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Re: [RRG] Are host-stack modifications allowed or disallowed ?

On 2/24/08 1:24 PM, Brian E Carpenter allegedly wrote:

I'm thinking that there may be a class of solutions which will
work as far as aggregation and scaling are concerned without
any host modifications, but would allow host modifications to
have substantial impact on traffic engineering for the benefit
of sites hosting major server farms. This type of site cares
about traffic engineering to improve its own performance and
reliability, quite independently of ISP concerns about traffic
engineering. I could imagine a server farm dynamically adjusting
its loc-id mapping as the work load shifts around between
phsyical servers, or as it observes performance changes
from one ISP or another. I would expect this would need tight
interaction between host virtualisation software and the
routing system.


So ...

  - a host or server farm can change its loc-id mapping and control
    which site interfaces it receives traffic on.  This can be
    per-flow.

  - on a broader level, a site interconnect point can control how
    traffic to an including prefix enters the site.
Since loc-id mappings for whole prefixes will be cached all over the Internet, the only way for the host (or server farm) to control this dynamically would be to use an ID from a different prefix. Would that do what you want? Or do you want to be able to say "Dear edge, I know your policy for traffic to prefix X is to bring it in through these two points, but I would like it all brought into just this one point"? If so, what's the protocol?
Also, what do you do about interactions between host requests and possible traffic oscillations? The edge would have to take all requests into account and come up with its own synthesis, filtered through overall network policy anyway?
It seems to me that anything the server/host could influence at the level of loc-id mapping would probably already be taken into account in the interconnect's behavior, including whether to have any dynamic behavior at all. For its own purposes, the host can use different addresses as needed (and we've been there before). 


However, the fact that sites use DNS and BGP4 to attract
traffic to particular prefixes today strongly suggests that
they will use any deployed loc-id mapping system the same
way.


Sure.  That's site level policy.

I wish I could say we should talk about it in person.

Scott


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