Re: Clarification in size of Rtr and network LSA

[Don Goodspeed <[e-mail]>]

Hmmm.  Would a scheme like ISIS has for extended LSPs
work for the router LSA?  If we could use a range of
router IDs that are not assigned, then maybe.  Or we
could use a non-backward compatible method using opaque
LSAs.  Any ideas?  -don

================================
Krishna,

I myself don't like fragmentation, if just due to the fact
that any fragment gets dropped, then the whole packet/frame
needs to be rexmit'ed.

Additionally, I would expect at least consistency counts for
each LSA type. This count should be retrieveable before
you start filling the LSA. With this count you can allocate
the proper memory size.

Mitchell Erblich
Sr Software Engineer
-------------

Krishna Rao wrote:
>
> Hi,
> This is w.r.to the size of the Router LSA to be generated. We can not predict the size of the router LSA initially in the process of forming the Router LSA. Usually we allocate (Max MTU size - (OSPF header size + IP header size + MD5 authentication size) --> 1500 - (28 + 20 + 16)= 1436) and start filling the LSA. For Point to point interface we add two links and need 24 bytes for each point to point interface. That results in supporting only 59 interfaces in a single area. Is this an acceptable argument? or Should we design such that OSPF sends a LSA more than MTU size and gets fragmented in IP.
> What is the scalabilty figure for Number of interfaces in a area for popular routers?
>
> Thanks in advance,
> Regards,
> Krishna

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