Re: [Ila] [5gangip] Scaling mapping systems (was Re: BOF Description)

[Tom Herbert <[e-mail]>]

On Wed, Feb 7, 2018 at 6:16 AM, Dino Farinacci <[e-mail]> wrote:

> > In ILAMP (https://tools.ietf.org/html/draft-herbert-ila-ilamp-00)
> secure redirects are defined to be the primary means of populating a cache.
> On a cache miss, a packet is forwarded into the network and routing should
> forward the packet to an ILA router that contains the complete set of
> mappings for the
>
> In LISP, we have PITRs that do roughly the same thing. But it comes at an
> expense that EIDs need to be advertised into the core routing system. I
> guess in your case, it is on the SIR-prefix that is injected and a packet
> destined for any ID with a SIR-prefix goes to the closest ILA router. Is
> that right?
>
> Yes. The packet is routed to an ILA router based on a prefix that contains
the shard index.


> > associated shard. The router performs the transformation and can send a
> redirect back to the caching node. The redirect can be cached so that
> subsequent packets take a direct route and avoid the
>
> But you will get some out of order packets. Until the cache is populated,
> packets are still in the network, either packets that have not reached the
> ILA router, or packets that have been transformed. So if the ILA router
> near the source, or the source itself, sends directly, there is a chance it
> is a shorter path. So new packets arrive to the destination before packets
> in flight.
>

Yes. OOO packets are possible during a transition period. In order delivery
is not a requirement of IP and the window for OOO packets is relatively
small anyway.


> > trianglular routing. Redirects must be secure so that they cannot be
> spoofed, so for that reason (and some others) the protocol is over TCP. The
> mapping cache is only an optimization and packets are never dropped or
> queued for pending cache resolution. If the cache weren't present,
> communications would
>
> But the ILA router in the network needs to have the mapping. And if it
> does not, what happens then?
>
> The ILA router is considered authoritative for its shard. If it doesn't
have a mapping then the packet is silently dropped as having an unreachable
destination.


> > still be viable but sub-optimal; that characteristic establishes a bound
> for the worst case DOS attack.
> >
> > Any thoughs on this approach?
>
> You’ll really need to put signatures in the Redirect messages if you want
> robust authentication.
>

The redirects are sent over an established TCP connection to an ILA-N so
that deters message spoofing. For stronger security, TCP authentication
option or TLS can be used.

Tom