RE: BFD stability follow-up from IETF-91

[Santosh P K <[e-mail]>]

Hi Manav,
      Thanks. Please see inline. 

> >> the seq numbers at the *end* of the BFD packet. This would not be
> >> covered in the Length field carried in the BFD header but would be
> >> accounted for in the length carried in the IP header. The concept of
> >> attaching a trailer is documented well and is used in the IGPs. RFC
> >> 6506 describes one such trailer
> >
> > You are suggesting to add the debug trailer with or without authentication
> right?
> 
> without.

If we can go with trailer method then it can be applicable to both with and without Auth right? I was thinking having two solution might complicate things :)? 


Thanks
Santosh P K 

> >
> >> On Thu, Nov 27, 2014 at 8:32 PM, Santosh P K <[e-mail]>
> >> wrote:
> >> > Manav,
> >> >     This is good question.
> >> >
> >> >> Can the authors add some text on how this debugging mechanism
> >> >> would work if somebody employs BFD authentication?
> >> >
> >> > Right now we have considered without authentication (we are setting
> >> > A
> >> bit). We should add some text on how we can use both Auth and de bug
> TLV.
> >> Is there any suggestion you have? I will get back to you on this.
> >> >
> >> >
> >> > Thanks
> >> > Santosh P K
> >> >
> >> >> > -----Original Message-----
> >> >> > From: Rtg-bfd [mailto:[e-mail]] On Behalf Of
> >> >> > Mach Chen
> >> >> > Sent: Thursday, November 27, 2014 2:13 PM
> >> >> > To: Marc Binderberger
> >> >> > Cc: [e-mail]
> >> >> > Subject: RE: BFD stability follow-up from IETF-91
> >> >> >
> >> >> > Hi Marc,
> >> >> >
> >> >> >> -----Original Message-----
> >> >> >> From: Marc Binderberger [mailto:[e-mail]]
> >> >> >> Sent: Thursday, November 27, 2014 1:43 AM
> >> >> >> To: Mach Chen
> >> >> >> Cc: Manav Bhatia; [e-mail]
> >> >> >> Subject: RE: BFD stability follow-up from IETF-91
> >> >> >>
> >> >> >> Hello Mach,
> >> >> >>
> >> >> >> > This triggers me think out there should be another solution
> >> >> >> > for getting the Tx and Rx timestamps without encoding the
> >> >> >> > timestamps in the BFD
> >> >> >> packets.
> >> >> >> > For example, the Tx and Rx systems could just save timestamps
> >> >> >> > locally or send them to a centralized entity and then use the
> >> >> >> > sequence numbers to correlate them for further analyzing.
> >> >> >>
> >> >> >> I remember some discussion on NVO3 about how many bits it takes
> >> >> >> ;-) - could you send the links/draft names you are working on
> >> >> >> to this
> >> list?
> >> >> >> May be useful for further discussions.
> >> >> >
> >> >> > Sure, here is the
> >> >> > link(http://tools.ietf.org/html/draft-chen-ippm-coloring-
> >> >> based-ipfpm-framework-02) for the reference.
> >> >> >
> >> >> > But here I want to say is that since we have sequence number, we
> >> >> > may not
> >> >> need the marking based solution. Suppose that someone want to
> >> >> monitor the delay of a BFD packet , just record and save the
> >> >> timestamp at the Tx side, which indexed by the sequence number.
> >> >> Similarly, do the same at the Rx side. Then based on the
> >> >> timestamps from both Tx and Rx, and using the sequence number to
> >> >> correlate the timestamps, it can also provide a way to monitor the
> delay of the BFD packet.
> >> >> >
> >> >> > That means, only if there is sequence number, even if without
> >> >> > carrying the
> >> >> timestamp in the BFD packet, BFD packet delay can be measured.
> >> >> >
> >> >> > Best regards,
> >> >> > Mach
> >> >> >
> >> >> >>
> >> >> >>
> >> >> >> Thanks & Regards,
> >> >> >> Marc
> >> >> >>
> >> >> >>
> >> >> >>
> >> >> >> On Wed, 26 Nov 2014 09:17:32 +0000, Mach Chen wrote:
> >> >> >> > Hi Marc and Manav,
> >> >> >> >
> >> >> >> >> -----Original Message-----
> >> >> >> >> From: Rtg-bfd [mailto:[e-mail]] On Behalf Of
> >> >> >> >> Marc Binderberger
> >> >> >> >> Sent: Wednesday, November 26, 2014 4:50 PM
> >> >> >> >> To: Manav Bhatia
> >> >> >> >> Cc: [e-mail]
> >> >> >> >> Subject: Re: BFD stability follow-up from IETF-91
> >> >> >> >>
> >> >> >> >> Hello Manav,
> >> >> >> >>
> >> >> >> >>> I believe the work is important and addresses something
> >> >> >> >>> thats really required (spent too much time debugging why
> >> >> >> >>> BFD
> >> flapped!).
> >> >> >> >>
> >> >> >> >> agree :-) we should keep the discussion alive.
> >> >> >> >>
> >> >> >> >>
> >> >> >> >>> side Time stamping would have helped in debugging whether
> >> >> >> >>> the
> >> >> BFD
> >> >> >> >>> packet was sent late, or whether the packet was sent on
> >> >> >> >>> time and also arrived on time but was delayed when passing
> >> >> >> >>> it up the BFD stack/processor (lay in the RX buffer for tad
> >> >> >> >>> too
> >> >> >> >>> long)
> >> >> >> >>
> >> >> >> >> well, I can see a point in having the Tx timestamps in the
> >> >> >> >> packet mainly for the purpose of knowing "this" packet was
> >> >> >> >> okay/not okay on the Tx side and to correlate it with your
> >> >> >> >> local Rx
> >> measurement.
> >> >> >> >
> >> >> >> > Yes, this is one solution if people think BFD delay is needed.
> >> >> >> > If allow to have Tx timestamps to be carried in the packets,
> >> >> >> > seems it should be no problem to leave a seat for the Rx
> >> >> >> > timestamps as well :-). After all, with both Tx and Rx
> >> >> >> > timestamp, it may simplify the
> >> >> >> implementation.
> >> >> >> >
> >> >> >> >>
> >> >> >> >> And even this point is less relevant with sequence numbers
> >> >> >> >> as this number allows the identification of packets and thus
> >> >> >> >> the correlation of information from the Tx and Rx system.
> >> >> >> >
> >> >> >> > Indeed, the sequence number helps a lot for the correlation
> >> >> >> > between the Tx and Rx system.
> >> >> >> >
> >> >> >> > This triggers me think out there should be another solution
> >> >> >> > for getting the Tx and Rx timestamps without encoding the
> >> >> >> > timestamps in the BFD
> >> >> >> packets.
> >> >> >> > For example, the Tx and Rx systems could just save timestamps
> >> >> >> > locally or send them to a centralized entity and then use the
> >> >> >> > sequence numbers to correlate them for further analyzing.
> >> >> >> >
> >> >> >> > Best regards,
> >> >> >> > Mach
> >> >> >> >
> >> >> >> >>
> >> >> >> >>
> >> >> >> >> Regards, Marc
> >> >> >> >>
> >> >> >> >>
> >> >> >> >>
> >> >> >> >>
> >> >> >> >>
> >> >> >> >>
> >> >> >> >> On Wed, 26 Nov 2014 12:26:41 +0530, Manav Bhatia wrote:
> >> >> >> >>> Hi Jeff,
> >> >> >> >>>
> >> >> >> >>> I vividly remember the original intent of the stability
> >> >> >> >>> draft was to help debug BFD failures -- to isolate the
> >> >> >> >>> issue at the RX or the TX side Time stamping would have
> >> >> >> >>> helped in debugging whether the BFD packet was sent late,
> >> >> >> >>> or whether the packet was sent on time and also arrived on
> >> >> >> >>> time but was delayed when passing it up the BFD
> >> >> >> >>> stack/processor (lay in the RX buffer for tad too long),
> >> >> >> >>> etc. But then time stamping came with its own set of issues,
> and was hence dropped from the original draft.
> >> >> >> >>>
> >> >> >> >>> Can the authors send a summary on the list on why time
> >> >> >> >>> stamping was dropped so that we're all clear on that one.
> >> >> >> >>>
> >> >> >> >>> The current proposal does help but is not complete.
> >> >> >> >>>
> >> >> >> >>> Assume that the RX end loses a BFD session and learns later
> >> >> >> >>> that it did eventually receive the missing BFD packets
> >> >> >> >>> (based on the seq
> >> >> #).
> >> >> >> >>> How would it know which end was misbehaving? Was it a delay
> >> >> >> >>> at the TX side, or was it the RX that delayed passing the
> >> >> >> >>> packets to the BFD process(or). This is usually what we
> >> >> >> >>> want to debug and i want to understand how this draft with
> >> >> >> >>> sequence numbers can unequivocally tell me that.
> >> >> >> >>>
> >> >> >> >>> I believe the work is important and addresses something
> >> >> >> >>> thats really required (spent too much time debugging why
> >> >> >> >>> BFD
> >> flapped!).
> >> >> >> >>> Clearly what would help is putting a small section that
> >> >> >> >>> describes how we can use the sequence numbers to debug
> what
> >> >> >> >>> and where
> >> >> things went wrong.
> >> >> >> >>>
> >> >> >> >>> Cheers, Manav
> >> >> >> >>>
> >> >> >> >>>
> >> >> >> >>> On Wed, Nov 26, 2014 at 5:49 AM, Jeffrey Haas
> >> >> >> >>> <[e-mail]>
> >> >> wrote:
> >> >> >> >>>> draft-ashesh-bfd-stability-01 was presented again during
> >> >> >> >>>> IETF-91 in Honolulu.  The slides can be viewed here:
> >> >> >> >>>>
> >> >> >> >>>> http://www.ietf.org/proceedings/91/slides/slides-91-bfd-4.
> >> >> >> >>>> ppt
> >> >> >> >>>> x
> >> >> >> >>>>
> >> >> >> >>>> To attempt to simplify the presentation, the contentious
> >> >> >> >>>> portion of the timers were removed from the proposal,
> >> >> >> >>>> leaving only the sequence numbering for detecting loss of
> >> >> >> >>>> BFD async
> >> packets.
> >> >> >> >>>>
> >> >> >> >>>> When the room was polled to see whether the draft should
> >> >> >> >>>> be adopted as a WG item, the sense of the room was very
> quiet.
> >> >> >> >>>> As promised, this is to inquire for support for this draft
> >> >> >> >>>> on the WG mailing list to make sure the whole group has a
> voice.
> >> >> >> >>>>
> >> >> >> >>>> It should be noted that post-meeting discussion on the
> >> >> >> >>>> fate of this draft noted that BFD authentication code
> >> >> >> >>>> points are plentiful and are available with expert review.
> >> >> >> >>>> Should the draft authors wish to continue this work as
> >> >> >> >>>> Experimental, that is an
> >> >> option.
> >> >> >> >>>>
> >> >> >> >>>> -- Jeff
> >> >> >> >>>>
> >> >> >> >>>
> >> >> >> >
> >> >> >
> >> >