Re: BGP Timers and Slow Convergence 101

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
On Fri, May 20, 2011 at 1:28 AM, Darby Weaver <darby.weaver_at_gmail.com>wrote:
> Umm...
>
> BGP Timers - Love em, Hate em, and then... Get over it and just Change Em!
>
> You can change the BGP Timers on either side of the peer link.
> The BGP Timers will be agreed up during the negotiating process and then
> the
> peer with the lowest timer configuration will be used at the timer values
> for the BGP peer link.
>
> Kewl?
>
> Easy as pie!
>
> Doesn't anyone's workbook besides mine cover this kind of thing?
>
> :)
>
> Darby
>
>
> --
> Darby Weaver
> Network Engineer
> http://www.darbyslogs.blogspot.com
>
> darbyweaver_at_yahoo.com
>
>
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