Filter-based routing table management (was: Re: minimum IPv6 announcement size)

William Herrin bill at
Thu Sep 26 17:26:48 UTC 2013

On Thu, Sep 26, 2013 at 11:07 AM, John Curran <jcurran at> wrote:
> On Sep 26, 2013, at 4:52 AM, bmanning at wrote:
>> sounds just like folks in 1985, talking about IPv4...
> If there were ever were a need for an market/settlement model, it is with respect
> to routing table slots.
> That's not to say that establishing a framework for externalizing routing costs would
> be easy; it's a complicated and twisted matter, and also fraught with various legal &
> competitive aspects.

Hi John,

That's putting it mildly. Establishing such a framework would be an
immense challenge. Here are some ideas I've heard:

1. The International Clearinghouse

Every BGP participant files with a clearinghouse, specifying:

a. How much they charge to carry 1 route
b. Whether or not they are a leaf node
c. Whether or not they are a transit-free network.

Any network which is not transit free must implement a default route
which leads to a big transit-free network in order to maintain full

The BGP participants then publish the exact routes they intend to
announce to the clearinghouse and for each one select which networks
they'll pay to carry the route. The route must still reach each
network via BGP; payment just means that the network won't filter the
route out.

The clearinghouse then collects payments from everybody and makes
payments to everybody, as well as providing each participant a list of
the routes that are paid for. Sellers are expected to promptly
incorporate new paid routes into their BGP filters.

>From my research a few years ago, a reasonable rate would be around 3
to 4 cents per year per advertised route per BGP-carrying router in
the organization. A couple billion dollars per year if the routing
table maintained its current size.

2. The partial routing scenario

Large service providers put bids in to the RIRs for the right to
announce /8 covering routes for each /8 delegated to the RIR. Each /8
matches exactly one service provider. Smaller BGP system participants
make private arrangements with a small (20 to 30) set of networks
(including their direct ISPs) to carry their advertised routes through
a reasonably redundant number of pathways to (and including) the
winning bidder for the /8 they inhabit. For the sake of performance,
they may also pay additional large networks to shortcut the traffic
towards them rather than let it dump at the /8 advertiser.

For the folks you don't pay via the clearinghouse, many end-user
systems and the majority of transit systems simply don't carry your
route unless yours is among the handful of systems critically
important to their customers. Instead, traffic to your network follows
the /8 advertisement until it reaches a network which carries your
specific route.

With the routing costs suitably reduced, settlement for the remaining
routes becomes moot.

This is usually within a few percent of the routing efficiency that
would have been achieved with total route propagation.

3. The routing overlay

Establish a semi-stateless tunneling system. Each BGP participant sets
up a tunnel ingress node and links a default route to it. Packets for
a destination not found in the routing table follow the default route
to the tunnel ingress.

The tunnel device then looks up an tunnel exit node via a mapping
protocol. Both the map server and the exit node have to be hosted on
IP addresses reachable via the normal routing table.

Having found an exit node, the original packet is encapsulated into a
tunnel packet and sent to the exit node. The exit node is in a part of
the network that carries an explicit route to the destination.

Then, move the definition of threshold size. Except for whitelisted
critical infrastructure, /24 advertisements would no longer carry an
expectation of universal distribution. To maintain connectivity, folks
at the bottom of the chain would need to establish or subscribe to
tunnel exit nodes that have a route back to them.

With the routing costs suitably reduced, settlement for the remaining
routes becomes moot.

The IRTF Routing Research Group studied such protocols a few years ago
and have pretty well fleshed out how to make one work with all the
tangled issues involving path mtu, dead path detection and so on.
Multiple designs sit on a shelf waiting for a promise that the
technology will be purchased if built.

Bill Herrin

William D. Herrin ................ herrin at  bill at
3005 Crane Dr. ...................... Web: <>
Falls Church, VA 22042-3004

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