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Re: [EFM] RE: Pause frame usage in transport networks


Based on previous messages, I understand what you are trying to do.  This 
is a problem that we dealt in writing the original Ethernet over SONET 
standard, X.86.  The other EOS standards written since X.86 have not paid 
attention to this detail.

The specific reason that X.86 was written to be a non-802.1 bridge, without 
a MAC Control layer on receive side was to allow MAC control frames to span 
the entire customer link, end to end, including the transmission facility 
portion of that link.  This allows all MAC Control frames, including 
"Pause" as well as the 802.3ah OAM frames to function end to end over the 

When implementing a service using systems based on transmission service 
technology standard that does not specifically protect the integrity of the 
MAC Control frames as well as the MAC frames then you can not count on them 
functioning beyond the first link.  In fact, you should take it for granted 
that the "Pause" frames as well as the OAM frame will be dropped at the 
first interface on the service provider network that the customer 
establishes a link to.  There is no alternative to this other than using 
the correct transmission technology that does specifically provide for the 
integrity of all frames.

Thank you,
Roy Bynum

At 11:52 AM 3/3/2003 -0800, Shahram Davari wrote:

>Hi all,
>Based on 802.3 standard, the PAUSE frames may have an individual or 
>multicast MAC address (including broadcast).
>It seems to me if the ONU1 sends PAUSE frames with Dest MAC address of 
>ONU2, then the OLT1 would
>relay that to ONU2 (no matter if OLT1 behaves as a transparent box or as a 
>bridge), while if the ONU1
>sends a PAUSE frame with Dest MAC address of OLT1 or a multicast MAC 
>address then the PAUSE frames
>would be terminated at OLT1 if OLT1 behaves like a bridge.
>       Eth              EOS            Eth
>In other words for end-to-end OAM, if we know that OLT1 does not terminate 
>any OAM frames, then ONU1 may use either
>Dest MAC address of ONU2 or a multicast address, but if we know that OLT1 
>terminates MAC, then ONU1 should use Dest MAC address of ONU2. To be is 
>safe side it seems that for end-to-end OAM, it is best if ONU1 always sets 
>the Dest MAC address to that of ONU2.