Subject: RE: WPF syndrome and MONAMI6 (was: [manet] RE: draft-boot-manet-nemo-analysis-00.txt)

From: "Teco Boot" <[email-masked]>
Date: Fri, 2 Mar 2007 18:11:52 +0100

Alexandry wrote:
> Based on this comparison, do you think that WPF syndrome is related to
> the (H1, Cn) MONAMI6 Scenario?  Or to another MONAMI6 Scenario?  Or not
> at all to MONAMI6?

[Teco] 
In MIP / NEMO, the egress interface is used to reach HA/CN.

In MANET & MANEMO, there is the concept of the MANET interface. Both have
the WPF problem. Problem can occur also when multiple router interfaces are
used, but metrics on interface by interface basis can be used.

MONAMI6 could have the WPF problem, but there could also be the assumption
that there is only one wireless hop to the backbone and the backbone has
large BW related to the wireless hop. Using local L2 metrics can be
sufficient in this case.

Selecting the best neighbor / next hop by MIP / NEMO where multiple wireless
hops are used, the WPF problem can occur as I described. MANEMO tree
discovery RA-TIO mechanisms could be used for selecting the best (or worst)
neighbor by all nodes, thus including hosts. Just picking one ignoring any
metric is gambling.

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From: Alexandru Petrescu <[email-masked]>
Date: Mon, 05 Mar 2007 09:47:59 +0100

Teco Boot wrote:
> Alexandry wrote:
>> Based on this comparison, do you think that WPF syndrome is related
>> to the (H1, Cn) MONAMI6 Scenario?  Or to another MONAMI6 Scenario?
>> Or not at all to MONAMI6?
> 
> [Teco] In MIP / NEMO, the egress interface is used to reach HA/CN.
> 
> In MANET & MANEMO, there is the concept of the MANET interface. Both
> have the WPF problem.

If I understand you correctly both MIP/NEMO and MANET&MANEMO have the
WPF issue, I agree.  Could we relay the WPF problem to MONAMI6 group to
be included in the multhoming issues document?  I support that.

> Problem can occur also when multiple router interfaces are used, but
> metrics on interface by interface basis can be used.
> 
> MONAMI6 could have the WPF problem, but there could also be the
> assumption that there is only one wireless hop to the backbone and
> the backbone has large BW related to the wireless hop. Using local L2
> metrics can be sufficient in this case.
> 
> Selecting the best neighbor / next hop by MIP / NEMO where multiple
> wireless hops are used, the WPF problem can occur as I described.

I agree it can appear.

> MANEMO tree discovery RA-TIO mechanisms could be used for selecting
> the best (or worst) neighbor by all nodes, thus including hosts. Just
> picking one ignoring any metric is gambling.

Doesn't OSPF provide metrics in its LSAs (Link State Advertisements) 
that can help a router select the best metric at it sees fit?  I think 
it does.

What's the difference between MANEMO TD RA-TIO and OSPF LSAs?

I think in MANEMO we care about routers not about hosts?  This should be 
threaded separately.

Alex

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From: Alexandru Petrescu <[email-masked]>
Date: Mon, 05 Mar 2007 11:18:16 +0100

>  picking one ignoring any metric is gambling.

I think before having the luxury to choose among better next hops
we must have the modest feature to choose at least one next hop, ie
simply to route for best effort.

TD RA-TIOs (Tree Discovery Router Advertisements - Tree Information
Options) don't advertise prefixes.  So whereas RA-TIOs may prove good at
selecting among candidates in a tree they don't offer a means to simply
choose the nexthop.

Neither the NINA nor the TD drafts have prefixes in RA-TIOs.

What do you think.

Alex

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From: "Teco Boot" <[email-masked]>
Date: Mon, 5 Mar 2007 22:05:05 +0100

> that can help a router select the best metric at it sees fit?  I think

[Teco] 
OLSRv2 is still using hop count. Additions to OLSR could enhance that.

OSPF, including OSPF MANET is using cost based metric. For network types P2P
and P2MP a metric can be set for each neighbor. OSPF MANET-interface is
P2MP. Example in draft-chandra-ospf-manet-ext-04 (section 3.1.2.1  Router
LSAs) shows selective metrics, this would be a solution for WPF.
draft-ogier-manet-ospf-extension-08.txt is similar.

The question is how to update the metric dynamicly, this requires an L2 API.
Or count missed hellos / LSA retransmits etc. 

The question is adopting this mechanism by oyther MANET protocols, for
example by TD and use RA-TIO path metric instead of hop count?
And do we need rules for actual metric values set?