Subject: Re: State machine diagram & alarm generation

From: Bob Albrightson <[email-masked]>
Date: Wed, 16 Feb 2005 4:34:15 PST

> 
> On Feb 14, 2005, at 9:20 AM, Jeffrey Haas wrote:
> 
> > Richard,
> >
> > On Sat, Feb 12, 2005 at 08:38:37AM -0000, [email-masked] wrote:
> >> First of all, thank you for taking the time to clarify the state
> >> machine. Do you think it would be worthwhile adding a state machine
> >> diagram to the base document to provide clarification?
> >
> > I'll let the authors answer, but it sounds useful to me. :-)
> 
> I can try to add some ASCII art, but it would probably be more 
> straightforward to just add a brief paragraph describing the state 
> machine, which is really quite simple.  I'll give that a shot first.  
> (Working on the next rev...)
> 
> --Dave
> 

This is something I cooked up a while ago.  Let me know if there are
any issues with it.

 -bob

                          BFD state diagram

                                                     +------------+
                    Rx_IHY = 1                       |            |
      +--------------------------------------------->|     UP     |
      |                                              |            |
      |                                              +------------+
      |                                               |    ^
      |                                               |    |
+------------+ Detection +------------+   Rx_IHY=0   /     |
|            |  Expired  |            |<------------+      |
|    INIT    |---------->|   FAILING  |                    | Rx_IHY = 1
|            |           |            |-------------+      |
+------------+           +------------+   Rx_IHY=0   \     |
      |                     ^      |                  |    |
      |                     +------+                  v    |
      |                     Rx_IHY=1                 +------------+
      |                                              |            |
      +--------------------------------------------->|    DOWN    |
                    Rx_IHY = 0                       |            |
                                                     +------------+

---

From: [email-masked]
Date: Thu, 17 Feb 2005 07:31:02 -0000

Bob,

Thanks, I think it would be useful to add this diagram to the draft. One minor point is that the arrow between Down and Init is pointing towards Down, this should be reversed to describe the state change from Down to Init on receipt of a packet with IHY = 0 rather than the other way round. Also:

1. I think it would be worth adding the text "Or Detection Expired" where it says "Rx_IHY = 0" above the arrow pointing from Up to Failing (to describe the state change to Failing from Up on Detection Time expiration).

2. It would be good to have a loop back arrow to/from the Init state on receipt of BFD packets with IHY = 0 (similar to the loop on the failing state for IHY = 1).

Regards,

Richard

	-----Original Message----- 
	From: [email-masked] on behalf of Bob Albrightson 
	Sent: Wed 16/02/2005 07:34 
	To: Dave Katz 
	Cc: [email-masked]; Jeffrey Haas; [email-masked] 
	Subject: Re: State machine diagram & alarm generation

	
	 -bob

	                          BFD state diagram

	                                                     +------------+
	                    Rx_IHY = 1                       |            |

---

From: Bob Albrightson <[email-masked]>
Date: Thu, 17 Feb 2005 3:06:34 PST

> Bob,
> 
>  
> 
> Thanks, I think it would be useful to add this diagram to the
> draft. One minor point is that the arrow between Down and Init is
> pointing towards Down, this should be reversed to describe the state
> change from Down to Init on receipt of a packet with IHY = 0 rather
> than the other way round. Also:
> 
>  
> 
> 1. I think it would be worth adding the text "Or Detection Expired"
> where it says "Rx_IHY = 0" above the arrow pointing from Up to
> Failing (to describe the state change to Failing from Up on
> Detection Time expiration).
> 
>  
> 
> 2. It would be good to have a loop back arrow to/from the Init state
> on receipt of BFD packets with IHY = 0 (similar to the loop on the
> failing state for IHY = 1).

Thanks for the comments.  Here is the new ascii art.

 -bob

                          BFD state diagram

                                                        Rx_IHY=1
                                                        +------+
                                                        |      v
                                                     +------------+
                    Rx_IHY = 1                       |            |
      +--------------------------------------------->|     UP     |
      |                                              |            |
      |                                   Detection  +------------+
      |                                    Expired    |    ^
      |                                      or       |    |
+------------+ Detection +------------+   Rx_IHY=0   /     |
|            |  Expired  |            |<------------+      |
|    INIT    |---------->|   FAILING  |                    | Rx_IHY = 1
|            |--+        |            |-------------+      |
+------------+  |        +------------+   Rx_IHY=0   \     |
      ^  ^      |           ^      |                  |    |
      |  +------+           +------+                  v    |
      |  Rx_IHY=0           Rx_IHY=1                 +------------+
      |                                              |            |
      +----------------------------------------------|    DOWN    |
                    Rx_IHY = 0                       |            |
                                                     +------------+

---

From: [email-masked]
Date: Thu, 17 Feb 2005 12:18:54 -0000

Thanks Bob. 
It looks good to me.
 
Richard

	-----Original Message----- 
	From: Bob Albrightson [mailto:[email-masked]] 
	Sent: Thu 17/02/2005 06:06 
	To: Spencer,R,Richard,XDE7 R 
	Cc: [email-masked]; [email-masked]; [email-masked]; [email-masked] 
	Subject: RE: State machine diagram & alarm generation

	
	 -bob
	
	                          BFD state diagram

	                                                        Rx_IHY=1
	                                                        +------+
	                                                        |      v
	                                                     +------------+
	                    Rx_IHY = 1                       |            |