Re: [sidr] Burstiness of BGP updates (was: WGLC: draft-ietf-sidr-bgpsec-reqs)

["George, Wes" <[e-mail]>]

> From: Jakob Heitz [mailto:[e-mail]]
> Sent: Monday, November 14, 2011 8:47 PM
> To: George, Wes; Randy Bush
> Cc: Sriram, Kotikalapudi; sidr wg list
> Subject: RE: [sidr] Burstiness of BGP updates (was: WGLC: draft-ietf-
> sidr-bgpsec-reqs)
>
> I can not believe that it will be 2X.

[WEG] the objective amount of impact is probably not the important bit here.

>
> First case: A beacon will very rarely cause a different bestpath.
[WEG] True. However... your comment was not specific to beacons. Also when it does, it makes the load problem you're trying to solve worse.
>
> Second case: There is actually a changed route being updated.
> You will receive both a regular update and a signature.
> Only one of those will casue a new bestpath in the great majority of
> cases.
>
> Basically, in the large majority of cases, a signature does not change
> the bestpath.
>
[WEG] Not true. Bestpath in BGPSec land is chosen based on policy informed by the difference between valid, invalid and unknown. Even if the absence or presence of the signature only toggles the route between valid and unknown, given that those have a defined policy action (eg raise or lower local pref, etc), the only way to ensure that receiving a signature later than the initial route update does not trigger a change of best path (let alone a recompute that doesn't trigger a change, which probably has nearly the same impact) is to set ones policy such that unknown and valid are the same preference. While that may be reasonable in early incremental deployment, eventually I don't think that's a safe assumption, and really eventually is when we have a scaling problem, not in early deployment.

Wes George

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