Transmission of IPv6 Packets over Fibre Channel
obsoleted by
- rfc-4338 — Transmission of IPv6, IPv4, and Address Resolution Protocol (ARP) Packets over Fibre Channel
Extracted elements (26)
IPv6 over FC does not use the FC Name Server, so FC soft zoning (Name Server masking) provides no security boundary for IPv6 traffic. This is a non-obvious limitation of applying FC zoning to IPv6 networks.
IPv6 over Fibre Channel uses FC Class 3 (datagram service) rather than connection-oriented classes because it provides the connectionless semantics needed for IP traffic without the overhead of dedicated physical connections or delivery confirmation.
The default MTU of 65280 octets far exceeds typical Internet message sizes, so implementations SHOULD implement Path MTU Discovery or maintain different MTU values for on-link and off-link destinations to avoid fragmentation in routed environments.
Both Fibre Channel and IETF standards use the same byte transmission order, but the bit numbering is different. Implementers familiar with FC must account for this difference when reading RFC wire-format diagrams.
IPv6 Exchanges SHOULD NOT be terminated by Logout, since Logout may terminate active Exchanges on other FC-4 protocols sharing the same port.
When mixed media (e.g., Ethernet and Fibre Channel) are bridged together, the smallest MTU of all media must be advertised by routers in MTU options; if no routers are present, each node connected to higher-MTU media must be manually configured.
All best-effort IPv6 multicast packets MUST be mapped to FC Sequences addressed to the broadcast N_Port_ID 0xFF-FF-FF, with the Destination N_Port_Name in the FC Network_Header set to 0x10-00-FF-FF-FF-FF-FF-FF.
An FC Information Unit containing an IPv6 packet MUST carry the FC Network_Header and the LLC/SNAP header. Only the first frame of the Sequence MUST include these headers; subsequent frames MUST NOT include them.
An IPv6-capable Nx_Port MUST support Class 3 FC service, MUST support continuously increasing SEQ_CNT, and its N_Port_Name format MUST be one of 0x1, 0x2, 0x5, 0xC, 0xD, 0xE, or 0xF.
FC Sequences are REQUIRED to be non-streamed, and an Nx_Port supporting IPv6 is REQUIRED to use continuously increasing SEQ_CNT. Each Exchange MUST start with SEQ_CNT=0 and every subsequent frame MUST increment SEQ_CNT by one.
For IPv6, Exchanges MUST NOT transfer Sequence Initiative because they are used in unidirectional mode; the Sequence Initiative bit in F_CTL MUST be set to 0. Each Nx_Port MUST have a dedicated Exchange for sending and receiving data to/from each peer.
For the LLC/SNAP header encapsulating IPv6 over FC, the following code points MUST be used: DSAP=0xAA, SSAP=0xAA, CTRL=0x03, OUI=0x00-00-00, PID=0x86-DD.
IPv6 packets carrying Neighbor Discovery messages MUST be encapsulated in Class 3 FC frames. Other IPv6 packets SHOULD use Class 3 as well.
Stateless address autoconfiguration MUST be performed as specified in RFC 2462. An IPv6 Address Prefix used for stateless autoconfiguration of an Nx_Port MUST have a length of 64 bits.
The default MTU for IPv6 over Fibre Channel is 65280 octets, but the MTU MUST NOT be lower than 1280 octets as required by IPv6. Router Advertisements specifying an MTU larger than 65280 MUST be ignored.
To encapsulate IPv6 over Fibre Channel, specific FC Header code points MUST be used: R_CTL=0x04, TYPE=0x05, CS_CTL/Prio=0x0, and DF_CTL=0x20 for the first frame (0x60 if ESP_Header used) and 0x00 for subsequent frames.
Address mapping for IPv6 unicast requires both the non-volatile 64-bit N_Port_Name and the volatile 24-bit N_Port_ID. An Nx_Port MUST validate the N_Port_Name/N_Port_ID mapping after FC link interruption events such as LIP or NOS/OLS.
An Nx_Port supporting IPv6 MUST be able to map a received broadcast Class 3 Device_Data FC frame to an implicit Port Login context to handle IPv6 multicast packets; the receive data field size of this implicit Port Login MUST be the same across all Nx_Ports on the same Fabric.
The IPv6 Interface Identifier for an Nx_Port is derived from the EUI-64 address mapped from the N_Port_Name, with the Universal/Local bit complemented. Formats 0x1, 0x2, and 0x5 produce locally-scoped identifiers; EUI-64 mapped formats (0xC-0xF) produce globally-scoped identifiers.
The IPv6 link-local address for an Nx_Port is formed by appending the 64-bit Interface Identifier to the prefix FE80::/64.
IPv6 does not introduce additional security concerns beyond those already in Fibre Channel. FC soft zoning (Name Server masking) does not work for IPv6 traffic since IPv6 over FC bypasses the FC Name Server. The FC ESP_Header may be used to secure FC frames, and IPsec (AH/ESP) may be used at the IPv6 layer.
The <N_Port_Name, N_Port_ID> mapping must be validated after FC link interruptions. After LIP in loop topology or NOS/OLS in point-to-point, address validation via ADISC (private loop) or FLOGI (fabric/public loop) is required; if addresses changed, all active Exchanges must be torn down and ports logged out.
The FC Header is 24 octets and contains R_CTL, D_ID, CS_CTL/Prio, S_ID, TYPE, F_CTL, SEQ_ID, DF_CTL, SEQ_CNT, OX_ID, RX_ID, and Parameter fields used for identification and control of the Data Field.
The FC Information Unit for an IPv6 packet consists of: FC Network_Header (16 octets) followed by LLC/SNAP header (8 octets) followed by the IPv6 packet payload, carried in the first FC frame only.
The FC Network_Header contains a Destination N_Port_Name (8 octets) and Source N_Port_Name (8 octets), totaling 16 octets. N_Port_Name formats MUST be one of 0x1, 0x2, 0x5, 0xC, 0xD, 0xE, or 0xF.
The Source/Target Link-layer Address option for Fibre Channel contains: Type (1 octet), Length=2 (1 octet, in 8-octet units), Reserved (2 octets), N_Port_Name (8 octets), Reserved (1 octet), and N_Port_ID (3 octets).