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RE: [LI] two ques
- To: "linux-india@xxxxxxxxxxxxxxxxxxxxx" <linux-india@xxxxxxxxxxxxxxxxxxxxx> (Non Receipt Notification Requested) (IPM Return Requested), Sharad Joshi <sharadj@xxxxxxxxxxxxxxxx> (Non Receipt Notification Requested) (IPM Return Requested)
- Subject: RE: [LI] two ques
- From: LENGARD Pascal OCISI <pascal.lengard@xxxxxxxxxxxxxxxx>
- Date: Thu, 4 Nov 1999 10:04:51 +0100
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>
> Hio,
>
> I posed these ques in different forums, but did not get any
> satisfactory
> reply. I know this is not the best stage to raise these ques, but i am
> sure any serious network software developer would be
> interested in these
> at some point of time... Now the ques.
>
> 0. *WHY* the *minimum* ethernet frame size is 64 bytes. Any rational
> behind this? This means that *at-least* 46 bytes of data *must* be
> present in the ethernet frame. (Even if there is not much
> data, that
> *must* be appended with zeros to make it 46 bytes).
The minimum length is fixed by physical problems like transmit
time of a paquet and collision detection on the wire by the ethernet
adapters.
(at least i believe this until someone tells me something else
acceptable).
ie: if you send a too small paquet that comes into collision with
another,
you take the risk that other adapters won't see the collision. This
depends on
three things: the length of your paquet, the speed of data in the wire,
the distance between the adapters on the wire. The speed is known, the
RFC
gives a limit in both minimum length and maximum distance between the
adapters
so that if you respect these limits you know that your network will work.
>
> 1. *WHY* is a pseudo header used for calculating checksum in TCP/UDP
> headers. Is this not a overhead. Any specific reasons for
> this? RFCs
> are silent on this.
don't know and don't have time to look...
>
> If any one could point out some links, which shed more light on these,
> that would suffice. I've already searched the net and various mailing
> list archieves for the above questions without success.
> Thanks in advance
> for any replies.
>
> Sharad.
pascal
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