Thread Links Date Links
Thread Prev Thread Next Thread Index Date Prev Date Next Date Index

Re: Frame Termination


A station (RS) may terminate a packet by sending FE
(Transmit Error Propagation - from table 46-2) instead
of FD (Terminate) when the station finds that:

"it is necessary to request that the PHY deliberately
corrupt the contents of the frame in such a manner
that a receiver will detect the corruption with the
highest degree of probability" - see

However, at the end of this packet, the station's RS
should move back to transmitting IDLEs. It is possible
that due to some bug or piece of broken logic within
the station, the RS continuously sends the Transmit Error
Propagation (FE) value.

Your question about the TERMINATE state must be in
reference to Clause 48, figure 48-9, since the MAC has
no states and this is the only place I can find a state
with this name.

If a packet were to switch from receiving ||D|| to
||E||, this state machine would move from the
DATA_MODE_START state through the AUDI(ELSE) path
to the RECEIVE state and on to the DATA_MODE_OTHER
state. It would never hit the TERMINATE state.

The receive RS only considers an end of packet to occur
if it receives a control character other than the /E/.
In a case such as you've described, the /E/ characters would
be continuously received so the packet would be ongoing.
If and when it ever ends, it would need to be marked with
a CRC error (if it wasn't already marked bad due to exceeding
the 1518 byte limit set by the MAC).

I hope this helps.


satya wrote:
> hi,
> I have just started studying 10 Gig protocol.
> I have doubt on frame end logic in the 10 Gig Ethernet frame format.
> At frame end if in place of FD we send
> FE ( or any other word except IDLE word) continuously.
> how can we detect the end of frame.
> When should MAC should come out of TERMINATE State machine.
> Bottom line
> Under what all conditions should mac come out of TERMINATE state machine apart
> from normal sequence.
> Thank you
> satya

Benjamin Brown
2 Commerce Park West
Suite 104 
Bedford NH 03110
603-641-9837 - Work
603-491-0296 - Cell
603-626-7455 - Fax
603-798-4115 - Home Office