Hi IPv6 hackers, Recent GbE NICs or GbE switches support Jumbo Frames, but RFC2464 provides that the maximum MTU of an Ethernet is 1500. So we cannot use the Jumbo Frames for IPv6.
2. Maximum Transmission Unit The default MTU size for IPv6 [IPV6] packets on an Ethernet is 1500 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 each node. If a Router Advertisement received on an Ethernet interface has an MTU option specifying an MTU larger than 1500, or larger than a manually configured value, that MTU option may be logged to system management but must be otherwise ignored. For example, on FreeBSD 5.4R, to send a Jumbo Frames of IPv4, I just only set the link MTU with ifconfig command. To send a Jumbo Frames of IPv6, I had to hack a kernel code to not compare link MTU with ETHERMTU(1500). BTW, Jinmei san suggested that KAME, NetBSD and OpenBSD are already hacked as above and this behavior may be only FreeBSD problem. But, according to RFC2464, FreeBSD behavior is right, and other BSDs is wrong. I know that this Jumbo Frames of GbE violates a specification of IEEE 802.3. But it is deploied already, and is used for a high performance application like the file servers. Does anyone have a plan to change the rule of RFC2464? Ryota Hirose Yamaha Corporation -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www1.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
