: The holdtime isn't technically negotiated, both sides convey their
: value in the open message and the lower of the two is used by both
: BGP speakers.
This isn't a negotiation?
: IIRC, neither J or C reset the session with the timer change, but the
: new holdtimer expiry value doesn't take effect until then.
We use Alcatel 7750s. Damn thing just resets the session; no warning, no nothing. 
: One other thing to note is that by default, keepalive intervals in
: those implementations are {holdtime/3}. Normally, if you're setting
: holdtime to something really lower (e.g., 10 seconds) you might want
: to increase the frequency of keepalives such that the probability of
: getting one through in times of instability rise. In particular,
: congestion incurred outside of BGP, as update messages themselves
: will serve as implicit keepalives, and with the amount of churn in BGP,
: empty updates (keepalives) are rare for most speakers with a global BGP
: view.
I have been looking for info on the negative impact on a router by increasing the keepalive frequency to a high rate. I'm sure it's minimal for a few BGP peers, but I could imagine with a lot of peers it's a non-zero impact.
scott
--- danny@tcb.net wrote: From: Danny McPherson <danny@tcb.net> On May
12, 2010, at 9:40 AM, Jay Nakamura wrote:
I just tested this and, yes, with Cisco to Cisco, changing the
setting won't reset the connection but you have to reset the
connection to have the value take effect. I need to look up what
happens when two sides are set to different values and which one
takes precedent.
: The holdtime isn't technically negotiated, both sides convey their
: value in the open message and the lower of the two is used by both
: BGP speakers.
This isn't a negotiation?
: IIRC, neither J or C reset the session with the timer change, but
the : new holdtimer expiry value doesn't take effect until then.
We use Alcatel 7750s. Damn thing just resets the session; no
warning, no nothing.
: One other thing to note is that by default, keepalive intervals in
: those implementations are {holdtime/3}. Normally, if you're
setting : holdtime to something really lower (e.g., 10 seconds) you
might want : to increase the frequency of keepalives such that the
probability of : getting one through in times of instability rise.
In particular, : congestion incurred outside of BGP, as update
messages themselves : will serve as implicit keepalives, and with the
amount of churn in BGP, : empty updates (keepalives) are rare for
most speakers with a global BGP : view.
I have been looking for info on the negative impact on a router by
increasing the keepalive frequency to a high rate. I'm sure it's
minimal for a few BGP peers, but I could imagine with a lot of peers
it's a non-zero impact.
with a keep alive interval of 10 seconds you can expect to get 10pps
from a 100 peers. the keepalive message is 19bytes
That doesn't seem particularly hurtful even by the standards of 5 year
old control plane processors.