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Re: [RRG] Why delaying initial packets matters

Robin,

On Feb 7, 2008, at 7:00 PM, Robin Whittle wrote:

A scheme such as ALT will also delay some of the DNS (identifier to
locator) lookups, since some DNS servers will be on EID space which
the ITR has no mapping for.
Not necessarily. The mapping service (e.g., DNS) servers can exist in locator space. In fact, this makes many things much easier (e.g., avoiding circular dependency). The downside is that the mapping service itself obviously cannot take advantage of the locator/ identifier split. 


I think there at at least two reasons we should be concerned about
the delay problems inherent in a map-encap scheme which depends on
any kind of global query server network (LISP-CONS, LISP-ALT or Bill
Herrin's TRRP):

1 - Great reluctance to introduce or impose any new architecture
   which further delays the establishment of communications.

2 - Concern that if the new kind of address space involves
   extra delays of any measurable kind - especially when they
   are perceptible by end-users - that this will be a serious
   and perhaps fatal barrier to the widespread adoption of the
   new kind of address space.
I believe Brian's point was that extra delays of measurable kind have _not_, even when perceptible by end users, been fatal in the past. People adjust. Software developers adjust. Etc. Why, I remember a day when if I did something on my computer that required Internet connectivity, I'd go get a soda instead of listening to the screech and moan of my modem as it brought up my SLIP line... (and yes, I did walk through hip deep snow to school both ways).
And to be clear, the delays you are concerned with are at communication initiation with a "new" endpoint only. A time when a few hundred more milliseconds of latency would likely be lost in the noise of DNS lookups, connection handshake, crypto handshake, etc. 


It will be difficult to convince end-users to pay money (including
less money) for the slower type of address space.
You are aware that there are still companies around that sell dialup, partly because they're significantly cheaper than DSL and cable, right? 


LISP-NERD, APT and Ivip avoid these delays.


At the cost of scalability and slower update cycles.  TANSTAAFL.


Are there any major arguments for ALT (or CONS or any other global
query server system) other than that it can scale to indefinitely
large database sizes,
A pull system can potentially provide for much higher rates of change than a push system. As I believe has been mentioned in the past, a pull system (if augmented by forwarding) could even be used for mobility. 


while any architecture involving local query
servers (supposedly) could not handle such a large database?
In my mind, the question isn't so much about the size of the database (DRAM is cheap, disk is cheaper), but rather propagating updates. It seems to me that pull systems are merely replicating some of the problems we face in the existing routing system since all updates must be propagated globally, regardless of whether they are of any interest to the source network, on the (given potential scaling targets essentially, statistically speaking, insignificant) chance that the source edge network _might_ want the update. 


Later, I will post an argument about why it is, and always will be,
practical and desirable to push even the largest imaginable mapping
database to a system of local query servers and/or ITRs.


I'll be quite interested in reading it.

Regards,
-drc


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