Subject: Query Regarding BFD Echo Mode

From: GAURAV HALWASIA <[email-masked]>
Date: Thu, 26 Nov 2009 09:27:17 +0530 (IST)

Hi,
I have few doubts regarding the BFD Echo mode.
In case we have established BFD session in between A & B (A--------B) and have enabled Echo mode on A. System B must have indicated to A that it can loop back the echo packets through the use of some non zero Echo Rx intervel (X milli seconds) in any control packets towards System A. 
A. Now will A send some "Stream of BFD Echo packets" per X milli seconds towards B or will A send only "single BFD Echo packet" per X milli seconds. Further, In any case, what the detection time will be in case of detecting failure through Echo Mode. I understand that braft says clearly that it's outside it's scope but still any pointer and sugession regarding the possible approach  will be helpful.
B. Further, till when these BFD Echo packets will be transmitted.?
C. Base draft says that a seperate UDP port will be used for Echo mode. i.e 3785. I assume that this UDP port will be opened on the system where the Echo packets has to be received back after getting loopbacked from the remote end (i.e on the system where the echo mode is getting used for detectinf failure). Is my understanding correct..?

As always, any help will be highly appreciated.
 
Thanks & Regards,
Gaurav

      The INTERNET now has a personality. YOURS! See your Yahoo! Homepage. http://in.yahoo.com/

---

From: Dave Katz <[email-masked]>
Date: Thu, 26 Nov 2009 10:30:20 -0800

On Nov 25, 2009, at 7:57 PM, GAURAV HALWASIA wrote:

> In case we have established BFD session in between A & B (A-------- 
> B) and have enabled Echo mode on A. System B must have indicated to  
> A that it can loop back the echo packets through the use of some non  
> zero Echo Rx intervel (X milli seconds) in any control packets  
> towards System A.
> A. Now will A send some "Stream of BFD Echo packets" per X milli  
> seconds towards B or will A send only "single BFD Echo packet" per X  
> milli seconds. Further, In any case, what the detection time will be  
> in case of detecting failure through Echo Mode. I understand that  
> braft says clearly that it's outside it's scope but still any  
> pointer and sugession regarding the possible approach  will be  
> helpful.

It's whatever you want to do.  The echo protocol is completely  
proprietary.  If you're not sure what you want to do with it, you  
probably don't want to use it.

> B. Further, till when these BFD Echo packets will be transmitted.?

Until the session fails, or you decide not to.  Some aspects of this  
are in scope (and in the spec.)

> C. Base draft says that a seperate UDP port will be used for Echo  
> mode. i.e 3785. I assume that this UDP port will be opened on the  
> system where the Echo packets has to be received back after getting  
> loopbacked from the remote end (i.e on the system where the echo  
> mode is getting used for detectinf failure). Is my understanding  
> correct..?

Well, that's the only system that is actually looking at the packets,  
so it would make sense.

--Dave

---

From: GAURAV HALWASIA <[email-masked]>
Date: Fri, 27 Nov 2009 09:38:34 +0530 (IST)

Hi Dave,

Thanks a lot for your inputs. I have one more query.

As per the snip from the draft 

"Required Min Echo RX Interval

      This is the minimum interval, in microseconds, between received
      BFD Echo packets that this system is capable of supporting, less
      any jitter applied by the sender (see section 6.8.9).  If this
      value is zero, the transmitting system does not support the
      receipt of BFD Echo packets."

So is this interval talking about the interval inbetween the individual Echo Packets or is it the interval inbetween the stream of "Echo Packets". To me it looks like this is the interval in between the individual "Echo Packets".?
Your inputs/comments will be very useful and highly appreciated.

With Best Regards,
Gaurav

________________________________
From: Dave Katz <[email-masked]>
To: GAURAV HALWASIA <[email-masked]>
Cc: BFD <[email-masked]>; Amitesh Shukla <[email-masked]>
Sent: Fri, 27 November, 2009 12:00:20 AM
Subject: Re: Query Regarding BFD Echo Mode

Hi,
>A. Now will A send some "Stream of BFD Echo packets" per X milli seconds towards B or will A send only "single BFD Echo packet" per X milli seconds. Further, In any case, what the detection time wil…
It's whatever you want to do.  The echo protocol is completely proprietary.  If you're not sure what you want to do with it, you probably don't want to use it.

B. Further, till when these BFD Echo packets will be transmitted.?
Until the session fails, or you decide not to.  Some aspects of this are in scope (and in the spec.)

C. Base draft says that a seperate UDP port will be used for Echo mode. i.e 3785. I assume that this UDP port will be opened on the system where the Echo packets has to be received back after getting loopbacked from the remote end (i.e on the system where the echo mode is getting used for detectinf failure). Is my understanding correct..?
Well, that's the only system that is actually looking at the packets, so it would make sense.

--Dave

---

From: "Reshad Rahman (rrahman)" <[email-masked]>
Date: Fri, 27 Nov 2009 07:14:09 -0500

This is the interval between individual packets for that particular BFD
session.

Regards,

Reshad.

From: [email-masked] [mailto:[email-masked]] On
Behalf Of GAURAV HALWASIA
Sent: Thursday, November 26, 2009 11:09 PM
To: Dave Katz
Cc: BFD; Amitesh Shukla
Subject: Re: Query Regarding BFD Echo Mode

Hi Dave,

So is this interval talking about the interval inbetween the individual
Echo Packets or is it the interval inbetween the stream of "Echo
Packets". To me it looks like this is the interval in between the
individual "Echo Packets".?

With Best Regards,

Gaurav

Hi,

In case we have established BFD session in between A & B (A--------B)
and have enabled Echo mode on A. System B must have indicated to A that
it can loop back the echo packets through the use of some non zero Echo
Rx intervel (X milli seconds) in any control packets towards System A. 
A. Now will A send some "Stream of BFD Echo packets" per X milli seconds
towards B or will A send only "single BFD Echo packet" per X milli
seconds. Further, In any case, what the detection time will be in case
of detecting failure through Echo Mode. I understand that braft says
clearly that it's outside it's scope but still any pointer and sugession
regarding the possible approach  will be helpful.

Until the session fails, or you decide not to.  Some aspects of this are
in scope (and in the spec.)

	C. Base draft says that a seperate UDP port will be used for
Echo mode. i.e 3785. I assume that this UDP port will be opened on the
system where the Echo packets has to be received back after getting
loopbacked from the remote end (i.e on the system where the echo mode is
getting used for detectinf failure). Is my understanding correct..?

Well, that's the only system that is actually looking at the packets, so
it would make sense.

--Dave

The INTERNET now has a personality. YOURS! See your Yahoo! Homepage
<http://in.rd.yahoo.com/tagline_yyi_1/*http:/in.yahoo.com/> .