Subject: Extended Hitless OSPF Restart

From: Acee Lindem <[email-masked]>
Date: Tue, 25 Jun 2002 19:51:32 -0700

FYI - Ultimately, this would be an informational RFC or better yet
folded into the base "OSPF Hitless Restart" specification (although
this has not been discussed as of yet).

Thanks,
Acee

Date: Tue, 25 Jun 2002 07:01:53 -0400
From: [email-masked]
To: IETF-Announce:  ;
Subject: I-D ACTION:draft-lindem-ospf-hitless-extended-restart-00.txt

A New Internet-Draft is available from the on-line Internet-Drafts
directories.

        Title           : Extended Hitless OSPF Restart
        Author(s)       : A. Lindem, A. Oswal
        Filename        :
draft-lindem-ospf-hitless-extended-restart-00.txt
        Pages           : 3
        Date            : 24-Jun-02

This memo documents an enhancement to OSPF 'hitless restart' whereby
an OSPF router can request that its forwarding state be maintained
longer that the router dead interval on one or more router
interfaces.  This is useful when the OSPF software is being
updated and the router dead interval on one or more interfaces is
configured to a small value.

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---

From: Daniel Gryniewicz <[email-masked]>
Date: Wed, 26 Jun 2002 15:36:36 -0400

Hi.

Could someone please explain to me why this is necessary?  My reading of
draft-ietf-ospf-hitless-restart-02 indicates that an implementation should
*not* exit helper status because a router dead interval expired.  Please
enlighten me.

Daniel

On Tue, 25 Jun 2002 19:51:32 -0700

> draft-lindem-ospf-hitless-extended-restart-00.txt
<snip>

---

From: Erblichs <[email-masked]>
Date: Wed, 26 Jun 2002 13:31:24 -0700

Group,

        This really goes back to the original doc..

        Shouldn't there be a limit of say 1 hour for the grace period.

        After that time, work that the proposed router's/helpers
        should almost ignore that the hitless restart functionality
        was originally requested and age out the LSAs that were
        originated by the by the restarting router.

        Mitchell Erblich
        =======================

---

From: Erblichs <[email-masked]>
Date: Wed, 26 Jun 2002 13:34:13 -0700

Sorry group,

        For this document...

        For the restarting router.. If it was the DR or BDR, do
        we keep him as the old DR/BDR or re-elect after router
        dead interval?

        Mitchell Erblich
        ==================

---

From: Daniel Gryniewicz <[email-masked]>
Date: Wed, 26 Jun 2002 16:24:09 -0400

Well, the draft allows local policy to specify not entering helper mode if,
for example, the requested grace period exceeds time T.

Daniel

On Wed, 26 Jun 2002 13:31:24 -0700

---

From: Acee Lindem <[email-masked]>
Date: Wed, 26 Jun 2002 14:14:27 -0700

> *not* exit helper status because a router dead interval expired.  Please

This not what I've implemented. A router acting as a helper will exit
helper mode when:

    1. The inactivity timer expires.
    2. The interface goes down (which will also cause an LSA change). However,
       I've made it a configurable option whether or not a given router acting
       as a helper exits graceful restart when there is a change to an LSA which
       will be flooded to the restarting router.
    3. Certain sequence mismatch conditions (but not the obvious ones that occur
       naturally during graceful restart).

I'd be interested in what others have implemented.

Thanks,
Acee

--
Acee

---

From: Daniel Gryniewicz <[email-masked]>
Date: Wed, 26 Jun 2002 17:22:45 -0400

Isn't the whole point of a grace period that you want to exceed a router dead
interval?  If you are not going to exceed it, you can just do an ISIS restart,
which does not need a grace period at all.

Daniel

On Wed, 26 Jun 2002 14:14:27 -0700
Acee Lindem <[email-masked]> wrote:

>     2. The interface goes down (which will also cause an LSA change).
However,>        I've made it a configurable option whether or not a given
router acting>        as a helper exits graceful restart when there is a
change to an LSA which>        will be flooded to the restarting router.
>     3. Certain sequence mismatch conditions (but not the obvious ones that
occur>        naturally during graceful restart).

---

From: Acee Lindem <[email-masked]>
Date: Wed, 26 Jun 2002 15:10:10 -0700

> which does not need a grace period at all.

The main differenence is that without graceful restart, OSPF offers no mechanism
for learning the link state database without transitioning out of full state and
re-originating router/neighbors LSAs, etc.

--
Acee