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 Blogs and organic groups at http://www.ccie.netReceived on Fri Jan 04 2013 - 02:16:38 ART
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