Re: [DNA] [Issue X] LinkID v.s. Landmark Prefix

[Erik Nordmark <erik.nordmark@sun.com>]

JinHyeock Choi wrote:

> In linkid scheme, a prefix addition or deletion would not 
> cause an incorrect decision, whereas there is such a 
> possibility for Landmark/ CompleteRA. 
> 
> Allow me an example. 
> 
> Assume a link with a router R and host H. 
> R advertises Prefix1. 
> 
> R1 happens to stop advertising Prefix1 and 
> start advertising a new prefix Prefix2. 

But in this case, when all the prefixes are being removed and replaced 
with a completely new set of prefixes, there is little if no harm to 
incorrectly assume a link change (after all, all the addresses need to 
be reconfigured, etc).

A more realistic example is the one I included in my more recent email 
today.

> R announces it by sending an RA but H 
> doesn't receive it. 
> 
> Then next time H receives CompleteRA with
> Prefix2, it will falsely assume a link change.   

Actually not; if will only assume a link change if it receives a link up 
event notification between the last time it heard a RA with Prefix1 and 
the first time it heard an RA with Prefix2.

    Erik

> Linkid scheme deal with such a temporary flapping by adopting 
> extra techniques such as "Linkid Prefix List" or "LEAST_VALID_LIFETIME". 
> 
> I don't know how Landmark/ CompleteRA can make a correct decision
> under flapping without such an extra techniques. 
> 
> Thanks in advance for your kind consideration. 
> 
> Best Regards
> 
> JinHyeock
>