Re: MTU and 2.4.x kernel

Jordan Mendelson (jordy@napster.com)
Thu, 15 Feb 2001 12:54:26 -0800

Rick Jones wrote:
>
> > Default of 536 is sadistic (and apaprently will be changed eventually
> > to stop tears of poor people whose providers not only supply them
> > with bogus mtu values sort of 552 or even 296, but also jailed them
> > to some proxy or masquearding domain), but it is still right: IP
> > with mtu lower 576 is not full functional.
>
> I thought that the specs said that 576 was the "minimum maximum"
> reassemblable IP datagram size and not a minimum MTU.

RFC 1191 (Path MTU Discovery as it happens):


Plateau MTU Comments Reference
------ --- -------- ---------
65535 Official maximum MTU RFC 791
65535 Hyperchannel RFC 1044
65535
32000 Just in case
17914 16Mb IBM Token Ring ref. [6]
17914
8166 IEEE 802.4 RFC 1042
8166
4464 IEEE 802.5 (4Mb max) RFC 1042
4352 FDDI (Revised) RFC 1188
4352 (1%)
2048 Wideband Network RFC 907
2002 IEEE 802.5 (4Mb recommended) RFC 1042
2002 (2%)
1536 Exp. Ethernet Nets RFC 895
1500 Ethernet Networks RFC 894
1500 Point-to-Point (default) RFC 1134
1492 IEEE 802.3 RFC 1042
1492 (3%)
1006 SLIP RFC 1055
1006 ARPANET BBN 1822
1006
576 X.25 Networks RFC 877
544 DEC IP Portal ref. [10]
512 NETBIOS RFC 1088
508 IEEE 802/Source-Rt Bridge RFC 1042
508 ARCNET RFC 1051
508 (13%)
296 Point-to-Point (low delay) RFC 1144
296
68 Official minimum MTU RFC 791

Jordan
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