Re: MTU and 2.4.x kernel

From: Jordan Mendelson (jordy@napster.com)
Date: Thu Feb 15 2001 - 15:54:26 EST


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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