Transmission of IPv6 Packets Over FDDI (RFC2019)
Original Publication Date: 1996-Oct-01
Included in the Prior Art Database: 2019-Feb-15
Internet Society Requests For Comment (RFCs)
This memo specifies the MTU and frame format for transmission of IPv6 [IPV6] packets on FDDI networks, including a method for MTU determination in the presence of 802.1d bridges to other media. [STANDARDS-TRACK]
Network Working Group M. Crawford Request for Comments: 2019 Fermilab Category: Standards Track October 1996
A Method for the Transmission of IPv6 Packets over FDDI Networks
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.
This memo specifies the MTU and frame format for transmission of IPv6 [IPV6] packets on FDDI networks, including a method for MTU determination in the presence of 802.1d bridges to other media. It also specifies the method of forming IPv6 link-local addresses on FDDI networks and the content of the Source/Target Link-layer Address option used the the Router Solicitation, Router Advertisement, Neighbor Solicitation, and Neighbor Advertisement messages described in [DISC], when those messages are transmitted on an FDDI network.
Maximum Transmission Unit
FDDI permits a frame length of 4500 octets (9000 symbols), including at least 22 octets (44 symbols) of Data Link encapsulation when long-format addresses are used. Subtracting 8 octets of LLC/SNAP header, this would, in principle, allow the IPv6 packet in the Information field to be up to 4470 octets. However, it is desirable to allow for the variable sizes and possible future extensions to the MAC header and frame status fields. The default MTU size for IPv6 packets on an FDDI network is therefore 4352 octets. This size may be reduced by a Router Advertisement [DISC] containing an MTU option which specifies a smaller MTU, or by manual configuration of a smaller value on each node. If a Router Advertisement is received with an MTU option specifying an MTU larger than the default or the manually configured value, that MTU option may be logged to system management but must be otherwise ignored.
For purposes of this document, information received from DHCP is considered "manually configured".
Crawford Standards Track [Page 1]
RFC 2019 Transmission of IPv6 Packets Over FDDI October 1996
FDDI provides both synchronous and asynchronous transmission, with the latter class further subdivided by the use of restricted and unrestricted tokens. Only asynchronous transmission with unrestricted tokens is required for FDDI interoperability. Accordingly, IPv6 packets shall be sent in asynchronous frames using unrestricted tokens. The robustness principle dictates that nodes should be able to receive synchronous frames and asynchronous frames sent using restricted tokens.
IPv6 packets are transmitted in LLC/SNAP frames, using long-format (48 bit) addresses. The data field contains the IPv6 header and payload and is followed by the FDDI Frame Check Sequence, Ending Delimiter, and Frame Status symbols.
+-------+ ^ | FC | | +-------+-------+-------+-------+-------+----...