Re: [ethmac] =?gb2312?B?aGVscA==?=

[aramisp@yahoo.com]

Why is the max size of a frame 1500 bytes.  Where is this number 
determined from. ???????
(or aprox. 1500 bytes)

----- Original Message ----- 
From: Javier_castillo_villar@y...  
To: ethmac@o...  
Date: Tue, 23 Apr 2002 11:17:52 +0200 
Subject: Re: [ethmac] =?gb2312?B?aGVscA==?= 

> 
> 
>  You can have various cases. If you are using DIX ethernet standard 
> (the windows standard) your length field are not the length of the 
> frame, it磗 the type of the frame, if you are using IP over 
> ethernet this 
> field is 0x800 if you are using ARP is 0x806. If you are using 
> 802.3 the 
> length type can be lower than the total length of the frame. This 
> is 
> because the frame are very short and the tx make padding that is 
> they 
> put character 0x20 to make the frame at least 64 bytes long. 
>  If in your trasmitter the frame it磗 longer than 1500 bytes it磗 
> an error 
> because the IP must know the MTU(maximun transfer unit) of the phy 
> layer and he must send only the number of bytes that the phy layer 
> can 
> send. 
> 
> 
> 
> 
> 
> ----- Original Message ----- 
> From: "lxn" <panic@1... > 
> To: ethmac@o... 
> Date: Thu, 18 Apr 2002 20:31:05 +0800 (CST) 
> Subject: [ethmac] =?gb2312?B?aGVscA==?= 
> 
> > Hi, 
> > when the tx module sending out frames, if the number of length 
> > field is smaller than the real frame size, what shall i do? 
> Cut the 
> > frame to meet the length field or transmit the whole frame? 
> And is 
> > this considered a error? 
> > 
> > 
> 
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