Re: OSPF LSA type 3 filtering

Haha, no to the best of my knowledge.

NP-complete is a kind of algo complexity.

-Carlos

Marko Milivojevic @ 04/01/2013 07:16 -0300 dixit:
> Btw. I believe the problem I was trying to describe is called NP-Complete, but that's a bit outside of my area of expertise. I'm not a mathematician not a CS.
>
> --
> Marko Milivojevic - CCIE #18427 (SP R&S)
> Senior CCIE Instructor - IPexpert
>
> :: This message was sent from a mobile device. I apologize for errors and brevity. ::
>
> On Jan 4, 2013, at 2:06, Marko Milivojevic <markom_at_ipexpert.com> wrote:
>
>> What is missing is the decisive information on when you can stop computing. Without T2, there is no knowing when you are done :-). What if an area had 5000 routers.
>>
>> You are correct though. You *could* do it without Type 2, but it can lead to dangerous issues.
>>
>> --
>> Marko Milivojevic - CCIE #18427 (SP R&S)
>> Senior CCIE Instructor - IPexpert
>>
>> :: This message was sent from a mobile device. I apologize for errors and brevity. ::
>>
>> On Jan 4, 2013, at 2:02, Carlos G Mendioroz <tron_at_huapi.ba.ar> wrote:
>>
>>> Marko,
>>> say we have an area with 3 routers, R1, R2, R3, connected by a LAN.
>>> Then OSPF would choose one as DR. Say that lan is X.
>>>
>>> Would you agree that the database representation would be:
>>>
>>> Router links:
>>> R1: R1 -> DR (transit)
>>> R2: R2 -> DR (transit)
>>> R3: R3 -> DR (transit)
>>>
>>> Net link:
>>> DR: X (R1,R2,R3)
>>>
>>> You can draw the topology just by looking at the router links.
>>> What is missing ?
>>>
>>> -Carlos
>>>
>>>
>>> Marko Milivojevic @ 04/01/2013 01:11 -0300 dixit:
>>>> Writing on a phone. Pardon the brevity
>>>>
>>>>>
>>>>> I would argue that you can make the topology of an area only with type 1 LSAs, and that type 2 LSAs are just for "condensing" the multiaccess
>>>>> link reachability information in one place.
>>>>
>>>> Not quite. You would know which routers exist in the area, but not how they are interconnected.
>>>>
>>>> To calculate the SPF tree, routers need two pieces of information for all non-leaf links: the link state, and relationship with other routers.
>>>>
>>>> OSPF recognizes three link types in Type 1: stub, transit, and point to point.
>>>>
>>>> For point to point links, link state is carried in two link state entries. Link itself is described as a "stub link", and the relationship with other router is described as a point-to-point link. These are both in Type 1 LSA.
>>>>
>>>> However, for transit link the actual link is described as a link entry in Type 1 LSA, with a reference to a Type 2 LSA (in a form of a DR address). The Type 2 carries the topological information about the relationships between touters in the segment. Both are crucial for the topological calculation.
>>>>
>>>> Note - this was all about the topological information and not the reachability.
>>>>
>>>> -Marko
>>>>
>>>>
>>>> Blogs and organic groups at http://www.ccie.net
>>>>
>>>> _______________________________________________________________________
>>>> Subscription information may be found at:
>>>> http://www.groupstudy.com/list/CCIELab.html
>>>
>>> --
>>> Carlos G Mendioroz <tron_at_huapi.ba.ar> LW7 EQI Argentina

-- 
Carlos G Mendioroz  <tron_at_huapi.ba.ar>  LW7 EQI  Argentina
Blogs and organic groups at http://www.ccie.net