Hi Jeffrey,
please see inline:
On 7/21/14 15:24 , Jeffrey (Zhaohui) Zhang wrote:
Hi,
In today's OSPF session there were mainly two questions/comments during my
presentation:
1. Acee: more discussion on mailing list about whether this is a general
problem/solution that the WG should be taking on
2. Peter: should we use OSPFv3 Extended LSA for a cleaner encoding
my comment was not specific to OSPFv3.
I propose to use following extensions to encode metric from DR to
attached router:
1. OSPFv2: Extended Link LSA
2. OSPFv3: E-Router LSAs
I want to repeat and add some comments/answers here as a starting point for
more discussions on the mailing list.
For #1:
- The described problem is real for some large scale and mission critical
networks
- The problem and solution are not only applicable to the above mentioned
example network, but also general to any broadcast network that have different
costs between different pair of routers. As long as the router-to-router costs
can be presented as a to-network and a from-network part, then the simple
solution applies
- The two-part-metric concept is a natural extension of the SPF graph theory -
we're just changing the previously zero from-network cost to none-zero.
For #2, there are pros and cons with each approach.
- The stub-link based approach does not depend on the in-progress LSA
Extensibility work. This has larger impact on implementation - the feature can
be supported w/o big changes to support extended LSA format.
though the stub-link approach is simpler to implement, it's a bit of a
"hack", as you are using a standard encoding for a stub link to
advertise a metric for a neighbor on a broadcast link.
- The LSA Extensibility work is only applicable for OSPFv3. That means OSPFv2
would need a different approach for the problem. Acee also mentioned that it
would be good to have consistent approaches between OSPFv2 and OSPFv3.
what I proposed is consistent - uses new extended LSAs in both OSPFv2
and OSPFv3.
thanks,
Peter
- As a result at this time we would prefer the stub-link approach.
The authors would like to hear more of your opinions/suggestions. Hopefully we can
reach consensus on the applicability of the problem & solution so that it can
become a WG item, and choose the best encoding approach.
Thanks!
Jeffrey
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