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Hi Shahram, Clearly then we can't use the exact semantics that I suggested due to this restriction. However, this statement allows an implied poll sequence which the systems "MAY" implement. One example is, if a remote endpoint starts a poll sequence and sends out poll packets P1, P2, P3 ... at the same time the parameters change at the local endpoint and it sends out new parameters in F1 (Final packet responding to P1), F2 for P2 and so on. In such a case, ending of the poll sequence (by receiving the first packet with P=0) is indication that the parameters were accepted as the remote end as it must have received atleast one of these final packets. However, the same cannot be claimed if you start this process on F2 as the same cannot be claimed about the other end accepting these parameters as the reset of poll bit could be due to the remote end receiving F1 packet. Implementations can choose to do this and regardless of the remote end implementation this works fine. However, this is not mandatory. Do you know of any case which may not work if someone implemented this "MAY" ? Regards, Satyam From: davari at broadcom.com To: satyamsinha at live.com; rtg-bfd at ietf.org Date: Fri, 14 Aug 2009 14:14:28 -0700 Subject: RE: Timer Manipulation Hi
Satyam,
But
section 6.5 says " A BFD Control packet MUST NOT have
both the Poll (P) and Final (F) bits set.".
Regards,
Shahram From: Satyam Sinha [mailto:satyamsinha at live.com] Sent: Friday, August 14, 2009 1:57 PM To: Shahram Davari; rtg-bfd at ietf.org Subject: RE: Timer Manipulation The MAY here means that BFD allows an endpoint to set both (P) and (F) bits together in the same packet. The endpoint "MAY" initiate the poll sequence even while it is responding to a poll sequence. It is not mandatory for it to wait for the poll sequence to complete before initiating it's own poll sequence. In case of change in local parameters while the endpoint is receiving a poll sequence, the endpoint could either use new parameters and set both (P) & (F) bits or use old parameters with only the (F) bit set and then start a poll sequence following the final transmissions. In both cases the endpoint has to wait for a Final packet from the other end. Regards, Satyam From: davari at broadcom.com To: rtg-bfd at ietf.org Date: Fri, 14 Aug 2009 12:44:24 -0700 Subject: Timer Manipulation Hi,
Section 6.8.3 of base
draft says :
"If either
bfd.DesiredMinTxInterval is changed or bfd.RequiredMinRxInterval is changed, a
Poll Sequence MUST be initiated (see section 6.5). If the timing is such that a
system receiving a Poll Sequence wishes to change the parameters described in
this paragraph, the new parameter values MAY be carried in packets with the
Final (F) bit set, even if the Poll Sequence has not yet been
sent."
It seems
that the above mentioned MAY requirement is not a good idea, because if a
Poll receiver updates any parameter in the Final packet, then how can the Poll
receiver verify that those Parameters are Received by the Poll sender?
Regards,
Shahram
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