Re: [dns-privacy] [DNSOP] FW: New Version Notification for draft-pan-dnsop-edns-isp-location-00

[Paul Vixie <[e-mail]>]

Lanlan Pan wrote:
> ... Because ECS is also based on the map of
> "*client subnet -> geolocation*" information.

Paul Vixie <[e-mail]>于2017年3月22日周
> wait, what?

Lanlan Pan wrote:
> Hi Paul,

hi.

> https://www.cdnplanet.com/blog/which-cdns-support-edns-client-subnet/

this web page is factually incorrect in that it presupposes that geo-ip
is used. i have added a comment there to this effect.

the original ECS web site
(http://www.afasterinternet.com/howitworks.htm) is somewhat
marketing-oriented, but says only that "With this more intelligent
routing, customers will have a better Internet experience with lower
latency and faster speeds." in other words, it expects that a CDN will
apply its server-selection logic on an address basis, but using the
truncated client subnet rather than to the DNS request source address.
it does not dictate what the CDN's server-selection logic has to be or do.

in RFC 7871 (http://www.afasterinternet.com/ietfrfc.htm) we see this
definition:

> Topologically Close:  Refers to two hosts being close in terms of the
>       number of hops or the time it takes for a packet to travel from
>       one host to the other.  The concept of topological distance is
>       only loosely related to the concept of geographical distance: two
>       geographically close hosts can still be very distant from a
>       topological perspective, and two geographically distant hosts can
>       be quite close on the network.

there is an error on page 22 which is directly on-point:

>    o  Recursive Resolvers implementing ECS should only enable it in
>       deployments where it is expected to bring clear advantages to the
>       end users, such as when expecting clients from a variety of
>       networks or from a wide geographical area.  Due to the high cache
>       pressure introduced by ECS, the feature SHOULD be disabled in all
>       default configurations.

from context, it's clear that they meant "topological area".

actual CDN technology, from as far back as Cisco Distributed Director in
the mid-1990's, has usually ignored geography, for the reasons i gave
up-thread: overlapping and incoherent topology within a geo-ip region
means that geo-location is a very poor predictor of per-path performance.

let me state (again) for the record that i was and remain opposed to ECS
because it's an obviously bad idea and the apparent need for it merely
proves that Stupid DNS Tricks
(http://queue.acm.org/detail.cfm?id=1647302) did not and could not solve
their chosen problem in the first place. it's architectural
cost-shifting, which is a form of both intellectual conversion and
economic compulsion. sad!

however, if you're going to propose a replacement for ECS, you should
correctly describe how it works. <<Because ECS is also based on the map
of "*client subnet -> geolocation*">> is not a correct description. if
EIL is geo-based, then it is completely different from ECS.

-- 
P Vixie