[3461] in linux-net channel archive
Re: Speaking of MTU problems
daemon@ATHENA.MIT.EDU (really kuznet@ms2.inr.ac.ru)
Mon Jun 24 15:45:11 1996
From: inr-linux-net@ms2.inr.ac.ru (really kuznet@ms2.inr.ac.ru)
To: linux-net@vger.rutgers.edu
Date: 24 Jun 1996 22:31:39 +0400
Dennis (dennis@etinc.COM) wrote:
: Shouldn't the (physical) mtu of a device take into account to header
: length?
:.....
: There are those that will argue that the MTU is the data size, but it is
: difficult
: to coordinate with directly connected devices when they have different
: definitions
: of the terms. (Ciscos have 2 mtus...phyisical and data). Perhaps its semantics,
: but it shouldnt work differently in different scenarios.
RFC 1122
MTU
The maximum transmission unit, i.e., the size of the
largest packet that can be transmitted.
------
The terms frame, packet, datagram, message, and segment are
illustrated by the following schematic diagrams:
A. Transmission on connected network:
_______________________________________________
| LL hdr | IP hdr | (data) |
|________|________|_____________________________|
<---------- Frame ----------------------------->
<----------Packet -------------------->
Internet has strict definition of MTU used in all Internet docs,
if you change it, we will have to translate all RFCs to your language.
Yes, max frame length is more natural for device driver writers,
but you still can define a field in private device data
dev->my_priv_data->truly_et_mtu or define THE_ONLY_TRUE_MTU(dev)
as dev->mtu+dev->hard_header_len.
Alexey Kuznetsov.
