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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