Subject: Re: draft-vasseur-mpls-ospf-pcsd-discovery-00.txt

From: "Naidu, Venkata" <[email-masked]>
Date: Thu, 8 Aug 2002 14:54:45 -0400

Vishwas,

-> We have done this for a lot of other purposes and
-> I feel it is valid.

  I am not saying that your ASBR suggestion is invalid :)
  Please read on...

  May I know for what other purposes we used ASBR option ?

-> >  The current OSPF-TE draft also does the same for Router
-> >  Address (which is required to be routable always and
-> >  very different from OSPF Router ID)
-> >
-> >   The Router Address TLV specifies a stable IP address of the
-> >   advertising router that is always reachable if there is any
-> >   connectivity to it.
->
-> When a link goes down the adjacent router will not advertize
-> the link and
-> hence the link and the router reachable thru the link will
-> not be used for
-> TE purposes either. We do not do a best effort in TE, where
-> we actually try
-> and only in case of failure realize a router/link could be down.

  Vishwas, here I am talking about Router Address TLV and not
  Link TLV. Consider all the links are up, but the advertised
  Router Address can still be unreachable.

  OSPF-TE draft didn't say that "Make sure that router
  advertises Router Address in their Router LSAs as stub links"
  etc etc.

-> I guess some implementations do use the router LSA to figure
-> out if the
-> router is actually reachable. The router LSA is updated when
-> the link goes
-> down, and when that happens we canot reach the router and we
-> do not use the TE information of that router either.

  You are talking about proprietary implementations here :)
  You know that I am NOT a full supporter of such designs.
  You are assuming that all *TE links* are *reachable* &
  *routable* links.

-> Well if the router is an ASBR, other area routers know of
-> the router because type-4 LSA's for the router. If a router
-> route for the router exists the router is reachable when
-> it is not, it is not.

  You didn't get my actual point. My point is,
  don't mandate that "PCS server must be an ASBR".

  You can mention in the draft:

  "If the administrator would like to know the reachability
   of PCS server dynamically then he can do one of the
   following possible options (this list is by no way
   comprehensive):
    1. If the PCS server is an internal router then
       advertise PCS server as an ABSR. But care must be
       taken in case of stub/NSSA areas.
    2. make an ABR act as PCS server
    3. make another PCS server as backup and make sure that
       backup is reachable when primary goes down"

  If an administrator would like to know the changes to
  PCS status then he can always turn on ASBR option
  on that router. If he doesn't want, (for example
  he added static routes along the path to PCS) then
  let PCS connections fail...let clients re-try.

--
Venkata.