In fact SD stands for start of frame delimiter. It is an essential component
of the synchronization process alongwith the preamble.
Regards
Atif
To: Stephen Ede <[EMAIL PROTECTED]>; [EMAIL PROTECTED]
<[EMAIL PROTECTED]>
Date: Sunday, July 30, 2000 9:30 AM
Subject: Re: 802.3 frame and full-duplex
>Stephen,
>
>First, SD is the last octet of the preamble. You get 7 octets of 0x55 and
>the final octet is 0xD5 which is signaling the start of the Data Link
frame,
>hence SD.
>
>On the switch question, if port A,B, and C are sending packets to port D I
>think that the output queue on D would accumulate the packets if the
offered
>load is greater than the link's capacity. However, the queue is not
>infinite and eventually you will have to start dropping packets.
>
>Jeff Humphreys
>
>
>----- Original Message -----
>From: Stephen Ede <[EMAIL PROTECTED]>
>To: <[EMAIL PROTECTED]>
>Sent: Saturday, July 29, 2000 7:28 PM
>Subject: 802.3 frame and full-duplex
>
>
>> I have 2 questions to submit here...
>>
>> 1) If there are several nodes attached to a 10/100 switch, and all NICs
>are
>> in full duplex mode, this means that CSMA/CD is not in effect, loopback
is
>> turned off, and any station can transmit and receive concurrently. But
>what
>> happens when 2 or 3 of these stations want to transmit to one particular
>> station concurrently? Is the traffic buffered in the switch? Or is
>CSMA/CD
>> still in effect, even in full duplex mode, where they will sense the wire
>> and wait if busy?
>>
>> 2) In the diagram below of an 802.3 frame, what does the "SD" potion
>> signify?
>>
>> | Preamble | SD | Dest. Add. | Source Add. | Length | DSAP | SSAP |
>Control
>> | Data | FCS |
>>
>> Thank you in advance.
>>
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