Re: [DNA] Comments on DNAv6 (draft-dnadt-dna-protocol-00.txt)

[Greg Daley <greg.daley@eng.monash.edu.au>]

Hi Erik,

I think we should fall back to RFC2461 ND behaviour in the bootstrap and
responding router load cases.

Please see below for my reasoning.

Erik Nordmark wrote:
> Subba Reddy wrote:
[cut]
> 
>> 2. While bootstrapping DNA data structures(section 5.1.3), a) will
>> the router reply for RSs without landmark option (may be sent by
>> other routers) b) will the router reply for RSs that contains
>> landmark option (may be sent by DNA host)
> 
> 
> I think the current text says that it will not respond at all. This is a 
> bit suboptimal when multiple routers boot at the same time.
> I suspect we need to figure out how to tweak this.
> Suggestions?

If we respond as if we have an RFC2461 host, then any problems
experienced will be the same as if a host has transitioned to
a network not supporting DNA (except that it will have a
link-layer hint to distinguish).

It's a short0lived transient situation though.

The additional trouble of blocking out responses can hamper
initialization after failures.  This is already well covered
for fixed hosts within 2461 and should be taken advantage of.

[cut]
> 
>> 5. To deal with amplification effect, what about having a threshold
>> on number of routers sending fast RA? For example, only first 5
>> routers (as per the fast RA rankings) only will reply for RSs (in
>> addition to the method specified in the draft)
> 
> 
> That might make sense.
> 
> I assume the 6+ ranked routers would not be completely quiet, but 
> instead schedule a 3 second multicast RA. This is needed in the case 
> that the routers annouce different prefixes, and also to make the host 
> discover that it has >5 default routers.

I think that we want to not make the system worse
in the face of bogus routers.

The existing RFC2461 behaviour is to perform random delay (0-500ms),
multicast, and induce additional delay if the minimum multicast
advertisement interval has not passed.

I guess that's actually as effective as the Nth router 3 second delay,
and is robust to fake routers.

Greg