A carrier grade L2BSA gateway with netgraph by Lutz Donnerhacke
In Germany, broadband access is still based on copper to the house due to
historical, political reasons. In order to increase transfer rates vectoring
became ubiquitous. That’s why all wires between houses and a curb need to be
operated by a single company. Unfortunately, Germany does not distinguish
between layer2 operators and layer3 operators. So either all households have
to buy Internet from a monopolist or a layer2 transmission to a third party
ISP must be regulated. The regulated access to the layer2 bitstream of a
customer is defined by the regulation authority and implemented as a so-
called A10NSP gateway. In principle at this point all layer2 traffic is
encapsulated by an additional VLAN tag for each customer line. The VLAN tag
itself is defined to be fixed as long as the DSL is in sync, but will change
randomly on resync. Existing A10NSP solutions are expensive, closed
appliances which provide only a single type of access: PPPoE. We offer
triple play via DHCP on multiple VLANs to our customers, and we did not want
to pay others for a (limited) solution. So the idea arose to implement this
A10NSP gateway ourselves using FreeBSD and netgraph. At this time several
thousand customers are connected using this cheap and scalable solution.
Let’s have a look into the implementation.
Lutz Donnerhacke
Lutz Donnerhacke studied physics and mathematics. During this time he was
part of the Internet build-up (Individual Network) in Germany and
administrator of the USENET de-hierarchy. Interest focused on cryptography
(OpenPGP, X.509, DNSSEC), programming (Ada, Haskell, Piet, C, Perl, PHP),
and Internet governance (Fitug, ICANN). He is working for a regional ISP for
more than 20 years and currently active in building central infrastructure
for a larger ISP.