Subject: Re: [lisp] Mapping system observations

From: [email-masked] (Noel Chiappa)
Date: Thu, 9 Aug 2012 16:26:35 -0400 (EDT)

> From: Damien Saucez <[email-masked]>

    > However, we observe a much more variable delay now with DDT than before
    > where delays were very stable with time.

Is this variation for a single MR<->{something} interaction, or is this the
overall time from i) an ITR needing a mappping to ii) it getting the mapping?
If the latter, it makes sense that there is more variation.

Previously, the Map-Request was sent over the ALT (via the ALT's root, in
almost all cases) to the ETR, and then the reply came back. Not a lot to vary
there (although the path from the root to the Map-Server would vary a bit).

Now, depending on how the delegation tree is configured (i.e. how many layers
from the root to the Map-Server for the mapping in question), how many of
those delegations are cached in the Map-Resolver the ITR is talking to, etc
you would expect to see a certain amount of variation.

	Noel

---

From: Damien Saucez <[email-masked]>
Date: Thu, 9 Aug 2012 22:36:33 +0200

Noel,

> If the latter, it makes sense that there is more variation.

It's the average delay among all the EID retrieved at the given time from the
vantage point.
> you would expect to see a certain amount of variation.

agree, we therefore need to figure out where to place DDT nodes, how much
the (root) nodes must be replicated, and how deep the tree must be to achieve
stable and low delays.

Damien Saucez