non-practical keepalive setting?

[Ondrej Zajicek]

On Sun, Mar 23, 2014 at 02:50:02PM +0100, Job Snijders wrote:
> Hi all,
> 
> 
> It seems it is possible to create a situation like this:
> 
>     Hold timer:       46/60
>     Keepalive timer:  56/80
> 
> Note the hold timer versus keepalive timer! This happens when the other
> side (in this case a JunOS box) configures a hold-time of 60 seconds.
> This results in endless session flapping because the BIRD box will not
> send Keepalives in a timely fashion. 
> 
> There is the BIRD configuration:
> 
>     template bgp peers {
>         local as 199036;
>         multihop;
>         hold time 240;
>         startup hold time 240;
>         connect retry time 120;
>         keepalive time 80;

	  ^^^^^^^^^^^^^^^^^

> While it is not strong RFC vocabulary, it is my interpretation that it
> would be more robust if the Keepalive Timer defaults to Hold Timer
> divided by three, when the Hold Timer is smaller than 3 times the
> configured Keepalive Timer.
> 
> Is this expected behaviour or a bug? 

It is expected behavior - if you explicitly specify keepalive time,
then you override the default (which is 1/3 of agreed hold time)
even if the specified value is nonsensical w.r.t. agreed hold time.

-- 
Elen sila lumenn' omentielvo

Ondrej 'SanTiago' Zajicek (email: santiago at crfreenet.org)
OpenPGP encrypted e-mails preferred (KeyID 0x11DEADC3, wwwkeys.pgp.net)
"To err is human -- to blame it on a computer is even more so."
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