Re: [Ospf-wireless-design] OSPF Flooding and Higher Mobility

Acee Lindem <acee@cisco.com> Fri, 04 November 2005 22:08 UTC

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Date: Fri, 04 Nov 2005 17:08:05 -0500
From: Acee Lindem <acee@cisco.com>
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To: Richard Ogier <rich.ogier@earthlink.net>
Subject: Re: [Ospf-wireless-design] OSPF Flooding and Higher Mobility
References: <436BCA18.2000102@cisco.com> <436BD6DB.5010701@earthlink.net>
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Richard Ogier wrote:

> I'm sure other people will also comment, but I have some preliminary
> comments now. When comparing the overhead between Smart Peering
> and MDRs, you need to use uniconnected MDRs for a fair comparison
> (unless you want to implement a biconnected version of Smart Peering).

Possibly - this could explain why there is a slightly better delivery ratio

>
> Also, it would be nice to compare with 100 nodes, and to compare
> other measures than overhead, such as delivery ratio, etc.
> I am eager to see such results.

I haven't personally run any simulations but I've been told that the run
time increases significantly with the number of nodes. However, more
nodes would definitely be interesting - as well as, smaller pause times and
higher velocities.

>
> Another point to consider is that OSPF-MDR is a natural
> generalization of OSPF. (MDRs generalize DRs in a natural way.)
>
> Richard
>
>
> Acee Lindem wrote:
>
>> Based on the INRIA reports and attendant E-mail threads, we (Cisco) have
>> recently gone down the path of doing some simulations with higher 
>> mobility.
>> The attached spread sheets show the results for 16 m/sec velocity and
>> varying radio range. The pause time is still 40 seconds. We found the 
>> results
>> to be more drastic with a smaller pause time but had some problems 
>> getting
>> a complete set of runs.
>>
>> MPRs have the following improvements over the base provided with GTNetS:
>>
>>     - Smart Peering is fixed to avoid instability by running a second
>>       SPF to determine if a potential peer is available via a real
>>       adjacency or unsynchronized adjacency. The adjacency is only 
>> suppressed
>>       in the case of connectivity to the SPT via real adjacencies. This
>>       is discussed in the Boeing report but wasn't implemented.
>>
>> Also, we have enabled promiscuous LSA caching enabled with the LSA
>> cache timeout extended to 100 seconds. We are attempting to get some
>> runs with this disabled as well some with a shorter pause time.
>>
>> For MDRs we used the standard bi-connected topology.
>>
>> We will provide the diffs for the code changes supporting smart peering.
>>
>> We have also been investigating using the MDR strategy of reducing 
>> adjacencies
>> by taking advantage of the flooding topology. However, doing this 
>> effectively
>> is more complex than it first seemed.
>>
>> Stan Ratliff, a Cisco Software Engineer, will be presenting these 
>> results.
>>
>> Thanks and Sorry for the Short Notice,
>> Acee
>>
>>
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