RE: Intra-area Crankback

["Ash, Gerald R (Jerry), ALCTA" <gash@att.com>]

Don,

>The issue is that if people implement crank back only they don't 
>get the benefit of feedback and therefore have only solved part 
>of the problem. I agree that they can be independent. I think there 
>is benefit to linking them. 

Agreed that there is benefit in having both crankback and feedback in play.

>Also note that feedback does not alone imply that rerouting 
>can be performed. A proper notify or failure reason must also 
>be taken into account. 

Agreed, this is what we were trying to point out in distinguishing crankback and feedback. 

>From draft-iwata-mpls-crankback-02.txt 
>  "In the feedback case [ASHW], 
>   or in the current error sub-codes of the Notification message [CR- 
>   LDP], one can infer a situation where rerouting can be done, but it 
>   also can lead to other problems, which have been experienced in 
>   practice, as illustrated below." 
>This implies to me that the authors feel that feedback is somehow 
>inferior to crankback.

Not at all.  We were trying to point out that crankback is a reroute-notify mechanism and if one emulates a 'crankback' (e.g., with a failure-notify), it is not a replacement for it.  We were not saying either feedback or crankback is superior or inferior, they do different things and both can provide needed functionality.  We have in fact pointed out the benefit of feedback in other drafts, e.g. http://www.ietf.org/internet-drafts/draft-ash-multi-area-te-reqmts-01.txt.  We'll revise the text in the next rev to remove any implied criticism, which was not intended. 

Regards,
Jerry