Re: BGP Timers and Slow Convergence 101

So I guess you could configure the neighbors to each have "timers 0
0" and the bgp processes would not notice the peer being unreachable
if the link were to go down.
If the above is true, what would be a reason to set it that way?

-Rich

On Fri, May 20, 2011 at 2:17 PM, garry baker <baker.garry_at_gmail.com> wrote:
> i guess if the workbooks you buy do not cover it you will have to go to the
> RFC, to figure out it is the holdtime value that is negotiated and the
> keepalives are based of this value:
>
> good stuff...
>
> http://tools.ietf.org/html/rfc4271
>
> Hold Time:
>
> This 2-octet unsigned integer indicates the number of seconds
> the sender proposes for the value of the Hold Timer. Upon
> receipt of an OPEN message, a BGP speaker MUST calculate the
> value of the Hold Timer by using the smaller of its configured
> Hold Time and the Hold Time received in the OPEN message. The
> Hold Time MUST be either zero or at least three seconds. An
> implementation MAY reject connections on the basis of the HoldTime.
> The calculated value indicates the maximum number of
> seconds that may elapse between the receipt of successive
> KEEPALIVE and/or UPDATE messages from the sender.
>
> 4.4. KEEPALIVE Message Format
>
> BGP does not use any TCP-based, keep-alive mechanism to determine if
> peers are reachable. Instead, KEEPALIVE messages are exchanged
> between peers often enough not to cause the Hold Timer to expire. A
> reasonable maximum time between KEEPALIVE messages would be one third
> of the Hold Time interval. KEEPALIVE messages MUST NOT be sent more
> frequently than one per second. An implementation MAY adjust the
> rate at which it sends KEEPALIVE messages as a function of the Hold
> Time interval.
>
> If the negotiated Hold Time interval is zero, then periodic KEEPALIVE
> messages MUST NOT be sent.
>
>
> --
> Garry L. Baker
>
> "With sufficient thrust, pigs fly just fine..." - RFC 1925

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Received on Fri May 20 2011 - 18:59:46 ART