As per Relevance of the word crawford, we have this rfc below:
Network Working Group M.
Request for Comments: 2019
Category: Standards Track October 1996
A Method for the Transmission of IPv6 Packets over FDDI
Status of this
This document specifies an Internet standards track protocol for
Internet community, and requests discussion and suggestions
improvements. Please refer to the current edition of the "
Official Protocol Standards" (STD 1) for the standardization
and status of this protocol. Distribution of this memo is unlimited
This memo specifies the MTU and frame format for transmission of IPv
[IPV6] packets on FDDI networks, including a method for
determination in the presence of 802.1d bridges to other media.
also specifies the method of forming IPv6 link-local addresses
FDDI networks and the content of the Source/Target Link-layer
option used the the Router Solicitation, Router Advertisement
Neighbor Solicitation, and Neighbor Advertisement messages
in [DISC], when those messages are transmitted on an FDDI network
Maximum Transmission
FDDI permits a frame length of 4500 octets (9000 symbols),
at least 22 octets (44 symbols) of Data Link encapsulation
long-format addresses are used. Subtracting 8 octets of LLC/
header, this would, in principle, allow the IPv6 packet in
Information field to be up to 4470 octets. However, it is
to allow for the variable sizes and possible future extensions to
MAC header and frame status fields. The default MTU size for IPv
packets on an FDDI network is therefore 4352 octets. This size
be reduced by a Router Advertisement [DISC] containing an MTU
which specifies a smaller MTU, or by manual configuration of
smaller value on each node. If a Router Advertisement is
with an MTU option specifying an MTU larger than the default or
manually configured value, that MTU option may be logged to
management but must be otherwise ignored
For purposes of this document, information received from DHCP
considered "manually configured".
Crawford Standards Track [Page 1]
RFC 2019 Transmission of IPv6 Packets Over FDDI October 1996
Frame
FDDI provides both synchronous and asynchronous transmission,
the latter class further subdivided by the use of restricted
unrestricted tokens. Only asynchronous transmission
unrestricted tokens is required for FDDI interoperability
Accordingly, IPv6 packets shall be sent in asynchronous frames
unrestricted tokens. The robustness principle dictates that
should be able to receive synchronous frames and asynchronous
sent using restricted tokens
IPv6 packets are transmitted in LLC/SNAP frames, using long-
(48 bit) addresses. The data field contains the IPv6 header
payload and is followed by the FDDI Frame Check Sequence,
Delimiter, and Frame Status symbols
+-------+ ^
| FC | |
+-------+-------+-------+-------+-------+-------+ |
| Destination FDDI address | |
+-------+-------+-------+-------+-------+-------+
| Source FDDI address |
+-------+-------+-------+-------+-------+-------+ |
| DSAP | SSAP | CTL | OUI | |
+-------+-------+-------+-------+-------+-------+ |
| Ethertype |
+-------+-------+-------+-------+-------+------+------+
| IPv6 header and payload ... /
+-------+-------+-------+-------+-------+------+------+
FDDI Header Fields
FC The Frame Code must be in the range 50 to 57 hexadecimal
inclusive, with the three low order bits indicating
frame priority. The Frame Code should be in the range 51
57 hexadecimal, inclusive, for reasons given in the
section
DSAP, SSAP Both the DSAP and SSAP fields shall contain the value
hexadecimal, indictating SNAP encapsulation
CTL The Control field shall be set to 03 hexadecimal,
Unnumbered Information
OUI The Organizationally Unique Identifier shall be set
000000 hexadecimal
Crawford Standards Track [Page 2]
RFC 2019 Transmission of IPv6 Packets Over FDDI October 1996
Ethertype The ethernet protocol type ("ethertype") shall be set to
value 86DD hexadecimal
Interaction with
802.1d MAC bridges which connect different media, for
Ethernet and FDDI, have become very widespread. Some of them do IPv
packet fragmentation and/or support IPv4 Path MTU discovery [PMTU],
many others do not, or do so incorrectly. Use of IPv6 in a
mixed-media environment should not depend on support from
bridges
For correct operation when mixed media are bridged together,
smallest MTU of all the media must be advertised by routers in an
option. If there are no routers present, this MTU must be
configured in each node which is connected to a medium with
default MTU. Multicast packets on such a bridged network must not
larger than the smallest MTU of any of the bridged media. Often,
subnetwork topology will support larger unicast packets to
exchanged between certain pairs of nodes. To take advantage
high-MTU paths when possible, nodes transmitting IPv6 on FDDI
implement the following simple mechanism for "FDDI
detection".
A node which implements FDDI adjacency detection and has it
on an FDDI interface must set a non-zero LLC priority in all
Advertisement, Neighbor Solicitation and, if applicable,
Advertisement frames transmitted on that interface. (In IEEE 802
language, the user_priority parameter of the M_UNITDATA.
primitive must not be zero.) If FDDI adjacency detection has
disabled on an FDDI interface, the priority field of those
must be zero
Note that an IPv6 frame which originated on an Ethernet, or
an Ethernet, before being translated by an 802.1d bridge
delivered to a node's FDDI interface will have zero in the
field, as required by [BRIDGE]. (There's a fine point here:
conforming bridge may provide a management-settable Outbound
Priority parameter for each port. However, the author is unaware
any product that provides this optional capability and, in any case
the default value for the parameter is zero.)
Crawford Standards Track [Page 3]
RFC 2019 Transmission of IPv6 Packets Over FDDI October 1996
If a node N1 receives, in an FDDI frame with a non-zero LLC priority
a valid Router Advertisement, Neighbor Advertisement, or
Solicitation from a node N2, then N1 may send unicast IPv6 packets
N2 with sizes up to the default IPv6 FDDI MTU (4352 octets),
regardless of any smaller MTU configured manually or received in
Router Advertisement MTU option. N2 may be the IPv6 destination
the next hop router to the destination
Nodes implementing FDDI adjacency detection must provide
configuration option to disable the mechanism. This option may
used when a smaller MTU is desired for reasons other than mixed-
bridging. By default, FDDI adjacency detection should be enabled
The only contemplated use of the LLC priority field of the FC
is to aid in per-destination MTU determination. It would
sufficient for that purpose to require only that
Advertisements, Neighbor Advertisements, and Neighbor
sent on FDDI always have non-zero priority. However, it may
simpler or more useful to transmit all IPv6 packets on FDDI
non-zero priority
Stateless Autoconfiguration and Link-Local
The address token [CONF] for an FDDI interface is the interface'
built-in 48-bit IEEE 802 address, in canonical bit order and with
octet in the same order in which they would appear in the header
an ethernet frame. (The individual/group bit is in the first
and the OUI is in the first three octets.) A different MAC
set manually or by software should not be used as the address token
An IPv6 address prefix used for stateless autoconfiguration of
FDDI interface must be 80 bits in length
The IPv6 Link-local address [AARCH] for an FDDI interface is
by appending the interface's IEEE 802 address to the 80-bit
FE80::.
+-------+-------+-------+-------+-------+-------+------+------+
| FE 80 00 00 00 00 00 00 |
+-------+-------+-------+-------+-------+-------+------+------+
| 00 00 | FDDI Address |
+-------+-------+-------+-------+-------+-------+------+------+
Crawford Standards Track [Page 4]
RFC 2019 Transmission of IPv6 Packets Over FDDI October 1996
Address Mapping --
The procedure for mapping IPv6 addresses into FDDI link-
addresses is described in [DISC]. The Source/Target Link-
Address option has the following form when the link layer is FDDI
+-------+-------+-------+-------+-------+-------+------+------+
| Type |Length | FDDI Address |
+-------+-------+-------+-------+-------+-------+------+------+
Option fields
Type 1 for Source Link-layer address
2 for Target Link-layer address
Length 1 (in units of 8 octets).
FDDI
The 48 bit FDDI IEEE 802 address, in canonical bit order
This is the address the interface currently responds to,
may be different from the built-in address used as
address token
Address Mapping --
An IPv6 packet with a multicast destination address DST
transmitted to the FDDI multicast address whose first two octets
the value 3333 hexadecimal and whose last four octets are the
four octets of DST, ordered from more to least significant
+-------+-------+-------+-------+-------+-------+
| 33 | 33 | DST13 | DST14 | DST15 | DST16 |
+-------+-------+-------+-------+-------+-------+
Crawford Standards Track [Page 5]
RFC 2019 Transmission of IPv6 Packets Over FDDI October 1996
Security
Security considerations are not addressed in this memo
Erik Nordmark contributed to the method for interaction with bridges
[AARCH] Hinden, and S. Deering, "IP Version 6
Architecture", RFC 1884, December 1995.
[BRIDGE]ISO/IEC 10038 : 1993 [ANSI/IEEE Std 802.1D] Media
control (MAC) bridges
[CONF] Thomson, S., and T. Narten, "IPv6 Stateless
Autoconfiguration", RFC 1971, August 1996.
[DISC] Narten, T., Nordmark, E., and W. Simpson, "Neighbor
for IP Version 6 (IPv6), RFC 1970, August 1996.
[IPV6] Deering, S., and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 1883, August 1996.
[PMTU] Mogul, J., and S. Deering, "Path MTU Discovery", RFC 1191,
November 1990.
Author's
Matt
Fermilab MS 368
PO Box 500
Batavia, IL 60510
Phone: +1 708 840-3461
EMail: crawdad@fnal.
Crawford Standards Track [Page 6]
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just be content we did not write this in Java, which would have made this "bigger and better" HAHAHHA.
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