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Re: IPv6 MTU issues in FTTH applications

2002-02-23 06:50:02
 In your previous mail you wrote:

   I am trying to convince myself that the IEEE 802.3ah working group
   working on FTTH should not consider a proposal to increase the MTU
   size of Ethernet beyond 1500 bytes.

=> usually larger frames are better than the opposite: if IEEE 802.3ah
WG on FTTH (fiber to the home?) considers to decrease the MTU below
1500 octest then we shall be really in trouble.

   I am also listing the various approaches to transmit an FTTH IPv6
   packet (e.g. H.263 video + G.726 audio over RTP, over UDP, over IPv4
   over IPSecV6 over IPv6 with multiple source routing headers {up to 23 ipv6
   addresses} and authentication), over multiple Ethernet frames without
   using IPv6 packet fragmentation mechanisms.
   
=> fragmentation is the enemy... But as 99.9...% Internet has a MTU
of 1500 octets the worst thing that could happen is the bigger MTU
remains mostly unused (as 9K frames in GigaEthernet).

   Would it be possible for example to develop a new protocol number at the
   Ethernet layer which would identify that two Ethernet frames that are back
   to back, originating from the same MAC address, are to be considered glued
   together across local links, by the destination IPv6 stack?
   
=> I've seen one day someone using multi-link PPPoE (RFC 1990 & 2516)
for this purpose... BTW this is not so stupid because multi-link PPP
is near the only standardized generic fragmentation/reassembly for
a link-layer, and it is already available nearly everywhere.

Regards

Francis(_dot_)Dupont(_at_)enst-bretagne(_dot_)fr