table Of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Summary of Fibre Channel . . . . . . . . . . . . . . . . . . . 3
2.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Identifiers and Login. . . . . . . . . . . . . . . . . . 3
2.3. FC Levels and Frame Format . . . . . . . . . . . . . . . 4
2.4. Sequences and Exchanges . . . . . . . . . . . . . . . . 5
3. IPv6 Capable Nx_Ports. . . . . . . . . . . . . . . . . . . . . 6
4. IPv6 Encapsulation . . . . . . . . . . . . . . . . . . . . . . 6
4.1. FC Sequence Format . . . . . . . . . . . . . . . . . . . 6
4.2. FC Classes of Service. . . . . . . . . . . . . . . . . . 8
4.3. FC Header Code Points. . . . . . . . . . . . . . . . . . 8
4.4. FC Network_Header. . . . . . . . . . . . . . . . . . . . 9
4.5. LLC/SNAP Header. . . . . . . . . . . . . . . . . . . . . 9
4.6. Bit and Byte Ordering. . . . . . . . . . . . . . . . . . 9
5. Maximum Transfer Unit. . . . . . . . . . . . . . . . . . . . . 10
6. Stateless Address Autoconfiguration. . . . . . . . . . . . . . 10
6.1. IPv6 Interface Identifier and Address Prefix . . . . . . 10
6.2. Generating an Interface ID from a Format 1
N_Port_Name. . . . . . . . . . . . . . . . . . . . . . . 11
6.3. Generating an Interface ID from a Format 2
N_Port_Name. . . . . . . . . . . . . . . . . . . . . . . 12
6.4. Generating an Interface ID from a Format 5
N_Port_Name. . . . . . . . . . . . . . . . . . . . . . . 13
6.5. Generating an Interface ID from an EUI-64
mapped N_Port_Name . . . . . . . . . . . . . . . . . . . 14
7. Link-Local Addresses . . . . . . . . . . . . . . . . . . . . . 15
8. Address Mapping for Unicast. . . . . . . . . . . . . . . . . . 15
9. Address Mapping for Multicast. . . . . . . . . . . . . . . . . 16
10. Sequence Management. . . . . . . . . . . . . . . . . . . . . . 17
11. Exchange Management. . . . . . . . . . . . . . . . . . . . . . 17
12. Security Considerations. . . . . . . . . . . . . . . . . . . . 18
13. Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . . 18
14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18
14.1. Normative References. . . . . . . . . . . . . . . . . . 18
14.2. Informative References. . . . . . . . . . . . . . . . . 19
A. Transmission of a Broadcast FC Sequence over FC Topologies . . 20
B. Validation of the <N_Port_Name, N_Port_ID> mapping . . . . . . 21
C. Fibre Channel Bit and Byte Numbering Guidance. . . . . . . . . 22
Author’s Address . . . . . . . . . . . . . . . . . . . . . . . . . 23
Full Copyright Statement . . . . . . . . . . . . . . . . . . . . . 24
1. Introduction
Fibre Channel (FC) is a high speed serial interface technology that
supports several Upper Layer Protocols including Small Computer
System Interface (SCSI) and IPv4 as specified in [IPFC].
The purpose of this document is to specify a way of encapsulating IP
version 6 [IPv6] over Fibre Channel and to describe a method of
forming IPv6 link-local addresses [AARCH] and statelessly
autoconfigured addresses on Fibre Channel networks. This document
also describes the content of the Source/Target Link-layer Address
option used in Neighbor Discovery [DISC] when the messages are
transmitted on a Fibre Channel network.
Warning to readers familiar with Fibre Channel: both Fibre Channel
and IETF standards use the same byte transmission order. However,
the bit numbering is different. See Appendix C for guidance.
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 [KEYWORDS].
2. Summary of Fibre Channel
2.1. Overview
Fibre Channel (FC) is a gigabit speed network technology primarily
used for Storage Networking. Fibre Channel is standardized in the
T11 Technical Committee of the InterNational Committee for
Information Technology Standards (INCITS), an American National
Standard Institute (ANSI) accredited standards committee.
Fibre Channel devices are called Nodes. Each Node has one or more
Ports that connect to Ports of other devices. Fibre Channel may be
implemented using any combination of the following three topologies:
- a point-to-point link between two Ports;
- a set of Ports interconnected by a switching network called a
Fabric, as defined in [FC-FS];
- a set of Ports interconnected with a loop topology, as defined in
[FC-AL-2].
A Node Port is more precisely called an N_Port. A Node Port that is
capable of operating in a loop topology using the loop specific
protocols is designated as an NL_Port. The term Nx_Port is used to
generically indicate these two kinds of Node Port.
A Fabric Port is more precisely called an F_Port. A Fabric Port that
is capable of operating in a loop topology using the loop specific
protocols is designated as an FL_Port. The term Fx_Port is used to
generically indicate these two kinds of Fabric Port.
From an IPv6 point of view, a Fibre Channel network, built with any
combination of the FC topologies described above, is an IPv6 Link
[IPv6]. IPv6-capable Nx_Ports are what [IPv6] calls Interfaces.
2.2. Identifiers and Login
Fibre Channel entities are identified by permanent 64 bit long
Name_Identifiers. [FC-FS] defines several formats of
Name_Identifiers. The value of the first four bits defines the
format of a Name_Identifier. These names are referred to in a more
precise manner as follows:
- an Nx_Port’s Name_Identifier is called N_Port_Name;
- an Fx_Port’s Name_Identifier is called F_Port_Name;
- a Node’s Name_Identifier is called Node_Name;
- a Fabric’s Name_Identifier is called Fabric_Name.
An Nx_Port connected to a Fibre Channel network is associated with
two identifiers, its permanent N_Port_Name and a volatile 24 bit
address called N_Port_ID. The N_Port_Name is used to identify the
Nx_Port, while the N_Port_ID is used for communications among
Nx_Ports.
Each Nx_Port acquires an N_Port_ID from the Fabric by performing a
process called Fabric Login or FLOGI. The FLOGI process is used also
to negotiate several communications parameters between the Nx_Port
and the Fabric, such as the receive data field size, which determines
the maximum size of the Fibre Channel frames that may be transferred
between the Nx_Port and the Fabric.
Before effective communication may take place between two Nx_Ports,
they must complete a process called Port Login or PLOGI. The PLOGI
process provides each Nx_Port with the other Nx_Port’s N_Port_Name,
and negotiates several communication parameters, such as the receive
data field size, which determines the maximum size of the Fibre
Channel frames that may be transferred between the two Nx_Ports.
Both Fabric Login and Port Login may be explicit, i.e., performed
using specific FC control messages (called Extended Link Services or
ELS), or implicit, in which the parameters are specified by
configuration or other methods.
2.3. FC Levels and Frame Format
[FC-FS] describes the Fibre Channel protocol using 5 different
levels. The FC-2 and FC-4 levels are relevant for this
specification. The FC-2 level defines the FC frame format, the
transport services, and control functions necessary for information
transfer. The FC-4 level supports Upper Level Protocols, such as
IPv4, IPv6 or SCSI. The Fibre Channel frame format is depicted in
figure 1.
+-----+-----------+-----------+--------//-------+-----+-----+
| | | Data Field | | |
| SOF | FC Header |<--------------------------->| CRC | EOF |
| | | Optional | Frame | | |
| | | Header(s) | Payload | | |
+-----+-----------+-----------+--------//-------+-----+-----+
Fig. 1: Fibre Channel Frame Format
The Start of Frame (SOF) and End of Frame (EOF) are special FC
transmission words that act as frame delimiters. The CRC is 4 octets
long and uses the same 32-bit polynomial used in FDDI.
The FC Header is 24 octets long and contains several fields
associated with the identification and control of the Data Field.
The Data Field is of variable size, ranging from 0 to 2112 octets,
and includes the user data in the Frame Payload field, and Optional
Headers. The currently defined Optional Headers are:
- ESP_Header;
- Network_Header;
- Association_Header;
- Device_Header.
The value of the SOF field determines the FC Class of service
associated with the frame. Five Classes of service are specified in
[FC-FS]. They are distinguished primarily by the method of flow
control between the communicating Nx_Ports and by the level of data
integrity provided. A given Fabric or Nx_Port may support one or
more of the following Classes of service:
- Class 1: Dedicated physical connection with delivery confirmation;
- Class 2: Frame multiplexed service with delivery confirmation;
- Class 3: Datagram service;
- Class 4: Fractional bandwidth;
- Class 6: Reliable multicast via dedicated connections.
2.4. Sequences and Exchanges
An application level payload such as IPv6 is called Information Unit
at the FC-4 level of Fibre Channel. Each FC-4 Information Unit is
mapped to an FC Sequence by the FC-2 level. An FC Sequence consists
of one or more FC frames related by the value of the Sequence_ID
(SEQ_ID) field of the FC Header.
The maximum data that may be carried by an FC frame is 2112 octets.
The maximum usable frame size depends on the Fabric and Nx_Port
implementations and is negotiated during the Login process. Whenever
an Information Unit to be transmitted exceeds this value, the FC-2
level segments it into multiple FC frames, sent as a single Sequence.
The receiving Nx_Port reassembles the Sequence of frames and delivers
a reassembled Information Unit to the FC-4 level. The Sequence Count
(SEQ_CNT) field of the FC Header may be used to ensure frame
ordering.
Multiple Sequences may be related together as belonging to the same
FC Exchange. The Exchange is a mechanism used by two Nx_Ports to
identify and manage an operation between them. The Exchange is
opened when the operation is started between the two Nx_Ports, and
closed when the operation ends. FC frames belonging to the same
Exchange are related by the value of the Exchange_ID fields in the FC
Header. An Originator Exchange_ID (OX_ID) and a Responder
Exchange_ID (RX_ID) uniquely identify the Exchange.
3. IPv6 Capable Nx_Ports
This specification requires an IPv6 capable Nx_Port to have the
following properties:
- The format of its N_Port_Name MUST be one of 0x1, 0x2, 0x5, 0xC,
0xD, 0xE, 0xF (see section 6.1). IPv6 support for other
Name_Identifier formats is outside the scope of this
specification;
- It MUST support Class 3;
- It MUST support continuously increasing SEQ_CNT [FC-FS];
- It MUST be able to transmit and receive an FC-4 Information Unit
at least 1304 octets long;
- It SHOULD support a receive data field size for Device_Data FC
frames of at least 1024 octets.
4. IPv6 Encapsulation
4.1. FC Sequence Format
An IPv6 packet is mapped to an Information Unit at the FC-4 level of
Fibre Channel, which in turn is mapped to an FC Sequence by the FC-2
level. An FC Information Unit containing an IPv6 packet MUST carry
the FC Network_Header [FC-FS] and the LLC/SNAP header [IEEE-LLC],
resulting in the FC Information Unit format depicted in figure 2.
+---------------+---------------+---------------+---------------+
| |
+- -+
| Network_Header |
+- (16 octets) -+
| |
+- -+
| |
+---------------+---------------+---------------+---------------+
| LLC/SNAP header |
+- (8 octets) -+
| |
+---------------+---------------+---------------+---------------+
| |
+- -+
/ IPv6 Packet /
/ /
+- -+
| |
+---------------+---------------+---------------+---------------+
Fig. 2: FC Information Unit Mapping an IPv6 Packet
The FC ESP_Header [FC-FS] MAY be used to secure the FC frames
composing the FC Sequence. [AH] or [ESP] may be used to provide
security at the IPv6 layer. Other types of FC Optional Header MUST
NOT be used in an IPv6 FC Sequence.
Typically, a Sequence consists of more than one frame. Only the
first frame of the Sequence MUST include the FC Network_Header and
the LLC/SNAP header. The other frames MUST NOT include them, as
depicted in figure 3.
First Frame of an IPv6 FC Sequence
+-----------+-------------------+-----------------+-------//--------+
| FC Header | FC Network_Header | LLC/SNAP header | First chunk of |
| | | | the IPv6 Packet |
+-----------+-------------------+-----------------+-------//--------+
Subsequent Frames of an IPv6 FC Sequence
+-----------+-----------------//------------------+
| FC Header | Additional chunk of the IPv6 Packet |
+-----------+----------------//-------------------+
Fig. 3: Optional Headers in an IPv6 FC Sequence
4.2. FC Classes of Service
This specification uses FC Class 3. IPv6 packets carrying Neighbor
Discovery [DISC] messages MUST be encapsulated in Class 3 FC frames.
Other IPv6 packets SHOULD use Class 3 as well. The use of other
Classes of service is outside the scope of this specification.
4.3. FC Header Code Points
The fields of the Fibre Channel Header are depicted in figure 4. The
D_ID and S_ID fields contain respectively the destination N_Port_ID
and the source N_Port_ID. To encapsulate IPv6 over Fibre Channel the
following code points MUST be used:
- R_CTL: 0x04 (Device_Data frame with Unsolicited Data Information
Category [FC-FS])
- TYPE: 0x05 (IP over Fibre Channel)
- CS_CTL/Prio: 0x0
- DF_CTL: 0x20 (Network_Header) for the first FC frame of an IPv6
Sequence, 0x00 for the following FC frames. If the FC ESP_Header
is used, then 0x60 for the first FC frame of an IPv6 Sequence,
0x40 for the following FC frames.
- F_CTL, SEQ_ID, SEQ_CNT, OX_ID, RX_ID, Parameter: see section 10,
section 11, and [FC-FS] for additional requirements.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| R_CTL | D_ID |
+---------------+---------------+---------------+---------------+
| CS_CTL/Prio | S_ID |
+---------------+---------------+---------------+---------------+
| TYPE | F_CTL |
+---------------+---------------+---------------+---------------+
| SEQ_ID | DF_CTL | SEQ_CNT |
+---------------+---------------+---------------+---------------+
| OX_ID | RX_ID |
+---------------+---------------+---------------+---------------+
| Parameter |
+---------------+---------------+---------------+---------------+
Fig. 4: FC Header Format
4.4. FC Network_Header
The fields of the FC Network_Header are depicted in figure 5. For
use with IPv6 the N_Port_Names formats MUST be one of 0x1, 0x2, 0x5,
0xC, 0xD, 0xE, 0xF. IPv6 support for other Name_Identifier formats
is outside the scope of this specification.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+- Destination N_Port_Name -+
| |
+---------------------------------------------------------------+
| |
+- Source N_Port_Name -+
| |
+---------------------------------------------------------------+
Fig. 5: FC Network_Header Format
4.5. LLC/SNAP Header
The fields of the LLC/SNAP Header [IEEE-LLC] are depicted in figure
6. To encapsulate IPv6 over Fibre Channel the following code points
MUST be used:
- DSAP: 0xAA
- SSAP: 0xAA
- CTRL: 0x03
- OUI: 0x00-00-00
- PID: 0x86-DD
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DSAP | SSAP | CTRL | OUI |
+---------------+---------------+---------------+---------------+