Subject: RE: [Isis-wg] Overload Bit

From: "Jeelani Syed" <[email-masked]>
Date: Sun, 10 Oct 2004 23:15:50 -0400

Agreed, I thought the question was why to advertise LSPs(disabling ISIS
on overload state) at all instead of using overload bit. So I was
pointing out one of the advantages using overload bit 
in flooding perspective especially when router has lot of LSP fragments.

-jeelani.sm

-----Original Message-----
From: Henk Smit [mailto:[email-masked]]
Sent: Friday, October 08, 2004 7:01 PM
To: Jeelani Syed
Cc: Abhishek Verma; [email-masked]
Subject: Re: [Isis-wg] Overload Bit

> First of all overload state is assumed to be a temporary state

  Says who ?
 If a router wants to set the overload bit for ever, it is allowed to
 do so. There are cases where a constant setting of the overload bit
 is useful.

> and it is undesirable to purge
> all LSPs beloging to a router from network and reflood them instead of
> just sending a LSP 
> with overload bit set/reset.

  1) Purging an LSP or 2) setting the overload bit
 are two totally different things, and should not be compared with
 each other.

  Also, purging one LSP or setting the overload bit on one LSP 
 requires roughly the same amount of work to be done by all
 routers (both actions require one router to create a new LSP,
 flood it to all routers, all routers do some LSPDB housekeeping,
 all routers run an SPF computation).

  Hope this helps,

        Henk.

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From: Tony Li <[email-masked]>
Date: Sun, 10 Oct 2004 20:42:13 -0700

One situation that came up that was of interest was an ISP that had
their NOC adjacent to their production links.  On the router leading
to the NOC, they set overload.  This prevented transit traffic through
that router even tho it was very well connected.  The NOC still had
connectivity as ES's (connected prefixes) were still reachable.

Tony