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Interface to 802.3 MAC: Followup Jeff Mandin PMC-Sierra Maintenance Adhoc – August 2008.

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Presentation on theme: "Interface to 802.3 MAC: Followup Jeff Mandin PMC-Sierra Maintenance Adhoc – August 2008."— Presentation transcript:

1 Interface to MAC: Followup Jeff Mandin PMC-Sierra Maintenance Adhoc – August 2008

2 Aug Maintenance Adhoc2 Discussions since the first telecon Many perspectives on how to understand the interaction between the MAC client and the MAC via MA_DATA.Request(): a)There is implicit interaction between the MAC and the MA_DATA.Request primitive, so that the packet is not presented to the MAC until the MAC is ready for it -In one understanding this results in implicit queueing of the packet and increased latency -In another understanding, MA_DATA.Request might block in some cases b)Client is responsible for ensuring that it doesnt have multiple MA_DATA.Request() outstanding, but client state diagrams do not include this explicitly c)MAC interface should be modified d)Also some variations on the above

3 Aug Maintenance Adhoc3 On what issues is there some consensus? a)Each of the descriptions of the Client/MAC interaction on the previous slide has issues - none is wholly satisfactory b)To make a conclusive statement and to avoid future problems, there should be some discussions with experts in c)The MAC only processes one transmit request at a time -To the eyes of many readers, the current MAC Control diagrams (ie. PAUSE and MPCP) appear to flout this and transmit multiple requests

4 Aug Maintenance Adhoc4 Clarifying the MAC Control Diagrams Approaches: a)Add exit condition to the transmission states, so that the control flow does not advance until the MAC is ready -ie. make the magic step explicit -Does it lead to missed requests in the state diagram? Is it consistent with other MAC Clients? b)Add text to indicate that the state diagram describes transmission logic for a packet, and that the client is responsible for ensuring that it does not invoke MA_DATA.Request when the MAC is not ready - Work out the precise text after the discussion

5 Aug Maintenance Adhoc5 PAUSE State Diagram + exit condition

6 Aug Maintenance Adhoc6 MPCP Control Multiplexer


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