RE: [RRG] Which Side to Control Ingress Link Selection?

[Randall Atkinson <rja@extremenetworks.com>]

I doubt that any one party can (or should) control the inter-domain path
that a packet takes from some source site to some destination site
through some non-trivial series of ASs.

What makes more sense, to me at least, is that the party forwarding
the packet at a given moment makes its forwarding decision based
on its local policy and the information available to it (RIB, FIB, packet
header, and whatever else).  That said, clearly it is reasonable for a
destination to indicate a preferred ingress path (or a set of preferences
for ingress) to the source.  The source node then takes that information
and applies its own local policy when creating and forwarding the packet
initially.  Routers along the path might usually be in several different domains,
each with slightly different sets of reachabilities and policies.  Provided
the packet arrives, and we have some means of minimising issues
with routing loops, that is sufficient.

After all, the Internet is an unreliable datagram service.  It is NOT
a circuit and we ought not be trying to transform it into a circuit
network.  Circuit network technologies exist and folks are free to
use those if they wish, but that is not the goal of the Internet.

Yours,

Ran


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